Mini PROTACs: N-end rule-mediated degradation on the horizon.

Heterobifunctional proteolysis-targeting chimeras (PROTACs) offer a promising cancer treatment avenue by efficiently degrading unwanted cellular proteins. A recent study from Zhang et al. demonstrated the successful utilization of the N-end rule in PROTAC design, allowing for a modular degradation rate tailored to the oncogenic driver BCR-ABL.

Low-Level BCR::ABL1 Transcript at Diagnosis in Childhood Leukemia: A 10-Year Single Institution Study.

INTRODUCTION: Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) is a high risk form of ALL associated with dismal outcomes in the pre-tyrosine kinase inhibitor (TKI) era. Addition of a TKI to chemotherapy improves outcomes. Therefore, testing for the presence of the Philadelphia chromosome by at least two methods at the time of diagnosis is critical. Diagnostic testing may include karyotype, fluorescent in situ hybridisation (FISH), and RT-PCR for the BCR::ABL1 transcript. The significance of low-level BCR::ABL1 transcript by RT-PCR in the absence of the Philadelphia chromosome on karyotype or by FISH is unknown. METHODS: This is a retrospective review of children diagnosed with acute leukemia at our institution from 2010 to 2020. Those positive for the BCR::ABL1 transcript by qualitative RT-PCR, and negative for t(9;22) by karyotype or FISH were analyzed for demographics, cytogenetic and molecular features at diagnosis and relapse, treatment and outcomes. The Kaplan-Meier method was used to estimate event-free and overall survival. RESULTS: Forty-seven of 306 (15%) patients with Ph- ALL had low-level BCR::ABL1 detected by RT-PCR. Most (77%) had B-cell ALL. The e1a2 transcript was detected most frequently, in 43 (91%) patients. BCR::ABL1 was quantifiable in 12/43 (28%) patients, with a median of 0.0008% (range 0.0003-0.095%). Seven patients (15%) relapsed. No patient with low-level BCR::ABL1 at diagnosis developed Ph + ALL at relapse. There was no difference in 5-year event-free (77% versus 81%, p = 0.407) or overall survival (86% versus 91%, p = 0.3) between children with low-level BCR::ABL1 (n = 47) and those without (n = 259). CONCLUSION: BCR::ABL1 low-level positivity in children with newly diagnosed Ph- ALL is a relatively common finding and did not adversely affect outcome for patients treated using a contemporary risk-adapted approach.

ASP210: a potent oligonucleotide-based inhibitor effective against TKI-resistant CML cells.

Clinical experience with tyrosine kinase inhibitors (TKIs) over the past two decades has shown that, despite the apparent therapeutic benefit, nearly 30% of patients with chronic myelogenous leukemia (CML) display primary resistance or intolerance to TKIs, and approximately 25% of those treated are forced to switch TKIs at least once during therapy due to acquired resistance. Safe and effective treatment modalities targeting leukemic clones that escape TKI therapy could hence be game changers in the professional management of these patients. Here, we aimed to investigate the efficacy of a novel therapeutic oligonucleotide of unconventional design, called ASP210, to reduce BCR-ABL1 mRNA levels in TKI-resistant CML cells, with the assumption of inducing their apoptosis. Imatinib- and dasatinib-resistant sublines of BCR-ABL1-positive MOLM-7 and CML-T1 cells were established and exposed to 0.25 and 2.5 µM ASP210 for 10 days. RT-qPCR showed a remarkable reduction of the target mRNA level by >99% after a single application. Cell viability was monitored daily by trypan blue staining. In response to the lack of driver oncoprotein BCR-ABL1, TKI-resistant CML cells underwent apoptosis regardless of the presence of the clinically relevant T315I mutation by day 5 after redosing with ASP210. The effect was selective for cancer cells, indicating a favorable safety profile for this therapeutic modality. Furthermore, the spontaneous uptake and high intracellular concentrations of ASP210 suggest its potential to be effective at relatively low doses. The present findings suggest that ASP210 is a promising therapeutic avenue for patients with CML who fail to respond to TKI therapy.NEW & NOTEWORTHY Effective treatment modalities targeting leukemic clones that escape tyrosine kinase inhibitor (TKI) therapy could be game changers in the professional management of patients displaying primary resistance, intolerance, or acquired resistance to TKIs. Although delivering authentic innovations today is more complex than ever, we developed a highly potent and safe oligonucleotide-based modality against BCR-ABL1 mRNA named ASP210 that effectively induces cell death in BCR-ABL1-positive TKI-resistant cells while sparing BCR-ABL1-negative healthy cells.

