Cetuximab, a monoclonal blocking antibody against the epidermal growth factor receptor EGFR, has been approved for the treatment of squamous cell carcinomas of the head and neck (HNSCC). However, only few patients display long-term responses, prompting the search for cetuximab resistance mechanisms and new therapeutic options enhancing cetuximab effectiveness.
Cetuximab-sensitive HNSCC cells were retro-engineered to express PIK3CA and RAS oncogenes. These cells and HNSCC cells harboring endogenous PIK3CA and RAS oncogenes were xenografted into mice (n = 10 per group) and studied for their biochemical, antitumor, antiangiogenic, and antilymphangiogenic responses to cetuximab and mTOR targeting agents. All P values are two-sided.
Cetuximab treatment of PIK3CA- and RAS-expressing HNSCC xenografts promoted an initial antitumor response, but all tumors relapsed within few weeks. In these tumors, cetuximab did not decrease the activity of mTOR, a downstream signaling target of EGFR, PIK3CA, and RAS. The combined administration of cetuximab and mTOR inhibitors exerted a remarkably increased antitumor activity, particularly in HNSCC cells that are resistant to cetuximab as a single agent. Indeed, cotargeting mTOR together with cetuximab caused a rapid tumor collapse of both PIK3CA- and RAS-expressing HNSCC xenografts (P < .001), concomitant with reduced proliferation (P < .001) and lymphangiogenesis (P < .001).
The presence of PIK3CA and RAS mutations and other alterations affecting the mTOR pathway activity in HNSCC could be exploited to predict the potential resistance to cetuximab, and to select the patients that may benefit the most from the concomitant administration of cetuximab and PI3K and/or mTOR inhibitors as a precision molecular therapeutic option for HNSCC patients.
G-protein coupled receptors (GPCRs) represent the largest family of cell surface molecules involved in signal transduction. Surprisingly, open reading frames for multiple GPCRs were hijacked in the process of co-evolution between herpesviridae family viruses and their human and mammalian hosts. Virally encoded GPCRs (vGPCRs) evolved as parts of viral genomes, which allowed harnessing the power of host GPCR signaling circuitries to ensure viral replicative success. Although vGPCRs are phylogenetically related to human chemokine receptors, they feature a number of unique characteristics. Here, we describe the molecular mechanisms underlying vGPCR-mediated viral pathogenesis which include constitutive activity, aberrant coupling to human G-proteins and β-arrestins, binding and activation by human chemokines, and dimerization with human GPCRs expressed in infected cells. The likely structural basis for these molecular events is described for the two closest viral homologs of human GPCRs. This information can be exploited for developing novel targeted therapeutic strategies against viral diseases.
Signal Transduction; Structure; Viral-Associated Malignancies; Chemokine Receptors; Constitutive Activity; Human Viruses
Activating mutations in GNAQ and GNA11, encoding members of the Gαq family of G protein α subunits, are the driver uveal melanoma oncogenes, while mutations in Gq-linked G proteincoupled receptors (GPCRs) have been identified recently in numerous human malignancies. How Gαq and its coupled receptors transduce mitogenic signals is still unclear, due to the complexity of signaling events perturbed upon Gq activation. Using of a synthetic biology approach and a genome-wide RNAi screen, we found that a highly conserved guanine nucleotide exchange factor, Trio, is essential to activate Rho- and Rac-regulated signaling pathways acting on JNK and p38, thereby transducing proliferative signals from Gαq to the nucleus independently of PLC-β. Indeed, while many biological responses elicited by Gq depend on the transient activation of second messenger system, Gq utilizes a hardwired protein-protein interaction-based signaling circuitry to achieve the sustained stimulation of proliferative pathways, thereby controlling normal and aberrant cell growth.
