Effects of NRAS Mutations on Leukemogenesis and Targeting of Children With Acute Lymphoblastic Leukemia

DEAPR: Differential Expression and Pathway Ranking Tool Demonstrates NRASG12V and NRASG12D Mutations Have Differing Effects in THP-1 Cells

Background/Objectives: NRAS mutations are found in approximately 10% of patients with acute myeloid leukemia (AML), with nearly half of those occurring at codon 12, but little is known about how differing G12 mutants affect cancer cell activity. Methods: A novel bioinformatic technique, differential expression and pathway ranking (DEAPR), was used to identify the most prominent changes in terms of both individual genes and associated pathways when comparing AML THP-1 cells containing an NRASG12D mutation with B11 cells, which are THP-1-derived cells with the NRASG12D allele removed and a dox-inducible NRASG12V allele introduced. Results: In total, 1456 differentially expressed (DE) protein-coding genes were uniquely associated to the NRASG12D mutation, while 585 DE protein-coding genes were specific to the NRASG12V mutation. The innate immune system pathway was prominent in both mutant-specific lists, even though the genes involved were not in both lists. Furthermore, the two calprotectin genes (S100A8 and S100A9), also associated with innate immunity, were upregulated in the NRASG12D mutant and downregulated in the NRASG12V mutant. Conclusions: This study, using the DEAPR strategy, clearly demonstrates the dramatic changes associated with two seemingly similar NRAS mutations, suggesting the deployment of different treatment strategies based on the type of NRAS mutation present.

Rat Sarcoma Virus Family Genes in Acute Myeloid Leukemia: Pathogenetic and Clinical Implications

Acute myeloid leukemias (AMLs) comprise a group of genetically heterogeneous hematological malignancies that result in the abnormal growth of leukemic cells and halt the maturation process of normal hematopoietic stem cells. Despite using molecular and cytogenetic risk classification to guide treatment decisions, most AML patients survive for less than five years. A deeper comprehension of the disease's biology and the use of new, targeted therapy approaches could potentially increase cure rates. RAS oncogene mutations are common in AML patients, being observed in about 15-20% of AML cases. Despite extensive efforts to find targeted therapy for RAS-mutated AMLs, no effective and tolerable RAS inhibitor has received approval for use against AMLs. The frequency of RAS mutations increases in the context of AMLs' chemoresistance; thus, novel anti-RAS strategies to overcome drug resistance and improve patients' therapy responses and overall survival are the need of the hour. In this article, we aim to update the current knowledge on the role of RAS mutations and anti-RAS strategies in AML treatments.

Advances and Challenges in RAS Signaling Targeted Therapy in Leukemia

RAS mutations are prevalent in leukemia, including mutations at G12, G13, T58, Q61, K117, and A146. These mutations are often crucial for tumor initiation, maintenance, and recurrence. Although much is known about RAS function in the last 40 years, a substantial knowledge gap remains in understanding the mutation-specific biological activities of RAS in cancer and the approaches needed to target specific RAS mutants effectively. The recent approval of KRASG12C inhibitors, adagrasib and sotorasib, has validated KRAS as a direct therapeutic target and demonstrated the feasibility of selectively targeting specific RAS mutants. Nevertheless, KRASG12C remains the only RAS mutant successfully targeted with FDA-approved inhibitors for cancer treatment in patients, limiting its applicability for other oncogenic RAS mutants, such as G12D, in leukemia. Despite these challenges, new approaches have generated optimism about targeting specific RAS mutations in an allele-dependent manner for cancer therapy, supported by compelling biochemical and structural evidence, which inspires further exploration of RAS allele-specific vulnerabilities. This review will discuss the recent advances and challenges in the development of therapies targeting RAS signaling, highlight emerging therapeutic strategies, and emphasize the importance of allele-specific approaches for leukemia treatment.

Progression and perspectives in disease modeling for Juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is a rare myeloproliferative neoplasm occurring in infants and young children. JMML has been shown to be resistant to all conventional cytotoxic chemotherapy drugs, and current curative therapies still rely on hematopoietic stem cell transplantation, which carries a high risk of relapse post-transplantation. This underscores the urgent need for novel treatment strategies. However, the rarity of JMML poses a major limitation for research, as it is difficult to collect substantial primary research material. To gain a deeper insight into the underlying biological mechanisms of JMML, researchers are continuously improving and developing preclinical research models to better emulate the disease. Therefore, this review aims to delineate the various experimental models currently employed in JMML, including patient-derived cell-based models, cell models, and animal models. We will discuss the characterization of these models in the context of JMML, hoping to provide a valuable reference for researchers in this field.

Paediatric Acute Lymphoblastic Leukaemia: A Narrative Review of Current Knowledge and Advancements

PURPOSE OF REVIEW

This review aims to provide an update on current knowledge regarding paediatric acute lymphoblastic leukaemia (ALL), focusing on recent advancements in diagnosis and treatment, as well as future directions in the field.

