“Differentiation therapy” provides a unique and potentially effective, less toxic treatment paradigm for cancer. Moreover, combining “differentiation therapy” with molecular approaches presents an unparalleled opportunity to identify and clone genes mediating cancer growth control, differentiation, senescence, and programmed cell death (apoptosis). Subtraction hybridization applied to human melanoma cells induced to terminally differentiate by treatment with fibroblast interferon (IFN-β) plus mezerein (MEZ) permitted cloning of melanoma differentiation associated (mda) genes. Founded on its novel properties, one particular mda gene, mda-7, now classified as a member of the interleukin (IL)-10 gene family (IL-24) because of conserved structure, chromosomal location, and cytokine-like properties has become the focus of attention of multiple laboratories. When administered by transfection or adenovirus-transduction into a spectrum of tumor cell types, melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) induces apoptosis, whereas no toxicity is apparent in normal cells. mda-7/IL-24 displays potent “bystander antitumor” activity and also has the capacity to enhance radiation lethality, to induce immune-regulatory activities, and to inhibit tumor angiogenesis. Based on these remarkable attributes and effective antitumor therapy in animal models, this cytokine has taken the important step of entering the clinic. In a Phase I clinical trial, intratumoral injections of adenovirus-administered mda-7/IL-24 (Ad.mda-7) was safe, elicited tumor-regulatory and immune-activating processes, and provided clinically significant activity. This review highlights our current understanding of the diverse activities and properties of this novel cytokine, with potential to become a prominent gene therapy for cancer.
mda-7/IL-24; Differentiation therapy of cancer; Programmed cell death; Antitumor bystander activity; Radiosensitization; Angiogenesis; Cell signaling; Phase I clinical trial
A potentially less toxic approach for cancer therapy comprises induction of tumor cells to lose growth potential irreversibly and terminally differentiate. Combining this scheme termed ‘differentiation therapy of cancer’ with subtraction hybridization to human melanoma cells resulted in the cloning of melanoma differentiation associated (mda) genes displaying elevated expression as a consequence of induction of terminal differentiation. One originally novel gene, mda-7, was found to display elevated expression in normal melanocytes and nevi with progressive loss of expression as a consequence of melanoma development and progression to metastasis. Based on structure, biochemical properties and chromosomal location, mda-7 has now been reclassified as interleukin (IL)-24 a member of the expanding IL-10 family of cytokines. In vitro cell culture and in vivo animal studies indicate that mda-7/IL-24 selectively induces programmed cell death (apoptosis) in multiple human cancers (including melanomas), without harming normal cells, and promotes profound anti-tumor activity in nude mice containing human tumor xenografts. Based on these remarkable properties, a Phase I Clinical trial was conducted to test the safety of administration of mda-7/IL-24 by a replication incompetent adenovirus (Ad.mda-7; INGN 241) in patients with advanced solid cancers including melanoma. mda-7/IL-24 was found to be safe and to promote significant clinical activity, particularly in the context of patients with metastatic melanoma. These results provide an impetus for further clinical studies, and document a central paradigm of cancer therapy, namely translation of basic science from the “bench to the bedside.”
mda-7/IL-24; apoptosis; metastatic melanoma; Phase I Clinical Trial
Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24), a cytokine belonging to the IL-10 family, selectively induces apoptosis in cancer cells without harming normal cells by promoting an endoplasmic reticulum (ER) stress response. The precise molecular mechanism by which the ER stress response culminates in cell death requires further clarification. The present study shows that in prostate carcinoma cells, the mda-7/IL-24-induced ER stress response causes apoptosis by translational inhibition of the antiapoptotic protein myeloid cell leukemia-1 (Mcl-1). Forced expression of Mcl-1 blocked mda-7/IL-24 lethality, whereas RNA interference or gene knockout of Mcl-1 markedly sensitized transformed cells to mda-7/IL-24. Mcl-1 downregulation by mda-7/IL-24 relieved its association with the proapoptotic protein Bak, causing oligomerization of Bak and leading to cell death. These observations show the profound role of the Bcl-2 protein family member Mcl-1 in regulating cancer-specific apoptosis induced by this cytokine. Thus, our studies provide further insights into the molecular mechanism of ER stress-induced cancer-selective apoptosis by mda-7/IL-24. As Mcl-1 is overexpressed in the majority of prostate cancers, mda-7/IL-24 might provide an effective therapeutic for this disease.
Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24), a unique member of the IL-10 gene family, displays a broad range of antitumor properties including cancer-specific induction of apoptosis, inhibition of tumor angiogenesis, and modulation of anti-tumor immune responses. Here we identify clusterin (CLU) as a MDA-7/IL-24 interacting protein in DU-145 cells and investigate the role of MDA-7/IL-24 in regulating CLU expression and mediating the antitumor properties of mda-7/IL-24 in prostate cancer. Ad.mda-7 decreased expression of soluble CLU (sCLU) and increased expression of nuclear CLU (nCLU). In the initial phase of Ad.mda-7 infection sCLU expression increased and CLU interacted with MDA-7/IL-24 producing a cytoprotective effect. Infection of stable clones of DU-145 prostate cancer cells expressing sCLU with Ad.mda-7 resulted in generation of nCLU that correlated with decreased cell viability and increased apoptosis. In the presence of mda-7/IL-24, sCLU-DU-145 cells displayed G2/M phase arrest followed by apoptosis. Similarly, Ad.mda-7 infection decreased cell migration by altering cytoskeleton in sCLU-DU-145 cells. Ad.mda-7-treated sCLU-DU-145 cells displayed a significant reduction in tumor growth in mouse xenograft models and reduced angiogenesis when compared to the vector control group. Tumor tissue lysates demonstrated enhanced nCLU generated from sCLU with increased apoptosis in the presence of MDA-7/IL-24. Our findings reveal novel aspects relative to the role of sCLU/nCLU in regulating the anticancer properties of MDA-7/IL-24 that may be exploited for developing enhanced therapies for prostate cancer.
MDA-7/IL-24; soluble clusterin; nuclear clusterin; G2/M arrest; apoptosis
mda-7/IL-24 is a unique member of the IL-10 gene family, which displays a broad range of antitumor properties including induction of cancer-specific apoptosis. Adenoviral mediated delivery by Ad.mda-7 invokes an endoplasmic reticulum stress response that is associated with ceramide production and autophagy in some cancer cells. Here we report that Ad.mda-7-induced ER stress and ceramide production triggers autophagy in human prostate cancer cells, but not normal prostate epithelial cells, through a canonical signaling pathway that involves Beclin-1, atg5 and hVps34. Autophagy occurs in cancer cells at early times after Ad.mda-7 infection but a switch to apoptosis occurs by 48 hr post-infection. Inhibiting autophagy with 3-methyladenosine increases Ad.mda-7-induced apoptosis, suggesting that autophagy may be initiated first as a cytoprotective mechanism. Inhibiting apoptosis by overexpression of anti-apoptotic proteins Bcl-2 or Bcl-xL increased autophagy after Ad.mda-7 infection. During the apoptotic phase, the MDA-7/IL-24 protein physically interacted with Beclin-1 in a manner that could inhibit Beclin-1 function culminating in apoptosis. Conversely, Ad.mda-7 infection elicited calpain-mediated cleavage of the autophagic protein ATG5 in a manner that could facilitate switch to apoptosis. Our findings reveal novel aspects of the interplay between autophagy and apoptosis in prostate cancer cells that underlie the cytotoxic action of mda-7/IL-24, possibly providing new insights in the development of combinatorial therapies for prostate cancer.
mda-7/IL-24; protective autophagy; apoptosis; Beclin-1; atg5
The cytokine melanoma differentiation associated gene 7 (mda-7) was identified by subtractive hybridization as a protein whose expression increased during the induction of terminal differentiation, and that was either not expressed or was present at low levels in tumor cells compared to non-transformed cells. Based on conserved structure, chromosomal location and cytokine-like properties, MDA-7, was classified as a member of the interleukin (IL)-10 gene family and designated as MDA-7/IL-24. Multiple studies have demonstrated that expression of MDA-7/IL-24 in a wide variety of tumor cell types, but not in corresponding equivalent non-transformed cells, causes their growth arrest and rapid cell death. In addition, MDA-7/IL-24 has been noted to radiosensitize tumor cells which in part is due to the generation of reactive oxygen species (ROS) and ceramide that cause endoplasmic reticulum stress and suppress protein translation. Phase I clinical trial data has shown that a recombinant adenovirus expressing MDA-7/IL-24 (Ad.mda-7 (INGN-241)) was safe and had measurable tumoricidal effects in over 40% of patients, strongly arguing that MDA-7/IL-24 could have significant therapeutic value. This review describes what is presently known about the impact of MDA-7/IL-24 on tumor cell biology and its potential therapeutic applications.
MDA-7; IL-24; Apoptosis; Autophagy; Ceramide; ROS; Ca2+; Clinical trial; Signal transduction; PERK; ER stress; MCL-1
The present studies focused on determining whether the autophagy-inducing drug OSU-03012 (AR-12) could enhance the toxicity of recombinant adenoviral delivery of melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) in glioblastoma multiforme (GBM) cells. The toxicity of a recombinant adenovirus to express MDA-7/IL-24 (Ad.mda-7) was enhanced by OSU-03012 in a diverse panel of primary human GBM cells. The enhanced toxicity correlated with reduced ERK1/2 phosphorylation and expression of MCL-1 and BCL-XL, and was blocked by molecular activation of ERK1/2 and by inhibition of the intrinsic, but not the extrinsic, apoptosis pathway. Both OSU-03012 and expression of MDA-7/IL-24 increased phosphorylation of PKR-like endoplasmic reticulum kinase (PERK) that correlated with increased levels of autophagy and expression of dominant negative PERK blocked autophagy induction and tumor cell death. Knockdown of ATG5 or Beclin1 suppressed OSU-03012 enhanced MDA-7/IL-24-induced autophagy and blocked the lethal interaction between the two agents. Ad.mda-7-infected GBM cells secreted MDA-7/IL-24 into the growth media and this conditioned media induced expression of MDA-7/IL-24 in uninfected GBM cells. OSU-03012 interacted with conditioned media to kill GBM cells and knockdown of MDA-7/IL-24 in these cells suppressed tumor cell killing. Collectively, our data demonstrate that the induction of autophagy and mitochondrial dysfunction by a combinatorial treatment approach represents a potentially viable strategy to kill primary human GBM cells.
