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Impact of HLA-E Overexpression by Tumor Cells on the Biology of TIL in Colorectal Cancer

ABSTRACT: Accumulating evidences suggest that colorectal cancer (CRC) progression is not solely determined by the genetic abnormalities of the tumor cells but also by the host response. Indeed, recent studies in CRC have associated improved survival with a high number of tumor-infiltrating (TIL) memory and cytotoxic T lymphocytes, suggesting a link between tumor progression and in situ T cell response. Gene expression profiling studies have clearly isolated a well-known subgroup of CRC characterized by microsatellite instability (MSI) CRC, associated with a strong immune response signature involving both Th1/cytotoxic and immune evasion pathways. Moreover, the investigators have previously shown that HLA-E/β2m is overexpressed by tumor cells in roughly 20% of CRC and is associated with a worse prognosis, most likely due to NK and T effector cell functions upon engagement with the inhibitory NK receptor CD94/NKG2A. However, our recent results on an enlarger cohort of patients suggest that if this observation holds true for MSS CRC, HLA-E over-expression is inversely associated with a good prognosis in MSI CRC. Thus, the phenotype and function of TIL, depending on the MSI/MSS status of CRC have to be precised. The investigators hypothesized that in MSI CRC, known to express a high number of MSI-H related frameshift peptides which represent a pool of tumor specific antigens, HLA-E could present peptides to TCR of non conventional CD8+ HLA-E-restricted alpha-betaT cells (also expressing CD94), then inducing a strong antitumor cytolytic activity. Therefore, the aim of this project is to determine the exact phenotype, function and specificity of the CD94+ TIL in CRC, depending on both the HLA-E and the MSI/MSS status of tumor cells. These results could impact the clinical practice as anti-NKG2A monoclonal antibodies or frameshift peptide based immunotherapy that could be promising new therapeutic options in CRC patients.

DISEASE(S): Colorectal Cancer,Colorectal Neoplasms

PROVIDER: 2231092 | ecrin-mdr-crc |

REPOSITORIES: ECRIN MDR

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Project description:We compared the expression of genes related to inflammatory cytotoxic functions between MSI and MSS (HLA class I negative and positive) gastrointestinal adenocarcinomas (GIACs), seeking evidence of differences in inflammatory mediators and cytotoxic T-cell responses. Twenty-two GIACs were divided into three study groups as a function of HLA class I expression and MSI phenotype. Comparison between eight high-level MSI (MSI-H) and 8 MSS/HLA+ (control) cancers identified 2170 differentially expressed genes (p< 0.05) after microarray analysis on the Affymetrix HG-U133-Plus-PM plate. We grouped genes in Gene Ontology functional categories: apoptotic programme (119 genes, p=5.1·10-7), leukocyte activation (32 genes, p=0.01), T cell activation (20 genes, p= 0.01), and cytokine production (19 genes, p= 0.04). Real-time RT-PCR and immunohistochemical evaluation were used to confirm some microarray data, finding that increased mRNA levels of pro-inflammatory cytokines and cytotoxic mediators were associated with greater infiltration by CD8+ T lymphocytes in the MSI-H group (p<0.001). Finally, tumours with immunohistochemical HLA class I negative pattern were not grouped together but rather in accordance with features of the gene expression profile of MSI or MSS tumours. As expected, genes associated with antigen processing machinery and MHC class I molecules (TAP2, B2m) were downregulated in MSS/HLA-ABC negative CRCs. In conclusion, microarray and immunohistochemical data may be useful to comprehensively assess tumour-host interactions and differentiate MSI from MSS cancers. The two types of tumours, MSI/HLA- and MSS/HLA-, showed marked differences in the composition and intensity of infiltrating leukocytes, suggesting that their immune escape strategies involve distinct pathways. Case-control study. Samples were selected according to immunological criteria: those with total loss of HLA antigens and those without alterations in the expression of HLA molecules. In addition, the microsatellite instability genotype of all the samples was also analyzed, resulting in microsatellite stability (MSS) and microsatellite instability (MSI) samples. Therefore, three groups of samples were selected: MSS/HLA+, MSS/HLA-, and MSI. The MSS/HLA+ group was used as the control.

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Impact of HLA-E Overexpression by Tumor Cells on the Biology of TIL in Colorectal Cancer

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