Alterations in the FMS-like tyrosine kinase 3 (FLT3) gene are the most frequent driver mutations in acute myeloid leukaemia (AML), linked to a high risk of relapse in patients with internal tandem duplications (FLT3-ITD). Tyrosine kinase inhibitors (TKIs) targeting the FLT3 protein are approved for clinical use, yet resistance often emerges. This resistance is mainly seen following the acquisition of additional point mutations in the tyrosine kinase domain (TKD), resulting in a double mutant FLT3-ITD/TKD, which sustains cell signalling and survival despite the presence of FLT3 inhibitors. Here, we developed a FLT3-mutant AML model with adaptive resistance to type II TKIs, sorafenib, and quizartinib by in vitro drug selection. Through global multiomic profiling, we identified upregulation of proteins involved in reactive oxygen species (ROS) production, particularly NADPH-oxidases, driving cellular 'ROS-addiction', with resistant cells relying on ROS for survival, and genome fidelity preserved by ATM-driven DNA repair. Transcriptomic analysis of adult and paediatric AML (pAML) patients identified high ATM expression as a biomarker for shorter median overall survival in both the de novo and relapsed settings. Inhibition of ATM with clinically relevant therapy WSD-0628 effectively killed TKI- and chemotherapy-resistant AML cells in vitro and significantly extended the survival of mice with sorafenib- and quizartinib-resistant FLT3-ITD AML in vivo. We propose a new treatment strategy to improve survival of patients who develop resistance to sorafenib and quizartinib, as well as relapsed and refractory pAML, exploiting resistance mechanisms to precision therapies and cell-intrinsic features of high-risk cases, highlighting a clinically relevant salvage strategy. ### Competing Interest Statement The authors have declared no competing interest.

In solid tumours, high expression of the glycolytic enzyme, α-enolase (ENO1), predicts for poor patient overall survival (OS), and circulating autoantibodies to ENO1 correlate positively with diagnosis and negatively with advanced disease. Although ENO1 is one of the most highly expressed genes in acute myeloid leukaemia (AML), its potential role as a biomarker in AML or its precursor, myelodysplastic neoplasms (MDS), has not been investigated. A meta-analysis of nine AML online datasets (n = 1419 patients) revealed that high ENO1 expression predicts for poor OS (HR = 1.22, 95% CI: 1.10–1.34, p < 0.001). Additionally, when compared to AML in remission (n = 5), ENO1 protein detected by immunohistochemistry was significantly higher at diagnosis in bone marrow from both AML (n = 5, p < 0.01) and MDS patients (n = 12, p < 0.05), and did not correlate with percentage of blasts (r = 0.28, p = 0.21). AML patients (n = 34) had lower circulating levels of ENO1 autoantibodies detected by ELISA compared to 26 MDS and 18 controls (p = 0.003). However, there was no difference in OS between AML patients with high vs. low levels of anti-ENO1 autoantibodies (p = 0.77). BM immunostaining for ENO1 and patient monitoring of anti-ENO1 autoantibody levels may be useful biomarkers for MDS and AML.

AbstractIntroductionVariants of uncertain significance (VUS) are commonly reported in cancer with the widespread adoption of diagnostic massive parallel sequencing. The rate of reclassification of VUS in patients with haematological malignancy is not known and we evaluated this retrospectively. We also investigated whether re‐evaluating VUS in 12–24 months or greater than 24 months post‐initial classification was significant.MethodA retrospective audit of patients with haematological malignancies referred to the Molecular Medicine Department at the John Hunter Hospital in Newcastle, Australia between September 2018 and December 2021. Data was analysed for VUS, which was then re‐analysed in standard software using current somatic variant guidelines. Proportions of VUS at baseline were compared to post‐re‐analysis.ResultsThe most common diagnoses in the patient cohort (n = 944) were acute myelogenous leukaemia (41%), myelodysplastic syndrome (31%), and chronic myelomonocytic leukaemia (7%). A total of 210 VUS were re‐analysed. The most common VUS were in the TET2 (20%), RUNX1 (10%) and DNMT3A (9%) genes. A total of 103 were re‐analysed at 24–39 months post‐initial classification and 107 variants were re‐analysed between 12 and 24 months post‐initial classification. Of these, 33 (16%) of VUS were re‐classified at 24–39 months and 12 (11%) were re‐classified at 12–24 months post‐initial classification. The most common variants that were re‐classified in both groups were CSF3R (32%), TET2 (29%), ASXL1 (11%) and ZRSR2 (11%).ConclusionThis study on reclassification of VUS in blood cancers demonstrated that one in seven VUS were re‐classified 12 months post initial classification. This can inform practice guidelines and potentially impact the prognosis, diagnosis and treatment of haematological malignancies.

