CRLF2 over-Expression Is a Poor Prognostic Marker in Children with High Risk T-Cell Acute Lymphoblastic Leukemia

Abstract

Pediatric T-ALL patients have a worse outcome compared to BCP-ALL patients and they could benefit from new prognostic marker identification. Alteration of CRLF2 gene, a hallmark correlated with poor outcome in BCP-ALL, has not been reported in T-ALL.We analyzed CRLF2 expression in 212 T-ALL pediatric patients enrolled in AIEOP-BFM ALL2000 study in Italian and German centers.Seventeen out of 120 (14.2%) Italian patients presented CRLF2 mRNA expression 5 times higher than the median (CRLF2-high); they had a significantly inferior event-free survival (41.2%±11.9 vs. 68.9%±4.6, p=0.006) and overall survival (47. 1%±12.1 vs. 73.8%±4.3, p=0.009) and an increased cumulative incidence of relapse/resistance (52.9%±12.1 vs. 26.2%±4.3, p=0.007) compared to CRLF2-low patients. The prognostic value of CRLF2 over-expression was validated in the German cohort. Of note, CRLF2 over-expression was associated with poor prognosis in the high risk (HR) subgroup where CRLF2-high patients were more frequently allocated.Interestingly, although in T-ALL CRLF2 protein was localized mainly in the cytoplasm, in CRLF2-high blasts we found a trend towards a stronger TSLP-induced pSTAT5 response, sensitive to the JAK inhibitor Ruxolitinib.In conclusion, CRLF2 over-expression is a poor prognostic marker identifying a subset of HR T-ALL patients that could benefit from alternative therapy, potentially targeting the CRLF2 pathway.

CRLF2 expression associates with ICN1 stabilization in T‐cell acute lymphoblastic leukemia

“…These data are in consonance with the other two previous studies which did not find association between CRLF2 overexpression with the presence of overall NOTCH1/ FBWX7 mutations. 5,6 Noteworthy, to the best of our knowledge, our study showed for the first time a significant association between ICN1 stabilization and CRLF2 overexpression in T-ALL. Indeed, deregulation of proteasome-mediated degradation of ICN1 is the most common mechanism for NOTCH pathway aberrant activation in human cancers.…”

“…However, in terms of clinical outcome, others have shown that children with CRLF2 overexpression were prednisone poor responders 6,7 and had significantly worse overall survival (OS), event-free survival, and cumulative incidence of relapse. 5 In a series of adult T-ALL, cases with CRLF2-high showed significantly poorer OS (11 vs 32 months). 7 These findings highlight the importance of identifying these patients at diagnosis for an adequate clinical management.…”

“…The two previous studies evaluating CRLF2 overexpression in pediatric T-ALL detected similar frequencies of patients with this aberration (14% and 15%) despite using a different cutoff. 5,6 To determine a possible correlation between clinical-demographic and molecular characteristics and CRLF2 expression levels, we compared patients with either CRLF2 overexpression (CRLF2-high) or CRLF2 low expression (CRLF2-low). No significant difference with regard to age, sex, WBC count, national cancer institute (NCI) risk classification, and molecular groups (including IKZF1 mutations/deletions) was observed (Supporting Information Table S1).…”

“…Despite extensive efforts to find abnormalities responsible for this upregulation, such as P2RY8-CRLF2, IGH-CRLF2, and STIL-TAL1 rearrangements and CRLF2, NOTCH1/FBXW7, IL7R, and JAK2 mutations, no molecular alteration was associated with CRLF2 overexpression. 5,6 In 2016, a study showed that CRLF2 is a direct target of IKZF1; strong IKZF1 binding peaks were detected in the promoter region of CRLF2 using B-and T-ALL cell lines and it was subsequently shown that IKZF1 suppresses the promoter activity and the expression of CRLF2. 7 Moreover, as previously shown by the Beverly and Capobianco study 8 of target genes.…”

Molecular characterization of acute lymphoblastic leukemia with high CRLF2 gene expression in childhood

“…The expression ratio was calculated using comparative Ct analysis (2 −ΔΔCt ). As in previous studies, CRLF2 high expression was defined as an expression level 20‐fold or greater than the median expression value in pB‐ALL patients and fivefold or greater than the median expression value for T‐cell acute lymphoblastic leukemia (T‐ALL) patients as previously described …”