(82b) Human Serum-like Medium Promotes Extensive Metabolic Alterations in Cancer Cell Lines and Affects Cellular Sensitivity to Chemotherapeutic Drugs. 

Altered cancer metabolism arises through a combination of genetic lesions and conditions subjected by the surrounding microenvironment. Indeed, the interplay between genetic and non-genetic determinants can dynamically affect metabolic regulation, and moreover, influence the heterogeneous metabolic dependencies across different cancers. Efforts to decipher this interplay and, more generally, the context-dependent heterogeneities of cancer cell metabolism may enable the identification of novel targets for anticancer therapeutic intervention. The interrogation of human cancer cell lines in culture is one of the most common approaches exploited to improve our understanding of altered cancer metabolism. However, existing cell culture medium formulations were designed primarily with the objective to promote cell survival and proliferation, and consequently, they poorly reflect in vivo nutrient conditions. Therefore, in an effort to better model the cancer cell microenvironment in vitro, we developed a novel formulation that contains metabolite and salt ion components at concentrations described for human serum. We then utilized a panel of blood cancer cell lines as a model system to determine the metabolic consequences of culturing cells in human serum-like medium (HSLM) relative to RPMI â?? the most commonly used medium for culturing this class of cell lines otherwise. We first validated that HSLM supported cell survival and proliferation across our cell line panel despite having a nutrient composition that was vastly different than that of RPMI and even of serum isolated from mice. We then quantified the net exchange of metabolites between cells and exogenous medium, and found that the rates and â?? in some cases â?? the directionality of metabolite exchange were substantially different in HSLM-cultured cells relative to their RPMI-cultured counterparts. We next quantified the intracellular concentrations of nearly 200 polar metabolites upon culturing in both formulations, and observed extensive alterations across several metabolic pathways in a medium-dependent fashion. In particular, we observed that intermediates along the de novo pyrimidine biosynthesis pathway were among the most drastically affected in both the net nutrient exchange and intracellular quantification data sets. As several widely used chemotherapeutics are known to target different facts of nucleotide metabolism, we then evaluated whether cellular sensitivity to these drugs would be changed upon culturing in HSLM. Indeed, we found that sensitivity to the drug 5-fluorouracil, which is commonly used in the treatment regimen of several types of cancer, was significantly decreased relative to analogous evaluation in RPMI. Our findings demonstrate the importance of efforts to better model in vivo nutrient conditions for interrogation of cancer cell lines in vitro towards improving our understanding of cancer cell metabolism. Moreover, such modeling may also enable a more accurate reflection of cellular responses to anticancer drugs relative to those described in existing medium formulations or, perhaps in some cases, those described in mouse models.