P53 mutation correlates with cisplatin sensitivity in head and neck squamous cell carcinoma lines

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.

Gene silencing with siRNA targeting E6/E7 as a therapeutic intervention against head and neck cancer-containing HPV16 cell lines

CONCLUSION

Our results indicate that siRNA E6 and/or E7 may have potential as a gene-specific therapy for human papillomavirus (HPV) type 16 (HPV16)-related squamous cell carcinoma of the head and neck (HNSCC).

OBJECTIVES

To evaluate the effectiveness of siRNA targeting E6 and/or E7 on the in vitro and in vivo growth suppression of HPV16-related HNSCC.

METHODS

HPV16-related HNSCC (UM-SCC47) cell lines were used for the present study. Expression of HPV viral oncogenes E6 and/or E7 and their cellular targets, p53 and pRb, was evaluated by real-time PCR, Western blotting, and immunofluorescence staining. To study the effect of siRNA on tumor growth in vivo, we developed animal models. Representative tumors harvested from each group were processed for apoptosis analyses (TUNEL assay) and immunofluorescence staining for p53 and pRb.

RESULTS

E6 and E7 oncogenes of HPV16 were down-regulated by E6 and/or E7 targeting siRNAs, respectively. The expression of p53 and pRb proteins in both the E6 siRNA group and E7 siRNA group was up-regulated compared with those of control groups. The cellular proliferation and apoptosis indexes of E6 and/or E7 siRNA groups were higher than those of controls. In vivo studies showed significant inhibitory effect of E6 and/or E7 siRNA compared with those of control groups, which was consistent with in vitro studies.

DNA-bound platinum is the major determinant of cisplatin sensitivity in head and neck squamous carcinoma cells

PURPOSE

The combination of systemic cisplatin with local and regional radiotherapy as primary treatment of head and neck squamous cell carcinoma (HNSCC) leads to cure in approximately half of the patients. The addition of cisplatin has significant effects on outcome, but despite extensive research the mechanism underlying cisplatin response is still not well understood.

METHODS

We examined 19 HNSCC cell lines with variable cisplatin sensitivity. We determined the TP53 mutational status of each cell line and investigated the expression levels of 11 potentially relevant genes by quantitative real-time PCR. In addition, we measured cisplatin accumulation and retention, as well as the level of platinum-DNA adducts.

RESULTS

We found that the IC50 value was significantly correlated with the platinum-DNA adduct levels that accumulated during four hours of cisplatin incubation (p = 0.002). We could not find a significant correlation between cisplatin sensitivity and any of the other parameters tested, including the expression levels of established cisplatin influx and efflux transporters. Furthermore, adduct accumulation did not correlate with mRNA expression of the investigated influx pumps (CTR1 and OCT3) nor with that of the examined DNA repair genes (ATR, ATM, BRCA1, BRCA2 and ERCC1).

CONCLUSION

Our findings suggest that the cisplatin-DNA adduct level is the most important determinant of cisplatin sensitivity in HNSCC cells. Imaging with radio-labeled cisplatin might have major associations with outcome.

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.

YM155 reverses cisplatin resistance in head and neck cancer by decreasing cytoplasmic survivin levels

Cisplatin is one of the commonly used chemotherapeutic drugs for the treatment of head and neck squamous cell carcinoma (HNSCC). However, acquisition of cisplatin resistance is common in patients with HNSCC, and it often leads to local and distant failure. In this study, we showed that survivin expression is significantly upregulated in HNSCC primary tumors and cell lines. In addition, survivin levels were significantly higher in human papilloma virus-negative patients that normally respond poorly to cisplatin treatment. Survivin expression was further increased in cisplatin-resistant cells (CAL27-CisR) as compared with its parent cells (CAL27). Therefore, we hypothesized that targeting of survivin in HNSCC could reverse the resistant phenotype in tumor cells, thereby enhancing the therapeutic efficacy of cisplatin. We used both in vitro and in vivo models to test the efficacy of YM155, a small molecule survivin inhibitor, either as a single agent or in combination with cisplatin. YM155 significantly decreased survivin levels and cell proliferation in a dose-dependent manner. In addition, YM155 pretreatment significantly reversed cisplatin resistance in cancer cells. Interestingly, YM155 treatment altered the dynamic localization of survivin in cells by inducing a rapid reduction in cytoplasmic survivin, which plays a critical role in its antiapoptotic function. In a severe combined immunodeficient mouse xenograft model, YM155 significantly enhanced the antitumor and antiangiogenic effects of cisplatin, with no added systemic toxicity. Taken together, our results suggest a potentially novel strategy to use YM155 to overcome the resistance in tumor cells, thereby enhancing the effectiveness of the chemotherapy in HNSCC.

Dysregulation of microRNA-34a expression in head and neck squamous cell carcinoma promotes tumor growth and tumor angiogenesis

BACKGROUND

MicroRNAs (miRs) are small non-coding RNAs that play an important role in cancer development where they can act as oncogenes or as tumor-suppressors. miR-34a is a tumor-suppressor that is frequently downregulated in a number of tumor types. However, little is known about the role of miR-34a in head and neck squamous cell carcinoma (HNSCC).

METHODS AND RESULTS

miR-34a expression in tumor samples, HNSCC cell lines and endothelial cells was examined by real time PCR. Lipofectamine-2000 was used to transfect miR-34a in HNSCC cell lines and human endothelial cells. Cell-proliferation, migration and clonogenic survival was examined by MTT, Xcelligence system, scratch assay and colony formation assay. miR-34a effect on tumor growth and tumor angiogenesis was examined by in vivo SCID mouse xenograft model. Our results demonstrate that miR-34a is significantly downregulated in HNSCC tumors and cell lines. Ectopic expression of miR-34a in HNSCC cell lines significantly inhibited tumor cell proliferation, colony formation and migration. miR-34a overexpression also markedly downregulated E2F3 and survivin levels. Rescue experiments using microRNA resistant E2F3 isoforms suggest that miR-34a-mediated inhibition of cell proliferation and colony formation is predominantly mediated by E2F3a isoform. In addition, tumor samples from HNSCC patients showed an inverse relationship between miR-34a and survivin as well as miR-34a and E2F3 levels. Overexpression of E2F3a completely rescued survivin expression in miR-34a expressing cells, thereby suggesting that miR-34a may be regulating survivin expression via E2F3a. Ectopic expression of miR-34a also significantly inhibited tumor growth and tumor angiogenesis in a SCID mouse xenograft model. Interestingly, miR-34a inhibited tumor angiogenesis by blocking VEGF production by tumor cells as well as directly inhibiting endothelial cell functions.

CONCLUSIONS

Taken together, these findings suggest that dysregulation of miR-34a expression is common in HNSCC and modulation of miR34a activity might represent a novel therapeutic strategy for the treatment of HNSCC.

