P2.03b-087 PD-L1 Expression in Adenosquamous Lung Carcinoma and the Comparison with the Other Common Variants of Non-Small Cell Lung Cancer: Topic: Biomarkers

Abstract

Adenosquamous lung carcinoma (ASC) is a hybrid tumor made of adenocarcinoma and squamous cell carcinoma in one tumor. It is a rare disease with poorer prognosis comparing with the other common variants of non-small cell lung cancer (NSCLC). There is a persisting need for identifying more effective targeted therapy methods. Immune check point therapy targeted PD-1 or PD-L1 has achieved promising results in advanced stage NSCLC. PD-L1 expression has been suggested as a potential biomarker to enrich patients who will benefit from these treatments. There is limited data regarding the expression of PD-L1 in lung ASC and its correlation with the driver oncogene changes. Protein expression of PD-L1 was examined by immunohistochemistry method using the VENTANA PD-L1 (SP263) Rabbit Monoclonal Antibody. Messenger RNA level of PD-L1 was evaluated by in situ hybridization method. EGFR, K-ras, and B-raf mutation were detected by real time PCR method. Tissue microarrays (TMAs) containing formalin fixed paraffin embedded (FFPE) NSCLC cases were used in this study. This study included 51 cases of lung ASC, 133 cases of lung adenocarcinoma (AD), and 83 cases of lung squamous cell carcinoma (SCC), totally. PD-L1 expression rate in lung ASC at the mRNA level and the protein level is highly correlated, which the kappa coefficient of the two examination methods is 0.856 (P=0.000). For the 46 cases of lung ASC, which the glandular and squamous components were analyzed separately, PD-L1 expression were divergent and mainly occurred in the SCC component of lung ASC. PD-L1 expression rate in the SCC component of ASC is similar with the result of lung SCC (39% vs 29%, P=0.327); its expression rate in AD component of ASC is the same with the result of lung AD (13.7% vs 13.5%, P=1.000). There is no association between PD-L1 expression and clinicopathological characteristics in lung ASC, for example, sex, age, smoking status, clinical stage, prognosis, EGFR mutation, K-ras mutation, or B-raf mutation, et al. PD-L1 expression in the two components of lung ASC is divergent and more prone to be expressed in the SCC component. Lung ASC may be not suitable for the PD-L1 targeted therapy because of this divergent expression status.