On the other hand, β-carboline alkaloid (Figure 3), isolated from Peganum harmala L., was found to exert its anticancer potential against human promyelocytic leukemia, prostate cancer, and gastric cancer by increasing the levels of Phosphatase and Tensin Homolog (PTEN) and decreasing the levels of ERK [45]. This evidence concerns the gene PTEN and acute promyelocytic leukemia.