COX-2 抑制剂降低结肠肿瘤中 PD-L1 表达并增加 I 型 TIL（肿瘤浸润淋巴细胞）的浸润

UNLABELLED: Colon cancer is initiated under inflammatory conditions associated with upregulation of immune checkpoint proteins.

We evaluated immune modulation induced by nonsteroidal anti-inflammatory agents used for colon cancer prevention. Both celecoxib and naproxen inhibited polyp growth in APC Min mice. Treatment of mice with either drug significantly decreased PD-L1 expression on polyps in a dose-dependent manner (P < 0. 0001 for both). The decrease in PD-L1 was associated with an influx of CD8+ T cells into polyps (P < 0. 0001, celecoxib; P = 0. 048, naproxen) compared with lesions from untreated animals and correlated with disease control. Naproxen is a nonselective inhibitor of both COX-1 and COX-2, and we questioned the role of the different cyclooxygenases in PD-L1 regulation. Silencing either COX-2 or COX-1 RNA in the murine colon cancer cell line MC38, reduced PD-L1 expression by 86% in COX-2-silenced cells (P < 0. 0001) while there was little effect with COX-1 siRNA compared with control.

Naproxen could inhibit the growth of MC38 in vivo. Naproxen-treated mice demonstrated a significant reduction in MC38 growth as compared with control (P < 0001). Both Tbet+ CD4 and CD8 tumor-infiltrating lymphocytes (TIL) were significantly increased (P = 0. 04 and P = 0. 038, respectively) without a concurrent increase in GATA3+ TIL (P > 0. 05). CD8+ TIL highly expressed the activation marker, CD69.

Not only was PD-L1 expression decreased on tumors, but LAG3+CD8+ T cells and PD-1 and LAG3 expression on regulatory T cells was also reduced (P = 0. 008 and P = 0. 002, respectively). These data demonstrate COX-2 inhibitors significantly decrease PD-L1 in colonic lesions and favorably impact the phenotype of tumor-infiltrating lymphocytes to control tumor growth. PREVENTION RELEVANCE: Nonsteroidal anti-inflammatories (NSAID) are an essential component of any combination chemoprevention of colon cancer.

We show NSAID treatment reduces PD-L1 expression on intestinal tumor cells. NSAID regulation of PD-L1 is dependent on COX-2 expression. These data underscore an important immunologic mechanism of action for NSAID in colon cancer prevention. See related Spotlight, p. 209.