Avid Bioservices Inc (CDMO)

[jazzbeerman]

TGF-beta, T regs, Bavituximab........

As you know, Bavituximab therapy is proven to shift the cytokine environment away from TGF-beta.


first this: It's recent...


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Tregs and rethinking cancer immunotherapy

http://www.jci.org/cgi/content/abstract/117/5/1167

Tyler J. Curiel

San Antonio Cancer Institute, University of Texas Health Sciences Center, and Cancer Therapy & Research Center, San Antonio, Texas, USA.

Address correspondence to: Tyler J. Curiel, San Antonio Cancer Institute, University of Texas Health Sciences Center

Tumors express antigens that should induce immune-mediated rejection, but spontaneous rejection of established tumors is rare. Recent work demonstrates that one reason for the lack of tumor rejection is that tumors actively defeat host immunity. This concept forces us to rethink current approaches to harnessing potent, specific host immunity to battle cancer, most of which are based on the paradigm that inducing more antitumor immune cells alone is therapeutic. However, as I discuss in this Personal Perspective, a newer paradigm predicts that reducing tumor-driven immune suppression will be clinically beneficial. CD4+CD25+ Tregs are one mechanism of tumor-driven immune evasion that provide prototypical targets for testing novel anticancer treatment strategies within the newer paradigm.



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Then this Must-Read "reply", on October 10th, 2007 ...................


excerpts below -


Journal of Clinical Oncology, Vol 25, No 29 (October 10), 2007

CORRESPONDENCE

In Reply

http://jco.ascopubs.org/cgi/content/full/25/29/4696

Paola Filipazzi, Chiara Castelli, Valenti Roberta, Veronica Huber, Manuela Iero, Lorenzo Pilla, Licia Rivoltini

Unit of Immunotherapy of Human Tumors, Fondazione IRCCS Istituto Nazionale Tumori, Milan, Italy

Giorgio Parmiani

Unit of Immunobiotherapy of Solid Tumors S. Raffaele Scientific Institute, Milan, Italy




A growing body of evidence currently supports the role of myeloid suppressor cells (MSC) as key mediators of immunosuppression in tumor-bearing animals.1 Nevertheless, the analysis of the actual relevance of this mechanism in cancer patients has so far been penalized by the variability of phenotypic and functional hallmarks that these cells appear to display in a human setting. In our study, we identify a monocyte subset (CD14+ human leukocyte antigen-DR [HLA-DR]–/lo transforming growth factor-ß [TGF-ß]–secreting cells) that may indeed represent an MSC population in patients with advanced melanoma. The finding acquires more relevance considering that melanoma is one of the human tumor histotypes mostly involved in immunotherapy studies because of its unique immunogenic properties.2 Having defined features for the identification of MSC in patients with melanoma should allow us in the near future to understand the relevance that this cell subset plays in restraining antitumor immune responses.

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As correctly pointed out by Ferretti, TGF-ß is a pathway shared by different regulatory immune mechanisms. Indeed, regulatory T cells (Treg) exert their immunosuppressive activity through mechanisms including cell-cell contact and/or the production of soluble factors such as interleukin-10 or TGF-ß,3 as we are presently observing in advanced melanoma patients (Castelli et al, unpublished observation, 2007). Recent studies in experimental models have linked MSC to Treg, showing that the conversion by tumor cells of dendritic cells into MSC induces bioactive TGF-ß secretion, which in turn stimulates Treg expansion and subsequent suppression of T cell–mediated immune responses.4

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from our study as well as from several other works,7,8 TGF-ß is emerging as a cytokine playing a pivotal role in immunosuppression of cancer patients. Indeed, both MSC and Treg seem to use this pathway to shut down antitumor T cell responses; therefore, interfering with the activity of this cytokine could represent a key strategy to cancer therapy.

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New molecules such as antisense oligonucleotides for TGF-ß, small drug-molecules that inhibit TGF-ß receptor I kinase, and anti–TGF-ß antibodies have shown promising results in preclinical studies and are presently entering the clinical phase of evaluation.9

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Alternatively, the interference with immunosuppressive mechanisms could be attempted upstream, interfering with the pathway utilized by tumor cells to promote MSC in vivo generation. As we reported that exosomes released by melanoma cells are likely responsible for the induction of CD14+HLA-DR–/lo cells secreting TGF-ß, thwarting the process of exosome production could represent a tool for interrupting the immunosuppressive circuits established by tumor cells and for retrieval of cancer immunity.


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