Acidic tumor-cell plasma membrane lipid bilayer

The acidic tumor-cell plasma membrane lipid bilayer is a distinctive feature of the tumor microenvironment resulting from the Warburg effect, where cancer cells prioritize aerobic glycolysis, leading to the accumulation of lactic acid and a decrease in extracellular pH to approximately 6.5–6.8 (Gatenby & Gillies, 2004 [Nature Reviews Cancer]). This pH gradient between the acidic tumor surface and the neutral systemic circulation (pH 7.4) provides a unique physical target for selective drug delivery (Reshetnyak et al., 2006 [PNAS]). Therapeutic strategies often employ pH-sensitive molecules, such as pH-Low Insertion Peptides (pHLIPs), which undergo a conformational change and insert into the lipid bilayer only under acidic conditions (Wyatt et al., 2017 [Trends in Biotechnology]). This mechanism allows for the targeted delivery of chemotherapeutic agents, imaging probes, or toxins directly to cancer cells while sparing healthy tissues at physiological pH. Consequently, the lipid bilayer itself acts as a conditional receptor-like target that facilitates the localization and internalization of specialized therapeutic payloads, such as the clinical-stage conjugate CBX-12 (Cybrexa Therapeutics, 2023).

Other names

Acidic tumor microenvironment membranepH-sensitive cancer cell membraneAcidic cancer cell lipid bilayerAcidic tumor cell surfaceAcidic tumor cell membrane

The mechanism of action involves the pH-dependent insertion of therapeutic agents into the lipid bilayer. At the physiological pH of 7.4, targeting molecules like pH-Low Insertion Peptides (pHLIPs) remain unstructured and do not interact strongly with membranes. However, in the acidic environment of a tumor (pH < 7.0), the protonation of specific residues (e.g., aspartate or glutamate) increases the hydrophobicity of the molecule, triggering the formation of an alpha-helix that inserts into and across the plasma membrane (Reshetnyak et al., 2006 [PNAS]). This process can be used to translocate cell-impermeable payloads into the cytoplasm or to tether imaging agents to the cell surface (Wyatt et al., 2017 [Trends in Biotechnology]).