CEACAM1 Promotes Melanoma Cell Growth through Sox-2

• DOI: 10.1016/j.neo.2014.05.003
• Publication Date: 2014-06-13T04:47:13Z
• Authors: Rona Ortenberg; Gilli Galore-Haskel; Ilanit Greenberg; Bella Zamlin; Sivan Sapoznik; Eyal Greenberg; Iris Barshack; Camila Avivi; Yulia Feiler; Israel Zan-Bar; Michal J. Besser; Ester Azizi; Friedman Eitan; Jacob Schachter; Gal Markel
• Keywords: 0301 basic medicine; Blotting, Western; Mice, SCID; Real-Time Polymerase Chain Reaction; Polymorphism, Single Nucleotide; Article; Mice; 03 medical and health sciences; Antigens, CD; Mice, Inbred NOD; Cell Line, Tumor; Animals; Humans; Melanoma; RC254-282; Cell Proliferation; Oligonucleotide Array Sequence Analysis; 0303 health sciences; Reverse Transcriptase Polymerase Chain Reaction; SOXB1 Transcription Factors; Neoplasms. Tumors. Oncology. Including cancer and carcinogens; Flow Cytometry; Immunohistochemistry; Gene Knockdown Techniques; Heterografts; Cell Adhesion Molecules

The prognostic value of the carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1) in melanoma was demonstrated more than a decade ago as superior to Breslow score. We have previously shown that intercellular homophilic CEACAM1 interactions protect melanoma cells from lymphocyte-mediated elimination. Here, we study the direct effects of CEACAM1 on melanoma cell biology. By employing tissue microarrays and low-passage primary cultures of metastatic melanoma, we show that CEACAM1 expression gradually increases from nevi to metastatic specimens, with a strong dominance of the CEACAM1-Long tail splice variant. Using experimental systems of CEACAM1 knockdown and overexpression of selective variants or truncation mutants, we prove that only the full-length long tail variant enhances melanoma cell proliferation in vitro and in vivo. This effect is not reversed with a CEACAM1-blocking antibody, suggesting that it is not mediated by intercellular homophilic interactions. Downstream, CEACAM1-Long increases the expression of Sox-2, which we show to be responsible for the CEACAM1-mediated enhanced proliferation. Furthermore, analysis of the CEACAM1 promoter reveals two single-nucleotide polymorphisms (SNPs) that significantly enhance the promoter's activity compared with the consensus nucleotides. Importantly, case-control genetic SNP analysis of 134 patients with melanoma and matched healthy donors show that patients with melanoma do not exhibit the Hardy-Weinberg balance and that homozygous SNP genotype enhances the hazard ratio to develop melanoma by 35%. These observations shed new mechanistic light on the role of CEACAM1 in melanoma, forming the basis for development of novel therapeutic and diagnostic technologies.