MAPK; JNK; p38; Rho GTPases; Signal Transduction; G Proteins; Cancer
Strong epidemiologic evidence links smoking and cancer. An increased understanding of the molecular biology of tobacco-related cancers could advance progress toward improving smoking cessation and patient management. Knowledge gaps between tobacco addiction, tumorigenesis, and cancer brought an interdisciplinary group of investigators together to discuss “The Biology of Nicotine and Tobacco: Bench to Bedside.” Presentations on the signaling pathways and pathogenesis in tobacco-related cancers, mouse models of addiction, imaging and regulation of nicotinic receptors, the genetic basis for tobacco carcinogenesis and development of lung cancer, and molecular mechanisms of carcinogenesis were heard. Importantly, new opportunities to use molecular biology to identify and abrogate tobacco-mediated carcinogenesis and to identify high-risk individuals were recognized.
Although prostate cancer typically runs an indolent course, a subset of men develop aggressive, fatal forms of this disease. We hypothesize that germline variation modulates susceptibility to aggressive prostate cancer. The goal of this work is to identify susceptibility genes using the C57BL/6-Tg(TRAMP)8247Ng/J (TRAMP) mouse model of neuroendocrine prostate cancer. Quantitative trait locus (QTL) mapping was performed in transgene-positive (TRAMPxNOD/ShiLtJ) F2 intercross males (n = 228), which facilitated identification of 11 loci associated with aggressive disease development. Microarray data derived from 126 (TRAMPxNOD/ShiLtJ) F2 primary tumors were used to prioritize candidate genes within QTLs, with candidate genes deemed as being high priority when possessing both high levels of expression-trait correlation and a proximal expression QTL. This process enabled the identification of 35 aggressive prostate tumorigenesis candidate genes. The role of these genes in aggressive forms of human prostate cancer was investigated using two concurrent approaches. First, logistic regression analysis in two human prostate gene expression datasets revealed that expression levels of five genes (CXCL14, ITGAX, LPCAT2, RNASEH2A, and ZNF322) were positively correlated with aggressive prostate cancer and two genes (CCL19 and HIST1H1A) were protective for aggressive prostate cancer. Higher than average levels of expression of the five genes that were positively correlated with aggressive disease were consistently associated with patient outcome in both human prostate cancer tumor gene expression datasets. Second, three of these five genes (CXCL14, ITGAX, and LPCAT2) harbored polymorphisms associated with aggressive disease development in a human GWAS cohort consisting of 1,172 prostate cancer patients. This study is the first example of using a systems genetics approach to successfully identify novel susceptibility genes for aggressive prostate cancer. Such approaches will facilitate the identification of novel germline factors driving aggressive disease susceptibility and allow for new insights into these deadly forms of prostate cancer.
Prostate cancer is a remarkably common disease, and in 2014 it is estimated that it will account for 27% of new cancer cases in men in the US. However, less than 13% those diagnosed will succumb to prostate cancer, with most men dying from unrelated causes. The tests used to identify men at risk of fatal prostate cancer are inaccurate, which leads to overtreatment, unnecessary patient suffering, and represents a significant public health burden. Many studies have shown that hereditary genetic variation significantly alters susceptibility to fatal prostate cancer, although the identities of genes responsible for this are mostly unknown. Here, we used a mouse model of prostate cancer to identify such genes. We introduced hereditary genetic variation into this mouse model through breeding, and used a genetic mapping technique to identify 35 genes associated with aggressive disease. The levels of three of these genes were consistently abnormal in human prostate cancers with a more aggressive disease course. Additionally, hereditary differences in these same three genes were associated with markers of fatal prostate cancer in men. This approach has given us unique insights into how hereditary variation influences fatal forms of prostate cancer.
