Sangre de grado Croton palanostigma induces apoptosis in human gastrointestinal cancer cells

Abstract

Sangre de grado is an ethnomedicinal red tree sap obtained from Croton spp. that is used to treat gastrointestinal ulcers, cancer and to promote wound healing. To evaluate the potential role of sangre de grado (SdG) in cancer we examined its effects on human cancer cells, AGS (stomach), HT29 and T84 (colon). Viability of cells treated with SdG (10–200 μg/ml) decreased (P<0.01) in a dose dependent manner measured over a 24-h period. Cell proliferation at 48 h decreased (P<0.01) in all cells treated with SdG (>100 μg/ml). When cells in suspension were treated with SdG (100 μg/ml) cell adherence was severely compromised (>85%). Cells treated with SdG (100 μg/ml) underwent apoptosis as detected by nucleus condensation and DNA fragmentation determined by ELISA, and flow cytometry. Morphological changes as assessed by acridine orange. These effects were similar to that observed with Taxol (30 μM). A significant alteration of microtubular architecture was equally observed in both stomach and colon cancer cells exposed to SdG (100 μg/ml). The induction of apoptosis and microtubule damage in AGS, HT29 and T84 cells suggest that sangre de grado should be evaluated further as a potential source of anti-cancer agents.

Introduction

Sangre de grado (Croton palanostigma), a member of the family Euphorbiaceae, is one of the most widely used medicinal plants of the South American tropics. The Croton genus includes several species (Croton lechleri, C. palanostigma, and C. draconoides) all of which contain a red viscous sap that is obtained from making cuts in the bark (Duke and Vasquez, 1994). The sap is reported to have a wide range of pharmacological and physiological actions (Chen et al., 1994; Desmarchelier et al., 1997; Phillipson 1995). It is used for wound healing (Porras-Reyes et al., 1993), controlling diarrhea (Gabriel et al., 1999; Holodniy et al., 1999), gastric ulcer healing and as a treatment for intestinal inflammation (Miller et al., 2000).

Several compounds have been isolated previously from sangre de grado (Cai et al., 1991, Cai et al., 1993a, Cai et al., 1993b). It has been reported that the bark sap contains only one alkaloid, Taspine, (Bettolo and Scarpati, 1979) which has been claimed to be the active principle responsible for the anti-inflammatory and wound healing properties (Perdue et al., 1979; Vaisberg et al., 1989). However, the wound healing activity has also been attributed to the lignan 3′4′-O-dimethylcedrusin (Pieters et al., 1993).

Recent findings from our laboratory showed the ability of sangre de grado promotes healing of gastric ulcers in rats and impairs the intestinal secretory response to capsaicin in guinea pig ileum (Miller et al., 2000). Thus, it appears that SdG has generalized benefits in gastrointestinal function. However, an evaluation of its ethnomedical application in cancer is lacking. A number plants of the family Euphorbiaceae have been used to treat cancers and tumors from at least the time of Hippocrates, and scientific references have been published in several countries (Iancu et al., 2000; Itokawa et al., 1991; Kupchan et al., 1976).

In our continuing efforts to evaluate the anti-cancer activity of medicinal plants from the Amazon, we collected ethnomedical information from tropical regions of South America and that led us to investigate the Croton spp., sangre de grado, which is used to treat certain forms of gastrointestinal cancers. It has been claimed that the growth inhibitory or antiproliferative effects of sangre de grado are associated with its cytotoxic and anti-tumor activity (Chen et al., 1994). However, the mechanisms of this beneficial effect have not been elucidated.