Therapeutic Effect of a Ribosome-Inactivating Protein from Mirabilis jalapa L. against Mouse Skin Cancer Induced by Co-Carcinogen Dimethylbenzantracene and UVB Radiation

Mirabilis jalapa L. leave has been reported to contain Ribosome-inactivating protein (RIP), which demonstrated to have in vitro cytotoxic effect on cancer cell lines and prevention effect against skin cancer. This research examined the therapeutic effect of protein fraction containing RIP isolated from Mirabilis jalapa L. (MJ protein) against skin cancer. MJ protein was isolated using phosphate buffer pH 7.2, and then tested for its activity to cleave supercoiled DNA. To induce the skin cancer, BALB/c mice were topically exposed to single dose of 0.2 mg/0.1 ml dimethylbenzanthracene (DMBA) and UVB radiation (daily dose, 0.4 J/cm²) for 60 days. Therapeutic effect of MJ protein was examined by observing the incidence, multiplicity, and regression of tumor and followed by analyzing the expressions of bcl2 using immunohistochemistry technique. The results showed that MJ protein therapy (doses of 0.3/0.1ml and 1.2mg/0.1ml) was able to decrease the incidence of skin cancer (SCC) by 75.5% and tumor nodule regression (approximately 35.3%) at 10 weeks of therapy, while the dose of 1.2mg/0.1ml decreased the tumor nodule diameter by 17.36%. In addition, 0.3 mg /0.1 ml and 1.2 mg/0.1ml of MJ protein were able to significantly decrease the expressions of bcl2 protein at 82.38% and 78.40% compared to post UVB control sample (10 weeks of therapy). However, there was no significant difference (p > 0.05) among the dose groups.