The overexpression of cyclooxygenase (COX)-2 is a frequent event in squamous cell carcinomas of the head and neck (HNSCC), and non-steroidal anti-inflammatory drugs, which are potent inhibitors of COX-1 and COX-2, exert chemopreventive effects on HNSCC cancer development. COX-2 promotes the release of the pro-inflammatory mediator prostaglandin E2 (PGE2), which acts on its cell surface G protein-coupled receptors EP1, EP2, EP3, and EP4. Here, we investigated the role of PGE2 and its receptors in cellular proliferation in HNSCC. The expression of COX-2 and EP1-4 was examined in immortalized oral epithelial cells and in a representative panel of HNSCC cell lines, and based on these data EP1-EP3 and COX-2 expression were evaluated by immunohistochemistry in a large clinical sample collection using HNSCC tissue microarrays. The ability of selective COX-2 inhibition to block PGE2 secretion was measured by ELISA specific assays. The effects of PGE2 on cell proliferation were evaluated using PGE2, its stable analog, and EP2 and EP3-specific synthetic agonists. The results presented here show that HNSCC tumoral lesions and their derived cell lines constitutively express COX-2 and the EP1, EP2 and EP3 receptors for PGE2. HNSCC cells secrete PGE2, which can be suppressed by low concentrations of COX-2 selective inhibitors, without inhibiting cell proliferation. Exogenously added stable PGE2 and EP3-specific agonists induce DNA synthesis in all HNSCC cell lines tested. Overall, our study supports the emerging notion that PGE2 produced in the tumor microenvironment by the overexpression of COX-2 in tumoral and inflammatory cells may promote the growth of HNSCC cells in an autocrine and paracrine fashion by acting on PGE2 receptors that are widely expressed in most HNSCC cancer cells. In particular, our findings suggest that EP3 receptor may play a more prominent role in HNSCC cell growth promotion, thus providing a rationale for the future evaluation of this PGE2 receptor as a target for HNSCC prevention strategies.
Head and neck cancer; Cyclooxygenase; Prostaglandin E2; PGE2 receptors; EP1; EP2; EP3; EP4; G protein-coupled receptors; Oral cancer
LDL-related protein 6 (LRP6) is a coreceptor of WNTs and a key regulator of the WNT/β-catenin pathway. Upon activation, LRP6 is phosphorylated within its intracellular PPPS/TP motifs. These phosphorylated motifs are required to recruit axin and to inhibit glycogen synthase kinase 3 (GSK3), two basic components of the β-catenin destruction complex. On the basis of a kinome-wide small interfering RNA (siRNA) screen and confirmative biochemical analysis, we show that several proline-directed mitogen-activated protein kinases (MAPKs), such as p38, ERK1/2, and JNK1 are sufficient and required for the phosphorylation of PPPS/TP motifs of LRP6. External stimuli, which control the activity of MAPKs, such as phorbol esters and fibroblast growth factor 2 (FGF2) control the choice of the LRP6-PPPS/TP kinase and regulate the amplitude of LRP6 phosphorylation and WNT/β-catenin-dependent transcription. Our findings suggest that cells not only recruit one dedicated LRP6 kinase but rather select their LRP6 kinase depending on cell type and the external stimulus. Moreover, direct phosphorylation of LRP6 by MAPKs provides a unique point for convergence between WNT/β-catenin signaling and mitogenic pathways.
Epidermal integrity is a complex process established during embryogenesis and maintained throughout the organism lifespan by epithelial stem cells. While Wnt regulates normal epithelial stem cell renewal, aberrant Wnt signaling can contribute to cancerous growth. Here, we explored the consequences of persistent expressing Wnt1 in an epidermal compartment that includes the epithelial stem cells. Surprisingly, Wnt caused the rapid growth of the hair follicles, but this was followed by epithelial cell senescence, disappearance of the epidermal stem cell compartment, and progressive hair loss. While Wnt1 induced the activation of β-catenin and the mTOR pathway, both hair follicle hyperproliferation and stem cell exhaustion were strictly dependent on mTOR function. These findings suggest that whereas activation of β-catenin contributes to tumor growth, epithelial stem cells may be endowed with a protective mechanism that results in cell senescence upon the persistent stimulation of proliferative pathways that activate mTOR, ultimately suppressing tumor formation.
