Expression of Cell Cycle Regulators During Smooth Muscle Cell Proliferation After Balloon Catheter Injury of Rat Artery

Intimal hyperplasia is defined as the abnormal migration and proliferation of vascular smooth muscle cells (VSMCs) with deposition of extracellular matrix. However, the cell cycle regulatory mechanisms of injury-induced VSMC proliferation are largely unknown. To examine the expression kinetics of cell cycle regulatory factors which is known to be worked positively or negatively, we used rat balloon injury model. Marked induction of proliferating cell nuclear antigen (PCNA), G1/S cyclin-dependent kinase (cdk2), and its regulatory subunit (cyclin E) occurred between 1 and 3 days after balloon arterial injury, and this was sustained for up to 7 days and then declined. However, the induction of the negative regulators, p21 and p27, occurred between 3 and 5 days of injury, peaked after 7 and 14 days and was then sustained. VSMC proliferation after balloon catheter injury of the rat iliac artery is associated with coordinated expression of positive (cdk2, cyclin E and PCNA) and negative (p21, p27) regulators. Cell cycle regulators such as cdk2, cyclin E, p21, p27 may be suitable targets for the control of intimal hyperplasia.

Cyclins D1, E, A expression and synergistic cytotoxicity to a cholangiocarcinoma cell line from recombinant TNF-alpha and PHA supernate.

We studied the cytotoxic effects of recombinant TNF-alpha and supernate of phytohemagglutinin stimulated peripheral blood mononuclear cells individually and in combination against a cholangiocarcinoma cell line. Levels of cyclins D1, E and A in the cell line were detected by immunoblotting, and the cell cycle stage was assayed by propidium iodide staining followed by flow cytometry analysis. Viable and apoptotic cells were assessed by trypan blue dye exclusion, DAPI staining, agarose DNA laddering and propidium iodide staining. At the beginning of each experiment, the majority of cholangiocarcinoma cells expressed cyclin A and were in S phase as determined by propidium iodide staining. Treatment of such cells with recombinant TNF-alpha resulted in cytotoxic effects clearly evident at 36 hours post exposure. There was a synergistic killing effect when recombinant TNF-alpha was combined with PHA supernate and this effect could be partly neutralized by monoclonal anti TNF-alpha, interleukin (IL)-2, IL-12 and IFN-gamma.

Overexpression of cyclin D1 and cyclin E in 1,2-dimethylhydrazine dihydrochloride-induced rat colon carcinogenesis

Deregulation of G1 cyclins has been reported in several human and rodent tumors including colon cancer. To investigate the expression pattern of G1 cyclins in 1,2- dimethyl-hydrazine dihydrochloride (DMH)-induced rat colon carcinogenesis, we studied the expression of cyclin D1 and cyclin E by quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis and immunohistochemistry (IHC). The mRNA level of cyclin D1 was increased 1.2-fold in adenocarcinomas but not significantly in adenomas, when compared with normal rat colonic mucosa (p<0.05). The cyclin E mRNA level was increased 2.7-fold in adenomas and 3.3-fold in adenocarcinomas (p<0.05). The PCNA mRNA level was also increased 1.9-fold in adenomas and 1.8-fold in adenocarcinomas (p<0.05). Immunohistochemical staining revealed exclusive nuclear staining of the neoplastic cells for cyclin D1, cyclin E and PCNA. Cyclin D1 expression was detected in 56.3% of the adenomas and in 61.5% of the adenocarcinomas examined, whereas cyclin E expression was detected in 87.5% of the adenomas and in 92.3% of the adenocarcinomas. Overall, cyclin D1, cyclin E and PCNA expression was significantly increased at both the mRNA and protein levels in normal colonic mucosa, adenomas and adenocarcinomas, but there was no significant difference in the degree of expression of these genes in adenomas and adenocarcinomas. Our results indicate that the overexpression of cyclin D1 and cyclin E may play an important role during the multistage process of rat colon carcinogenesis, at a relatively early stage, and may disturb cell-cycle control in benign adenomas, and thereafter, participate in tumor progression.