RECENT FINDINGS

ALL is the most frequently diagnosed paediatric malignancy, with advances leading to a 90% survival rate. The heterogeneity of childhood ALL requires a precise diagnostic algorithm incorporating morphological, immunophenotypic, and cytogenetic analyses. Research is exploring next-generation sequencing and artificial intelligence-aided techniques for future diagnostic approaches. Despite these advancements, global disparities in healthcare access hinder prompt diagnosis and management. The pathophysiology of ALL involves chromosomal and genetic alterations which disrupt cell-cycle regulation and result in uncontrolled lymphoblast proliferation. Environmental factors also contribute to leukaemogenesis. Risk-stratification based on genetic subtypes has significant implications for risk-based therapy. Chemotherapy is administered in three phases: induction, consolidation, and maintenance, with prophylactic intrathecal chemotherapy considered essential. For high-risk, refractory, or relapsed ALL, haematopoietic stem cell transplantation and novel therapies such as tyrosine kinase inhibitors, chimeric antigen receptor T-cell therapy, and blinatumomab immunotherapy, have improved outcomes. Ongoing clinical trials aim to further improve treatment efficacy, reduce toxicity, and increase survival. Although prevention strategies for ALL exist at three levels, the supporting evidence remains limited, highlighting a need for further research. Continued research and clinical trials are essential to addressing the gaps treatment efficacy and prevention strategies. Efforts to improve global healthcare access and integrate novel diagnostic and therapeutic approaches are crucial for advancing outcomes for paediatric patients with ALL.

Sotorasib Is a Pan-RASG12C Inhibitor Capable of Driving Clinical Response in NRASG12C Cancers

KRASG12C inhibitors, like sotorasib and adagrasib, potently and selectively inhibit KRASG12C through a covalent interaction with the mutant cysteine, driving clinical efficacy in KRASG12C tumors. Because amino acid sequences of the three main RAS isoforms-KRAS, NRAS, and HRAS-are highly similar, we hypothesized that some KRASG12C inhibitors might also target NRASG12C and/or HRASG12C, which are less common but critical oncogenic driver mutations in some tumors. Although some inhibitors, like adagrasib, were highly selective for KRASG12C, others also potently inhibited NRASG12C and/or HRASG12C. Notably, sotorasib was five-fold more potent against NRASG12C compared with KRASG12C or HRASG12C. Structural and reciprocal mutagenesis studies suggested that differences in isoform-specific binding are mediated by a single amino acid: Histidine-95 in KRAS (Leucine-95 in NRAS). A patient with NRASG12C colorectal cancer treated with sotorasib and the anti-EGFR antibody panitumumab achieved a marked tumor response, demonstrating that sotorasib can be clinically effective in NRASG12C-mutated tumors.

SIGNIFICANCE

These studies demonstrate that certain KRASG12C inhibitors effectively target all RASG12C mutations and that sotorasib specifically is a potent NRASG12C inhibitor capable of driving clinical responses. These findings have important implications for the treatment of patients with NRASG12C or HRASG12C cancers and could guide design of NRAS or HRAS inhibitors. See related commentary by Seale and Misale, p. 698. This article is featured in Selected Articles from This Issue, p. 695.

Leukemic conversion involving RAS mutations of type 1 CALR-mutated primary myelofibrosis in a patient treated for HCV cirrhosis: a case report

Somatic frameshift mutations in exon 9 of calreticulin (CALR) gene are recognized as disease drivers in primary myelofibrosis (PMF), one of the three classical Philadelphia-negative myeloproliferative neoplasms (MPNs). Type 1/type 1-like CALR mutations particularly confer a favorable prognostic and survival advantage in PMF patients. We report an unusual case of PMF incidentally diagnosed in a 68-year-old woman known with hepatitis C virus (HCV) cirrhosis who developed a progressive painful splenomegaly, without anomalies in blood cell counts. While harboring a type 1 CALR mutation, the patient underwent a leukemic transformation in less than 1 year from diagnosis, with a lethal outcome. Analysis of paired DNA samples from chronic and leukemic phases by a targeted next-generation sequencing (NGS) panel and single-nucleotide polymorphism (SNP) microarray revealed that the leukemic clone developed from the CALR-mutated clone through the acquisition of genetic events in the RAS signaling pathway: an increased variant allele frequency of the germline NRAS Y64D mutation present in the chronic phase (via an acquired uniparental disomy of chromosome 1) and gaining NRAS G12D in the blast phase. SNP microarray analysis showed five clinically significant copy number losses at regions 7q22.1, 8q11.1-q11.21, 10p12.1-p11.22, 11p14.1-p11.2, and Xp11.4, revealing a complex karyotype already in the chronic phase. We discuss how additional mutations, detected by NGS, as well as HCV infection and antiviral therapy, might have negatively impacted this type 1 CALR-mutated PMF. We suggest that larger studies are required to determine if more careful monitoring would be needed in MPN patients also carrying HCV and receiving anti-HCV treatment.

Lineage Conversion in Pediatric B-Cell Precursor Acute Leukemia under Blinatumomab Therapy

We report incidence and deep molecular characteristics of lineage switch in 182 pediatric patients affected by B-cell precursor acute lymphoblastic leukemia (BCP-ALL), who were treated with blinatumomab. We documented six cases of lineage switch that occurred after or during blinatumomab exposure. Therefore, lineage conversion was found in 17.4% of all resistance cases (4/27) and 3.2% of relapses (2/63). Half of patients switched completely from BCP-ALL to CD19-negative acute myeloid leukemia, others retained CD19-positive B-blasts and acquired an additional CD19-negative blast population: myeloid or unclassifiable. Five patients had KMT2A gene rearrangements; one had TCF3::ZNF384 translocation. The presented cases showed consistency of gene rearrangements and fusion transcripts across initially diagnosed leukemia and lineage switch. In two of six patients, the clonal architecture assessed by IG/TR gene rearrangements was stable, while in others, loss of clones or gain of new clones was noted. KMT2A-r patients demonstrated very few additional mutations, while in the TCF3::ZNF384 case, lineage switch was accompanied by a large set of additional mutations. The immunophenotype of an existing leukemia sometimes changes via different mechanisms and with different additional molecular changes. Careful investigation of all BM compartments together with all molecular -minimal residual disease studies can lead to reliable identification of lineage switch.