Stem cell; mTOR; Wnt; aging; cancer; signal transduction
The recent elucidation of the genomic landscape of head and neck squamous cell carcinoma (HNSCC) has provided a unique opportunity to develop selective cancer treatment options. These efforts will require the establishment of relevant HNSCC models for preclinical testing. Here, we performed full exome and transcriptome sequencing of a large panel of HNSCC-derived cells from different anatomical locations and human papillomavirus (HPV) infection status. These cells exhibit typical mutations in TP53, FAT1, CDK2NA, CASP8, and NOTCH1, and copy number variations (CNVs) and mutations in PIK3CA, HRAS, and PTEN that reflect the widespread activation of the PI3K-mTOR pathway. SMAD4 alterations were observed that may explain the decreased tumor suppressive effect of TGF-β in HNSCC. Surprisingly, we identified HPV+ HNSCC cells harboring TP53 mutations, and documented aberrant TP53 expression in a subset of HPV+ HNSCC cases. This analysis also revealed that most HNSCC cells harbor multiple mutations and CNVs in epigenetic modifiers (e.g., EP300, CREBP, MLL1, MLL2, MLL3, KDM6A, and KDM6B) that may contribute to HNSCC initiation and progression. These genetically-defined experimental HNSCC cellular systems, together with the identification of novel actionable molecular targets, may now facilitate the pre-clinical evaluation of emerging therapeutic agents in tumors exhibiting each precise genomic alteration.
HNSCC; Sequencing; Exome; RNAseq; Cancer
Oral squamous cell carcinoma (OSCC) has a propensity to spread to the cervical lymph nodes (LN). The presence of cervical LN metastases severely impacts patient survival, whereby the two-year survival for oral cancer patients with involved LN is ~30% compared to over 80% in patients with non-involved LN. Elucidation of key molecular mechanisms underlying OSCC metastasis may afford an opportunity to target specific genes, to prevent the spread of OSCC and to improve patient survival. In this study, we demonstrated that expression of the heterotrimeric G-protein alpha-12 (Gα12) is highly up-regulated in primary tumors and LN of OSCC patients, as assessed by quantitative polymerase chain reaction (qPCR) and immunohistochemistry (IHC). We also found that exogenous expression of the constitutively activated-form of Gα12 promoted cell migration and invasion in OSCC cell lines. Correspondingly, inhibition of Gα12 expression by shRNA consistently inhibited OSCC cell migration and invasion in vitro. Further, the inhibition of G12 signaling by regulator of G-protein signaling (RGS) inhibited Gα12-mediated RhoA activation, which in turn resulted in reduced LN metastases in a tongue-orthotopic xenograft mouse model of oral cancer. This study provides a rationale for future development and evaluation of drug candidates targeting Gα12-related pathways for metastasis prevention.
Oral squamous cell carcinoma; G-protein alpha-12; Lymph node; Metastasis
Most proangiogenic polypeptide growth factors and chemokines enhance vascular permeability, including vascular endothelial growth factor (VEGF), the main target for anti-angiogenic-based therapies, and interleukin-8 (IL-8), a potent proinflammatory mediator. Here, we show that in endothelial cells IL-8 initiates a signaling route that converges with that deployed by VEGF at the level of the small GTPase Rac1 and that both act through the p21-activated kinase to promote the phosphorylation and internalization of VE-cadherin. However, whereas VEGF activates Rac1 through Src-related kinases, IL-8 specifically signals to Rac1 through its cognate G protein-linked receptor, CXCR2, and the stimulation of the phosphatidylinositol 3-kinase γ (PI3Kγ) catalytic isoform, thereby providing a specific molecular targeted intervention in vascular permeability. These results prompted us to investigate the potential role of IL-8 signaling in a mouse model for retinal vascular hyperpermeability. Importantly, we observed that IL-8 is upregulated upon laser-induced retinal damage, which recapitulates enhanced vascularization, leakage, and inflammatory responses. Moreover, blockade of CXCR2 and PI3Kγ was able to limit neovascularization and choroidal edema, as well as macrophage infiltration, therefore contributing to reduce retinal damage. These findings indicate that the CXCR2 and PI3Kγ signaling pathway may represent a suitable target for the development of novel therapeutic strategies for human diseases characterized by vascular leakage.
