Intra-tumoral heterogeneity in the expression of programmed-death (PD) ligands in isogeneic primary and metastatic lung cancer: Implications for immunotherapy

Abstract

Purpose: There is inconclusive evidence to suggest the expression of programmed cell death (PD) ligand 1 (PD-L1) is a putative predictor of response to PD-1/PD-L1-targeted therapies in lung cancer. We evaluated the heterogeneity in the expression of PD-1 ligands in isogeneic primary and metastatic LC specimens. Experimental Design: From 12,580 post mortem cases, we identified 214 patients with untreated metastatic LC, of which 98 had adequately preserved tissues to construct a syngeneic primary LC/metastasis tissue microarray. Immunostaining for PD-L1 and 2 was evaluated in paired primary and metastatic lesions and correlated with clinicopathologic features. Results: We included 98 patients with non-small cell (NSCLC, n = 65, 66%), small cell histology (SCLC, n = 29, 30%) and four (4%) atypical carcinoids (AC). In total 8/65 (12%) primary PD-L1 positive NSCLC, had discordant matched metastases (14/17, 82%). PD-L1 negative primaries had universally concordant distant metastases. SCLCs were universally PD-L1 negative across primary and metastatic disease. PD-L2 positive NSCLC (n = 11/65, 17%) had high rate of discordant metastases (n = 24/27, 88%) and four cases (6%) had PD-L2 positive metastases with negative primaries. 2/29 SCLC (7%) and 1/4 AC (25%) were PD-L2 positive with discordance in all the sampled metastatic sites (n = 5). We found no correlation between the expression of PD ligands and clinicopathologic features of LC. Conclusions: Intra-tumoral heterogeneity in the expression of PD ligands is common in NSCLC, while PD-L1 is homogeneously undetectable in primary and metastatic SCLC. This holds implications in the clinical development of immune response biomarkers in LC.

Keywords: Heterogeneity; PD-1; PD-L1; PD-L2; lung cancer.

Figure 1.

Scatter plot illustrating the distribution of PD-L1 and PD-L2 immunoreactivity expressed by histoscore values across primary tumors, lymphnode and visceral metastases of NSCLC (Panels A and B) and SCLC (Panel C). Panels (D)and (E)describe the heterogeneity in the expression of PD-L1 (Panel D) and PD-L2 (Panel E) across paired primary and metastatic NSCLC deposits stratified according to PD-L1 and PD-L2 primary tumor expression status.

Figure 2.

Representative sections showing a case of primary SCLCs are shown at 100× magnification. Panel (A)shows a case staining negatively for PD-L1. A case of PD-L2 expressing SCLC is shown in Panel B. Panel (C)shows a case of a PD-L1 positive primary lung adenocarcinoma. Strongly positive PD-L1 tumor cells are abutting an area of tumor necrosis and are associated with a strong lymphocytic infiltrate. Panels (D)and (E)show representative sections of a strongly PD-L2 positive and PD-L2 negative primary lung adenocarcinomas.

Figure 3.

Representative sections at 100× magnification showing a case of PD-L1 positive primary lung adenocarcinoma (Case ID nr. 7, Panel A) with a matched, concordant PD-L1 positive metastatic deposit to the myocardium (Panel B) and a second discordant PD-L1 negative metastatic deposit to the thyroid (Panel C). Panel (D)shows the only identified case of a PD-L1 negative primary adenocarcinoma with evidence of a PD-L1 positive lymphnode metastatic deposit (Panel E). Both specimens show anthracotic pigmentation, more prominent in Panel E. Panel (F)illustrates a PD-L1 positive squamous cell carcinoma (Case ID nr. 5) with evidence of a peritumoral lymphocytic infiltrate and a paired PD-L1 positive lymphnode metastasis shown at 100 × and 400 × magnification (Panel G, H).