In Vitro and In Vivo Antitumor Activities of Tenacissoside C from Marsdenia tenacissima

Tenacissoside C, a natural bioactive compound of C₂₁ steroidal saponins, was isolated and purified from air-dried stems of Marsdenia tenacissima. In the present study, the MTT assay showed that tenacissoside C exhibited obvious cytotoxicity in K562 cells with IC₅₀ values of 31.4, 22.2, and 15.1 µM for 24, 48, and 72 h, respectively. Flow cytometry analysis indicated that the antiproliferative activity induced by tenacissoside C might be executed via G0/G1 cell cycle arrest and proapoptosis in K562 cells. Western blotting analysis elucidated that: A) Tenacissoside C induced K562 cell cycle (G0/G1) arrest via downregulating cycline D1 protein expression; and B) Tenacissoside C induced K562 cell apoptosis via the mitochondrial pathway by downregulating Bcl-2 and Bcl-xL protein expression, upregulating Bax and Bak protein expression, and activating caspase-9 and caspase-3. In vivo, significant tumor growth inhibition activity of tenacissoside C was observed in K562 cell-bearing nude mice, accompanied by a significant antiangiogenic effect in vivo against K562 cells (a marked decrease in MVD) and associated with enhanced apoptotic cell death (TUNEL staining assay in vivo), both in dose-dependent manners. The treatment with tenacissoside C did not significantly affect body mass and macroscopic examination of the organs in this mouse tumor model.