Mutation of K-Ras is a frequent oncogenic event in human cancers, particularly cancers of lungs, pancreas, and colon. It remains unclear why some tissues are more susceptible to Ras-induced transformation than others. Here, we globally activated a mutant oncogenic K-Ras allele (K-RasG12D) in mice and examined the tissue-specific effects of this activation on cancer pathobiology, Ras signaling, tumor suppressor, DNA damage, and inflammatory responses. Within 5–6 weeks of oncogenic Ras activation, mice develop oral and gastric papillomas, lung adenomas and hematopoietic hyperproliferation and turn moribund. The oral, gastric and lung pre-malignant lesions display activated Erk1/2 and NF-κB signaling as well as activated tumor suppressor and DNA damage responses. Other organs such as pancreas, liver and small intestine do not exhibit neoplastic progression within six weeks following K-rasG12D activation and do not show a potent tumor suppressor response. Even though robust Erk1/2 signaling is activated in all the tissues examined, the pErk1/2 distribution remains largely cytoplasmic in K-RasG12D refractory tissues (pancreas, liver and intestines) as opposed to a predominantly nuclear localization in K-RasG12D induced neoplasms of lung, oral, and gastric mucosa. The downstream targets of Ras signaling, pElk-1 and c-Myc, are elevated in K-RasG12D induced neoplastic lesions but not in K-RasG12D refractory tissues. We propose that oncogenic K-Ras refractory tissues delay oncogenic progression by spatially limiting the efficacy of Ras/Raf/Erk1/2 signaling, whereas K-Ras responsive tissues exhibit activated Ras/Raf/Erk1/2 signaling, rapidly form pre-malignant tumors, and activate potent anti-tumor responses that effectively prevent further malignant progression.
K-Ras; ERK1/2; Elk-1; nuclear translocation; p53
The platelet-derived growth factors (PDGF A, B, C, and D) and their receptors (α-PDGFR and β-PDGFR) play an indispensible role in physiologic and pathologic conditions, including tumorigenesis. The transformative β-PDGFR is overexpressed and activated during prostate cancer progression, but the identification and functional significance of its complementary ligand have not been elucidated. This study examined potential oncogenic functions of β-PDGFR ligands PDGF B and PDGF D, using nonmalignant prostate epithelial cells engineered to overexpress these ligands. In our models, PDGF D induced cell migration and invasion more effectively than PDGF B in vitro. Importantly, PDGF D supported prostate epithelial cell tumorigenesis in vivo and showed increased tumor angiogenesis compared with PDGF B. Autocrine signaling analysis of the mitogen-activated protein kinase and phosphoinositide 3-kinase pathways found PDGF D–specific activation of the c-jun-NH2-kinase (JNK) signaling cascade. Using short hairpin RNA and pharmacologic inhibitors, we showed that PDGFD-mediated phenotypic transformation is β-PDGFR and JNK dependent. Importantly, we made a novel finding of PDGF D–specific increase in the shedding and activation of the serine protease matriptase in prostate epithelial cells. Our study, for the first time to our knowledge, showed ligand-specific β-PDGFR signaling as well as PDGF D–specific regulation of matriptase activity and its spatial distribution through shedding. Taken together with our previous finding that matriptase is a proteolytic activator of PDGF D, this study provides a molecular insight into signal amplification of the proteolytic network and PDGF signaling loop during cancer progression.
The degree of differentiation in human cancers generally reflects the degree of malignancy, with the most undifferentiated cancer being also the highest grade and the most aggressive. High-grade serous ovarian carcinomas (HGSOC) are poorly differentiated and fast-growing malignancies. The molecular mechanisms underlying the poor differentiation of HGSOC has not been completely characterized. Evidence suggests that miRNA, miR are dysregulated in HGSOC. Therefore, we focused on those miRNAs that are relevant to tumor differentiation. Expression profiling of miRNAs in HGSOC, indicated miR-106a and its family members were significantly upregulated. Upregulation of miR-106a was further validated by real-time reverse transcriptase PCR (qRT-PCR) and miRNA in situ hybridization in a large cohort of HGSOC specimens. Overexpression of miR-106a in benign and malignant ovarian cells significantly increased the cellular proliferation rate and expanded the side-population fraction. In particular, SKOV3 cells with miR-106a overexpression had significantly higher tumor initial/stem cell population (CD24- and CD133-positive cells) than control SKOV3 cells. Among many miR-106a predicated target genes, p130 (RBL2), an retinoblastoma (Rb) tumor suppressor family member, was not only confirmed as a specific target of miR-106a but also related to tumor growth and differentiation. The importance of mir-106a and RBL2 was further demonstrated in vivo, in which, SKOV3 cells overexpressing miR-106a formed poorly differentiated carcinomas and had reduced RBL2 levels. To our knowledge, this is the first study of miR-106a mediating proliferation and tumor differentiation in HGSOC.
