Genotyping of 73 UM-SCC head and neck squamous cell carcinoma cell lines

Targeted radiosensitization of ETS fusion-positive prostate cancer through PARP1 inhibition

ETS gene fusions, which result in overexpression of an ETS transcription factor, are considered driving mutations in approximately half of all prostate cancers. Dysregulation of ETS transcription factors is also known to exist in Ewing's sarcoma, breast cancer, and acute lymphoblastic leukemia. We previously discovered that ERG, the predominant ETS family member in prostate cancer, interacts with the DNA damage response protein poly (ADP-ribose) polymerase 1 (PARP1) in human prostate cancer specimens. Therefore, we hypothesized that the ERG-PARP1 interaction may confer radiation resistance by increasing DNA repair efficiency and that this radio-resistance could be reversed through PARP1 inhibition. Using lentiviral approaches, we established isogenic models of ERG overexpression in PC3 and DU145 prostate cancer cell lines. In both cell lines, ERG overexpression increased clonogenic survival following radiation by 1.25 (±0.07) fold (mean ± SEM) and also resulted in increased PARP1 activity. PARP1 inhibition with olaparib preferentially radiosensitized ERG-positive cells by a factor of 1.52 (±0.03) relative to ERG-negative cells (P < .05). Neutral and alkaline COMET assays and immunofluorescence microscopy assessing γ-H2AX foci showed increased short- and long-term efficiencies of DNA repair, respectively, following radiation that was preferentially reversed by PARP1 inhibition. These findings were verified in an in vivo xenograft model. Our findings demonstrate that ERG overexpression confers radiation resistance through increased efficiency of DNA repair following radiation that can be reversed through inhibition of PARP1. These results motivate the use of PARP1 inhibitors as radiosensitizers in patients with localized ETS fusion-positive cancers.

Regulation of HPV16 E6 and MCL1 by SF3B1 inhibitor in head and neck cancer cells

ABT-737 inhibits the anti-apoptotic proteins B-cell lymphoma 2 (BCL-2) and BCL-X_L. Meayamycin B switches the splicing pattern of myeloid cell leukemia factor 1 (MCL1) pre-mRNA. Specifically, inhibition of splicing factor 3B subunit 1 (SF3B1) with meayamycin B promotes the generation of the proapoptotic, short splicing variant (MCL1-S) and diminishes the antiapoptotic, long variant (MCL1-L). This action was previously associated with the cytotoxicity of meayamycin B in non-small cell lung carcinoma cell lines. ABT-737 induced apoptosis in response to an ablation of MCL1-L by meayamycin B. In this study, we further exploited this synergistic combination in head and neck squamous cell carcinoma (HNSCC), up to 90% of which overexpress MCL1 and BCL-X_L. In a panel of seven HNSCC cell lines, the combination of meayamycin B and ABT-737 rapidly triggered a Bax/Bak-mediated apoptosis that overcame the resistance from HPV16-positive HNSCC against each agent alone. Both RT-PCR and Western blotting showed that meayamycin B up-regulated MCL1-S and down-regulated MCL1-L. Significantly, we discovered that SF3B1 was involved in the splicing of oncogenic HPV16 E6 to produce non-oncogenic HPV16 E6*, indicating that SF3B1 may inhibit HPV16-induced tumorigenesis.

TRIP13 promotes error-prone nonhomologous end joining and induces chemoresistance in head and neck cancer

Head and neck cancer (SCCHN) is a common, aggressive, treatment-resistant cancer with a high recurrence rate and mortality, but the mechanism of treatment-resistance remains unclear. Here we describe a mechanism where the AAA-ATPase TRIP13 promotes treatment-resistance. Overexpression of TRIP13 in non-malignant cells results in malignant transformation. High expression of TRIP13 in SCCHN leads to aggressive, treatment-resistant tumors and enhanced repair of DNA damage. Using mass spectrometry, we identify DNA-PKcs complex proteins that mediate non homologous end joining (NHEJ), as TRIP13 binding partners. Using repair-deficient reporter systems, we show that TRIP13 promotes NHEJ, even when homologous recombination is intact. Importantly, overexpression of TRIP13 sensitizes SCCHN to an inhibitor of DNA-PKcs. Thus, this study defines a new mechanism of treatment resistance in SCCHN and underscores the importance of targeting NHEJ to overcome treatment failure in SCCHN and potentially in other cancers that overexpress TRIP13.

Development and characterization of salivary adenoid cystic carcinoma cell line

OBJECTIVE

To develop in vitro adenoid cystic carcinoma cell line as a surrogate for functional studies.

MATERIALS AND METHODS

Cells obtained from a primary ACC of the base of tongue were cultivated in vitro and immortalized with h-TERT. Morphologic, cytogenetic and functional studies were performed.

RESULTS

Tumor cells were verified by positive reactions to keratin and smooth muscle actin and phenotypic cellular and nuclear features. In-vitro cell growth and colony formation assay supported their tumor nature.

CONCLUSION

We authenticated an ACC cell line with hybrid epithelial-myoepithelial feature as a resource for functional experimentation.

The cytoplasmic domain of N-cadherin modulates MMP‑9 induction in oral squamous carcinoma cells

Oral squamous carcinoma is the sixth most common cancer worldwide, and one of the most common cancers in developing countries. Regional and distant metastases comprise the majority of cases at initial diagnosis and correlate with poor patient outcomes. Oral epithelia is one of many tissue types to exhibit a cadherin switch during tumor progression, in which endogenous cell adhesion proteins, such as E-cadherin, give way to those of mesenchymal origin. The mesenchymal cell adhesion protein N-cadherin is found at the invading front of oral squamous carcinomas and has been strongly correlated with poor patient prognosis. The goal of the present study was to elucidate the mechanism by which N-cadherin may increase extracellular matrix-associated proteolytic activity to facilitate invasiveness in oral tumor development. The overexpression of N-cadherin in two oral squamous carcinoma cell lines increased motility, invasive capacity and synthesis of matrix metalloproteinase-9 (MMP-9) in a manner that was independent of E-cadherin downregulation. The use of EN and NE chimeric cadherin molecules with reciprocally substituted cytoplasmic domains revealed that optimal induction of MMP-9 synthesis required the cytoplasmic region, but not the extracellular region, of N-cadherin. Utilizing an N-cadherin mutant with impaired p120 binding ability, we found that such mutation resulted in a 4-fold decrease in motility compared to wild-type N-cadherin, but did not affect either MMP-9 expression or motility-normalized invasion. Overexpression of wild-type N-cadherin produced a 27-fold increase in the transcriptional activity of β-catenin, concomitant with increases in MMP-9 transcription. These results suggest that N-cadherin may promote motility and invasiveness through distinct mechanisms, and that β-catenin may be an integral mediator of N-cadherin-dependent invasive signaling in oral epithelia.

Identification of chemoresistant factors by protein expression analysis with iTRAQ for head and neck carcinoma

Background:

Cisplatin and other anticancer drugs are important in the treatment of head and neck squamous cell carcinoma; however, some tumours develop drug resistance. If chemoresistance could be determined before treatment, unnecessary drug administration would be avoided. Here, we investigated chemoresistance factors by comprehensive analyses at the protein level.

Methods:

Four human carcinoma cell lines were used: cisplatin-sensitive UM-SCC-23, UM-SCC-23-CDDPR with acquired cisplatin resistance, naturally cisplatin-resistant UM-SCC-81B, and UM-SCC-23/WR with acquired 5-fluorouracil resistance. Extracted proteins were labelled with iTRAQ and analysed by tandem mass spectrometry to identify resistance. Protein expression was confirmed by western blotting and functional analysis was carried out using siRNA.

Results:

Thirteen multiple-drug resistance proteins were identified, as well as seven proteins with specific resistance to cisplatin, including α-enolase. Differential expression of these proteins in cisplatin-resistant and -sensitive cell lines was confirmed by western blotting. Functional analysis for α-enolase by siRNA showed that cisplatin sensitivity significantly was increased in UM-SCC-81B and slightly in UM-SCC-23-CDDPR but not in UM-SCC-23/WR cells.

Conclusions:

We identified proteins thought to mediate anticancer drug resistance using recent proteome technology and identified α-enolase as a true cisplatin chemoresistance factor. Such proteins could be used as biomarkers for anticancer agent resistance and as targets of cancer therapy.

Glucose-regulated protein 78 (Grp78) confers chemoresistance to tumor endothelial cells under acidic stress

OBJECTIVES

This study was designed to investigate the activation of the unfolded protein response (UPR) in tumor associated endothelial cells (TECs) and its association with chemoresistance during acidic pH stress.

MATERIALS AND METHODS

Endothelial cells from human oral squamous cell carcinomas (OSCC) were excised by laser capture microdissection (LCM) followed by analysis of UPR markers (Grp78, ATF4 and CHOP) using quantitative PCR. Grp78 expression was also determined by immunostaining. Acidic stress was induced in primary human dermal microvascular endothelial cells (HDMECs) by treatment with conditioned medium (CM) from tumor cells grown under hypoxic conditions or by adjusting medium pH to 6.4 or 7.0 using lactic acid or hydrochloric acid (HCl). HDMEC resistance to the anti-angiogenic drug Sunitinib was assessed with SRB assay.

