Characterization of Philadelphia-like Pre-B Acute Lymphoblastic Leukemia: Experiences in Mexican Pediatric Patients

Abstract

Ph-like subtypes with CRLF2 abnormalities are frequent among Hispano–Latino children with pre-B ALL. Therefore, there is solid ground to suggest that this subtype is frequent in Mexican patients. The genomic complexity of Ph-like subtype constitutes a challenge for diagnosis, as it requires diverse genomic methodologies that are not widely available in diagnostic centers in Mexico. Here, we propose a diagnostic strategy for Ph-like ALL in accordance with our local capacity. Pre-B ALL patients without recurrent gene fusions (104) were classified using a gene-expression profile based on Ph-like signature genes analyzed by qRT-PCR. The expressions of the CRLF2 transcript and protein were determined by qRT-PCR and flow cytometry. The P2RY8::CRLF2, IGH::CRLF2, ABL1/2 rearrangements, and Ik6 isoform were screened using RT-PCR and FISH. Surrogate markers of Jak2-Stat5/Abl/Ras pathways were analyzed by phosphoflow. Mutations in relevant kinases/transcription factors genes in Ph-like were assessed by target-specific NGS. A total of 40 patients (38.5%) were classified as Ph-like; of these, 36 had abnormalities associated with Jak2-Stat5 and 4 had Abl. The rearrangements IGH::CRLF2,P2RY8::CRLF2, and iAMP21 were particularly frequent. We propose a strategy for the detection of Ph-like patients, by analyzing the overexpression/genetic lesions of CRLF2, the Abl phosphorylation of surrogate markers confirmed by gene rearrangements, and Sanger sequencing.

Clinical, biological, and outcome features of P2RY8‐CRLF2 and CRLF2 over‐expression in pediatric B‐cell precursor acute lymphoblastic leukemia according to the CCLG‐ALL 2008 and 2018 protocol

“…25,27,28 CRLF2 rearrangements were found to be prevalence in Hispanic or Latino ethnics with high incidence up to 49.5% in Mexico population. 29 In our study of large Chinese cohort, the incidence of P2RY8-CRLF2 and IgH-CRLF2 in non-DS BCP-ALL patients was 3.33% and 0.65% respectively, which was similar to those reported by UK Leukemia and St. Jude Children's Hospital studies in unselected cohorts. 8,9 Due to various techniques used to detect CRLF2 expression and different method to define the cut-off value of CRLF2 over-expression, the frequencies of CRLF2 over-expression reported in the literatures were discrepant, ranged from 4.7% to 19%.…”

“…Over the past decades, CRLF2 alterations, including P2RY8‐CRLF2 , IgH‐CRLF2 , and CRLF2 overexpression was discovered maybe a hallmark of genetic subgroups of childhood BCP‐ALL with high risk of treatment failure 25,27,28 . CRLF2 rearrangements were found to be prevalence in Hispanic or Latino ethnics with high incidence up to 49.5% in Mexico population 29 . In our study of large Chinese cohort, the incidence of P2RY8‐CRLF2 and IgH‐CRLF2 in non‐DS BCP‐ALL patients was 3.33% and 0.65% respectively, which was similar to those reported by UK Leukemia and St. Jude Children's Hospital studies in unselected cohorts 8,9 .…”

“…Since MRD before consolidation was a very important influencing factor on long‐term outcome and we found MRD at this time‐point was an independent factor for EFS and OS and the association between P2RY8‐CRLF2 and high MRD, the independent prognostic influence of P2RY8‐CRLF2 was not validated in our study. In addition, no relationship between P2RY8‐CRLF2 and patients' outcomes was also reported by Children's Oncology Group study and Mexico cohort 27,29 . Further analysis of our cohort, unfavorable OS was discovered in patients with P2RY8‐CRLF2 treated on IR group or treated on CCLG‐2008 protocol.…”

“…27,29 Further analysis of our cohort, unfavorable OS was discovered in patients with P2RY8-CRLF2 treated on IR group or treated on CCLG-2008 protocol. The results from AIEOP-BFM ALL 2000 study in children and Children's Hospital of Chongqing Medical University of China both found the unfavorable influence of P2RY8-CRLF2 in IR BCP-ALL and the treatment protocol in the latter was also CCLG-2008 5,22.…”

Triple-hit explanation for the worse prognosis of pediatric acute lymphoblastic leukemia among Mexican and Hispanic children

“…The most relevant differences in Mexican patients are: the lower incidence of t ( 12 , 21 )( ETV6::RUNX1 ), similar to Hispanics ( 22 , 26 ). The t ( 1 , 19 )( TCF3::PBX1 ) is slightly more frequent in Mexicans than in Hispanics and non-Hispanics ( 22 , 27 ); abnormalities in CRLF2 are particularly frequent in Mexicans, with a similar incidence of IGH::CRLF2 compared to Hispanics, and P2RY8::CRLF2 is present with a higher frequency, all patients with these rearrangements presented CRLF2 overexpression ( 28 – 30 ); the iAMP21 is also frequent (10.1% in B-Others) ( 26 , 29 ). This means that in Mexicans, ETV6-RUNX1 , associated with standard prognosis, is reduced, and rearrangements of CRLF2 and iAMP21 , which confer high risk, are widely represented among Mexican patients.…”