p63 orchestrates serine and one carbon metabolism enzymes expression in head and neck cancer

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is characterized by high proliferation and limited differentiation. The altered expression of the p53 family members, and specifically of p63, represents a pivotal event in the pathogenesis of HNSCC. Physiologically, p63 affects metabolism through the direct transactivation of the enzyme hexokinase 2, and subsequently controls the proliferation of epithelial cells; nonetheless, its role in cancer metabolism is still largely unclear. The high energetic demand of cancer and the consequent needs of a metabolic reshape, also involve the serine and glycine catabolic and anabolic pathways, including the one carbon metabolism (OCM), to produce energetic compounds (purines) and to maintain cellular homeostasis (glutathione and S-adenosylmethionine).

RESULTS

The involvement in serine/glycine starvation by other p53 family members has been reported, including HNSCC. Here, we show that in HNSCC p63 controls the expression of the enzymes regulating the serine biosynthesis and one carbon metabolism. p63 binds the promoter region of genes involved in the serine biosynthesis as well as in the one carbon metabolism. p63 silencing in a HNSCC cell line affects the mRNA and protein levels of these selected enzymes. Moreover, the higher expression of TP63 and its target enzymes, negatively impacts on the overall survival of HNSCC patients.

CONCLUSION

These data indicate a direct role of p63 in the metabolic regulation of HNSCC with significant clinical effects.

Receptor tyrosine kinase MET as potential target of multi-kinase inhibitor and radiosensitizer sorafenib in HNSCC

BACKGROUND

The multi-kinase inhibitor sorafenib displays antitumoral effects in head and neck squamous cell carcinoma (HNSCC); however, the targeted kinases are unknown. Here we aimed to identify those kinases to determine the mechanism of sorafenib-mediated effects and establish candidate biomarkers for patient stratification.

METHODS

The effects of sorafenib and MET inhibitors crizotinib and SU11274 were analyzed using a slide-based antibody array, Western blotting, proliferation, and survival assays. X-rays were used for irradiations.

RESULTS

Sorafenib inhibited auto-phosphorylation of epidermal growth factor receptor and MET, which has not been described previously. MET expression in HNSCC cells was not always associated with activity/phosphorylation. Furthermore, sorafenib-dependent cell kill and radiosensitization was not associated with MET level. Although MET inhibitors blocked proliferation, they caused only mild cytotoxicity and no radiosensitization.

CONCLUSION

We identified MET as a new potential target of sorafenib. However, MET inhibition is not the cause for sorafenib-mediated cytotoxicity or radiosensitization.

Effect of sorafenib on cisplatin-based chemoradiation in head and neck cancer cells

Despite aggressive chemoradiation (CRT) protocols in the treatment of patients with head and neck squamous cell carcinomas (HNSCC), the outcome is still unfavorable. To improve therapy efficacy we had already successfully tested the multikinase inhibitor sorafenib in combination with irradiation (IR) in previous studies on HNSCC cell lines. In this study we investigated its effect on combined CRT treatment using cisplatin.Radio- and chemosensitivity with and without sorafenib was measured in four HNSCC cell lines and normal fibroblasts (NF) by colony formation assay. Apoptosis and cell cycle analysis were performed by flow cytometry.

In HNSCC cells, sorafenib enhanced the antiproliferative effect of cisplatin without affecting apoptosis induction and with only minor effects on cell inactivation. Sorafenib added prior to irradiation enhanced cellular radiosensitivity in three of the tested HNSCC cell lines and caused massive overall cell inactivation when combined with CRT. In contrast, sorafenib did not radiosensitize NF and reduced cisplatin-induced cell inactivation. Cell inactivation by IR and cisplatin is further increased by the addition of sorafenib in HNSCC, but not in NF cells. Therefore, sorafenib is a promising candidate to improve therapy efficacy for HNSCC.