RESULTS

UPR markers, Grp78, ATF4 and CHOP were significantly upregulated in TECs from OSCC compared to HDMECs. HDMECs cultured in acidic CM (pH 6.0-6.4) showed increased expression of the UPR markers. However, severe acidosis led to marked cell death in HDMECs. Alternatively, HDMECs were able to adapt when exposed to chronic acidosis at pH 7.0 for 7 days, with concomittant increase in Grp78 expression. Chronic acidosis also confers drug resistance to HDMECs against Sunitinib. Knockdown of Grp78 using shRNA resensitizes HDMECs to drug treatment.

CONCLUSIONS

UPR induction in ECs under acidic pH conditions is related to chemoresistance and may contribute to therapeutic failures in response to chemotherapy. Targeting Grp78, the key component of the UPR pathway, may provide a promising approach to overcome ECs resistance in cancer therapy.

Increased growth-inhibitory and cytotoxic activity of arsenic trioxide in head and neck carcinoma cells with functional p53 deficiency and resistance to EGFR blockade

BACKGROUND AND PURPOSE

Mutations in the p53 gene are frequently observed in squamous cell carcinoma of the head and neck region (SCCHN) and have been associated with drug resistance. The potential of arsenic trioxide (ATO) for treatment of p53-deficient tumor cells and those with acquired resistance to cisplatin and cetuximab was determined.

MATERIAL AND METHODS

In a panel of 10 SCCHN cell lines expressing either wildtype p53, mutated p53 or which lacked p53 by deletion the interference of p53 deficiency with the growth-inhibitory and radiosensitizing potential of ATO was determined. The causal relationship between p53 deficiency and ATO sensitivity was evaluated by reconstitution of wildtype p53 in p53-deficient SCCHN cells. Interference of ATO treatment with cell cycle, DNA repair and apoptosis and its efficacy in cells with acquired resistance to cisplatin and cetuximab was evaluated.

RESULTS

Functional rather than structural defects in the p53 gene predisposed tumor cells to increased sensitivity to ATO. Reconstitution of wt p53 in p53-deficient SCCHN cells rendered them less sensitive to ATO treatment. Combination of ATO with irradiation inhibited clonogenic growth in an additive manner. The inhibitory effect of ATO in p53-deficient tumor cells was mainly associated with DNA damage, G2/M arrest, upregulation of TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) receptors and apoptosis. Increased activity of ATO was observed in cetuximab-resistant SCCHN cells whereas cisplatin resistance was associated with cross-resistance to ATO.

CONCLUSIONS

Addition of ATO to treatment regimens for p53-deficient SCCHN and tumor recurrence after cetuximab-containing regimens might represent an attractive strategy in SCCHN.

Establishment and genetic characterization of six unique tumor cell lines as preclinical models for sinonasal squamous cell carcinoma

Sinonasal squamous cell carcinomas (SCC) are rare tumors, etiologically related to occupational exposure to wood and leather dust. In spite of surgical and radiotherapeutic advances, the 5 year survival is still 30–50%. Therefore, alternative treatment options are needed. We report the establishment and characterization of six unique human sinonasal SCC cell lines, named SCCNC1, 2, 4, 5, 6 and 7. In vitro growth and invasion characteristics were evaluated and genetic profiles were compared to those of the original primary tumors. The population doubling times ranged from 21 to 34 hours. Cell lines SCCNC2 and 7 were highly invasive in matrigel. Five cell lines carried a high number of copy number alterations, including amplifications and homozygous deletions, while one showed only three abnormalities. Sequence analysis revealed three cell lines with TP53 mutation and none with KRAS or BRAF. Overexpression of p53 was observed in five, and of EGFR in four cell lines. None of the cell lines showed strong immunopositivity of p16 or presence of human papilloma virus. In conclusion, we have created six new cell lines that are clinically and genetically representative of sinonasal SCC and that will be a useful tool for the preclinical testing of new therapeutic agents.

Endothelial cell-secreted EGF induces epithelial to mesenchymal transition and endows head and neck cancer cells with stem-like phenotype

Emerging evidence suggests that endothelial cell-secreted factors contribute to the pathobiology of squamous cell carcinoma (SCC) by enhancing invasive migration and resistance to anoikis. Here, we report that SCC cells within the perivascular niche have undergone epithelial to mesenchymal transition (EMT) in a primary human SCC of a patient that developed distant metastases. Endothelial cell-secreted EGF induced EMT of human SCC cells in vitro and also induced acquisition of a stem-like phenotype. In vivo, tumor xenografts vascularized with EGF-silenced endothelial cells exhibited a smaller fraction of cancer stem-like cells (ALDH(+)CD44(+)) and were less invasive than tumors vascularized with control endothelial cells. Collectively, these results demonstrated that endothelial cell-EGF induces EMT and acquisition of stem-like properties by head and neck tumor cells. On this basis, we suggest that vascular endothelial cells contribute to tumor dissemination by secreting factors that endow carcinoma cells with enhanced motility and stemness.

A novel curcumin analog (H-4073) enhances the therapeutic efficacy of cisplatin treatment in head and neck cancer

Chemotherapy constitutes the standard modality of treatment for localized head and neck squamous cell carcinomas (HNSCC). However, many patients fail to respond and relapse after this treatments due to the acquisition of chemo-resistance. Therefore, there is an urgent need to develop novel drugs that could reverse the resistant phenotype. Curcumin, the constituent of the spice turmeric has been shown to have anti-inflammatory, anti-oxidant and anti-proliferative properties in several tumor types. However, use of curcumin has been limited due to its poor bio-absorption. Recently, a novel class of curcumin analogs, based on diarylidenylpiperidones (DAP), has been developed by incorporating a piperidone link to the beta-diketone structure and fluoro substitutions on the phenyl groups. In this study, we evaluated the effectiveness of H-4073, a parafluorinated variant of DAP, using both in vitro and in vivo head and neck cancer models. Our results demonstrate that H-4073 is a potent anti-tumor agent and it significantly inhibited cell proliferation in all the HNSCC cell lines tested in a dose-dependent manner. In addition, pretreatment of cisplatin-resistant HNSCC cell lines with H-4073 significantly reversed the chemo-resistance as observed by cell viability assay (MTT), apoptosis assay (Annexin V binding) and cleaved caspase-3 (Western blot). H-4073 mediated its anti-tumor effects by inhibiting JAK/STAT3, FAK, Akt and VEGF signaling pathways that play important roles in cell proliferation, migration, survival and angiogenesis. In the SCID mouse xenograft model, H-4073 significantly enhanced the anti-tumor and anti-angiogenesis effects of cisplatin, with no added systemic toxicity. Interestingly, H-4073 inhibited tumor angiogenesis by blocking VEGF production by tumor cells as well as directly inhibiting endothelial cell function. Taken together, our results suggest that H-4073 is a potent anti-tumor agent and it can be used to overcome chemotherapy resistance in HNSCC.

Cancer stem cells: mediators of tumorigenesis and metastasis in head and neck squamous cell carcinoma

BACKGROUND

Cancer stem cells (CSCs) represent a subpopulation of cells responsible for tumor growth. Their role in head and neck squamous cell carcinoma (HNSCC) tumorigenesis and metastasis remains uncertain.

METHODS

Wound healing and an orthotopic animal model were used to study cells expressing the CSC phenotype (CD44(high) and aldehyde dehydrogenase [ALDH](+)) and assess mobility, tumorigenesis, and metastasis. A prospective collection of 40 patient-derived primary HNSCC specimens were analyzed for CSC-proportion compared to clinical variables.

RESULTS

CSCs exhibited significantly faster wound closure and greater tumorigenesis and regional metastasis in vivo than non-CSCs. In primary patient tumors, size and advanced stage were correlated with elevated proportion of CSCs, however, not with survival.

CONCLUSION

HNSCC stem cells mediate tumorigenesis and regional metastasis in vivo. In primary patient tumors, CSC-proportion was associated with tumor size and stage, but not with metastatic spread or survival. CSC burden alone may only represent a minor variable in understanding CSCs and metastasis.

