Evaluation of HHLA2 and CD8 Immunohistochemical Expression in Colorectal Carcinoma and Their Prognostic Significance.

Background: Colorectal carcinoma (CRC) is the third most common malignancy worldwide. Human endogenous retrovirus H long terminal repeat-associating protein 2 (HHLA2) is a novel immune checkpoint molecule. The association between HHLA2 expression and clinicopathological features and its prognostic significance in CRC patients are still controversial. The aim of this study is to evaluate the prognostic value of immunohistochemical (IHC) expression of HHLA2 and CD8 in CRC.

Material And Methods: This retrospective study included 134 cases diagnosed with primary CRC at the Gastrointestinal Surgery Center (GISC) department, Mansoura Faculty of Medicine, during the period from December 2014 to December 2018. Clinicopathological and survival data were collected. IHC for HHLA2 and CD8 was performed, and they were correlated with clinicopathological parameters and patient prognosis.

Results: Among 134 CRC cases, high HHLA2 expression was detected in 73 (54.5%). High HHLA2 expression was significantly related to the depth of invasion (P = 0.005*), lymph node metastasis (P = 0.01*), tumor stage )P = 0.002*), and distant recurrence )P = 0.012*). Multivariate analysis spotted HHLA2 high expression as an independent prognostic predictor for OS in CRC (P = 0.03*) and DFS (P = 0.008*). CD8 shows a significant correlation with tumor infiltrating lymphocytes (TILs) (P ≤ 0.001*), absence of metastasis ((P = 0.029*), absence of tumor deposits (P=0.014*). However, CD8 shows no significant association with survival or HHLA2.

Conclusion: HHLA2 is an independent prognostic factor for the overall survival and disease free survival of CRC patients and can predict poor prognosis in CRC patients.