SGK3-PROTAC1 (0.3 μM) induces 50% degradation of endogenous SGK3 within 2 h, with maximal 80% degradation observed within 8 h, accompanied by a loss of phosphorylation of NDRG1, an SGK3 substrate. Low doses of SGK3-PROTAC1 (0.1−0.3 μM) restores sensitivity of SGK3 dependent ZR-75-1 and CAMA-1 breast cancer cells to Akt and PI3K inhibitors, whereas the cis epimer analogue incapable of binding to the VHL E3 ligase has no impact. SGK3-PROTAC1 suppresses proliferation of ZR-75-1 and CAMA-1 cancer cell lines treated with a PI3K inhibitor more effectively than could be achieved by a conventional SGK isoform inhibitor.
