Abstract 1614: Genetic loss of PKC epsilon inhibits development and metastasis of prostate cancer in transgenic adenocarcinoma of mouse prostate model

Abstract

Abstract Protein kinase C epsilon (PKC∈), a novel PKC isoform is over-expressed in prostate cancer (PCa) development in both human and mouse. PKC∈ expression correlates with the aggressiveness of human PCa. However, the role of PKC∈ plays in the course of development and metastasis of PCa in vivo is unknown. To obtain the first molecular genetic evidence that PKC∈ is linked to development and metastasis of PCa, we generated PKC∈-deleted mice by crossbreeding transgenic adenocarcinoma of mouse prostate (TRAMP) (TG//WT) mice with PKC∈ knock out (TG//KO) mice. Sixteen weeks old TG Wild-type (TG//WT), TG//PKC∈ Heterozygous (TG//Het) and TG//PKC∈ KO (TG//KO) were evaluated for PCa development and metastasis. A significant decrease in the PKC∈ protein level was observed in the prostate tissues of TG//Het and TG//KO mice compared to TG//WT mice. PKC∈ deletion in TRAMP mice did not affect on the expression of other PKC isoforms neither in prostate nor in brain tissues. We performed MicroPET/CT imaging, using a tumor selective radiopharmaceutical agent 124I-NM404, of 16 wks old mice from each of TG//WT, and TG//KO mice. Results illustrated a lack of focal uptake of 124I-NM404 in TG//KO mice compared to TG//WT mice. TG//WT mice showed metastasis in proximal lymph node as evident by uptake of 124I-NM404. Histopathology data revealed PCa metastasis into the lungs, livers and lymph nodes of TG//WT mice. However, no metastasis was observed in TG//Het and TG//KO mice suggesting the role of PKC∈ in development and metastasis. We have previously shown that PKC∈ associates with Stat3 and this association increases with the progression of the diseases in TRAMP mice and in human PCa. Deletion of PKC∈ in TRAMP mice inhibited 1) phosphorylated forms of both Stat3Ser727 and Stat3Tyr705, 2) DNA binding activity of Stat3, 3) expression levels of markers of proliferation (PI3K85 and PCNA), anti-apoptosis (BclxL), and metastasis (VEGF and COX-2) and 4) IL-6 receptor expression and serum IL-6 levels. To obtain clues about the genes regulated by PKC∈ and linked to the Stat3 signaling pathway, we performed focused PCR arrays of JAK/STAT signaling in excised PCa tissues from TG//WT and TG//KO mice. This array contained 84 genes related to JAK/STAT family members, the receptors that activate them, nuclear co-factor and co-activators associated with the Stat proteins, Stat inducible genes, and negative regulators. Data revealed a significant down-regulation in the m-RNA expression of CCAAT/enhancer binding protein (CEBP) β (2.5 fold), C-reactive protein (4.34 fold), epidermal growth factor receptor (EGFR) (4.54 fold), gp130 (2.5 fold), jun B (2.5 fold), and Stat3 (2.85 fold) in TG//KO mice compared to TG//WT mice. Taken together, these results provide first molecular genetic evidence of the role of PKC∈ in the development and metastasis of PCa in a transgenic mouse model. (Support: NIH Grant, CA35368). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1614. doi:10.1158/1538-7445.AM2011-1614