Abstract
Head and neck cancers (HNCs) are aggressive epithelial tumours frequently treated using radiation. HNC biology shows distinctions dependent on the oncologic involvement of the human papilloma virus (HPV). Clinically, HPV positive HNCs respond better to radiotherapy but few in vitro data demonstrate radiobiological differences explaining differences in clinical outcomes. This pilot study examined radiobiological responses to irradiation and subsequent regeneration in two HNC cell lines (HPV positive and negative). A novel approach was taken to develop generational cultures of HNC cell lines, UM-SCC-1 (HPV negative) and UM-SCC-47 (HPV positive). MTT assays were used to determine surviving metabolic activity as a function of dose following 6 MV X-ray irradiation. Parallel cultures surviving 4 Gy irradiation (not analysed) were re-cultured and passaged to develop subsequent generations which were re-irradiated and analysed for generational change in radiation response. Second and 3rd generations of UM-SCC-1 showed decreasing metabolic activity with dose but little difference was evident in surviving fractions between these generations. Significantly lower metabolic activity in the 3rd generation at <6 Gy, compared to the 2nd generation, showed UM-SCC-47 becoming progressively more radiosensitive. HPV positive UM-SCC-47 showed generational progression in radiosensitisation not seen in the HPV negative UM-SCC-1.
Highlights
Head and neck cancers are typically aggressive epithelial tumours arising in the mucosae lining the mouth, nose, pharynx and larynx
This study investigated specific radiobiological responses, as a function of dose, in 2 HNSCC cell lines re-cultured following repeated X-ray irradiation
Increasing radiosensitivity in UM-SCC-1 cells was not apparent after the 2nd generation, it was observed to continue for the human papilloma virus (HPV) positive UM-SCC-47 cells
Summary
Head and neck cancers are typically aggressive epithelial tumours arising in the mucosae lining the mouth, nose, pharynx and larynx. A novel approach was taken whereby cell line cultures were re-assayed for metabolic activity in surviving fractions following previous radiation exposures and passage[17]. This identified ‘generational’ change in the metabolic survival of each cell line after exposure to a range of X-ray doses using standard MTT assay[18]. Generational changes in metabolic activity were compared between cell lines of different HPV status This approach results in the development of multiple concurrent cultures of each cell line and this study was undertaken as a pilot to test significance in change of response after subsequent irradiations and to inform future work
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