Tumor infiltration by FcγRIII (CD16)+ myeloid cells is associated with improved survival in patients with colorectal carcinoma

Abstract

The prognostic significance of macrophage and natural killer (NK) cell infiltration in colorectal carcinoma (CRC) microenvironment is unclear. We investigated the CRC innate inflammatory infiltrate in over 1,600 CRC using two independent tissue microarrays and immunohistochemistry. Survival time was assessed using the Kaplan-Meier method and Cox proportional hazards regression analysis in a multivariable setting. Spearman's rank correlation tested the association between macrophage and lymphocyte infiltration. The Basel study included over 1,400 CRCs. The level of CD16+ cell infiltration correlated with that of CD3+ and CD8+ lymphocytes but not with NK cell infiltration. Patients with high CD16+ cell infiltration (score 2) survived longer than patients with low (score 1) infiltration (p = 0.008), while no survival difference between patients with score 1 or 2 for CD56+ (p = 0.264) or CD57+ cell (p = 0.583) infiltration was detected. CD16+ infiltrate was associated with improved survival even after adjusting for known prognostic factors including pT, pN, grade, vascular invasion, tumor growth and age [(p = 0.001: HR (95% CI) = 0.71 (0.6-0.9)]. These effects were independent from CD8+ lymphocyte infiltration [(p = 0.036: HR (95% CI) = 0.81 (0.7-0.9)] and presence of metastases [(p = 0.002: HR (95% CI) = 0.43 (0.3-0.7)]. Phenotypic studies identified CD16+ as CD45+CD33+CD11b+CD11c+ but CD64- HLA-DR-myeloid cells. Beneficial effects of CD16+ cell infiltration were independently validated by a study carried out at the University of Athens confirming that patients with CD16 score 2 survived longer than patients with score 1 CRCs (p = 0.011). Thus, CD16+ cell infiltration represents a novel favorable prognostic factor in CRC.

Figure 1

Phenotypic analysis of innate inflammatory infiltrate in the CRC microenvironment. Upper left panel documents CD16+ cell infiltration in CRC lesions. The four pictures show representative examples of different numbers of CD16+ cells infiltrating CRC microenvironment. Brown staining identifies labeled cells. The indicated marker highlights the size of CD16+ cells. Lower left panel documents infiltration by CD16+ and CD56+ cells in CRC. Panels (a) and (b) show two representative CRC lesions with ≤10 and >10 infiltrating CD16+ cells, corresponding to score 1 and 2 staining, respectively (see “Patients and Methods” section). Panels (c) and (d), show two representative CRC lesions with ≤4 and >4 infiltrating CD56+ cells, corresponding to score 1 and 2 staining, respectively. Right panel: Phenotypic analysis of CD16+ cells infiltrating a representative CRC specimen. Specific markers are indicated in individual histograms.

Figure 2

CD16+ cell infiltration is associated with improved overall survival in CRC patients. Kaplan–Meier plots depict overall survival of patients bearing CRC showing score 1 (black lines) or 2 (purple lines) infiltration by cells expressing the indicated markers. Significance of differences eventually observed is also reported. Panels (a–c) refer to the Basel tumor array, whereas panel (d) reports data from the study independently performed in Athens.

Figure 3

Effect of the combination of CD16+ and CD68+ cell infiltration on overall survival in CRC patients. Kaplan–Meier plot of panel (a) indicates that score of CD68+ cell infiltration of CRC is not associated with differential overall survival. In panel (b), CRC patients were subdivided in four subgroups according to CD16/CD68 specific ratio. Black line refers to a 0–0.18 CD16/CD68 positive cell infiltration ratio, whereas purple line, green line and blue line refer to 0.18–0.35, 0.35–0.52 and >0.52 ratios. Higher ratios are associated with significantly improved overall survival.