Abstract: Objective To explore the effect of CD99 overexpression on the morphology and differentiation-related phenotypes of
classical Hodgkin’s lymphoma cell line L428 and investigate the role of CD99 gene in Hodgkin/Reed-Sternberg (HRS) cell
generation and transformation. Methods The effect of CD99 overexpression on the cell morphology was detected by HE
staining and phalloidin staining. Differentiation-related protein expressions were detected by immunocytochemistry and flow
cytometry after stable tansfection of CD99 gene in L428 cells. Results CD99 overexpression caused a decrease of the cell size
and reorganization of the actin cytoskeleton in L428 cells. Upregulation of CD99 led to the loss of classical Hodgkin’s
lymphoma diagnosis marker CD30 and CD15 and the restoration of the B-cell makers of PAX5, CD19, CD79α, BCL-6, and
CD10. Conclusion CD99 overexpression leads to redifferentiation of L428 cells towards B cells, suggesting that the loss of
B-cell phenotype in classical Hodgkin’s lymphoma is very likely a result of down-regulated CD99 expression.