Influence of Breast Tumor-Associated Lipids on Oxygen Transport Across Model Cell Membranes (Part B: Saturated Phospholipids and Cholesterol).

Dysregulation of lipid homeostasis is common in cancers, and biophysical studies have suggested that increased incorporation of saturated lipids and cholesterol may reduce cell membrane permeability to oxygen (O2). Low intracellular oxygen, in turn, may promote tumor aggressiveness, as well as resistance to radiotherapy. A prior lipidomics study found membrane phospholipids associated with de novo fatty acid synthesis to be unusually abundant in breast tumors with poor prognosis, including the saturated lipids 1-myristoyl-2-palmitoyl-sn-glycero-3-phosphocholine (MPPC14,16, or PC14:0/16:0) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC16,16, or PC16:0/16:0). Part A of the current work has found that MPPC14,16 and cholesterol together promote reduced oxygen permeability. Here, we have followed up on this finding to determine whether the effect is related to lipid saturation generally or to structural features of MPPC14,16 specifically. We have used atomistic molecular dynamics simulations to calculate oxygen permeability coefficients for lipid bilayers composed of either DPPC16,16 or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC14,14, or PC14:0/14:0) mixed in a 1:1 ratio with cholesterol. The resulting mean oxygen permeability values, of 3-5 cm/s, were 2 to 4 times lower than bilayers combining the common monounsaturated phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC, or PC16:0/18:1) in a 1:1 ratio with cholesterol. As such, this study finds that doubly saturated 14- and 16-carbon phospholipids and cholesterol together can generally reduce membrane oxygen permeability. The extent to which such permeability reductions could promote hypoxia in a biological context requires further investigation.