Monoclonal antibodies targeting immune checkpoints are gaining ground in the treatment of melanoma and other cancers, and considerable effort is made to identify biomarkers predicting the efficacy of these therapies. Our retrospective study was performed on surgical tissue samples (52 lymph nodes and 34 cutaneous/subcutaneous metastases) from 30 patients with metastatic melanoma treated with ipilimumab. Using a panel of 11 antibodies against different immune cell types, intratumoral immune cell densities were determined and evaluated in relation to response to ipilimumab treatment and disease outcome. For most markers studied, median immune cell densities were at least two times higher in lymph node metastases compared to skin/subcutaneous ones; therefore, the prognostic and predictive associations of immune cell infiltration were evaluated separately in the two groups of metastases as well as in all samples as a whole. Higher prevalence of several immune cell types was seen in lymph node metastases of the responders compared to non-responders, particularly FOXP3 cells and CD8 T lymphocytes. In subcutaneous or cutaneous metastases, on the other hand, significant difference could be observed only in the case of CD16 and CD68. Associations of labeled cell densities with survival were also found for most cell types studied in nodal metastases, and for CD16 and CD68 cells in skin/s.c. metastatic cases. Our results corroborate the previous findings suggesting an association between an immunologically active tumor microenvironment and response to ipilimumab treatment, and propose new potential biomarkers for predicting treatment efficacy and disease outcome.

BackgroundBesides being a preferential site of early metastasis, the sentinel lymph node (SLN) is also a privileged site of T-cell priming, and may thus be an appropriate target for investigating cell types involved in antitumor immune reactions.MethodsIn this retrospective study we determined the prevalence of OX40+ activated T lymphocytes, FOXP3+ (forkhead box P3) regulatory T cells, DC-LAMP+ (dendritic cell-lysosomal associated membrane protein) mature dendritic cells (DCs) and CD123+ plasmacytoid DCs by immunohistochemistry in 100 SLNs from 60 melanoma patients. Density values of each cell type in SLNs were compared to those in non-sentinel nodes obtained from block dissections (n = 37), and analyzed with regard to associations with clinicopathological parameters and disease outcome.ResultsSentinel nodes showed elevated amount of all cell types studied in comparison to non-sentinel nodes. Metastatic SLNs had higher density of OX40+ lymphocytes compared to tumor-negative nodes, while no significant difference was observed in the case of the other cell types studied. In patients with positive sentinel node status, high amount of FOXP3+ cells in SLNs was associated with shorter progression-free (P = 0.0011) and overall survival (P = 0.0014), while no significant correlation was found in the case of sentinel-negative patients. The density of OX40+, CD123+ or DC-LAMP+ cells did not show significant association with the outcome of the disease.ConclusionsTaken together, our results are compatible with the hypothesis of functional competence of sentinel lymph nodes based on the prevalence of the studied immune cells. The density of FOXP3+ lymphocytes showed association with progression and survival in patients with positive SLN status, while the other immune markers studied did not prove of prognostic importance. These results, together with our previous findings on the prognostic value of activated T cells and mature DCs infiltrating primary melanomas, suggest that immune activation-associated markers in the primary tumor may have a higher impact than those in SLNs on the prognosis of the patients. On the other hand, FOXP3+ cell density in SLNs, but not in the primary tumor, was found predictive of disease outcome in melanoma patients.

Ectopic lymphoid structures have been described in several tumor types including metastatic lesions, but not primary tumors, of patients with melanoma. Here we present evidence of B-cell follicles in primary cutaneous melanomas, being present in 39 of 147 cases (27 %). B-cell clusters were associated with T lymphocytes, most of which belonging to CD45RO(+) memory T cells. A network of CD21(+) follicular dendritic cells was demonstrated in 8 of 22 cases studied (36 %). MECA-79(+) HEV-like venules were observed in the neighborhood of the follicles in the majority of cases, however, their presence was not confined to tumors hosting ectopic lymphoid structures. The appearance of B-cell aggregates did not show association with the outcome of the disease, although a trend for their higher prevalence was observed in thicker tumors. Our results show that neogenesis of lymphoid structures does occur in primary melanomas, albeit with lower frequency compared to that reported in metastases.

High endothelial venules (HEVs) are specialized vessels in lymphoid organs, supporting lymphocyte trafficking from the blood. As the presence of these vessels was described recently in tumors, it was proposed that they could facilitate the development of antitumor immune response, resulting in improved prognosis. The aim of our study was to analyze the correlation of the density of HEVs with that of the different immune cell types as well as with the clinicopathologic parameters and the disease outcomes in patients with cutaneous melanoma. Primary melanoma samples of 118 patients were analyzed retrospectively by immunohistochemical labeling and quantitation of vessels stained with the MECA-79 antibody, as well as a panel of eight different immune cell types (CD8 and CD45RO T cells, lymphocytes expressing the CD25, CD134, or CD137 activation markers, FOXP3 regulatory T cells, CD20 B cells, and DC-LAMP mature dendritic cells). Correlations of MECA-79 vessel density with that of the immune cells, as well as with clinicopathologic parameters and disease outcomes were evaluated. We showed that the number of MECA-79 vessels correlates strongly with the peritumoral density of B and T lymphocytes. Moreover, higher HEV numbers were detected in tumors hosting tertiary lymphoid structures as well as in those of axial location compared with the ones in the extremity and in men compared with women, whereas no association was found with patient age, tumor thickness, histologic type or ulceration, or with the survival of melanoma patients. The density of MECA-79 HEVs in primary melanomas shows a correlation with B and T-lymphocyte density and differences according to the presence of tertiary lymphoid structures, tumor site, and the sex of the patient. However, it has no prognostic value.

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