Paradoxical effects of cytokines in tumor immune surveillance and tumor immune escape

Abstract
The role of cytokines in modulating the formation of new tumors is mediated by their ability to regulate antigen-specific anti-tumor responses and by the activation of non-specific mechanisms, including those involved in the processes of inflammation and innate resistance.

Cytokines may influence the growth of tumors by acting directly on tumor cells as growth promoting or growth inhibiting factors or indirectly by attracting inflammatory cell types and affecting angiogenesis. Due to the potency and complexity of cytokine activity against tumor growth, the improvement of cloning techniques and the availability of recombinant forms of different cytokines, a great effort has been made in the recent years to exploit this anti-tumor potential for cancer therapy. This important goal has been difficult to achieve in most cases due to toxicity of most cytokines which could not be dissociated from their anti-tumoral functions. Nevertheless, if well designed, treatment protocols and/or modifications of the cytokine molecules may in some situations augment the anti-tumor effects while limiting the toxicity.
One of these molecular approaches could be the design of peptides containing the functional domain of certain cytokines, exemplified by IT9302, a peptide homologous to the functional domain of IL-10, which has demonstrated to increase tumor NK cell sensitivity.

METHODS. Two novel monoclonal antibodies (MP1.1C11 and MP1.1B7) were used to examine the expression of MC1R in
uveal melanomas. Tissue samples obtained from 17 patients were analyzed for expression of MC1R by immunohistochem-istry. Additionally, uveal melanoma cell lines were treated with proinflammatory cytokines, after which MC1R cell surface ex-pression was analyzed by flow cytometry.

RESULTS. Results demonstrated that MC1R is expressed by uveal melanoma to a significantly greater extent than other mela-noma markers. With the use of MP1.1C11 or MP1.1B7, MC1R was detected in 95% of the tested melanoma tissues, including one liver metastasis. In contrast, MART-1, S100-specific pro-tein, and gp-100 were only expressed by 66%, 33%, and 67% of the analyzed samples, respectively. Results also demonstrated that even though MC1R is mainly located intracellularly, its cell surface expression can be promoted by cytokines such as IFN-
, TNF-, IL-4, and IL-10.

CONCLUSIONS. These observations support the inclusion of MC1R in the panel of markers for the diagnosis of uveal mel-anoma. Therapeutic use of MC1R-specific antibodies targeting cytokine-induced MC1R potentially requires expression of the target molecule on the surfaces of tumor cells. Data presented here support MC1R as a new marker and a putative therapeutic target for uveal melanoma. (Invest Ophthalmol Vis Sci. 2007; 48:1219–1227) DOI:10.1167/iovs.06-0090

Dendritic cell immunizations alone or combined with low doses of interleukin-2 induce specific immune responses in melanoma patients

Summary
Dendritic cell (DC)-based therapy has proved to be effective in patients with a variety of malignancies. However, an optimal immunization protocol using DCs and the best means for delivering antigens has not yet been described. In this study, 20 patients with malignant melanoma in stages III or IV were vaccinated with autologous DCs pulsed with a melanoma cell lysate, alone (n=13) or in combination with low doses of subcutaneous (s.c.) interleukin (IL)-2 injections (n= 7), to assess toxicity, immunological and clinical responses. Monocyte-derived DCs were morphological, phenotypic and functionally characterized in vitro. Peripheral blood mononuclear cells (PBMC), harvested from patients either prior to and after the treatment, were analysed using enzyme-linked immunosorbent spot (ELISPOT). After vaccination, 50% of the patients tested (seven of 13) from the rst group and (three of seven) from the second, showed an increase in interferon (IFN)-? production in response to allogeneic melanoma cell lines but not to controls. Four of ve tested human leucocyte antigen (HLA)-A2+ patients with anti-melanoma activity also showed speci c T cell responses against peptides derived from melanoma-associated antigens. Delayed type IV hypersensitivity reaction (DTH) against melanoma cell lysate was observed in six of 13 patients from the group treated with DC vaccines only and four of seven from the group treated with the combination of DCs and IL-2. Signi cant correlations were found between DTH-positive responses against tumour lysate and both disease stability and post-vaccination survival on the stage IV patients. There were no toxicities associated with the vaccines or evidence of autoimmunity including vitiligo. Furthermore, no signi cant enhancement was observed as a result of combining DC vaccination with IL-2. Our data suggest that autologous DCs pulsed with tumour lysate may provide a standardized and widely applicable source of melanoma speci c antigens for clinical use. It is safe and causes no signi cant side effects and has been demonstrated to be partially ef cient at triggering effective anti-melanoma immunity.

The role of regulatory T lymphocytes in the induced immune response mediated by biological vaccines

Abstract
Immunotherapy has become a novel therapeutic alternative for various kinds of tumours.Recently,we have ?nalized the ?rst phase I clinical study in Chile for the treatment of advanced malignant melanoma,using dendritic cells (DCs)loaded with allogeneic melanoma cell lysate. This study included 20 patients and the obtained results,pioneer in Latin America,showed that DC-based immunotherapy is innocuous,even provided in combination with IL-2.In addition,immunological responses were detected in 50% of the treated patients,establishing a positive correlation between the delayed type hypersensitivity (DTH)reaction,which indicates induction of in vivo immunological memory,and patients surviving. (...)