Novel sulfonyl-substituted tetrandrine derivatives for colon cancer treatment by inducing mitochondrial apoptosis and inhibiting PI3K/AKT/mTOR pathway

Tetrandrine (TET) possesses multiple pharmacological activities and could suppress tumor proliferation via PI3K pathway inhibition. However, inferior antitumor activity and potential toxicity limit its clinical application. In the present study, a series of 14-sulfonamide and sulfonate TET derivatives were designed, synthesized, and evaluated for biological activities. Through structural-activity relationship studies, compound 3c with α, β-unsaturated carbonyl group exhibited the most potent activity against all tested tumor cell lines (including Hela, HCT116, HepG2, MCF-7, and SHSY5Y), as well as negligible toxicity against normal cell lines LO2 and HEK293. Additionally, compound 3c effectively inhibited HCT116 and CT26 cell proliferation in vitro with increased cell proportion in the G2/M phase, activated the mitochondrial apoptosis pathway, and induced colon cancer cell apoptosis by suppressing the PI3K/AKT/mTOR pathway. The further molecular docking results confirmed that compound 3c is potentially bound to multiple residues in PI3K with a stronger binding affinity than TET. Ultimately, compound 3c dramatically suppressed tumor growth in the CT26 xenograft tumor model, without noticeable visceral toxicity detected in the high-dose group. In summary, compound 3c might present new insights for designing new PI3K inhibitors and be a potential candidate for colon cancer treatment.