ROS; caspase; ER stress; CD95; cell death
Ovarian cancer is the fifth most common cause of cancer-related death in women. Current interventional approaches, including debulking surgery, chemotherapy, and/or radiation have proven minimally effective in preventing the recurrence and/or mortality associated with this malignancy. Subtraction hybridization applied to terminally differentiating human melanoma cells identified melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24), whose unique properties include the ability to selectively induce growth suppression, apoptosis, and radiosensitization in diverse cancer cells, without causing any harmful effects in normal cells. Previously, it has been shown that adenovirus-mediated mda-7/IL-24 therapy (Ad.mda-7) induces apoptosis in ovarian cancer cells, however, the apoptosis induction was relatively low. We now document that apoptosis can be enhanced by treating ovarian cancer cells with ionizing radiation (IR) in combination with Ad.mda-7. Additionally, we demonstrate that mda-7/IL-24 gene delivery, under the control of a minimal promoter region of progression elevated gene-3 (PEG-3), which functions selectively in diverse cancer cells with minimal activity in normal cells, displays a selective radiosensitization effect in ovarian cancer cells. The present studies support the use of IR in combination with mda-7/IL-24 as a means of augmenting the therapeutic benefit of this gene in ovarian cancer, particularly in the context of tumors displaying resistance to radiation therapy.
Melanoma differentiation associated gene-7/interleukin 24 (mda-7/IL-24) is a novel cytokine displaying selective apoptosis-inducing activity in transformed cells without harming normal cells. The studies by further defines the mechanism(s) by which a GST-MDA-7 fusion protein inhibits cell survival of primary human glioma cells in vitro. GST-MDA-7 killed glioma cells with diverse genetic characteristics that were dependent on activation of JNK1-3 with subsequent activation of BAX and the induction of mitochondrial dysfunction. Activation of JNK1-3 was dependent upon protein kinase R-like endoplasmic reticulum kinase (PERK) and GST-MDA-7 lethality was suppressed in PERK-/- cells. GST-MDA-7 caused PERK-dependent vacuolization of LC3-expressing endosomes whose formation was suppressed by incubation with 3-methyladenine, expression of HSP70 or of BiP/GRP78, or by knockdown of ATG5 or Beclin 1 expression, but not by inhibition of the JNK1-3 pathway. Knockdown of ATG5 or Beclin 1 expression or overexpression of HSP70 reduced GST-MDA-7 lethality. Our data demonstrate that GST-MDA-7 induces an ER stress response that, via the induction of autophagy, is causal in the activation of pro-apoptotic pathways that converge on the mitochondrion and ultimately culminate in decreased glioma cell survival.
autophagy; caspase; ER stress; cell death
Previous studies showed that the human melanoma differentiation-associated gene-7 (mda-7), also known as interleukin-24 (IL-24), has potent antitumor activity against human and murine cancer cells. However, the majority of these studies were limited to in vitro testing. In the present study, we investigated the antitumor activity of mda-7/IL-24 against human ovarian cancer cells both in vitro and in vivo.
In vitro, treatment of ovarian cancer cells with an adenoviral vector carrying the mda-7 gene (Ad-mda7) resulted in inhibition of cell proliferation and induction of cell cycle arrest, leading to apoptosis. We did not observe inhibitory activity in Ad-mda7-treated normal cells. In vivo, treatment of subcutaneous tumor xenografts with Ad-mda7 resulted in significant tumor growth inhibition when compared with that in control groups (p < 0.001). Molecular analysis of ovarian tumor tissue lysates treated with Ad-mda7 showed that MDA-7 protein expression was associated with activation of the caspase cascade.
Our results show that treatment of ovarian cancer cells with mda-7/IL-24 results in growth suppression both in vitro and in vivo.
Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) is a novel cytokine displaying selective apoptosis-inducing activity in transformed cells without harming normal cells. The present studies focused on defining the mechanism(s) by which a GST-MDA-7 fusion protein inhibits cell survival of primary human glioma cells in vitro. GST-MDA-7 killed glioma cells with diverse genetic characteristics that correlated with inactivation of ERK1/2 and activation of JNK1-3. Activation of JNK1-3 was dependent on protein kinase R–like endoplasmic reticulum kinase (PERK), and GST-MDA-7 lethality was suppressed in PERK−/− cells. JNK1-3 signaling activated BAX, whereas inhibition of JNK1-3, deletion of BAX, or expression of dominant-negative caspase-9 suppressed lethality. GST-MDA-7 also promoted a PERK-, JNK-, and cathepsin B–dependent cleavage of BID; loss of BID function promoted survival. GST-MDA-7 suppressed BAD and BIM phosphorylation and heat shock protein 70 (HSP70) expression. GST-MDA-7 caused PERK-dependent vacuolization of LC3-expressing endosomes whose formation was suppressed by incubation with 3-methylade-nine, expression of HSP70 or BiP/GRP78, or knockdown of ATG5 or Beclin-1 expression but not by inhibition of the JNK1-3 pathway. Knockdown of ATG5 or Beclin-1 expression or overexpression of HSP70 reduced GST-MDA-7 lethality. Our data show that GST-MDA-7 induces an endoplasmic reticulum stress response that is causal in the activation of multiple proapoptotic pathways, which converge on the mitochondrion and highlight the complexity of signaling pathways altered by mda-7/IL-24 in glioma cells that ultimately culminate in decreased tumor cell survival.
The acquisition of metastasis potential is a critical point for malignant tumors. Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) is a potential tumor suppress gene and frequently down-regulated in malignant tumors. It has been implicated that overexpression of MDA-7 led to proliferation inhibition in many types of human tumor. Invasion is an important process which is potential to promote tumor metastasis. However, the role and potential molecular mechanism of mda-7/IL-24 to inhibit the invasion of human melanoma cancer is not fully clear. In this report, we identified a solid role for mda-7/IL-24 in invasion inhibition of human melanoma cancer LiBr cells, including decreasing of adhesion and invasion in vitro, blocking cell cycle, down-regulating the expression of ICAM-1, MMP-2/9, CDK1, the phosphorylation of ERK and Akt, NF-κB and AP-1 transcription activity. Meanwhile, there was an increased expression of PTEN in mda-7/IL-24 over-expression LiBr cells. Our results demonstrated that mda-7/IL-24 is a potential invasion suppress gene, which inhibits the invasion of LiBr cells by the down-regulation of ICAM-1, MMP-2/9, PTEN, and CDK1 expression. The molecular pathways involved were the MAPK/ERK, PI3K-Akt, NF-κB, and AP-1. These findings suggest that mda-7/IL-24 may be used as a possible therapeutic strategy for human melanoma cancer.
Melanoma; mda-7; Invasion
The novel cytokine melanoma differentiation associated gene-7 (mda-7) was identified by subtractive hybridization in the mid-1990s as a protein whose expression increased during the induction of terminal differentiation, and that was either not expressed or was present at low levels in tumor cells compared to non-transformed cells. Based on conserved structure, chromosomal location and cytokine-like properties, MDA-7, has now been classified as a member of the expanding interleukin (IL)-10 gene family and designated as MDA-7/IL-24. Multiple studies have demonstrated that expression of MDA-7/IL-24 in a wide variety of tumor cell types, but not in corresponding equivalent non-transformed cells, causes their growth arrest and ultimately cell death. In addition, MDA-7/IL-24 has been noted to be a radiosensitizing cytokine, which in part is due to the generation of reactive oxygen species (ROS) and ceramide that cause endoplasmic reticulum stress. Phase I clinical trial data has shown that a recombinant adenovirus expressing MDA-7/IL-24 (Ad.mda-7 (INGN-241)) was safe and had measurable tumoricidal effects in over 40% of patients, which strongly argues that MDA-7/IL-24 may have significant therapeutic value. This review describes what is known about the impact of MDA-7/IL-24 on tumor cell biology and its potential therapeutic applications.
MDA-7: melanoma differentiation associated gene 7
Melanoma differentiation associated gene-7(mda-7) encodes IL-24, a cytokine that can selectively trigger apoptosis in transformed cells. Recombinant mda-7 adenovirus (Ad.mda-7) effectively kills glioma cells, offering a novel gene therapy strategy to address deadly brain tumors. In this study, we defined the proximal mechanisms by which Ad-mda-7 kills glioma cells. Key factors implicated included activation of the endoplasmic reticulum stress kinase protein kinase R–like endoplasmic reticulum kinase (PERK), Ca++ elevation, ceramide generation and reactive oxygen species (ROS) production. PERK inhibition blocked ceramide or dihydroceramide generation, which were critical for Ca++ induction and subsequent ROS formation. Activation of autophagy and cell death relied upon ROS formation, the inhibition of which ablated Ad.mda-7–killing activity. In contrast, inhibiting TRX induced by Ad.MDA-7 enhanced tumor cytotoxicity and improved animal survival in an orthotopic tumor model. Our findings indicate that mda-7/IL-24 induces an endoplasmic reticulum stress response that triggers production of ceramide, Ca2+, and ROS, which in turn promote glioma cell autophagy and cell death.