Roscovitine strongly enhances the effect of olaparib on radiosensitivity for HPV neg. but not for HPV pos. HNSCC cell lines

At present, advanced stage human Papillomavirus (HPV) negative and positive head and neck squamous cell carcinoma (HNSCC) are treated by intense multimodal therapy that includes radiochemotherapy, which are associated with relevant side effects. Patients with HPV positive tumors possess a far better prognosis than those with HPV negative cancers. Therefore, new therapeutic strategies are needed to improve the outcome especially of the latter one as well as quality of life for all HNSCC patients. Here we tested whether roscovitine, an inhibitor of cyclin-dependent kinases (CDKs), which hereby also blocks homologous recombination (HR), can be used to enhance the radiation sensitivity of HNSCC cell lines.

In all five HPV negative and HPV positive cell lines tested, roscovitine caused inhibition of CDK1 and 2. Surprisingly, all HPV positive cell lines were found to be defective in HR. In contrast, HPV negative strains demonstrated efficient HR, which was completely suppressed by roscovitine. In line with this, for HPV negative but not for HPV positive cell lines, treatment with roscovitine resulted in a pronounced enhancement of the radiation-induced G2 arrest as well as a significant increase in radiosensitivity. Due to a defect in HR, all HPV positive cell lines were efficiently radiosensitized by the PARP-1 inhibitor olaparib. In contrast, in HPV negative cell lines a significant radiosensitization by olaparib was only achieved when combined with roscovitine.

Pulsed Radiation Therapy With Concurrent Cisplatin Results in Superior Tumor Growth Delay in a Head and Neck Squamous Cell Carcinoma Murine Model

PURPOSE

To assess the efficacy of 3-week schedules of low-dose pulsed radiation treatment (PRT) and standard radiation therapy (SRT), with concurrent cisplatin (CDDP) in a head and neck squamous cell carcinoma xenograft model.

METHODS AND MATERIALS

Subcutaneous UT-SCC-14 tumors were established in athymic NIH III HO female mice. A total of 30 Gy was administered as 2 Gy/d, 5 d/wk for 3 weeks, either by PRT (10 × 0.2 Gy/d, with a 3-minute break between each 0.2-Gy dose) or SRT (2 Gy/d, uninterrupted delivery) in combination with concurrent 2 mg/kg CDDP 3 times per week in the final 2 weeks of radiation therapy. Treatment-induced growth delays were defined from twice-weekly tumor volume measurements. Tumor hypoxia was assessed by (18)F-fluoromisonidazole positron emission tomography imaging, and calculated maximum standardized uptake values compared with tumor histology. Tumor vessel density and hypoxia were measured by quantitative immunohistochemistry. Normal tissues effects were evaluated in gut and skin.

RESULTS

Untreated tumors grew to 1000 mm(3) in 25.4 days (±1.2), compared with delays of 62.3 days (±3.5) for SRT + CDDP and 80.2 days (±5.0) for PRT + CDDP. Time to reach 2× pretreatment volume ranged from 8.2 days (±1.8) for untreated tumors to 67.1 days (±4.7) after PRT + CDDP. Significant differences in tumor growth delay were observed for SRT versus SRT + CDDP (P=.04), PRT versus PRT + CDDP (P=.035), and SRT + CDDP versus PRT + CDDP (P=.033), and for survival between PRT versus PRT + CDDP (P=.017) and SRT + CDDP versus PRT + CDDP (P=.008). Differences in tumor hypoxia were evident by (18)F-fluoromisonidazole positron emission tomography imaging between SRT and PRT (P=.025), although not with concurrent CDDP. Tumor vessel density differed between SRT + CDDP and PRT + CDDP (P=.011). No differences in normal tissue parameters were seen.

CONCLUSIONS

Concurrent CDDP was more effective in combination PRT than SRT at restricting tumor growth. Significant differences in tumor vascular density were evident between PRT and SRT, suggesting a preservation of vascular network with PRT.

Targeting epidermal growth factor receptor for head and neck squamous cell carcinoma: still lost in translation?

The epidermal growth factor receptor (EGFR) is preferentially expressed in head and neck squamous cell carcinoma (HNSCC), and is a promising therapeutic target. Yet other than cetuximab, no agent targeting EGFR has been approved for this disease, and none has shown benefit over the standard of care. Several randomized trials of antibody and small molecule agents have found no new indication for these agents, despite their initial promise. In this review, we examine the major clinical evidence and discuss potential future developments of translational science in this area, including use of these agents in risk-stratified subgroups, inhibition of downstream/parallel targets, and combination with immunotherapy.