Aberrant expression and activity of G proteins and G protein coupled receptors (GPCRs) are frequently associated with tumorigenesis. Deep sequencing studies show that 4.2% of tumors carry activating mutations in GNAS (encoding Gαs), and that oncogenic activating mutants in genes encoding Gαq family members (GNAQ or GNA11) are present in ~66% and ~6% of melanomas arising in the eye and skin, respectively. Furthermore, nearly 20% of human tumors harbor mutations in GPCRs. Many human cancer-associated viruses also express constitutively active viral GPCRs. These studies indicate that G proteins, GPCRs and their linked signaling circuitry represent novel therapeutic targets for cancer prevention and treatment.
Heparin is commonly used to treat intravascular thrombosis in children undergoing extracorporeal membrane oxygenation or cardiopulmonary bypass. These clinical circumstances are associated with elevated plasma levels of angiotensin II (Ang II). However, the mechanisms by which heparin modulates vascular reactivity of Ang II remain unclear. We hypothesized that heparin may offset Ang II-induced vasoconstriction on mesenteric resistances arteries through modulating the Rho-A/Rho kinase pathway. Vascular contractility was studied using pressurized, resistance-sized mesenteric arteries from mice. Rho-A activation was measured by pull-down assay, and myosin light chain or PKA phosphorylation by immunoblotting. We found that heparin significantly attenuated vasoconstriction induced by Ang II but not that by KCl. The combined effect of Ang II with heparin was almost abolished by a specific Rho kinase inhibitor Y27632. Ang II stimulated Rho-A activation and myosin light chain phosphorylation, both responses were antagonized by heparin. Moreover, the inhibitory effect of heparin on Ang II-induced vasoconstriction was reversed by Rp-cAMPS (cAMP-dependent PKA inhibitor), blunted by ODQ (soluble guanylate cyclase inhibitor), and mimicked by a cell-permeable cGMP analogue, 8-Br-cGMP, but not by a cAMP analogue. PKC and Src kinase were not involved. We conclude that heparin inhibits Ang II-induced vasoconstriction through Rho-A/Rho kinase- and cGMP/PKA-dependent pathways.
Ang II; heparin; resistance arteries; Rho-A/Rho kinase; vascular tone
Polarization of hepatocytes is manifested by bile canalicular network formation and activation of LKB1 and AMPK, which control cellular energy metabolism. The bile acid, taurocholate, also regulates development of the canalicular network through activation of AMPK. In the present study, we used collagen sandwich hepatocyte cultures from control and liver-specific LKB1 knockout mice to examine the role of LKB1 in trafficking of ABCB11, the canalicular bile acid transporter. In polarized hepatocytes, ABCB11 traffics from Golgi to the apical plasma membrane and endogenously cycles through the rab 11a-myosin Vb recycling endosomal system. LKB1 knockout mice were jaundiced, lost weight and manifested impaired bile canalicular formation and intracellular trafficking of ABCB11, and died within three weeks. Using live cell imaging, fluorescence recovery after photobleaching (FRAP), particle tracking, and biochemistry, we found that LKB1 activity is required for microtubule-dependent trafficking of ABCB11 to the canalicular membrane. In control hepatocytes, ABCB11 trafficking was accelerated by taurocholate and cAMP; however, in LKB1 knockout hepatocytes, ABCB11 trafficking to the apical membrane was greatly reduced and restored only by cAMP, but not taurocholate. cAMP acted through a PKA-mediated pathway which did not activate AMPK. Our studies establish a regulatory role for LKB1 in ABCB11 trafficking to the canalicular membrane, hepatocyte polarization, and canalicular network formation.
