Association of PD-1, PD-1 ligands, and other features of the tumor immune microenvironment with response to anti-PD-1 therapy

Abstract

Purpose: Immunomodulatory drugs differ in mechanism-of-action from directly cytotoxic cancer therapies. Identifying factors predicting clinical response could guide patient selection and therapeutic optimization.

Experimental design: Patients (N = 41) with melanoma, non-small cell lung carcinoma (NSCLC), renal cell carcinoma (RCC), colorectal carcinoma, or castration-resistant prostate cancer were treated on an early-phase trial of anti-PD-1 (nivolumab) at one institution and had evaluable pretreatment tumor specimens. Immunoarchitectural features, including PD-1, PD-L1, and PD-L2 expression, patterns of immune cell infiltration, and lymphocyte subpopulations, were assessed for interrelationships and potential correlations with clinical outcomes.

Results: Membranous (cell surface) PD-L1 expression by tumor cells and immune infiltrates varied significantly by tumor type and was most abundant in melanoma, NSCLC, and RCC. In the overall cohort, PD-L1 expression was geographically associated with infiltrating immune cells (P < 0.001), although lymphocyte-rich regions were not always associated with PD-L1 expression. Expression of PD-L1 by tumor cells and immune infiltrates was significantly associated with expression of PD-1 on lymphocytes. PD-L2, the second ligand for PD-1, was associated with PD-L1 expression. Tumor cell PD-L1 expression correlated with objective response to anti-PD-1 therapy, when analyzing either the specimen obtained closest to therapy or the highest scoring sample among multiple biopsies from individual patients. These correlations were stronger than borderline associations of PD-1 expression or the presence of intratumoral immune cell infiltrates with response.

Conclusions: Tumor PD-L1 expression reflects an immune-active microenvironment and, while associated other immunosuppressive molecules, including PD-1 and PD-L2, is the single factor most closely correlated with response to anti-PD-1 blockade. Clin Cancer Res; 20(19); 5064-74. ©2014 AACR.

Figure 1. Association of tumor PD-L1 expression with immune infiltrates

Left column: IHC for PD-L1. Right column: IHC for CD3+ TILs. Panel (A), representative specimen from a subcutaneous melanoma metastasis demonstrating focal PD-L1 expression by tumor cells geographically associated with TILs. Panel (B), diffuse membranous tumor cell PD-L1 expression in a NSCLC brain metastasis, not associated with TILs. Panels (C), colorectal carcinoma metastasis to liver with membranous PD-L1 expression on infiltrating immune cells (brown stain) but not on tumor cells (asterisks). Original magnification 200×, all panels. Higher power images and additional immunohistochemical studies of the representative melanoma and colorectal carcinoma case are shown in Supplementary Figures 2 and 3.

Figure 2. Immunoarchitechture within a melanoma lymph nodal metastasis

On a section stained with H&E (upper left), a tumor deposit is indicated by arrows and lymph node germinal centers by asterisks. Expression of PD-1, PD-L1 and PD-L2 was observed in the lymph node germinal centers, providing an internal positive control for staining. Within the tumor deposit, PD-L1 and PD-L2 were expressed by both tumor and infiltrating immune cells, associated geographically with PD-1 expression. Additional characterization of the immune infiltrate is provided in Supplementary Figure 4. Original magnification 100×, all panels.

Figure 3. Association of PD-L2 expression in the tumor microenvironment with PD-L1 expression by tumor cells

PD-L2 expression as assessed by IHC was positive in 8 of 38 tumor specimens, and was expressed on tumor cells and/or immune infiltrating cells. Although PD-L2 was observed less frequently than PD-L1 expression, when present, it was almost always geographically associated with tumor cell PD-L1 expression.