Abstract LB-137: Tissue-specific conditional PKCϵ knockout mice: a model to precisely reveal PKCϵ functional role in initiation, promotion and progression of cancer

Abstract

Abstract Evidence from our laboratory and others indicate that PKCϵ is a transforming oncogene and a predictive biomarker of various human cancers including prostate, breast, head and neck, lungs, brain, bladder and cutaneous squamous cell carcinoma (SCC). However, a precise in vivo link of PKCϵ and its downstream signaling components to cancer induction, progression and metastasis remain undefined. To achieve these goals, we generated tissue specific conditional PKCϵ knockout mice using cre-lox technology. To do so, we generated a targeting vector in which Exon 4 of the PKCϵ gene was flanked by LoxP sites. This vector was used to generate mice carrying two floxed alleles of PKCϵ (PKCϵLoxP/LoxP mice) by standard gene knockout methodology. Homozygous PKCϵLoxP/LoxP mice have normal body weight and phenotype. To determine what effect loss of PKCϵ would have on the prostrate, the PKCϵLoxP/LoxP mice were bred to prostate specific cre (PB-Cre4+). Western blot and immunohistochemical analyses showed inhibition of PKCϵ protein level in the prostate of PKCϵ-KO mice. However, no change in the PKCϵ protein level was observed in the spleen, liver and lungs of PKCϵ-KO mice. Also, PKCϵ deletion in prostate did not affect the levels of other PKC isoforms (PKCα, PKCβII, and PKCς). No significant difference was observed in the prostate weight of PKCϵLoxP/LoxP and PKCϵ-KO mice. Histopathological analyses of prostate from both PKCϵLoxP/LoxP and prostate PKCϵ-KO mice showed normal pathology in the PKCϵ-KO prostate. To determine the functional impact of prostate specific deletion of PKCϵ on prostate tumor growth, we performed an orthotopic xenograft study. In this experiment, TRAMP mouse tumor cells (TRAMPC1, 2×106) were implanted in the prostate. Mice were sacrificed at 6 weeks post-implantation. Results demonstrated a significant (P<0.05) decrease in the growth of prostate tumor weight in PKCϵ-KO mice compared to wild type. To determine a role for PKCϵ in the epidermis, PKCϵLoxP/LoxP mice were bred to tamoxifen-inducible K14 Cre mice. PKCϵ deletion in the epidermis resulted in inhibition of ultraviolet radiation (UVR) exposure (2 kJ/m2)-induced Stat3 and AKT phosphorylation, the molecular events essential for UVR-induced development of SCC. In summary, our novel PKCϵLoxP/LoxP mice will be useful to define the functional role and molecular mechanism of PKCϵ linked to cancer induction, progression and metastasis. (Support: NIH Grants CA35368 and CA102431). Citation Format: Bilal B. Hafeez, Louise Meske, Anupama Singh, Ashok Singh, Weixiong Zhong, Patricia Powers, Manorama John, Anne Griep, Ajit Verma. Tissue-specific conditional PKCϵ knockout mice: a model to precisely reveal PKCϵ functional role in initiation, promotion and progression of cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-137. doi:10.1158/1538-7445.AM2015-LB-137