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Myeloid-Derived Suppressor Cells (MDSC) in Melanoma Patients Treated with Anti-PD-1 Immunotherapy
Myeloid-derived suppressor cells (MDSC) are a subset of immature myeloid cells with suppressive activity well described in the context of cancer. They inhibit anti-tumour immunity, promote metastasis formation and can lead to immune therapy resistance. In a retrospective study, blood probes of 46 advanced melanoma patients were analysed before the first administration of anti-PD-1 immunotherapy and in the third month of treatment for MDSC, immature monocytic (ImMC), monocytic MDSC (MoMDSC) and granulocytic MDSC (GrMDSC) by multi-channel flow cytometry. Cell frequencies were correlated with response to immunotherapy, progression-free survival (PFS) and lactate dehydrogenase (LDH) serum level. Responders to anti-PD-1 therapy had higher MoMDSC levels (4.1 ± 1.2%) compared to non-responders (3.0 ± 1.2%) (p = 0.0333) before the first administration of anti-PD-1. No significant changes in MDSCs frequencies were observed in the groups of patients before and in the third month of therapy. The cut-off values of MDSCs, MoMDSCs, GrMDSCs and ImMCs for favourable 2- and 3-year PFS were established. Elevated LDH level is a negative prognostic factor of response to the treatment and is related to an elevated ratio of GrMDSCs and ImMCs level compared to patients’ LDH level below the cut-off. Our data may provide a new perspective for more careful consideration of MDSCs, and specially MoMDSCs, as a tool for monitoring the immune status of melanoma patients. Changes in MDSC levels may have a potential prognostic value, however a correlation with other parameters must be established.
Exploring correlations between gut mycobiome and lymphocytes in melanoma patients undergoing anti-PD-1 therapy
Abstract Research has shown that the microbiome can influence how the immune system responds to melanoma cells, affecting the course of the disease and the outcome of the therapy. Here, we used the metagenomic approach and flow cytometry analyses of blood cells to discover correlations between gut fungi of metastatic melanoma patients enrolled in anti-PD-1 therapy and lymphocytes in their blood. We analyzed the patterns of associations before the first administration of anti-PD-1 therapy (BT, n = 61) and in the third month of the therapy (T3, n = 37), allowing us to track changes during treatment. To understand the possible impact of gut fungi on the efficacy of anti-PD-1 therapy, we analyzed the associations in clinical beneficiaries (CB, n = 37) and non-beneficiaries (NB, n = 24), as well as responders (R, n = 28) and non-responders (NR, n = 33). Patients with LDH < 338 units/L, overall survival (OS) > 12, CB, as well as R, had lower levels of Shannon diversity (p = 0.02, p = 0.05, p = 0.05, and p = 0.03, respectively). We found that the correlation pattern between intestinal fungi and lymphocytes was specific to the type of response, positive or negative. When comparing CB and NB groups, correlations with opposite directions were detected for C. albicans, suggesting a response-specific immune reaction. For CB, M. restricta exhibited a set of correlations with different types of lymphocytes, with prevalent positive correlations, suggesting a robust immune response in the CB group. This result extends our former research, where M. restricta and C. albicans were associated with an increased risk of melanoma progression and a poorer response to anti-PD-1 treatment.