Individualizing antimetabolic treatment strategies for head and neck squamous cell carcinoma based on TP53 mutational status

BACKGROUND

Mutations in the tumor protein 53 (TP53) tumor suppressor gene are common in head and neck squamous cell carcinoma (HNSCC) and correlate with radioresistance. Currently, there are no clinically available therapeutic approaches targeting p53 in HNSCC. In this report, the authors propose a strategy that uses TP53 mutational status to individualize antimetabolic strategies for the potentiation of radiation toxicity in HNSCC cells.

METHODS

Glycolytic flux and mitochondrial respiration were evaluated in wild-type (wt) and mutant (mut) TP53 HNSCC cell lines. Sensitivity to external-beam radiation (XRT) was measured using a clonogenic assay.

RESULTS

HNSCC cells that expressed mutTP53 demonstrated radioresistance compared with HNSCC cells that expressed wtTP53. Glycolytic inhibition potentiated radiation toxicity in mutTP53-expressing, but not wtTP53-expressing, HNSCC cells. The relative sensitivity of mutTP53 HNSCC cells to glycolytic inhibition was caused by a glycolytic dependence associated with decreased mitochondrial complex II and IV activity. The wtTP53-expressing cells maintained mitochondrial reserves and were relatively insensitive to glycolytic inhibition. Inhibition of respiration using metformin increased glycolytic dependence in wtTP53-expressing cells and potentiated the effects of glycolyic inhibition on radiation toxicity.

CONCLUSIONS

TP53 mutation in HNSCC cells was correlated with a metabolic shift away from mitochondrial respiration toward glycolysis, resulting in increased sensitivity to the potentiating effects of glycolytic inhibition on radiation toxicity. In contrast, wtTP53-expressing cells required inhibition of both mitochondrial respiration and glycolysis to become sensitized to radiation. Therefore, the authors concluded that TP53 mutational status may be used as a marker of altered tumor cell metabolism to individualize HNSCC treatment selection of specific, targeted metabolic agents that can overcome cellular resistance to radiation therapy.

Resistance and gain-of-resistance phenotypes in cancers harboring wild-type p53

Chemotherapy is the bedrock for the clinical management of cancer, and the tumor suppressor p53 has a central role in this therapeutic modality. This protein facilitates favorable antitumor drug response through a variety of key cellular functions, including cell cycle arrest, senescence, and apoptosis. These functions essentially cease once p53 becomes mutated, as occurs in ∼50% of cancers, and some p53 mutants even exhibit gain-of-function effects, which lead to greater drug resistance. However, it is becoming increasingly evident that resistance is also seen in cancers harboring wild-type p53. In this review, we discuss how wild-type p53 is inactivated to render cells resistant to antitumor drugs. This may occur through various mechanisms, including an increase in proteasomal degradation, defects in post-translational modification, and downstream defects in p53 target genes. We also consider evidence that the resistance seen in wild-type p53 cancers can be substantially greater than that seen in mutant p53 cancers, and this poses a far greater challenge for efforts to design strategies that increase drug response in resistant cancers already primed with wild-type p53. Because the mechanisms contributing to this wild-type p53 "gain-of-resistance" phenotype are largely unknown, a concerted research effort is needed to identify the underlying basis for the occurrence of this phenotype and, in parallel, to explore the possibility that the phenotype may be a product of wild-type p53 gain-of-function effects. Such studies are essential to lay the foundation for a rational therapeutic approach in the treatment of resistant wild-type p53 cancers.

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.

Differential biomarker expression in head and neck cancer correlates with anatomical localization

We tested the expression of known (p16(ink4), Ki67, p53, EGFR) and a new immunohistochemical (collagen XVII/BP180) biomarker in head and neck squamous cell carcinomas (SCC) of diverse anatomical localization. Tissue microarrays (TMA) of 124 SCC were created, immunostained, and analyzed following whole slide digitalization using the Pannoramic Scan and the TMA Module software (3DHISTECH Kft, Budapest, Hungary). Statistical analysis of scoring results was carried out using Pearson's chi-square test. We observed the significant elevation of p16(ink4) and Ki67 expression in supraglottic, tonsillar and tonsillo-lingual SCCs compared to those affecting the oral cavity, oropharynx without tonsils, larynx without supraglottis and the hypopharynx. This differential antigen expression may reflect the diverse route of embryologic differentiation followed by the affected regions except those of the tonsils and the supraglottis which show similar antigenic pattern but diverse developmental path. All the other biomarkers tested including p53, collagen XVII and EGFR were detected in the majority of cancers including high grade cases, but did not reveal any significant regional difference. Based on our results oropharyngeal squamous cell carcinomas may not be regarded as one entity. Concerning the oral cavity and the oropharynx, cancers affecting the tonsils (palatine and lingual) show significantly elevated p16(ink4) and Ki67 expression; so as the cancers of the supraglottis compared to the rest of larynx. Consequently, tonsillar and supraglottic cancers show similar biomarker profiles. Correlation of differential biomarker expression with diverse biological behavior in head and neck cancers need further investigations.

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.

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.

Current potential and limitations of molecular diagnostic methods in head and neck cancer

Traditional diagnostic methods such as clinical assessment, histopathological examination and imaging techniques are limited in their capacity to provide information on prognosis and treatment choice of head and neck cancer. In recent years, molecular techniques have been developed that enabled us to get more insight into the molecular biological cellular pathways underlying tumor progression and metastasis. Correlation of these molecular changes with clinical events has been explored. However, consistently useful markers have not been identified yet, although many promising developments are in progress. It may be expected that in the near future, molecular markers will be useful for clinical purposes. In this paper, an overview will be given of the several molecular techniques that may have potential to be introduced in clinical practice in the management of head and neck squamous cell carcinoma.

Hyperphosphorylation of replication protein A in cisplatin-resistant and -sensitive head and neck squamous cell carcinoma cell lines

BACKGROUND

Resistance to chemotherapy is a major limitation in the treatment of head and neck squamous cell carcinomas (HNSCCs), accounting for high mortality rates in patients. Here, we investigated the role of replication protein A (RPA) in cisplatin and etoposide resistance.

METHODS

We used 6 parental HNSCC cell lines. We also generated 1 cisplatin-resistant progeny subline from a parental cisplatin-sensitive cell line, to examine cisplatin resistance and sensitivity with respect to RPA2 hyperphosphorylation and cell-cycle response.

RESULTS

Cisplatin-resistant HNSCC cell levels of hyperphosphorylated RPA2 in response to cisplatin were 80% to 90% greater compared with cisplatin-sensitive cell lines. RPA2 hyperphosphorylation could be induced in the cisplatin-resistant HNSCC subline. The absence of RPA2 hyperphosphorylation correlated with a defect in cell-cycle progression and cell survival.

CONCLUSION

Loss of RPA2 hyperphosphorylation occurs in HNSCC cells and may be a marker of cellular sensitivities to cisplatin and etoposide in HNSCC.

