Growth inhibition of human osteosarcoma (OS) cell lines by cucurbitacin B. (A) Chemical structure of cucurbitacin B. (B) Dose-dependent antiproliferative activity of cucurbitacin B against seven human OS cell lines (U2OS, G292, MG-63, HT-161, HOS, SAOS-2, and SJSA) as measured by MTT assay after 48 h of exposure. Measurements repeated in triplicates. Data represent the mean ± standard deviation (SD; error bars).