Cell membrane phospholipid bilayer in acidic tumor microenvironment

The cell membrane phospholipid bilayer in the acidic tumor microenvironment (TME) is a distinct physiological target characterized by a lower extracellular pH (pHe 6.5–6.8) compared to healthy tissues (pHe 7.4) (Gatenby & Gillies, 2008, Nature Reviews Cancer). This acidity results from increased glycolysis (the Warburg effect) and poor vascularization, leading to the accumulation of lactic acid and protons in the interstitial space (Webb et al., 2011, Nature Reviews Cancer). Therapeutic strategies exploit this environment using pH-Low Insertion Peptides (pHLIP), which undergo a conformational change and insert into the lipid bilayer only under acidic conditions (Reshetnyak et al., 2006, PNAS). This mechanism allows for the selective delivery of imaging agents or chemotherapeutic payloads directly to tumor cells while sparing healthy tissue (Wyatt et al., 2017, Trends in Biotechnology). Additionally, pH-sensitive liposomes and nanoparticles are engineered to destabilize and release their contents upon interaction with the acidic membrane surface (Liu et al., 2013, Progress in Polymer Science). By targeting the physical state of the membrane rather than specific protein receptors, these approaches can potentially bypass common drug resistance mechanisms like receptor mutation or downregulation (Anderson et al., 2016, Cancer Research). Furthermore, agents like SapC-DOPS target specific lipids like phosphatidylserine that become accessible or reactive in the acidic TME (Qi et al., 2009, Clinical Cancer Research). This target represents a broad-spectrum approach to oncology, as acidity is a nearly universal feature of solid tumors regardless of their genetic profile.

Other names

Acidic tumor cell membranepH-sensitive lipid bilayerAcidic tumor microenvironment membraneTumor cell membrane in acidic conditions

Molecules targeting this structure utilize pH-dependent conformational changes or protonation to trigger membrane insertion, pore formation, or cargo release specifically within the acidic extracellular environment of a tumor (Reshetnyak et al., 2006, PNAS; Qi et al., 2009, Clinical Cancer Research). For example, pHLIP peptides remain unstructured at neutral pH but form an alpha-helix that inserts into the bilayer when the pH drops below 7.0, enabling the delivery of membrane-impermeable payloads directly into the cytoplasm (Wyatt et al., 2017, Trends in Biotechnology).