Increased mRNA expression for serotonin receptor 1B (HTR1B) is associated with thrombosis in BCR::ABL1-negative myeloproliferative neoplasms.

BCR::ABL1-negative myeloproliferative neoplasms (MPNs) are clonal haematopoietic stem cell disorders characterized by specific driver mutations and an increased risk of both macrothrombosis and microthrombosis. Serotonin receptor type 1B (HTR1B) was found to be expressed by various solid tumours, and also primary bone marrow mononuclear cells from myelodysplastic neoplasm and acute myeloid leukaemia patients, representing a potential therapeutic target. In this study we assessed for the first time the expression levels of HTR1B mRNA in the peripheral blood mononuclear cells (PBMC) of 85 newly diagnosed MPN patients, consisting of 28 polycythemia vera, 25 essential thrombocythemia and 32 primary myelofibrosis cases. Levels of HTR1B expression between MPN subtypes and control group were not significantly different. However, at clinical data examination, it was observed that MPN patients with a recent history of major thrombosis and/or signs of impaired microcirculation exhibited significantly higher HTR1B expression levels compared to non-thrombotic MPNs and control group. Moreover, thrombotic MPN patients had significantly higher HTR1B expression than patients with recent thrombosis and absence of MPN diagnostic criteria. These findings suggest that increased levels of HTR1B expression in PBMC might be associated with thrombosis in MPN patients, but larger studies are needed for confirmation, including testing of the receptor protein expression level.

Combined targeting of GPX4 and BCR-ABL tyrosine kinase selectively compromises BCR-ABL+ leukemia stem cells.

BACKGROUND: In the ongoing battle against BCR-ABL+ leukemia, despite significant advances with tyrosine kinase inhibitors (TKIs), the persistent challenges of drug resistance and the enduring presence of leukemic stem cells (LSCs) remain formidable barriers to achieving a cure. METHODS: In this study, we demonstrated that Disulfiram (DSF) induces ferroptosis to synergize with TKIs in inhibiting BCR-ABL+ cells, particularly targeting resistant cells and LSCs, using cell models, mouse models, and primary cells from patients. We elucidated the mechanism by which DSF promotes GPX4 degradation to induce ferroptosis through immunofluorescence, co-immunoprecipitation (CO-IP), RNA sequencing, lipid peroxidation assays, and rescue experiments. RESULTS: Here, we present compelling evidence elucidating the sensitivity of DSF, an USA FDA-approved drug for alcohol dependence, towards BCR-ABL+ cells. Our findings underscore DSF's ability to selectively induce a potent cytotoxic effect on BCR-ABL+ cell lines and effectively inhibit primary BCR-ABL+ leukemia cells. Crucially, the combined treatment of DSF with TKIs selectively eradicates TKI-insensitive stem cells and resistant cells. Of particular note is DSF's capacity to disrupt GPX4 stability, elevate the labile iron pool, and intensify lipid peroxidation, ultimately leading to ferroptotic cell death. Our investigation shows that BCR-ABL expression induces alterations in cellular iron metabolism and increases GPX4 expression. Additionally, we demonstrate the indispensability of GPX4 for LSC development and the initiation/maintenance of BCR-ABL+ leukemia. Mechanical analysis further elucidates DSF's capacity to overcome resistance by reducing GPX4 levels through the disruption of its binding with HSPA8, thereby promoting STUB1-mediated GPX4 ubiquitination and subsequent proteasomal degradation. Furthermore, the combined treatment of DSF with TKIs effectively targets both BCR-ABL+ blast cells and drug-insensitive LSCs, conferring a significant survival advantage in mouse models. CONCLUSION: In summary, the dual inhibition of GPX4 and BCR-ABL presents a promising therapeutic strategy to synergistically target blast cells and drug-insensitive LSCs in patients, offering potential avenues for advancing leukemia treatment.

