Head And Neck Squamous Cell Carcinoma Cell Survival Research Articles

Effect of short-term fasting on the cisplatin activity in human oral squamous cell carcinoma cell line HN5 and chemotherapy side effects

BackgroundKetogenic interventions like short-term fasting show potential as complementary therapies to enhance the effectiveness of chemotherapy for cancer. However, the specific effects of fasting on head and neck squamous cell carcinoma (HNSCC) cells and healthy oral mucosa cells during these treatments are not well understood. This study investigates whether short-term fasting can differentially impact HNSCC cell survival and viability compared to healthy keratinocytes while undergoing standard chemotherapy regimens.MethodsThis study investigated the effects of fasting on cell viability in HN5 cell line and healthy oral keratinocyte cells. The HN5 cell line, derived from human tongue squamous cell carcinoma, and primary human keratinocytes isolated from the basal layer of gingival epithelium were divided into three groups: (1) control, (2) treated with the standard chemotherapeutic agent cisplatin, and (3) treated with cisplatin under fasting conditions achieved through 48-hour glucose restriction mimicking the blood glucose levels of fasted individuals. Cell proliferation was assessed at 48 and 72 h using the MTT assay, a colorimetric method based on mitochondrial dehydrogenase activity. Flow cytometry analysis with specific apoptosis and necrosis markers distinguished between early and late apoptotic, necrotic, and viable cells.ResultsCell viability in HN5 and healthy keratinocyte cells decreased in cisplatin with low glucose groups compared to cisplatin and control groups. The same results were observed for healthy keratinocyte cells; only a decrease in cell viability in cisplatin groups compared to control groups was observed, which was not statistically significant. Cell apoptosis in HN5 and healthy keratinocyte cells increased in cisplatin with low glucose groups compared to cisplatin and control groups. In healthy keratinocyte cells, the cisplatin with low glucose group showed an impressive increase in necrosis, late apoptosis, and early apoptosis and a significant decrease in live cells compared with other groups.ConclusionThis study revealed that short-term fasting chemotherapy significantly improved HNSCC cell line apoptosis and necrosis.

Identification of splicing factors signature predicting prognosis risk and the mechanistic roles of novel oncogenes in HNSCC

Head and neck squamous cell carcinoma (HNSCC) is the most frequent subtype of head and neck cancer, generally with a poor prognosis and limited therapeutic options due to its highly heterogeneous malignancy. In this study, we screened functional splicing regulatory RNA binding proteins (RBPs) that were closely related with the prognosis of HNSCC patients and showed significant expression differences between HNSCC tumors and normal tissues. Based on this finding, we chose six candidate genes (HNRNPC, ZCRB1, RBM12B, SF3A2, SF3B3, and SRSF11) to generate a prognostic prediction model and validated the accuracy of the prognostic model for predicting patient survival outcomes. We found that the risk score predicted by our model can serve as an independent prognostic predictor. Notably, HNSCC tumors showing higher expression of SF3B3, HNRNPC, or ZCRB1 possessed higher risk scores in the discovered prediction model. The investigation of the underlying mechanism validated that knockdown of SF3B3, HNRNPC, and ZCRB1 separately induced a substantial impairment of HNSCC cell survival. Conversely, overexpression of each of the three genes promoted tumor cellular proliferation. High throughput RNA sequencing analysis revealed that changes in the expression of SF3B3 and HNRNPC remarkably affected alternative splicing of genes related to cell cycle regulation, whereas the depletion of ZCRB1 contributed to aberrant splicing events involving in DNA damage response. In addition, the prognostic prediction model's risk score was demonstrated to be related with the immune infiltration score. Particularly, SF3B3 has a negative correlation with CD8A expression. Therefore, our findings provide promising prognosis predictors and potential therapeutic targets for better treatment efficacy of HNSCC.

