HIV-derived vectors for therapy and vaccination against HIV.

Despite being at the origin of one of the world's most devastating public health concerns, the Human Immunodeficiency Virus (HIV) has properties that can be harnessed for therapeutic purposes. Indeed, the ability of HIV to efficiently deliver its genome into the nuclear compartment makes it an ideal vector for gene delivery into target cells. The design of so-called HIV-derived vectors, or more generally lentiviral vectors (LVs), consists in keeping only the parts of the virus that ensure efficient nuclear delivery while entirely removing all coding sequences that contribute towards the replication and pathogenesis of the virus: as a result, the vector genome is composed of less than 10% of the original virus genome and exclusively cis-active sequences. Proteins required for the formation of the lentivector particles and for the early steps of viral replication (including Gag- and Pol-derived proteins) are provided in trans. HIV-derived vectors are thus non-replicative virus shells that deliver genes of interest into target cells with high efficiency. Undoubtedly, there is a hopeful twist of fate in our fight against AIDS, which consists in using these vectors to achieve gene therapy and vaccination against HIV itself. This review summarises the current generation of LVs with a special focus on vaccine applications against AIDS. Preclinical data are very encouraging and efforts are ongoing to optimise these vectors, to increase their safety and improve their immunogenicity.

The role of the retinoblastoma protein (Rb) in the nuclear localization of BAG-1: implications for colorectal tumour cell survival.

Although the retinoblastoma susceptibility gene RB1 is inactivated in a wide variety of human cancers, the retinoblastoma protein (Rb) has been shown to be overexpressed in colon cancers, which is linked to the anti-apoptotic function of the protein. However, the mechanisms by which Rb regulates apoptosis are yet to be fully elucidated. We have established that Rb interacts with the anti-apoptotic BAG-1 (Bcl-2 associated athanogene-1) protein, and that a decrease in nuclear localization of BAG-1 is detectable when the interaction between Rb and BAG-1 is disrupted by expression of the E7 viral oncoprotein. Interestingly, although reported as deregulated in colorectal cancers, we have found that BAG-1 expression is also altered in small adenomas, where its localization was found to be predominantly nuclear. In addition, we have established that maintenance of high nuclear BAG-1 in vitro increases the resistance of adenoma-derived cells to gamma-radiation-induced apoptosis. Our work suggests a novel function for Rb, involving modulation of the subcellular localization of BAG-1. We have found predominant nuclear BAG-1 localization in small adenomas, and suggest that BAG-1 may promote colorectal tumour cell survival by making colonic epithelial cells less sensitive to DNA damage.

Nuclear BAG-1 expression inhibits apoptosis in colorectal adenoma-derived epithelial cells.

BAG-1 is an anti-apoptotic protein that is frequently deregulated in a variety of malignancies including colorectal cancer. There are three isoforms: BAG-1L is located in the nucleus, BAG-1M and BAG-1S are located both in the nucleus and the cytoplasm. In colon cancer, the expression of nuclear BAG-1 is associated with poorer prognosis and is potentially a useful predictive factor for distant metastasis. However, the function of BAG-1 in colonic epithelial cells has not been studied. Having previously shown a predominant nuclear localisation of BAG-1 in adenoma-derived cell lines, we wanted to determine the function of nuclear BAG-1 in these non-tumourigenic cells, to identify whether nuclear BAG-1 was implicated in tumour progression in the colon. In the current report we established that nuclear BAG-1 inhibits apoptosis in a colorectal adenoma-derived cell line. We demonstrate that apoptosis induced by gamma-radiation or the vitamin D analogue EB1089 in the non-tumourigenic human colorectal adenoma-derived S/RG/C2 cell line, was preceded by a decrease in nuclear and an increase in cytoplasmic BAG-1 expression. This change in subcellular localisation of BAG-1 was due to the redistribution of the BAG-1M isoform. In addition, we have shown that the maintenance of high nuclear BAG-1 through enforced expression of the nuclear localised BAG-1L isoform enhanced cellular survival after gamma-radiation or exposure to EB1089. Furthermore the expression of cytoplasmic BAG-1S isoform fused with a nuclear localisation signal protected against gamma-radiation induced apoptosis. This demonstrates that nuclear localisation of the BAG-1 protein confers a survival advantage in colorectal adenoma-derived cells and that nuclear BAG-1 could potentially be an important survival factor in colorectal carcinogenesis.