The current study suggests that the RB tumor suppressor pathway is a critical regulator of growth and differentiation in HGSOC.
Ku70 was originally described as an auto-antigen, but it also functions as DNA repair protein in the nucleus and as an anti-apoptotic protein by binding to Bax in the cytoplasm, blocking Bax-mediated cell death. In neuroblastoma (NB) cells, Ku70’s binding with Bax is regulated by Ku70 acetylation such that increasing Ku70 acetylation results in Bax release, triggering cell death. While regulating cytoplasmic Ku70 acetylation is important for cell survival, the role of nuclear Ku70 acetylation in DNA repair is unclear. Here we demonstrated that Ku70 acetylation in the nucleus is regulated by the CREB-binding protein (CBP), and that Ku70 acetylation plays an important role in DNA repair in NB cells. We treated NB cells with ionization radiation and measured DNA repair activity as well as Ku70 acetylation status. Cytoplasmic and nuclear Ku70 were acetylated after ionization radiation in NB cells. Interestingly, cytoplasmic Ku70 was redistributed to the nucleus following irradiation. Depleting CBP in NB cells results in reducing Ku70 acetylation and enhancing DNA repair activity in NB cells suggesting nuclear Ku70 acetylation may have an inhibitory role in DNA repair. These results provide support for the hypothesis that enhancing Ku70 acetylation, through deacetylase inhibition, may potentiate the effect of ionization radiation in NB cells.
acetyltransferase; histone deacetylase; Ku70; Bax; CBP; cell death
High grade non-muscle invasive bladder cancer is commonly treated with Bacillus Calmette-Guérin, an immunotherapeutic that depends on fibronectin and tumor cell integrin α5β1 for internalization into bladder cancer cells. We previously demonstrated that the anti-angiogenic peptide CLT1 forms cytotoxic complexes with fibronectin that are cooperatively internalized into proliferating endothelium through ligation of integrins and chloride intracellular channel 1. While CLT1 has no effect on mature, differentiated cells, we show here that CLT1 is highly cytotoxic for a panel of bladder tumor cell lines as well as a variety of cell lines derived from kidney, lung, breast and prostate cancer. Paralleling our previous results, we found CLT1-induced tumor cell death to be increased in the presence of fibronectin, which mediated CLT1 internalization and subsequent autophagic cell death in a mechanism that depends on tumor cell integrin α5β1 and chloride intracellular channel 3 (CLIC3). This mechanistic link was further supported by our results showing upregulation of α5β1 and CLIC3 in CLT1-responsive tumor cell lines and co-localization with CLT1 in tumor tissues. Incubating tumor tissue from bladder cancer patients with fluorescein-conjugated CLT1 resulted in a strong and specific fluorescence while normal bladder tissue remained negative. Based on its affinity for bladder tumor tissue and strong anti-tumor effects, we propose that CLT1 could be useful for targeting bladder cancer.
CLT1; fibronectin; bladder cancer; integrin α5β1; chloride intracellular channel 3
Previously we reported caveolin-1 (Cav-1) overexpression in prostate cancer (PCa) cells and demonstrated that it promotes PCa progression. Here, we report that Cav-1 was overexpressed in 41.7% (15 of 36) of high-grade prostatic intraepithelial neoplasia (HGPIN) specimens obtained during radical prostatectomies. Positive correlations exist between Cav-1–positive (Cav-1+) HGPIN and Cav-1+ primary PCa (rho = 0.655, P< 0.0001) and between Cav-1 and c-Myc expression in HGPIN (rho = 0.41, P = 0.032). To determine whether Cav-1 cooperates with c-Myc in development of premalignant lesions and PCa in vivo, we generated transgenic mice with c-Myc overexpression driven by the ARR2PB promoter. In this ARR2PB–c-myc model, Cav-1 overexpression was found in mouse PIN (mPIN) lesions and PCa cells and was associated with a significantly higher ratio of proliferative to apoptotic labeling in mPIN lesions than in the Cav-1–negative epithelia adjacent to those lesions (10.02 vs 4.34; P = 0.007). Cav-1 overexpression was also associated with increased levels of P-Akt and VEGF-A, which were previously associated with Cav-1–induced PCa cell survival and positive-feedback regulation of cellular Cav-1 levels, respectively. In multiple PCa cell lines, Cav-1 protein (but not mRNA) was induced by c-Myc transfection, whereas VEGF siRNA transfection abrogated c-Myc–induced Cav-1 overexpression, suggesting a c-Myc–VEGF–Cav-1 signaling axis. Overall, our results suggest that Cav-1 is associated with c-Myc in the development of HGPIN and PCa. Further, Cav-1 overexpression in HGPIN is potentially a biomarker for early identification of patients who tend to develop Cav-1+ primary PCa.