Hypomethylating agents are the most widely used upfront therapy for patients with myelodysplastic syndrome (MDS) who are not suitable for hematopoietic stem cell transplantation. In Australia, azacitidine was, until recently, the only approved and subsidized treatment for patients with intermediate-2 and high-risk MDS, chronic myelomonocytic leukemia, and low blast acute myeloid leukemia. We analyzed prescription data to evaluate the real-world persistence and overall survival (OS) of patients prescribed azacitidine for the first time in Australia. A retrospective cohort analysis of patients who had been prescribed Pharmaceutical Benefits Scheme (PBS)-listed azacitidine for the first time, between January 2016 and April 2021, was conducted using the PBS 10% dataset. Treatment persistence and OS were estimated using Kaplan-Meier methods. The impact of the number of treatment cycles and treatment adherence on OS was also estimated. There were 351 patients in the PBS 10% dataset who initiated treatment with azacitidine. The average age (standard deviation [SD]) at azacitidine initiation was 71.9 (11.1) years and the average number (SD) of azacitidine prescriptions was 5.6 (0.2). The median persistence on azacitidine was 15.6 months, and the OS was 13.4 months. The median OS for patients who had six or more cycles of azacitidine treatment was greater compared to patients who had five or less cycles of treatment. The data from this real-world study illustrate the unmet medical needs of patients with MDS treated with azacitidine in Australia. The majority of patients are not treated with the optimal number of cycles of azacitidine, which is negatively correlated with patient outcomes.

INTRODUCTION:Acute myeloid leukemia (AML) is an aggressive and poor-prognosis blood cancer. Despite a low mutation burden compared to other cancers, AML is heterogenous and identifying robust therapeutic targets has been difficult. Genomic profiling has greatly advanced our understanding of AML, and has revealed targets for AML therapy. However, only 50% of AML patients have gene mutations that are currently druggable, and relapse rates remain high. The addition of proteomic profiling is emerging to address these challenges. AREAS COVERED:Using references collected through Pubmed, we review recent studies that have combined genomic and proteomic profiling (i.e. proteogenomic profiling), as well as studies that have additionally integrated other omics approaches, such as phosphoproteomics. We highlight how proteogenomic profiling promises to deconvolve the cellular pathways driving leukemogenesis, uncover novel therapeutic targets, and identify biomarkers of response to novel and existing therapies. EXPERT OPINION:Proteogenomic profiling is providing unparalleled insight into AML, and is beginning to identify robust biomarkers. Standardization of workflows will be required before mass spectrometry-based proteomic assays can be integrated into routine clinical use. However, the demonstrated ability to adapt signatures into biomarker panels that can be assayed by existing clinical workflows is enabling current clinical translation.