Improved clearance during treatment of HPV-positive head and neck cancer through mTOR inhibition

Human papillomavirus (HPV)-related head and neck squamous cell carcinoma (HNSCC) incidence is increasing at a near epidemic rate. We investigated whether the mammalian (or mechanistic) target of rapamycin (mTOR) inhibitor, rapamycin, can be used as a concurrent agent to standard-of-care cisplatin/radiation therapy (CRT) to attenuate tumor lactate production, thus enhancing CRT-induced immune-mediated clearance of this antigenic tumor type. A C57Bl/6-derived mouse oropharyngeal epithelial cell line retrovirally transduced with HPV type 16 E6/E7 and human squamous cell carcinoma cell lines were evaluated for their response to rapamycin in vitro with proliferation assays, Western blots, and lactate assays. Clonogenic assays and a preclinical mouse model were used to assess rapamycin as a concurrent agent to CRT. The potential of rapamycin to enhance immune response through lactate attenuation was assessed using quantitative tumor lactate bioluminescence and assessment of cell-mediated immunity using E6/E7-vaccinated mouse splenocytes. Rapamycin alone inhibited mTOR signaling of all cancer cell lines tested in vitro and in vivo. Furthermore, rapamycin administered alone significantly prolonged survival in vivo but did not result in any long-term cures. Given concurrently, CRT/rapamycin significantly enhanced direct cell killing in clonogenic assays and prolonged survival in immunocompromised mice. However, in immunocompetent mice, concurrent CRT/rapamycin increased long-term cures by 21%. Preliminary findings suggest that improved survival involves increased cell killing and enhanced immune-mediated clearance in part due to decreased lactate production. The results may provide rationale for the clinical evaluation of mTOR inhibitors concurrent with standard-of-care CRT for treatment of HPV-positive HNSCC.

High RAB25 expression is associated with good clinical outcome in patients with locally advanced head and neck squamous cell carcinoma

Currently there are no molecular markers able to predict clinical outcome in locally advanced head and neck squamous cell carcinoma (HNSCC). In a previous microarray study, RAB25 was identified as a potential prognostic marker. The aim of this study was to analyze the association between RAB25 expression and clinical outcome in patients with locally advanced HNSCC treated with standard therapy. In a retrospective immunohistochemical study (n = 97), we observed that RAB25-negative tumors had lower survival (log-rank, P = 0.01) than patients bearing positive tumors. In an independent prospective mRNA study (n = 117), low RAB25 mRNA expression was associated with poor prognosis. Using classification and regression tree analysis (CART) we established two groups of patients according to their RAB25 mRNA level and their risk of death. Low mRNA level was associated with poor local recurrence-free (log-rank, P = 0.005), progression-free (log-rank, P = 0.002) and cancer-specific (log-rank, P < 0.001) survival. Multivariate Cox model analysis showed that low expression of RAB25 was an independent poor prognostic factor for survival (hazard ratio: 3.84, 95% confidence interval: 1.93-7.62, P < 0.001). Patients whose tumors showed high RAB25 expression had a low probability of death after treatment. We also found lower RAB25 expression in tumors than in normal tissue (Mann-Whitney U, P < 0.001). Moreover, overexpression of RAB25 in the UM-SCC-74B HNSCC cell line increased cisplatin sensitivity, and reduced cell migration and invasion. Our findings support a tumor suppressor role for RAB25 in HNSCC and its potential use to identify locally advanced patients with a high probability of survival after genotoxic treatment.

Human epidermal growth factor receptor 3 (HER3) blockade with U3-1287/AMG888 enhances the efficacy of radiation therapy in lung and head and neck carcinoma

HER3 is a member of the epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases. In the present study, we investigated the capacity of the HER3 blocking antibody, U3-1287/AMG888, to modulate the in vitro and in vivo radiation response of human squamous cell carcinomas of the lung and head and neck. We screened a battery of cell lines from these tumors for HER3 expression and demonstrated that all cell lines screened exhibited expression of HER3. Importantly, U3-1287/AMG888 treatment could block both basal HER3 activity and radiation induced HER3 activation. Proliferation assays indicated that HER3 blockade could decrease the proliferation of both HNSCC cell line SCC6 and NSCLC cell line H226. Further, we demonstrated that U3-1287/AMG888 can sensitize cells to radiation in clonogenic survival assays, in addition to increasing DNA damage as detected via λ-H2AX immunofluorescence. To determine if U3-1287/AMG888 could enhance radiation sensitivity in vivo we performed tumor growth delay experiments using SCC6, SCC1483, and H226 xenografts. The results of these experiments indicated that the combination of U3-1287/AMG888 and radiation could decrease tumor growth in studies using single or fractionated doses of radiation. Analysis of HER3 expression in tumor samples indicated that radiation treatment activated HER3 in vivo and that U3-1287/AMG888 could abrogate this activation. Immunohistochemistry analysis of SCC6 tumors treated with both U3-1287/AMG888 and a single dose of radiation demonstrated that various cell survival and proliferation markers could be reduced. Collectively our findings suggest that U3-1287/AMG888 in combination with radiation has an impact on cell and tumor growth by increasing DNA damage and cell death. These findings suggest that HER3 may play an important role in response to radiation therapy and blocking its activity in combination with radiation may be of therapeutic benefit in human tumors.

Mapping C-terminal transactivation domains of the nuclear HER family receptor tyrosine kinase HER3

Nuclear localized HER family receptor tyrosine kinases (RTKs) have been observed in primary tumor specimens and cancer cell lines for nearly two decades. Inside the nucleus, HER family members (EGFR, HER2, and HER3) have been shown to function as co-transcriptional activators for various cancer-promoting genes. However, the regions of each receptor that confer transcriptional potential remain poorly defined. The current study aimed to map the putative transactivation domains (TADs) of the HER3 receptor. To accomplish this goal, various intracellular regions of HER3 were fused to the DNA binding domain of the yeast transcription factor Gal4 (Gal4DBD) and tested for their ability to transactivate Gal4 UAS-luciferase. Results from these analyses demonstrated that the C-terminal domain of HER3 (CTD, amino acids distal to the tyrosine kinase domain) contained potent transactivation potential. Next, nine HER3-CTD truncation mutants were constructed to map minimal regions of transactivation potential using the Gal4 UAS-luciferase based system. These analyses identified a bipartite region of 34 (B₁) and 27 (B₂) amino acids in length that conferred the majority of HER3’s transactivation potential. Next, we identified full-length nuclear HER3 association and regulation of a 122 bp region of the cyclin D1 promoter. To understand how the B₁ and B₂ regions influenced the transcriptional functions of nuclear HER3, we performed cyclin D1 promoter-luciferase assays in which HER3 deleted of the B₁ and B₂ regions was severely hindered in regulating this promoter. Further, the overexpression of HER3 enhanced cyclin D1 mRNA expression, while HER3 deleted of its identified TADs was hindered at doing so. Thus, the ability for HER3 to function as a transcriptional co-activator may be dependent on specific C-terminal TADs.

HSP90 Inhibitor SNX5422/2112 Targets the Dysregulated Signal and Transcription Factor Network and Malignant Phenotype of Head and Neck Squamous Cell Carcinoma

Heat shock protein 90 (HSP90) is a chaperone protein that stabilizes proteins involved in oncogenic and therapeutic resistance pathways of epithelial cancers, including head and neck squamous cell carcinomas (HNSCCs). Here, we characterized the molecular, cellular, and preclinical activity of HSP90 inhibitor SNX5422/2112 in HNSCC overexpressing HSP90. SNX2112 inhibited proliferation, induced G2/M block, and enhanced cytotoxicity, chemosensitivity, and radiosensitivity between 25 and 250 nM in vitro. SNX2112 showed combinatorial activity with paclitaxel in wild-type (wt) TP53-deficient and cisplatin in mutant (mt) TP53 HNSCC lines. SNX2112 decreased expression or phosphorylation of epidermal growth factor receptor (EGFR), c-MET, v-akt murine thymoma viral oncogene homolog 1 (AKT), extracellular signal-regulated kinases (ERK) 1 and 2, inhibitor κB kinase, and signal transducer and transcription factor 3 (STAT3), corresponding downstream nuclear factor κB, activator protein-1, and STAT3 reporter genes, and target oncogenes and angiogenic cytokines. Furthermore, SNX2112 enhanced re-expression of TP53 and targets p21WAF1 and PUMA, while TP53 inhibitor Pifithrin or siRNA attenuated the antiproliferative activity of SNX2112 in wtTP53 HNSCC in vitro. Prodrug SNX5422 similarly down-modulated key signal targets, enhanced TP53 expression and apoptosis, and inhibited proliferation, angiogenesis, and tumorigenesis in a wtTP53-deficient HNSCC xenograft model. Thus, HSP90 inhibitor SNX5422/2112 broadly modulates multiple key nodes within the dysregulated signaling network, with corresponding effects upon the malignant phenotype. Our data support investigation of SNX5422/2112 in combination with paclitaxel, cisplatin, and radiotherapy in HNSCC with different TP53 status.

PI3K/mTOR inhibitor PF-04691502 antitumor activity is enhanced with induction of wild-type TP53 in human xenograft and murine knockout models of head and neck cancer

PURPOSE

Phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway activation is often associated with altered expression or mutations of PIK3CA, TP53/p73, PTEN, and TGF-β receptors (TGFBR) in head and neck squamous cell carcinomas (HNSCC). However, little is known about how these alterations affect response to PI3K/mTOR-targeted agents.

