Targeting TARP, a novel breast and prostate tumor-associated antigen, with T cell receptor-like human recombinant antibodies.

MHC class I molecules are important components of immune surveillance. There are no available methods to directly visualize and determine the quantity and distribution of MHC/peptide complexes on individual cells or to detect such complexes on antigen-presenting cells in tissues. MHC-restricted recombinant antibodies with the same specificity of T cell receptors (TCR) may become a valuable tool to address these questions. They may also serve as valuable targeting molecules that mimic the specificity of cytotoxic T cells. We isolated by phage display a panel of human recombinant Fab antibodies with peptide-specific, MHC-restricted TCR-like reactivity directed toward HLA-A2-restricted T cell epitopes derived from a novel antigen termed TCRgamma alternative reading frame protein (TARP) which is expressed on prostate and breast cancer cells. We have characterized one of these recombinant antibodies and demonstrated its capacity to directly detect specific HLA-A2/TARP T cell epitopes on antigen-presenting cells that have complexes formed by naturally occurring active intracellular processing of the antigen, as well as on the surface of tumor cells. Moreover, by genetic fusion we armed the TCR-like antibody with a potent toxin and demonstrated that it can serve as a targeting moiety killing tumor cells in a peptide-specific, MHC-restricted manner similar to cytotoxic T lymphocytes.

The role played by key transcription factors in activated mast cells.

The network of transcription factors in mast cells has not been investigated as widely as it has been in other differentiated hematopoietic cells. There are still many mechanisms of transcriptional regulation that need to be fully elucidated to understand how mast cell external stimuli lead to the appropriate physiological responses. Such information could be used to determine potential therapeutic targets for the control of mast cell activation in inflammatory diseases, allergy, and asthma. The aim of this article is to review hallmark studies in the field of transcription factor regulation in mast cells. We elaborate especially on several transcription factors studied in our laboratory in the past decade, including activator protein-1, microphthalmia-associated transcription factor, upstream stimulating factor-2, and signal transducer and activator of transcription 3.

Antiapoptotic function of Bcl-2 in mast cells is dependent on its association with heat shock protein 90beta.

In the present study, we demonstrated that the antiapoptotic function of Bcl-2 in mast cells is significantly dependent on its association with the heat shock protein 90beta (Hsp90beta). Dissociation of these 2 proteins inhibits the antiapoptotic activity of Bcl-2 by initiating the release of cytochrome c from mitochondria into cytosol and increasing the activity of caspase 3 and caspase 7, resulting in mast-cell apoptosis. The antiapoptotic activity of Bcl-2 was greatly affected by knocking-out specifically Hsp90beta using the RNA interference approach. Thus, for the first time, it has been shown that Hsp90beta might modulate the antiapoptotic activity of Bcl-2 at least in mast cells. These findings could have implications for a novel strategy of regulating apoptosis in patients with mastocytosis and other mast cell-associated diseases.