Cancer cell responses to Hsp70 inhibitor JG-98: Comparison with Hsp90 inhibitors and finding synergistic drug combinations

Hsp70 is a promising anti-cancer target. Our JG-98 series of Hsp70 inhibitors show anti-cancer activities affecting both cancer cells and tumor-associated macrophages. They disrupt Hsp70 interaction with a co-chaperone Bag3 and affect signaling pathways important for cancer development. Due to a prior report that depletion of Hsp70 causes similar responses as depletion of Hsp90, interest to Hsp70 inhibitors as drug prototypes is hampered by potential similarity of their effects to effects of Hsp90 inhibitors. Here, using the Connectivity Map platform we demonstrate that physiological effects of JG-98 are dissimilar from effects of Hsp90 inhibitors, thus justifying development of these compounds. Using gene expression and ActivSignal IPAD platform, we identified pathways modulated by JG-98. Some of these pathways were affected by JG-98 in Bag3-dependent (e.g. ERK) and some in Bag3-independent manner (e.g. Akt or c-myc), indicating multiple effects of Hsp70 inhibition. Further, we identified genes that modulate cellular responses to JG-98, developed approaches to predict potent combinations of JG-98 with known drugs, and demonstrated that inhibitors of proteasome, RNApol, Akt and RTK synergize with JG-98. Overall, here we established unique effects of novel Hsp70 inhibitors on cancer cell physiology, and predicted potential drug combinations for pre-clinical development.