A surrogate molecular approach for the detection of Philadelphia chromosome-like B-acute lymphoblastic leukemia.

BACKGROUND: Philadelphia chromosome (Ph)-like B-acute lymphoblastic leukemia (B-ALL) is a clinically significant, high-risk genetic subtype of B-ALL cases. There are few data on the incidence, characterization, and treatment outcomes of Ph-like ALL cases from low- and middle-income countries. There is a pressing need to establish a well-organized/cost-effective approach for identifying Ph-like ALL instances. METHODS: Multiplex reverse transcriptase polymerase chain reaction, nCounter NanoString, and fluorescence in situ hybridization were used to detect and characterize Ph-like ALL cases among recurrent genetic abnormalities (RGA)neg B-ALL cases. At the end of induction therapy, flow cytometry-minimal residual disease (MRD) assay was used to quantify MRD positivity in Ph-like ALL cases. RESULTS: Of 130 newly diagnosed B-ALL cases, 25% (BCR::ABL1), 4% (ETV6::RUNX1), 5% (TCF3::PBX1), 2% (KM2TA::AFF1), and 65% RGAneg B-ALL cases were revealed by multiplex reverse transcriptase polymerase chain reaction. Among RGAneg B-ALL cases, 24% Ph-like ALL cases using nCounter NanoString were identified, with 48% CRLF2high cases with 45% CRLF2::P2RY8 and 18% CRLF2::IGH rearrangements(∼r) revealed by fluorescence in situ hybridization. In 52% of CRLF2low cases, 17% ABL1 and JAK2∼r 8% EPOR::IGH & PDGRFB∼r were identified. Ph-like ALL cases had higher total leukocyte count (p < .05), male preponderance (p < .05), and high MRD-positivity/induction failure compared with RGAneg B-ALL cases. Furthermore, in Ph-like ALL cases, 11 significant genes using quantitative polymerase chain reaction were identified and validated. CRLF2, IGJ, CEACAM6, MUC4, SPATS2L and NRXN3 genes were overexpressed and show statistical significance (p < .05) in Ph-like ALL cases. CONCLUSIONS: This study showed the high incidence of Ph-like ALL cases with kinase activating alterations and treatment outcomes from low- and middle-income region. Furthermore, a surrogate cost-effective multiplex panel of 11 overexpressed genes for the prompt detection of Ph-like ALL cases is proposed. PLAIN LANGUAGE SUMMARY: Identification of recurrent gene abnormalities (RGA)neg B-acute lymphoblastic leukemia (B-ALL) cases using multiplex-reverse transcriptase polymerase chain reaction. Identification and characterization of Philadelphia (Ph)-like ALL cases using nCounter NanoString gene expression profiling and fluorescence in situ hybridization. Furthermore, Ph-like ALL cases were characterized according to CRLF2 expression and kinase-activating genomic alterations. Minimal residual disease of Ph-like ALL cases were quantified using flow cytometry-minimal residual disease assay. A surrogate molecular approach was established to detect Ph-like ALL cases from low- and middle-income countries.

Comparing de novo chronic myeloid leukemia in blastic phase with Philadelphia chromosome-positive acute lymphoblastic leukemia after allogeneic hematopoietic cell transplantation.

BACKGROUND: De novo chronic myeloid leukemia in blastic phase (CML-BP) showing lymphoid immunophenotype mimics Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph-positive ALL). Although upfront allogeneic hematopoietic cell transplantation (HCT) is considered in both diseases, it is not yet clear whether the transplant outcomes are also similar. METHODS: Using a registry database, the transplant outcomes between de novo CML-BP and Ph-positive ALL in negative-minimal residual disease (MRD), positive MRD, and nonremission cohorts were compared, respectively. All of the included patients had received tyrosine kinase inhibitor therapy before HCT and underwent HCT between 2002 and 2021. Regarding Ph-positive ALL, patients with p210 transcripts were excluded because there was concern that this group might include patients with de novo CML-BP. RESULTS: Although most of the outcomes were comparable, in patients with positive MRD at HCT, de novo CML-BP was significantly associated with superior disease-free survival (DFS) (hazard ratio [HR] 0.6, p = .0032), overall survival (HR 0.66, p = .027), and a lower risk of relapse (HR 0.48, p = .0051). In subgroup analyses, BCR::ABL1 mutation status had a significant interaction with the disease (p for interaction = .0027). De novo CML-BP seemed to be associated with superior disease-free survival in a BCR::ABL1 mutation-positive cohort, whereas this association was not observed in a mutation-negative cohort. CONCLUSIONS: Considering previous reports that showed inferior outcomes for de novo CML-BP compared to Ph-positive ALL, the data suggested that allogeneic HCT could overcome the poor prognosis of de novo CML-BP. These findings highlight the importance of distinguishing de novo CML-BP from Ph-positive ALL.