The glucose analog and glycolytic inhibitor 2-deoxy-D-glucose (2-DG), which is currently under clinical evaluation for targeting cancer cells, not only blocks glycolysis thereby reducing cellular ATP, but also interferes with N-linked glycosylation, which leads to endoplasmic reticulum (ER) stress and an unfolded protein response (UPR). Both bioenergetic challenge and ER stress have been shown to activate autophagy, a bulk cellular degradation process that plays either a pro- or anti-death role. Here, we investigate which pathway 2-DG interferes with that activates autophagy and the role of this process in modulating 2-DG-induced toxicity.
Pancreatic cancer cell line 1420, melanoma cell line MDA-MB-435 and breast cancer cell line SKBR3 were used to investigate the relationship between induction by 2-DG treatment of ER stress/UPR, ATP reduction and activation of autophagy. ER stress/UPR (Grp78 and CHOP) and autophagy (LC3B II) markers were assayed by immunoblotting, while ATP levels were measured using the CellTiter-Glo Luminescent Cell Viability Assay. Autophagy was also measured by immunofluorescence utilizing LC3B antibody. Cell death was detected with a Vi-Cell cell viability analyzer using trypan blue exclusion.
In the three different cancer cell lines described earlier, we find that 2-DG upregulates autophagy, increases ER stress and lowers ATP levels. Addition of exogenous mannose reverses 2-DG-induced autophagy and ER stress but does not recover the lowered levels of ATP. Moreover, under anaerobic conditions where 2-DG severely depletes ATP, autophagy is diminished rather than activated, which correlates with lowered levels of the ER stress marker Grp78. Additionally, when autophagy is blocked by siRNA, cell sensitivity to 2-DG is increased corresponding with upregulation of ER stress-mediated apoptosis. Similar increased toxicity is observed with 3-methyladenine, a known autophagy inhibitor. In contrast, rapamycin which enhances autophagy reduces 2-DG-induced toxicity.
Overall, these results indicate that the major mechanism by which 2-DG stimulates autophagy is through ER stress/UPR and not by lowering ATP levels. Furthermore, autophagy plays a protective role against 2-DG-elicited cell death apparently by relieving ER stress. These data suggest that combining autophagy inhibitors with 2-DG may be useful clinically.
2-Deoxy-D-glucose; Autophagy; ER stress; ATP; Cell death
Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) is a cancer-specific, apoptosis-inducing gene with broad-spectrum antitumor activity, making it an ideal candidate for a novel cancer gene therapy. A systemic and sustained antitumor immune response generated at the time of initial molecular-targeted therapy would provide additional clinical benefits in cancer patients, resulting in improved prevention of tumor recurrence. In this study, we explored the therapeutic efficacy of intratumoral delivery of a nonreplicating adenoviral vectors encoding mda-7/IL-24 (Ad.mda-7) and a secretable form of endoplasmic reticulum resident chaperone grp170 (Ad.sgrp170), a potent immunostimulatory adjuvant and antigen carrier. Intratumoral administration of Ad.mda-7 in combination with Ad.sgrp170 was more effective in controlling growth of TRAMP-C2 prostate tumor as compared to either Ad.mda-7 or Ad.sgrp170 treatment. Generation of systemic antitumor immunity was demonstrated by enhanced protection against subsequent tumor challenge and improved control of distant tumors. The combined treatments enhanced antigen and tumor-specific T-cell response as indicated by increased IFN-γ production and cytolytic activity. Antibody depletion suggests that CD8+ T-cell may be involved in the antitumor effect of the dual molecule-targeted therapies. Therefore, introducing immunostimulatory chaperone grp170 in situ strongly promotes the ‘immunogenic’ cell death when delivered to the mda-7/IL-24 induced apoptotic tumor cells, indicating that an improved anti-cancer efficacy may be achieved by concurrently targeting both tumor and immune compartments. Given multiple undefined antigens present endogenously within prostate cancer, these data provide a rationale for combining sgrp170-based vaccine strategy with mda-7/IL-24-targeted cancer therapy to induce durable systemic immunity.
mda-7/IL-24; cancer gene therapy; stress protein; chaperone; grp170; immunity
The death rate for pancreatic cancer approximates the number of new cases each year and when diagnosed current therapeutic regimens provide little benefit in extending patient survival. These dire statistics necessitate the development of enhanced single or combinatorial therapies to decrease the pathogenesis of this invariably fatal disease. Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) is a potent cancer gene therapeutic because of its broad-spectrum cancer-specific apoptosis-inducing properties as well as its multi-pronged indirect anti-tumor activities. However, pancreatic cancer cells demonstrate inherent resistance to mda-7/IL-24 that is caused by a block of translation of mda-7/IL-24 mRNA in these tumor cells. We now reveal that a dietary agent perillyl alcohol (POH) in combination with Ad.mda-7 efficiently reverses the mda-7/IL-24 ‘protein translational block' by inducing reactive oxygen species thereby resulting in MDA-7/IL-24 protein production, growth suppression and apoptosis. Pharmacological inhibitor and siRNA studies identify xanthine oxidase as a major source of superoxide radical production causing these toxic effects. Since both POH and Ad.mda-7 are being evaluated in clinical trials, combining a dietary agent and a virally delivered therapeutic cytokine provide an innovative approach for potentially treating human pancreatic cancer.
