Advancing Education, Research, and Quality of Care for the Head and Neck oncology patient.
Introduction: Caffeine has been reported to have anti-cancer effects through various cellular mechanisms. Recent studies have shown that consumption of caffeinated coffee is inversely associated with the risk of oral cavity and oropharynx cancer. Caffeine is a known agonist of the bitter taste receptor T2R10. Bitter taste receptors (T2Rs), including T2R10, have been studied in various solid tumors including pancreatic, breast, and head and neck cancers. Prior literature showed a T2R10-dependent mechanism to downregulate multidrug-resistant protein ABCG2 in pancreatic adenocarcinoma. The presence of ATP binding cassette (ABC) transporters has been associated with chemoresistance and high-grade disease in head and neck squamous cell carcinoma (HNSCC). The effects of caffeine have yet to be elucidated in HNSCC. Currently, cisplatin is the first-line chemotherapy agent used in HNSCC. We hypothesize that (1) a combinatory treatment with cisplatin and caffeine will decrease cell viability compared to cisplatin treatment alone, and (2) caffeine will downregulate ABC transporters in HNSCC via T2R-mediated mechanisms.
Methods: HNSCC cell lines UM-SCC47, FaDu, and RPMI 2650 were cultured for caffeine and cisplatin treatments. Sublethal dosing of caffeine was first established using crystal violet cell viability assays to ensure that effects were not due to caffeine-induced cytotoxicity. Cell viability was then assessed for cisplatin alone (determined IC50) vs cisplatin with caffeine treatment (cisplatin IC50 with 100 uM or 200 uM caffeine). The expression of ABC transporters ABCC1, ABCG2, ABCF1, and TAP2 were measured following 72-hour caffeine exposure using qPCR normalized to housekeeping gene UBC. ABC transporter expression experiments were repeated under the same conditions with a siRNA T2R10 UM-SCC47 knockdown.
Results: Caffeine concentrations of 100 and 200 uM did not significantly affect cell viability in UM-SCC47, FaDu, and RPMI 2650 cells. Exposure to the combinatory treatment of caffeine and cisplatin significantly reduced cell viability in UM-SCC47 and FaDu (P<0.01), compared to treatment with cisplatin alone. Notably, this reduction in viability was not observed in RPMI 2650, which exhibit the lowest T2R10 expression among the tested cell lines. Compared to no treatment, UM-SCC47 cells treated with 200 uM caffeine showed a significant decrease in the mRNA expression of multidrug-resistant transporters ABCC1, ABCG2, ABCF1, and TAP2 (P<0.05). In UM-SCC47 TA2R10 siRNA knockdown cells, caffeine treatment did not significantly alter ABC transporter expression, suggesting T2R10 involvement in caffeine-induced transporter changes.
Conclusion: The combination of caffeine and cisplatin decreased HNSCC cell proliferation in vitro. Treatment with 200 uM caffeine for 72 hours was associated with a decrease in ABC transporter expression which may influence cisplatin efflux and combat multidrug resistant cancers. These findings have significant public health implications, highlighting caffeine's potential as a well-tolerated adjunct to chemotherapy in treatment-resistant HNSCC.