Radiosensitization through dual inhibition of Wee1 and PARP in ex vivo cultivated HPV-negative head and neck carcinomas (primary and lymph node metastasis)

Introduction Tumor relapse and recurrence are frequent after primary/adjuvant platinum-based chemotherapy of advanced head and neck cancer, especially when tumors are HPV-negative and present lymph node metastasis. In order to test more efficient and less toxic radiosensitizing substances, preclinical tumor models are required, which enable to examine tumor biology of primary and lymph node metastasis (LN-Met.).

Material & method Tumor specimen of primary and associated LN-Met (if available) were cultivated ex vivo, irradiated and partially treated with inhibitors against Wee1 and PARP. Residual DNA double-strand breaks (DNA-DSB) 24 hours after irradiation quantified by DNA-DSB marker 53BP1 in immunofluorescence were surrogate markers for radiosensitization. Tumor cells were identified via p63 tumor marker. In addition, a treatment of three radio-resistant HPV cell lines was investigated.

Results After dual Wee1/PARP inhibition all three radio-resistant cell lines showed an increased number of residual DSBs and were radiosensitized in the colony assay. In 5 of 7 examined tumors, Wee1/PARP inhibition led to a significant (2,5-7 fold) increase of residual 53BP1-foci number, measured 24 hours after irradiation (p=0,02). Tumor cells of the associated LN-Met. (n=2) also showed an increase of residual foci number, but to a lower extent.

Discussion Our results show that a simultaneous ex vivo cultivation of primary and associated LN-Met. is feasible for head and neck tumors. The findings indicate a radiosensitizing effect of dual Wee1/PARP inhibition. The ex vivo assay could be an effective tool to predict tumor sensitivity towards Wee1/PARP inhibition.

Stiftung Tumorforschung Kopf-Hals. Mildred-Scheel-Nachwuchszentrum

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Artikel online veröffentlicht:
24. Mai 2022