Radiosensitizers are introduced to boost cytotoxicity against tumor cells while having much less toxicity on normal cells.  The radio sensitizing properties of methanolic extracts of Euphorbia pulcherrima and Euphorbia heterophylla against a hepatocellular cancer cell line were investigated in this work (HepG2). The cytotoxic effect of E. pulcherrima and E. heterophylla combined with ionizing radiation (IR) were detected. Caspase-3 levels, Bcl₂, Bax & P53 gene expression and Annexin V-FITC apoptosis test were determined. The combination of these extracts and IR showed a considerably higher cytotoxic effect than the one using either extracts or IR alone. There is a substantial increase of Bax & P53 a combined with decrease in Bcl2.  In comparison to the control, there is a 12 to 9 fold increase in total active caspase-3. Both extracts increased the proportion of annexin-positive apoptotic cells from 1.69 percent to 17.22 percent and 14.07 percent, respectively. The combination of extracts and IR showed 17 and 11 folds higher p53 level compared to control in the nucleus, respectively.
These results showed that combined E. Pulcherrimaand E. Heterophyllaand IR contribute to increased cytotoxic effects on the HPG2. It can be suggested that these extracts can be used as radio-sensitizers.