Abstract. Euphorbia fischeriana Steud, a traditional Chinese medicine, has been shown to inhibit the growth of various cancers by the induction of apoptosis and cell cycle arrest. The purpose of the present study was to investigate the association between the phosphoinositide-3-kinase (PI3K)/protein kinase B (Akt) signaling pathway and the inhibitory effect of Euphorbia fischeriana Steud on the growth and metastasis of melanoma B16 cells in vitro, and the underlying mechanisms. MTT assay results indicated that Euphorbia fischeriana Steud inhibited the growth of B16 cells in a time-and dose-dependent manner. Flow cytometric analysis revealed that Euphorbia fischeriana Steud markedly induced apoptosis of the B16 cells, with arrest at the G0/G1 phase of the cell cycle. In addition, in a Transwell assay Euphorbia fischeriana Steud significantly suppressed the migration of B16 cells. Western blot analysis revealed that the expression levels of phosphatase and tensin homolog (PTEN) were upregulated, and the phosphorylation of Akt was downregulated, which resulted in inhibition of the PI3K/Akt signaling pathway and the eventual suppression of its downstream targets, such as matrix metalloproteinase-2 mRNA, in B16 cells. The results demonstrated that Euphorbia fischeriana Steud inhibited the growth and migration of B16 cells, possibly via modulation of the PI3K/Akt signaling pathway and upregulation of PTEN expression levels, in addition to downregulation of p-Akt expression. The aforementioned findings suggest that Euphorbia fischeriana Steud may have broad therapeutic applications in the treatment of malignant melanoma.
IntroductionMalignant melanoma has become a frequently occurring malignancy with an annual increase of ~3% (1). The majority (~90%) of patients with early detected melanoma are curable; however, the efficiency of clinical drugs in the treatment of patients with advanced metastatic melanoma is <20% (2), and the 5-year survival rate is <5%, with a median survival time of only 2-8 months (3,4). Numerous studies have confirmed that the poor prognosis of malignant melanoma is primarily attributable to the high incidence of distant metastasis and a strong capacity for invasion (5-7). Therefore, the development of more effective therapies for the inhibition of metastasis presents a challenge for the treatment of malignant melanoma.Chemotherapy has a significant role in the treatment of cancer. However, the majority of chemotherapy drugs also destroy normal cells, leading to adverse effects (8). Therefore, the identification of natural compounds with a wide range of anticancer activities, high selectivity for the destruction of cancer cells and low toxicity of normal cells is of importance in cancer research. Euphorbia fischeriana Steud (also known as lang-du), a herbaceous plant used in traditional Chinese medicine (TCM), has demonstrated inhibitory effects through its capacity to induce apoptosis, suppress growth and cause cell cycle arrest when assessed within several cancer cell lines, including leukemia a...