Caveolin-1; c-Myc; prostatic intraepithelial neoplasia; prostate cancer; metaplasia
The roles of cholecystokinin 2 receptor (CCK2R) in numerous physiologic processes in the gastrointestinal tract and central nervous system are ‘well documented. There has been some evidence that CCK2R alterations play a role in cancers, but the functional significance of these alterations for tumorigenesis is unknown. We have identified six mutations in CCK2R among a panel of 140 colorectal cancers and 44 gastric cancers. We show that these mutations increase receptor activity, activate multiple downstream signaling pathways, increase cell migration, and promote angiogenesis. Our findings suggest that somatic mutations in CCK2R may promote tumorigenesis through deregulated receptor activity and highlight the importance of evaluating CCK2R inhibitors to block both the normal and mutant forms of the receptor.
NFBD1/MDC1 is involved in DNA damage checkpoint signaling and DNA repair. NFBD1 binds to the chromatin component γH2AX at sites of DNA damage, causing amplification of ataxia telangiectasia-mutated gene (ATM) pathway signaling and recruitment of DNA repair factors. Residues 508–995 of NFBD1 possess transactivation activity, suggesting a possible role of NFBD1 in transcription. Furthermore, NFBD1 influences p53-mediated transcription in response to adriamycin. We sought to determine the role of NFBD1 in ionizing radiation (IR)–responsive transcription and if NFBD1 influences transcription independently of p53.
Using microarray analysis, we identified genes altered upon NFBD1 knockdown. Surprisingly, most NFBD1 regulated genes are regulated in both the absence and presence of IR, thus pointing toward a novel function for NFBD1 outside of the DNA damage response. Furthermore, NFBD1 knockdown regulated genes mostly independent of p53 knockdown. These genes are involved in pathways including focal adhesion signaling, carbohydrate metabolism, and insulin signaling.
We found that CAV1 and CAV2 mRNA and protein levels are reduced by both NFBD1 knockdown and knockout independently of IR and p53. NFBD1-depleted cells exhibit some similar phenotypes to Cav1-depleted cells. Furthermore, like Cav1-depletion, NFBD1 shRNA increases Erk phosphorylation. Thus, Cav1 could act as a mediator of the DNA-damage independent effects of NFBD1 in mitogenic signaling.
ErbB4 is unusual among receptor tyrosine kinases because some isoforms can be efficiently cleaved at the plasma membrane to release a soluble intracellular domain. The cleavage product has high kinase activity and homes to the nucleus. A screen for proteins that associate with the ErbB4 intracellular domain identified candidate interactors including ITCH, WWP2, Nucleolin, and Krab-associated protein 1 (Kap1). Kap1 binds to multiple isoforms of ErbB4 but does not require ErbB4 kinase activity for binding, nor is it an ErbB4 substrate. Kap1 reduces ERBB4 transcription and either directly or indirectly modulates the expression of genes that are themselves regulated by ErbB4. Upregulation of ErbB4 and suppression of MDM2 jointly enhance and accelerate the accumulation of p21CIP1 in response to DNA damage. Overall, these findings further substantiate the role of ErbB4 in conjoint regulation of growth factor signaling and DNA damage responses.