mda-7/IL-24; POH; reactive oxygen species; cancer-selective apoptosis; xanthine oxidase
Melanoma differentiation associated gene-7 (MDA-7), also known as interleukin (IL)-24, is a tumour suppressor gene associated with differentiation, growth and apoptosis. However, the mechanisms underlying its anti-neoplastic activity, tumour-specificity and efficacy across a spectrum of human cancers have yet to be fully elucidated. In this study, the biological impact of MDA-7 on the behavior of breast cancer (BC) cells is evaluated. Furthermore, mRNA expression of MDA-7 is assessed in a cohort of women with BC and correlated with established pathological parameters and clinical outcome.
The human BC cell line MDA MB-231 was used to evaluate the in-vitro impact of recombinant human (rh)-MDA-7 on cell growth and motility, using a growth assay, wounding assay and electric cell impedance sensing (ECIS). Localisation of MDA-7 in mammary tissues was assessed with standard immuno-histochemical methodology. BC tissues (n = 127) and normal tissues (n = 33) underwent RNA extraction and reverse transcription, MDA-7 transcript levels were determined using real-time quantitative PCR. Transcript levels were analyzed against tumour size, grade, oestrogen receptor (ER) status, nodal involvement, TNM stage, Nottingham Prognostic Index (NPI) and clinical outcome over a 10 year follow-up period.
Exposure to rh-MDA-7 significantly reduced wound closure rates for human BC cells in-vitro. The ECIS model demonstrated a significantly reduced motility and migration following rh-MDA-7 treatment (p = 0.024). Exposure to rh-MDA-7 was only found to exert a marginal effect on growth. Immuno-histochemical staining of human breast tissues revealed substantially greater MDA-7 positivity in normal compared to cancer cells. Significantly lower MDA-7 transcript levels were identified in those predicted to have a poorer prognosis by the NPI (p = 0.049) and those with node positive tumours. Significantly lower expression was also noted in tumours from patients who died of BC compared to those who remained disease free (p = 0.035). Low levels of MDA-7 were significantly correlated with a shorter disease free survival (mean = 121.7 vs. 140.4 months, p = 0.0287) on Kaplan-Meier survival analysis.
MDA-7 significantly inhibits the motility and migration of human BC cells in-vitro. MDA-7 expression is substantially reduced in malignant breast tissue and low transcript levels are significantly associated with unfavourable pathological parameters, including nodal positivity; and adverse clinical outcomes including poor prognosis and shorter disease free survival. MDA-7 offers utility as a prognostic marker and potential for future therapeutic strategies.
Tissue factor (TF) is frequently overexpressed in cancer cells and correlated with more aggressive tumor phenotypes and poor prognosis. In addition to promoting coagulation-dependent metastasis and cancer-associated thrombosis, tumor cell-expressed TF mediates direct cell signaling involving the protease activated receptor (PAR) 2. Ixolaris is a tick-derived inhibitor of the TF-FVIIa-Xa coagulation initiation complex which blocks primary tumor growth and angiogenesis in glioblastoma and melanoma models.
Here we address the anti-tumor effects of Ixolaris in TF-VIIa-PAR2 signaling-dependent breast cancer models, a xenograft model of highly aggressive human MDA-MB-231mfp cells and a syngeneic model of PAR2-deficient and replete PyMT mouse mammary carcinoma cells.
Ixolaris potently inhibited the procoagulant activity of human MDA-MB-231mfp or murine PyMT breast cancer cells. Ixolaris blocked signaling by the ternary TF-FVIIa-FXa complex, and, surprisingly, at higher concentrations also the binary TF-FVIIa complex on MDA-MB-231 cells. We show that Ixolaris interacts with certain residues in the human VIIa protease domain that are involved in PAR2 cleavage. In contrast to human VIIa, Ixolaris was a poor inhibitor of murine TF-FVIIa signaling and did not attenuate PAR2-dependent tumor growth in a syngeneic mouse model of breast cancer progression.
These data show that Ixolaris inhibits PAR2 cleavage specifically by human TF signaling complexes and suggest that Ixolaris may block tumor growth of human cell models with ectopic FVIIa expression through inhibition of direct TF-FVIIa-PAR2 signaling as well as its anticoagulant activity.
The HIV protease inhibitor nelfinavir is currently under investigation as a new anti-cancer drug. Several studies have shown that nelfinavir induces cell cycle arrest, endoplasmic reticulum stress, autophagy, and apoptosis in cancer cells. In the present article, the effect of nelfinavir on human breast cancer cells is examined and potential combination treatments are investigated.