Cell cycle arrest and apoptosis in TP53 subtypes of bladder carcinoma cell lines treated with cisplatin and gemcitabine

Currently, the combination of cisplatin and gemcitabine is considered a standard chemotherapeutic protocol for bladder cancer. However, the mechanism by which these drugs act on tumor cells is not completely understood. The aim of the present study was to investigate the effects of these two antineoplastic drugs on the apoptotic index and cell cycle kinetics of urinary bladder transitional carcinoma cell lines with wild-type or mutant TP53 (RT4: wild type for TP53; 5637 and T24: mutated TP53). Cytotoxicity, cell survival assays, clonogenic survival assays and flow cytometric analyses for cell cycle kinetics and apoptosis detection were performed with three cell lines treated with different concentrations of cisplatin and gemcitabine. G1 cell cycle arrest was observed in the three cell lines after treatment with gemcitabine and gemcitabine plus cisplatin. A significant increase in cell death was also detected in all cell lines treated with cisplatin or gemcitabine. Lower survival rates occurred with the combined drug protocol independent of TP53 status. TP53-wild type cells (RT4) were more sensitive to apoptosis than were mutated TP53 cells when treated with cisplatin or gemcitabine. Concurrent treatment with cisplatin and gemcitabine was more effective on transitional carcinoma cell lines than either drug alone; the drug combination led to a decreased cell survival that was independent of TP53 status. Therefore, the synergy between low concentrations of cisplatin and gemcitabine may have clinical relevance, as high concentrations of each individual drug are toxic to whole organisms.

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

BACKGROUND

We established multiple University of Michigan Squamous Cell Carcinoma (UM-SCC) cell lines. With time, these have been distributed to other labs all over the world. Recent scientific discussions have noted the need to confirm the origin and identity of cell lines in grant proposals and journal articles. We genotyped the UM-SCC cell lines in our collection to confirm their unique identity.

METHOD

Early-passage UM-SCC cell lines were genotyped and photographed.

RESULTS

Thus far, 73 unique head and neck UM-SCC cell lines (from 65 donors, including 21 lines from 17 females) were genotyped. In 7 cases, separate cell lines were established from the same donor.

CONCLUSIONS

These results will be posted on the UM Head and Neck SPORE Tissue Core website for other investigators to confirm that the UM-SCC cells used in their laboratories have the correct features. Publications using UM-SCC cell lines should confirm the genotype.

Molecular techniques and genetic alterations in head and neck cancer

It is well known that cellular DNA alterations can lead to the formation of cancer, and there has been much discovery in the pathways involved in the development of head and neck squamous cell carcinoma (HNSCC). With novel genome-wide molecular assays, our ability to detect these abnormalities has increased. We now have a better understanding of the molecular complexity of HNSCC, but there is still much research to be done. In this review, we discuss the well described genetic alterations and touch on the newer findings, as well as some of the future directions of head and neck cancer research.

Galanin receptor subtype 2 suppresses cell proliferation and induces apoptosis in p53 mutant head and neck cancer cells

PURPOSE

Galanin and its three receptors (GALR1-3) are expressed in many normal tissues, but silenced in some tumors. Contradictory roles for galanin and its receptors in various tumors have been reported. To understand their function, investigations of individual galanin receptors are necessary. In head and neck squamous carcinoma cells (HNSCC) with silenced GALR1 and GALR2, we showed that reexpressed GALR1 suppresses tumor cell proliferation via Erk1/2-mediated effects on cdk inhibitors and cyclin D1. Others showed that GALR2 could induce apoptosis in neuroblastoma cells with wild-type p53, whereas GALR2 stimulated proliferation in small cell lung cancer. In this study, we investigated the role of GALR2 in HNSCC cells that have mutant p53 and do not express GALR1.

EXPERIMENTAL DESIGN

UM-SCC-1, a human oral carcinoma cell line with a splice site mutation causing a 46-bp p53 off-frame deletion, was stably transfected to express GALR2 (UM-SCC-1-GALR2).

RESULTS

Galanin treatment of UM-SCC-1-GALR2 caused morphologic changes and a marked decrease in cell number that were not observed in UM-SCC-1-mock cells. Galanin and GALR2 resulted in decreased bromodeoxyuridine incorporation, p27(Kip1) and p57(Kip2) up-regulation, and decreased cyclin D1 expression. These effects were similar to GALR1 signaling in HNSCC, but GALR2 also induced caspase-3-dependent apoptosis, which was confirmed by Annexin-V staining and DNA fragmentation analysis. These were not observed with GALR1.

CONCLUSION

This study shows that GALR2 reexpression can inhibit cell proliferation and induce apoptosis in HNSCC cells with mutant p53. GALR2 may be a feasible target for HNSCC therapy.

EGFR, p16, HPV Titer, Bcl-xL and p53, sex, and smoking as indicators of response to therapy and survival in oropharyngeal cancer

PURPOSE

To prospectively identify markers of response to therapy and outcome in an organ-sparing trial for advanced oropharyngeal cancer.

PATIENTS AND METHODS

Pretreatment biopsies were examined for expression of epidermal growth factor receptor (EGFR), p16, Bcl-xL, and p53 as well as for p53 mutation. These markers were assessed for association with high-risk human papillomavirus (HPV), response to therapy, and survival. Patient variables included smoking history, sex, age, primary site, tumor stage, and nodal status.

RESULTS

EGFR expression was inversely associated with response to induction chemotherapy (IC) (P = .01), chemotherapy/radiotherapy (CRT; P = .055), overall survival (OS; P = .001), and disease-specific survival (DSS; P = .002) and was directly associated with current smoking (P = .04), female sex (P = .053), and lower HPV titer (P = .03). HPV titer was significantly associated with p16 expression (P < .0001); p16 was significantly associated with response to IC (P = .008), CRT (P = .009), OS (P = .001), and DSS (P = .003). As combined markers, lower HPV titer and high EGFR expression were associated with worse OS (rho(EGFR) = 0.008; rho(HPV) = 0.03) and DSS (rho(EGFR) = 0.01; rho(HPV) = 0.016). In 36 of 42 biopsies, p53 was wild-type, and only one HPV-positive tumor had mutant p53. The combination of low p53 and high Bcl-xL expression was associated with poor OS (P = .005) and DSS (P = .002).

CONCLUSION

Low EGFR and high p16 (or higher HPV titer) expression are markers of good response to organ-sparing therapy and outcome, whereas high EGFR expression, combined low p53/high Bcl-xL expression, female sex, and smoking are associated with a poor outcome. Smoking cessation and strategies to target EGFR and Bcl-xL are important adjuncts to the treatment of oropharyngeal cancer.

Induction of cell cycle arrest and apoptosis by 5-fluorouracil in laryngeal cancer cells containing HPV16 E6 and E7 oncoproteins

OBJECTIVE

To investigate the cytotoxic effect of 5-fluorouracil (5Fu) on HPV16-associated laryngeal cancer cells.

DESIGN AND METHODS

Cytotoxicity assay and TUNEL assay were used to assess the effect of 5Fu on laryngeal cancer cells transfected with HPV16 E6 or E7.