Inhibition of USP14 promotes TNFα-induced cell death in head and neck squamous cell carcinoma (HNSCC)

TNFα is a key mediator of immune, chemotherapy and radiotherapy-induced cytotoxicity, but several cancers, including head and neck squamous cell carcinomas (HNSCC), display resistance to TNFα due to activation of the canonical NFκB pro-survival pathway. However, direct targeting of this pathway is associated with significant toxicity; thus, it is vital to identify novel mechanism(s) contributing to NFκB activation and TNFα resistance in cancer cells. Here, we demonstrate that the expression of proteasome-associated deubiquitinase USP14 is significantly increased in HNSCC and correlates with worse progression free survival in Human Papillomavirus (HPV)- HNSCC. Inhibition or depletion of USP14 inhibited the proliferation and survival of HNSCC cells. Further, USP14 inhibition reduced both basal and TNFα-inducible NFκB activity, NFκB-dependent gene expression and the nuclear translocation of the NFκB subunit RELA. Mechanistically, USP14 bound to both RELA and IκBα and reduced IκBα K48-ubiquitination leading to the degradation of IκBα, a critical inhibitor of the canonical NFκB pathway. Furthermore, we demonstrated that b-AP15, an inhibitor of USP14 and UCHL5, sensitized HNSCC cells to TNFα-mediated cell death, as well as radiation-induced cell death in vitro. Finally, b-AP15 delayed tumor growth and enhanced survival, both as a monotherapy and in combination with radiation, in HNSCC tumor xenograft models in vivo, which could be significantly attenuated by TNFα depletion. These data offer new insights into the activation of NFκB signaling in HNSCC and demonstrate that small molecule inhibitors targeting the ubiquitin pathway warrant further investigation as a novel therapeutic avenue to sensitize these cancers to TNFα- and radiation-induced cytotoxicity.

Blocking EREG/GPX4 Sensitizes Head and Neck Cancer to Cetuximab through Ferroptosis Induction

(1) Background: Epiregulin (EREG) is a ligand of EGFR and ErB4 involved in the development and the progression of various cancers including head and neck squamous cell carcinoma (HNSCC). Its overexpression in HNSCC is correlated with short overall survival and progression-free survival but predictive of tumors responding to anti-EGFR therapies. Besides tumor cells, macrophages and cancer-associated fibroblasts shed EREG in the tumor microenvironment to support tumor progression and to promote therapy resistance. Although EREG seems to be an interesting therapeutic target, no study has been conducted so far on the consequences of EREG invalidation regarding the behavior and response of HNSCC to anti-EGFR therapies and, more specifically, to cetuximab (CTX); (2) Methods: EREG was silenced in various HNSCC cell lines. The resulting phenotype (growth, clonogenic survival, apoptosis, metabolism, ferroptosis) was assessed in the absence or presence of CTX. The data were confirmed in patient-derived tumoroids; (3) Results: Here, we show that EREG invalidation sensitizes cells to CTX. This is illustrated by the reduction in cell survival, the alteration of cell metabolism associated with mitochondrial dysfunction and the initiation of ferroptosis characterized by lipid peroxidation, iron accumulation and the loss of GPX4. Combining ferroptosis inducers (RSL3 and metformin) with CTX drastically reduces the survival of HNSCC cells but also HNSCC patient-derived tumoroids; (4) Conclusions: The loss of EREG might be considered in clinical settings as a predictive biomarker for patients that might undergo ferroptosis in response to CTX and that might benefit the most from the combination of ferroptosis inducers and CTX.

Irradiated fibroblasts increase interleukin-6 expression and induce migration of head and neck squamous cell carcinoma.

BackgroundCytotoxic effects of radiation play an important role in the treatment of head and neck cancer. However, irradiation is known to lead to the migration of various cancer cells, including those of head and neck cancer. Recently, fibroblasts in the cancer microenvironment have been reported to be involved in this mechanism. Nevertheless, the mechanism underlying migration of head and neck cancer cells remains unclear. Herein, we aimed to elucidate this migration mechanism induced by irradiation in terms of the interaction of head and neck cancer cells with fibroblasts.MethodsWe used the head and neck squamous cell carcinoma (HNSCC) cell lines SAS and FaDu as well as fibroblast cell lines. These cells were irradiated and their viability was compared. In fibroblasts, changes in interleukin-6 (IL-6) secretion caused by irradiation were measured by enzyme-linked immunosorbent assay (ELISA). The cell migration ability of cancer cells was evaluated via a migration assay using a semipermeable membrane. HNSCC cells were cocultured with irradiated and nonirradiated fibroblasts, and their migration ability under each condition was compared. We also examined the effect of IL-6 on the migration of HNSCC cells. Furthermore, to investigate the effect of fibroblast-derived IL-6 on the migration ability of HNSCC cells, we conducted a coculture study using IL-6 neutralizing antibody.ResultsIrradiation reduced the survival of HNSCC cells, whereas fibroblasts were resistant to irradiation. Irradiation also increased IL-6 secretion by fibroblasts. Migration of HNSCC cells was enhanced by coculture with fibroblasts and further enhanced by coculture with irradiated fibroblasts. We also confirmed that the migration of HNSCC cells was induced by IL-6. The enhanced migration of cancer cells caused by coculturing with fibroblasts was canceled by the IL-6 neutralizing antibody.ConclusionThese results show that fibroblasts survive irradiation and induce the migration ability of HNSCC cells through increased secretion of IL-6.

