Protein expression of cyclin D2 and p16 in proliferation and differentiation of cultured cardiac myocytes

AIM:To investigate the protein expression of cyclin D₂ and p16 in proliferation and differentiation of cultured cardiac myocytes.METHODS:One-day-old Sparague-Dawley rats were used. Cardiac myocytes(CM) were collected by a trypsin-dispersal method and cultured. Cell growth line and fluorescence activated cell sorting (FACS) were used to investigate the proliferation of CM. Ultra-thin sections were made to observe the ultrastructure of CM under transmission electron microscope. The expression of cyclin D₂ and p16 in CM were measured using immunocytochemistry and image analysis.RESULTS:①Results of cell growth line and FACS analysis showed that cultured CM could proliferate in the first 3 cultured days, but the ability decreased quickly, concomitant with differentiation. CM was obseved quiescent in cell cycle three days later. The ultrastructure of CM showed the large amount of myofilaments and mitochondrion. ②The protein expression of cyclin D₂ in 3,4,5 day CM group was 0.89 times(P＜0.05),0.80 times (P＜0.05) and 0.56 times (P＜0.01) of that in 1 day group, respectively. The expression of p16 in CM was increased during the culture process, 2,3,4,5 day group were 1.63 times, 1.72 times, 1.99 times and 2.84 times (P＜0.01) of that in 1 day group, respectively.CONCLUSION:Cultured neonatal rat cardiac myocytes could proliferate during the first 3 days after incubation, but the ability of proliferation decreased, from the fourth day, concomitant with differentiation. Cyclin D₂ and p16 play the key roles in CM postnatal development. Downregulation of cyclin D₂ and upregulation of p16 may induce CM differentiation.     

Role of BAG2 gene in A549 cell proliferation and its clinical implications

AIM: To investigate the role of Bcl-2-associated athanogene 2 (BAG2) in the proliferation of human lung adenocarcinoma A549 cells and its clinical implications. METHODS: The abundance of BAG2 protein in A549 and lung bronchial epithelium (HBE) cells were measured by Western blot. After down-regulation of BAG2 by transfection of siRNA in A549 cells, the expression of cell proliferation and cell cycle related proteins were detected by CFSE assay, WST-1 assay and Western blot, respectively. Moreover, the expression of BAG2 in cDNA array which contained 10 pairs of lung cancer and adjacent tissue was verified. Meanwhile, BAG2 expression in GEO database, which included the human lung cancer and adjacent tissue microarray data was analyzed. The prognosis power of BAG2 was evaluated by the Kaplan-Meier survival curve analysis. RESULTS: BAG2 had remarkably higher expression level in A549 cells than that in HBE cells. Knockdown of BAG2 resulted in significantly inhibition of proliferation in A549 cells, accompany with the significantly down-regulation of cyclin B1 and cyclin E1. BAG2 was over-expressed in the lung cancer tissues, as compared with the adjacent normal tissues. Kaplan-Meier plotter and cDNA microarray results showed that patients with higher BAG2 expression were significantly associated with poorer survival. CONCLUSION: The BAG2 gene tends to regulate A549 cells proliferation via cyclin B1 and cyclin E1. BAG2 has significantly prognostic power on the survival of lung cancer patients.