The effects of nelfinavir and tamoxifen on the human breast cancer cell lines MCF7, T47 D, MDA-MB-453, and MDA-MB-435 were tested by analysing their influence on cell viability (via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay), apoptosis (annexin binding, poly(ADP-ribose) polymerase cleavage), autophagy (autophagy marker light chain 3B expression), endoplasmic reticulum stress (binding protein and activating transcription factor 3 expression), and the occurrence of oxidative stress (intracellular glutathione level).
Nelfinavir induced apoptosis in all four breast cancer cell lines tested, although the extent of autophagy and endoplasmic reticulum stress varied among the cell lines. The concentration of nelfinavir needed for an efficient induction of apoptosis in breast cancer cells could be reduced from 15 μg/ml to 6 μg/ml when combined with tamoxifen. At a concentration of 6 μg/ml, tamoxifen substantially enhanced the endoplasmic reticulum stress reaction in those cell lines that responded to nelfinavir with binding protein (BiP) upregulation (MCF7, T47D), and enhanced autophagy in cell lines that responded to nelfinavir treatment with autophagy marker light chain 3B upregulation (MDA-MB-453). Although tamoxifen has been described to be able to induce oxidative stress at concentrations similar to those applied in this study (6 μg/ml), we observed that nelfinavir but not tamoxifen reduced the intracellular glutathione level of breast cancer cells within hours of application by up to 32%, suggesting the induction of oxidative stress was an early event and an additional cause of the apoptosis induced by nelfinavir.
The results demonstrate that nelfinavir may be an effective drug against breast cancer and could be combined with tamoxifen to enhance its efficacy against breast cancer cells. Moreover, the cytotoxic effect of a tamoxifen and nelfinavir combination was independent of the oestrogen receptor status of the analysed breast cancer cells, suggesting a potential benefit of a combination of these two drugs even in patients with no hormone-responsive tumours. We therefore recommend that clinical studies on nelfinavir with breast cancer patients should include this drug combination to analyse the therapeutic efficacy as well as the safety and tolerability of this potential treatment option.
BACKGROUND: The mda-7 gene (melanoma differentiation associated gene-7) is a novel tumor suppressor gene. The anti-proliferative activity of MDA-7 has been previously reported. In this report, we analyze the anti-tumor efficacy of Ad-mda7 in a broad spectrum of cancer lines. MATERIALS AND METHODS: Ad-mda7-transduced cancer or normal cell lines were assayed for cell proliferation (tritiated thymidine incorporation assay, Alamar blue assay, and trypan-blue exclusion assay), apoptosis (TUNEL, and Annexin V staining visualized by fluorescent microscopy or FACs analysis), and cell cycle regulation (Propidium Iodide staining and FACs analysis). RESULTS: Ad-mda7 treatment of tumor cells resulted in growth inhibition and apoptosis in a temporal and dose-dependent manner. The anti-tumor effects were independent of the genomic status of p53, RB, p16, ras, bax, and caspase 3 in these cells. In addition, normal cell lines did not show inhibition of proliferation or apoptotic response to Ad-mda7. Moreover, Ad-mda7-transduced cancer cells secreted a soluble form of MDA-7 protein. Thus, Ad-mda7 may represent a novel gene-therapeutic agent for the treatment of a variety of cancers. CONCLUSIONS: The potent and selective killing activity of Ad-mda7 in cancer cells but not in normal cells makes this vector a potential candidate for cancer gene therapy.
Several epidemiological studies have correlated the use of non-steroidal anti-inflammatory drugs (NSAID) with reduced risk of ovarian cancer, the most lethal gynecological cancer, diagnosed usually in late stages of the disease. We have previously established that the pro-apoptotic cytokine melanoma differentiation associated gene-7/Interleukin-24 (mda-7/IL-24) is a crucial mediator of NSAID-induced apoptosis in prostate, breast, renal and stomach cancer cells. In this report we evaluated various structurally different NSAIDs for their efficacies to induce apoptosis and mda-7/IL-24 expression in ovarian cancer cells. While several NSAIDs induced apoptosis, Sulindac Sulfide and Diclofenac most potently induced apoptosis and reduced tumor growth. A combination of these agents results in a synergistic effect. Furthermore, mda-7/IL-24 induction by NSAIDs is essential for programmed cell death, since inhibition of mda-7/IL-24 by small interfering RNA abrogates apoptosis. mda-7/IL-24 activation leads to upregulation of growth arrest and DNA damage inducible (GADD) 45 α and γ and JNK activation. The NF-κB family of transcription factors has been implicated in ovarian cancer development. We previously established NF-κB/IκB signaling as an essential step for cell survival in cancer cells and hypothesized that targeting NF-κB could potentiate NSAID-mediated apoptosis induction in ovarian cancer cells. Indeed, combining NSAID treatment with NF-κB inhibitors led to enhanced apoptosis induction. Our results indicate that inhibition of NF-κB in combination with activation of mda-7/IL-24 expression may lead to a new combinatorial therapy for ovarian cancer.
