CD4+ T cell responses to HLA-DP5-restricted wild-type sequence p53 peptides in patients with head and neck cancer

T-helper and T-regulatory cells modulation in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is one of the most diffused cancer types, characterized by a high reoccurrence rate, mainly due to the inability of current therapeutic approaches to completely eradicate cancer cells. HNSCC patients often have defective immune functions, thus allowing cancer immune escape and cancer spreading. Particularly important in driving immune escape during HNSCC progression are T-helper and T-regulatory cells. New insights into their mechanisms of action might support the development of effective and long-lasting immunotherapy.

Immune alterations and immunotherapy prospects in head and neck cancer

INTRODUCTION

Several literature sources have suggested that subjects with head and neck squamous cell carcinoma (HNSCC) display significant abnormalities of immunocompetent cells and cytokine secretion. Serious side effects and only a limited success with traditional therapies in HNSCC dictate the need for newer therapies.

AREAS COVERED

This article comprehensively reviews the immune system alterations in HNSCC and the rationale behind various experimental immunotherapies, aiming at keeping this disease under control. Relevant publications were identified through the PubMed database search. The ongoing clinical trials regarding experimental immunotherapy agents in HNSCC were accessed at www.clinicaltrials.gov . The obtained information was thoroughly analyzed and systematized.

EXPERT OPINION

Important and severe immune defects including T-cell dysfunction, cytokine alterations and antigen presentation defects are present in patients with HNSCC. In addition, tumor microenvironment was shown to play a critical role in the HNSCC progression. These discoveries have triggered a growing interest in immunotherapy as a potential treatment strategy for HNSCC. Effective immunotherapy could avoid the toxic side effects plaguing the current management of HNSCC. It is also hoped that immunotherapy will have long-lasting effects due to induction of immunologic memory. Promising directions include nonspecific immune stimulation, targeting specific HNSCC tumor antigens and therapeutic vaccines among others. These new agents may expand the existing therapy options for HNSCC in future.

Intratumoral convergence of the TCR repertoires of effector and Foxp3+ CD4+ T cells

The presence of Foxp3⁺ regulatory CD4⁺ T cells in tumor lesions is considered one of the major causes of ineffective immune response in cancer. It is not clear whether intratumoral T_reg cells represent T_reg cells pre-existing in healthy mice, or arise from tumor-specific effector CD4⁺ T cells and thus representing adaptive T_reg cells. The generation of T_reg population in tumors could be further complicated by recent evidence showing that both in humans and mice the peripheral population of T_reg cells is heterogenous and consists of subsets which may differentially respond to tumor-derived antigens. We have studied T_reg cells in cancer in experimental mice that express naturally selected, polyclonal repertoire of CD4⁺ T cells and which preserve the heterogeneity of the T_reg population. The majority of T_reg cells present in healthy mice maintained a stable suppressor phenotype, expressed high level of Foxp3 and an exclusive set of TCRs not used by naive CD4⁺ T cells. A small T_reg subset, utilized TCRs shared with effector T cells and expressed a lower level of Foxp3. We show that response to tumor-derived antigens induced efficient clonal recruitment and expansion of antigen-specific effector and T_reg cells. However, the population of T_reg cells in tumors was dominated by cells expressing TCRs shared with effector CD4⁺ T cells. In contrast, T_reg cells expressing an exclusive set of TCRs, that dominate in healthy mice, accounted for only a small fraction of all T_reg cells in tumor lesions. Our results suggest that the T_reg repertoire in tumors is generated by conversion of effector CD4⁺ T cells or expansion of a minor subset of T_reg cells. In conclusion, successful cancer immunotherapy may depend on the ability to block upregulation of Foxp3 in effector CD4⁺ T cells and/or selectively inhibiting the expansion of a minor T_reg subset.

Tumor vaccines in 2010: need for integration

Induction of tumor-specific immunity is an attractive approach to cancer therapy, however to date every major pivotal trial has resulted in failure. While the phenomena of tumor-mediated immune suppression has been known for decades, only recently have specific molecular pathways been elucidated, and for the first time, rationale means of intervening and observing results of intervention have been developed. In this review we describe major advances in our understanding of tumor escape from immunological pressure and provide some possible therapeutic scenarios for enhancement of efficacy in future cancer vaccine trials.