IGJ and SPATS2L immunohistochemistry sensitively and specifically identify BCR::ABL1+ and BCR::ABL1-like B-acute lymphoblastic leukaemia.

Therapeutic management and prognostication for patients with B-acute lymphoblastic leukaemia (B-ALL) require appropriate disease subclassification. BCR::ABL1-like B-ALL is unique in that it is defined by a gene expression profile similar to BCR::ABL1+ B-ALL rather than a unifying recurrent translocation. Current molecular/cytogenetic techniques to identify this subtype are expensive, not widely accessible, have long turnaround times and/or require an adequate liquid biopsy. We have studied a total of 118 B-ALL cases from three institutions in two laboratories to identify surrogates for BCR::ABL1+/like B-ALL. We report that immunoglobulin joining chain (IGJ) and spermatogenesis associated serine-rich 2-like (SPATS2L) immunohistochemistry (IHC) sensitively and specifically identify BCR::ABL1+/like B-ALL. IGJ IHC positivity has a sensitivity of 83%, a specificity of 95%, a positive predictive value (PPV) of 89% and a negative predictive value (NPV) of 90%. SPATS2L staining has similar sensitivity and NPV but lower specificity (85%) and PPV (70%). The presence of either IGJ or SPATS2L staining augments the sensitivity (93%) and NPV (95%). While these findings would need to be validated in larger studies, they suggest that IGJ and/or SPATS2L IHC may be utilized in identifying BCR::ABL1-like B-ALL or in selecting B-ALL cases for confirmatory molecular/genetic testing, particularly in resource-limited settings.

A critical review of management of allogeneic transplant-eligible adults with Ph+ acute lymphoblastic leukaemia.

Acute lymphoblastic leukaemia (ALL) in 20%-30% of adult patients contains the Philadelphia (Ph+) chromosome. Historically, Ph+ ALL denoted a markedly inferior outcome and long-term survival in the absence of an allograft was uncommon. However, the advent of targeted therapy directed against the BCR::ABL1 fusion protein with various tyrosine kinase inhibitors (TKIs) has markedly improved the prognosis, resulting in a number of treatment controversies in allograft-eligible patients. Which is the best TKI to use in induction? What is the clinical relevance of the subdivision of Ph+ ALL into multilineage vs lymphoid types? Do all patients in first morphological complete remission (CR1) after induction and consolidation with chemotherapy/TKI require an allograft? If not, what risk factors predict a poor outcome without an allograft? Can chemotherapy-free approaches, such as blinatumomab in conjunction with more potent TKIs, obviate the need for an allograft in high-risk patients? What is the best strategy to deal with persistent or emerging minimal residual disease both pre- and post-transplant? Is maintenance TKI indicated in all patients post allograft? Can salvage therapy and a subsequent allograft cure patients who relapse after not being transplanted in CR1? This manuscript reviews the latest data influencing contemporary management and discusses these controversies.

Efficacy and safety of olverembatinib in adult BCR::ABL1-positive ALL with T315I mutation or relapsed/refractory disease.

