Similar T-cell repertoires of tumor infiltrating lymphocytes and Crohn’s-like lymphoid reaction in colorectal cancer.

e15133 Background: Tumor infiltrating lymphocytes (TILs) and Crohn’s-like Lymphoid Reaction (CLR) are independently associated with improved survival in colorectal cancer (CRC). Whereas TILs are localized within tumors, CLR are extra-tumoral lymphocytic aggregates. The origins and relationships of the T-cell repertoire of TILs and the T cells within CLR of the colorectal cancer tumor microenvironment are unknown. Methods: Expert pathology review identified and circled areas of invasive adenocarcinoma and areas containing CLR from 13 CRC patients for macrodissection from formalin fixed paraffin embedded (FFPE) slides. DNA was extracted from matched tumor and CLR areas for multiplex PCR sequencing of the CDR3 region of the T-cell receptor beta chain (TCRβ), using the immunoSEQ platform. This approach permits 1) estimating the T-cell content of each sample, 2) measuring the clonality of the T-cell repertoire as a measure of diversity, and 3) quantifying the overlap and similarity of T-cell repertoires across samples. Results: The T-cell content (Spearman’s rs = 0.56, p = 0.046) and clonality (Spearman’s rs = 0.66, p = 0.014) were highly correlated among matched tumor and CLR samples. The ten most frequently identified TIL clones were found at similar frequencies in matched CLR enriched tissues. Comparisons of all the clones detected in tumor and matched CLR tissue demonstrated substantial similarity of these immune repertoires, with an average of 186 shared clones between samples. This degree of similarity was significantly greater than published reports of the similarity of the T-cell repertoire of colorectal tumors and adjacent normal tissue (p = 1.1e-5). Conclusions: The T-cell repertoire of CLR is highly similar to the tumor infiltrating T-cell repertoire, providing supporting evidence for the hypothesis that tumor-specific antigen presentation and lymphocyte maturation occur within CLR.