EXPERIMENTAL DESIGN

In this preclinical study, PI3K/Akt/mTOR signaling was characterized in nine HNSCC (UM-SCC) cell lines and human oral keratinocytes. We investigated the molecular and anticancer effects of dual PI3K/mTOR inhibitor PF-04691502(PF-502) in UM-SCC expressing PIK3CA with decreased wild-type TP53, mutant TP53-/+ mutantTGFBR2, and in HNSCC of a conditional Pten/Tgfbr1 double knockout mouse model displaying PI3K/Akt/mTOR activation.

RESULTS

UM-SCC showed increased PIK3CA expression and Akt/mTOR activation, and PF-502 inhibited PI3K/mTORC1/2 targets. In human HNSCC expressing PIK3CA and decreased wtTP53 and p73, PF-502 reciprocally enhanced TP53/p73 expression and growth inhibition, which was partially reversible by p53 inhibitor pifithrin-α. Most UM-SCC with wtTP53 exhibited a lower IC50 than those with mtTP53 status. PF-502 blocked growth in G0-G1 and increased apoptotic sub-G0 DNA. PF-502 suppressed tumorigenesis and showed combinatorial activity with radiation in a wild-type TP53 UM-SCC xenograft model. PF-502 also significantly delayed HNSCC tumorigenesis and prolonged survival of Pten/Tgfbr1-deficient mice. Significant inhibition of p-Akt, p-4EBP1, p-S6, and Ki67, as well as increased p53 and TUNEL were observed in tumor specimens.

CONCLUSIONS

PI3K-mTOR inhibition can enhance TP53/p73 expression and significantly inhibit tumor growth alone or when combined with radiation in HNSCC with wild-type TP53. PIK3CA, TP53/p73, PTEN, and TGF-β alterations are potential modifiers of response and merit investigation in future clinical trials with PI3K-mTOR inhibitors.

Nuclear EGFR as a molecular target in cancer

The epidermal growth factor receptor (EGFR) has been one of the most targeted receptors in the field of oncology. While anti-EGFR inhibitors have demonstrated clinical success in specific cancers, most patients demonstrate either intrinsic or acquired resistance within one year of treatment. Many mechanisms of resistance to EGFR inhibitors have been identified, one of these being attributed to alternatively localized EGFR from the cell membrane into the cell's nucleus. Inside the nucleus, EGFR functions as a co-transcription factor for several genes involved in cell proliferation and angiogenesis, and as a tyrosine kinase to activate and stabilize proliferating cell nuclear antigen and DNA dependent protein kinase. Nuclear localized EGFR is highly associated with disease progression, worse overall survival in numerous cancers, and enhanced resistance to radiation, chemotherapy, and the anti-EGFR therapies gefitinib and cetuximab. In this review the current knowledge of how nuclear EGFR enhances resistance to cancer therapeutics is discussed, in addition to highlighting ways to target nuclear EGFR as an anti-cancer strategy in the future.

Galanin has tumor suppressor activity and is frequently inactivated by aberrant promoter methylation in head and neck cancer

PURPOSE

There is accumulating evidence that galanin receptors (GALRs) may be tumor suppressors in head and neck squamous cell carcinoma (HNSCC). Promoter methylation status and gene expression were assessed in a large panel of primary tumors, based on the hypothesis that CpG hypermethylation might silence the galanin gene.

EXPERIMENTAL DESIGN

Galanin expression was examined using reverse transcription-polymerase chain reaction (PCR). The methylation status of the galanin promoter was studied using bisulfate sequencing and methylation-specific PCR. UM-SCC-54 was stably transfected to express galanin.

RESULTS

Galanin expression was absent in 3/12 (25.0%) UM-SCC cell lines, whereas three nonmalignant cell lines had stable expression. Galanin methylation was found in 24/100 (24.0%) cases. HNSCC tumor specimens was significantly correlated with the GALR1 methylation status (P = 1.88E-06). The presence of galanin promoter hypermethylation was statistically correlated with a decrease in disease-free survival (log-rank test, P = 6.02E-05). A multivariate logistic regression analysis showed that methylation of galanin and methylation of the gene pair galanin and GALR1 had an odds ratio for recurrence of 8.95 [95% confidence interval (CI), 2.29-35.03] and 23.84 (95% CI, 2.74-207.17), respectively. UM-SCC-54 cells that are GALR1-proficient but have hypermethylated galanin exhibited suppressed cell proliferation following exogenous expression of galanin.

CONCLUSIONS

Association of frequent promoter hypermethylation and gene silencing with poor survival, combined with growth suppression of HNSCC cells after forced gene expression, supports the hypothesis that galanin acts as a tumor suppressor. These data suggest that galanin and GALR1 are potential therapeutic targets and prognostic factors.

Head and neck cancer stem cells: the effect of HPV--an in vitro and mouse study

OBJECTIVES

To determine if the behavior of cancer stem cells (CSCs) is affected by human papillomavirus (HPV) status.

STUDY DESIGN

An in vitro and in vivo analysis of HPV and CSCs.

SETTING

University laboratory.

SUBJECTS AND METHODS

We isolated CSCs from HPV-positive and HPV-negative cell lines. Two HPV-negative cell lines underwent lentiviral transduction of E6/E7. Chemoresistence was determined using colony formation assays. Native HPV-positive and HPV E6/E7-transduced cells were compared for lung colonization after tail vein injection in NOD/SCID mice.

RESULTS

The proportion of CSC is not significantly different in HPV-positive or HPV-negative head and neck squamous cell carcinoma (HNSCC) cell lines. The HNSCC CSCs are more resistant to cisplatin than the non-CSCs, but there were no significant differences between HPV-positive and HPV-negative cells. The HPV-negative cancer cells yielded low colony formation after cell sorting. After transduction with HPV E6/E7, increased colony formation was observed in both CSCs and non-CSCs. Results from tail vein injections yielded no differences in development of lung colonies between HPV E6/E7-transduced cells and nontransduced cells.

CONCLUSIONS

Human papillomavirus status does not correlate with the proportion of CSCs present in HNSCC. The HPV-positive cells and those transduced with HPV E6/E7 have a greater clonogenicity than HPV-negative cells. The HNSCC CSCs are more resistant to cisplatin than non-CSCs. This suggests that common chemotherapeutic agents may shrink tumor bulk by eliminating non-CSCs, whereas CSCs have mechanisms that facilitate evasion of cell death. Human papillomavirus status does not affect CSC response to cisplatin therapy, suggesting that other factors explain the better outcomes for patients with HPV-positive cancer.

TGF-β and NF-κB signal pathway cross-talk is mediated through TAK1 and SMAD7 in a subset of head and neck cancers

Transforming growth factor-beta (TGF-β) has a dual role in epithelial malignancies, including head and neck squamous cell carcinoma (HNSCC). Attenuation of canonical TGF-β signaling enhances de novo tumor development, whereas TGF-β overexpression and signaling paradoxically promotes malignant progression. We recently observed that TGF-β-induced growth arrest response is attenuated, in association with aberrant activation of nuclear factor-κB (NF-κB), a transcription factor, which promotes malignant progression in HNSCC. However, what role cross-talk between components of the TGF-β and NF-κB pathways plays in altered activation of these pathways has not been established. Here, we show TGF-β receptor II and TGF-β-activated kinase 1 (TAK1) are predominantly expressed in a subset of HNSCC tumors with nuclear activation of NF-κB family member RELA (p65). Further, TGF-β1 treatment induced sequential phosphorylation of TAK1, IKK, IκBα and RELA in human HNSCC lines. TAK1 enhances TGF-β-induced NF-κB activation, as TAK1 siRNA knockdown decreased TGF-β1-induced phosphorylation of IKK, IκB and RELA, degradation of IκBα, RELA nuclear translocation and DNA binding, and NF-κB-induced reporter and target gene transcription. Functionally, TAK1 siRNA inhibited cell proliferation, migration and invasion. Celastrol, a TAK1 inhibitor and anti-inflammatory compound used in traditional Chinese medicine, also decreased TGF-β1-induced phosphorylation of TAK1 and RELA, and suppressed basal, TGF-β1- and tumor necrosis factor-alpha (TNF-α)-induced NF-κB reporter gene activity. Celastrol also inhibited cell proliferation, while increasing sub-G0 DNA fragmentation and Annexin V markers of apoptosis. Furthermore, TGF-β and RELA activation promoted SMAD7 expression. In turn, SMAD7 preferentially suppressed TGF-β-induced SMAD and NF-κB reporters when compared with constitutive or TNF-α-induced NF-κB reporter gene activation. Thus, cross-talk by TGF-β via TAK1 and NF-κB promotes the malignant phenotype of HNSCC. Moreover, NF-κB may contribute to the downstream attenuation of canonical TGF-β signaling through increased SMAD7 expression. Celastrol highlights the therapeutic potential of agents targeting TAK1 as a key node in this pro-oncogenic TGF-β-NF-κB signal pathway.

