Correlation between Density of CD8+ T-cell Infiltrate in Microsatellite Unstable Colorectal Cancers and Frameshift Mutations: A Rationale for Personalized Immunotherapy.

Pauline Maby,Mohamad Hamieh,Gabriela Bindea,Hafid Kora,Thierry Frébourg,Florence Le Pessot,Richard Sesboüé,Jérôme Leprince,Jérôme Galon,David Tougeron,Bernhard Mlecnik,Jean-Baptiste Latouche,Jacques Mauillon,Helen K Angell,Aurélie Drouet,Nicolas Elie,Tessa Fredriksen,Émilie Fauquembergue ,Jean‐Jacques Tuech ,Jacques Bénichou ,Pierre Martineau ,Jean–Christophe Sabourin

doi:10.1158/0008-5472.can-14-3051

Abstract

Colorectal cancers with microsatellite instability (MSI) represent 15% of all colorectal cancers, including Lynch syndrome as the most frequent hereditary form of this disease. Notably, MSI colorectal cancers have a higher density of tumor-infiltrating lymphocytes (TIL) than other colorectal cancers. This feature is thought to reflect the accumulation of frameshift mutations in sequences that are repeated within gene coding regions, thereby leading to the synthesis of neoantigens recognized by CD8(+) T cells. However, there has yet to be a clear link established between CD8(+) TIL density and frameshift mutations in colorectal cancer. In this study, we examined this link in 103 MSI colorectal cancers from two independent cohorts where frameshift mutations in 19 genes were analyzed and CD3(+), CD8(+), and FOXP3(+) TIL densities were quantitated. We found that CD8(+) TIL density correlated positively with the total number of frameshift mutations. TIL densities increased when frameshift mutations were present within the ASTE1, HNF1A, or TCF7L2 genes, increasing even further when at least one of these frameshift mutations was present in all tumor cells. Through in vitro assays using engineered antigen-presenting cells, we were able to stimulate peripheral cytotoxic T cells obtained from colorectal cancer patients with peptides derived from frameshift mutations found in their tumors. Taken together, our results highlight the importance of a CD8(+) T cell immune response against MSI colorectal cancer-specific neoantigens, establishing a preclinical rationale to target them as a personalized cellular immunotherapy strategy, an especially appealing goal for patients with Lynch syndrome.

Highlights

Colorectal cancers with high density of tumor-infiltrating lymphocytes (TIL), especially of CD8þ T lymphocytes (TL), areNote: Supplementary data for this article are available at Cancer Research Online.Ó2015 American Association for Cancer Research.associated with a better prognosis [1,2,3,4], suggesting that a cytotoxic antitumor immune response could control colorectal cancer progression
In 52 microsatellite instability (MSI) colorectal cancers, that frameshift mutation number and spectrum correlated with total (CD3þ) TIL density [16]
We found that frameshift mutations of ASTE1, HNF1A, and TCF7L2 genes were correlated with an increased CD8þ TIL density (P < 0.05 in at least two among four independent compartments, that is, epithelium in tumor center, epithelium in invasion front, stroma in tumor center, stroma in invasion front)

Summary

Introduction

Colorectal cancers with high density of tumor-infiltrating lymphocytes (TIL), especially of CD8þ T lymphocytes (TL), areNote: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/).Ó2015 American Association for Cancer Research.associated with a better prognosis [1,2,3,4], suggesting that a cytotoxic antitumor immune response could control colorectal cancer progression. MSI colorectal cancers are known to have a better prognosis [5,6,7,8] and a more dense infiltration of intraepithelial activated CD8þ TLs than microsatellite stable (MSS) colorectal cancers [9,10,11,12,13], suggesting that MSI colorectal cancers are prone to a local cytotoxic cellular immune response. The link between stronger immunogenicity of MSI colorectal cancers and MMR deficiency is commonly explained by the accumulation of frameshift mutations within coding sequences and the synthesis of neoantigens [14] Degradation of such neoantigens can release immunogenic neopeptides, presented by human leukocyte antigen class I (HLA-I) molecules, on the tumor cell surface, and targeted by a specific CD8þ cellular immune response. TLs from MSI colorectal cancer patients have already been activated against some

Methods

Results

Conclusion