Loss of TGF-β type II receptor (TβRII, encoded by Tgfbr2) expression in the prostate stroma contributes to prostate cancer initiation, progression, and invasion. We evaluated whether TβRII loss also affected prostate cancer bone metastatic growth. Immunohistologic analysis revealed that TβRII expression was lost in cancer-associated fibroblasts in human prostate cancer bone metastatic tissues. We recapitulated the human situation with a conditional stromal Tgfbr2 knockout (Tgfbr2-KO) mouse model. Conditioned media from primary cultured Tgfbr2-KO or control Tgfbr2-flox prostatic fibroblasts (koPFCM or wtPFCM, respectively) were applied to C4-2B prostate cancer cells before grafting the cells tibially. We found that koPFCM promoted prostate cancer cell growth in the bone and development of early mixed osteoblastic/osteolytic bone lesions. Furthermore, the koPFCM promoted greater C4-2B adhesion to type-I collagen, the major component of bone matrix, compared to wtPFCM-treated C4-2B. Cytokine antibody array analysis revealed that koPFCM had more than two-fold elevation in granulocyte colony-stimulating factor and CXCL1, CXCL16, and CXCL5 expression relative to wtPFCM. Interestingly, neutralizing antibodies of CXCL16 or CXCL1 were able to reduce koPFCM-associated C4-2B type-I collagen adhesion to that comparable with wtPFCM-mediated adhesion. Collectively, our data indicate that loss of TGF-β responsiveness in prostatic fibroblasts results in upregulation of CXCL16 and CXCL1 and that these paracrine signals increase prostate cancer cell adhesion in the bone matrix. These microenvironment changes at the primary tumor site can mediate early establishment of prostate cancer cells in the bone and support subsequent tumor development at the metastatic site.
Malignant gliomas are highly invasive tumors with an almost invariably rapid and lethal outcome. Surgery and chemoradiotherapy fail to remove resistant tumor cells that disperse within normal tissue, which are a major cause for disease progression and therapy failure. Infiltration of the neural parenchyma is a distinctive property of malignant gliomas compared to other solid tumors. Thus, glioma cells are thought to produce unique molecular changes that remodel the neural extracellular matrix and form a microenvironment permissive for their motility. Here we describe the unique expression and pro-invasive role of fibulin-3, a mesenchymal matrix protein specifically upregulated in gliomas. Fibulin-3 is downregulated in peripheral tumors and thought to inhibit tumor growth. However, we found fibulin-3 highly upregulated in gliomas and cultured glioma cells, although the protein was undetectable in normal brain or cultured astrocytes. Overexpression and knockdown experiments revealed that fibulin-3 did not seem to affect glioma cell morphology or proliferation, but enhanced substrate-specific cell adhesion and promoted cell motility and dispersion in organotypic cultures. Moreover, orthotopic implantation of fibulin-3-overexpressing glioma cells resulted in diffuse tumors with increased volume and rostrocaudal extension compared to controls. Tumors and cultured cells overexpressing fibulin-3 also showed elevated expression and activity of matrix metalloproteases, such as MMP-2/9 and ADAMTS-5. Taken together, our results suggest that fibulin-3 has a unique expression and pro-tumoral role in gliomas, and could be a potential target against tumor progression. Strategies against this glioma-specific matrix component could disrupt invasive mechanisms and restrict dissemination of these tumors.
EFEMP-1; fibulin; proteoglycans; extracellular matrix; glioma invasion
Glioblastoma (GBM) is the most common and severe primary brain tumor in adults. Its aggressive and infiltrative nature renders the current therapeutics of surgical resection, radiation, and chemotherapy relatively ineffective. Accordingly, recent research has focused on the elucidation of various signal transduction pathways in GBM, particularly aberrant activation. This review focuses on the STAT-3 signal transduction pathway in the context of this devastating tumor. STAT-3 is aberrantly activated in human GBM tissues, and this activation is implicated in controlling critical cellular events thought to be involved in gliomagenesis such as cell cycle progression, apoptosis, angiogenesis, and immune evasion. There are no reports of gain of function mutations in GBM; rather, the activation of STAT-3 is thought to be a consequence of either dysregulation of upstream kinases or loss of endogenous inhibitors. This review provides detailed insight into the multiple mechanisms of STAT-3 activation in GBM, as well as describing endogenous and chemical inhibitors of this pathway and their clinical significance. In GBM, STAT-3 acts a “molecular hub” to link extracellular signals to transcriptional control of proliferation, cell cycle progression, and immune evasion. Because STAT-3 plays this central role in GBM signal transduction, it has significant potential as a therapeutic target.
