PD-L1 and HLA Class I Antigen Expression and Clinical Course of the Disease in Intrahepatic Cholangiocarcinoma

Abstract

Purpose: More effective therapy is needed for intrahepatic cholangiocarcinoma (ICC). The encouraging clinical results obtained with checkpoint molecule-specific monoclonal antibodies (mAb) have prompted us to investigate whether this type of immunotherapy may be applicable to ICC. The aims of this study were to determine whether (i) patients mount a T-cell immune response to their ICC, (ii) checkpoint molecules are expressed on both T cells and tumor cells, and (iii) tumor cells are susceptible to recognition by cognate T cells.

Experimental design: Twenty-seven ICC tumors were analyzed for (i) lymphocyte infiltrate, (ii) HLA class I and HLA class II expression, and (iii) PD-1 and PD-L1 expression by T cells and ICC cells, respectively. The results of this analysis were correlated with the clinicopathologic characteristics of the patients investigated.

Results: Lymphocyte infiltrates were identified in all tumors. PD-L1 expression and HLA class I antigen expression by ICC cells was observed in 8 and 11, respectively, of the 27 tumors analyzed. HLA class I antigen expression correlated with CD8(+) T-cell infiltrate. Furthermore, positive HLA class I antigen expression in combination with negative/rare PD-L1 expression was associated with favorable clinical course of the disease.

Conclusions: ICC patients are likely to mount a T-cell immune response against their own tumors. Defects in HLA class I antigen expression in combination with PD-L1 expression by ICC cells provide them with an immune escape mechanism. This mechanism justifies the implementation of immunotherapy with checkpoint molecule-specific mAbs in patients bearing ICC tumors without defects in HLA class I antigen expression.

Figure 1

Representative staining patterns of formalin-fixed, paraffin-embedded primary ICC lesions with CD8- (A and B) and CD4- (C and D) specific mAbs in the fibrous septa (A and C) and tumor lobules (B and D) of ICC lesions. E–H, representative staining patterns of formalin-fixed, paraffin-embedded primary ICC lesions with HLA class I antigen-specific mAbs. Tumor tissue sections were IHC stained with a pool of mouse HLA-A–specific mAb HCA2 and HLA-B/C-specific mAb HC10 (ratio, 1:1). The staining with HLA class I antigen–specific mAbs was scored as negative (E), heterogeneous (F), and positive (G). Representative staining of fibrous septa of ICC lesion with HLA class I antigen–specific mAbs is shown (H). Magnification is indicated.

Figure 2

Correlation between HLA class I antigen expression and number of CD8⁺ T cells infiltrating the fibrous septa (FS; A) and the tumor lobules (TLs; B) in ICC lesions. Negative, heterogeneous, and positive HLA class I antigen expression is indicated with 0, 1, and 2, respectively. On each box, the central mark is the median, the edges of the box are the 25th and 75th percentiles, the whiskers extend to the most extreme data points not considered outliers, and outliers are plotted individually.

Figure 3

Representative staining patterns of fibrous septa (FS; A) and tumor lobules (TLs; B and C) of formalin-fixed, paraffin-embedded primary ICC lesions with PD-1–specific mAb. H&E staining of tumor tissue section provides orientation (D). Representative tumor cell staining patterns (E, marginal/interface; F and G, diffuse; H, patchy;) of formalin-fixed, paraffin-embedded primary ICC lesions with PD-L1–specific mAb. Magnification is indicated.

Figure 4

Correlation between HLA class I antigen expression in combination with PD-L1 expression and number of CD8⁺ T cells infiltrating in ICC lesions. Number of CD8⁺ T cells infiltrating the fibrous septa (FS; A) and the tumor lobules (TLs; B) in patients with negative/rare PD-L1 and positive HLA class I antigen expression (indicated with 1) was higher than that in patients with high PD-L1 expression (PD-L1 score ≥2), negative/heterogeneous HLA class I antigen expression or a combination of both (indicated with 0). On each box, the central mark is the median, the edges of the box are the 25th and 75th percentiles, the whiskers extend to the most extreme data points not considered outliers, and outliers are plotted individually.

Figure 5

Association of HLA class I antigen and PD-L1 expression in primary ICC lesions with OS in patients with ICC. A, the OS of patients with lesions grouped based on AJCC stage system was compared using the Kaplan–Meier method. Stage group of ICC lesions is indicated. Differences in patients' survival were analyzed using a log-rank test. B, the OS of patients with lesions stained with a positive HLA class I antigen expression in combination with negative/rare PD-L1 expression and that of lesions with high PD-L1 expression (PD-L1 score ≥ 2), negative/heterogeneous HLA class I antigen expression or a combination of both were compared using the Kaplan–Meier method. Differences in patients' survival were analyzed using a log-rank test. C, patients were stratified on HLA class I antigen expression as those with positive or negative/heterogeneous ICC. Then the OS of patients with lesions stained with high PD-L1 expression (PD-L1 score ≥2) was compared with that of patients with negative/rare PD-L1 expression using the Kaplan–Meier method. Differences in patients' survival were analyzed using a log-rank test.