Lack of association of immune checkpoint protein expression with T stage or stage grouping in colorectal cancer (CRC): A tissue microarray (TMA) based analysis of clinical data.

Abstract

e15241 Background: Immunotherapy is a valuable therapeutic intervention in multiple cancer types. In CRC, it is currently limited to those with microsatellite instability–high expression. Thus, immunotyping of CRC patients is critical to identifying potential targets for drug development. In this study, we profiled 171 CRC patient tumor samples to assess the expression of three immune check-point regulators (HHLA2, B7H3, and PD-L1), and 3 clinically useful biomarkers (CK7, CK20, and CDX2) and their association with T stage and stage grouping. Methods: TMA was created from 171 samples of CRC diagnosed between 2000 and 2016 in a major urban cancer center. Formalin fixed paraffin embedded (FFPE) tissues were used for immunohistochemistry (IHC). Antibodies specific for IHC staining were used for HHLA2, B7H3, PD-L1, CK7, CK20, and CDX2. Each specimen was scored from 4-12, based on multiplication of tumor tissue staining value (1 if 1-25%, 2 if 26-50%, 3 if 51-75%, and 4 if 76-100% of area visualized) by the intensity (1-3X). Expression of the proteins was sub divided into two or three groups, depending on the mean expression. Association between the six proteins and pathologic features including T stage and stage grouping (based on the AJCC stage at time of diagnosis) was assessed using chi-square or Fisher Exact tests. Results: Of the 171 patients, 62 (36.3%) presented with a primary cancer that recurred at a later date, and 109 (63.7%) had metastatic disease at presentation. Twenty patients were excluded from statistical analysis due to lack of staging data. The % of tumors with positive expression was 38.1 (HHLA), 37.6 (B7H3), 54.7 (PD-L1), 20.9 (CK7), 52.5 (CK20), and 58.2 (CDX2). There was no significant association between expression of each of the 6 proteins (HHLA2, B7H3, PD-L1, CK7, CK20, and CDX2) and the T stage (T1-2, T3 or T4) or stage grouping (stage 1-2 or stage 3). Consistent with clinical expectation, the expression of CK20 was higher than CK7 (p < 0.05). Conclusions: Expression of HHLA2, B7H3, PD-L1, CK7, CK20, and CDX2 were not associated with T stage or stage grouping of CRC samples in our study. These data suggest that these proteins are expressed early in the onset of CRC. Studies to determine their predictive and prognostic implications are underway.