Pan-cancer B- and T-cell transcriptome analysis of CXCL13 as a predictive marker for immune checkpoint inhibitor response.

2626 Background: Maturation of lymphoid structures and tumor-antigen presentation via B cells in the tumor microenvironment (TME) have been recognized as factors in tumor immunity. The presence of B cells and tertiary lymphoid structures appears to result in better prognosis in patients with cancer but their role in response to immunotherapy remains subject to research. This study aimed to leverage the transcriptome expression of B and T cell markers and elucidate their impact on response to immune checkpoint inhibitors (ICIs). Methods: Among 514 patients with cancer included in the Profile-Related Evidence determining Individualized Cancer therapy study (NCT02478931), 208 with advanced cancer and available date treated with ICIs were analyzed. Patients were divided into responders (progression-free survival PFS after initiation of ICI therapy: 6 or more months) and non-responders (PFS: less than 6 months). Transcriptome expression of 34 immunoregulatory markers associated with B and T cells was compared between these groups using odds ratios (ORs) of “High” transcriptome expression “High” (75-100 percentile), “Intermediate” (25-74), and “Low” (0-24), rank compared to 735 controls of each immune marker for immunotherapy responders. A logistic regression model was used to perform a multivariable analysis of ORs. Clinical characteristics between responders and non-responders were summarized, and rate of “High” transcriptome expression of identified markers contributing to immunotherapy response was summarized by cancer type. Results: In total, 82 and 126 patients were classified into responder and non-responder groups. Median age was 65.0 and 61.0, and women were 58.5% (48/82) and 54.8% (69/126) in each group, respectively. Cancer type in both groups was well balanced. In univariate analysis, “High” transcriptome expression of CXCL13, CD3, BTLA, CTLA-4, and PD-1 was significantly more frequent in the responder than non-responder group. Cluster heatmaps in both groups revealed more B and T cell enriched population in the responder group. In multivariable analysis, patients with “High” CXCL13 expression were more likely to be immunotherapy responders (OR: 3.91, 95% confidence interval CI=1.02-15.04, p=0.044). High CXCL13 transcriptome expression was most common in head and neck (25%, 3/12), breast (22.4%, 11/49), neuroendocrine (20%, 3/15), and lung (20%, 4/20) tumors. Conclusions: This pan-cancer analysis found an association between high CXCL13 mRNA expression and better response to ICI therapy. CXCL13 role in promoting a lymphoid structure in the TME by facilitating B-cell recruitment could enable anti-tumor immunity, resulting in better response to immunotherapy. This indicates that dissection of not only T cell but also B cell regulatory factors is necessary to cancer immunotherapy response and resistance mechanisms. Clinical trial information: NCT02478931 .