Prognostic impact of CD73 and A2A adenosine receptor expression in non-small-cell lung cancer

Abstract

In immune cells, CD73 dephosphorylates and converts extracellular AMP into adenosine, which binds the A2A adenosine receptor (A2AR). Blockade of this interaction, which induces an immunosuppressed niche in the tumor microenvironment, represents a potential novel treatment strategy. The clinical significance of CD73 and A2AR expression in non-small-cell lung cancer (NSCLC), however, has yet to be thoroughly investigated. Here we evaluated CD73 and A2AR protein expression levels using immunohistochemistry in tissue microarrays containing 642 resected NSCLC specimens. Furthermore, we compared the expression profiles of 133 paired primary tumors and lymph node metastases. CD73 and A2AR expression levels were significantly higher in females than in males, in never smokers than in ever smokers, and in adenocarcinomas than in squamous cell carcinomas. Among adenocarcinomas, significantly higher CD73 and A2AR expression was observed in TTF-1-positive and mutant EGFR-positive tumors than in their counterparts. Compared with CD73, A2AR expression was more inconsistent between primary tumors and lymph node metastases. Among NSCLC patients, high CD73 expression was an independent indicator of poor prognosis in multivariate Cox regression analyses for overall survival [hazard ratio (HR), 2.18; 95% confidence interval (CI), 1.38-3.46] and recurrence-free survival (HR, 2.05; 95% CI, 1.42-2.95). In contrast, high A2AR expression was an independent predictor of favorable prognosis for overall survival (HR, 0.70; 95% CI, 0.50-0.98) and recurrence-free survival (HR, 0.74; 95% CI, 0.56-0.97). Together, these findings indicate that CD73 and A2AR have opposing prognostic effects, although cases involving CD73 or A2AR expression share some clinicopathological features.

Keywords: A2AR; CD73; adenosine; non-small-cell lung cancer; prognosis.

Figure 1. Representative images from an immunohistochemistry analysis of CD73 and A2AR and representative images for immune infiltration assessment

Images of each CD73 membranous intensity level [0 (absent), 1 (weak), 2 (moderate), and 3 (strong), upper panel] and each A2AR membranous and cytoplasmic intensity level [0 (absent), 1 (weak), 2 (moderate), and 3 (strong), middle panel] are shown (original magnification, ×40). In the hematoxylin and eosin (HE)-stained panel (lower panel), images of each intensity of immune infiltration [0 (no), 1 (mild), 2 (moderate), and 3 (strong)] are shown (original magnification, ×40). The black arrow in the CD73-stained panel indicates CD73-positive lymphocytes, which are used as positive internal controls. The scale bars are 50 μm.

Figure 2. CD73 and A2AR expression levels according to clinicopathological factors

CD73 A. and A2AR B. expression levels are plotted according to sex, smoking status, and histology. Each box plot indicates the median and interquartile range (top and bottom borders of the box). The whiskers above and below each box represent 1.5× of the interquartile range. Abbreviations: ADC, adenocarcinoma; SqCC, squamous cell carcinoma.

Figure 3. Kaplan–Meier estimates of overall survival and recurrence-free survival (years) stratified according to CD73 or A2AR expression levels in patients with non-small cell lung cancer

Significant differences in overall survival A. and recurrence-free survival B. are shown for non-small-cell lung cancer (NSCLC) patients with high CD73 expression vs. those with low CD73 expression. Patients with NSCLCs harboring high A2AR expression had significantly better overall survival C. and recurrence-free survival D. outcomes than those with low A2AR expression. Survival estimations stratified by combined tumor CD73 and A2AR expression status are shown for overall survival E. and recurrence-free survival F.

Figure 4. CD73 and A2AR expression levels in adenocarcinomas

CD73 A. and A2AR B. expression levels are plotted according to TTF-1 positivity, mutant EGFR expression, and ALK positivity. Each box plot shows the median and interquartile range (top and bottom borders of the box). The whiskers above and below each box represent 1.5× of the interquartile range.

Figure 5. Kaplan–Meier estimates of overall survival and recurrence-free survival (years) stratified according to CD73 or A2AR expression levels in patients with lung adenocarcinoma

Patients with adenocarcinoma and high CD73 expression had significantly worse overall survival A. and recurrence-free survival B. outcomes than did those with low CD73 expression. Adenocarcinoma patients harboring high A2AR expression had significantly better survival outcomes for overall survival C. and recurrence-free survival D. than did those with low A2AR expression. Survival estimations of adenocarcinoma patients stratified by combined tumor CD73 and A2AR expression status are shown for overall survival E. and recurrence-free survival F.