Background The association of circulating lipids with clinical outcomes of drug-resistant castration-resistant prostate cancer (DR-CRPC) is not fully understood. While it is known that increases in select lipids correlate to decreased survival, neither the mechanisms mediating these alterations nor the correlation of resistance to drug treatments is well characterized. Methods This gap-in-knowledge was addressed using in vitro models of non-cancerous, hormone-sensitive, CRPC and drug-resistant cell lines combined with quantitative LC-ESI-Orbitrap-MS (LC-ESI-MS/MS) lipidomic analysis and subsequent analysis such as Metaboanalyst and Lipid Pathway Enrichment Analysis (LIPEA). Results Several lipid regulatory pathways were identified that are associated with Docetaxel resistance in prostate cancer (PCa). These included those controlling glycerophospholipid metabolism, sphingolipid signaling and ferroptosis. In total, 7460 features were identified as being dysregulated between the cell lines studied, and 21 lipid species were significantly altered in drug-resistant cell lines as compared to nonresistant cell lines. Docetaxel resistance cells (PC3-Rx and DU145-DR) had higher levels of phosphatidylcholine (PC), oxidized lipid species, phosphatidylethanolamine (PE), and sphingomyelin (SM) as compared to parent control cells (PC-3 and DU-145). Alterations were also identified in the levels of phosphatidic acid (PA) and diacylglyceride (DAG), whose levels are regulated by Lipin (LPIN), a phosphatidic acid phosphatase that converts PA to DAG. Data derived from cBioPortal demonstrated a population of PCa patients expressing mutations aligning with amplification of LPIN1, LPIN2 and LPIN3 genes. Lipin amplification in these genes correlated to decreased survival in these patients. Lipin-1 mRNA expression also showed a similar trend in PCa patient data. Lipin-1, but not Lipin-2 or − 3, was detected in several prostate cancer cells, and was increased in 22RV1 and PC-3 cell lines. The increased expression of Lipin-1 in these cells correlated with the level of PA. Conclusion These data identify lipids whose levels may correlate to Docetaxel sensitivity and progression of PCa. The data also suggest a correlation between the expression of Lipin-1 in cells and patients with regards to prostate cancer cell aggressiveness and patient survivability. Ultimately, these data may be useful for identifying markers of lethal and/or metastatic prostate cancer.

A lack of understanding exists between the association between circulating lipids and clinical outcomes of drug‐resistant castration‐resistant prostate cancer (CRPC). Although an increase in select circulating lipids correlates to decreased patient survival, neither the mechanisms mediating alterations in these lipids, nor the correlation to drug resistance are well characterized. This gap‐in‐knowledge was addressed using in vitro models of non‐cancerous, hormone‐sensitive, CRPC and drug‐resistant cell lines combined with quantitative HPLC‐ESI‐Orbitrap‐MS lipidomic analysis. Lipid extracts were obtained using Bligh‐Dyer (methanol/chloroform/water) extraction from non‐cancerous, hormone‐sensitive, CRPC and drug‐resistant prostate cell lines. Lipids present in both cells and media were initially analyzed using an untargeted shotgun approach (ESI‐MS), followed by a targeted‐based quantitative HPLC‐ESI‐Orbitrap‐MS approach. Shotgun experiments were performed using commercially available standards. For target‐based lipidomics, LC separation yielded specific lipid class separation prior to ESI/MS/MS enabling enhanced detection of lipids suppressed in the shotgun approach. Post data acquisition for both shotgun and HPLC‐ESI/MS/MS lipidomics were based on multiple methods including isotope, carbon number (to internal standards) and ionization efficiency‐based corrections. Pathway analysis was also performed on the various prostate cell lines. Online resources and software’s utilized included MetaboAnalyst, LIPIDMATCH LIPID MAPS, XCMS, and MZmine. Principle component analysis (PCA) generated scores plots of non‐cancerous, hormone‐sensitive, CRPC parent cell lines and drug‐resistant CRPC cell lines in the positive mode (ESI+) had a total variance of 66%. Additionally, a distinct separation between drug‐resistant and parent control cell lines was shown. Several discriminatory ion features were identified between prostate cell lines, especially between drug‐resistant and parent control neuroendocrine cell lines. Of these discriminatory features, 83 showed significant alterations. Two of the identified lipids had alterations matching those measured in plasma from prostate cancer patients. Distinct phospholipid classes were observed to have increased levels in prostate cancer cells, when compared to non‐cancer cells. Lipidomic analysis identified phosphatidylcholines (PC 36:1), whose levels were increased in Docetaxel resistant CRPC. These data also show that the lipidomic profiles of prostate cancer cell lines mirror that seen in the plasma of prostate cancer patients. These data may lead to new early detection strategies and more personalized treatment options for patients. Support or Funding Information Department of Defense Prostate Cancer Research Program Idea Development Award (PC150431 GRANT11996600) Phospholipids in Prostate Cancer (A. Scores Plot) PCA scores plot comparing drug‐resistant CRPC cells to DU145 control parent cells in the positive mode (ESI+). ~80% of the total variance is explained by Component 1 and ...

PURPOSE The 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, and castration‐resistant prostate cancer (CRPC) cell lines combined with quantitative HPLC‐ESI‐Orbitrap‐MS lipidomic analysis. HYPOTHESIS We 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 changes in this enzyme influences the overall survivability of prostate cancer patients. METHODS Lipids were isolated using the Bligh‐Dyer extraction from non‐cancerous, hormone‐sensitive, and CRPC cell lines. Lipids present in both cells and media were initially analyzed using an untargeted shotgun approach (ESI‐MS), followed by a targeted‐based quantitative HPLC‐ESI‐Orbitrap‐MS approach. Post data acquisition for both shotgun and HPLC‐ESI/MS/MS lipidomics 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. Gene alteration frequency and overall survival data were generated using cBioPortal for Cancer Genomics and GEPIA 2. Lipin expression in cells was determined using immunoblot analysis. RESULTS Our 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), a process controlled by lipin. 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, suggesting that decreased lipin‐1 expression correlates to more aggressive prostate cancer. This hypothesis was supported by analysis of alteration in lipin genes expressed in numerous cohorts of prostate cancer patients, demonstrating that lipin mutations indicated a decrease in the overall survival of prostate cancer patients. CONCLUSIONS Distinct phospholipid classes were observed to have increased levels in prostate cancer cells, as compared to non‐cancer cells. Preliminary data shows a correlation between the abundance of PA and DAG with lipin expression in cells representing more aggressive prostate cancers, which is supported by data from patient populations, suggesting that altered lipin expression correlates to decreased survival.

PURPOSE The 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. HYPOTHESIS We 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. METHODS Lipids 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. RESULTS Our 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. CONCLUSIONS Distinct 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. REFERENCES Ingram, L.M., et al., Identification of lipidomic profiles associated with drug‐resistant prostate cancer cells. Lipids Health Dis, 2021. 20(1): p. 15.