RESULTS

5Fu induced apoptosis in the cells either with or without HPV16 in a dose- and time-dependent manner. 5Fu caused the accumulation of active pRb and p21(WAF1/CIP1), together with an increase in Bak and Bax expression and a decrease in Bcl-2 levels in all the transfected cells. G(1)/S phase cell cycle arrest was associated with the antiproliferation activity of 5Fu. 5Fu also presented some effects on the E6 and E7 oncoproteins.

CONCLUSIONS

HPV16 E6 and E7 oncoproteins do not prevent 5Fu-medicated apoptosis and G(1)/S cell arrest in laryngeal cancers. The sensitivity of 5Fu treatment is associated with the decrease of Bcl-2 and/or the increase in Bak and p21(WAFI/CIP1).

Inhibition of apoptosis in human laryngeal cancer cells by E6 and E7 oncoproteins of human papillomavirus 16

The carcinogenesis of human papillomaviruses type 16 (HPV-16) is mainly due to its two oncoproteins, E6 and E7. Their carcinogenic features in term of their relationship with Bcl-2 family are still unclear. We thus aimed to analyze the expression of Bcl-2 family members, Bcl-2, Bax, and Bak in laryngeal cancer cells transfected with the E6 or E7 and to determine the sensitivity of these cells to apoptotic stimuli. We employed two human laryngeal cancer cell lines, UMSCC12 and UMSCC11A in this study. These two cell lines were stably transfected with HPV16 E6, E7 or empty vector, pcDNA3.1. We found that E6 and E7 inhibited apoptosis induced by TNF-alpha/CHX in both UMSCC11A and UMSCC12 cells, enhanced the stability of Bcl-2 protein and increased the degradation of Bak protein. Furthermore, it was found that HPV-16 E7 statistically enhanced the expression of Bcl-2 in laryngeal cancer. The alteration of Bak by E6 and E7 was not through the influence on the Bak promoter, as the luciferase assay showed that neither E6 nor E7 changed the Bak promoter activity. We conclude that the evasion of apoptosis mediated by HPV-16 E6 and E7 is associated with increased Bcl-2 and decreased Bak in laryngeal carcinogenesis and that the decreased level of Bak by E6 and E7 is not caused by the regulation of the Bak promoter but by reducing its protein stability.

Alterations in the p53 pathway and their association with radio- and chemosensitivity in head and neck squamous cell carcinoma

Chemotherapy and/or radiotherapy are established measures in treatment protocols of head and neck squamous cell carcinoma (HNSCC). However, we still lack reliable predictive markers for the response to radio- and chemotherapy. The p53 pathway is involved in stress response and thus might influence chemo-/radiosensitivity. Using 29 HNSCC cell lines previously characterized for p53 mutations, we simultaneously analyzed several key players in the p53 pathway by RT-PCR, transcript sequencing and immunohistochemistry, and investigated their association with chemosensitivity and radiosensitivity. Cell lines with p53 mutations were slightly more sensitive to cisplatin than those with wild-type p53. The type of mutation did not influence radio- or chemosensitivity. p14(ARF), an activator of p53, was lost or mutated in all cell lines. Three cell lines showed overexpression of HDM-2, a major negative regulator of p53; however, HDM-2 levels did not correlate with radio- or chemosensitivity. HPV-16 oncoproteins were detected in one highly chemoresistant cell line. Our findings suggest that molecular events resulting in the inactivation of the p53 pathway occur in all HNSCC cell lines. However, single alterations in the p53 pathway are not reliable predictors for the response to radio- or chemotherapy in HNSCC.

Polymorphism of FGFR4 in cancer development and sensitivity to cisplatin and radiation in head and neck cancer

The aim of this study was to investigate the predisposition of the FGFR4 Gly/Arg polymorphism for development of head and neck squamous cell carcinoma (HNSCC) and, furthermore, to examine if the FGFR4 Arg(388) allele can be associated with resistance to chemo- and radiotherapy. When analysing 110 tumour biopsies a significant 1.7-fold increased risk to develop HNSCC in individuals carrying the Gly(388) allele (p=0.026) was found. Moreover a 2-fold increased risk for males harbouring the Gly(388) allele (p=0.031) to develop HNSCC was detected. In 39 HNSCC cell lines the role of the Arg(388) allele for radiation and cisplatin sensitivity was investigated. Our results show no role of the Arg(388) allele for the radiosensitivity (p=0.996) but indicate a tendency to increased cisplatin sensitivity (p=0.141). When screening the transmembrane and kinase domains in the FGFR4 gene a novel mutation, probably generating a truncated protein lacking exons 14-18, was found in six of eight selected cell lines. Taken together, we have here identified a marker that predicts the risk to develop HNSCC and possibly the sensitivity to cisplatin as well as a novel mutation in the FGFR4 gene.

Expression of p53 and Bcl-xL as predictive markers for larynx preservation in advanced laryngeal cancer

OBJECTIVE

To assess tumor markers in advanced laryngeal cancer.

DESIGN

Marker expression and clinical outcome.

PATIENTS

Pretreatment tumor biopsy specimens were analyzed from patients enrolled in the Department of Veterans Affairs Laryngeal Cancer Study.

MAIN OUTCOME MEASURES

Expression of p53 (OMIM TP53) and Bcl-xL (OMIM 600039) in pretreatment biopsy specimens was assessed for correlation with chemotherapy response, laryngeal preservation, and survival.

RESULTS

Higher rates of larynx preservation were observed in patients whose tumors expressed p53 vs those that did not (80% [36 of 45 patients] vs 59% [24 of 41 patients], P =.03). Higher rates of larynx preservation were also observed in patients whose tumors expressed low levels of Bcl-xL vs high levels of Bcl-xL (90% [18 of 20 patients] vs 60% [30 of 50 patients], P =.02). Patients were categorized into 3 risk groups (low, intermediate, and high) based on their tumor p53 and Bcl-xL expression status. Patients whose tumors had the high-risk biomarker profile (low p53 expression and high Bcl-xL expression) were less likely to preserve their larynx than patients whose tumors had the intermediate-risk biomarker profile (high p53 expression and low or high Bcl-xL expression) or the low-risk biomarker profile (low p53 expression and low Bcl-xL expression). The larynx preservation rates were 100% (10 of 10 patients), 77% (26 of 34 patients), and 54% (7 of 13 patients) for the low-risk, intermediate-risk, and high-risk groups, respectively (P =.04, Fisher exact test).

CONCLUSION

Tumor expression of p53 and Bcl-xL is a strong predictor of successful larynx preservation in patients treated with induction chemotherapy and followed by radiation therapy in responding tumors.

