Targeted knockdown of Bcl2 in tumor cells using a synthetic TRAIL 3'-UTR microRNA

The role of Bax and Bcl-2 in gemcitabine-mediated cytotoxicity in uveal melanoma cells

Gemcitabine (GEM), a new cytotoxic agent, was shown to be effective against uveal melanoma (UM) which is noted for its resistance to chemotherapy. In this study, we found the different sensitivities to GEM in UM cell lines and identified apoptotic cell death as the cause of GEM cytotoxicity. Both UM cell lines showed an increase in Bax protein levels and activation of cleaved Caspase 3. Additionally, SP6.5 cells showed a gradual increase in Bcl-2 expression over time, whereas VUP cells showed almost none. After interfering in the expression of Bcl-2, the sensitivity to GEM was obviously enhanced in SP6.5 cells. These results suggest that an increase in Bax plays a crucial role in apoptotic cell death induced by GEM in the absence of p53. Moreover, inhibition of Bcl-2 expression can efficiently enhance the cytotoxic effect of, and sensitivity to, GEM in UM cells.

Enhanced therapeutic efficacy of vitamin K2 by silencing BCL-2 expression in SMMC-7721 hepatocellular carcinoma cells

Vitamin K2 (VK2) exerts cell growth inhibitory effects in various human cancer cells such as SMMC-7721 hepatocellular carcinoma (HCC) cells. BCL-2 is an antiapoptotic protein that is frequently overexpressed in numerous tumors. Modulation of multiple antiapoptotic signaling pathways involving BCL-2, which are related to growth factor-stimulated signal transduction in cell survival, is essential for enhancement of the cytotoxic effect of anticancer drugs. In this study, we tested a new strategy of gene therapy by combining BCL-2 siRNA with VK2. In SMMC-7721 HCC cells, the combined treatment significantly enhanced cytotoxicity compared with treatment with either VK2 or siBCL-2 alone. We found that combined treatment induced a significantly different level of G2 stage inhibition. Furthermore, the p53 protein was overexpressed 24 h subsequent to combination treatment, and p21 was clearly increased at 36 h as a consequence of the increased p53 activity. In conclusion, these data suggest that the antitumor effect of VK2 may be improved by silencing BCL-2 expression in SMMC-7721 HCC cells and provides support for the combined use of VK2 and siBCL-2 as a promising approach in cancer gene therapy.

Potentiation of tumor radiotherapy by a radiation-inducible oncolytic and oncoapoptotic adenovirus in cervical cancer xenografts

The p53 tumor suppressor pathway is impaired in more than 90% of cervical cancers and cancer-derived cell lines as a result of infection by human papillomavirus (HPV). The HPV E6 oncoprotein forms complexes with p53 and promotes its degradation via ubiquitin-dependent mechanism. In our study, we attempted to improve the clinical outcomes of this combined therapy by modifying the p53-targeted adenovirus to become radiation-responsive. The antitumor adenovirus was constructed by inserting a radiation-responsive expression cassette composed of the promoter of early growth response-1 (Egr-1) and the proapoptotic protein TRAIL. We showed that the addition of adenovirus containing Egr-1/TRAIL significantly increased cell death and apoptosis caused by radiotherapy. In mice bearing xenograft tumors, intratumoral administration of the Egr-1/TRAIL adenovirus followed by radiation significantly reduced tumor growth and enhanced tumor survival. Our Egr-1/TRAIL adenoviral gene product may offer a novel "one-two punch" tumor therapy for cervical cancers not only by potentiating radiation treatment but also by preserving p53 defect-specific tumor killing of the oncolytic adenovirus.

SP1 suppresses phorbol 12-myristate 13-acetate induced up-regulation of human regucalcin expression in liver cancer cells

There is a growing evidence that regucalcin (RGN) plays a multifunctional role in liver cancer cells. Previous reports showed that the presence of phorbol 12-myristate 13-acetate (PMA) caused a significant increase in RGN mRNA expression and promoter activity in rat hepatoma cells. In this study, we confirmed that human RGN is also up-regulated by PMA treatment independent of translation, and we identified the mechanism by which PMA up-regulates the expression of human RGN via driving SP1 away from a SP1 motif located within -188/-180 of the promoter in HepG2 cells. Overexpression of SP1 dramatically reduces PMA-induced up-regulation of both internal expression of mRNA and promoter activity, whereas knockdown of SP1 has the opposite effect. Therefore, the present study delineates the fundamental elements in the promoter which will be helpful in the future studies on the regulation of RGN expression in liver cancer.