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.

B-cell precursor acute lymphoblastic leukemia (B-ALL) is characterized by a constellation of somatic pathogenic variants associated with malignant transformation. These variants have implications for clinical management by providing clinical biomarkers. Most B-ALL cases have a sporadic presentation. However, some patients may present the disease as the neoplastic manifestation of cancer predisposition syndromes caused by germline pathogenic variants. In these cases, genetic counseling and personalized oncologic management is mandatory, considering the patient’s sensitivity to conventional therapies. In this review, we have summarized current knowledge on the biological role and clinical relevance of somatic and germline pathogenic variants associated with B-ALL, and discuss three aspects of their application as biomarkers: (1) their usefulness to determine specific molecular subtypes, predicting prognosis and response to specific therapies, (2) their influence in genetic counseling and therapy adaptation for B-ALL in the context of underlying cancer predisposition syndromes, and (3) their detection and interpretation through methodologies. We also included a brief discussion on the need to reclassify variants of uncertain significance to clarify their clinical relevance. Finally, we discuss cases illustrating the impact of somatic and germline pathogenic variants in personalized medicine.

The use of JAK inhibitors (JAKi) represents a promising therapeutic approach for patients with lymphoid leukemias (Lym-L). Clinical trials are ongoing to evaluate the safety and efficacy of JAK inhibitors. Over the last years, there have been reports of preclinical Lym-L models that developed JAKi resistance, and reports of patients treated with JAKi who experienced treatment failure. Although evidence shows that there are diverse JAKi mechanisms, no review studies have been performed that summarize and discuss this information. This scoping review aimed to provide an updated overview of the mechanisms underlying JAKi molecular resistance in Lym-L. According to a scoping review PRISMA guidelines, a search was conducted in the PubMed and Europe PMC databases for studies published from 2010 to 2024. We included articles that described the molecular resistance to JAKi in Lym-L preclinical models or patients. The search was complemented by a review of laboratory-engineered resistant mutations in genomic datasets to obtain more information about their presence in patients with Lym-L. Twenty-two articles were eligible for this review, and six different mechanisms of molecular resistance were identified: (1) point mutations in the kinase domain, (2) cooperation between double-JAK mutants, (3) inactivation of phosphatases, (4) evasion of JAK inhibition due to trans-phosphorylation of JAK family proteins, (5) upregulation of pro-survival proteins, and (6) activation of kinase cross-signaling pathways. The integrated evidence enabled the identification of specific mechanisms of molecular resistance to JAKi in Lym-L, as well as promising therapeutic approaches to prevent them. These include selecting a sensitive JAKi, choosing an effective dosage regimen, and combining inhibitory molecules.

Rearrangements and overexpression of CRLF2 are hallmarks of poor outcomes in BCR::ABL1-like B-ALL, and CRLF2 overexpression is a high-risk marker in T-ALL. However, CRLF2 alterations in pediatric hematologic malignancies other than B-ALL have not been reported. In this study, we analyzed the CRLF2 overexpression, rearrangements (P2RY8::CRLF2 and IGH::CRLF2), activation (pSTAT5 and pERK), and the expression of dominant-negative IKZF1 isoforms (Ik6 and Ik8), implied in CRLF2 dysregulation, in 16 pediatric patients (AML, n = 9; T-ALL, n = 3; LBL, n = 2; HL, n = 1; cytopenia, n = 1). A high frequency of CRLF2 rearrangements and overexpression was found in the 16 patients: 28.6% (4/14) showed CRLF2 overexpression, 93.8% (15/16) were positive for CRLF2 total protein (cell-surface and/or cytoplasmic), while 62.5% (10/16) were positive for P2RY8::CRLF2 and 12.6% (2/16) for IGH::CRLF2. In addition, 43.8% (7/16) expressed Ik6 and Ik8 isoforms. However, only a few patients were positive for the surrogate markers pSTAT5 (14.3%; 2/14) and pERK (21.4%; 3/14).