The expression of PKM1 and PKM2 in benign and cancerous prostatic tissues

e17058 Background: Prostate cancer (PCa) is the most diagnosed cancers in American men. After androgen deprivation therapy (ADT) fails, there is an increase in the aggressive neuroendocrine (NE) phenotype. Currently, there is no effective treatment for NE prostate cancer (NEPC). The metabolic reprogramming, one of the cancer hallmarks, regulates PCa progression and therapy resistance. However, the energy metabolism in NEPC has not been well studied yet. Pyruvate kinase (PK), catalyzing the final step of glycolysis, has PKM1, PKM2, PKL and PKR four isoforms. PKL and PKR are expressed in the liver and erythrocytes, respectively. Alternative splicing of PKM results in two isoforms, PKM1 and PKM2, which are expressed in most tissues. In prostate adenocarcinoma, loss of PKM1 promotes PCa progression whereas loss of PKM2 suppresses tumor growth. However, the expression pattern of PKM1 and PKM2 in NEPCa remains largely unknown. Methods: Immunofluorescence (IF), immunohistochemistry (IHC), Western blot and RT-qPCR were conducted to examine the expression of PKM1 and PKM2 in both murine and human prostatic tissues. The bioinformatics analysis was done using the publicly available RNA-Seq data obtained from the cBioportal, the Cancer Genome Atlas (TCGA), and the Cancer Cell Line Encyclopedia websites (CCLE). Results: TRAMP is a widely used PCa mouse model. TRAMP mice develop prostatic intraepithelial neoplasia (PIN) and the tumors progress into NEPC following castration. We found that PKM1 expression was detected in normal prostate but not in the PIN lesions. In the TRAMP NEPC tumors, PKM1 expression was detected in the NE areas but not in the adjacent PIN lesions. Compared with the adjacent PIN, NEPC cells displayed lower PKM2 expression. Further, we examined the expression of PKM1 and PKM2 in human prostatic tissues including benign prostatic hyperplasia (BPH), low-grade adenocarcinomas (AdPCa), high-grade AdPCa, and NEPC. We found that in BPH, basal epithelial cells express both PKM1 and PKM2. In PCa, PKM1 was robustly expressed in the stromal cells but its expression was absent in the cancer cells in majority of the specimens examined except a small number of samples where low level of PKM1 was detected in the cancer cells. However, PKM1 expression was detected in 9 out of 12 NEPC samples and colocalized with NE marker chromogranin A. This co-expression was also detected in the NE cells scattered on the prostate adenocarcinoma tissues. As for PKM2, its expression was detected in all the samples examined. However, different from previous report, PKM2 expression levels did not correlate with cancer grade in this cohort. Conclusions: PKM1 is expressed in the basal epithelial cells of benign prostates, a small subset of prostate adenocarcinomas, and 75% NEPC tumors. PKM2 is expressed throughout prostate development, in both benign and cancerous prostate. However, PKM2 expression does not correlate with tumor grade.