Anti-PD-1 and anti-CTLA-4 immunotherapies have become the standard of care for metastatic melanoma. However, the majority of patients develop resistance to therapy. Macrophages are abundant cells in tumours, but their role in immunotherapy response and resistance is largely unknown. This study investigated the role of macrophages in anti-PD-1 +/- CTLA-4 response in stage IV melanoma patients.
Transcriptomic and multiplex immunohistochemistry (mIHC) immune profiling were performed on formalin-fixed paraffin embedded tissue pre-treatment biopsies from advanced melanoma patients treated with anti-PD-1 (n = 19) or anti-PD-1 + anti-CTLA-4 (n = 10). Response and progression-free survival were assessed using RECIST criteria. Using tumour dissociates, mass cytometry was used to characterize macrophages in detail.
Although there was no significant difference in CD68+ macrophages between responding and non-responding patients, responding patients had a significantly higher intratumoral density of CD14+ CD68+ CD16+ macrophages compared to non-responders at baseline (median= 192 versus 23; p = 0.006). Using mIHC, patients were classified into high/low CD16+ macrophages and differential RNA expression analysis was performed. CD16+ high macrophage tumours displayed increased expression of genes related to T cell activation (TIGIT, LAG3, ICOS, PDCD1, FASLG and TBX21), MHC class I presentation (TAP1, UBD, PSMB10 and B2M) and chemokine + cytokine activity (CXCL13, CXCL10, CXCL11, CXCL9, CXCR6 and CXCR3). Using mass cytometry, we determined that CD16+ macrophages are CD13+ HLA-DR+, ICOS+ CD86+/- LAG3- GITR- TIGIT-. Multivariate analysis showed that low LDH, low melanoma substage and the presence of high CD16+ macrophages were associated with a significantly better overall response rate (OR = 14; p = 0.011) and progression free survival (HR = 0.15; p = 0.016), but not overall survival (HR = 0.22; p = 0.068).
Presence of CD68+ CD14+ CD16+ macrophages in pre-treatment melanoma combined with low LDH and low melanoma substage strongly correlates with response and survival of advanced melanoma patients treated with immunotherapy.
Clinical trial identification
Legal entity responsible for the study
National Health and Medical Research Council (NHMRC).
M.S. Carlino: Advisory / Consultancy: Amgen; Advisory / Consultancy: Merck MSD; Advisory / Consultancy: Novartis; Advisory / Consultancy: Pierre Fabre. A.M. Menzies: Advisory / Consultancy: BMS; Advisory / Consultancy: Merck MSD; Advisory / Consultancy: Novartis; Advisory / Consultancy: Roche; Advisory / Consultancy: Pierre Fabre. G.V. Long: Advisory / Consultancy: Amgen; Advisory / Consultancy: Array; Advisory / Consultancy: BMS; Advisory / Consultancy: Merck MSD; Advisory / Consultancy: Novartis; Advisory / Consultancy: Roche; Advisory / Consultancy: Pierre Fabre. All other authors have declared no conflicts of interest.