Senexin B

Selective inhibitors of Bcr-Abl (prototype – imatinib mesylate, IM, Gleevec®) cause a therapeutic effect in the treatment of the primary process...Senexin B (SenB) and SNX631 were used for selective inhibition of CDK8/19, to suppress Bcr-Abl – IM, dasatinib, nilotinib, PF-114.Results and DiscussionsIt was found that CDK8/19 inhibition by SenB alone does not have an antiproliferative effect on CML cells...These changes were not demonstrated in KU812, where neither SenB sensitization, nor changes in expression of CKIs and c-Myc level were detected.ConclusionInhibition of CDK8/19 helps to overcome the delay of the cell cycle caused by the Bcr-Abl antagonist in CML cells and increase the death of tumor cells. The absence of general toxicity of CDK8/19 inhibitors during prolonged treatment under experimental conditions allows us to recommend CDK8/19 inhibition with targeted therapy of Bcr-Abl-positive tumors in prospect.

Senexin B, a non-toxic selective inhibitor of cyclin-dependent protein kinases 8 and 19 (CDK8 and CDK19), in combination with γ-photon irradiation in doses of 2-10 Gy increased the death of colon adenocarcinoma cell line HCT116 (intact p53) in a logarithmically growing culture, which was accompanied by the prevention of cell cycle arrest and a decrease of "senescence" phenotype. The effect of senexin B in cells with intact p53 is similar to that of Tp53 gene knockout: irradiated HCT116p53KO cells passed through the interphase and died independently of senexin B. The inhibitor reduced the ability of cells to colony formation in response to irradiation; p53 status did not affect the effectiveness of the combination of radiation and senexin B. Thus, the CDK8/19 inhibitor senexin B increased cell sensitivity to radiotherapy by mechanisms dependent and independent of p53 status.

Selective CDK8/19 inhibitors (senexin B and SNX631) showed synergistic interactions with lapatinib and trastuzumab in a panel of HER2 BrCa cell lines, overcoming and preventing resistance to HER2-targeting drugs. These effects were associated with decreased tumor cell proliferation and altered recruitment of stromal components to the xenograft tumors. These results suggest potential clinical benefit of combining HER2- and CDK8/19-targeting drugs in the treatment of metastatic HER2 BrCa.