Proteomic analysis of 1α,25-dihydroxyvitamin D3 action on human colon cancer cells reveals a link to splicing regulation.

1α,25-Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) and other vitamin D compounds are promising molecules in the prevention and therapy of colon cancer and other neoplasias. To study the mechanism of action of 1,25(OH)(2)D(3) in colon cancer cells, we carried out a comparative proteomic analysis of the nuclear fractions of SW480-ADH cells treated with 1,25(OH)(2)D(3) or vehicle during 8 or 48h. 2D-DIGE analysis combined with MALDI-TOF-TOF mass spectrometry interrogation led to the identification of 59 differentially expressed unique proteins. Most identified proteins were nuclear, but several cytoskeleton-associated proteins were also detected. A good concordance between changes in expression at protein and RNA levels was observed for the validated proteins. A large group of identified proteins, such as SFPQ, SMARCE, KHSRP, TARDBP and PARP1, were involved in RNA processing or modification and have been ascribed to the spliceosome compartment of human cells. In addition, a smaller group of proteins (ERM (Ezrin, Radixin, Moesin) family, VCL, CORO1C, ACTB) were cytoskeleton-associated and played a role in cell adhesion and morphology. These results confirm the induction of epithelial phenotype by 1,25(OH)(2)D(3) and suggest a role for vitamin D compounds in the regulation of the spliceosome and thus, in alternative splicing and possibly microRNA synthesis in colon cancer cells.