A signal network involving coactivated NF-kappaB and STAT3 and altered p53 modulates BAX/BCL-XL expression and promotes cell survival of head and neck squamous cell carcinomas

Abrogation of apoptosis to sustain cell survival is an essential step in development of cancer. Aberrant activation of signal transcription factors NF-kappaB or STAT3, alterations in p53 status, or BCL/BAX family expression have each been reported to affect cell survival in cancer, including head and neck squamous cell carcinomas (HNSCC). However, molecular targeting of these alterations individually has yielded disappointing results. In our study, we examined the hypothesis that alterations in a signal network involving NF-kappaB, STAT3 and p53 modulates expression of proapoptotic BAX and antiapoptotic BCL-XL proteins, and promotes cell survival of HNSCC. We found that NF-kappaB and STAT3 are coactivated together, and with cytokine stimulation or siRNA knock-down, both modulate BAX/BCL-XL. Greater modulation among HNSCC lines expressing low wt p53 than those over-expressing mt p53 protein suggested that decreased p53 expression might enhance activation of NF-kappaB, STAT3 and BCL-XL. Reexpression of wt p53 suppressed NF-kappaB and STAT3 nuclear binding activity, and BCL-XL expression, while inducing p21 and BAX. Over-expression of p53 together with inhibition of NF-kappaB or STAT3 induced greater increase in the BAX/BCL-XL ratio and apoptosis than modulation of these transcription factors individually. Conversely, NF-kappaB or STAT3 inducing cytokines decreased the BAX/BCL-XL ratio. Thus, a network involving signal coactivation of NF-kappaB and STAT3, differentially modified by p53 inactivation or mutation, promotes altered BAX/BCL-XL expression and cell survival in HNSCC. Inhibition of signal activation of both NF-kappaB and STAT3 together with reexpression of p53 could be the most effective strategy to restore BAX/BCL-XL regulation and for cytotoxic therapy of HNSCC.

Systems biology-defined NF-kappaB regulons, interacting signal pathways and networks are implicated in the malignant phenotype of head and neck cancer cell lines differing in p53 status

BACKGROUND

Aberrant activation of the nuclear factor kappaB (NF-kappaB) pathway has been previously implicated as a crucial signal promoting tumorigenesis. However, how NF-kappaB acts as a key regulatory node to modulate global gene expression, and contributes to the malignant heterogeneity of head and neck cancer, is not well understood.

RESULTS

To address this question, we used a newly developed computational strategy, COGRIM (Clustering Of Gene Regulons using Integrated Modeling), to identify NF-kappaB regulons (a set of genes under regulation of the same transcription factor) for 1,265 genes differentially expressed by head and neck cancer cell lines differing in p53 status. There were 748 NF-kappaB targets predicted and individually annotated for RELA, NFkappaB1 or cREL regulation, and a prevalence of RELA related genes was observed in over-expressed clusters in a tumor subset. Using Ingenuity Pathway Analysis, the NF-kappaB targets were reverse-engineered into annotated signature networks and pathways, revealing relationships broadly altered in cancer lines (activated proinflammatory and down-regulated Wnt/beta-catenin and transforming growth factor-beta pathways), or specifically defective in cancer subsets (growth factors, cytokines, integrins, receptors and intermediate kinases). Representatives of predicted NF-kappaB target genes were experimentally validated through modulation by tumor necrosis factor-alpha or small interfering RNA for RELA or NFkappaB1.

CONCLUSION

NF-kappaB globally regulates diverse gene programs that are organized in signal networks and pathways differing in cancer subsets with distinct p53 status. The concerted alterations in gene expression patterns reflect cross-talk among NF-kappaB and other pathways, which may provide a basis for molecular classifications and targeted therapeutics for heterogeneous subsets of head and neck or other cancers.

Phenylbutyrate interferes with the Fanconi anemia and BRCA pathway and sensitizes head and neck cancer cells to cisplatin

Background

Cisplatin has been widely used to treat head and neck cancer. One of the clinical limitations with this treatment, however, is that tumors that are initially responsive to cisplatin later acquire resistance. We have recently shown that a subset of head and neck cancer cell lines has a defective Fanconi anemia DNA damage response pathway and this defect correlates to cisplatin sensitivity. We have also shown that the histone deacetylase inhibitor phenylbutyrate sensitize human cells to cisplatin. In this study we explored whether phenylbutyrate may sensitize head and neck cancer cells by interfering with the Fanconi anemia pathway.

Results

We found that the phenylbutyrate sensitizes head and neck cancer cell lines to cisplatin. This sensitization by phenylbutyrate correlated to a significant decrease in the formation of cisplatin-induced FANCD2 nuclear foci, which is a functional read out of the Fanconi anemia and BRCA (FA/BRCA) pathway. This abrogation of the FA/BRCA pathway by phenylbutyrate was not due to loss of FANCD2 monoubiquitylation but rather correlated to a phenylbutyrate-mediated reduction in the expression of the BRCA1 protein. Furthermore, we found that cancer cells defective in the FA pathway were also sensitized to cisplatin by phenylbutyrate suggesting that phenylbutyrate targets additional pathways.

Conclusion

The results from this study suggest that phenylbutyrate may have therapeutic utility as a cisplatin sensitizer in head and neck cancer by inhibiting the FA/BRCA pathway through the down regulation of BRCA1 as well as by an FA/BRCA-independent mechanism.

Deficient TP53 expression, function, and cisplatin sensitivity are restored by quinacrine in head and neck cancer

PURPOSE

To determine the nature and potential pharmacologic reversibility of deficient TP53 expression and function in head and neck squamous cell carcinomas (HNSCC) with wild-type TP53, previously associated with decreased sensitivity to cisplatin therapy.

EXPERIMENTAL DESIGN

TP53 genotype, mRNA and protein expression, TP53-induced p21 expression, and TP53 DNA-binding and reporter gene function were determined in a panel of nine previously characterized HNSCC cell lines from the University of Michigan squamous cell carcinoma (UM-SCC) series. The genotoxic drug doxorubicin and the anti-inflammatory and antimalarial drug quinacrine, previously identified as inducers of TP53, were used to examine the nature and potential reversibility of deficient TP53 expression and function. The specific role of inducible TP53 on function and cellular proliferation was confirmed using selective TP53 inhibitor pifithrin-alpha or short hairpin RNA knockdown. The capability of quinacrine to sensitize HNSCC to the cytotoxic effects of cisplatin was assessed.

RESULTS

UM-SCC cell lines with wild-type TP53 genotype underexpressed TP53 mRNA and protein when compared with normal human keratinocytes or UM-SCC with mutant TP53. Although doxorubicin failed to induce TP53 expression or functional activity, quinacrine induced TP53 mRNA and protein expression, increased TP53 reporter activity and p21 protein expression, and induced growth inhibition in these wild-type TP53 cell lines. Quinacrine-induced TP53 reporter activity and growth suppression were attenuated by pifithrin-alpha and TP53 short hairpin RNA knockdown. Furthermore, quinacrine sensitized UM-SCC to cisplatin in vitro.

CONCLUSIONS

Deficient TP53 mRNA and protein expression underlies decreased function in a subset of HNSCC with wild-type TP53 and can be restored together with cisplatin sensitization by quinacrine.