STATs; Gliomas; Signal Transduction
Caveolin-1 (cav-1) and the cancer-promoting growth factors vascular endothelial growth factor (VEGF), transforming growth factor β1 (TGF-β1), and fibroblast growth factor 2 (FGF2) are often found to be up-regulated in advanced prostate cancer and other malignancies. However, the relationship between cav-1 overexpresson and growth factor up-regulation remains unclear. This report presents the first evidence to our knowledge that in prostate cancer cells, a positive autoregulatory feedback loop is established in which VEGF, TGF-β1, and FGF2 up-regulate cav-1, and cav-1 expression, in turn, leads to increased levels of VEGF, TGF-β1, and FGF2 mRNA and protein, resulting in enhanced invasive activities of prostate cancer cells, i.e., migration and motility. Our results further demonstrate that cav-1–enhanced mRNA stability is a major mechanism underlying the up-regulation of these cancer-promoting growth factors. PI3-K-Akt signaling is required for forming this positive autoregulatory feedback loop.
caveolin-1; Akt; cancer promoting growth factors; mRNA stability
Environmental exposures during sensitive windows of development can reprogram normal physiological responses and alter disease susceptibility later in life in a process known as developmental reprogramming. For example, exposure to the xenoestrogen diethylstilbestrol (DES) during reproductive tract development can reprogram estrogen-responsive gene expression in the myometrium, resulting in hyper-responsiveness to hormone in the adult uterus and promotion of hormone-dependent uterine leiomyoma. We show here that the environmental estrogens genistein (GEN), a soy phytoestrogen, and the plasticizer bisphenol A (BPA), differ in their pattern of developmental reprogramming and promotion of tumorigenesis (leiomyomas) in the uterus. While both GEN and BPA induce genomic estrogen receptor (ER) signaling in the developing uterus, only GEN induced PI3K/AKT non-genomic ER signaling to the histone methyltransferase Enhancer of Zeste homolog 2 (EZH2). As a result, this “pre-genomic” signaling phosphorylates and represses EZH2, and reduces levels of H3K27 repressive mark in chromatin. Furthermore, only GEN caused estrogen-responsive genes in the adult myometrium to become hyper-responsive to hormone; estrogen-responsive genes were repressed in BPA exposed uteri. Importantly, this pattern of EZH2 engagement to decrease versus increase H3K27 methylation correlated with the effect of these xenoestrogens on tumorigenesis. Developmental reprogramming by GEN promoted development of uterine leiomyomas, increasing tumor incidence and multiplicity, while BPA did not. These data demonstrate that environmental estrogens have distinct non-genomic effects in the developing uterus that determines their ability to engage the epigenetic regulator EZH2, decrease levels of the repressive epigenetic histone H3K27 methyl mark in chromatin during developmental reprogramming, and promote uterine tumorigenesis.
developmental reprogramming; xenoestrogens; uterine leiomyoma; genistein; bisphenol A; EZH2
PARP inhibitors show promise as combination and single agents in cancer chemotherapy. Here, we evaluate results obtained with mouse fibroblasts and the common laboratory PARP inhibitor, 4-amino-1,8-naphthalimide (4-AN), and analyze the potential for enhanced cytotoxicity following the combination of a DNA damaging agent and a PARP inhibitor. Methylated DNA bases are repaired by the monofunctional glycosylase-initiated single-nucleotide base excision repair (BER) pathway. An intermediate of this process has a single-nucleotide gap in double-stranded DNA containing the 5′-deoxyribose phosphate (dRP) group atone margin. This 5′-dRP group is removed by the lyase activity of pol β prior to gap filling, then completion of repair is by DNA ligation. PARP-1 binds to and is activated by the 5′-dRP group-containing intermediate, and poly(ADP-ribos)ylation is important for efficient repair. 4-AN-mediated sensitization to the methylating chemotherapeutic agent temozolomide is extreme, producing a level of cytotoxicity not seen with either agent alone. In contrast, with agents producing oxidative DNA damage repaired by bifunctional glycosylase-initiated BER, there is only weak sensitization by co-treatment with PARP inhibitor. Other clinically utilized DNA-damaging agents repaired by different DNA repair pathways also reveal minimal 4-AN-mediated sensitization. This information has potentially important implications for strategic use of PARP inhibitors in chemotherapy.
