Characterization of CRLF2 Expression in Pediatric B-Cell Precursor Acute Lymphoblastic Leukemia.

Background: Acute lymphoblastic leukemia (ALL) is a heterogeneous disease with several underlying genetic ab-normalities. Several studies have tried to elucidate the prognostic significance of cytokine receptor-like factor 2 (CRLF2) overexpression in pediatric B-cell precursor (BCP)-ALL; however, it is still controversial.

Methods: CRLF2 expression was assessed by flow cytometry in 87 newly diagnosed BCP-ALL pediatric patients, and 80 age and gender-matched control group. Janus Kinase2 (JAK2) (R683) mutation analysis was also performed in those identified to have CRLF2 overexpression with adequate DNA samples by direct sequencing.

Results: CRLF2 overexpression was identified in 26/87 (29.9%) of our patients with cutoff set at mean fluorescence intensity (MFI = 3.8) using the Receiver Operating Characteristic (ROC) curve. There were no significant differences in the clinical and laboratory features between patients with high and low-CRLF2 expression, apart from thrombocytopenia which showed statistically significant association with the low-expression group (p = 0.041). Sequence analysis of samples with high CRLF2 expression (n = 23) revealed that 2/23 (8.7%) cases harbored the mutation JAK2 (R683). CRLF2 levels did not have a significant impact on either overall survival (OS) or disease free survival (DFS) (p = 0.601; p = 0.212, respectively).

Conclusions: CRLF2 overexpression was not an adverse parameter in pediatric BCP-ALL patients. However, patients with CRLF2 overexpression may harbor the JAK2 mutation presenting a group that can benefit from targeted therapy by kinase inhibitors. The usage of CRLF2 expression to monitor minimal residual disease of BCP-ALL would be an area of interest for further evaluation.