Third-generation tyrosine kinase inhibitors (TKIs) have much potential for the treatment of BCR::ABL1-positive leukaemia, particularly that harbouring the ABL1 T315I mutation. Olverembatinib (HQP1351), a novel third-generation TKI, has favourable efficacy and safety profiles in chronic myeloid leukaemia. Here, we present the clinical findings from 31 BCR::ABL1-positive acute lymphoblastic leukaemia (ALL) patients who received olverembatinib. Among the 14 patients with overt relapsed/refractory (R/R) disease (including 10 with the T315I mutation), 71.4% achieved an overall response. Of the other 17 patients with minimal residual disease (MRD)-positive ALL (including 14 with the T315I mutation), 60.0% and 47.1% achieved MRD flow negativity and complete molecular remission, respectively. With a median follow-up time of 16.3 months, the median event-free survival and overall survival were 3.9 and 8.3 months respectively, in overt R/R patients, and 11.5 and 18.4 months in MRD-positive patients. Allogeneic haematopoietic stem cell transplantation further improved outcomes among responders. The safety profile was generally manageable. This study suggests that olverembatinib-based therapy is another promising option for BCR::ABL1-positive ALL in addition to ponatinib, especially for patients with MRD-positive disease and a single T315I mutation.

The Mozart effect in chronic myeloid leukaemia.

Clinical research has not been able to establish whether the differences between first- and second-generation BCR-ABL 1 kinase inhibitors are clinically relevant with regard to outcome. In the study by Alcazer et al., a relevant difference seems to emerge-paradoxically in the absence of the drugs-as demonstrated by differences in the relapse kinetics after cessation of therapy. Commentary on: Alcazer et al. Kinetics of molecular recurrence after tyrosine kinase inhibitor cessation in chronic phase chronic myelogenous leukaemia patients. Br J Haematol 2024;204:1536-1539.

Oxidative lipid damage by naringenin selectively sensitizes chronic myeloid leukemia cell lines and patient samples to Bcr-Abl tyrosine kinase inhibitors.

Chronic myeloid leukemia (CML) treatment with Bcr-Abl tyrosine kinase inhibitors (TKIs) has significantly improved patient outcomes, yet challenges such as drug resistance and persistence of leukemic stem cells persist. This study explores the potential of naringenin, a natural flavonoid, to enhance the efficacy of Bcr-Abl TKIs in CML therapy. We showed that naringenin reduces viability of a panel of CML cell lines regardless of varying cellular origin and genetic mutations, and acts synergistically with dasatinib and ponatinib. Importantly, naringenin is effective in targeting blast crisis CML CD34+ cells by decreasing their colony formation, self-renewal and viability. Compared to CML, naringenin is significantly less effective against normal bone marrow (NBM) counterparts. In addition, naringenin significantly enhances the inhibitory effects of dasatinib in CML but not NBM CD34+ cells. Mechanism studies showed that naringenin's inhibitory effects were associated with the induction of oxidative stress and lipid damage, as evidenced by increased reactive oxygen species (ROS) and malondialdehyde (MDA) levels. Notably, naringenin upregulated genes related to mitochondrial biogenesis while downregulating antioxidant defense genes. Pretreatment with α-tocopherol, which inhibits lipid-mediated ROS production, completely abolished the ROS increase and restored cell viability, indicating that lysosomal lipid peroxidation plays a crucial role in naringenin's mechanism of action. In a CML xenograft mouse model, the combination of naringenin and dasatinib resulted in remarkably more tumor growth suppression compared to single drug alone. Importantly, this combination was well-tolerated, with no adverse effects on body weight observed. These findings suggest that naringenin, by inducing oxidative lipid damage, enhances the anti-leukemic effects of Bcr-Abl TKIs, offering a promising therapeutic strategy for CML.

Atypical BCR-ABL1 transcript in mixed phenotype acute leukemia with bone marrow necrosis.

Mixed phenotype acute leukemia (MPAL) is a type of acute leukemia in which encompasses mixed features of myeloid, T-lymphoid, and/or B-lymphoid differentiation. Philadelphia chromosome-positive (Ph+) MPAL is a rare subgroup with a poor prognosis and accounts for ＜1% of adult acute leukemia. Until now, there is still no consensus on how to best treat Ph+ MPAL. Here, we report a 62-year-old male with Ph+ (atypical e13a2 BCR-ABL1 fusion protein) MPAL. This patient presented with recurrent and intense bone pain due to bone marrow necrosis (BMN). Besides, he did not achieve a complete remission for the first two chemotherapies, until he received flumatinib combined with hyper-CVAD (B) (a dose-intensive regimen include methotrexate and cytarabine). To our knowledge, this is the first report to describe the coexistence of BMN and atypical e13a2 BCR-ABL1 transcripts in patients with MPAL. This finding will bring new understandings in the diagnosis and treatment of Ph+ MPAL.