Head and neck squamous cell carcinoma (HNSCC) is one of the ten most common cancers with a 50% five-year survival rate, which has remained unchanged for the past three decades. One of the major reasons for the aggressiveness of this cancer is that HNSCCs readily metastasize to cervical lymph nodes that are abundant in the head and neck region. Hence, discovering new molecules controlling the metastatic process as well as understanding their regulation at the molecular level are essential for effective therapeutic strategies.
Rab25 expression level was analyzed in HNSCC tissue microarray. We used a combination of intravital microscopy in live animals and immunofluorescence in an in vitro invasion assay, to study role of Rab25 in tumor cells migration and invasion.
In this study, we identified the small GTPase Rab25 as a key regulator of HNSCC metastasis. We observed that Rab25 is downregulated in HNSCC patients. Next, we determined that re-expression of Rab25 in a metastatic cell line is sufficient to block invasion in a 3D collagen matrix and metastasis to cervical lymph nodes in a mouse model for oral cancer. Specifically, Rab25 affects the organization of F-actin at the cell surface, rather than cell proliferation, apoptosis or tumor angiogenesis.
These findings suggest that Rab25 plays an important role in tumor migration and metastasis, and that understanding its function may lead to the development of new strategies to prevent metastasis in oral cancer patients.
Rab25; metastasis; oral cancer; intravital microscopy; actin cytoskeleton
SET/I2PP2A is a multifunctional protein that is up-regulated in head and neck squamous cell carcinoma (HNSCC). The action of SET in HNSCC tumorigenicity is unknown.
Stable SET knockdown by shRNA (shSET) was established in three HNSCC cell lines: HN12, HN13, and Cal27. Protein expression and phosphorylated protein levels were determined by Western blotting and immunofluorescence, cell migration and invasion were measured by functional analysis, and PP2A activity was determined using a serine/threonine phosphatase assay. A real-time PCR array was used to quantify 84 genes associated with cell motility. Metalloproteinase (MMP) activity was assessed by zymographic and fluorometric assays. HN12shSET xenograft tumors (flank and tongue models) were established in Balb/c nude mice; the xenograft characteristics and cisplatin sensitivity were demonstrated by macroscopic, immunohistochemical, and histological analyses, as well as lymph node metastasis by histology.
The HN12shSET cells displayed reduced ERK1/2 and p53 phosphorylation compared with control. ShSET reduced HN12 cell proliferation and increased the sub-G1 population of HN12 and Cal27 cells. Increased PP2A activity was also associated with shSET. The PCR array indicated up-regulation of three mRNAs in HN12 cells: vimentin, matrix metalloproteinase-9 (MMP9) and non-muscle myosin heavy chain IIB. Reduced E-cadherin and pan-cytokeratin, as well as increased vimentin, were also demonstrated as the result of SET knockdown. These changes were accompanied by an increase in MMP-9 and MMP-2 activities, migration and invasion. The HN12shSET subcutaneous xenograft tumors presented a poorly differentiated phenotype, reduced cell proliferation, and cisplatin sensitivity. An orthotopic xenograft tumor model using the HN12shSET cells displayed increased metastatic potential.
SET accumulation has important actions in HNSCC. As an oncogene, SET promotes cell proliferation, survival, and resistance to cell death by cisplatin in vivo. As a metastasis suppressor, SET regulates invasion, the epithelial mesenchymal transition, and metastasis.
SET; Head and neck cancer; MMP; ERK; EMT; p53; Invasion; Cisplatin; Metastasis
The diagnosis of cervical lymph node metastasis in head and neck squamous cell carcinoma (HNSCC) patients constitutes an essential requirement for clinical staging and treatment selection. However, clinical assessment by physical examination and different imaging modalities, as well as by histological examination of routine lymph node cryosections can miss micrometastases, while false positives may lead to unnecessary elective lymph node neck resections. Here, we explored the feasibility of developing a sensitive assay system for desmoglein 3 (DSG3) as a predictive biomarker for lymph node metastasis in HNSCC.
