Cytotoxicity Potency of Cannabinoids Is by Serum Supplementation: Implications for In Vitro Cancer Studies

BACKGROUND: Fetal calf serum (FCS) is a key supplement in cell culture, providing nutrients, and growth factors that support cancer cell proliferation. Studies suggest that compound cytotoxicity profiles in vitro vary depending on FCS concentration in culture medium. The study aimed to examine how extracellular conditions influence the in vitro response of cancer cells to phytocannabinoids, with particular emphasis on serum supplementation. METHODS AND RESULTS: Cells were exposed to CBD and THC in media containing 0.5% or 10% FCS for 24-72 h. Cell viability was assessed using the sulforhodamine B assay and live-cell imaging. Significantly enhanced cytotoxic effects of CBD and THC were noted under low-serum conditions (0.5% FCS) compared to standard conditions (10% FCS), particularly after 72 h incubation. THC demonstrated greater cytotoxicity than CBD in SiHa cells, while both compounds showed similar effects in HeLa cells. CONCLUSION: The study demonstrates that serum concentration critically modulates the cytotoxic potency of cannabinoids. Reduced FCS enhances cannabinoid efficacy by limiting protein binding, emphasizing the need to optimize serum conditions for accurate in vitro cytotoxicity assessments.