Mutually exclusive expression of CD73 and PDL1 in tumors from patients (pt) with NSCLC, gastroesophageal (GE) and urothelial bladder carcinoma (UBC).
P. Martin, A. Spitzmueller, S. Wu, M. Widmaier, R. Korn, S. Althammer, J. Zha, B. W. Higgs, Z. Cooper, K. Steele , Journal of Clinical Oncology , DOI: 10.1200/JCO.2017.35.15_suppl.3079
Background: Tumors use multiple means of immune evasion, notably the programmed death-1 (PD1)/PDL1 pathway. Anti-PD1/PDL1 therapy induces
anti-tumor activity and has improved pt outcomes. Activation of the immunosuppressive CD39/CD73/adenosine pathway might play a role in pts
who do not benefit from anti-PD1/PDL1 therapies. We evaluated expression of CD73 and PDL1 and explored the association between CD73 and
intraepithelial (IE) CD8+ cells (TILs) to begin to understand their potential interplay in cancer.
Methods: Immunohistochemistry for PDL1, CD73 and CD8 was conducted on tumors of non-squamous NSCLC (NSq) (n=42), GE (n=50), and UBC (n=50). PDL1 and CD73 were scored by image analysis with Definiens software. IE CD8+ TILs were scored semi-quantitatively by a pathologist (0-2 = low; 3-4 = high). Using the top tertile of PDL1 and CD73 for high expression levels, a Fisher’s meta-analysis was calculated across the three indications.
Results: Across all tumors, 25% (35/142) were PDL1 high (+), but CD73 low (-) and another 25% (35/142) were CD73+ but PDL1- (p=0.06, see table). This trend for mutually exclusive high expression of PDL1/CD73 was strongest in GE (p<0.01). In the PDL1+ group 76% (35/46) had high IE CD8+ TILs
whereas in the CD73+ group only 35% (16/46) had high TILs (p<0.0001 using a proportions test). In the PDL1+/CD73- pt subset 77% (27/35) were
CD8+ high vs only 23% (8/35) in the PDL1-/CD73+ subset.
Conclusions: The identification of distinct pt subsets based on high PDL1 and/or CD73 expression suggests that tumors have multiple mechanisms of immune evasion. Increased IE CD8+ TILs were associated with PDL1 expression. The finding that PDL1-/ CD73+ tumors have lower IE CD8+ TILs compared to PDL1+/CD73- tumors suggests a role for CD73 in excluding IE TILs. Larger sample sets are needed to confirm these findings and to further explore any relationship with the tumor microenvironment. Our data suggests potential approaches to identify subsets of pts likely to
benefit from immunotherapy targeting PDL1 and CD73.