Oncogenic PKC epsilon and Pten loss converge on activating CXCL13 via atypical NF- κB transcriptional signaling in prostate cancer progression

GARG R; BLANDO J; PEREZ C; ABBA MC; BENAVIDES F; KAZANIETZ M

Washington DC

Congreso; AACR Annual Meeting 2017; 2017

Protein Kinase C epsilon (PKCε), a pro-oncogenic member of the PKC family of phorbol ester/diacylglycerol receptors, has been shown to be up-regulated in most epithelial cancers, including prostate cancer. PKCε transgenic overexpression in the mouse prostate causes preneoplastic lesions, however when intercrossed with mice haploinsufficient for Pten, the resulting compound mice (PB-PKCε;Pten+/-) develops invasive adenocarcinoma. We found that Pten-deficient prostate cell lines engineered to overexpress PKCε (CaP8-PKCε) cells become highly invasive and tumorigenic. Microarray gene expression profiling in this cell line revealed marked changes in the expression of genes implicated in proliferation, migration, adhesion, EMT, angiogenesis and metabolism. In particular, the chemokine CXCL13 was identified as the top-most up-regulated gene in CaP8-PKCε cells. Measurements of either CXCL13 mRNA, protein release to the culture medium (CM), or Cxcl13 promoter activity showed clear enhancements in cells overexpressing PKCε or Pten depleted, and these effects were enriched synergistically in CaP8-PKCε cells. CaP8-PKCε subjected to CXCL13 RNAi depletion showed reduced motility and tumorigenic growth. Similar results were observed upon silencing of CXCR5, the CXCL13 receptor. CXCL13 expression and promoter activity in CaP8-PKCε cells were significantly reduced by GF109203X (PKC inhibitor), IKK16, wedelolactone (NF-κB inhibitors), and BKM120 (PI3K inhibitor), but were insensitive to BX795 (PDK1 inhibitor). RNAi-mediated depletion of NIK or IKKα significantly blunted Cxcl13 luciferase promoter activity in CaP8-PKCε cells, but the effect was partially inhibited by IKKβ RNAi, suggesting the role of the atypical NF-κB pathway. Mutation of a responsive element for atypical NF-κB in the CXCL13 promoter abolished CXCL13 reporter activity in CaP8-PKCε cells. Taken together, our study identifies a novel paradigm depicting atypical NF-κB as the transcriptional signaling pathway by which PKCε overexpression/Pten loss regulates overproduction of the chemokine CXCL13 in prostate cancer cells.