Clinicopathological analysis of immunohistochemical expression of CD47 and SIRPα in adult T-cell leukemia/lymphoma

The interaction of CD47 and signal-regulatory protein alpha (SIRP alpha) induces "don't eat me signal", leading suppression of phagocytosis. This signal can affect the clinical course of malignant disease. Although CD47 and SIRP alpha expression are associated with clinicopathological features in several neoplasms, the investigation for adult T-cell leukemia/lymphoma (ATLL) has not been well-documented. This study aimed to declare the association between CD47 and SIRP alpha expression and clinicopathological features in ATLL. We performed immunostaining on 73 biopsy samples and found that CD47 is primarily expressed in tumor cells, while SIRP alpha is expressed in non-neoplastic stromal cells. CD47 positive cases showed significantly higher FoxP3 (P = .0232) and lower CCR4 (P = .0214). SIRP alpha positive cases presented significantly better overall survival than SIRP alpha negative cases (P = .0132). SIRP alpha positive cases showed significantly HLA class I (P = .0062), HLA class II (P = .0133), microenvironment PD-L1 (miPD-L1) (P = .0032), and FoxP3 (P = .0229) positivity. In univariate analysis, SIRP alpha expression was significantly related to prognosis (Hazard ratio [HR] 0.470; 95% confidence interval [CI] 0.253-0.870;P = .0167], although multivariate analysis did not show SIPR alpha as an independent prognostic factor. The expression of SIRP alpha on stromal cells reflects activated immune surveillance mechanism in tumor microenvironment and induce good prognosis in ATLL. More detailed studies for gene expression or genomic abnormalities will disclose clinical and biological significance of the CD47 and SIRP alpha in ATLL.