Isolation of tumor interstitial fluid for metabolic determinations.

Neoplastic cells are characterized by alterations in metabolic pathways, typically leading to an aberrant use of glycolysis even under aerobic conditions - a phenomenon known as the Warburg effect. One consequence of this metabolic shift is the production of lactate, an oncometabolite often found at elevated levels in tumors. Lactate not only fuels the growth of cancer cells but also promotes angiogenesis, immune escape, and metastasis, thereby contributing to tumor progression and resistance to therapy. This highlights the importance of lactate in cancer metabolism and underscores the need for methods to measure it. In this study, we describe various centrifugation and elution protocols to isolate interstitial fluid and measure lactate in experimental tumors. These tumors were generated in immunocompetent mice using the MC38 colon cancer cell line. We propose that, with minor modifications, the methods here described could be successfully adapted for use with tumors originating from other human or murine cell lines. Furthermore, these methods could potentially enable the detection of other oncometabolites in the tumor microenvironment, which could have significant implications for both basic research and therapeutic strategies.