Billadeau serves on the Scientific Advisory Board of Actuate Therapeutics Inc

Billadeau serves on the Scientific Advisory Board of Actuate Therapeutics Inc. siRNA depletion of GSK-3 kinases Rabbit polyclonal to ZNF562 impaired the activation of ATR leading to the phosphorylation and activation of Chk1. Mechanistically, depletion or knockdown of GSK-3 kinases resulted in the degradation of the ATR-interacting protein TopBP1, thus limiting the activation of ATR in response to single-strand DNA damage. Conclusions: These data identify a previously unknown role for GSK-3 kinases in the regulation of the TopBP1/ATR/Chk1 DNA damage response pathway. The data also support the inclusion of patients with PDAC in clinical studies of 9-ING-41 alone and in combination with gemcitabine. and suppressed tumor growth 11, 14, 15. Using a genetically engineered mouse model we demonstrated that GSK-3 contributes to KRas-driven tumor-promoting pathways that are required for the initiation of acinar-to-ductal metaplasia 16. These data support the potential therapeutic benefit of targeting GSK-3 in human pancreatic cancer. GSK-3 inhibitor tool compounds have been developed and tested for their abilities to sensitize pancreatic cancer cells to gemcitabine. Previous studies in hematopoietic cells 17 and pancreatic cancer cells 18 showed that activation of the Akt-GSK-3 pathway is a key signaling event for gemcitabine resistance. The GSK-3 inhibitor tool compound Bio E260 19 could prevent the sensitization to gemcitabine-induced cell death by zidovudine 18. Lithium, a GSK-3 inhibitor, synergistically enhances the anti-cancer effect of gemcitabine by promoting the ubiquitin-dependent proteasome degradation of Gli1 20, 21. The GSK-3 inhibitor AR-A014418 22 also sensitizes pancreatic cancer cells to gemcitabine with altered expression of genes involved in DNA repair 23. Interestingly, while GSK-3 inhibition could disrupt NFB activity in pancreatic cancer E260 cells it did not significantly sensitize these cells to gemcitabine 24. The GSK-3 inhibitor LY2090314 25 was clinically evaluated in patients for metastatic pancreatic cancer but its adverse PK properties ended its development. We have shown that a series of novel GSK-3 inhibitors, from which the clinical candidate, 9-ING-41 emerged, {impaired PDAC and ovarian cancer cell proliferation and survival 26,, but its effects on PDAC and mechanism of action are not known. Herein, we provide evidence that 9-ING-41, which is currently being evaluated in a phase 1/2 trial in patients with advanced cancer, reduces proliferation of PDAC cells and xenografts and significantly increase tumor-killing effect when combined with chemotherapies in resistant glioblastoma and breast cancer 27, 29, 32, 33. To examine its anti-tumor proliferation effect on pancreatic cancer cells, 5 previously described PDAC cell lines 30 and 3 recently developed pancreatic cancer PDX 28 cell lines were plated and treated with 9-ING-41 in increasing nanomolar concentrations (50 nM, – 2000 nM). Growth suppression was observed in all tested cell lines using a colorimetric, MTS assay after 48 hours (Figure 1A). We next tested the effect of 9-ING-41 in combination with gemcitabine. While 9-ING-41 alone inhibited 6741 proliferation at both 48 and 72 hours, it also synergistically sensitized 6741 (Figure 1B) and 5160 (Supplemental Figure 1A) to gemcitabine as determined by calculating the combination index. To further investigate the cancer cell killing and chemo-sensitizing effect of 9-ING-41, we utilized L3.6 and 6741 in a clonogenic assay (Supplemental Figure S1B and C). L3.6 and 6741 colony numbers decreased in a dose-dependent manner following 9-ING-41 treatment (Figure 1C). When combined with increasing doses of gemcitabine, 9-ING-41 could substantially reduce colony number compared to gemcitabine alone (Figure 1D). Previous studies have shown that 9-ING-41 E260 treatment inhibited the proliferation of ovarian cancer cell lines by induction of apoptosis 27. Therefore, we examined cell apoptosis/necrosis by annexin V/PI staining in 9-ING-41 treated pancreatic cancer cells. As shown in Supplement Figure S2A and S2B, combination of both 9-ING-41 and gemcitabine decreased the number of live cells and increased the population of necrotic cells. Immunoblotting results further confirmed the phenotype of significant cell death in the combination drug group (Supplement Figure S2C). Taken together, these data suggest that 9-ING-41 can suppress cell proliferation and sensitize PDAC cells to gemcitabine and and significantly prolongs survival of mice bearing orthotopic tumors. Mechanistically, we identify a previously unknown role for GSK-3 kinase.

Comments are closed.