Rac3 induces a molecular pathway triggering breast cancer cell aggressiveness: differences in MDA-MB-231 and MCF-7 breast cancer cell lines.

BACKGROUND: Rho GTPases are involved in cellular functions relevant to cancer. The roles of RhoA and Rac1 have already been established. However, the role of Rac3 in cancer aggressiveness is less well understood. METHODS: This work was conducted to analyze the implication of Rac3 in the aggressiveness of two breast cancer cell lines, MDA-MB-231 and MCF-7: both express Rac3, but MDA-MB-231 expresses more activated RhoA. The effect of Rac3 in cancer cells was also compared with its effect on the non-tumorigenic mammary epithelial cells MCF-10A. We analyzed the consequences of Rac3 depletion by anti-Rac3 siRNA. RESULTS: Firstly, we analyzed the effects of Rac3 depletion on the breast cancer cells' aggressiveness. In the invasive MDA-MB-231 cells, Rac3 inhibition caused a marked reduction of both invasion (40%) and cell adhesion to collagen (84%), accompanied by an increase in TNF-induced apoptosis (72%). This indicates that Rac3 is involved in the cancer cells' aggressiveness. Secondly, we investigated the effects of Rac3 inhibition on the expression and activation of related signaling molecules, including NF-κB and ERK. Cytokine secretion profiles were also analyzed. In the non-invasive MCF-7 line; Rac3 did not influence any of the parameters of aggressiveness. CONCLUSIONS: This discrepancy between the effects of Rac3 knockdown in the two cell lines could be explained as follows: in the MDA-MB-231 line, the Rac3-dependent aggressiveness of the cancer cells is due to the Rac3/ERK-2/NF-κB signaling pathway, which is responsible for MMP-9, interleukin-6, -8 and GRO secretion, as well as the resistance to TNF-induced apoptosis, whereas in the MCF-7 line, this pathway is not functional because of the low expression of NF-κB subunits in these cells. Rac3 may be a potent target for inhibiting aggressive breast cancer.

Histone H3 lysine 36 methyltransferase Hypb/Setd2 is required for embryonic vascular remodeling.

HYPB is a human histone H3 lysine 36 (H3K36)-specific methyltransferase and acts as the ortholog of yeast Set2. This study explored the physiological function of mammalian HYPB using knockout mice. Homozygous disruption of Hypb impaired H3K36 trimethylation but not mono- or dimethylation, and resulted in embryonic lethality at E10.5-E11.5. Severe vascular defects were observed in the Hypb(-/-) embryo, yolk sac, and placenta. The abnormally dilated capillaries in mutant embryos and yolk sacs could not be remodeled into large blood vessels or intricate networks, and the aberrantly rounded mesodermal cells exhibited weakened interaction with endothelial cells. The embryonic vessels failed to invade the labyrinthine layer of placenta, which impaired the embryonic-maternal vascular connection. These defects could not be rescued by wild-type tetraploid blastocysts, excluding the possibility that they were caused by the extraembryonic tissues. Consistent with these phenotypes, gene expression profiling in wild-type and Hypb(-/-) yolk sacs revealed that the Hypb disruption altered the expression of some genes involved in vascular remodeling. At the cellular level, Hypb(-/-) embryonic stem cell-derived embryonic bodies, as well as in vitro-cultured human endothelial cells with siRNA-mediated suppression of HYPB, showed obvious defects in cell migration and invasion during vessel formation, suggesting an intrinsic role of Hypb in vascular development. Taken together, these results indicate that Hypb is required for embryonic vascular remodeling and provide a tool to study the function of H3K36 methylation in vasculogenesis/angiogenesis.

Expression of the bcl-2 gene and its significance in human pancreatic carcinoma.

OBJECTIVE: To elucidate the expression of the bcl-2 gene in association with both biological characteristics of human primary pancreatic carcinoma and patient's prognosis. METHODS: The s-p immunohistochemistry assay was used to detect the expression of the bcl-2 gene on paraffin-embedded sections from 97 cases of primary pancreatic carcinoma, 32 cases of pancreatitis, and 21 cases of normal pancreas. RESULTS: Among the 97 cases of pancreatic carcinoma, 70 (72.2%) showed positive staining for the bcl-2 protein. In the 32 cases of pancreatitis, 3 (9.4%) showed positive immunostaining for the bcl-2, and in the normal pancreas cases, 1 (4.8%) showed positive immunostaining for the bcl-2. However, the positive staining rates of the bcl-2 protein were lower in tumor tissue from the patients with metastases and tumor-node-metastasis (TNM) stages III, IV than in those from those with non-metastases, well differentiation, non-invasion and TNM stages I, II. The patients with positive immunostaining of bcl-2 have a longer postoperative survival than those with negative staining. CONCLUSIONS: Pancreatic carcinoma expressed a high positivity for bcl-2. Findings suggested that the overexpression of bcl-2 is related to the carcinogenesis and progression of human pancreatic carcinoma. Bcl-2 might be one of the parameters in terms of biological characteristics and good prognosis in patients with pancreatic carcinoma.