Infiltration of Lynch Colorectal Cancers by Activated Immune Cells Associates with Early Staging of the Primary Tumor and Absence of Lymph Node Metastases

Abstract

Purpose: Lynch syndrome colorectal cancers often lose human leukocyte antigen (HLA) class I expression. The outgrowth of clones with immune evasive phenotypes is thought to be positively selected by the action of cytotoxic T cells that target HLA class I-positive cancer cells. To investigate this hypothesis, we related the type and density of tumor lymphocytic infiltrate in Lynch colorectal cancers with their HLA class I phenotype and clinicopathologic stage.Experimental Design: HLA class I expression was assessed by means of immunohistochemistry. Characterization of tumor-infiltrating lymphocytes was carried out by using a triple immunofluorescence procedure that allowed the simultaneous detection of CD3-, CD8-, and granzyme B (GZMB)-positive cells. Additional markers were also used for further characterization of an elusive CD3Results: We discovered that high tumor infiltration by activated CD8 þ T cells correlated with aberrant HLA class I expression and associated with early tumor stages (P < 0.05). CD8 þ T cells were most abundant in HLA class I heterogeneous tumors (P ¼ 0.02) and frequent in HLA class I-negative cases (P ¼ 0.04) when compared with HLA class I-positive carcinomas. An elusive immune cell population (was characteristic for HLA class I-negative tumors lacking lymph node metastases (P < 0.01). Conclusions:The immune system assumes an important role in counteracting the progression of Lynch colorectal cancers and in selecting abnormal HLA class I phenotypes. Our findings support the development of clinical strategies that explore the natural antitumor immune responses occurring in Lynch syndrome carriers.

Immunoprofiles of colorectal cancer from Lynch syndrome

“…4,5,8,18,19 Gene expression profiling further linked Lynch syndrome with genes involved in antigen processing and presentation, T cell activation, natural killer cell-mediated cytotoxicity, and apoptosis. 8,20–22 Loss of B2M in 28% of the Lynch syndrome tumors was within previous reported range of 21–30% and are likely caused by frameshift mutations in microsatellite regions of the B2M gene (Figure 1).…”

“…CD68 positive macrophages were scored semi-quantitatively in the entire TMA core (area of 0.78 mm 2 ) and the percentage (10% increments) of positive cells was reported in relation to the overall cellularity in line with previous studies. 4 CD68 macrophage scores were divided into tertiles for the survival analyses since no combined survival analyses were made: CD68 low (0–9.5% CD68 positive area), CD68 intermediate (9.5–15%), and CD68 high (15–37.7%).…”

“…1–4 The MMR defect may be constitutional, in which it defines Lynch syndrome, or somatic caused by hypermethylation of the MLH1 gene promoter. Tumor-infiltrating lymphocytes have been associated with MSI and signify a favorable prognosis in sporadic as well as Lynch syndrome-associated colorectal cancer.…”

“…Tumor-infiltrating lymphocytes have been associated with MSI and signify a favorable prognosis in sporadic as well as Lynch syndrome-associated colorectal cancer. 4-9 Recently, MSI has also been identified as a predictor of response to immune modulatory treatment with checkpoint inhibitors. This development offers new and promising possibilities for individualized treatment in patients with MMR deficient tumors.…”

“…13,14 B2M loss has been associated with loss of MHC class I receptors suggesting that this subset may not elicit neoepitope-induced T cell responses. 4,15 In contrast, high levels of PD-L1 have been associated with T cell exhaustion that can be reversed by inhibition of the programmed death 1 (PD-1)/PD-L1 binding. 16 As a basis for preselection of patients, who may benefit from immunotherapy, we characterized the immunophenotypes and transcriptional immune profiles in Lynch syndrome versus MMR proficient colorectal cancers from the familial colorectal cancer type X (FCCTX) syndrome.…”