A novel, small molecule inhibitor of Hsc70/Hsp70 potentiates Hsp90 inhibitor induced apoptosis in HCT116 colon carcinoma cells

Abstract

Purpose The anti-apoptotic function of the 70 kDa family of heat shock proteins and their role in cancer is well documented. Dual targeting of Hsc70 and Hsp70 with siRNA induces proteasome-dependent degradation of Hsp90 client proteins and extensive tumor specific apoptosis as well as the potentiation of tumor cell apoptosis following pharmacological Hsp90 inhibition. Methods We have previously described the discovery and synthesis of novel adenosine-derived inhibitors of the 70 kDa family of heat shock proteins; the first inhibitors described to target the ATPase binding domain. The in vitro activity of VER-155008 was evaluated in HCT116, HT29, BT474 and MDA-MB-468 carcinoma cell lines. Cell proliferation, cell apoptosis and caspase 3/7 activity was determined for VER-155008 in the absence or presence of small molecule Hsp90 inhibitors. Results VER-155008 inhibited the proliferation of human breast and colon cancer cell lines with GI 50 s in the range 5.3-14.4 lM, and induced Hsp90 client protein degradation in both HCT116 and BT474 cells. As a single agent, VER-155008 induced caspase-3/7 dependent apoptosis in BT474 cells and non-caspase dependent cell death in HCT116 cells. VER-155008 potentiated the apoptotic potential of a small molecule Hsp90 inhibitor in HCT116 but not HT29 or MDA-MB-468 cells. In vivo, VER-155008 demonstrated rapid metabolism and clearance, along with tumor levels below the predicted pharmacologically active level. Conclusion These data suggest that small molecule inhibitors of Hsc70/Hsp70 phenotypically mimic the cellular mode of action of a small molecule Hsp90 inhibitor and can potentiate the apoptotic potential of a small molecule Hsp90 inhibitor in certain cell lines. The factors determining whether or not cells apoptose in response to Hsp90 inhibition or the combination of Hsp90 plus Hsc70/ Hsp70 inhibition remain to be determined.

The dissociation of the Hsp60/pro-Caspase-3 complex by bis(pyridyl)oxadiazole copper complex ( CubipyOXA ) leads to cell death in NCI-H292 cancer cells

“…Hsps can block both the intrinsic and the extrinsic apoptotic pathways through the interaction with proteins involved in the apoptotic process [30,31,33]. For example, high levels of Hsp27, or Hsp70, or Hsp90 inhibit apoptosis by preventing Caspase activation in a variety of cellular models [34][35][36]. However, the molecular mechanism of this anti-apoptotic effect mediated by Hsps is still unclear and it is possible that, under certain circumstances, may be due by a variety of different modulators [34].…”

“…Along this line of thought, inhibition of certain Hsps known to be involved in carcinogenesis has been proposed as a potential anti-cancer treatment strategy worth testing [42][43][44]35]. Furthermore, monitoring the levels of Hsps can be a useful way of following up the response to therapy [6].…”

Gold nanoparticles induce nuclear damage in breast cancer cells, which is further amplified by hyperthermia

“…The subcellular redistribution of the nucleolar protein fibrillarin has been linked to autoschizis in cancer cells [29]; fibrillarin was therefore selected to monitor the impact of GNPs on nucleolar organization. Like nucleoli, molecular chaperones, exemplified by the constitutively synthesized hsc70, and the nuclear transporter cellular apoptosis susceptibility protein (CAS [30]) are critical to nuclear functions and essential for cancer cell viability, proliferation, or migration [31][32][33][34][35][36]. In addition to these proteins, the nuclear lamina and nuclear pore complexes (NPCs) provide sensitive indicators that can be used to monitor changes in cell physiology ( [37,38] and references therein).…”

Cross-Presentation of the Oncofetal Tumor Antigen 5T4 from Irradiated Prostate Cancer Cells—A Key Role for Heat-Shock Protein 70 and Receptor CD91

“…To test this, first we applied to tumor cells before irradiation the small-molecule inhibitor VER155008, which inhibits the activity of both the induced and constitutive forms of Hsp70 (21,22). Tumor cell numbers after 72 hours were only slightly lower when VER155008 was applied to irradiated cells, presumably because cell proliferation was already slowed down by the irradiation.…”