Overexpression of long non-coding RNA MEG3 suppresses breast cancer cell proliferation, invasion, and angiogenesis through AKT pathway.

Long non-coding RNA MEG3 has been identified as a tumor suppressor which plays important roles in tumorigenesis; however, its potential role in breast cancer has not been fully examined. Here, we showed that MEG3 was downregulated in breast cancer tissues and cell lines. Overexpression of MEG3 inhibited breast cancer cell proliferation and invasion, suggesting that MEG3 played an important role in breast cancer progression and metastasis. Moreover, MEG3 upregulation caused marked inhibition of angiogenesis-related factor expression. Conditioned medium derived from MEG3 overexpressed breast cancer cells significantly decreased the capillary tube formation of endothelial cells. Furthermore, elevated expression of MEG3 in breast cancer inhibits in vivo tumorigenesis and angiogenesis in a nude mouse xenograft model. Mechanistically, overexpression of MEG3 results in downregulation of AKT signaling, which is pivotal for breast cancer cell growth, invasion, and tumor angiogenesis. Collectively, these results suggest that MEG3 might suppress the tumor growth and angiogenesis via AKT signaling pathway and MEG3 may serve as a potential novel diagnostic and therapeutic target of breast cancer.

[Inhibition of growth and metastases of human colon cancer xenograft in nude mice by angiogenesis inhibitor endostatin].

BACKGROUND & OBJECTIVE: Tumor angiogenesis is essential for growth and metastases of colon cancer. Angiogenesis inhibitors can induce apoptosis in colon cancer by inhibiting tumor angiogenesis and has strong inhibitory effect both on tumor growth and metastases of human colon cancer. Anti-angiogenic cancer therapy is important for selecting the timing and method of operation and program of complex treatment and enhancing the five-year survival rate of patients with colon cancer. In this study, we aimed to investigate the effects of angiogenesis inhibitor endostatin on the growth and metastases of colon cancer in vivo. METHODS: Metastatic model simulating human colon cancer was established by orthotopic implantation of histologically intact human tumor tissue into colon wall of nude mice. Endostatin was administered s.c. at dose of 0 mg/kg, 5 mg/kg, 10 mg/kg and 20 mg/kg, every day for six weeks. Seven weeks after implantation, the tumor weight and inhibition rates and intratumoral microvessel density (MVD) and apoptotic index (AI) and the presence of metastases are evaluated respectively after the mice were sacrificed. RESULTS: In compared with the untreated controls, growth of the orthotopically implanted tumor was significantly reduced in weight in mice treated with endostatin with an inhibition rate of 0%, 67.9%, 84.0%, and 90.1% at the dosage of 0 mg/kg, 5 mg/kg, 10 mg/kg, and 20 mg/kg, respectively. The MVD also decreased significantly in the treated mice [(12.8 +/- 4.1) versus (5.9 +/- 2.5), (2.2 +/- 1.4) and (0.74 +/- 0.3)]. The AI increased significantly in the treated mice [(3.87 +/- 2.61)%, versus (6.89 +/- 5.18%), (13.24 +/- 4.76)% and (20.97 +/- 9.04)%]. The incidences of peritoneal metastases were also significantly inhibited in the treated mice (90.0% versus 36.4%, 25.0%, and 0%). The incidences of liver metastases were also significantly inhibited in the treated mice (80.0% versus 27.3%, 16.7% and 0%). Tumor metastases to the liver and peritoneaum were also significantly inhibited in a dose-dependent manner (P < 0.05). CONCLUSIONS: Angiogenesis inhibitor endostatin can induce apoptosis in colon cancer by inhibiting tumor angiogenesis and has strong inhibitory effect both on tumor growth and metastases of human colon cancer xenograft in nude mice.