Abstract
Objective
Tumor immunogenicity has been proved to have an essential role in tumor development and metastasis. Cancer cell recognition of T cells can be potentially utilized in tumor prognosis and immunotherapy. However, the understanding of immune responses and T cell receptor (TCR) repertoires in many types of tumor is yet to be complete. Our aim was to explore the TCR beta-chain (TCRb) heterogeneity across renal cell carcinoma (RCC) patients, as well as the TCRb heterogeneity between tumor-infiltrating lymphocytes (TILs) and peripheral blood mononuclear cells (PBMCs).
Methods
Tumor and blood samples of thirty-nine treatment-naïve RCC patients, and blood samples of two renal neoplasm patients and ten healthy volunteers were obtained. Genomic DNA was extracted from the frozen tumor tissues and the isolated PBMCs. To prepare the TCRb library, primers were designed to amplify the CDR3 region of the TCRb gene for the followed high-throughput sequencing. The sequencing data was analyzed by an in-house immune repertoire analyzing pipeline, including Shannon diversity, clonotype abundance, pair-wise overlap and distance, and other analyses.
Results
TCRb repertoires in the RCC tumor tissues have lower diversity compared to the RCC PBMC samples while the TCRb repertoires in the non-carcinoma PBMC samples possess the highest diversity among them. The abundance of highly expressed clonotypes (HECs) in the RCC tumor samples is higher than the HECs in the RCC PBMC samples, whereas the abundance of HECs in the non-carcinoma PBMC samples was the lowest. The pair-wise distance data generated by comparing the overlap of any two included samples suggest that TCRb repertoires in RCC do not produce distinguishable pattern across pathologically classified subtypes. The comparison of two cladograms generated from the pair-wise distances with or without the HECs suggests that HEC was a major contributor to the intraindividual difference in TCRb repertoires between TILs and PBMCs.
Conclusions
Intensive interindividual and intraindividual heterogeneity in TCRb repertoire across multiple RCC subtypes can be observed in the aspect of diversity, abundance of HECs, and pair-wise distance; the intraindividual heterogeneity in RCC is mainly contributed by HECs.
Keywords: Renal cell carcinoma (RCC), immune repertoire, T cell receptor (TCR)