Radiation-induced loss of cell surface CD47 enhances immune-mediated clearance of human papillomavirus-positive cancer

The increasing incidence of human papillomavirus (HPV) related oropharyngeal squamous cell carcinoma (OSSC) demands development of novel therapies. Despite presenting at a more advanced stage, HPV(+) oropharyngeal squamous cell carcinoma (OSCC) have a better prognosis than their HPV(-) counterparts. We have previously demonstrated that clearance of HPV(+) OSCC during treatment with radiation and chemotherapy requires an immune response which is likely responsible for the improved clinical outcomes. To further elucidate the mechanism of immune-mediated clearance, we asked whether radiation therapy induces tumor cell changes that allow the body to recognize and aid in tumor clearance. Here, we describe a radiation-induced change in tumor surface protein expression that is critical for immune-mediated clearance. Radiation therapy decreases surface expression of CD47, a self-marker. CD47 is frequently overexpressed in head and neck squamous cell carcinoma and radiation induces a decrease of CD47 in a dose-dependent manner. We show that both in vitro and in vivo tumor cell CD47 protein levels are restored over time after sublethal radiation exposure and that protein levels on adjacent, normal tissues remain unaffected. Furthermore, reduction of tumor cell CD47 increases phagocytosis of these cells by dendritic cells and leads to increased interferon gamma and granzyme production from mixed lymphocytes. Finally, decreasing tumor cell CD47 in combination with standard radiation and chemotherapy results in improved immune-mediated tumor clearance in vivo. These findings help define an important mechanism of radiation-related immune clearance and suggest that decreasing CD47 specifically on tumor cells may be a good therapeutic target for HPV related disease.

Dacomitinib, an irreversible Pan-ErbB inhibitor significantly abrogates growth in head and neck cancer models that exhibit low response to cetuximab

Aberrant epidermal growth factor (EGF) signaling is associated with tumor growth in squamous cell carcinoma of the head and neck in humans (HNSCC), and is a major focus of targeted therapy. Cetuximab, a monoclonal antibody against EGFR, has been successful at prolonging survival but has only a 10% tumor shrinkage response rate in a clinical setting. The goal of this study was to compare dacomitinib (PF-00299804), a next generation small molecule tyrosine kinase inhibitor that irreversibly blocks multiple HER family receptors (HER-1 (EGFR), HER-2 and HER-4 tyrosine kinases), to cetuximab, the current FDA approved anti-EGFR medication for HNSCC and erlotinib, an EGFR specific small molecule tyrosine kinase inhibitor. Dacomitinib, erlotinib and cetuximab were tested in a panel of 27 HNSCC cell lines. Treatment with 100 ug/ml of cetuximab or 1 uM of erlotinib inhibited growth by at least 50% in 7/27 cell lines, while treatment with 1 uM of dacomitinib had similar growth inhibition in 17/27 lines. Cell lines representing three levels of sensitivity to dacomitinib were further examined using Western blots, cell cycle and apoptosis analysis. Treatment with 100 nM of dacomitinib reduced EGFR activity and downstream AKT and ERK pathways more effectively than treatment with 100 ug/ml of cetuximab in all ten tested lines. Although both compounds induced apoptosis at similar levels, dacomitinib caused greater G0/G1 arrest. Sensitivity to EGFR blockade was associated with levels of EGFR and ERK and was not associated with common oncogenic mutations and copy number variations. Phosphorylated and total EGFR and ERK levels correlate with sensitivity to both cetuximab and dacomitinib. Three of the four lines in the exquisitely sensitive group had the highest levels of phosphorylated and total EGFR and ERK among the ten lines selected, while the three resistant lines collectively had the lowest levels. Neither pAKT nor tAKT was associated with sensitivity.

Overexpression of RNA-binding protein CELF1 prevents apoptosis and destabilizes pro-apoptotic mRNAs in oral cancer cells

CELF1 RNA-binding protein, otherwise called CUGBP1, associates and coordinates the degradation of GU-rich element (GRE) containing mRNA’s encoding factors important for cell growth, migration and apoptosis. Although many substrates of CELF1 have been identified, the biological significance of CELF1-mediated mRNA decay remains unclear. As the processes modulated by CELF1 are frequently disrupted in cancer, we investigated the expression and role of CELF1 in oral squamous cancer cells (OSCCs). We determined that CELF1 is reproducibly overexpressed in OSCC tissues and cell lines. Moreover, depletion of CELF1 reduced proliferation and increased apoptosis in OSCCs, but had negligible effect in non-transformed cells. We found that CELF1 associates directly with the 3′UTR of mRNAs encoding the pro-apoptotic factors BAD, BAX and JunD and mediates their rapid decay. Specifically, 3′UTR fragment analysis of JunD revealed that the GRE region is critical for binding with CELF1 and expression of JunD in oral cancer cells. In addition, silencing of CELF1 rendered BAD, BAX and JunD mRNAs stable and increased their protein expression in oral cancer cells. Taken together, these results support a critical role for CELF1 in modulating apoptosis and implicate this RNA-binding protein as a cancer marker and potential therapeutic target.

Dihydroceramide desaturase knockdown impacts sphingolipids and apoptosis after photodamage in human head and neck squamous carcinoma cells

BACKGROUND

Dihydroceramide desaturase 1 (DES) is the enzyme responsible for converting dihydroceramide into ceramide in the de novo sphingolipid biosynthesis pathway. Dihydroceramide can inhibit ceramide channel formation to interfere with apoptosis. We have shown that following ceramide synthase knockdown, photodynamic therapy (PDT), a cancer treatment modality, is associated with decreased levels of ceramides and dihydroceramides in cells that are resistant to apoptosis.

AIM

Here we investigated the effect of DES knockdown on the sphingolipid profile and apoptosis in human head and neck squamous carcinoma cells after PDT with the silicon phthalocyanine Pc 4.

MATERIALS AND METHODS

Following siRNA transfection and PDT treatment, quantitative real-time polymerase chain reaction for quantification of DES mRNA, immunoblotting for protein expression, mass spectrometry for sphingolipid analysis, spectrofluorometry for caspase 3-like (DEVDase) activity, flow cytometry for apoptosis detection, and trypan blue assay for cell viability evaluation, were performed.

RESULTS

Down-regulation of DES led to a substantial increase in levels of dihydroceramides without affecting ceramide levels. PDT-induced accumulation of individual dihydroceramides and global ceramides was increased by DES knockdown. Concomitantly, mitochondrial depolarization, DEVDase activation, late-apoptosis and cell death were attenuated by DES knockdown. Early apoptosis, however, was enhanced.

CONCLUSION

Our findings support the following: (i) dihydroceramide reduces pro-apoptotic effects of ceramide; (ii) cells adapt to DES knockdown to become more sensitive to ceramide and early-apoptosis; (iii) DES is a potential molecular target for regulating apoptotic resistance to PDT.

Inhibition of Plk1 and Cyclin B1 expression results in panobinostat-induced G₂ delay and mitotic defects

The development of clinically useful histone deacetylase inhibitors has expanded greatly. In a preclinical study, we showed that panobinostat (LBH589) inhibits cell cycle progression of human head and neck squamous cell carcinoma (HNSCC) cell lines at G₂/M and an associated decrease in expression of particular genes required for passage through G₂ and mitosis. In this study we sought to analyse the mechanistic underpinnings of panobinostat-induced growth arrest. HNSCC cell lines were synchronised and progression through mitosis monitored. We demonstrate that panobinostat causes a marked G₂ delay and mitotic defects. A loss of G₂-specific Plk1 and Cyclin B1 expression and co-incident increase in p21(Waf1/Cip1) expression is also shown. Furthermore, we show a significant loss of E2F1 recruitment to the promoters of these genes in response to panobinostat treatment. These data provide mechanistic evidence of panobinostat-induced cell cycle arrest and highlight its potential as a chemotherapeutic agent for HNSCC.

Deficient DNA damage signaling leads to chemoresistance to cisplatin in oral cancer

Activation of the cellular DNA damage response (DDR) is an important determinant of cell sensitivity to cisplatin and other chemotherapeutic drugs that eliminate tumor cells through induction of DNA damage. It is therefore important to investigate whether alterations of the DNA damage-signaling pathway confer chemoresistance in cancer cells and whether pharmacologic manipulation of the DDR pathway can resensitize these cells to cancer therapy. In a panel of oral/laryngeal squamous cell carcinoma (SCC) cell lines, we observed deficiencies in DNA damage signaling in correlation with cisplatin resistance, but not with DNA repair. These deficiencies are consistent with reduced expression of components of the ataxia telangiectasia mutated (ATM)-dependent signaling pathway and, in particular, strong upregulation of Wip1, a negative regulator of the ATM pathway. Wip1 knockdown or inhibition enhanced DNA damage signaling and resensitized oral SCC cells to cisplatin. In contrast to the previously reported involvement of Wip1 in cancer, Wip1 upregulation and function in these SCC cells is independent of p53. Finally, using xenograft tumor models, we showed that Wip1 upregulation promotes tumorigenesis and its inhibition improves the tumor response to cisplatin. Thus, this study reveals that chemoresistance in oral SCCs is partially attributed to deficiencies in DNA damage signaling, and Wip1 is an effective drug target for enhanced cancer therapy.