Aleukemic Chronic Myeloid Leukemia Without Neutrophilia and Thrombocytosis: A Report From the BCR::ABL1 Pathology Group.

Chronic myeloid leukemia (CML) is characterized by leukocytosis with left-shifted neutrophilia, basophilia, eosinophilia, and variable thrombocytosis. However, extremely rare cases of patients with CML without significant leukocytosis and thrombocytosis (aleukemic phase [ALP] CML, or CML-ALP) have been reported. Due to its rarity and limited awareness, there remains a significant knowledge gap concerning the pathologic diagnosis, disease progression, and optimal patient management and outcomes. In this multi-institutional study, we investigated 31 patients with CML-ALP. Over half (54.8%) of patients had a history of or concurrent hematopoietic or nonhematopoietic malignancies. At time of diagnosis of CML-ALP, approximately 26.7% of patients exhibited neutrophilia, 56.7% had basophilia, and 13.3% showed eosinophilia. The median number of metaphases positive for t(9;22)(q34;q11.2) was 15, with a median of 38.5% of interphase nuclei positive for BCR::ABL1 by fluorescence in situ hybridization. The median BCR::ABL1 level was 26.14%. Remarkably, 14 (45.2%) patients were initially misdiagnosed or not diagnosed before karyotype or fluorescence in situ hybridization information for BCR::ABL1 became available. Twenty-five patients received tyrosine kinase inhibitors (TKIs). One patient developed blast crisis while on TKI treatment 8 months after initial diagnosis. With a median follow-up time of 46.1 months, 20 of 22 patients who received TKI therapy and had detailed follow-up information achieved complete cytogenetic remission or deeper, 15 achieved major molecular remission or deeper, and 10 achieved molecularly undetectable leukemia. In conclusion, given the frequent occurrence of prior or concurrent malignancies, aleukemic presentation, and low level of t(9;22)(q34;q11.2)/BCR::ABL1, misdiagnosis or delayed diagnosis is common among these patients. While these patients generally respond well to TKIs, rare patients may develop blastic transformation. It is therefore important for pathologists and hematologists to be aware of this highly unusual presentation of CML to ensure timely diagnosis and appropriate management.

Long non-coding RNA PXN-AS1 promotes glutamine synthetase-mediated chronic myeloid leukemia BCR::ABL1-independent resistance to Imatinib via cell cycle signaling pathway.

BACKGROUND: Chronic myeloid leukemia (CML) is a common hematological malignancy, and tyrosine kinase inhibitors (TKIs) represent the primary therapeutic approach for CML. Activation of metabolism signaling pathway has been connected with BCR::ABL1-independent TKIs resistance in CML cells. However, the specific mechanism by which metabolism signaling mediates this drug resistance remains unclear. Here, we identified one relationship between glutamine synthetase (GS) and BCR::ABL1-independent Imatinib resistance in CML cells. METHODS: GS and PXN-AS1 in bone marrow samples of CML patients with Imatinib resistance (IR) were screened and detected by whole transcriptome sequencing. GS expression was upregulated using LVs and blocked using shRNAs respectively, then GS expression, Gln content, and cell cycle progression were respectively tested. The CML IR mice model were established by tail vein injection, prognosis of CML IR mice model were evaluated by Kaplan-Meier analysis, the ratio of spleen/body weight, HE staining, and IHC. PXN-AS1 level was blocked using shRNAs, and the effects of PXN-AS1 on CML IR cells in vitro and in vivo were tested the same as GS. Several RNA-RNA tools were used to predict the potential target microRNAs binding to both GS and PXN-AS1. RNA mimics and RNA inhibitors were used to explore the mechanism through which PXN-AS1 regulates miR-635 or miR-635 regulates GS. RESULTS: GS was highly expressed in the bone marrow samples of CML patients with Imatinib resistance. In addition, the lncRNA PXN-AS1 was found to mediate GS expression and disorder cell cycle in CML IR cells via mTOR signaling pathway. PXN-AS1 regulated GS expression by binding to miR-635. Additionally, knockdown of PXN-AS1 attenuated BCR::ABL1-independent Imatinib resistance in CML cells via PXN-AS1/miR-635/GS/Gln/mTOR signaling pathway. CONCLUSIONS: Thus, PXN-AS1 promotes GS-mediated BCR::ABL1-independent Imatinib resistance in CML cells via cell cycle signaling pathway.

