Abstract 2798: High density of CD68+HLA-DR- macrophages in the stroma of primary melanoma correlates with an unfavorable immune microenvironment as assessed by Digital Spatial Profiling

• Published in: Cancer research (Chicago, Ill.) Ill.), 2019-07, Vol.79 (13_Supplement), p.2798-2798
• Main Authors: Rizk, Emanuelle M., Chen, Andrew, Silverman, Andrew M., Marks, Douglas K., Rabadan, Raul, Fuhrman, Kit, VanSchoiack, Alison, Liang, Yan, Beechem, Joseph, Saenger, Yvonne M., Gartrell, Robyn D.
• Format: Article
• Language: English
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/1538-7445.AM2019-2798

Introduction: The role of macrophages (Mϕ) in melanoma progression is controversial, as they have been shown to both favor and inhibit anti-tumor immunity. Density of Mϕ at the leading tumor edge has been shown to be a marker of poor prognosis. In previous work, we used quantitative multiplexed immunofluorescence (qmIF) to discover the ratio of CD8+ T lymphocytes (CTLs) to CD68+ Mϕ in the peritumoral stroma predicts a favorable prognosis. Further, we found that increased proximity of HLA-DR- Mϕ to CTLs in the stroma predicts poor prognosis. These findings highlight the importance of the location of Mϕ within the tumor microenvironment (TME). Here, we further analyze and compare the TME of patients with high and low stromal densities of HLA-DR- Mϕ. Methods: From a cohort of 104 patients with primary stage II-III melanoma and known survival information, we selected 8 patients for Digital Spatial Profiling (DSP) analyses. Of this subcohort, 4 patients had a high density of HLA-DR- Mϕ and close proximity of HLA-DR- Mϕ to CTLs in the stroma while the other 4 had a high CTL to Mϕ ratio with low HLA-DR- Mϕ density, as determined by qmIF (methods published). FFPE slides were stained with antibodies conjugated to UV-photocleavable DNA barcodes and specific to 34 proteins, including CD45, CD4, CD8, CD68, PD-1, and PD-L1. Twelve regions of interest (ROIs) per patient were selected based on high Mϕ density as determined by qmIF. ROIs were then analyzed using UV excitation, which releases DNA barcodes for downstream quantitation on the nanoString nCounter® platform. Protein expression was compared between patients and statistical analysis performed using Mann-Whitney test. Results: We found that ROIs from patients with higher density of HLA-DR- Mϕ had a lower immune infiltration overall as assessed by quantitation of CD45 per ROI (p