Evidence of a tumour suppressive function of E2F1 gene in human breast cancer.

BACKGROUND: The E2F family of transcription factors are key regulators of genes involved in cell cycle progression, cell fate determination, DNA damage repair and apoptosis. E2F1 is unique in that it contributes both to the control of cellular proliferation and cellular death. Furthermore, unlike other E2Fs, E2F1 responds to various cellular stresses. This study aimed to examine the level of mRNA expression of E2F1 gene in normal and malignant breast tissue and correlate the level of expression to tumour stage. MATERIALS AND METHODS: One hundred and twenty-seven breast cancer tissue and 33 normal tissues were analyzed. Levels of transcription of E2F1 were determined using real-time quantitative PCR, normalized against CK19. Levels of expression were analyzed against TNM stage, nodal involvement, tumour grade and distant metastasis. RESULTS: The levels of E2F1 mRNA were lower in malignant tissues. They declined further with increasing TNM stage. This became statistically significant when TNM stages 3 and 4 were compared to TNM stages 1 and 2 disease (TNM1 vs. TNM3 p = 0.032; TNM1 vs. TNM4 p = 0.032; TNM2 vs. TNM3 p = .019; TNM2 vs. TNM4 p = 0.021). The levels of E2F1 also fell with increasing tumour grade, when comparing grade 2 and 3 with grade 1, however, the differences were not statistically significant. CONCLUSION: These results are highly suggestive of the role of E2F1 as a tumour suppressive gene in human breast cancer.

LIGHT, a novel ligand for lymphotoxin beta receptor and TR2/HVEM induces apoptosis and suppresses in vivo tumor formation via gene transfer.

LIGHT is a new member of tumor necrosis factor (TNF) cytokine family derived from an activated T cell cDNA library. LIGHT mRNA is highly expressed in splenocytes, activated PBL, CD8(+) tumor infiltrating lymphocytes, granulocytes, and monocytes but not in the thymus and the tumor cells examined. Introduction of LIGHT cDNA into MDA-MB-231 human breast carcinoma caused complete tumor suppression in vivo. Histological examination showed marked neutrophil infiltration and necrosis in LIGHT expressing but not in the parental or the Neo-transfected MDA-MB-231 tumors. Interferon gamma (IFNgamma) dramatically enhances LIGHT-mediated apoptosis. LIGHT protein triggers apoptosis of various tumor cells expressing both lymphotoxin beta receptor (LTbetaR) and TR2/HVEM receptors, and its cytotoxicity can be blocked specifically by addition of a LTbetaR-Fc or a TR2/HVEM-Fc fusion protein. However, LIGHT was not cytolytic to the tumor cells that express only the LTbetaR or the TR2/HVEM or hematopoietic cells examined that express only the TR2/HVEM, such as PBL, Jurkat cells, or CD8(+) TIL cells. In contrast, treatment of the activated PBL with LIGHT resulted in release of IFNgamma. Our data suggest that LIGHT triggers distinct biological responses based on the expression patterns of its receptors on the target cells. Thus, LIGHT may play a role in the immune modulation and have a potential value in cancer therapy.

Effect of serum renotropin on rat glomerular mesangial cell growth in vitro.

In vitro study of rat glomerular mesangial cell growth was carried out to investigate the pattern of serum renotropic stimulation in 5/6 nephrectomized (5/6NT) rats. Incorporation rates of 3H-TdR, 3H-UR and 3H-Leu into mesangial cells were used as parameters to measure serum renotropic stimulation. Renotropin activity increased immediately after 5/6NT, reaching peak at 48 h, and was succeeded by a rapid decline at 96 h postoperatively. A second rise occurred on the 7th day, followed by gradual decrement. It seemed evident that the serum obtained 48 h after 5/6NT surgery was capable of stimulating the uptake of 3H-TdR, 3H-UR and 3H-Leu by the mesangial cells (MCs). It may be concluded that renotropin promotes DNA, RNA and protein synthesis of MCs. The prolonged and constant effect of serum renotropin on MCs might be one of the important mechanisms in progressive sclerosis of the remaining kidney after subtotal nephrectomy.

VEGI, a novel cytokine of the tumor necrosis factor family, is an angiogenesis inhibitor that suppresses the growth of colon carcinomas in vivo.

A novel member of the tumor necrosis factor (TNF) family has been identified from the human umbilical vein endothelial cell cDNA library, named vascular endothelial growth inhibitor (VEGI). The VEGI gene was mapped to human chromosome 9q32. The cDNA for VEGI encodes a protein of 174 amino acid residues with the characteristics of a type II transmembrane protein. Its amino acid sequence is 20-30% identical to other members of the TNF family. Unlike other members of the TNF family, VEGI is expressed predominantly in endothelial cells. Local production of a secreted form of VEGI via gene transfer caused complete suppression of the growth of MC-38 murine colon cancers in syngeneic C57BL/6 mice. Histological examination showed marked reduction of vascularization in MC-38 tumors that expressed soluble but not membrane-bound VEGI or were transfected with control vector. The conditioned media from soluble VEGI-expressing cells showed marked inhibitory effect on in vitro proliferation of adult bovine aortic endothelial cells. Our data suggest that VEGI is a novel angiogenesis inhibitor of the TNF family and functions in part by directly inhibiting endothelial cell proliferation. The results further suggest that VEGI maybe highly valuable toward angiogenesis-based cancer therapy.