A combination of a ribonucleotide reductase inhibitor and histone deacetylase inhibitors downregulates EGFR and triggers BIM-dependent apoptosis in head and neck cancer

Head and neck squamous cell carcinomas (HNSCCs) are the sixth most common malignant neoplasm and more than 50% of patients succumb to this disease. HNSCCs are characterized by therapy resistance, which relies on the overexpression of anti-apoptotic proteins and on the aberrant regulation of the epidermal growth factor receptor (EGFR). As inherent and acquired resistance to therapy counteracts improvement of long-term survival, novel multi-targeting strategies triggering cancer cell death are urgently required. We investigated how induction of replicational stress by the ribonucleotide reductase inhibitor hydroxyurea (HU) combined with histone deacetylase inhibitors (HDACi) exerts anti-tumor activity. We treated HNSCC cell lines and freshly isolated tumor cells with HDACi, such as the clinically approved anti-epileptic drug valproic acid (VPA), in combination with HU. Our data demonstrate that at clinically achievable levels VPA/HU combinations efficiently block proliferation as well as clonogenic survival, and trigger apoptosis of HNSCC cells. In the presence of VPA/HU, such tumor cells increase expression of the pro-apoptotic BCL-2 family protein BIM, independent of wild-type p53 signaling and in the absence of increased expression of the p53 targets PUMA and BAX. The pro-apoptotic activity of BIM in HNSCCs was found critical for tumor cell death; ectopic overexpression of BIM induced HNSCC apoptosis and RNAi-mediated depletion of BIM protected HNSCC cells from VPA/HU. Also, significantly elevated BIM levels (p<0.01) were detectable in the apoptotic tumor centers versus proliferating tumor margins in HNSCC patients (n=31), underlining BIM's clinical relevance. Importantly, VPA/HU treatment additionally reduces expression and cell surface localization of EGFR. Accordingly, in a xenograft mouse model, VPA/HU efficiently blocked tumor growth (P<0.001) correlating with BIM induction and EGFR downregulation. We provide a molecular rationale for the potent anti-cancer activities of this drug combination. Our data suggest its exploitation as a potential strategy for the treatment of HNSCC and other tumor entities characterized by therapy resistance linked to dysregulated EGFR activation.

siRNA-mediated down-regulation of ceramide synthase 1 leads to apoptotic resistance in human head and neck squamous carcinoma cells after photodynamic therapy

BACKGROUND

The effectiveness of photodynamic therapy (PDT) for cancer treatment correlates with apoptosis. We previously observed that the knockdown of ceramide synthase 6, an enzyme from the de novo sphingolipid biosynthesis pathway, is associated with marked reduction in C18-dihydroceramide and makes cells resistant to apoptosis post-PDT. Down-regulation of ceramide synthase 1 (CERS1) can also render cells resistant to anticancer drugs.

AIM

To explore the impact of CERS1 knockdown on apoptosis and the sphingolipid profile, post-PDT, with the silicone phthalocyanine Pc 4, in a human head and neck squamous carcinoma cell line.

MATERIALS AND METHODS

Besides siRNA transfection and PDT treatment, the following methods were used: immunoblotting for protein expression, mass spectrometry for sphingolipid analysis, spectroflurometry and flow cytometry for apoptosis detection, and trypan blue assay for cell viability evaluation.

RESULTS

CERS1 knockdown led to inhibition of PDT-induced caspase 3-like (DEVDase) activation, of apoptosis and cell death. CERS1 knockdown was associated with global and selective decreases in ceramides and dihydroceramides, in particular C18-, C18:1- and C20-ceramide post-PDT.

CONCLUSION

Our novel findings are consistent with the notion that CERS1 regulates apoptotic resistance to PDT, partly via C18- and C20-ceramide, and that CERS1 is a molecular target for controlling resistance to PDT.

CXCL13 activation of c-Myc induces RANK ligand expression in stromal/preosteoblast cells in the oral squamous cell carcinoma tumor-bone microenvironment

CXC chemokine ligand-13 (CXCL13) has been implicated in oral squamous cell carcinoma (OSCC) tumor progression and osteolysis. The tumor necrosis factor family member RANKL (receptor activator of NF-κB ligand), a critical bone resorbing osteoclastogenic factor, has an important role in cancer invasion of bone/osteolysis. Here, we show high-level expression of CXCL13 in primary human OSCC tumor specimens; however, human bone marrow-derived stromal (SAKA-T) and murine preosteoblast (MC3T3-E1) cells produce at very low level. Recombinant CXCL13 (0-15 ng/ml) dose dependently induced CXCR5 expression in SAKA-T and MC3T3-E1 cells. Conditioned media obtained from OSCC cell lines increased the RANKL expression and an antibody against the CXCL13 specific receptor, CXCR5 markedly decreased RANKL expression in these cells. Furthermore, CXCL13 increased hRANKL-Luc promoter activity. Superarray screening identified c-Myc and NFATc3 transcription factors upregulated in CXCL13-stimulated SAKA-T cells. Immunohistochemical analysis of OSCC tumors that developed in athymic mice demonstrated RANKL and NFATc3 expression in tumor and osteoblast cells, however, showed p-c-Myc expression specific to osteoblastic cells at the tumor-bone interface. We further identified NFATc3 expression, but not c-Myc activation in primary human OSCC tumor specimens compared with adjacent normal tissue. Also, CXCL13 significantly increased p-ERK1/2 in SAKA-T and MC3T3-E1 cells. siRNA suppression of c-Myc expression markedly decreased CXCL13-induced RANKL and NFATc3 expression in preosteoblast cells. Chromatin-immuno precipitation assay confirmed p-c-Myc binding to the hRANKL promoter region. In summary, c-Myc activation through CXCL13-CXCR5 signaling axis stimulates RANKL expression in stromal/preosteoblast cells. Thus, our results implicate CXCL13 as a potential therapeutic target to prevent OSCC invasion of bone/osteolysis.

ErbB2, EphrinB1, Src kinase and PTPN13 signaling complex regulates MAP kinase signaling in human cancers

In non-cancerous cells, phosphorylated proteins exist transiently, becoming de-phosphorylated by specific phosphatases that terminate propagation of signaling pathways. In cancers, compromised phosphatase activity and/or expression occur and contribute to tumor phenotype. The non-receptor phosphatase, PTPN13, has recently been dubbed a putative tumor suppressor. It decreased expression in breast cancer correlates with decreased overall survival. Here we show that PTPN13 regulates a new signaling complex in breast cancer consisting of ErbB2, Src, and EphrinB1. To our knowledge, this signaling complex has not been previously described. Co-immunoprecipitation and localization studies demonstrate that EphrinB1, a PTPN13 substrate, interacts with ErbB2. In addition, the oncogenic V660E ErbB2 mutation enhances this interaction, while Src kinase mediates EphrinB1 phosphorylation and subsequent MAP Kinase signaling. Decreased PTPN13 function further enhances signaling. The association of oncogene kinases (ErbB2, Src), a signaling transmembrane ligand (EphrinB1) and a phosphatase tumor suppressor (PTPN13) suggest that EphrinB1 may be a relevant therapeutic target in breast cancers harboring ErbB2-activating mutations and decreased PTPN13 expression.

UM-SCC-104: a new human papillomavirus-16-positive cancer stem cell-containing head and neck squamous cell carcinoma cell line

BACKGROUND

Few human papillomavirus (HPV)(+) head and neck squamous cell carcinoma (HNSCC) cell lines exist. We established University of Michigan-squamous cell carcinoma-104 (UM-SCC-104), a new HPV(+) HNSCC cell line from a recurrent oral cavity tumor, and characterized it for the presence of cancer stem cells (CSCs).

METHODS

Tumor cells were tested for biomarker expression by immunohistology, and the presence of HPV was assessed by several methods.

RESULTS

UM-SCC-104 has a unique genotype, contains HPV-16, and expresses E6/E7. Inoculation of aldehyde dehydrogenase (ALDH)(+) and ALDH(-) cells in an immunocompromised mouse resulted in tumor growth from the ALDH(+) cells after 6 weeks that recapitulated the histology of the primary, whereas ALDH(-) cells did not produce tumors.

CONCLUSION

UM-SCC-104, a new HPV-16, CSC-containing HNSCC cell line will aid in studying recurrent HPV(+) tumors. The aggressive nature of this tumor is consistent with high uniform expression of epidermal growth factor receptor (EGFR) and a functionally significant proportion of ALDH(+) CSCs.