The Role of the NF-kappaB Transcriptome and Proteome as Biomarkers in Human Head and Neck Squamous Cell Carcinomas

NF-kappaB is a family of signal activated transcription factors comprised of hetero- or homo-dimers from 5 different subunits, NF-kappaB1, NF-kappaB2, RELA, cREL and RELB. NF-kappaBs normally are transiently activated in response to infection or injury, but in cancers are aberrantly activated, regulating a transcriptome of hundreds of genes and corresponding proteome that promote pathogenesis and therapeutic resistance. In head and neck squamous cell carcinomas, an important role of NF-kappaB in regulation of the altered transcriptome and proteome has been established, providing a catalog of activating and target genes and proteins that may be useful as biomarkers of alterations in this pathway for this and other cancers. An emerging appreciation that NF-kappaB and other signal pathways form an altered regulatory network highlights the need to use biomarkers and combine targeted agents for personalized therapy of cancer.

A novel nuclear factor-kappaB gene signature is differentially expressed in head and neck squamous cell carcinomas in association with TP53 status

PURPOSE

To determine if gene signatures differentially expressed in head and neck squamous cell carcinomas (HNSCC) are related to alterations in transcription factors nuclear factor-kappaB (NF-kappaB) and TP53 previously associated with decreased cell death, response to therapy, and worse prognosis.

EXPERIMENTAL DESIGN

Unique gene signatures expressed by HNSCC lines were identified by cDNA microarray, principal components, and cluster analyses and validated by quantitative reverse transcription-PCR (RT-PCR) and in situ hybridization. Bioinformatic analysis of the promoters and ontogeny of these clustered genes was done. Expression of proteins encoded by genes of a putative NF-kappaB signature, NF-kappaB p65, and TP53 were examined in HNSCC tissue specimens by immunostaining. Predicted promoter binding and modulation of expression of candidate NF-kappaB genes and cell survival were evaluated by p65 chromatin immunoprecipitation (ChIP) and small interfering RNA (siRNA) knockdown.

RESULTS

Two groups of HNSCC exhibiting distinct gene signatures were identified: cluster A enriched for histone genes, with a higher prevalence of TP53 promoter binding motifs; and cluster B enriched for injury response genes with NF-kappaB regulatory motifs. Coexpression of cluster B proteins was observed with strong NF-kappaB phospho-p65 and weak TP53 staining, and NF-kappaB phospho-p65 was inversely associated with TP53 (P = 0.02). Promoter binding of the NF-kappaB signature genes was confirmed by p65 ChIP, and down-modulation of their expression and cell death were induced by p65 siRNA.

CONCLUSION

NF-kappaB promotes expression of a novel NF-kappaB-related gene signature and cell survival in HNSCC that weakly express TP53, a subset previously associated with inactivated wild-type TP53, greater resistance to chemoradiotherapy, and worse prognosis.

Loss of p53 expression correlates with metastatic phenotype and transcriptional profile in a new mouse model of head and neck cancer

Squamous cell carcinoma of the head and neck (HNSCC) is the sixth most frequent cancer worldwide. Because HNSCC is largely acquired by environmental carcinogen exposure rather than through germ line mutations, there are no known familial forms of the disease in humans nor are there inbred rodent strains prone to spontaneous head and neck tumors. Transgenic animals with inactivation of tumor suppressor genes commonly mutated in human cases of HNSCC provide attractive models for studying the pathogenesis of head and neck cancer. p53 is the most frequently inactivated tumor suppressor gene in HNSCC. We used a chemical induction protocol in mice heterozygous for the p53 gene to evaluate how p53 inactivation contributed to head and neck carcinogenesis the mouse model. Metastatic squamous cell carcinomas developed in 100% of animals. Histopathologically, the tumors ranged from well to poorly differentiated and showed many molecular features of human HNSCC. Mice carrying only one p53 allele developed tumors with significantly reduced latency compared with wild-type controls (average, 18 versus 22 weeks). Metastatic cancer cells showed complete loss of p53 expression when compared with primary tumors. Transcriptional profiling showed not only distinct genetic differences between primary and metastatic tumors, but also when cancers from heterozygous null and wild-type animals were compared. Our results provide novel insights into the molecular genetics of tumor progression in head and neck cancer.

Identification of angiogenesis/metastases genes predicting chemoradiotherapy response in patients with laryngopharyngeal carcinoma

PURPOSE

To identify genes related to angiogenesis/metastasis that predict locoregional failure in patients with laryngopharyngeal cancer (LPC) undergoing chemoradiotherapy (CRT) treatment.

METHODS

Tumor tissue was collected and snap-frozen from 35 sequential patients with histologically confirmed LPC being treated with CRT. Gene expression analysis was performed using a novel cDNA array consisting of 277 genes functionally associated with angiogenesis (n = 152) and/or metastasis (n = 125). Locoregional response was correlated to the gene expression profiles to identify genes associated with outcome. These genes were internally validated by real-time reverse transcriptase polymerase chain reaction (RT-PCR) and validated externally by immunohistochemistry analysis on an independent set of patients.

RESULTS

Locoregional failure occurred in nine of 35 patients. Seventeen genes from the cDNA microarray correlated with locoregional failure (two-sample t test, P < .05). Seven genes were chosen for additional analysis based on the availability of antibodies for immunohistochemistry. Of these seven genes, real-time RT-PCR validated four genes: MDM2, VCAM-1, erbB2, and H-ras (Wilcoxon rank sum test, P = .008, .02, .04, and .04, respectively). External validation by immunohistochemistry confirmed MDM2 and erbB2 as being predictive of locoregional response. Controlling for stage of disease, positivity for MDM2 or erbB2 was an independent negative predictor of locoregional disease-free survival.

CONCLUSION

Genomic screening by cDNA microarray and validation internally by real-time RT-PCR and externally by immunohistochemistry have identified two genes (MDM2 and erbB2) as predictors of locoregional failure in LPC patients treated with CRT. The role of these genes in treatment selection and the functional basis for their activity in CRT response merit additional consideration.

Celecoxib Toxicity Is Cell Cycle Phase Specific

Celecoxib inhibits proliferation and induces apoptosis in human tumors, but the molecular mechanisms for these processes are poorly understood. In this study, we evaluated the ability of celecoxib to induce toxicity in head and neck squamous cell carcinomas (HNSCC) and explored the relationships between celecoxib-induced cell cycle inhibition and toxicity in HNSCC. Celecoxib inhibited the proliferation of UM-SCC-1 and UM-SCC-17B cells both in vitro and in vivo, accompanied by G(1) phase cell cycle arrest and apoptosis. Celecoxib induced p21(waf1/cip1) at the transcriptional level independent of wild-type p53 function, leading to decreased expression of cyclin D1 and hypophosphorylation of Rb, with subsequent marked downstream decreases in nuclear E2F-1 protein expression and E2F transactivating activity by luciferase reporter assay. Cell cycle phase-specific cytometric sorting showed that celecoxib induced clonogenic toxicity preferentially to cells within the S phase greater than G(1) and G(2) phases. Levels of p21(waf1/cip1) and cyclin D1 protein were reduced in the S phase compared with the G(1) and G(2) phases, suggesting a possible protective role for p21(waf1/cip1) expression in celecoxib toxicity. In conclusion, we show that celecoxib has marked antiproliferative activity against head and neck cancer cells through transcriptional induction of p21(waf1/cip1) and G(1) phase accumulation leading to S phase-specific clonogenic toxicity. We additionally show that a profound inhibition of nuclear E2F function provides a possible mechanism for this S phase-specific toxicity.

