Structural optimization and structure-activity relationship (SAR) analysis were then carried out on the virtual hit of VS-8 with potent activity, which resulted in the discovery of compound 10 as a more potent regulator of Hsp90-Cdc37 interaction with a promising inhibitory effect (IC<sub>50</sub> = 27 μM), a moderate binding capacity (K<sub>D</sub> = 40 μM) and a preferable antiproliferative activity against several cancer lines including MCF-7, SKBR3 and A549 cell lines (IC<sub>50</sub> = 26 μM, 15 μM and 38 μM respectively).
Putative biomarkers such as cell cycle related genes (Cdc37), cancer cell adhesion (Glycam 1, integrin alpha8, integrin alphaX and Clec4n), signal transduction (Tlr2, IL-33, and Ccbp2), migration (Ccr1, Ccl6, and diaphorase 1 (Cyb5r3) and cancer development (epiregulin) can be useful for diagnosis and as prognosis markers and some of the target molecules can be applied for prevention of cancer.
Furthermore, CDC37 silencing sensitises cancer cells to HSP90 inhibitors by potentiating kinase client depletion and the induction of apoptosis, suggesting that simultaneously modulating HSP90 and CDC37 could be beneficial.
These results support an essential role for CDC37 in concert with HSP90 in maintaining oncogenic protein kinase clients and endorse the therapeutic potential of targeting CDC37 in cancer.
In contrast to HSP90-directed agents, Cdc37 targeting seems to affect cancer cells through a distinct mechanism and does not significantly deplete the intracellular levels of most known HSP90 client proteins.