ERK1/2 regulation of CD44 modulates oral cancer aggressiveness

Carcinogen-induced oral cavity squamous cell carcinoma (OSCC) incurs significant morbidity and mortality and constitutes a global health challenge. To gain further insight into this disease, we generated cell line models from 7,12-dimethylbenz(a)anthracene-induced murine primary OSCC capable of tumor formation upon transplantation into immunocompetent wild-type mice. Whereas several cell lines grew rapidly and were capable of metastasis, some grew slowly and did not metastasize. Aggressively growing cell lines displayed ERK1/2 activation, which stimulated expression of CD44, a marker associated with epithelial to mesenchymal transition and putative cancer stem cells. MEK (MAP/ERK kinase) inhibition upstream of ERK1/2 decreased CD44 expression and promoter activity and reduced cell migration and invasion. Conversely, MEK1 activation enhanced CD44 expression and promoter activity, whereas CD44 attenuation reduced in vitro migration and in vivo tumor formation. Extending these findings to freshly resected human OSCC, we confirmed a strict relationship between ERK1/2 phosphorylation and CD44 expression. In summary, our findings identify CD44 as a critical target of ERK1/2 in promoting tumor aggressiveness and offer a preclinical proof-of-concept to target this pathway as a strategy to treat head and neck cancer.

TNF-α promotes c-REL/ΔNp63α interaction and TAp73 dissociation from key genes that mediate growth arrest and apoptosis in head and neck cancer

Inflammation-induced activation of proto-oncogenic NF-κB/REL and dysfunction of tumor suppressor TP53/p63/p73 family transcription factors are key events in cancer progression. How inflammatory signaling coordinates dysregulation of these two transcription factor families during oncogenesis remains incompletely understood. Here, we observed that oncoprotein c-REL and tumor suppressor TAp73 are coexpressed and complex with ΔNp63α in the nucleus of a subset of head and neck squamous cell carcinoma (HNSCC) cell lines with mutant (mt)TP53. TNF-α, a proinflammatory cytokine, promoted c-REL nuclear translocation, c-REL/ΔNp63α interaction, and dissociation of TAp73 from ΔNp63α and the nucleus to the cytoplasm, whereas c-REL siRNA knockdown attenuated this effect. Overexpression of c-REL or a c-REL κB-site DNA-binding mutant enhanced protein interaction with ΔNp63α and TAp73 dissociation, implicating c-REL/ΔNp63α-specific interactions in these effects. We discovered that TNF-α or genetic alteration of c-REL expression inversely modulates ΔNp63α/TAp73 interactions on distinct p63 DNA-binding sites, including those for key growth arrest and apoptotic genes p21WAF1, NOXA, and PUMA. Functionally, c-REL repressed these genes and the antiproliferative effects of TNF-α or TAp73. Conversely, c-REL siRNA depletion enhanced TAp73 promoter interaction and expression of genes mediating growth arrest and apoptosis. Similar to TNF-α-treated HNSCC lines, human HNSCC tumors and hyperplastic squamous epithelia of transgenic mice overexpressing ΔNp63α that exhibit inflammation also show increased nuclear c-REL/ΔNp63α and cytoplasmic TAp73 localization. These findings unveil a novel and reversible dynamic mechanism whereby proinflammatory cytokine TNF-α-induced c-REL/ΔNp63α interactions inactivate tumor suppressor TAp73 function, promoting TNF-α resistance and cell survival in cancers with mtTP53.

A positive feedback loop between HER2 and ADAM12 in human head and neck cancer cells increases migration and invasion

Increased activation of epidermal growth factor receptor (EGFR) family members such as HER2/Erbb2 can result in more aggressive disease, resistance to chemotherapy and reduced survival of head and neck squamous cell carcinoma (HNSCC) patients. In order to identify mechanisms through which these receptor tyrosine kinases accelerate tumor progression, the regulation of metalloprotease expression by EGFR family members was investigated in 11 SCC cell lines. HER2 expression was significantly correlated with ADAM12 (A Disintegrin And Metalloprotease 12) expression in these cell lines and was co-expressed in human head and neck cancers. Inhibition of HER2 or EGFR decreased ADAM12 transcripts while HER2 transfection up-regulated ADAM12 expression. To understand the molecular mechanisms underlying HER2 regulation of ADAM12, we investigated the signaling pathways directing ADAM12 production in SCC cells. Inhibition of phosphatidyl inositol-3-kinase (PI3K) or mammalian Target of Rapamycin (mTOR) decreased ADAM12 transcripts in HER2-expressing SCC cells, while transfection with AKT increased ADAM12 mRNA. Experiments utilizing ADAM12 transfection or siRNA targeting of ADAM12 revealed that the protease increased both the migration and invasiveness of oral SCC cells. Surprisingly, ADAM12 also increased HER2 message, protein levels, and activity through an Ets1-dependent mechanism. Collectively, these results reveal a novel positive activation loop between ADAM12 and HER2 that may contribute to HNSCC progression.

Cetuximab augments cytotoxicity with poly (adp-ribose) polymerase inhibition in head and neck cancer

Overexpression of the epidermal growth factor receptor (EGFR) is a hallmark of head and neck cancers and confers increased resistance and inferior survival rates. Despite targeted agents against EGFR, such as cetuximab (C225), almost half of treated patients fail this therapy, necessitating novel therapeutic strategies. Poly (ADP-Ribose) polymerase (PARP) inhibitors (PARPi) have gained recent attention due to their unique selectivity in killing tumors with defective DNA repair. In this study, we demonstrate that C225 enhances cytotoxicity with the PARPi ABT-888 in UM-SCC1, UM-SCC6, and FaDu head and neck cancer cells. The mechanism of increased susceptibility to C225 and PARPi involves C225-mediated reduction of non-homologous end-joining (NHEJ)- and homologous recombination (HR)-mediated DNA double strand break (DSB) repair, the subsequent persistence of DNA damage, and activation of the intrinsic apoptotic pathway. By generating a DSB repair deficiency, C225 can render head and neck tumor cells susceptible to PARP inhibition. The combination of C225 and the PARPi ABT-888 can thus be an innovative treatment strategy to potentially improve outcomes in head and neck cancer patients. Furthermore, this strategy may also be feasible for other EGFR overexpressing tumors, including lung and brain cancers.

Assembly and initial characterization of a panel of 85 genomically validated cell lines from diverse head and neck tumor sites

PURPOSE

Human cell lines are useful for studying cancer biology and preclinically modeling cancer therapy, but can be misidentified and cross-contamination is unfortunately common. The purpose of this study was to develop a panel of validated head and neck cell lines representing the spectrum of tissue sites and histologies that could be used for studying the molecular, genetic, and phenotypic diversity of head and neck cancer.

METHODS

A panel of 122 clinically and phenotypically diverse head and neck cell lines from head and neck squamous cell carcinoma, thyroid cancer, cutaneous squamous cell carcinoma, adenoid cystic carcinoma, oral leukoplakia, immortalized primary keratinocytes, and normal epithelium was assembled from the collections of several individuals and institutions. Authenticity was verified by carrying out short tandem repeat analysis. Human papillomavirus (HPV) status and cell morphology were also determined.

RESULTS

Eighty-five of the 122 cell lines had unique genetic profiles. HPV-16 DNA was detected in 2 cell lines. These 85 cell lines included cell lines from the major head and neck primary tumor sites, and close examination shows a wide range of in vitro phenotypes.

CONCLUSIONS

This panel of 85 genomically validated head and neck cell lines represents a valuable resource for the head and neck cancer research community that can help advance understanding of the disease by providing a standard reference for cell lines that can be used for biological as well as preclinical studies.

Alteration of microRNA profiles in squamous cell carcinoma of the head and neck cell lines by human papillomavirus

BACKGROUND

Human papillomavirus (HPV)-positive cases of squamous cell carcinoma of the head and neck (SCCHN) have a much better disease outcome compared to SCCHN cases lacking HPV. Differences in microRNA (miRNA) expression may affect their clinical outcomes.

METHODS

The miRNA expression was studied using microarrays and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) in HPV-16-positive and HPV-negative SCCHN cell lines. The role of HPV-16 E6 and E7 oncogenes in altering miRNA expression was investigated using human foreskin keratinocytes (HFKs).

RESULTS

The miRNAs miR-363, miR-33, and miR-497 were upregulated, whereas miR-155, miR-181a, miR-181b, miR-29a, miR-218, miR-222, miR-221, and miR-142-5p were downregulated in HPV-positive cells compared to both HPV-negative SCCHN and normal oral keratinocytes. HPV-16 E6 oncogene altered miRNA expression in HFKs and in an HPV-16-positive cell line with E6 knockdown using siRNA.

CONCLUSION

miRNAs differentially expressed in the presence of HPV-16 may provide biomarkers for SCCHN and identify cellular pathways targeted by this virus.

Sensitization of head and neck cancer to cisplatin through the use of a novel curcumin analog

OBJECTIVE

To determine whether a novel small molecule inhibitor derived from curcumin (FLLL32) that targets signal transducer and activator of transcription (STAT) 3 would induce cytotoxic effects in STAT3-dependent head and neck squamous cell cancer (HNSCC) cells and would sensitize tumors to cisplatin.