Is there a role for PCR-SSCP among the methods for missense mutation detection of TP53 gene?

Mutation analysis methods have increased in variety during the past years. High-throughput microarray methods have especially increased in popularity. However, new methods require reference points, and not all of the methods are equal in sensitivity and specificity. Furthermore, the detection of unknown missense mutations, such as unknown TP53 mutations in human tumors, for clinical purposes requires great accuracy, which may be difficult to acquire with the current high-throughput methods. For these reasons, the classical methods, such as PCR-manual sequencing and PCR-SSCP, are still valuable and necessary.

Nuclear factor-kappaB p65 small interfering RNA or proteasome inhibitor bortezomib sensitizes head and neck squamous cell carcinomas to classic histone deacetylase inhibitors and novel histone deacetylase inhibitor PXD101

Histone deacetylase inhibitors (HDI) can inhibit proliferation and enhance apoptosis in a wide range of malignancies. However, HDIs show relatively modest activity in head and neck squamous cell carcinomas (HNSCC), in which we have shown the activation of nuclear factor-kappaB (NF-kappaB; NF-kappaB1/RelA or p50/p65), a transcription factor that promotes expression of proliferative and antiapoptotic genes. In this study, we examined if HDIs enhance activation of NF-kappaB and target genes and if genetic or pharmacologic inhibition of NF-kappaB can sensitize HNSCC to HDIs. Limited activity of classic HDIs trichostatin A and sodium butyrate was associated with enhanced activation of NF-kappaB reporter activity in a panel of six HNSCC cell lines. HDIs enhanced NF-kappaB p50/p65 DNA binding and acetylation of the RelA p65 subunit. Transfection of small interfering RNAs targeting p65 strongly inhibited NF-kappaB expression and activation, induced cell cycle arrest and cell death, and further sensitized HNSCC cells when combined with HDIs. The p65 small interfering RNA inhibited HDI-enhanced expression of several NF-kappaB-inducible genes implicated in oncogenesis of HNSCC, such as p21, cyclin D1, and BCL-XL. Bortezomib, an inhibitor of proteasome-dependent NF-kappaB activation, also increased sensitization to trichostatin A, sodium butyrate, and a novel HDI, PXD101, in vitro, and to the antitumor effects of PXD101 in bortezomib-resistant UMSCC-11A xenografts. However, gastrointestinal toxicity, weight loss, and mortality of the combination were dose limiting and required parenteral fluid administration. We conclude that HDI-enhanced NF-kappaB activation is one of the major mechanisms of resistance of HNSCC to HDIs. The combination of HDI and proteasome inhibitor produced increased antitumor activity. Low starting dosages for clinical studies combining HDIs with proteasome inhibitors and IV fluid support may be warranted.

Compromised Fanconi anemia response due to BRCA1 deficiency in cisplatin-sensitive head and neck cancer cell lines

Head and neck cancers are commonly treated with the DNA-damaging agent cisplatin. While many tumors respond well to cisplatin treatment, some do not. The mechanism for this differential sensitivity of head and neck tumors to cisplatin is not understood in detail. In this study, we explored whether the functional status of the Fanconi anemia and BRCA pathway (FA/BRCA) would predict cisplatin sensitivity in head and neck cancer cells. The FA/BRCA pathway is critical for the orchestration of the cellular response to cisplatin and other DNA cross-linking agents. It was found that three out of four cisplatin-sensitive head and neck cancer cell lines showed defective formation of FANCD2 nuclear foci while all four cisplatin-resistant cell lines tested were proficient in FANCD2 foci formation following cisplatin treatment. The defect in FANCD2 foci formation in the cisplatin-sensitive cell lines was not due to defective monoubiquitylation of FANCD2 but appeared to be due to reduced expression or defective function of BRCA1 since expression of exogenous BRCA1 restored the ability of these cells to induce FANCD2 foci following cisplatin treatment and enhanced cisplatin resistance. These results suggest a possible role for BRCA1 in modulating cisplatin sensitivity in head and neck cancer cells.

Genome-wide identification of novel expression signatures reveal distinct patterns and prevalence of binding motifs for p53, nuclear factor-kappaB and other signal transcription factors in head and neck squamous cell carcinoma

BACKGROUND

Differentially expressed gene profiles have previously been observed among pathologically defined cancers by microarray technologies, including head and neck squamous cell carcinomas (HNSCCs). However, the molecular expression signatures and transcriptional regulatory controls that underlie the heterogeneity in HNSCCs are not well defined.

RESULTS

Genome-wide cDNA microarray profiling of ten HNSCC cell lines revealed novel gene expression signatures that distinguished cancer cell subsets associated with p53 status. Three major clusters of over-expressed genes (A to C) were defined through hierarchical clustering, Gene Ontology, and statistical modeling. The promoters of genes in these clusters exhibited different patterns and prevalence of transcription factor binding sites for p53, nuclear factor-kappaB (NF-kappaB), activator protein (AP)-1, signal transducer and activator of transcription (STAT)3 and early growth response (EGR)1, as compared with the frequency in vertebrate promoters. Cluster A genes involved in chromatin structure and function exhibited enrichment for p53 and decreased AP-1 binding sites, whereas clusters B and C, containing cytokine and antiapoptotic genes, exhibited a significant increase in prevalence of NF-kappaB binding sites. An increase in STAT3 and EGR1 binding sites was distributed among the over-expressed clusters. Novel regulatory modules containing p53 or NF-kappaB concomitant with other transcription factor binding motifs were identified, and experimental data supported the predicted transcriptional regulation and binding activity.

CONCLUSION

The transcription factors p53, NF-kappaB, and AP-1 may be important determinants of the heterogeneous pattern of gene expression, whereas STAT3 and EGR1 may broadly enhance gene expression in HNSCCs. Defining these novel gene signatures and regulatory mechanisms will be important for establishing new molecular classifications and subtyping, which in turn will promote development of targeted therapeutics for HNSCC.

p53 mutation and cyclin D1 amplification correlate with cisplatin sensitivity in xenografted human squamous cell carcinomas from head and neck

To investigate the response of tumour growth to cisplatin treatment, in relation to p53 mutation and cyclin D1 dysregulation on DNA and protein level, biopsies from seven xenografted human squamous cell carcinomas from the head and neck were analysed with immunohistochemistry for p53 expression and cyclin D1 expression. Polymerase chain reaction-singlestranded conformation polymorphism was used to determine p53 mutations. Fluorescence in situ hybridization was performed to analyse cyclin D1 amplification. The mice were injected i.p. with NaCl (controls) or cisplatin. After injection the tumour volume were measured. The inhibition of tumour growth by cisplatin was defined as the area under the growth curves, and compared with the growth curves of the tumours in the control group. Xenografts with p53 mutation showed significantly higher resistance to cisplatin (p < 0.001) and also tumours with cyclin D1 amplification showed significantly higher resistance (p < 0.001).

