AUTHOR=Bravo Alicia Inés , Aris Mariana , Panouillot Marylou , Porto Martina , Dieu-Nosjean Marie-Caroline , Teillaud Jean-Luc , Barrio María Marcela , Mordoh José 

TITLE=HEV-associated dendritic cells are observed in metastatic tumor-draining lymph nodes of cutaneous melanoma patients with longer distant metastasis-free survival after adjuvant immunotherapy

JOURNAL=Frontiers in Immunology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2023.1231734

DOI=10.3389/fimmu.2023.1231734

ISSN=1664-3224

ABSTRACT=<sec><title>Introduction</title><p>Tissue biomarkers that aid in identifying cutaneous melanoma (CM) patients who will benefit from adjuvant immunotherapy are of crucial interest. Metastatic tumor-draining lymph nodes (mTDLN) are the first encounter site between the metastatic CM cells and an organized immune structure. Therefore, their study may reveal mechanisms that could influence patients´ outcomes.</p></sec><sec><title>Methods</title><p>Twenty-nine stage-III CM patients enrolled in clinical trials to study the vaccine VACCIMEL were included in this retrospective study. After radical mTDLN dissection, patients were treated with VACCIMEL (n=22) or IFNα-2b (n=6), unless rapid progression (n=1). Distant Metastasis-Free Survival (DMFS) was selected as an end-point. Two cohorts of patients were selected: one with a good outcome (GO) (n=17; median DMFS 130.0 months), and another with a bad outcome (BO) (n=12; median DMFS 8.5 months). We analyzed by immunohistochemistry and immunofluorescence the expression of relevant biomarkers to tumor-cell biology and immune cells and structures in mTDLN, both in the tumor and peritumoral areas.</p></sec><sec><title>Results</title><p>In BO patients, highly replicating Ki-67<sup>+</sup> tumor cells, low tumor HLA-I expression and abundant FoxP3<sup>+</sup> lymphocytes were found (<italic>p=0.037; p=0.056</italic> and <italic>p=0.021</italic>). In GO patients, the most favorable biomarkers for prolonged DMFS were the abundance of peri- and intra-tumoral CD11c<sup>+</sup> cells (<italic>p=0.0002</italic> and <italic>p=0.001</italic>), peri-tumoral DC-LAMP<sup>+</sup> dendritic cells (DCs) (<italic>p=0.001</italic>), and PNAd<sup>+</sup> High Endothelial Venules (HEVs) (<italic>p=0.004</italic>). Most strikingly, we describe in GO patients a peculiar, heterogeneous structure that we named FAPS (Favoring Antigen-Presenting Structure), a triad composed of DC, HEV and CD62L<sup>+</sup> naïve lymphocytes, whose postulated role would be to favor tumor antigen (Ag) priming of incoming naïve lymphocytes. We also found in GO patients a preferential tumor infiltration of CD8<sup>+</sup> and CD20<sup>+</sup> lymphocytes (<italic>p=0.004</italic> and <italic>p=0.027</italic>), as well as peritumoral CD20<sup>+</sup> aggregates, with no CD21<sup>+</sup> follicular dendritic cells detected (<italic>p=0.023</italic>). Heterogeneous infiltration with CD64<sup>+</sup>CD68<sup>-</sup>CD163<sup>-</sup>, CD64<sup>+</sup>CD68<sup>+</sup>CD163<sup>-</sup> and CD64<sup>+</sup>CD68<sup>+</sup>CD163<sup>+</sup> macrophages were observed in both cohorts.</p></sec><sec><title>Discussion</title><p>The analysis of mTDLN in GO and BO patients revealed marked differences. This work highlights the importance of analyzing resected mTDLN from CM patients and suggests a correlation between tumor and immune characteristics that may be associated with a spontaneous or vaccine-induced long DMFS. These results should be confirmed in prospective studies.</p></sec>