Higher prevalence of harbouring BCR::ABL1 in first-degree relatives of chronic myeloid leukaemia (CML) patients compared to normal population.

BACKGROUND: The role of familial influence in chronic myeloid leukaemia (CML) occurrence is less defined. Previously, we conducted a study to determine the prevalence of harbouring BCR::ABL1 in our local adult normal population (designated as StudyN). We present our current study, which investigated the prevalence of harbouring BCR::ABL1 in the normal first-degree relatives of local CML patients (designated as StudyR). We compared and discussed the prevalence of StudyR and StudyN to assess the familial influence in CML occurrence. METHODS: StudyR was a cross-sectional study using convenience sampling, recruiting first-degree relatives of local CML patients aged ≥ 18 years old without a history of haematological tumour. Real-time quantitative polymerase chain reaction standardised at the International Scale (BCR::ABL1-qPCRIS) was performed according to standard laboratory practice and the manufacturer's protocol. RESULTS: A total of 96 first-degree relatives from 41 families, with a mean age of 39 and a male-to-female ratio of 0.88, were enrolled and analysed. The median number of relatives per family was 2 (range 1 to 5). Among them, 18 (19%) were parents, 39 (41%) were siblings, and 39 (41%) were offspring of the CML patients. StudyR revealed that the prevalence of harbouring BCR::ABL1 in the first-degree relatives was 4% (4/96), which was higher than the prevalence in the local normal population from StudyN, 0.5% (1/190). All four positive relatives were Chinese, with three of them being female (p > 0.05). Their mean age was 39, compared to 45 in StudyN. The BCR::ABL1-qPCRIS levels ranged between 0.0017%IS and 0.0071%IS, similar to StudyN (0.0023%IS to 0.0032%IS) and another study (0.006%IS to 0.016%IS). CONCLUSION: Our study showed that the prevalence of harbouring BCR::ABL1 in the first-degree relatives of known CML patients was higher than the prevalence observed in the normal population. This suggests that familial influence in CML occurrence might exist but could be surpassed by other more dominant influences, such as genetic dilutional effects and protective genetic factors. The gender and ethnic association were inconsistent with CML epidemiology, suggestive of a higher familial influence in female and Chinese. Further investigation into this topic is warranted, ideally through larger studies with longer follow-up periods.

Myeloproliferative neoplasm with eosinophilia and coexisting BCR::ABL1 and PDGFRB rearrangement: favorable and rapid response to imatinib.

Here, we present a rare case of myeloproliferative neoplasms (MPN) with eosinophilia harboring both BCR::ABL1 and PDGFRB rearrangements, posing a classification dilemma. The patient exhibited clinical and laboratory features suggestive of chronic myeloid leukemia (CML) and myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions (MLN-TK), highlighting the diagnostic challenges associated with overlapping phenotypes. Despite the complexity, imatinib treatment swiftly achieved deep molecular remission, underscoring the therapeutic efficacy of tyrosine kinase inhibitors in such scenarios. Furthermore, the rapid attainment of deep remission by this patient in response to imatinib closely resembles that observed in MLN-TK patients with PDGFRB rearrangements. Further research is warranted to elucidate the underlying mechanisms driving the coexistence of multiple oncogenic rearrangements in MPNs and to optimize therapeutic strategies for these complex cases.

Spotlight on the real-world treatment of CML pts in Germany: a retrospective survey in private oncology practices.