Identification of CCT3 as a prognostic factor and correlates with cell survival and invasion of head and neck squamous cell carcinoma.

Background: Recurrent locally advanced or metastatic head and neck squamous cell carcinoma (HNSCC) is associated with dismal prognosis because of its highly invasive behavior and resistance to conventional intensive chemotherapy. The identification of effective markers for early diagnosis and prognosis is important for reducing mortality and ensuring that therapy for HNSCC is effective. Chaperonin-containing TCP-1 3 (CCT3) folds cancer-related proteins to control carcinogenesis. The prognostic value and growth association of CCT3 and HNSCC remain unknown.Methods: The GEO, Oncomine and UALCAN databases were used to examine CCT3 expression in HNSCC. A few clinical HNSCC samples with normal tissues were used to detect CCT3 expression by using immunohistochemistry method. The TCGA-HNSC dataset was used to evaluate the association between expression of CCT3 and prognosis. The molecular mechanism was investigated with gene set enrichment analysis (GSEA). CCK-8 and wound healing assays were used to detect cell growth and invasion of HNSCC, respectively.Results: CCT3 expression was significantly up-regulated in HNSCC in both mRNA and protein levels. In addition, up-regulated CCT3 expression was associated with various clinicopathological parameters. High expression of CCT3 was significantly correlated with inferior survival of HNSCC patients. Knockdown of CCT3 significantly inhibited cell growth and invasion of HNSCC cell lines. GSEA analysis indicated that CCT3 was closely correlated with tumor-related signaling pathways and HNSCC cell survival.Conclusion: Our findings suggest that CCT3 is a biomarker of poor prognosis and related to the process of HNSCC.

Palbociclib Renders Human Papilloma Virus-Negative Head and Neck Squamous Cell Carcinoma Vulnerable to the Senolytic Agent Navitoclax.

We demonstrate that inhibition of cyclin-dependent kinases 4/6 (CDK4/6) leads to senescence in human papillomavirus (HPV)-negative (-) head and neck squamous cell carcinoma (HNSCC), but not in HPV-positive (+) HNSCC. The BCL-2 family inhibitor, navitoclax, has been shown to eliminate senescent cells effectively. We evaluated the efficacy of combining palbociclib and navitoclax in HPV- HNSCC. Three HPV- HNSCC cell lines (CAL27, HN31, and PCI15B) and three HPV+ HNSCC cell lines (UPCI-SCC-090, UPCI-SCC-154, and UM-SCC-47) were treated with palbociclib. Treatment drove reduced expression of phosphorylated Rb (p-Rb) and phenotypic evidence of senescence in all HPV- cell lines, whereas HPV+ cell lines did not display a consistent response by Rb or p-Rb and did not exhibit morphologic changes of senescence in response to palbociclib. In addition, treatment of HPV- cells with palbociclib increased both β-galactosidase protein expression and BCL-xL protein expression compared with untreated controls in HPV- cells. Co-expression of β-galactosidase and BCL-xL occurred consistently, indicating elevated BCL-xL expression in senescent cells. Combining palbociclib with navitoclax led to decreased HPV- HNSCC cell survival and led to increased apoptosis levels in HPV- cell lines compared with each agent given alone. IMPLICATIONS: This work exploits a key genomic hallmark of HPV- HNSCC (CDKN2A disruption) using palbociclib to induce BCL-xL-dependent senescence, which subsequently causes the cancer cells to be vulnerable to the senolytic agent, navitoclax.

