CD3+RUNX3+ lymphocyte density; an independent prognostic factor in colon and lung adenocarcinoma but not in lung squamous cell carcinoma

RUNX3, an important regulator of T-cell differentiation plays a crucial role in activation and maintenance of various T-cells including cytotoxic-, helper- and memory-cells. Former studies have highlighted RUNX3 as a prognostic factor across several cancer types, but few have studied its cell-type specific expression patterns. We used multiplex immunohistochemistry to assess and quantify cells co-expressing CD3 and RUNX3 in three cohorts consisting of 452 colon adenocarcinoma (COAD), 239 lung adenocarcinoma (LUAD) and 307 lung squamous cell carcinoma (LUSC) patients. Further, we correlated the expression of CD3/RUNX3 to disease-specific survival and to previously investigated immune markers in these cohorts. We found that a high density of CD3⁺RUNX3⁺ cells was an independent prognostic factor for disease-specific survival in COAD (HR 0.37, 95% CI 0.21-0.64) and LUAD (HR 0.61, 95% CI (0.39-0.97), but not in LUSC. Interestingly, RUNX3 expression was positively correlated with CD8 in all cohorts, CD20 in LUAD and FOXP3 in LUSC. Univariate subgroup analyses revealed that COAD patients with high numbers of both CD3⁺RUNX3⁺ and CD8⁺ cells rarely experienced a DSS event (HR 0.24, 95% CI 0.15-0.39). Contrasting previous studies, we did not observe RUNX3 expression in epithelial cells. A high level of CD3⁺RUNX3⁺ density is an independent prognostic factor in COAD and LUAD, but not in LUSC. In COAD, a subset of patients in stage II/III with CD3⁺RUNX3⁺_high/CD8 ⁺ _high may be spared adjuvant treatment due to excellent prognosis. However, further studies are needed to confirm and elucidate the protective role of CD3⁺RUNX3⁺ cells in COAD and LUAD.