HPV-positive oropharyngeal squamous cell carcinoma (OPSCC) is increasing in incidence in many developed countries. HPV infection appears to be associated with defects in DNA double strand break repair. Targeting these defects could facilitate less toxic treatment of OPSCC. The PARP-inhibitor Olaparib inhibits DNA base excision repair and can induce synthetic lethality in cells with deficient repair of double strand DNA breaks. Development of novel therapies for HPV-positive OPSCC is hampered by a lack of in vitro models. The aims of this project were to develop and characterise novel HPV-positive OPSCC cell lines, and use them to evaluate the potential of synthetic lethal therapies.
Novel cell lines were derived from OPSCC biopsies and characterised for HPV infection and integration, p53 status and STR profile. mRNA-seq analysis was used to compare gene expression (human and HPV) in the novel lines with a panel of established head and neck cancer cell-lines. Response to Olaparib was assessed in eight OPSCC cell lines using clonogenic assays, and flow cytometry ( gamma-H2AX and cell cycle).
Two novel cell lines derived from tonsil tumours in non-smoking men, showed the presence of HPV16 DNA, wild-type p53 and viral integration. Differential gene expression analysis showed that the novel lines (CU-OP-2 and CU-OP-3) shared a similar pattern of gene expression, which differed from that observed in two widely used HPV-positive lines (UMSCC-47 and UPCI-SCC-090), as well as from 4 HPV-negative OPSCC cell-lines (UMSCC-4, UMSCC-6, UMSCC-19 and UMSCC-74A). Olaparib treatment reduced colony formation in a dose dependent manner. Two HPV-positive cell lines were sensitive to therapeutically relevant doses of Olaparib. Treatment with Olaparib caused an increase in double strand DNA breaks and accumulation in G2 phase.
Two novel OPSCC cell-lines have been generated and characterised. Some HPV-positive lines appear sensitive to Olaparib at potentially therapeutic doses. This suggests PARP inhibition may be useful for treatment of HPV-positive OPSCC.