Materials and Methods
DSG3 expression was determined in multiple general cancer- and HNSCC-tissue microarrays (TMA), in negative and positive HNSCC metastatic cervical lymph nodes, and in a variety of HNSCC and control cell lines. A nanostructured immunoarray system was developed for the ultrasensitive detection of DSG3 in lymph node tissue lysates.
We demonstrate that DSG3 is highly expressed in all HNSCC lesions and their metastatic cervical lymph nodes, but absent in non-invaded lymph nodes. We show that DSG3 can be rapidly detected with high sensitivity using a simple microfluidic immunoarray platform, even in human tissue sections including very few HNSCC invading cells, hence distinguishing between positive and negative lymph nodes.
We provide a proof of principle supporting that ultrasensitive nanostructured assay systems for DSG3 can be exploited to detect micrometastatic HNSCC lesions in lymph nodes, which can improve the diagnosis and guide in the selection of appropriate therapeutic intervention modalities for HNSCC patients.
DSG3; Head and Neck Cancer; Desmosomes; Biomarker; Sentinel Lymph Nodes; Nanosensors
cancer biomarkers; electrochemistry; inkjet-printed arrays; microfluidics; sensors
Neuroblastoma is one of the most genomically heterogeneous childhood malignances studied to date, and the molecular events that occur during the course of the disease are not fully understood. Genomic studies in neuroblastoma have showed only a few recurrent mutations and a low somatic mutation burden. However, none of these studies has examined the mutations arising during the course of disease, nor have they systemically examined the expression of mutant genes. Here we performed genomic analyses on tumors taken during a 3.5 years disease course from a neuroblastoma patient (bone marrow biopsy at diagnosis, adrenal primary tumor taken at surgical resection, and a liver metastasis at autopsy). Whole genome sequencing of the index liver metastasis identified 44 non-synonymous somatic mutations in 42 genes (0.85 mutation/MB) and a large hemizygous deletion in the ATRX gene which has been recently reported in neuroblastoma. Of these 45 somatic alterations, 15 were also detected in the primary tumor and bone marrow biopsy, while the other 30 were unique to the index tumor, indicating accumulation of de novo mutations during therapy. Furthermore, transcriptome sequencing on the 3 tumors demonstrated only 3 out of the 15 commonly mutated genes (LPAR1, GATA2, and NUFIP1) had high level of expression of the mutant alleles, suggesting potential oncogenic driver roles of these mutated genes. Among them, the druggable G-protein coupled receptor LPAR1 was highly expressed in all tumors. Cells expressing the LPAR1 R163W mutant demonstrated a significantly increased motility through elevated Rho signaling, but had no effect on growth. Therefore, this study highlights the need for multiple biopsies and sequencing during progression of a cancer and combinatorial DNA and RNA sequencing approach for systematic identification of expressed driver mutations.
To assess the efficacy of Rapamycin treatment in chemoprevention and chemotherapy of tumorigenesis in a genetically-defined mouse model of head and neck squamous cell carcinoma (HNSCC).
Knockdown of Tgfbr1 and/or Pten using siRNA-mediated RNA interference was carried out in human HNSCC cell lines to analyze molecular changes in the mTOR pathway. Tgfbr1flox/flox; Ptenflox/flox; K14-CreERtam mice were treated with oral gavage of tamoxifen for the conditional deletion of Tgfbr1 and Pten in oral mucosa, resuting in HNSCC (Bian et al 2011). Tgfbr1 and Pten conditonal deletion (2cKO) mice were treated with Rapamycin before or after the onset of HNSCC, and the efficacy of this treatment was assessed by determining tumor burden, longevity, and molecular analysis of the mTOR pathway. Molecular changes observed in human HNSCC cell lines and 2cKO mice were compared to identify key alterations in the mTOR pathway.
