Calcium/calmodulin-dependent kinases participate in the cell cycle regulation and antiapoptotic mechanisms in MCF-7 human breast cancer cells

The purpose of this research was to test the hypothesis that calcium (Ca2+)/calmodulin-dependent kinases (CaM-Ks) are involved in cell cycle regulation and prevention of oxidative stress-induced apoptosis in MCF-7 human breast cancer cells. We discovered that CaM-Kinases participate in the control of the cell cycle in MCF-7 cells. CaM-KI inhibition with either KN-93 or specific siRNA caused an arrest in the cell cycle in these cells. This arrest occurred in the G1 phase of the cell cycle. Supporting this finding, CaM-K inhibition using KN-93 also resulted in downregulation of cyclin D1 protein and reduction of pRb phosphorylation when cells were compared to control cultures. Furthermore, inhibition of the upstream activator of CaM-KI, CaM-KK, using siRNA also resulted in cell cycle arrest.; We found that CaM-K inhibition increased oxidative stress-induced cell death. Increases in cell death in cultures treated with the CaM-K inhibitor KN-93 in addition to doxorubicin, ionizing radiation, or photodynamic therapy were observed. In a simplified model of oxidative stress, we cultured MCF-7 cells in the presence of KN-93 and hydrogen peroxide. CaM-K inhibition increased hydrogen peroxide-induced apoptosis in MCF-7 cells, which was seen as an increased number of apoptotic cells, DNA fragmentation and PARP cleavage. Furthermore, CaM-KII activity was induced by hydrogen peroxide in MCF-7 cells. By pharmacological and molecular inhibition, we showed that CaM-KII is participating in the hydrogen peroxide-induced ERK phosphorylation. These findings demonstrate that oxidative stress induces CaM-KII activity in breast cancer cells and consequently activates antiapoptotic pathways, such as ERK. This signaling pathway may enable cells to survive treatments that induce oxidative stress in breast cancer cells, such as chemotherapy, ionizing radiation and photodynamic therapy.; Taken together, our results show novel roles for CaM-Kinases in human breast cancer cells. CaM-KK and CaM-KI participate in the control of the G 0-G1 restriction check point of the cell cycle in MCF-7 human breast cancer cells. Furthermore, we discovered that CaM-KII may exert antiapoptotic effects through ERK activation in response to oxidative stress. Considering these findings, we propose that CaM-Kinases can be novel molecular targets in breast cancer research.