Cell experiment:

HCT116 and HT29 human colon cancer cells are seeded and left to attach overnight. Vehicle control or compound (VER-50589) is added for 1, 4, and 24 h. Attached cells are collected and counted by hemacytometer. Incubation medium (1 mL) and cell pellets are frozen at –80℃ until mass spectrometry analysis[1].

Animal experiment:

HCT116 cells (2-5 million cells per site) are injected s.c. in the flanks of 6- to 8-week-old female NCr athymic mice. Dosing commenced when tumors are well established (~5-6 mm diameter). For combined therapy and pharmacokinetic and pharmacodynamic studies, mice bearing HCT116 xenografts are administered 100 mg/kg VER-50589 i.p. per day for 9 days. Tumor volumes are calculated. On study termination, blood samples are taken, and plasma is separated and stored –80℃. Tumors are excised, weighed, and snap frozen at –80℃[1].

VER-50589 is a potent inhibitor of HSP90 with IC50 value of 21 nM for HSP90β [1].

Heat shock protein 90 (HSP90) is a chaperone protein that stabilizes proteins against heat stress, assists proteins to fold properly and aids in protein degradation. Also, HSP90 stabilizes proteins required for tumor growth.

VER-50589 is a potent HSP90 inhibitor. VER-50589 inhibited recombinant yeast Hsp90 ATPase activity with IC50 value of 143 nM at 400 μM ATP and inhibited recombinant human HSP90β with IC50 value of 821 nM in the presence of the activator AHA1. Also, VER-50589 bound to recombinant human HSP90β with Kd value of 4.5 nM. In human cancer cells, VER-50589 exhibited antiproliferative activity with mean GI50 value of 78 nM. In CH1 human ovarian cells, VER-50589 inhibited cell growth with GI50 value of 32.7 nM. In HT29 cells, VER-50589 exhibited extensive glucuronidation and increased glucuronide levels by 50-fold, which were responsible for the resistance. In CH1doxR cells that were resistant to doxorubicin, VER-50589 exhibited similar cellular GI50 value compared with CH1 cells. In HCT116 colon cancer cells, VER-50589 caused G1 and G2-M block. Also, VER-50589 induced cytostasis and apoptosis [1].

In athymic mice bearing OVCAR3 human ovarian ascites tumors, VER-50589 completely inhibited HSP90. In mice bearing HCT116 colon carcinoma xenografts, VER-50589 (100 mg/kg) reduced tumor volume by 30% and tumor weight by 26%. Also, VER-50589 reduced expression of ERBB2 and C-RAF [1].

Reference:
[1].  Sharp SY, Prodromou C, Boxall K, et al. Inhibition of the heat shock protein 90 molecular chaperone in vitro and in vivo by novel, synthetic, potent resorcinylic pyrazole/isoxazole amide analogues. Mol Cancer Ther, 2007, 6(4): 1198-1211.