Targeting DNA Double-Strand Break Repair Enhances Radiosensitivity of HPV-Positive and HPV-Negative Head and Neck Squamous Cell Carcinoma to Photons and Protons.

The response of head and neck squamous cell carcinoma (HNSCC) to radiotherapy depends on human papillomavirus type 16 (HPV) status, and where improved outcome and survival is observed in HPV-positive disease. However, strategies to further radiosensitise the tumours, particularly relatively radioresistant HPV-negative HNSCC, are actively being sought. The impact of targeting the major protein kinases involved in the signaling of DNA double-strand break (DSB) repair, namely ataxia telangiectasia-mutated (ATM), ataxia telangiectasia and Rad3-related (ATR), and the catalytic subunit of DNA-dependent protein kinase (DNA-Pkcs), on the radiosensitisation of HNSCC cells was examined. The response to both conventional photon radiotherapy, but also proton beam therapy, was analysed by clonogenic assays and 3D spheroid growth. We observed that inhibition of ATM, ATR, and particularly DNA-Pkcs, caused a significant reduction in HNSCC cell survival post-irradiation with both photons and protons, with less of an impact on the most radiosensitive HPV-positive cell line. The inhibition of DNA-Pkcs and, to a lesser extent ATM, in combination with radiation was also more effective at inhibiting the growth of 3D spheroids derived from relatively radioresistant HPV-negative HNSCC. Similar effects of the inhibitors were observed comparing photon and proton irradiation, demonstrating the potential for targeting DSB repair as an effective combination treatment for HNSCC.

Tumor necrosis factor-α triggers opposing signals in head and neck squamous cell carcinoma and induces apoptosis via mitochondrial- and non-mitochondrial-dependent pathways.

Head and neck squamous cell carcinoma (HNSCC) remains one of the most common malignancies worldwide. Although the treatment outcomes of HNSCC have improved in recent years, the prognosis of patients with advanced-stage disease remains poor. Current treatment strategies for HNSCC include surgery as a primary therapy, while radio-, chemo-, and biotherapeutics can be applied as second-line therapy. Although tumor necrosis factor-α (TNF-α) is a potent tumor suppressor cytokine, the stimulation of opposing signals impairs its clinical utility as an anticancer agent. The aim of this study was to elucidate the mechanisms regulating TNF-α‑induced opposing signals and their biological consequences in HNSCC cell lines. We determined the molecular mechanisms of TNF-α-induced opposing signals in HNSCC cells. Our invitro analysis indicated that one of these signals triggers apoptosis, while the other induces both apoptosis and cell survival. The TNF-α-induced survival of HNSCC cells is mediated by the TNF receptor-associated factor2 (TRAF2)/nuclear factor(NF)-κB-dependent pathway, while TNF-α-induced apoptosis is mediated by mitochondrial and non-mitochondrial-dependent mechanisms through FADD-caspase-8-caspase-3 and ASK-JNK-p53-Noxa pathways. The localization of Noxa protein to both the mitochondria and endoplasmic reticulum(ER) was found to cause mitochondrial dysregulation and ER stress, respectively. Using inhibitory experiments, we demonstrated that the FADD‑caspase-8‑caspase-3 pathway, together with mitochondrial dysregulation and ER stress-dependent pathways, are essential for the modulation of apoptosis, and the NF-κB pathway is essential for the modulation of anti-apoptotic effects/cell survival during the exposure of HNSCC cells to TNF-α. Our data provide insight into the mechanisms of TNF-α-induced opposing signals in HNSCC cells and may further help in the development of novel therapeutic approaches with which to minimize the systemic toxicity of TNF-α.

COTI-2, A Novel Thiosemicarbazone Derivative, Exhibits Antitumor Activity in HNSCC through p53-dependent and -independent Mechanisms.

