Context: Cucurbitacins are a group of triterpenoids that have a cucurbitane skeleton with a wide range of biological activities.
Objectives: This study evaluated the anticancer properties of one cucurbitacin isolated from Cayaponia racemosa Cong. (Cucurbitaceae), 2β,3β,16α,20(R),25-pentahydroxy-22-oxocucurbita-5-en (1), with in vitro and in vivo models.
Materials and methods: In vitro cytotoxic activity was determined with human leukemia (HL60) and normal blood cells (PBMC). Sarcoma 180 was used as in vivo model.
Results: The cucurbitacin (1) reduced the number of viable cells; however, there was no changed in the number of non-viable cells at 5 µg/mL. Selectivity towards cancer cells was suggested by the absence of activity on normal proliferating lymphocytes at the concentrations tested (IC₅₀ >25 µg/ml). Morphological analysis of compound 1-treated cells showed typical apoptotic features, such as intense deposition of granules in the cytoplasm (eosinophilia), DNA fragmentation and irregularities in the plasma membrane. In addition, the cells treated with compound 1 presented intense vacuolization and disruption of the plasma membrane. Acridine orange/Ethidium bromide staining confirmed these findings, revealing an increased number of apoptotic cells. In the Sarcoma 180 tumor model, compound 1 showed 52 and 62% of antitumor activity, either alone (25 mg/kg/day) or in association with the chemotherapeutic agent 5-FU (10 + 10 mg/kg/day), respectively. Moreover, either alone or associated with 5-FU, treatment with compound 1 caused an increase in spleen weight and morphological alterations related to immunostimulatory properties.
Conclusion: These data indicate that these naturally occurring compounds have anticancer potential.