Mutations in the type III receptor tyrosine kinase FLT3 are frequent in patients with acute myeloid leukemia (AML) and are associated with a poor prognosis. AML is characterized by the overproduction of reactive oxygen species (ROS), which can induce cysteine oxidation in redox-sensitive signaling proteins. Here, we sought to characterize the specific pathways affected by ROS in AML by assessing oncogenic signaling in primary AML samples. The oxidation or phosphorylation of signaling proteins that mediate growth and proliferation was increased in samples from patient subtypes with FLT3 mutations. These samples also showed increases in the oxidation of proteins in the ROS-producing Rac/NADPH oxidase-2 (NOX2) complex. Inhibition of NOX2 increased the apoptosis of FLT3-mutant AML cells in response to FLT3 inhibitors. NOX2 inhibition also reduced the phosphorylation and cysteine oxidation of FLT3 in patient-derived xenograft mouse models, suggesting that decreased oxidative stress reduces the oncogenic signaling of FLT3. In mice grafted with FLT3 mutant AML cells, treatment with a NOX2 inhibitor reduced the number of circulating cancer cells, and combining FLT3 and NOX2 inhibitors increased survival to a greater extent than either treatment alone. Together, these data raise the possibility that combining NOX2 and FLT3 inhibitors could improve the treatment of FLT3 mutant AML.

FLT3-mutations are diagnosed in 25-30% of patients with acute myeloid leukemia (AML) and are associated with a poor prognosis. AML is associated with the overproduction of reactive oxygen species (ROS), which drives genomic instability through the oxidation of DNA bases, promoting clonal evolution, treatment resistance and poor outcomes. ROS are also important second messengers, triggering cysteine oxidation in redox sensitive signaling proteins, however, the specific pathways influenced by ROS in AML remain enigmatic. Here we have surveyed the posttranslational architecture of primary AML patient samples and assessed oncogenic second messenger signaling. Signaling proteins responsible for growth and proliferation were differentially oxidized and phosphorylated between patient subtypes either harboring recuring mutation in FLT3 compared to patients expressing the wildtype-FLT3 receptor, particularly those mapping to the Src family kinases (SFKs). Patients harboring FLT3-mutations also showed increased oxidative posttranslational modifications in the GTPase Rac activated-NADPH oxidase-2 (NOX2) complex to drive autocratic ROS production. Pharmacological and molecular inhibition of NOX2 was cytotoxic specifically to FLT3-mutant AMLs, and reduced phosphorylation of the critical hematopoietic transcription factor STAT5 and MAPK/ERK to synergistically increase sensitivity to FLT3-inhibitors. NOX2 inhibition also reduced phosphorylation and cysteine oxidation of FLT3 in patient derived xenograft mouse models in vivo , highlighting an important link between oxidative stress and oncogenic signaling. Together, these data raise the promising possibility of targeting NOX2 in combination with FLT3-inhibitors to improve treatment of FLT3-mutant AML. One Sentence Summary FLT3-precision therapies have entered the clinic for AML however, their durability is limited. Here we identify the Rac-NOX2 complex as the major driver of redox second messenger signaling in FLT3-mutant AML. Molecular and pharmacological inhibition of NOX2 decreased FLT3, STAT5 and MEK/ERK signaling to delay leukemia progression, and synergistically combined with FLT3 inhibitors.

Acute lymphoblastic leukaemia (ALL) is the most common cancer diagnosed in children and adolescents. Approximately 70% of patients survive >5-years following diagnosis, however, for those that fail upfront therapies, survival is poor. Reactive oxygen species (ROS) are elevated in a range of cancers and are emerging as significant contributors to the leukaemogenesis of ALL. ROS modulate the function of signalling proteins through oxidation of cysteine residues, as well as promote genomic instability by damaging DNA, to promote chemotherapy resistance. Current therapeutic approaches exploit the pro-oxidant intracellular environment of malignant B and T lymphoblasts to cause irreversible DNA damage and cell death, however these strategies impact normal haematopoiesis and lead to long lasting side-effects. Therapies suppressing ROS production, especially those targeting ROS producing enzymes such as the NADPH oxidases (NOXs), are emerging alternatives to treat cancers and may be exploited to improve the ALL treatment. Here, we discuss the roles that ROS play in normal haematopoiesis and in ALL. We explore the molecular mechanisms underpinning overproduction of ROS in ALL, and their roles in disease progression and drug resistance. Finally, we examine strategies to target ROS production, with a specific focus on the NOX enzymes, to improve the treatment of ALL.