TP53 mutations are highly prevalent in head and neck squamous cell carcinoma (HNSCC) and associated with increased resistance to conventional treatment primarily consisting of chemotherapy and radiation. Restoration of wild-type p53 function in TP53-mutant cancer cells represents an attractive therapeutic approach and has been explored in recent years. In this study, the efficacy of a putative p53 reactivator called COTI-2 was evaluated in HNSCC cell lines with different TP53 status.Experimental Design: Clonogenic survival assays and an orthotopic mouse model of oral cancer were used to examine in vitro and in vivo sensitivity of HNSCC cell lines with either wild-type, null, or mutant TP53 to COTI-2 alone, and in combination with cisplatin and/or radiation. Western blotting, cell cycle, live-cell imaging, RNA sequencing, reverse-phase protein array, chromatin immunoprecipitation, and apoptosis analyses were performed to dissect molecular mechanisms. COTI-2 decreased clonogenic survival of HNSCC cells and potentiated response to cisplatin and/or radiation in vitro and in vivo irrespective of TP53 status. Mechanistically, COTI-2 normalized wild-type p53 target gene expression and restored DNA-binding properties to the p53-mutant protein in HNSCC. In addition, COTI-2 induced DNA damage and replication stress responses leading to apoptosis and/or senescence. Furthermore, COTI-2 lead to activation of AMPK and inhibition of the mTOR pathways in vitro in HNSCC cells. COTI-2 inhibits tumor growth in vitro and in vivo in HNSCC likely through p53-dependent and p53-independent mechanisms. Combination of COTI-2 with cisplatin or radiation may be highly relevant in treating patients with HNSCC harboring TP53 mutations.

PO-122 Synemin is a novel co-regulator of non-homologous end joining in head and neck cancer cells

Introduction Cancer therapy resistance is one of the major obstacles for higher cure rates. Novel key players of the resistome are focal adhesion proteins (FAPs). As FAPs are critically involved in DNA repair, we here characterise the yet unknown function of the FAP and intermediate filament protein Synemin (SYN) as a novel DNA repair regulator and potential cancer drug target in head and neck squamous cell carcinoma (HNSCC). Material and methods Our novel 3D High Throughput esiRNA Screen (3DHTesiRNAs) using laminin-rich extracellular matrix (lrECM) was conducted to measure radiation-induced residual DNA double strand breaks (DSBs; foci assay) and clonogenic radiation survival in UTSCC15-pEGFP-53BP1 cells. Validations were performed in 10 additional HNSCC cell lines in 3D lrECM. Upon SYN depletion, DSB repair reporter assays for non-homologous end joining (NHEJ) and homologous recombination (HR) as well as Western Blotting for protein expression and phosphorylation were carried out. SYN depleted cells with and without irradiation were analysed for kinase activity profiling (PamGene) and protein interactome determination using a sequential immunoprecipitation/mass spectrometry approach. Results and discussions Among the targets found in the 3DHTesiRNAs, SYN turned out as one of the top FAP candidate determinants of HNSCC cell survival. SYN silencing radiosensitized HNSCC cells, while its exogenous overexpression induced radioprotection. We found an increased SYN/chromatin interaction and a marked perinuclear SYN accumulation post irradiation. Intriguingly, SYN depletion elicited a 40% reduction in NHEJ activity without affecting HR or alt-EJ. In line, ATM, DNA-PKcs and c-Abl phosphorylation as well as Ku70 expression strongly declined in SYN depleted and irradiated cells relative to controls and, in contrast, to the rescue of these protein modifications by SYN overexpression. Single, double and triple depletion of SYN, DNA-PKcs and c-Abl resulted in similar radiosensitization and DSB levels as observed for SYN only, suggesting its upstream role. In the kinome analysis we observed variable changes in the serine/threonine kinases, in contrast to the tyrosine kinases with a pronounce reduced kinase activity after SYN silencing. Conclusion Our data suggest the intermediate filament SYN as a new important determinant of DNA repair, tyrosine kinome and radioresistance of HNSCC cells. These observations further support the notion that DNA repair is controlled by cooperative interactions between nuclear and cytoplasmic proteins.

Targeting aldehyde dehydrogenase activity in head and neck squamous cell carcinoma with a novel small molecule inhibitor.