5-Fluorouracil Mediates Apoptosis and G1/S Arrest in Laryngeal Squamous Cell Carcinoma via a p53-Independent Pathway

PURPOSE

5-Fluorouracil (5-FU) is a commonly used chemotherapeutic agent in the treatment of laryngeal squamous cell carcinoma. 5-FU can induce cell cycle arrest or apoptosis in various cancers via either a p53-dependent or a p53-independent pathway; however, its pathway of action in laryngeal carcinoma is unknown. In this study, we aim to investigate the role that p53 plays in the cytotoxic effect of 5-FU on laryngeal squamous carcinoma cells.

MATERIALS AND METHODS

We employed two human laryngeal squamous carcinoma cell lines with different p53 statuses-one (UMSCC12) had truncated non-functional p53 and the other (UMSCC11A) had mutant but functional p53. Cell death was detected using cytotoxicity assay and Annexin V staining. Cell cycles were analyzed by flow cytometry. Western blot was used to analyze the protein expression.

RESULTS

5-FU induces apoptosis in both UMSCC12 and UMSCC11A cells in a dose- and time-dependent manner, suggesting that the pathway was p53-independent. 5-FU induced the accumulation of retinoblastoma protein and a cyclin dependent kinase inhibitor, p21WAF1/CIP1, in both UMSCC12 and UMSCC11A cells. However, 5-FU did not induce p53 expression in either UMSCC12 or UMSCC11A cells. In addition, G1/S cell cycle phase arrest was associated with antiproliferative activity of 5-FU in both cell lines. In order to gain an insight into the role p53 plays in response to 5-FU treatment in laryngeal carcinoma, we further transfected either a wildtype p53 plasmid or an empty pcDNA3.1 vector into UMSCC12 cells. We found that 5-FU increased pRb and p21WAF1/CIP1 expression in both p53-transfected and vector-transfected cells without the significant accumulation of p53.

DISCUSSION

Our results suggest that 5-FU mediates apoptosis and G1/S cell cycle phase arrest in laryngeal carcinoma via a p53-independent but p21WAF1/CIP1-dependent or p21WAF1/CIP1-Rb-dependent pathway. While p53 does not seem to be involved in 5-FU induced apoptosis and cell cycle arrest in laryngeal carcinoma, further studies are needed to examine the roles of retinoblastoma protein and p21WAF1/CIP1 in laryngeal carcinoma receiving chemotherapy.

Proteasome inhibitor PS-341 induces apoptosis in cisplatin-resistant squamous cell carcinoma cells by induction of Noxa

Cisplatin is one of the most common DNA-damaging agents used for treating patients with solid tumors such as squamous cell carcinoma (SCC). Unfortunately, significant levels of resistance in SCC cells emerge rapidly following cisplatin treatment. Here we report that the proteasome inhibitor PS-341, the representative of a new class of chemotherapeutic drugs, was capable of inducing apoptosis in cisplatin-resistant SCC cells via the endoplasmic reticulum stress. PS-341 stimulated the phosphorylation of PERK and the unfolded protein response, resulting in the induction of the transcription factor ATF-4. Importantly, the Bcl-2 homology domain 3-only (BH3-only) protein Noxa was found to be strongly induced in cisplatin-resistant SCC cells by PS-341 but not by cisplatin. The knock-down of Noxa using small interference RNA significantly abolished PS-341-mediated apoptosis in SCC cells. Using eIF2alpha mutant mouse embryonic fibroblasts, we found that functional eIF2alpha played an essential role in PS-341-induced Noxa expression. Taken together, our novel findings reveal a direct link between PS-341-induced endoplasmic reticulum stress and the mitochondria-dependent apoptotic pathway and suggest that PS-341 may be utilized for overcoming cisplatin-resistance in human SCC.

Molecular markers of head and neck squamous cell carcinoma: promising signs in need of prospective evaluation

BACKGROUND

The aim of this article is to review recent developments in the biological understanding of head and neck squamous cell carcinomas.

METHODS AND RESULTS

We describe the markers according to their function and their prognostic or predictive roles. Some associations can be found between molecular markers and invasiveness, aggressiveness, degree of differentiation, and tumor stage, but only a few clinical studies have shown an impact on prognosis. In addition, despite an increasing number of articles relating to this topic, the small number of patients included in the studies reported reduces the clinical implications of these results. Few studies applied a more comprehensive molecular analysis approach, such as DNA microarrays or differential expression profiling by polymerase chain reaction, to identify a combination of markers that could be more informative than a single molecular marker.

CONCLUSION

Some progress has been made with respect to molecular markers and head and neck cancers. Translational and prospective, hypothesis-driven research must proceed with sufficient rigor to facilitate the clinical applicability of such results.

Potent antitumor activity of a novel cationic pyridinium-ceramide alone or in combination with gemcitabine against human head and neck squamous cell carcinomas in vitro and in vivo

In this study, a cationic water-soluble ceramide analog L-threo-C6-pyridinium-ceramide-bromide (L-t-C6-Pyr-Cer), which exhibits high solubility and bioavailability, inhibited the growth of various human head and neck squamous cell carcinoma (HNSCC) cell lines at low IC50 concentrations, independent of their p53 status. Consistent with its design to target negatively charged intracellular compartments, L-t-C6-Pyr-Cer accumulated mainly in mitochondria-, and nuclei-enriched fractions upon treatment of human UM-SCC-22A cells [human squamous cell carcinoma (SCC) of the hypopharynx] at 1 to 6 h. In addition to its growth-inhibitory function as a single agent, the supra-additive interaction of L-t-C6-Pyr-Cer with gemcitabine (GMZ), a chemotherapeutic agent used in HNSCC, was determined using isobologram studies. Then, the effects of this ceramide, alone or in combination with GMZ, on the growth of UM-SCC-22A xenografts in SCID mice was assessed following the determination of preclinical parameters, such as maximum tolerated dose, clearance from the blood, and bioaccumulation. Results demonstrated that treatment with L-t-C6-Pyr-Cer in combination with GMZ significantly prevented the growth of HNSCC tumors in vivo. The therapeutic efficacy of L-t-C6-Pyr-Cer/GMZ combination against HNSCC tumors was approximately 2.5-fold better than that of the combination of 5-fluorouracil/cis-platin. In addition, liquid chromatography/mass spectroscopy analysis showed that the levels of L-t-C6-Pyr-Cer in HNSCC tumors were significantly higher than its levels in the liver and intestines; interestingly, the combination with GMZ increased the sustained accumulation of this ceramide by approximately 40%. Moreover, treatment with L-t-C6-Pyr-Cer/GMZ combination resulted in a significant inhibition of telomerase activity and decrease in telomere length in vivo, which are among downstream targets of ceramide.