As shown in Figure 3B, knockdown of PKC, but not that PKCB or PKC, significantly decreased the apoptosis induced by the combination of PMA and apicularen A. These results demonstrate that PKC mediates the synergistic effect of PMA on apicularen A induced cell death in HeLa cells. PMA this website increases apicularen A Inhibitors,Modulators,Libraries mediated tubulin down regulation We previously reported that the mechanism of apicularen A induced apoptotic cell death in human HM7 colon can cer cells partially involved a decrease in intracellular tubulin levels. Thus, we investigated whether PMA in creases apicularen A induced apoptotic cell death by fur ther down regulating tubulin. Apicularen A decreased total tubulin protein levels in a time dependent manner.

At 48 hours, the combination of PMA and apicularen A decreased tubulin protein levels to a greater extent than apicularen A alone, while PMA alone had no effect. Similar results were obtained for B tubulin. Since apicularen A down regulates Inhibitors,Modulators,Libraries tubulin levels by decreasing tubulin mRNA levels in HM7 cells, tubulin mRNA levels were assessed by RT PCR in cells exposed to PMA and apicularen A. PMA did not affect tubulin mRNA levels in apicularen A treated cells. Microtubule architecture was assessed by possibility that PKC activation might also be responsible for the effect of PMA and apicularen A on tubulin protein levels was considered. HeLa cells were pretreated with Ro31 8220 and then exposed to apicularen A in the pres ence or absence of PMA. As expected, inhibition of PKC activity by Ro31 8220 partially restored Inhibitors,Modulators,Libraries tubulin levels.

Taken together, these results suggest that the potentiation of apicularen A induced apoptotic cell death by PMA is associated with decreased tubulin protein levels. Discussion Inhibitors,Modulators,Libraries The present study shows that PMA increases the cyto toxicity of apicularen A in HeLa cells. PKC inhibition completely blocked the synergistic Inhibitors,Modulators,Libraries effect of PMA on apicularen A induced cytotoxicity and tubulin down regulation. Specific knockdown of PKC isotypes revealed that PKC is the unique mediator of that effect among PKC family members. PMA induces apoptotic cell death in several kinds of cells. In addition, the combination of PMA and anticancer drugs increases cytotoxicity, suggest ing that PMA may be suitable as an anticancer agent within a drug combination regimen. In this study, al though PMA alone did not induce cell death, it increased the cell death induced by apicularen A synergistically. This effect was completely blocked by the PKC inhibitor selleckchem Oligomycin A Ro31 8220, indicating that PKC is involved in the synergistic mechanism. Among PKC isotypes, PKC mainly promotes apoptosis, however, since Ro31 8220 does not inhibit PKC, we had to consider that other PKC isotype may be involved in the synergy.