Abstract LB-65: Protein kinase Cε, which is linked to development of squamous cell carcinomas, potentiates ultraviolet radiation-induced expression of novel transcription factors GATA and PAX, which regulates expression of cell survival genes

Abstract

Abstract Protein kinase C epsilon (PKCε) is among the six PKC isoforms (α, δ, ε, η, μ, ξ) expressed in both mouse and human skin. We have reported that epidermal PKCε levels dictate the susceptibility of PKCε transgenic mice (TG) to the development of squamous cell carcinomas (SCC) elicited by repeated exposures to ultraviolet radiation (UVR). Histologically, SCC in TG mice, like human SCC, is poorly differentiated and metastatic. To find clues about the mechanism by which PKCε may impart susceptibility to UVR-induced development of SCC, we compared the effects of UVR treatment of TG mice with their wildtype (WT) littermates on global transcription factors (TFs) activation profile. In this experiment, mice were exposed to UVR (2kj/m2) four times (Monday, Wednesday, Friday and Monday). At 1hr and 3hrs post last UVR exposure, these mice were sacrificed. Nuclear lysates were prepared from the scraped epidermis of these mice. To screen for unknown TFs, we employed the Panomics Combo Protein array, which contains consensus complimentary sequences of 345 TFs binding sites. Array results from samples of UVR exposed mice were directly compared to the unexposed mice. TFs that had increased over 2-fold in the UVR exposure experiments were scored as positive for activation. We observed (>2-fold) activation of 70 TFs as early as 1hr post UVR exposure. Among all seventy TFs, highly activated TFs were GATA-1, GATA-2, PAX-4, PAX-6, PAX-8, Thy-1BP, HFH-2, HFH-3, HIF-1, CEA, HOXD8/9/10, AhR/Amt, and MUSF. We performed the validation of various activated TFs and among them we found that GATA and PAX families of transcription factors were found activated. UVR-induced expression level of GATA-1, GATA-2, PAX-4 was enhanced in PKCε over-expressing transgenic mice as compared to wild-type littermates. We employed the Genego program and found that VEGFR-2, CyclinD1, Bcl-2, c-Myc, BMP-4, WT1 and survivin are the downstream target genes of GATA1 and GATA-2. All of these genes are known to play role in the cell survival pathway. We have previously shown that PKCε overexpressing transgenic mice also exhibit constitutive activation of Stat3. Taken together, we conclude that PKCε-mediated activation of Stat-3, GATA-1, GATA-2 and PAX-4 may contribute to the susceptibility of PKCε transgenic mice to UVR-induced development of SCC. (Support: NIH Grant CA 35368) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-65. doi:1538-7445.AM2012-LB-65