*These authors contributed equally to this work Background:Acute Myeloid Leukaemia (AML) is the most common and aggressive form of acute leukaemia, with a 5-year survival rate of just 24%. Activating mutations in the receptor tyrosine kinase FLT3 are the most common driver mutations in AML (25-30% of patients). Inhibiting the FLT3 receptor as a mono-therapeutic strategy in AML has proven difficult however, due to the development of treatment resistance and relapse. In order to identify improved therapeutic targets, the oncogenic signalling pathways downstream of mutant FLT3 require characterisation. Methods:Quantitative, label-based phosphoproteomics was performed on primary blasts from 7 AML patients (4 mutant-FLT3, 3 wildtype-FLT3). Differentially phosphorylated pathways were identified using Ingenuity Pathway Analysis, and kinase activation was assessed by kinase substrate enrichment analysis. Validation of results was performed using targeted mass spectrometry. Proliferation, apoptosis, and cell cycle assays were used to assess drug toxicity; drug synergy was evaluated using Chou-Talalay and Webb analyses. Results:Analysis of differentially expressed phosphoproteins in mutant-FLT3 compared to wildtype-FLT3 AML patient blasts revealed dysregulation of DNA repair pathways. Specifically, mutant-FLT3 samples displayed increased phosphorylation of proteins within the error-prone Non-Homologous End Joining (NHEJ) repair pathway, indicating NHEJ pathway activation. Kinase enrichment analysis predicted increased activity of the NHEJ core kinase, DNA-dependent protein kinase (DNA-PK), in mutant-FLT3 samples. Accordingly, proliferation assays revealed that mutant-FLT3 cell lines were sensitive to inhibition of DNA-PK. FLT3-inhibitor treatment reduced DNA-PK phosphorylation in mutant-FLT3 cells, suggesting that activation of DNA-PK is downstream of FLT3 activation. Inhibition of DNA-PK kinase activity combined with FLT3 inhibitors led to synergistic induction of cell death, selectively in mutant-FLT3 cell lines. DNA-PK inhibitors combined with FLT3 inhibitors also co-operatively induced cell death in mutant-FLT3 primary AML patient samplesex vivo, and significantly prolonged survival compared to either monotherapy in a human AML xenograft mouse model. Conclusions:Mutant-FLT3 AML is associated with activation of the error-prone NHEJ repair pathway, which may contribute to genomic instability. Targeting the NHEJ kinase, DNA-PK, in combination with FLT3 inhibitors has the potential to improve outcomes for this poor-prognosis AML subtype. Disclosures Enjeti: Bayer:Speakers Bureau;AbbVie:Membership on an entity's Board of Directors or advisory committees;Alexion:Speakers Bureau;Novartis:Membership on an entity's Board of Directors or advisory committees;Astellas:Membership on an entity's Board of Directors or advisory committees;Sanofi:Speakers Bureau.

Acute myeloid leukaemia (AML) is an aggressive haematological malignancy with a poor overall survival. Reactive oxygen species (ROS) have been shown to be elevated in a wide range of cancers including AML. Whilst previously thought to be mere by-products of cellular metabolism, it is now clear that ROS modulate the function of signalling proteins through oxidation of critical cysteine residues. In this way, ROS have been shown to regulate normal haematopoiesis as well as promote leukaemogenesis in AML. In addition, ROS promote genomic instability by damaging DNA, which promotes chemotherapy resistance. The source of ROS in AML appears to be derived from members of the "NOX family" of NADPH oxidases. Most studies link NOX-derived ROS to activating mutations in the Fms-like tyrosine kinase 3 (FLT3) and Ras-related C3 botulinum toxin substrate (Ras). Targeting ROS through either ROS induction or ROS inhibition provides a novel therapeutic target in AML. In this review, we summarise the role of ROS in normal haematopoiesis and in AML. We also explore the current treatments that modulate ROS levels in AML and discuss emerging drug targets based on pre-clinical work.