PARP inhibitor; mouse fibroblasts; base excision repair
Although Dopamine and cAMP-regulated phosphoprotein, Mr 32000 (DARPP-32) is overexpressed in two-thirds of gastric cancers, it impact on molecular functions has not been fully characterized. In this study, we examined the role of DARPP-32 in gastric cancer cell invasion. Using matrigel coated Boyden chamber invasion assay, DARPP-32-overexpressing AGS cells showed 3-fold increase in invasion relative to the vector control (p<0.01). We also tested the trans-endothelial cell invasion as a measure of cell aggressiveness using the impedance-based HUVEC invasion assay and obtained similar results (p<0.001). Western blot analysis indicated that overexpression of DARPP-32 mediated an increase in the MT1-MMPand CXCR4 protein levels. Consistent with the role of MT1-MMP in cleaving extracellular matrix proteins initiating the activation of soluble MMPs, we detected a robust increase in MMP-2 activity in DARPP-32-overexpressing cells. The knockdown of endogenous DARPP-32 in the MKN-45 cells reversed these signaling events and decreased cell invasive activity. We tested whether the invasive activity mediated by DARPP-32 might involve sustained signaling via CXCR4-dependent activation of the MT1-MMP/MMP-2 pathway. The small-molecule CXCR4 antagonist (AMD3100) and CXCR4-siRNA blocked DARPP-32-induced cell invasion. We further examined our hypothesis that DARPP-32 could interact with CXCR4 and stabilize its levels following stimulation with its ligand, CXCL12. Using reciprocal co-immunoprecipitation and immunofluorescence experiments, we found that DARPP-32 and CXCR4 co-exist in the same protein complex. DARPP-32 prolonged the CXCR4 protein half-life and reduced ubiquitination of the CXCR4 protein, following treatment with its ligand, CXCL12. In conclusion, these findings demonstrate a novel mechanism by which DARPP-32 promotes cell invasion by regulating CXCR4-mediated activation of the MT1-MMP/MMP-2 pathway.
MMPs; CXCL-12; MT1-MMP; invasion; DARPP-32
Radiation oncology modalities such as intensity-modulated and image-guided radiation therapy can reduce the high dose to normal tissue and deliver a heterogeneous dose to tumors focusing on areas deemed at highest risk for tumor persistence. Clinical radiation oncology produces daily doses ranging from 1 to 20 Gy, with tissues being exposed to 30 or more daily fractions. Hypothesizing that cells that survive fractionated radiation therapy have a substantially different phenotype than the untreated cells, which might be exploitable for targeting with molecular therapeutics or immunotherapy, three prostate cancer cell lines (PC3, DU145 and LNCaP) and normal endothelial cells were studied to understand the biology of differential effects of multi-fraction (MF) radiation of 0.5, 1 and/or 2 Gy fraction to 10 Gy total dose, and a single dose (SD) of 5 and 10 Gy. The resulting changes in mRNA, miRNA and phosphoproteome were analyzed. Significant differences were observed in the MF radiation exposures including those from the 0.5 Gy MF that produces little cell killing. As expected, p53 function played a major role in response. Pathways modified by MF include immune response, DNA damage, cell cycle arrest, TGF-β, survival and apoptotic signal transduction. The radiation-induced stress response will set-forth a unique platform for exploiting the effects of radiation therapy as “focused biology” for cancer treatment in conjunction with molecular targeted or immunologically directed therapy. Given that more normal tissue is treated, albeit to lower doses with these newer techniques, the response of the normal tissue may also influence long-term treatment outcome.
To identify genes that contribute to chemotherapy resistance in glioblastoma, we conducted a synthetic lethal screen in a chemotherapy-resistant glioblastoma derived cell line with the clinical alkylator temozolomide (TMZ) and an siRNA library tailored towards “druggable” targets. Select DNA repair genes in the screen were validated independently, confirming the DNA glycosylases UNG and MYH as well as MPG to be involved in the response to high dose TMZ. The involvement of UNG and MYH is likely the result of a TMZ-induced burst of reactive oxygen species. We then compared the human TMZ sensitizing genes identified in our screen with those previously identified from alkylator screens conducted in E. coli and S. cerevisiae. The conserved biological processes across all three species composes an Alkylation Functionome that includes many novel proteins not previously thought to impact alkylator resistance. This high-throughput screen, validation and cross-species analysis was then followed by a mechanistic analysis of two essential nodes: base excision repair (BER) DNA glycosylases (UNG, human and mag1, S. cerevisiae) and protein modification systems, including UBE3B and ICMT in human cells or pby1, lip22, stp22 and aim22 in S. cerevisiae. The conserved processes of BER and protein modification were dual targeted and yielded additive sensitization to alkylators in S. cerevisiae. In contrast, dual targeting of BER and protein modification genes in human cells did not increase sensitivity, suggesting an epistatic relationship. Importantly, these studies provide potential new targets to overcome alkylating agent resistance.
