SCC-112, a novel cell cycle-regulated molecule, exhibits reduced expression in human renal carcinomas.

We report here the identification and an initial characterization of a novel cell cycle-regulated molecule, SCC-112. SCC-112 cDNA (6744 bp) encodes a longest open reading frame (ORF) comprised of 1297 amino acids, representing a approximately 150-kDa nuclear protein. SCC-112 mRNA and protein levels were relatively high during the G2/M phase of the cell cycle in MDA-MB 435 breast cancer cells. Transient expression of SCC-112 cDNA in COS-1 cells led to an increase in the number of cells in sub-G1 phase and enhanced activity of caspase-3, a downstream effector of apoptosis. Stable transfection of SCC-112 cDNA in MDA-MB 231 breast cancer cells also led to an increase in the number of cells in sub-G1 phase ( approximately 2-3-fold), indicative of apoptosis. The examination of the paired sets of human normal and tumor tissues revealed that the SCC-112 mRNA level was significantly high in normal breast and kidney tissues as compared to the corresponding primary tumor tissues (P<0.0001; breast, n=50, and kidney, n=20). Consistent with these observations, SCC-112 protein expression (150 kDa) was high in a majority of the normal renal tissues examined as compared to the matched renal tumor tissues (67%, 1.2-fold to>10-fold, n=18). Taken together, these findings suggest that the SCC-112 gene expression is likely to be associated with normal cell growth and proliferation.