Induced and natural regulatory T cells in human cancer.
ABSTRACT Introduction: Evidence suggests that FOXP3(+)CD25(high)CD4(+) regulatory T cells (Treg) which accumulate in cancer may have beneficial or unfavorable effects on prognosis. The presence in tumor-associated inflammatory infiltrates of two subsets of Treg with distinct phenotypic and functional profiles might explain these conflicting observations. Areas covered: Human inducible (i) Treg arising by tumor-driven conversion of conventional CD4(+) T cells are highly suppressive, therapy-resistant Treg which down-regulate anti-tumor immune responses, promoting tumor growth. Natural (n) Treg, normally responsible for maintaining peripheral tolerance, control cancer-associated inflammation, which favors tumor progression. This division of labor between nTreg and iTreg is not absolute, and overlap may be common. Nevertheless, iTreg play a critical and major role in cancer and cancer therapy. The tumor microenvironment determines the type, frequency and suppression levels of accumulating Treg. Expert opinion: In cancer, a selective removal or silencing of iTreg and not of nTreg should be a therapeutic goal. However, the implementation of this challenging strategy requires further studies of cellular and molecular crosstalk among immune cells in the tumor microenvironment.
SourceAvailable from: Syed Salman Ashraf
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ABSTRACT: Meta-analyses show that approximately half of all squamous cell carcinomas (SCCs) of the penis are associated with a human papillomavirus (HPV) infection. As data about the tumour microenvironment of HPV-positive and HPV-negative penile carcinomas is scarce and conflicting, we examined tumour-infiltrating lymphocyte populations in such cases. The HPV status of 28 penile SCCs was determined by polymerase chain reaction, while the number and distribution of different lymphocyte populations were analysed by immunohistochemistry on whole sections of paraffin-embedded tumour specimens. The average number of tumour-infiltrating T cells in HPV-associated SCC was higher than in HPV-negative SCC, and their phenotype showed strong polarization towards a T helper 1 and cytotoxic immune response. In addition, we identified more tumour-infiltrating regulatory T cells in HPV-positive carcinomas, which might represent a mechanism of immune evasion. The present study provides further evidence that the tumour microenvironment of HPV-positive carcinomas differs from that of HPV-negative carcinomas.Archiv für Pathologische Anatomie und Physiologie und für Klinische Medicin 12/2014; 466(3). DOI:10.1007/s00428-014-1713-4 · 2.56 Impact Factor
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ABSTRACT: Cancer immune evasion is a major stumbling block in designing effective anticancer therapeutic strategies. Although considerable progress has been made in understanding how cancers evade destructive immunity, measures to counteract tumor escape have not kept pace. There are a number of factors that contribute to tumor persistence despite having a normal host immune system. Immune editing is one of the key aspects why tumors evade surveillance causing the tumors to lie dormant in patients for years through "equilibrium" and "senescence" before re- emerging. In addition, tumors exploit several immunological processes such as targeting the regulatory T cell function or their secretions, antigen presentation, modifying the production of immune suppressive mediators, tolerance and immune deviation. Besides these, tumor heterogeneity and metastasis also play a critical role in tumor growth. A number of potential targets like promoting Th1, NK cell, γδ T cell responses, inhibiting Treg functionality, induction of IL-12, use of drugs including phytochemicals have been designed to counter tumor progression with much success. Some natural agents and phytochemicals merit further study. For example, use of certain key polysaccharide components from mushrooms and plants have shown possess therapeutic impact on tumor-imposed genetic instability, anti-growth signaling, replicative immortality, deregulated metabolism etc. In this review, we will discuss the advances made towards understanding the basis of cancer immune evasion and summarize the efficacy of various therapeutic measures and targets that have been developed or are being investigated to enhance tumor rejection. Copyright © 2015. Published by Elsevier Ltd.Seminars in Cancer Biology 03/2015; ePub ahead of print. DOI:10.1016/j.semcancer.2015.03.004 · 9.14 Impact Factor