Bitter taste receptors (TAS2Rs) are increasingly recognised as extraoral chemosensors that modulate diverse biological processes, including cancer cell behaviour and drug responsiveness. Many TAS2R ligands correspond to therapeutic compounds; however, their contribution to the response of brain tumours to chemotherapy remains unexplored. Here, we investigated whether the bitter taste signalling pathway is modulated by temozolomide (TMZ), the standard chemotherapeutic agent for glioblastoma, with an impact on treatment efficacy in glioblastoma cells. We show that TMZ elicits intracellular Ca2+ responses compatible with activation of G-protein-coupled receptor signalling and induces anti-proliferative and pro-apoptotic effects in multiple human glioblastoma cell lines. Pharmacological inhibition of bitter taste receptors, as well as genetic silencing of the taste transduction G protein GNAT3, significantly attenuated TMZ-induced cytotoxicity, suggesting that bitter taste signalling is involved in this process. In silico ligand prediction combined with receptor expression profiling identified TAS2R43 as a candidate modulator of these effects, and TAS2R43 knockdown markedly reduced TMZ-induced loss of cell viability and apoptosis. Moreover, TMZ enhanced intracellular accumulation of the ABC transporter substrate doxorubicin, suggesting modulation of multidrug efflux mechanisms. Collectively, our findings identify TAS2R43 as a potential biomarker that warrants further validation to improve responses to TMZ and other ABC transporter-limited anticancer drugs.
Costa et al. (Fri,) studied this question.