, Volume 60, Issue 6, pp 869-882
Date: 13 Mar 2011

Leukocyte infiltrate in gastrointestinal adenocarcinomas is strongly associated with tumor microsatellite instability but not with tumor immunogenicity

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To analyze the correlation of genomic instability with leukocyte infiltrate in gastrointestinal carcinomas (GIACs) and with tumor immunogenicity, e.g., HLA class I cell surface expression defects and galectin-3 and PDL-1 expression.

Experimental design

Lymphocyte and macrophage infiltrations were immunohistochemically studied in HLA class I negative GIACs with sporadic high-level microsatellite instability (MSI-H) or microsatellite stability (MSS).


Tumors with MSI-H were associated with the following: dense infiltration (CD45, P < 0.001); cytotoxic CD8-positive lymphocytes (P < 0.001); and a complete absence of HLA class I cell surface expression, due to inactivating β2-microglobulin (β2-m) mutation in 50% of cases. In contrast, HLA class I negative tumors with MSS were significantly associated with fewer CD8-positive lymphocytes. There was no association between microsatellite instability and other molecular features of the tumor cells, including expression of galectin-3. Finally, macrophage infiltrate in the tumors was not correlated with microsatellite instability or HLA class I cell surface expression (CD64, P = 0.63; CD163, P = 0.51).


Microsatellite instability appears to be the most important factor determining the composition, density, and localization of leukocyte infiltrate, which is independent of other molecular features such expression of HLA class I cells, galectin-3, or programmed death ligand-1. Accordingly, the strong intratumoral CD8+ T infiltration of MSI-H tumors may be produced by elevated levels of specific inflammatory chemokines in the tumor microenvironment.