Anti-oncogenic activities of cyclin D1b siRNA on human bladder cancer cells via induction of apoptosis and suppression of cancer cell stemness and invasiveness.

Abstract

The human cyclinD1 gene generates two major isoforms, cyclinD1a and cyclinD1b, by alternative splicing. Although cyclin D1b mRNA is hardly expressed in normal human tissues, it is detected in approximately 60% of human bladder cancer tissues and cell lines. In the present study, to assess the therapeutic ability of cyclinD1b siRNA, we investigated the anti-oncogenic effects of cyclinD1b siRNA on human bladder cancer cell lines, SBT31A and T24, which express cyclinD1b mRNA. Knockdown of cyclinD1b by specific siRNA significantly suppressed cell proliferation, invitro cell invasiveness and three-dimensional (3D) spheroid formation in these cell lines. Cell cycle analyses revealed that cyclinD1b siRNA inhibited G1-S transition in T24 cells. The increase in the sub-G1 fraction, morphological aberrant nuclei with nuclear fragmentation and caspase-3 activity in SBA31A cells treated with cyclinD1b siRNA showed that cyclinD1b siRNA induced apoptosis. In T24 cells, knockdown of cyclinD1b suppressed the expression of the stem cell marker CD44. Knockdown of cyclinD1b or CD44 suppressed the invasiveness under 3D spheroid culture conditions and expression of N-cadherin. Tumor growth of SBT31A cells in nude mice was significantly inhibited by cyclinD1b siRNA. Taken together, these results indicate that knockdown of cyclinD1b suppresses the malignant phenotypes of human bladder cancer cells via induction of apoptosis and suppression of cancer cell stemness and epithelial-mesenchymal transition. Applying cyclinD1b siRNA will be a novel therapy for cyclinD1b-expressing bladder cancers.