Clinical trials in chronic myeloid leukemia (CML) are usually carried out in specialized centers whereas primary care for patients (pts) with CML is mainly provided by local oncology practices. The aim of this study was to assess treatment practices in pts with CML in the setting of private oncology practices in Germany. We collected data of 819 pts with a confirmed diagnosis (dx) of CML in 2013 or later from 43 practices. At dx, 84.2% (n=690) and 9.4% (n=77) of pts were in chronic or accelerated phase, 0.7% (n=6) had a blast crisis. Molecular monitoring was provided by EUTOS certified laboratories in 87.7% of pts. Typical BCR::ABL1 transcripts were detected in 86.6% (n=709). Molecular response was assessed after 2.8, 6.0, 9.4 and 12.9 m (mean) after start of treatment. Of the pts with available data, 11.1% did not achieve early molecular response and at 18 m, 83.7% had at least a major molecular response. 288 (35.2%) of pts switched to 2nd line (2L) treatment after a mean of 21.0 months. Reasons for 2L treatment were side effects in 43.4% and suboptimal response or failure in 31.4% of pts. 106 pts went on to third line (3L) treatment. 36.8 % of pts switched to and 92.8 % of pts still on 3L treatment achieved BCR::ABL1IS ≤1% at 12 m. In conclusion, in Germany pts with CML are routinely monitored by qPCR and good responses are achieved in the majority. Treatment changes are mainly due to adverse events rather than suboptimal responses.

Late relapse of chronic myeloid leukemia after allogeneic bone marrow transplantation points to KANSARL (KANSL1::ARL17A) alteration: a case report with insights on the molecular landscape.

Chronic myeloid leukemia is a myeloproliferative neoplasm characterized by the presence of the Philadelphia chromosome and the consequent BCR::ABL1 oncoprotein. In the era before the introduction of tyrosine kinase inhibitors (TKIs), the only potentially curative treatment was allogeneic hematopoietic stem cell transplantation (HSCT). Here, we present the case of a patient affected by CML who experienced a relapse 20 years after allogeneic HSCT. Following relapse, the patient was treated with imatinib and bosutinib, resulting in a deep molecular response and successfully discontinued treatment. Additional analysis including whole-exome sequencing and RNA sequencing provided some insights on the molecular mechanisms of the relapse: the identification of the fusion transcript KANSL1::ARL17A (KANSARL), a cancer predisposition fusion gene, could justify a condition of genomic instability which may be associated with the onset and/or probably the late relapse of his CML.

The FABD domain is critical for the oncogenicity of BCR/ABL in chronic myeloid leukaemia.

BACKGROUND: Abnormally expressed BCR/ABL protein serves as the basis for the development of chronic myeloid leukaemia (CML). The F-actin binding domain (FABD), which is a crucial region of the BCR/ABL fusion protein, is also located at the carboxyl end of the c-ABL protein and regulates the kinase activity of c-ABL. However, the precise function of this domain in BCR/ABL remains uncertain. METHODS: The FABD-deficient adenovirus vectors Ad-BCR/ABL△FABD, wild-type Ad-BCR/ABL and the control vector Adtrack were constructed, and 32D cells were infected with these adenoviruses separately. The effects of FABD deletion on the proliferation and apoptosis of 32D cells were evaluated by a CCK-8 assay, colony formation assay, flow cytometry and DAPI staining. The levels of phosphorylated BCR/ABL, p73, and their downstream signalling molecules were detected by western blot. The intracellular localization and interaction of BCR/ABL with the cytoskeleton-related protein F-actin were identified by immunofluorescence and co-IP. The effect of FABD deletion on BCR/ABL carcinogenesis in vivo was explored in CML-like mouse models. The degree of leukaemic cell infiltration was observed by Wright‒Giemsa staining and haematoxylin and eosin (HE) staining. RESULTS: We report that the loss of FABD weakened the proliferation-promoting ability of BCR/ABL, accompanied by the downregulation of BCR/ABL downstream signals. Moreover, the deletion of FABD resulted in a change in the localization of BCR/ABL from the cytoplasm to the nucleus, accompanied by an increase in cell apoptosis due to the upregulation of p73 and its downstream proapoptotic factors. Furthermore, we discovered that the absence of FABD alleviated leukaemic cell infiltration induced by BCR/ABL in mice. CONCLUSIONS: These findings reveal that the deletion of FABD diminished the carcinogenic potential of BCR/ABL both in vitro and in vivo. This study provides further insight into the function of the FABD domain in BCR/ABL.