Chemoresistant cancer cells express high levels of aldehyde dehydrogenases (ALDHs), particularly in head and neck squamous cell carcinoma (HNSCC). The ALDH family of enzymes detoxify both exogenous and endogenous aldehydes. Since many chemotherapeutic agents, such as cisplatin, result in the generation of cytotoxic aldehydes and oxidative stress, we hypothesized that cells expressing high levels of ALDH may be more chemoresistant due to their increased detoxifying capacity and that inhibitors of ALDHs may sensitize them to these drugs. Here, we show that overall ALDH activity is increased with cisplatin treatment of HNSCC and that ALDH3A1 protein expression is particularly enriched in cells treated with cisplatin. Activation of ALDH3A1 by a small molecule activator (Alda-89) increased survival of HNSCC cells treated with cisplatin. Conversely, treatment with a novel small molecule ALDH inhibitor (Aldi-6) resulted in a marked decrease in cell viability, and the combination of Aldi-6 and cisplatin resulted in a more pronounced reduction of cell viability and a greater reduction in tumor burden in vivo than what was observed with cisplatin alone. These data indicate that ALDH3A1 contributes to cisplatin resistance in HNSCC and that the targeting of ALDH, specifically, ALDH3A1, appears to be a promising strategy in this disease.

A novel read-through transcript JMJD7-PLA2G4B regulates head and neck squamous cell carcinoma cell proliferation and survival

Recent findings on the existence of oncogenic fusion genes in a wide array of solid tumors, including head and neck squamous cell carcinoma (HNSCC), suggests that fusion genes have become attractive targets for cancer diagnosis and treatment. In this study, we showed for the first time that a read-through fusion gene JMJD7-PLA2G4B is presented in HNSCC, splicing neighboring jumonji domain containing 7 (JMJD7) and phospholipase A2, group IVB (PLA2G4B) genes together. Ablation of JMJD7-PLA2G4B significantly inhibited proliferation of HNSCC cells by promoting G1 cell cycle arrest and increased starvation-induced cell death compared to JMJD7-only knockdown HNSCC cells. Mechanistically, we found that JMJD7-PLA2G4B modulates phosphorylation of Protein Kinase B (AKT) to promote HNSCC cell survival. Moreover, JMJD7-PLA2G4B also regulated an E3 ligase S-phase kinase-associated protein 2 (SKP2) to control the cell cycle progression from G1 phase to S phase by inhibiting Cyclin-dependent kinase inhibitor 1 (p21) and 1B (p27) expression. Our study provides novel insights into the oncogenic control of JMJD7-PLA2G4B in HNSCC cell proliferation and survival, and suggests that JMJD7-PLA2G4B may serve as an important therapeutic target and prognostic marker for HNSCC development and progression.

Spheroid Culture of Head and Neck Cancer Cells Reveals an Important Role of EGFR Signalling in Anchorage Independent Survival.

In solid tumours millions of cells are shed into the blood circulation each day. Only a subset of these circulating tumour cells (CTCs) survive, many of them presumable because of their potential to form multi-cellular clusters also named spheroids. Tumour cells within these spheroids are protected from anoikis, which allows them to metastasize to distant organs or re-seed at the primary site. We used spheroid cultures of head and neck squamous cell carcinoma (HNSCC) cell lines as a model for such CTC clusters for determining the role of the epidermal growth factor receptor (EGFR) in cluster formation ability and cell survival after detachment from the extra-cellular matrix. The HNSCC cell lines FaDu, SCC-9 and UT-SCC-9 (UT-SCC-9P) as well as its cetuximab (CTX)-resistant sub-clone (UT-SCC-9R) were forced to grow in an anchorage-independent manner by coating culture dishes with the anti-adhesive polymer poly-2-hydroxyethylmethacrylate (poly-HEMA). The extent of apoptosis, clonogenic survival and EGFR signalling under such culture conditions was evaluated. The potential of spheroid formation in suspension culture was found to be positively correlated with the proliferation rate of HNSCC cell lines as well as their basal EGFR expression levels. CTX and gefitinib blocked, whereas the addition of EGFR ligands promoted anchorage-independent cell survival and spheroid formation. Increased spheroid formation and growth were associated with persistent activation of EGFR and its downstream signalling component (MAPK/ERK). Importantly, HNSCC cells derived from spheroid cultures retained their clonogenic potential in the absence of cell-matrix contact. Addition of CTX under these conditions strongly inhibited colony formation in CTX-sensitive cell lines but not their resistant subclones. Altogether, EGFR activation was identified as crucial factor for anchorage-independent survival of HNSCC cells. Targeting EGFR in CTC cluster formation might represent an attractive anti-metastatic treatment approach in HNSCC.

Drug-induced RAF dimerization is independent of RAS mutation status and does not lead to universal MEK dependence for cell survival in head and neck cancers.

