Aim
This study aimed to determine the expression and significance of LOX-1 in the TME of clinical CRC specimens.
Background
Lectin-like oxidized LDL receptor-1 (LOX-1) has been identified as a new marker for functional myeloid-derived suppressor cells (MDSCs) that exhibit an immunosuppressive phenotype in the tumor microenvironment (TME). However, the role of LOX-1+ cells in the TME of colorectal cancer (CRC) remains unknown.
Conclusions
The MDSC marker, LOX-1, was mainly expressed by M2 macrophages in CRC tissues. LOX-1+ macrophages and CD8+ CTLs may serve as useful biomarkers for predicting the prognosis of CRC.
Results
We performed immunohistochemical and genetic analyses of LOX-1, CD8, KRAS, and BRAF in 128 resected CRC specimens and determined the expression of IFN-γ and IL-10 using real-time reverse transcription-polymerase chain reaction. We analyzed the correlation between LOX-1, TME factors, gene alteration, clinicopathological factors, and disease prognosis. The co-expression pattern of LOX-1, hematopoietic markers, and a fibroblast marker was evaluated using multiplex immunofluorescence staining. Low stromal LOX-1 expression and low intratumoral CD8+ cytotoxic T-lymphocyte (CTL) status correlated with poor prognosis. Moreover, stromal LOX-1-low/CD8+ CTL-low status was the most important independent prognostic factor of poor overall survival. Most of the LOX-1+ stromal cells were positive for CD163+ , indicating they were CD163+ M2 macrophages. Conclusions: The MDSC marker, LOX-1, was mainly expressed by M2 macrophages in CRC tissues. LOX-1+ macrophages and CD8+ CTLs may serve as useful biomarkers for predicting the prognosis of CRC.