Abstract 768: A role for c-Rel in ΔNp63α/v-RAS HA -driven carcinogenesis?.

The p63 isoform ΔNp63α is expressed in basal keratinocytes and overexpressed in human squamous cell carcinomas, but the mechanisms whereby this p53 homologue contributes to cancer pathogenesis have yet to be elucidated fully. In mimicking the overexpression of ΔNp63α observed in squamous cell carcinomas using transient adenoviral transduction of primary murine kerationcytes, we showed that overexpression of ΔNp63α inhibits Ca 2+ -mediated growth arrest and biochemical differentiation. We previously reported that this block in growth arrest is mediated via the NF-κB subunit, c-Rel, which accumulates in a phosphorylated form in the nucleus of ΔNp63α-overexpressing cells and physically associates in a phosphorylation-dependent manner with ΔNp63α. Consistent with the observed effects on growth regulation, ΔNp63α:c-Rel complexes bind to a p63 binding site on the cdk inhibitor p21 WAF1 . To explore the biological impact of long-term ΔNp63α overexpression in primary murine keratinocytes, lentiviruses were developed. Consistent with our transient adenoviral vector studies, keratinocytes expressing lenti-ΔNp63α have enhanced proliferation rates over 15 days in culture relative to lenti-GFP controls. Using a nude mouse grafting model that allows distinction between normal, benign, and malignant growths, we previously reported that lenti-GFP keratinocytes expressing oncogenic v-ras Ha form well differentiated papillomas at the graft site, while keratinocytes expressing lenti-ΔNp63α in combination with v-ras Ha form undifferentiated carcinomas. To expand this model system to study c-Rel we first confirmed that lentivirus-driven ΔNp63α overexpression results in sustained nuclear accumulation of the NF-kB subunit c-Rel, consistent with our observations using the adenovirally transduced cultures. In the lenti-ΔNp63α expressing cultures, enhancement of c-Rel is observed beginning at day 5 post-infection and is maintained through the latest time point tested, 14 days. Lentiviral c-Rel shRNAs have been developed to assess the contribution of altered nuclear c-Rel expression to ΔNp63α-mediated growth regulation in vitro and in vivo and have been successfully used to knockdown c-Rel to the latest time point tested, 28 days. Taken together, these data support a role for ΔNp63α in facilitating keratinocyte transformation and provide a model system for elucidating the contribution of NFkB/c-rel to ΔNp63α /v-ras Ha -driven carcinogenesis. Citation Format: Kathryn E. King, Roshini M. Ponnamperuma, Sa Ra Park, Steven Jay, Linan Ha, Wendy C. Weinberg. A role for c-Rel in ΔNp63α/v-RAS HA -driven carcinogenesis?. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 768. doi:10.1158/1538-7445.AM2013-768