Interleukin-37 mediates the antitumor activity in hepatocellular carcinoma: role for CD57+ NK cells

Abstract

The biological role of interleukin-37 (IL-37) in cancer is large unknown. Through immunohistochemical detection using 163 primary hepatocellular carcinoma (HCC) clinical specimens, we found the expression of IL-37 was decreased in tumor tissues, and the expression level was negatively correlated with tumor size. High expression of IL-37 in HCC tumor tissues was associated with better overall survival (OS) and disease-free survival (DFS). IL-37 expression in tumor tissues was positively associated with the density of tumor-infiltrating CD57+ natural killer (NK) cells, but not with the CD3+ and CD8+ T cells. Consistently, in vitro chemotaxis analysis showed that IL-37- overexpressing HCC cells could recruit more NK cells. The in vivo mouse model experiments also revealed that overexpression IL-37 in HCC cells significantly delayed tumor growth and recruited more NK cells into tumors tissues. Our finding suggested that IL-37 might play an important role for the prognosis of HCC patients via regulating innate immune-action.

Figure 1. IL-37 protein expression in primary hepatocellular carcinoma surgical specimens as shown by immunohistochemical detection.

(A) IL-37 expression in distant normal liver tissues. (B) IL-37 expression in the tumor tissues and the adjacent non-tumor tissue. (C) and (D) IL-37 positively staining in some tumor cases. (E) and (F) IL-37 negative staining in some tumor cases. N: non-tumor tissue; T: tumor tissue. B with 100× magnification; A, C–F with 200× magnification).

Figure 2. The Kaplan-Meier survival analysis of primary HCC patients (n = 163) with high IL-37 expression (n = 63) and low IL-37 expression (n = 100) after surgical resection.

The overall survival (OS) (A) and disease free survival (DFS) (B) rate of the patients in the low-IL-37 group and in the high-IL-37 group.

Figure 3. Relationship between IL-37 expression and CD57+ NK cells, CD3+ T cells and CD8+ T cells in the tumor microenvironment.

(A) Representative photomicrographs showing immunohistochemical staining for IL-37, CD57, CD3 and CD8 in the same primary HCC tumors. The correlation of IL-37 expression with CD57+ NK cells (B), CD3+ T cells (C) and CD8+ T cells (D) was shown. (E) Kaplan-Meier survival curves of HCC patients (n = 163) with high CD57+ NK cells density (n = 82) and low CD57+ NK cells density (n = 81) after surgical resection.

Figure 4. The impact of IL-37 on the chemotaxis and migration of NK cells, CD3+ T cells and CD8+ T cells.

(A) Stable IL-37 expression in Hep3B cells was confirmed by western blotting. The cropped blots were shown. The recruitment of NK cells (B), CD3+ T cells (C) and CD8+ T cells (D) by the supernatant from Hep3B/LV-IL37 cells or Hep3B/LV-NC cells was compared. The values shown are expressed as the mean ± SD of three independent experiments. The p values were calculated using Student's t-test.

Figure 5. Overexpression of IL-37 delayed tumor growth and enhanced local CD57+ NK cells infiltration within murine tumors.

(A) Stable IL-37 expression in Hepa1-6 cells was confirmed by western blotting. The cropped blots were shown. (B) The tumor growth curves of IL-37 overexpression group (Hepa 1-6/LV-IL37) and control group (Hepa 1-6/LV-NC) were compared. * p < 0.05 versus control. (C) Photographs of dissected tumors from the C57BL/6 mice of IL-37 overexpression group and control group. (D) Dissected tumor weights from IL-37 overexpression group and control group were compared. (E) Representative photomicrographs showing immunohistochemical staining of IL-37, CD57, CD3 and CD8 in murine tumors. (F) The density of CD57+ NK cells, CD3+ or CD8+ T cell infiltration in IL-37 overexpression group and control group was compared. The values shown are expressed as the mean ± SD. The p values were calculated using Student's t-test.