TY - JOUR
T1 - The differential staurosporine-mediated G1 arrest in normal versus tumor cells is dependent on the retinoblastoma protein
AU - McGahren-Murray, Mollianne
AU - Terry, Nicholas H.A.
AU - Keyomarsi, Khandan
PY - 2006/10/1
Y1 - 2006/10/1
N2 - Previously, we reported that breast cancer cells with retinoblastoma (pRb) pathway-defective checkpoints can be specifically targeted with chemotherapeutic agents, following staurosporine-mediated reversible growth inhibition in normal cells. Here we set out to determine if the kinetics of staurosporine-mediated growth inhibition is specifically targeted to the G1 phase of cells, and if such G1 arrest requires the activity of wild-type pRb. Normal human mammary epithelial and immortalized cells with intact pRb treated with low concentrations of staurosporine arrested in the G1 phase of the cell cycle, whereas pRb-defective cells showed no response. The duration of G 1 and transition from G1 to S phase entry were modulated by staurosporine in Rb-intact cells. In pRb+ cells, but not in Rb cells, low concentrations of staurosporine also resulted in a significant decrease in cyclin-dependent kinase 4 (CDK4) expression and activity. To directly assess the role of pRb in staurosporine-mediated G1 arrest, we subjected wild-type (Rb+/+) and pRb-/- mouse embryo fibroblasts (MEFs) to staurosporine treatments. Our results show that whereas Rb+/+ MEFs were particularly sensitive to G1 arrest mediated by staurosporine, pRb-/- cells were refractory to such treatment. Additionally, CDK4 expression was also inhibited in response to staurosporine only in Rb+/+ MEFs. These results were recapitulated in breast cancer cells treated with siRNA to pRb to down-regulate the pRb expression. Collectively, our data suggest that treatment of cells with nanomolar concentrations of staurosporine resulted in down-regulation of CDK4, which ultimately leads to G1 arrest in normal human mammary epithelial and immortalized cells with an intact pRb pathway, but not in pRb-null/defective cells.
AB - Previously, we reported that breast cancer cells with retinoblastoma (pRb) pathway-defective checkpoints can be specifically targeted with chemotherapeutic agents, following staurosporine-mediated reversible growth inhibition in normal cells. Here we set out to determine if the kinetics of staurosporine-mediated growth inhibition is specifically targeted to the G1 phase of cells, and if such G1 arrest requires the activity of wild-type pRb. Normal human mammary epithelial and immortalized cells with intact pRb treated with low concentrations of staurosporine arrested in the G1 phase of the cell cycle, whereas pRb-defective cells showed no response. The duration of G 1 and transition from G1 to S phase entry were modulated by staurosporine in Rb-intact cells. In pRb+ cells, but not in Rb cells, low concentrations of staurosporine also resulted in a significant decrease in cyclin-dependent kinase 4 (CDK4) expression and activity. To directly assess the role of pRb in staurosporine-mediated G1 arrest, we subjected wild-type (Rb+/+) and pRb-/- mouse embryo fibroblasts (MEFs) to staurosporine treatments. Our results show that whereas Rb+/+ MEFs were particularly sensitive to G1 arrest mediated by staurosporine, pRb-/- cells were refractory to such treatment. Additionally, CDK4 expression was also inhibited in response to staurosporine only in Rb+/+ MEFs. These results were recapitulated in breast cancer cells treated with siRNA to pRb to down-regulate the pRb expression. Collectively, our data suggest that treatment of cells with nanomolar concentrations of staurosporine resulted in down-regulation of CDK4, which ultimately leads to G1 arrest in normal human mammary epithelial and immortalized cells with an intact pRb pathway, but not in pRb-null/defective cells.
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U2 - 10.1158/0008-5472.CAN-06-1809
DO - 10.1158/0008-5472.CAN-06-1809
M3 - Article
C2 - 17018634
AN - SCOPUS:33750289449
SN - 0008-5472
VL - 66
SP - 9744
EP - 9753
JO - Cancer Research
JF - Cancer Research
IS - 19
ER -