104 Melanoma associated antigen A3 (MAGE-A3) influences proliferation of metastatic squamous cell carcinoma (SCC) in vitro

Abstract

104 Melanoma associated antigen A3 (MAGE-A3) influences proliferation of metastatic squamous cell carcinoma (SCC) in vitro A Santana, N Roudiani, J Therrien, JH Lee, D Felsen and J Carucci 1 Dept. of Derm., NYU Langone Med. Ctr., New York, NY, 2 Stiefel Laboratories, Research Triangle Park, NC and 3 Inst. for Ped. Urol., Weill Cornell Medicine, New York, NY In order to identify novel targets for cancer immune therapy, our lab has profiled the expression of cancer testis antigens (CTA) in primary human SCC. CTAs are immunogenic and may be suitable targets for immunotherapy, or as biomarkers for aggressive biological behavior. We recently showed that MAGE-A3 is highly expressed in aggressive SCC with poor prognosis. We hypothesized that MAGE-A3 may be a novel target for immunotherapy and/or a biomarker for metastatic SCCs. In this study we determined MAGE-A3 expression in and the effect of antibody treatment on growth of human (A431) and murine (Pam 212 and LY2, BALB/c) SCC cell lines. Pam 212 cells develop locally invasive SCC in syngeneic hosts and LY2 were isolated from a rare Pam 212 metastasis (Yuspa et al., JID, 1983; Dong et al., J Cell Biochem 1997). A431, Pam 212, and LY2 cell lines express MAGE-A3 at the transcript and protein level as measured by qRT-PCR and immunoblot, respectively. Moreover, A431 SCC growth and proliferation was significantly inhibited after MAGE-A3 antibody treatment measured by MTT (P 0.001) and crystal violet (P 0.001). We found that cell growth and proliferation of locally invasive Pam 212 cells was unaffected by anti-MAGE-A3 treatment. However, metastatic tumor derived LY2 cell growth and proliferation was significantly inhibited after MAGE-A3 antibody treatment measured by MTT (P 0.01) and crystal violet (P 0.01). MAGE-A3 expression could potentially serve both as a cancer biomarker and vaccine candidate due to its expression by SCC cells in vitro. Interestingly, MAGE-A3 antibody treatment inhibited the growth of A431 and LY2, SCCs that metastasize in vivo. These results suggest that metastatic SCC may rely on signaling events downstream of MAGE-A3 to support proliferation. Ongoing studies focus on elucidation of pathways involved in MAGE driven SCC proliferation in vivo using immune competent BALB/c mice. 105 Keratinocyte p38a loss results in increased tumor initiation, decreased malignant progression, and altered tumor type specification during two-stage chemical carcinogenesis in murine skin A Kiss, AC Koppel, C Cataisson, J Anders, S Yuspa, P Bible, M Kellett, MI Morasso and T Efimova 1 Anatomy and Regenerative Biology, George Washington University School of Medicine and Health Sciences, Washington, DC, 2 Laboratory of Cancer Biology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD and 3 Laboratory of Skin Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD The p38a signaling pathway not only regulates the inflammation and stress responses, but also controls, in a context-specific manner, the homeostatic balance of cell proliferation, differentiation and survival, deregulation of which is known to contribute to tumor development. Studies in mouse models revealed both tumor-suppressing and tumor-promoting roles of p38a, depending on tissue and tumor type, and tumor stage. However, the in vivo functional contributions of p38a to the skin carcinogenesis remain incompletely understood. We explored the in vivo role of p38a in two-stage chemical skin carcinogenesis using mice with conditional epidermal keratinocyte-specific genetic ablation of p38a (p38a-cKO). Mutant mice exhibited a significantly increased tumor multiplicity, and, in addition to characteristic benign and malignant squamous tumors, developed benign well-differentiated sebaceous adenomas containing a signature activating Hras mutation. Only 4% of tumors in p38a-cKO mice underwent malignant conversion to squamous cell carcinomas (SCCs), compared with 38% of tumors in wild-type (WT) mice (p<0.0001). p38a deficiency resulted in a significantly reduced size and a more differentiated morphology of p38a-cKO SCCs, relative to WT SCCs. RNA sequencing revealed p38a-dependent transcriptional changes in genes involved in cell differentiation, development, proliferation, cell death, and inflammation, both in control and in v-ras-transformed keratinocytes. Altogether, our data reveal novel roles for p38a signaling in control of tumor initiation, malignant progression, and tumor type specification.