Cancer Genes and Genomics Role of Neurofilament Light Polypeptide in Head and Neck Cancer Chemoresistance

Resistance to cisplatin-based chemotherapy is responsible for therapeutic failure of many common human cancers including cancer of head and neck (HNC). Mechanisms underlying cisplatin resistance remain unclear. In this study, we identified neurofilament light polypeptide (NEFL) as a novel hypermethylated gene associated with resistance to cisplatin-based chemotherapy inHNC. Analysis of 14HNC cell lines revealed that downregulation of NEFL expression significantly correlated with increased resistance to cisplatin. Hypermethylation of NEFL promoter CpG islands was observed in cell lines as examined by bisulfiteDNA sequencing andmethylation-specific PCR (MSP) and tightly correlated with reduced NEFL mRNA and protein expression. Furthermore, in patient samples withHNC (n1⁄4 51) analyzed by quantitativeMSP,NEFL promoter hypermethylation was associated with resistance to cisplatin-based chemotherapy [relative risk (RR), 3.045; 95% confidence interval (CI), 1.459–6.355; P 1⁄4 0.007] and predicted diminished overall and disease-free survival for patients treated with cisplatin-based chemotherapy. Knockdown ofNEFL by siRNA in the highly cisplatin-sensitive cell line PCI13 increased (P< 0.01) resistance to cisplatin. In cisplatin-resistant O11 and SCC25cp cells, restored expression of NEFL significantly increased sensitivity to the drug. Furthermore, NEFL physically associated with tuberous sclerosis complex 1 (TSC1), a known inhibitor of the mTOR pathway, and NEFL downregulation led to functional activation of mTORpathway and consequentially conferred cisplatin resistance. This is the first study to show a role forNEFL in HNC chemoresistance. Our findings suggest that NEFL methylation is a novel mechanism for HNC chemoresistance and may represent a candidate biomarker predictive of chemotherapeutic response and survival in patients with HNC. Mol Cancer Res; 10(3); 305–15. 2012 AACR.