CEACAM1 and neoplasm: Whether SOX9 directly or indirectly regulates CEACAM1 expression is still a matter of debate with different authors obtaining opposing results, possibly due to differences between the types of cells studied (colon epithelium versus melanoma cells lines) and the differences of the roles fulfilled by CEACAM1 in colon carcinoma (tumor growth suppressor) and melanoma (tumor aggressiveness promoter) [50–52].