BackgroundThe Ras association domain family 1 (RASSF1) gene is a Ras effector encoding two major mRNA forms, RASSF1A and RASSF1C, derived by alternative promoter selection and alternative mRNA splicing. RASSF1A is a tumor suppressor gene. However, very little is known about the function of RASSF1C both in normal and transformed cells.MethodsGene silencing and over-expression techniques were used to modulate RASSF1C expression in human breast cancer cells. Affymetrix-microarray analysis was performed using T47D cells over-expressing RASSF1C to identify RASSF1C target genes. RT-PCR and western blot techniques were used to validate target gene expression. Cell invasion and apoptosis assays were also performed.ResultsIn this article, we report the effects of altering RASSF1C expression in human breast cancer cells. We found that silencing RASSF1C mRNA in breast cancer cell lines (MDA-MB231 and T47D) caused a small but significant decrease in cell proliferation. Conversely, inducible over-expression of RASSF1C in breast cancer cells (MDA-MB231 and T47D) resulted in a small increase in cell proliferation. We also report on the identification of novel RASSF1C target genes. RASSF1C down-regulates several pro-apoptotic and tumor suppressor genes and up-regulates several growth promoting genes in breast cancer cells. We further show that down-regulation of caspase 3 via overexpression of RASSF1C reduces breast cancer cells' sensitivity to the apoptosis inducing agent, etoposide. Furthermore, we found that RASSF1C over-expression enhances T47D cell invasion/migration in vitro.ConclusionTogether, our findings suggest that RASSF1C, unlike RASSF1A, is not a tumor suppressor, but instead may play a role in stimulating metastasis and survival in breast cancer cells.

BackgroundRASSF1A and RASSF1C are two major isoforms encoded by the Ras association domain family 1 (RASSF1) gene through alternative promoter selection and mRNA splicing. RASSF1A is a well established tumor suppressor gene. Unlike RASSF1A, RASSF1C appears to have growth promoting actions in lung cancer. In this article, we report on the identification of novel RASSF1C target genes in non small cell lung cancer (NSCLC).MethodsOver-expression and siRNA techniques were used to alter RASSF1C expression in human lung cancer cells, and Affymetrix-microarray study was conducted using NCI-H1299 cells over-expressing RASSF1C to identify RASSF1C target genes.ResultsThe microarray study intriguingly shows that RASSF1C modulates the expression of a number of genes that are involved in cancer development, cell growth and proliferation, cell death, and cell cycle. We have validated the expression of some target genes using qRT-PCR. We demonstrate that RASSF1C over-expression increases, and silencing of RASSF1C decreases, the expression of PIWIL1 gene in NSCLC cells using qRT-PCR, immunostaining, and Western blot analysis. We also show that RASSF1C over-expression induces phosphorylation of ERK1/2 in lung cancer cells, and inhibition of the MEK-ERK1/2 pathway suppresses the expression of PIWIL1 gene expression, suggesting that RASSF1C may exert its activities on some target genes such as PIWIL1 through the activation of the MEK-ERK1/2 pathway. Also, PIWIL1 expression is elevated in lung cancer cell lines compared to normal lung epithelial cells.ConclusionsTaken together, our findings provide significant data to propose a model for investigating the role of RASSF1C/PIWIL1 proteins in initiation and progression of lung cancer.

To evaluate the clinical efficacy of monoclonal antibody (mAb) 3E10 Fv antibody-mediated p53 protein therapy, an Fv-p53 fusion protein produced in Pichia pastoris was tested on CT26.CL25 colon cancer cells in vitro and in vivo in a mouse model of colon cancer metastasis to the liver. In vitro experiments showed killing of CT26.CL25 cells by Fv-p53 but not Fv or p53 alone, and immunohistochemical staining confirmed that Fv was required for transport of p53 into cells. Prevention of liver metastasis in vivo was tested by splenic injection of 100 nmol/L Fv-p53 10 min and 1 week after injection of CT26.CL25 cancer cells into the portal vein of BALB/c mice. Mice were sacrificed 1 week after the second injection of Fv-p53 and assigned a quantitative metastasis score. Control mice had an average metastasis score of 3.3 F 1.3, whereas mice treated with Fv-p53 had an average metastasis score of 0.8 F 0.4 (P = 0.004). These results indicate that Fv-p53 treatment had a profound effect on liver metastasis and represent the first demonstration of effective full-length p53 protein therapy in vivo. mAb 3E10 Fv has significant clinical potential as a mediator of intracellular and intranuclear delivery of p53 for prevention and treatment of cancer metastasis. [Cancer Res 2007;67(4):1769-74]

High-risk types of human papillomavirus (HPV) cause nearly all cases of cervical cancer. The E6 oncoprotein is produced as a full-length variant (E6) as well as several shorter isoforms (E6*). E6* inhibits certain oncogenic activities of E6, suggesting that it might play an anti-oncogenic role in vivo. To test this, we created E6*-expressing SiHa (HPV+) and C33A (HPV−) cells, then examined the ability of both the parental and E6*-expressing cells to form tumors in nude mice. We found that over-expression of E6* indeed decreased the growth of tumors derived from both SiHa and C33A cells, with the reduction greatest in tumors derived from E6*-expressing SiHa cells. These findings point to multiple anti-oncogenic characteristics of E6*, some of which likely involve down-regulation of the full-length isoform, and others that are independent of HPV. These data represent the first demonstration of biologically-relevant E6* activities distinct from those of the full-length isoform in vivo.