Biomedical subjects

Luis Alvarez-Vallina

Publications and source records attributed to Luis Alvarez-Vallina.

22 records · Page 2Linked to original sources

PubMed2002

Cells as vehicles for cancer gene therapy: the missing link between targeted vectors and systemic delivery?

Systemic administration of currently manufactured viral stocks has not so far achieved sufficient circulating titers to allow therapeutic targeting of metastatic disease. This is due to low initial viral titers, immune inactivation, nonspecific adhesion, and loss of particles. One way to exploit the elegant molecular manipulations that have been made to increase vector targeting is to protect these vectors until they reach the local sites of tumor growth. Various cell types home preferentially to tumors and can be loaded with the constructs required to produce targeted vectors. Here we discuss the potential of using such cell carriers to chaperone precious vectors directly to the tumors. The vectors can incorporate mechanisms to achieve tumor site-inducible expression, along with tumor cell-specific expression of the therapeutic gene and/or replicating viral genomes that would be released at the tumor. In this way, the great advances that have so far been made with the engineering of vector tropisms might be genuinely exploited and converted into clinical benefit.

Cell Transplantation↗

PubMed2002

Development of a computer-assisted high-throughput screening platform for anti-angiogenic testing.

Angiogenesis is widely accepted to play a central role in tumor growth and spreading. Therefore, anti-angiogenic agents appear as promising tools in cancer therapy, and great efforts have been devoted to their identification in recent years. Despite fast progress in this area, a quantitative and objective system for rapid anti-angiogenic testing is not currently available. In this work, we describe a new platform for the large-scale screening of agents with potential anti-angiogenic activity. This involved the miniaturization of an in vitro two-dimensional assay model of vascular morphogenesis to run in a high-density format (384- or 1536-well microplates) and the development of a specific digital image-analysis system for the automated and quantitative evaluation of biological activity. To test the efficacy and reproducibility of the platform, we used a wide variety of well-characterized angiogenesis inhibitors, including antibodies against components of the extracellular matrix, peptides, and chemicals. The system proved to be a reproducible, polyvalent, and powerful tool for massive screening of agents with potential application in cancer therapy. Ongoing developmental work, directed toward optimizing this system for use with a fully automated high-throughput screening platform, should accelerate research into the mechanisms of tumor angiogenesis and the development of drugs that target the essential tumor vasculature.

Automation↗

PubMed2002

Tumor antigen-specific induction of transcriptionally targeted retroviral vectors from chimeric immune receptor-modified T cells.

High-level systemic delivery of viral vectors to tumors has proved problematic as a result of immune neutralization, nonspecific adhesion, and clearance of circulating viral particles. Some cell types localize to tumors in response to particular biological properties associated with tumor growth. Their use to deliver viral vectors to tumors would allow precious viral stocks to be protected until they can be released at high local concentrations. Here, we describe a mechanism by which retroviral vector production by T cells can be regulated by a tumor-specific trigger through engagement of a chimeric immune receptor (CIR) with its target antigen. The virus that is released from the T cells can also be transcriptionally targeted. Finally, we show that it is possible to use vector-loaded, antigen-triggered human T cells as therapeutic, tumor-specific vector delivery cells in models of both local intratumoral and systemic delivery to both lung and liver metastases. This strategy incorporates multiple levels of targeting into the delivery system at the stages of surface targeting, viral production, and gene expression.

Adenoviridae↗

PubMed2002

Autocrine costimulation: tumor-specific CD28-mediated costimulation of T cells by in situ production of a bifunctional B7-anti-CEA diabody fusion protein.

T cells require two distinct signals for optimal activation, an antigen-specific signal, provided by engagement of the T-cell receptor (TCR) and a second costimulatory signal mediated by engagement of CD28 with members of the B7 family. Although infiltrating T cells are present in many malignancies, they appear to be mostly anergic and do not attack the tumor, presumably because of the absence of activation and/or costimulatory signals. Here we describe a novel strategy for the in situ activation of tumor-specific T cells. We genetically modified T cells to secrete a bifunctional fusion protein, comprising the extracellular portion of B7-1 fused to an anticarcinoembryonic antigen (CEA) diabody. In coculture with CEA(+) tumor cells autocrine and paracrine secretion of B7-alphaCEA provided a potent tumor-specific costimulatory signal to T cells in combination with a recombinant alphaCEAxalphaCD3 bispecific diabody. B7-alphaCEA was also found to strongly enhance survival and tumor-specific activation of T cells expressing an anti-CEA TCRzeta-based chimeric immune receptor (CIR) both when expressed in cis by the T cells themselves as well as in trans, when added to the culture medium. In the absence of costimulatory signals provided by the tumor, our strategy allows T cells to "arm themselves" by the production of tumor-specific costimulatory proteins. Sustained in situ production of such molecules, like the B7-diabody fusion protein may create a favorable local environment for the activation and proliferation of tumor-reactive T cells and increase the tumoricidal activity of immunotherapeutic approaches targeting the TCR pathway.

Autocrine Communication↗