Establishment and characterization of triple drug resistant head and neck squamous cell carcinoma cell lines

Resistance to chemotherapy leading to poor outcome and survival remains a challenge for developing strategies for therapeutic interventions in all types of cancer, including head and neck cancer. In vitro chemoresistant cell line models are an indispensable resource towards delineating the mechanisms involved in drug resistance/response and for the development of novel drugs. Current treatment for head and neck cancer includes chemotherapy with cisplatin, docetaxel and 5-fluorouracil (5-FU) and the response rates to these drugs in patients is 60-80%. The present study aimed to generate head and neck cancer triple drug-resistant cell lines in an effort towards elucidating the mechanisms underlying chemoresistance and providing a resourceful tool for drug design. Using two head and neck squamous cell carcinoma cell lines, Hep-2 (larynx) and CAL-27 (oral cavity), the present study sequentially exposed these cells to increasing concentrations of the combination of docetaxel, cisplatin and 5-FU (TPF) to generate triple drug-resistant cells, termed Hep-2 TPF resistant (TPFR) and CAL-27 TPFR. The effect of the drug treatments on the cell viability, apoptosis, cell cycle and the expression of genes associated with multidrug resistance were analyzed in the parental cells and drug-resistant counterparts. The Hep-2 TPFR and CAL-27 TPFR cells exhibited a higher resistance index (RI >= 2) compared with that of the parental cells. Cell cycle analysis revealed a decreased number of TPFR cells in G0/G1 phase (P<0.05) and a corresponding accumulation of cells in G2/M phase. A reduced degree of apoptosis in these cells (Hep-2, 33 vs 20%, P=0.003; and CAL-27, 18 vs 9.7%) was complemented by an increased expression of genes involved in drug resistance, including MDR1, MRP2, ERCC1, CTR, survivin and thymidylate synthase. The present study, therefore, established two multi drug-resistant head and neck squamous cell carcinoma cell lines and characterized these cells on a cellular and molecular level. Development of these tools accentuates their requirement in the field of drug discovery and in mechanistic studies elucidating the underlying mechanisms of drug resistance.