Treatments for recurrent or metastatic head and neck squamous cell carcinoma (HNSCC) have limited efficacy. One potential therapeutic target for HNSCC is the RAS/RAF/MEK/ERK cascade, which is one of the major signaling pathways for HNSCC cell survival. In HNSCC, RAS can be activated either by HRAS mutation or by upstream signaling. The ABL inhibitor nilotinib acts as a weak RAF inhibitor that induces RAF dimerization and subsequent activation of MEK/ERK in other cancer cell lines with activated RAS, leading to an unexpected dependence on MEK/ERK for cell survival. We hypothesized that nilotinib and the MEK inhibitor MEK162 would be synergistic in HNSCC cell lines owing to the frequent activation of RAS. We treated HNSCC cell lines with nilotinib and performed immunoblotting and cell-viability experiments. We used an orthotopic mouse model to assess synergistic effects in vivo. Nilotinib induced significant BRAF-CRAF heterodimerization and ERK activation irrespective of RAS mutation status. In cell-viability assays, nilotinib synergized with MEK162. MEK162 alone induced G1 arrest that was minimally enhanced by nilotinib. In the mouse model, treatment with MEK162 alone or combined with nilotinib led to tumor growth inhibition. In HNSCC, nilotinib-induced RAF dimerization is independent of RAS mutation status, but this dimerization does not lead to MEK dependence for cell survival in all HNSCC cell lines. MEK inhibition alone leads to decreased proliferation both in vitro and in vivo. Although nilotinib has some synergistic effects with MEK162, other agents may be more effective against HNSCC when combined with MEK162.

Carfilzomib and ONX 0912 Inhibit Cell Survival and Tumor Growth of Head and Neck Cancer and Their Activities Are Enhanced by Suppression of Mcl-1 or Autophagy

Carfilzomib is a selective, irreversible inhibitor of the chymotrypsin-like activity of the proteasome and is undergoing clinical evaluation in myeloma. ONX 0912 (oprozomib) is an orally bioavailable derivative. The activities of carfilzomib and ONX 0912 against solid tumor malignancies are less well understood. We investigated the impact and mechanisms of action of carfilzomib and ONX 0912 in preclinical models of head and neck squamous cell carcinoma (HNSCC). The effects of carfilzomib and ONX 0912 on HNSCC cell survival and xenograft tumor growth were evaluated. The impact and mechanisms of both agents on apoptosis and autophagy induction were also investigated. The contribution of the unfolded protein response (UPR) to autophagy induction and the role of autophagy in attenuating HNSCC cell death were determined. Carfilzomib and ONX 0912 potently induced apoptosis in HNSCC cell lines via upregulation of pro-apoptotic Bik. Upregulation of Mcl-1 by these agents served to dampen their efficacies. Carfilzomib and ONX 0912 also induced autophagy, mediated, in part, by activation of the UPR pathway involving upregulation of ATF4 transcription factor. Autophagy induction served a prosurvival role. Oral administration of ONX 0912 inhibited the growth of HNSCC xenograft tumors in a dose-dependent manner. These results show that carfilzomib and ONX 0912 are potently active against HNSCC cells, and the activities of these agents can be enhanced via suppression of Mcl-1 or inhibition of autophagy. Oral ONX 0912 exhibits in vivo activity against HNSCC tumors and may represent a useful therapeutic agent for this malignancy.

P63 mediates survival in squamous cell carcinoma by suppression of p73-dependent apoptosis

We demonstrate that deltaNp63alpha is an essential survival factor in head and neck squamous cell carcinoma (HNSCC) through its ability to suppress p73-dependent apoptosis. Inhibition of endogenous p63 expression by RNAi induces apoptosis selectively in HNSCC cells that overexpress deltaNp63alpha. Knockdown of p63 induces the proapoptotic bcl-2 family members Puma and Noxa, and both their induction and subsequent cell death are p53 independent but require transactivating isoforms of p73. Inhibition of p73-dependent transcription by deltaNp63alpha involves both direct promoter binding and physical interaction with p73. In HNSCC cells lacking endogenous deltaNp63alpha expression, bcl-2 is instead upregulated and can suppress p73-mediated death. Together, these data define a pathway whereby deltaNp63alpha promotes survival in squamous epithelial malignancy by repressing a p73-dependent proapoptotic transcriptional program.