Scott M. Thompson BA, Presenter: Nothing to Disclose

Matthew Raymond Callstrom MD, PhD, Abstract Co-Author: Research Grant, Thermedical, Inc Research Grant, General Electric Company Research Grant, Siemens AG Research Grant, Galil Medical Ltd

Kim Butters, Abstract Co-Author: Nothing to Disclose

Danielle Jondal, Abstract Co-Author: Nothing to Disclose

David Proia PhD, Abstract Co-Author: Employee, Synta Pharmaceuticals Corp

Ju-Seog Lee, Abstract Co-Author: Nothing to Disclose

Snorri Thorgeirsson, Abstract Co-Author: Nothing to Disclose

Lewis R. Roberts MBChB, PhD, Abstract Co-Author: Research Grant, Ariad Pharmaceuticals, Inc Research Grant, Bayer AG Research Grant, Bristol-Myers Squibb Company Research Grant, Gilead Sciences, Inc Consultant, Gilead Sciences, Inc Research Grant, Inova Diagnostics, Inc Consultant, Inova Diagnostics, Inc Consultant, Nordion, Inc Research Grant, Nordion, Inc Research Grant, Wako Life Sciences, Inc Consultant, Wako Life Sciences, Inc

David Arthur Woodrum MD, PhD, Abstract Co-Author: Nothing to Disclose

Heat shock protein 90 (HSP90) regulates numerous oncogenic signaling pathways, thereby inhibiting cancer cell death and promoting cell survival under conditions of cell stress such as thermal ablation. The aim of the present study was to test the hypothesis that inhibition of HSP90 enhances heat stress induced hepatocellular carcinoma (HCC) cell killing.

All studies approved by the Institutional Review Board. Microarray analysis was performed on 139 pairs of tumor and benign liver samples from primary human HCCs to assess for HSP90α/β mRNA expression and survival by HSP90α/β expression was analyzed by Kaplan Meier method. The poor prognostic N1S1 and better prognostic AS30D HCC cell lines were pre-treated with a dose-titration of the HSP90 inhibitor ganetespib or vehicle followed by sublethal heat stress (45.0°C) or control (37°C) for 10 minutes. Cell viability and clonogenic survival were assessed using WST-1 and colony formation assays (N=3). Cell death and heat stress induced oncogenic signaling were assessed using Caspase-Glo 3/7 assay and western immunoblotting.

HSP90α and HSP90β were overexpressed in tumor compared to benign adjacent tissue in 72% and 58% of HCC patients, respectively, and patients with high tumor expression of HSP90α had a significantly worse overall survival (p<0.01). Inhibition of HSP90 enhanced heat stress induced HCC cell killing over heat stress or drug alone in both cell lines (p<0.01) and prevented clonogenic survival following sublethal heat stress. Ganetespib in combination with heat stress induced a 4-fold increase in caspase 3/7 activity in the AS30D but not the N1S1 cell line. Western immunoblotting demonstrated that HSP90 inhibition increased expression of autophagy and apoptosis markers LC3B and cleaved caspase 3 and blocked heat stress induced AKT and ERK signaling in the AS30D cell line and increased LC3B expression in the N1S1 cell line.

These data demonstrate that HSP90α is overexpressed in a majority of HCC patients which correlates with poor prognosis. Inhibition of HSP90 with the small molecule inhibitor ganetespib enhances heat stress induced HCC cell killing by apoptosis and/or autophagy depending on the molecular subtype of HCC.

HSP90 inhibition with ganetespib in combination with thermal ablation may be a promising therapeutic strategy to enhance ablation induced HCC cell killing across diverse molecular subtypes of HCC.

Thompson, S, Callstrom, M, Butters, K, Jondal, D, Proia, D, Lee, J, Thorgeirsson, S, Roberts, L, Woodrum, D, Heat Shock Protein 90 (HSP90) Overexpression Correlates with Poor Hepatocellular Carcinoma Patient Survival and Targeted Inhibition of HSP90 Enhances Heat Stress Induced HCC Killing by Apoptosis and Autophagy.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14002522.html