miR-205 Enhances Sensitivity to Genotoxic Agents in HNSCC Cells and Blocks Sphingosine Kinase 2 Action in Tumorigenicity

Head and neck squamous cell carcinoma (HNSCC) exhibits alterations in sphingolipids, sphingosine kinase 2 (SK2), and microRNAs (miRNAs), including miR-205. Resistance to therapy, such as cisplatin and radiation, often leads to recurrence and metastasis. This study investigates the role of SK2 in resistance to DNA damage induced by cisplatin and UV light, as well as the potential of miR-205 to reverse this resistance in HNSCC cells. For this purpose, we adopted SK2 overexpression and SK2 knockdown associated with miR-205 mimic in oral carcinoma keratinocyte cell lines and an in-house established squamous carcinoma primary cell line (LMSCC-03) as models. Resistance to UV and cisplatin was evaluated by using orosphere and clonogenic assays. Western blot analysis was performed to investigate how miR-205 mediates SK2 effects on EMT proteins following exposure to genotoxic agents. NOK-SK2 cells were more resistant to UV exposure than NOK-Ø cells in clonogenic and orosphere assays. Conversely, SK2 knockdown in HN13 cells increased sensitivity to UV exposure, indicating that SK2 confers resistance to UV damage. Interestingly, miR-205 overexpression, in combination with UV or cisplatin exposure, inhibited SK2-mediated resistance to these genotoxic agents in HN12-SK2 and NOK-SK2 cells and decreased the levels of proteins involved in the epithelial-mesenchymal transition (EMT). In LMSCC-03, overexpression of miR-205 significantly decreased cellular viability and clonogenic potential. Moreover, combining cisplatin treatment with miR-205 overexpression abolished the clonogenic potential in LMSCC-03 cells. Our study reveals, for the first time, that miR-205 can be an alternative for sensitization to treatment with genotoxic agents, opening a new and promising strategy for highly malignant HNSCC and overcoming cisplatin resistance.