AUTHOR=Chen Qiong-Yuan , Chen Yu-Xin , Han Qiu-Yue , Zhang Jiang-Gang , Zhou Wen-Jun , Zhang Xia , Ye Yao-Han , Yan Wei-Hua , Lin Aifen 

TITLE=Prognostic Significance of Immune Checkpoints HLA-G/ILT-2/4 and PD-L1 in Colorectal Cancer

JOURNAL=Frontiers in Immunology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2021.679090

DOI=10.3389/fimmu.2021.679090

ISSN=1664-3224

ABSTRACT=<p>Immune checkpoint inhibitors (ICIs) have become a promising area of research for cancer treatment. In addition to the well-known ICIs targeting PD-1/PD-L1, HLA-G/ILT-2/-4 is relatively new immune checkpoint that has been evaluated in early clinical trials in patients with advanced solid tumors. In this study, the expression of HLA-G (n=157), ILT-2/4 (n=82), and PD-L1 (n=70) in epithelial cell adhesion molecule (EpCAM)-positive colorectal cancer (CRC) cells was analyzed by multicolor flow cytometry, and the prognostic significance of these molecules was evaluated. In EpCAM<sup>+</sup> CRC cells, the median percentages of HLA-G, ILT-2, ILT-4, and PD-L1 were 14.90%, 67.70%, 8.55% and 80.30%, respectively. In addition, a positive correlation was observed between them (all <italic>p</italic>&lt;0.001). Higher levels of these immune checkpoint proteins are associated with lymph node metastasis. In addition to the AJCC stage (<italic>p</italic>=0.001), Kaplan-Meier survival analysis showed that higher levels of HLA-G (<italic>p</italic>=0.041), ILT-2 (<italic>p</italic>=0.060), ILT-4 (<italic>p</italic>&lt;0.001), PD-L1 (<italic>p</italic>=0.012), HLA-GILT4 (<italic>p</italic>&lt;0.001) and ILT-2ILT-4 (<italic>p</italic>&lt;0.001) were significantly associated with shorter survival of CRC patients. When CRC patients were stratified by early and advanced AJCC stages, HLA-G levels were only related to the survival among CRC patients with early disease stage (<italic>p</italic>=0.024), while ILT-4 levels were significant for both CRC patients with early (<italic>p</italic>=0.001) and advanced (<italic>p</italic>=0.020) disease stages. Multivariate cox regression analysis revealed that advanced AJCC stage (HR=2.435; <italic>p</italic>=0.005) and higher ILT-4 levels (HR=2.198; <italic>p</italic>=0.063) were independent risk factors for poor outcomes in patients with CRC. In summary, among the immune checkpoints, HLA-G/ILT-2/4 and PD-L1, ILT-4 is the most significant prognostic indicator of CRC. This finding indicated that a combination of immunotherapy strategies, such as ILT-4 blockade, could improve the clinical outcomes in patients with cancer. Moreover, multicolor flow cytometry can be employed as a reliable and efficient, alternative to immunohistochemistry, for evaluating the immune checkpoint proteins expressed in tumor lesions.</p>