MDA-7/IL-24 has noteworthy potential as an anticancer therapeutic because of its diversity of antitumor properties, its lack of toxicity toward normal cells and tissues, and its safety and efficacy as evidenced in a phase I clinical trial. In a recent study, we document that Ad.mda-7-induced ER stress and ceramide production leads to early autophagy that subsequently switches to apoptosis in human prostate cancer cells. During the apoptotic phase, the MDA-7/IL-24 protein physically interacts with Beclin 1 and this interaction might inhibit Beclin 1 function culminating in apoptosis. Conversely, Ad.mda-7 infection leads to calpain-mediated cleavage of the Atg5 protein that might also facilitate a biochemical switch from autophagy to apoptosis. Our recent paper reveals novel aspects of the interplay between autophagy and apoptosis that underlie the cytotoxic action of MDA-7/IL-24 in prostate cancer cells. These new insights into MDA-7/IL-24 action provide intriguing leads for developing innovative combinatorial approaches for prostate cancer therapy.
mda-7/IL-24; protective autophagy; apoptosis; Beclin 1; Atg5
Measles virus (MV), a member of the family Paramyxoviridae, is a nonsegmented negative-strand RNA virus. The RNA helicases retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are differentially involved in the detection of cytoplasmic viral RNAs and induction of alpha/beta interferon (IFN-α/β). RIG-I is generally believed to play a major role in the recognition of paramyxoviruses, whereas many viruses of this family produce V proteins that can inhibit MDA5. To determine the individual roles of MDA5 and RIG-I in IFN induction after MV infection, small interfering RNA-mediated knockdown of MDA5 or RIG-I was performed in the human epithelial cell line H358, which is susceptible to wild-type MV isolates. The production of IFN-β mRNA in response to MV infection was greatly reduced in RIG-I knockdown clones compared to that in H358 cells, confirming the importance of RIG-I in the detection of MV. The IFN-β mRNA levels were also moderately reduced in MDA5 knockdown clones, even though these clones retained fully functional RIG-I. A V protein-deficient recombinant MV (MVΔV) induced higher amounts of IFN-β mRNA at the early stage of infection in H358 cells compared to the parental virus. The reductions in the IFN-β mRNA levels in RIG-I knockdown clones were less pronounced after infection with MVΔV than after infection with the parental virus. Taken together, the present results indicate that RIG-I and MDA5 both contribute to the recognition of MV and that the V protein promotes MV growth at least partly by inhibiting the MDA5-mediated IFN responses.
Transglutamiase-4 (TGase-4), also known as prostate transglutaminase, belongs to the TGase family and is uniquely expressed in the prostate gland. The functions of this interesting protein are not clearly defined. In the present study, we have investigated an unexpected link between TGase-4 and the melanoma differentiation-associated gene-7/interleukin-24 (MDA-7/IL-24), a cytokine known to regulate the growth and apoptosis of certain cancer and immune cells.
Frozen sections of normal and malignant human prostate tissues and human prostate cancer (PCa) cell lines PC-3 and CA-HPV-10, cell lines expressing low and high levels of TGase-4, and recombinant MDA-7/IL-24 (rhMDA-7/IL-24) were used. Expression construct for human TGase-4 was generated using a mammalian expression vector with full length human TGase-4 isolated from normal human prostate tissues. PC-3 cells were transfected with expression construct or control plasmid. Stably transfected cells for control transfection and TGase-4 over expression were created. Similarly, expression of TGase-4 in CA-HPV-10 cells were knocked down by way of ribozyme transgenes. Single and double immunofluorescence microscopy was used for localization and co-localization of TGase-4 and MDA-7/IL-24 in PCa tissues and cells with antibodies to TGase-4; MDA-7/IL-24; IL-20alpha; IL-20beta and IL-22R. Cell-matrix adhesion, attachment and migration were by electric cell substrate impedance sensing and growth by in vitro cell growth assay. A panel of small molecule inhibitors, including Akt, was used to determine signal pathways involving TGase-4 and MDA-7/IL-24.
We initially noted that MDA-7 resulted in inhibition of cell adhesion, growth and migration of human PCa PC-3 cells which did not express TGase-4. However, after the cells over-expressed TGase-4 by way of transfection, the TGase-4 expressing cells lost their adhesion, growth and migratory inhibitory response to MDA-7. On the other hand, CA-HPV-10 cells, a cell type naturally expressing high levels of TGase-4, had a contrasting response to MDA-7 when compared with PC-3 cells. Inhibitor to Akt reversed the inhibitory effect of MDA-7, only in PC-3 control cells, but not the TGase-4 expressing PC-3 cells. In human prostate tissues, TGase-4 was found to have a good degree of co-localization with one of the MDA-7 receptor complexes, IL-20Ra.
The presence of TGase-4 has a biological impact on a prostate cancer cell's response to MDA-7. TGase-4, via mechanism(s) yet to be identified, blocked the action of MDA-7 in prostate cancer cells. This has an important implication when considering the use of MDA-7 as a potential anticancer cytokine in prostate cancer therapies.