1,25(OH)2D3 also affects the levels of proapoptotic (ie, Bax and Bak) and antiapoptotic (ie, Bcl-2 and Bcl-XL) proteins, resulting in apoptosis in several tumor models, including human carcinomas of the breast, colon, and prostate.(4,10,33) This study with hMSCs indicates that the antiproliferation effects of 1,25(OH)2D3 or 25(OH)D3 are not explained by increases in Bax or decreases in Bcl-2. Here, BAK1 is linked to carcinoma.