Rigosertib and Cholangiocarcinoma: A Cell Cycle Affair

Abstract

Rigosertib is multi-kinase inhibitor that could represent an interesting therapeutic option for non-resectable patients with cholangiocarcinoma, a very aggressive hepatic cancer with limited effective treatments. The Western blotting technique was used to evaluate alterations in the expression of proteins involved in the regulation of the cell cycle of cholangiocarcinoma EGI-1 cells. Our results show an increase in EMI1 and Cyclin B protein levels after Rigosertib treatment. Moreover, the phosphorylation of CDK1 is significantly reduced by Rigosertib, while PLK1 expression increased after 24 h of treatment and decreased after 48 h. Finally, we evaluated the role of p53. Its levels increase after Rig treatment, and, as shown in the cell viability experiment with the p53 inhibitor Pifithrin, its activity is necessary for the effects of Rigosertib against the cell viability of EGI-1 cells. In conclusion, we hypothesized the mechanism of the action of Rigosertib against cholangiocarcinoma EGI-1 cells, highlighting the importance of proteins involved in the regulation of cell cycles. The CDK1-Cyclin B complex and p53 play an important role, explaining the Block in the G2/M phase of the cell cycle and the effect on cell viability

Another Brick to Confirm the Efficacy of Rigosertib as Anticancer Agent

“…Cells were cultured in medium without any type of treatment for 24 h and western blot experiments were performed. As shown in Figure 2 , between all the cell lines evaluated, A549 cells had the highest expression of p53 (comparable to the levels of EGI-1 cells in our previous paper [ 19 ], data not shown). Instead, MDA-MB-231 and U87-MG cells presented the lowest level of expression of p53.…”

“…As previously demonstrated, p53 was expressed in the human cholangiocarcinoma EGI-1 cell line and plays a key role in the Rig mechanism of action [ 19 ]. We evaluated p53 expression in A549, MCF-7, MDA-MB-23, RPMI 8226, and U87-MG cells.…”

“…In our previous work, we demonstrated that, in human EGI-1 human cholangiocarcinoma cells, Rig induced the modulation of EMI1, Cyclin B, PLK1, and P-CDK1 proteins [ 19 ]. The level of the same proteins was evaluated in A549 and U87-MG cells after treatment with increasing concentrations of Rig (10 nM, 100 nM, and 1 µM) for 24 and 48 h.…”

“…Furthermore, due to its ability to block cells in the G2/M phase of cell cycle, Rig resulted also in a potent radiosensitizing agent [ 12 , 18 ]. Moreover, we also demonstrated that the main pathway of the Rig mechanism against EGI-1 cells included proteins involved in the regulation of the cell cycle and p53 modulation [ 19 ].…”

Role of protein phosphorylation in cell signaling, disease, and the intervention therapy

“…There are also many multi‐kinase inhibitors that achieve different effects depending on the kinase they inhibit. For example, ilorasertib can inhibit AURKB and VEGF; rigosertib can simultaneously inhibit CDK1, RAS, and MEK1 to affect cell cycle, cell proliferation, and survival 241–243 . Inhibitors with multiple targets can achieve better blocking effects, resulting in more effective therapeutic effects; but at the same time, there will also be a problem of increased side effects due to simultaneous blocking of multiple targets 244 …”