CDK-associated Cullin 1 can promote cell proliferation and inhibit cisplatin-induced apoptosis in the AGS gastric cancer cell line

BACKGROUND Gastric cancer is a common and highly lethal malignancy in the world, but its pathogenesis remains elusive. In this study, we focus on the biological functions of CDK-associated Cullin1 (CAC1), a novel gene of the cullin family, in gastric cancer, which may help us to further understand the origin of this malignancy. METHODS The AGS and MGC803 gastric cancer cell lines and the GES-1 gastric mucosa cell line were selected for study. At first, CAC1 expressions of those cell lines were examined by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) and western blot examinations, then CAC1 small interfering RNA (CAC1-siRNA) were designed and transfected into the AGS cell line with a relatively high level of CAC1. Once CAC1 was silenced, a series of biological characteristics of AGS cells such as cell proliferation, cell cycle, apoptosis, and expressions of apoptosis-related genes (P53, BCL2 and BAX) were determined by MTT, flow cytometry, qRT-PCR and western blot, respectively. RESULTS CAC1 expression of AGS or MGC803 was much higher than that of GES-1. After CAC1 expression was effectively depressed by RNA interference in AGS cells, significant cell growth inhibition occurred. Furthermore, the proportion of cells treated with CAC1-siRNA increased in the G1 phase and decreased in the S phase, indicative of G1 cell cycle arrest. More importantly, the proportions of early/late apoptosis in AGS cells were enhanced with cis-diaminedichloroplatinum (cisplatin, CDDP) treatment, but to a higher extent with cisplatin plus CAC1-siRNA. Interestingly, BCL2 mRNA copies showed about a 30% decrease in the cisplatin group, but dropped by around 60% in the cisplatin plus CAC1-siRNA group. Conversely, the P53 mRNA expressions obtained nearly a two-fold increase in the cisplatin group, in addition to a five-fold increase in the cisplatin plus CAC1-siRNA group, and the BAX mRNA levels had almost a two- and four-fold augmentation, respectively. Meanwhile, P53, BAX and BCL2 showed the same alteration patterns in western blot examinations. CONCLUSIONS CAC1 can promote cell proliferation in the AGS gastric cancer cell line. Moreover, it can prevent AGS cells from experiencing cisplatin-induced apoptosis via modulating expressions of P53, BCL2 and BAX.