Comparison of T-cell receptor repertoire restriction in blood and tumor tissue of colorectal cancer patients

Sebastian Ochsenreither,Alberto Fusi,Eckhard Thiel,Dirk Nagorsen,Natascha C Nüssler,Ulrich Keilholz,Susanne Wojtke,Antonia Busse

doi:10.1186/1479-5876-8-35

Abstract

Several immunotherapeutic approaches rely on antigen-specific T-cells. Restrictions in the T-cell receptor (TCR) repertoire were reported as indicator of anti-tumor cytotoxic T-lymphocyte (CTL) response in various tumor entities. It is unclear yet whether a TCR restriction in peripheral blood mirrors the tumor compartment. We compared the expression of TCR Vβ-families for the quantification of TCR repertoire alterations in blood and tissue samples from patients with colorectal carcinoma. Blood samples from patients with colorectal carcinoma and healthy volunteers and tissue samples of normal colonic mucosa and colorectal carcinoma were analyzed. Relative Vβ-family quantification was performed based on quantitative reverse transcribed PCR. Standard deviation and average mean of the single families were determined. Two variables describing the degree of Vβ-repertoire restriction were defined. Forty-eight blood samples and 37 tissue samples were analyzed. TCR repertoire restriction was higher in blood of tumor patients than in blood of healthy controls (p < 0.05). No difference in the degree of TCR repertoire restriction was found between carcinoma and unaffected colon tissue. We found no corresponding elevated TCR families among the different compartments blood, normal colon, and carcinoma tissue of the same patient. In conclusion, we observed a repertoire restriction in peripheral blood as well as in tumor tissue of cancer patients. However, in tumor tissue, repertoire alterations were comparable to normal mucosa, suggesting compartment-specific TCR distribution rather than alterations due to tumor-T-cell interaction questioning the presence of highly restricted clonal T-cell expansions in colorectal cancer as they have been described in other, assumingly more immunogenic tumor entities.

Highlights

Understanding the interaction between tumor and immune system might help improving immunotherapeutic approaches for malignant diseases
In this study, Tcell receptor (TCR) Vβ-family repertoire restrictions in blood and tissue of patients with colorectal carcinoma were compared using high throughput relative quantification of TCR Vβ-families based on quantitative reverse transcribed PCR (qRT PCR) technology
While a multitude of mathematical approaches have been established to describe the degree of repertoire restriction in single V-families from spectratype/ immunoscope data, to our knowledge, a model to describe global TCR repertoire restriction based on V-family quantification has not been published so far

Summary

Introduction

Understanding the interaction between tumor and immune system might help improving immunotherapeutic approaches for malignant diseases. Spontaneous T-cell responses against TAAs have been described in peripheral blood, lymph nodes, and bone marrow of patients with various malignant diseases prior to immunotherapy [2]. In colorectal cancer (CRC), spontaneous T-cell responses against several TAAs have been detected in peripheral blood, in patients with metastatic. In case of unknown or multiple epitopes, the analysis of TCR repertoire both by FACS and PCR based methods offers the opportunity to detect oligoclonal expansion of specific T-cells [14,15,16]. The dimeric transmembrane Tcell receptor (TCR) is the central mediator of epitope specific cytotoxic T-cell activation. Consisting of an α- and a β-chain in most of the cases, diversity is generated during T-cell evolution by recombinations of the gene segments V (variable), in case of the β-chain D (diversity), and J

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