Acidic tumor microenvironment and cell membrane lipid bilayer

The acidic tumor microenvironment (TME) and the cell membrane lipid bilayer constitute a physiological target defined by the metabolic alterations of cancer cells. Due to the Warburg effect, tumors exhibit high rates of glycolysis and lactic acid secretion, resulting in an extracellular pH (pHe) of 6.5 to 6.8, which is significantly more acidic than the pH 7.4 of healthy tissues (Reshetnyak et al., 2006, PNAS). This acidity serves as a physical trigger for specialized molecules, most notably pH-Low Insertion Peptides (pHLIPs), which remain unstructured in neutral conditions but form an alpha-helix and insert into the lipid bilayer when protonated (Wyatt et al., 2017, Trends in Biotechnology). This mechanism allows for the selective delivery of therapeutic payloads, such as cytotoxins or imaging agents, directly into the cytoplasm or onto the membrane of malignant cells. Unlike traditional targets that rely on specific protein expression, this approach exploits a universal hallmark of solid tumors, potentially bypassing issues of receptor heterogeneity and downregulation. Current clinical developments, such as the peptide-drug conjugate CBX-12, utilize this target to deliver potent topoisomerase inhibitors while minimizing systemic toxicity (Cybrexa Therapeutics, 2024). However, challenges remain regarding the specificity of these agents in other naturally acidic environments like the kidneys or sites of inflammation.

Other names

Tumor extracellular acidosisAcidic TMEpH-sensitive membrane interfaceLow pH tumor microenvironmentAcidic TME-lipid bilayer interface

Drugs targeting this environment typically utilize pH-sensitive peptides or polymers that undergo a conformational transition from a soluble state to a membrane-inserted state upon protonation in the acidic extracellular fluid (pH < 7.0). This transition facilitates the direct translocation of cargo across the lipid bilayer or the release of drugs from pH-responsive nanocarriers at the cell surface (Wyatt et al., 2017, Trends in Biotechnology).