Temozolomide; chemotherapy resistance; alkylation response; siRNA; DNA Repair
While the importance of RGS-GAIP–interacting protein (GIPC) in the biology of malignant cells is well known, the molecular mechanism of GIPC in the inhibition of tumor progression has not been identified. This study focused on elucidating the molecular role of GIPC in breast cancer progression. By using a human breast tumor specimen, an in vivo mouse model, and breast cancer cell lines, we showed for the first time that GIPC is involved in breast cancer progression through regulation of breast cancer cell proliferation, survival, and invasion. Furthermore, we found that the Akt/Mdm2/p53 axis, insulin-like growth factor-1 receptor (IGF-1R), matrix metalloproteinase-9 (MMP-9), and Cdc42 were downstream of GIPC signaling in breast cancer cells. Moreover, we showed that wild-type p53 reduced GIPC-induced breast cancer cell survival, whereas mutant p53 inhibited GIPC-induced cell invasion. Finally, we demonstrated that a myristylated GIPC peptide (CR1023, Myristoyl-PSQSSSEA) capable of blocking the PDZ domain of GIPC successfully inhibited MDA-MB-231 cell proliferation, survival, and further in vivo tumor growth. Taken together, these findings demonstrate the importance of GIPC in breast tumor progression, which has a potentially significant impact on the development of therapies against many common cancers expressing GIPC, including breast and renal cancer.
breast cancer; RGS-GAIP-interacting protein; invasion; migration; apoptosis; proliferation; p53; GIPC peptide; CR1023; myristylation
Medical therapy of patients with malignancy requires a paradigm shift through development of new drugs with a good safety record and novel mechanisms of activity. While there is no dearth of such molecules, one particular agent, “reovirus” is promising by its ability to target cancer cells with aberrant signaling pathways. This double stranded RNA virus has been therapeutically formulated and has rapidly progressed from pre-clinical validation of anti cancer activity to a phase III registration study in platinum refractory metastatic squamous cell carcinoma of the head and neck. During this process, reovirus has demonstrated safety both as a single agent when administered intratumorally and intravenously, as well as in combination therapy, with multiple chemotherapeutics such as gemcitabine, carboplatin/paclitaxel, and docetaxel; and similarly with radiation. The scientific rationale for its development as an anticancer agent stems from the fact that it preferentially replicates in and induces lyses of cells with an activated Kras pathway. As documented in many previous studies, the initial observation of greater tropism in Kras compromised situation might certainly not be the sole and possibly not even the predominant reason for enhanced virulence. All the same, scientists have emphasized on Kras optimistically due to its high prevalence in various types of cancers. Incidence of Kras mutation has been found to be highest in pancreatic cancer (85–90%) followed by colorectal (35–45%) and lung (25–30%). Reovirus, in fact has the potential not only as a therapy but also as a tool to unravel the aberrant cellular pathway leading to carcinogenicity.
PRSS3/mesotrypsin is an atypical isoform of trypsin that has been associated with breast, lung, and pancreatic cancer cell malignancy. In analyses of open source transcriptional microarray data, we find that PRSS3 expression is upregulated in metastatic prostate cancer tissue, and that expression of PRSS3 in primary prostate tumors is prognostic of systemic progression following prostatectomy. Using a mouse orthotopic model with bioluminescent imaging, we show that PRSS3/mesotrypsin is critical for prostate cancer metastasis. Silencing of PRSS3 inhibits anchorage independent growth of prostate cancer cells in soft agar assays, and suppresses invasiveness in Matrigel transwell assays and three-dimensional (3D) cell culture models. We further show that treatment with recombinant mesotrypsin directly promotes an invasive cellular phenotype in prostate cancer cells, and find that these effects are specific and require the proteolytic activity of mesotrypsin, because neither cationic trypsin nor a mesotrypsin mutant lacking activity can drive the invasive phenotype. Finally, we demonstrate that a newly developed, potent inhibitor of mesotrypsin activity can suppress prostate cancer cell invasion to a similar extent as PRSS3 gene silencing. This study defines mesotrypsin as an important mediator of prostate cancer progression and metastasis, and suggests that inhibition of mesotrypsin activity may provide a novel modality for prostate cancer treatment.
