Immuno-oncology has gained momentum with the approval of antibodies with clinical
activities in different indications. Unfortunately, for anti-PD (L)1 agents in monotherapy,
only half of the treated population achieves a clinical response. For other agents,
such as anti-CTLA4 antibodies, no biomarkers exist, and tolerability can limit administration.
In this study, using publicly available genomic datasets, we evaluated the expression
of the macrophage scavenger receptor-A (SR-A) (MSR1) and its association with a response
to check-point inhibitors (CPI). MSR1 was associated with the presence of macrophages,
dendritic cells (DCs) and neutrophils in most of the studied indications. The presence
of MSR1 was associated with macrophages with a pro-tumoral phenotype and correlated
with TIM3 expression. MSR1 predicted favorable overall survival in patients treated
with anti-PD1 (HR: 0.56, FDR: 1%, p = 2.6 x 10-5), anti PD-L1 (HR: 0.66, FDR: 20%,
p = 0.00098) and anti-CTLA4 (HR: 0.37, FDR: 1%, p = 4.8 x 10-5). When specifically
studying skin cutaneous melanoma (SKCM), we observed similar effects for anti-PD1
(HR: 0.65, FDR: 50%, p = 0.0072) and anti-CTLA4 (HR: 0.35, FDR: 1%, p = 4.1 x 10-5).
In a different dataset of SKCM patients, the expression of MSR1 predicted a clinical
response to anti-CTLA4 (AUC: 0.61, p = 2.9 x 10-2). Here, we describe the expression
of MSR1 in some solid tumors and its association with innate cells and M2 phenotype
macrophages. Of note, the presence of MSR1 predicted a response to CPI and, particularly,
anti-CTLA4 therapies in different cohorts of patients. Future studies should prospectively
explore the association of MSR1 expression and the response to anti-CTLA4 strategies
in solid tumors.