DESIGN

Basic science. Two HNSCC cell lines, UM-SCC-29 and UM-SCC-74B, were characterized for cisplatin [cis-diammineplatinum(II) dichloride] sensitivity. Baseline expression of STAT3 and other apoptosis proteins was determined. The FLLL32 50% inhibitory concentration (IC(50)) dose was determined for each cell line, and the effect of FLLL32 treatment on the expression of phosphorylated STAT3 and other key proteins was elucidated. The antitumor efficacy of cisplatin, FLLL32, and combination treatment was measured. The proportion of apoptotic cells after cisplatin, FLLL32, or combination therapy was determined.

RESULTS

The UM-SCC-29 cell line is cisplatin resistant, and the UM-SCC-74B cell line is cisplatin sensitive. Both cell lines express STAT3, phosphorylated STAT3 (pSTAT3), and key apoptotic proteins. FLLL32 downregulates the active form of STAT3, pSTAT3, in HNSCC cells and induces a potent antitumor effect. FLLL32, alone or with cisplatin, increases the proportion of apoptotic cells. FLLL32 sensitized cisplatin-resistant cancer cells, achieving an equivalent tumor kill with a 4-fold lower dose of cisplatin.

CONCLUSIONS

FLLL32 monotherapy induces a potent antitumor effect and sensitizes cancer cells to cisplatin, permitting an equivalent or improved antitumor effect at lower doses of cisplatin. Our results suggest that FLLL32 acts by inhibiting STAT3 phosphorylation, reduced survival signaling, increased susceptibility to apoptosis, and sensitization to cisplatin.

Genome-wide methylation and expression differences in HPV(+) and HPV(-) squamous cell carcinoma cell lines are consistent with divergent mechanisms of carcinogenesis

Oncogenic human papillomaviruses (HPV) are associated with nearly all cervical cancers and are increasingly important in the etiology of oropharyngeal tumors. HPV-associated head and neck squamous cell carcinomas (HNSCC) have distinct risk profiles and appreciate a prognostic advantage compared to HPV-negative HNSCC. Promoter hypermethylation is widely recognized as a mechanism in the progression of HNSCC, but the extent to which this mechanism is consistent between HPV(+) and HPV(-) tumors is unknown. To investigate the epigenetic regulation of gene expression in HPV-induced and carcinogen-induced cancers, we examined genome-wide DNA methylation and gene expression in HPV(+) and HPV(-) SCC cell lines. We used two platforms: the Illumina Infinium Methylation BeadArray and tiling arrays, and confirmed illustrative examples with pyrosequencing and quantitative PCR. These analyses indicate that HPV(+) cell lines have higher DNA methylation in genic and LINE-1 regions than HPV(-) cell lines. Differentially methylated loci between HPV(+) and HPV(-) cell lines significantly correlated with HPV-typed HNSCC primary tumor DNA methylation levels. Novel findings include higher promoter methylation of polycomb repressive complex 2 target genes in HPV(+) cells compared to HPV(-) cells and increased expression of DNMT3A in HPV(+) cells. Additionally, CDKN2A and KRT8 were identified as interaction hubs among genes with higher methylation and lower expression in HPV(-) cells. Conversely, RUNX2, IRS-1 and CCNA1 were major hubs with higher methylation and lower expression in HPV(+) cells. Distinct HPV(+) and HPV(-) epigenetic profiles should provide clues to novel targets for development of individualized therapeutic strategies.

The poly(ADP-Ribose) polymerase inhibitor ABT-888 reduces radiation-induced nuclear EGFR and augments head and neck tumor response to radiotherapy

BACKGROUND AND PURPOSE

Current therapies for head and neck cancer frequently are not curative, necessitating novel therapeutic strategies. Thus, we studied whether inhibition of poly(ADP-Ribose) polymerase (PARP), a key DNA repair enzyme, could improve efficacy of radiotherapy in human head and neck cancer.

MATERIALS AND METHODS

UM-SCC1, UM-SCC5, UM-SCC6, and FaDu human head and neck cancer cellular susceptibility to the PARP inhibitor (PARPi) ABT-888 and/or radiation (IR) was assessed using colony formation assays. DNA damage was evaluated using the alkaline comet assay and immunostaining for γ-H2AX foci. Non-homologous end-joining (NHEJ) mediated repair was measured using phospho-DNA-Pk foci. Epidermal growth factor receptor (EGFR) location was assessed by immunostaining. Poly ADP-Ribose polymerization (PAR) levels were assessed using immunoblotting.

RESULTS

Human head and neck cancer cells exhibited enhanced cytotoxicity with IR and ABT-888 compared to either agent alone. This increased susceptibility correlated with reduced nuclear EGFR, attenuation of NHEJ, and persistence of DNA damage following IR. Interestingly, a subset of head and neck cancer cells which had elevated basal PAR levels was susceptible to PARPi alone.

CONCLUSIONS

Combining radiotherapy and PARP inhibition may improve outcomes and quality of life for head and neck cancer patients treated with radiotherapy. Furthermore, this novel strategy may also be feasible in other tumor types. Moreover, PAR levels should be investigated as a potential biomarker for tumor susceptibility to PARP inhibition.

ΔNp63 versatilely regulates a Broad NF-κB gene program and promotes squamous epithelial proliferation, migration, and inflammation

Head and neck squamous cell carcinoma (HNSCC) and many other epithelial malignancies exhibit increased proliferation, invasion, and inflammation, concomitant with aberrant nuclear activation of TP53 and NF-κB family members ΔNp63, cRel, and RelA. However, the mechanisms of cross-talk by which these transcription factors coordinate gene expression and the malignant phenotype remain elusive. In this study, we showed that ΔNp63 regulates a cohort of genes involved in cell growth, survival, adhesion, and inflammation, which substantially overlaps with the NF-κB transcriptome. ΔNp63 with cRel and/or RelA are recruited to form novel binding complexes on p63 or NF-κB/Rel sites of multitarget gene promoters. Overexpressed ΔNp63- or TNF-α-induced NF-κB and inflammatory cytokine interleukin-8 (IL-8) reporter activation depended on RelA/cRel regulatory binding sites. Depletion of RelA or ΔNp63 by small interfering RNA (siRNA) significantly inhibited NF-κB-specific, or TNF-α-induced IL-8 reporter activation. ΔNp63 siRNA significantly inhibited proliferation, survival, and migration by HNSCC cells in vitro. Consistent with these data, an increase in nuclear ΔNp63, accompanied by increased proliferation (Ki-67) and adhesion (β4 integrin) markers, and induced inflammatory cell infiltration was observed throughout HNSCC specimens, when compared with the basilar pattern of protein expression and minimal inflammation seen in nonmalignant mucosa. Furthermore, overexpression of ΔNp63α in squamous epithelial cells in transgenic mice leads to increased suprabasilar cRel, Ki-67, and cytokine expression, together with epidermal hyperplasia and diffuse inflammation, similar to HNSCC. Our study reveals ΔNp63 as a master transcription factor that, in coordination with NF-κB/Rels, orchestrates a broad gene program promoting epidermal hyperplasia, inflammation, and the malignant phenotype of HNSCC.

Radiosensitization of head and neck squamous cell carcinoma by a SMAC-mimetic compound, SM-164, requires activation of caspases

Chemoradiation is the treatment of choice for locally advanced head and neck squamous cell carcinoma (HNSCC). However, radioresistance, which contributes to local recurrence, remains a significant therapeutic problem. In this study, we characterized SM-164, a small second mitochondria-derived activator of caspase -mimetic compound that promotes degradation of cellular inhibitor of apoptosis-1(cIAP-1; also known as baculoviral IAP repeat-containing protein 2, BIRC2) and releases active caspases from the X-linked inhibitor of apoptosis inhibitory binding as a radiosensitizing agent in HNSCC cells. We found that SM-164 at nanomolar concentrations induced radiosensitization in some HNSCC cell lines in a manner dependent on intrinsic sensitivity to caspase activation and apoptosis induction. Blockage of caspase activation via short interfering RNA knockdown or a pan-caspase inhibitor, z-VAD-fmk, largely abrogated SM-164 radiosensitization. On the other hand, the resistant lines with a high level of Bcl-2 that blocks caspase activation and apoptosis induction became sensitive to radiation on Bcl-2 knockdown. Mechanistic studies revealed that SM-164 radiosensitization in sensitive cells was associated with NF-κB activation and TNFα secretion, followed by activation of caspase-8 and -9, leading to enhanced apoptosis. Finally, SM-164 also radiosensitized human tumor xenograft while causing minimal toxicity. Thus, SM-164 is a potent radiosensitizer via a mechanism involving caspase activation and holds promise for future clinical development as a novel class of radiosensitizer for the treatment of a subset of head and neck cancer patients.