prostate cancer; metastasis; PRSS3; mesotrypsin; proteases; protease inhibitors
The transmembrane mucin MUC1 is overexpressed in most ductal carcinomas, and its overexpression is frequently associated with metastatic progression. MUC1 can drive tumor initiation and progression via interactions with many oncogenic partners, including β-catenin, the epidermal growth factor receptor (EGFR) and Src. The decoy peptide PMIP (Protein transduction domain MUC1 Inhibitory Peptide) has been shown to inhibit the tumor promoting activities of MUC1 in breast and lung cancer, including cell growth and invasion, and its usage suppresses metastatic progression in mouse models of breast cancer. To further characterize the reduced metastasis observed upon PMIP treatment, we performed motility assays and observed that PMIP inhibits cell motility of breast cancer cells. To determine the mechanism by which PMIP inhibits motility, we evaluated changes in global gene transcription upon PMIP treatment, and identified a number of genes with altered expression in response to PMIP. Among these genes is the metastatic mediator, c-Met, a transmembrane tyrosine kinase that can promote cell scattering, migration and invasion. To further investigate the role of c-Met in MUC1-dependent metastatic events, we evaluated the effects of MUC1 expression and EGFR activation on breast cancer cell scattering, branching and migration. We found that MUC1 strongly promoted all of these events and this effect was further amplified by EGF treatment. Importantly, the effect of MUC1 and EGF on these phenotypes was dependent upon c-Met activity. Overall, these results indicate that PMIP can block the expression of a key metastatic mediator, further advancing its potential use as a clinical therapeutic.
MUC1; Epidermal Growth Factor Receptor; therapy; c-Met; migration; breast cancer
Colorectal cancer is the third leading cause of cancer-related mortality in the world. The main cause of death of colorectal cancer is hepatic metastases which can be treated using isolated hepatic perfusion (IHP), allowing treatment of colorectal metastasis with various methods. In this study we present a novel potent multimodality strategy comprising humanized death receptor 4 (DR4) antibody mapatumumab (Mapa) in combination with oxaliplatin and hyperthermia to treat human colon cancer cells. Oxaliplatin and hyperthermia sensitized colon cancer cells to Mapa in the mitochondrial dependent apoptotic pathway and increased reactive oxygen species production, leading to Bcl-xL phosphorylation at Serine 62 in a c-Jun N-terminal kinase (JNK)-dependent manner. Overexpression of Bcl-xL reduced the efficacy of the multimodality treatment, while phosphorylation of Bcl-xL decreased its anti-apoptotic activity. The multimodality treatment dissociated Bcl-xL from Bax, allowing Bax oligomerization to induce cytochrome c release from mitochondria. In addition, the multimodality treatment significantly inhibited colorectal cancer xenografts’ tumor growth. The successful outcome of this study will support the application of multimodality strategy to colorectal hepatic metastases.
Mapatumumab; Hyperthermia; Oxaliplatin; Mitochondria-dependent pathway
Data accumulated over the latest two decades have established that the serine protease urokinase-type plasminogen activator (uPA) is a potential therapeutic target in cancer. When designing inhibitors of the proteolytic activity of serine proteases, obtaining sufficient specificity is problematic since the topology of the proteases’ active sites are highly similar. In an effort to generate highly specific uPA inhibitors with new inhibitory modalities, we isolated uPA-binding RNA aptamers by screening a library of 35 nucleotides long 2′-fluoro-pyrimidine RNA molecules using as bait a version of human pro-uPA lacking the epidermal growth factor-like and kringle domains. One pro-uPA binding aptamer sequence, referred to as upanap-126, proved to be highly specific for human uPA. Upanap-126 delayed the proteolytic conversion of human pro-uPA to active uPA, but did not inhibit plasminogen activation catalysed by two-chain uPA. The aptamer also inhibited the binding of pro-uPA to uPAR and the binding of vitronectin to the preformed pro-uPA/uPAR complexes both in cell-free systems and on cell surfaces. Furthermore, upanap-126 inhibited human tumour cell invasion in vitro, in the Matrigel assay, and in vivo, in the chick embryo assay of cell escape from microtumours. Finally, upanap-126 significantly reduced the levels of tumour cell intravasation and dissemination in the chick embryo model of spontaneous metastasis. Together, our findings demonstrate that utilisation of upanap-126 represents a novel multi-functional mechanistic modality for inhibition of uPA-dependent processes involved in tumour cell spread.
zymogen; cancer; metastasis; serine protease; urokinase-type plasminogen activator receptor