Overexpression of Cyclin D1 Promotes Tumor Cell Growth and Confers Resistance to Cisplatin-Mediated Apoptosis in an Elastase-myc Transgene–Expressing Pancreatic Tumor Cell Line

Abstract

Purpose: Elevated cyclin D1 in human pancreatic cancer correlates with poor prognosis.Because pancreatic cancer is invariably resistant to chemotherapy, the goal of this study was to examine whether the drug resistance of pancreatic cancer cells is in part attributed to cyclin D1 overexpression. Experimental Design: Stable overexpression and small interfering RNA (siRNA)^mediated knockdown of cyclin D1 were done in the newly established Ela-myc pancreatic tumor cell line. Cisplatin sensitivity of control, overexpressing, and siRNA-transfected cells was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, clonogenic, and apoptotic assays [DNA fragmentation, sub-G 1 , and poly(ADP-ribose) polymerase cleavage analysis]. The role of nuclear factor-nB and apoptotic proteins in cyclin D1-mediated chemoresistance was examined by EMSA and Western blotting, respectively. Results: Overexpression of cyclin D1in Ela-myc pancreatic tumor cells promoted cell proliferation and anchorage-independent growth. Moreover, cyclin D1^overexpressing cells exhibited significantly reduced chemosensitivity and a higher survival rate upon cisplatin treatment, as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and clonogenic assays, respectively. Although overexpression of cyclin D1 rendered cells more resistant to cisplatininduced apoptosis, siRNA-directed suppression of cyclin D1 expression resulted in enhanced susceptibility to cisplatin-mediated apoptosis. The attenuation of cisplatin-induced cell death in cyclin D1^overexpressing cells was correlated with the up-regulation of nuclear factor-nB activity and maintenance of bcl-2 and bcl-xl protein levels. Conclusions: These results suggest that overexpression of cyclin D1 can contribute to chemoresistance of pancreatic cancer cells because of the dual roles of cyclin D1 in promoting cell proliferation and in inhibiting drug-induced apoptosis.Human pancreatic cancer is an aggressive disease that currently has no viable treatment. This is mainly due to late diagnosis and resistance of the cancer cells to conventional chemotherapeutic agents (1 -3). Previous studies have addressed the clinical relevance of cyclin D1 in pancreatic cancer (4 -7). A significant proportion of pancreatic cancer cases show overexpression of the cyclin D1 gene (5, 8). Furthermore, increased cyclin D1 expression is associated with poor prognosis (5) and decreased postoperative patient survival (8). However, the molecular mechanisms underlying the poor prognostic value of elevated cyclin D1 in pancreatic cancer remain unknown.The proto-oncogenic function of cyclin D1 has been attributed in part to its role in promoting cell cycle progression. Cyclin D1 is a key cell cycle regulator of the G 1 to S phase progression (9, 10). The binding of cyclin D1 to cyclindependent kinase (cdk4 or cdk6) leads to the phosphorylation of retinoblastoma protein (pRb) subsequently triggering the release of E2F transcription factors to allow transcription of genes required f...

Glycogen synthase kinase-3β positively regulates the proliferation of human ovarian cancer cells

“…Further, increased expression of cyclin D1 has also been reported to contribute to chemotherapy resistance [30]. Our results that GSK-3β increased cyclin D1 expression in ovarian cancer cells support a possibility that GSK-3β is involved in chemotherapy resistance.…”

3,3′,5-Triiodo-l-thyronine inhibits ductal pancreatic adenocarcinoma proliferation improving the cytotoxic effect of chemotherapy

“…Overall, these studies suggested that cyclin D1 exerts a protective effect against drug-induced cytotoxicity. The molecular mechanisms of cyclin D1-mediated chemoresistance, however, remains to be identified (Biliran et al 2005). In agreement with this data, we have demonstrated that T 3 decreased cyclin D1 levels and we can speculate that the increase of the anti-proliferative effect of DDP induced by T 3 is associated to this T 3--dependent cyclin D1 inhibition.…”

“…The cytotoxic effect of DDP was constant during the first 48 h treatment, but after 72 h the cells began to grow again slowly; this is different from treatment with dFdCyd that showed an increase of cytotoxicity until the end of treatment. Recent studies suggested that the overexpression of cyclin D1 could contribute chemoresistance to DDP therapy in pancreatic cancer cells since dual roles of cyclin D1 in promoting cell proliferation and inhibiting drug-induced apoptosis have been shown (Biliran et al 2005). It was reported that the inhibition of cyclin D1 expression, using an anti-sense strategy, not only suppressed pancreatic cancer cell growth, but also potentiated the anti-proliferative effect of DDP (Kornmann et al 1999).…”

Cell survival, cell death and cell cycle pathways are interconnected: Implications for cancer therapy

“…Attenuation of cisplatin-induced apoptosis in cyclin D1 overexpressing cells was attributed to the upregulation of Bcl2 and Bcl-xL proteins. However, when the overexpressed Cyclin D1 was downregulated, using antisense RNA, the apoptotic cell death induced by cisplatin was enhanced (Biliran et al, 2005). Furthermore, cyclin D3 interacts with caspase-2, and this interaction lead to an increased caspase activity and apoptosis in HEK 293 cells (Mendelsohn et al, 2002).…”