Knockdown of Tgfbr1 and/or Pten in human HNSCC cell lines resulted in activation of mTORC1 and increased levels of survivin. Furthermore, we observed similar changes in HNSCC of the 2cKO mouse. In the human HNSCC tissue array, a loss of Tgfbr1 expression correlated with increased survivin levels. Chemopreventive Rapamycin treatment significantly delayed the onset of the HNSCC tumors and prolonged survival in 2cKO mice. Additionally, we also found that Rapamycin had a therapeutic effect on squamous cell carcinomas in these mice. In 2cKO HNSCC tongue tumors, Rapamycin treatment induced apoptosis, inhibited cell proliferation and phosphorylation of Akt and S6, and decreased survivin expression.
These findings indicate that tumorigenesis in 2cKO HNSCC is associated with activation of the Akt/mTOR/survivin pathway, and inhibition of this pathway by Rapamycin treatment successfully ameliorates the onset and progression of tumorigenesis.
TGF-β; Pten; head and neck cancer; mTOR; survivin
We report that K5.Smad7 mice, which express Smad7 transgene by a keratin-5 promoter, were resistant to radiation-induced oral mucositis, a painful oral ulceration. In addition to NF-κB activation known to contribute to oral mucositis, we found activated TGF-β signaling in oral mucositis. Smad7 dampened both pathways to attenuate inflammation, growth inhibition and apoptosis. Additionally, Smad7 promoted oral epithelial migration to close the wound. Further analyses revealed that TGF-β signaling Smads and their co-repressor CtBP1 transcriptionally repressed Rac1, and Smad7 abrogated this repression. Knocking down Rac1 in mouse keratinocytes abrogated Smad7-induced migration. Topically applying Smad7 protein with a cell permeable Tat-tag (Tat-Smad7) to oral mucosa showed preventive and therapeutic effects on radiation-induced oral mucositis in mice. Thus, we have identified novel molecular mechanisms involved in oral mucositis pathogenesis and our data suggest an alternative therapeutic strategy to block multiple pathological processes of oral mucositis.
The integrity of the epidermis and mucosal epithelia is highly dependent on resident self-renewing stem cells, which makes them vulnerable to physical and chemical insults compromising the repopulating capacity of the epithelial stem cell compartment. This is frequently the case in cancer patients receiving radiation or chemotherapy, many of whom develop mucositis, a debilitating condition involving painful and deep mucosal ulcerations. Here, we show that inhibiting the mammalian target of rapamycin (mTOR) with rapamycin increases the clonogenic capacity of primary human oral keratinocytes and their resident self-renewing cells by preventing stem cell senescence. This protective effect of rapamycin is mediated by the increase expression of mitochondrial superoxide dismutase (MnSOD), and the consequent inhibition of ROS formation and oxidative stress. mTOR inhibition also protects from the loss of proliferative basal epithelial stem cells upon ionizing radiation in vivo, thereby preserving the integrity of the oral mucosa and protecting from radiation-induced mucositis.
Head and neck cancer is a devastating disease that afflicts many individuals worldwide. Conventional therapies are successful in only a limited subgroup and often leave the patient with disfigurement and long lasting adverse effects on normal physiological functions. The field is in dire need of new therapies. Oncolytic viral as well as targeted therapies have shown some success in other malignancies and are attractive for the treatment of head and neck cancer. Recently, it has been shown that a subset of head and neck cancers is human papillomavirus (HPV) positive and that this subset of cancers is biologically distinct and more sensitive to chemoradiation therapies although the underlying mechanism is unclear. However, chemoresistance remains a general problem. One candidate mediator of therapeutic response, which is of interest for the targeting of both HPV-positive and -negative tumors is the human DEK proto-oncogene. DEK is upregulated in numerous tumors including head and neck cancers regardless of their HPV status. Depletion of DEK in tumor cells in culture results in sensitivity to genotoxic agents, particularly in rapidly proliferating cells. This suggests that tumors with high DEK protein expression may be correlated with poor clinical response to clastogenic therapies. Targeting molecules such as DEK in combination with new and/or conventional therapies, holds promise for novel future therapeutics for head and neck cancer.