Lipin Expression Correlates to Differences in Phospholipid Profiles in Drug‐Resistant Prostate Cancer Cells

Abstract

PURPOSEThe association between clinical outcomes of prostate cancer progression and lipid remodeling is not well understood. Although it is known that increases in select circulating lipids correlate to decreased patient survival, the mechanisms mediating alterations in these lipids are not fully explained. We addressed this gap‐in‐knowledge using in vitro models of non‐cancerous, hormone‐sensitive, castration‐resistant prostate cancer (CRPC), and docetaxel resistant (DR) CRPC cell lines combined with quantitative HPLC‐ESI‐Orbitrap‐MS lipidomic analysis.HYPOTHESISWe hypothesized that the expression of lipin (phosphatidic acid phosphatase), an enzyme mediating the conversion of phosphatidic acid to diacylglycerol, correlates to changes in lipidomic profiles in prostate cancer cells. We further hypothesized that the lipidomic profile of metastatic CRPC cell lines (PC‐3 and DU‐145) will shift as they are undergoing multiple treatments of docetaxel.METHODSLipids were isolated using the Bligh‐Dyer extraction from non‐cancerous, hormone‐sensitive, CRPC, and DR‐CRPC cell lines. Lipids were initially analyzed using an untargeted shotgun approach (ESI‐MS), followed by a targeted‐based quantitative HPLC‐ESI‐Orbitrap‐MS approach. Post data acquisition were based on multiple methods including isotope, carbon number (to internal standards) and ionization efficiency‐based corrections. Online resources and software's utilized included MetaboAnalyst, LIPIDMATCH, LIPID MAPS, XCMS, and MZmine.Lipin‐1 expression in cells was determined using immunoblot analysis. Docetaxel‐sensitive traits were obtained after five treatments of 1 nM docetaxel between passages of the CRPC cell line PC‐3. Results were demonstrated by a 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐Diphenyltetrazolium Bromide (MTT) assay.RESULTSOur data showed significant changes in the abundance of lipid species between the various cell lines and a correlation between select lipid species and the progression of prostate cancer. Prominent among these were the levels of phosphatidic acid (PA) and diacylglycerol (DAG). Most notably, PA levels in cells tended to inversely correlate with DAG levels. These levels correlated to the decreased expression on lipin, specifically lipin‐1.CONCLUSIONSDistinct phospholipid classes were observed to have increased levels in prostate cancer cells, as compared to non‐cancer cells. The protein expression of lipin‐1 in most prostate cell lines correlated to the abundance of PA, excluding the DR cell lines. This suggests that altered lipin expression correlates to decreased survival. Additionally, dosing the parent and treated PC‐3 cells with a range of docetaxel indicated that the 5x1nM treated cells had a larger cytotoxic effect to docetaxel, as compared to the non‐treated cells.REFERENCESIngram, L.M., et al., Identification of lipidomic profiles associated with drug‐resistant prostate cancer cells. Lipids Health Dis, 2021. 20(1): p. 15.