Acute Myeloid Leukaemia is a devastating disease that continues to have a poor outcome for the majority of patients. In recent years, however, a number of drugs have received FDA approval, following on from successful clinical trial results. This parallels the characterization of the molecular landscape of Acute Myeloid Leukaemia (AML) over the last decade, which has led to the development of drugs targeting newly identified recurring mutations. In addition, basic biological research into the pathobiology of AML has identified aberrant programmed cell death pathways in AML. Following on from successful outcomes in lymphoid malignancies, drugs targeting the B Cell Lymphoma 2 (BCL-2) family of anti-apoptotic proteins have been explored in AML. In this review, we will outline the preclinical and clinical work to date supporting the role of drugs targeting BCL-2, with Venetoclax being the most advanced to date. We will also highlight rationale combinations using Venetoclax, ongoing clinical trials and biomarkers of response identified from the early phase clinical trials performed.

A 20-year-old man was admitted to a regional hospital with fevers, rigors, anorexia and left upper quadrant pain. It was his fourth presentation to the emergency department in the preceding 10 days. On the first two presentations, he had been sent home with a provisional diagnosis of renal colic. After review by his general practitioner, he had undergone outpatient imaging that identified filling defects in the pulmonary arteries of his left lower lobe, which were reported as being consistent with pulmonary emboli. In addition, two hypodense splenic lesions were identified, as well as collapse and possible consolidation of the left lower lobe. His GP had referred him to the emergency department for further review (his third presentation), after which he had commenced therapeutic anticoagulation for a presumed diagnosis of pulmonary emboli. The patient's history was notable for a self-limiting episode of gastroenteritis 6 weeks before his initial presentation, with sick family contacts. On his fourth presentation, he described progressive left upper quadrant and flank pain over the preceding 10 days, with intermittent fevers and rigors. He had no other focal infective symptoms on review. On examination, he was found to have a fever (temperature, 39.3°C), sinus tachycardia (heart rate, 154 beats/min), tachypnoea (respiratory rate, 28 breaths/min), hypotension (blood pressure, 97/66 mmHg), decreased breath sounds at the left base of his lung fields and mild left upper quadrant tenderness. Investigations showed a white cell count of 16 × 109/L (reference interval [RI], 4.0–11.0 × 109/L), with a predominant neutrophilia (neutrophils, 14 × 109/L [RI, 2.0–7.0 × 109/L]). Results of his liver function tests and electrolyte, urea and creatinine levels were all within reference intervals. A computed tomography scan of the chest and upper abdomen again showed two low-density lesions of unclear aetiology in the spleen, as well as a left-sided pleural effusion and collapse of the left lower lobe. Given the possibility that the hypodense splenic lesions represented septic emboli from a cardiac source, the patient was treated empirically with benzylpenicillin, flucloxacillin and gentamicin for a provisional diagnosis of endocarditis. However, a transthoracic echocardiogram performed the next day did not support this diagnosis, with no abnormalities detected. Beyond the radiological findings described, there were no other clinical grounds to support a diagnosis of endocarditis. Blood cultures taken on Day 1 of admission were positive for gram-negative bacilli, with confirmation of a non-typhoidal Salmonella species (later confirmed as Salmonella Virchow) the following day. This allowed targeted antibiotic therapy, once susceptibilities were known, with ampicillin (2 g every 6 hours). Cultures of stool samples taken at admission were positive for the same isolate, consistent with the patient's self-limiting episode of gastroenteritis 6 weeks before his first presentation. Magnetic resonance imaging of the abdomen suggested that the two splenic lesions were likely to represent abscesses in this clinical context (Figure). Given our patient's ongoing sepsis, a decision was made to perform a laparoscopic splenectomy for source control on Day 5 of admission. Surgical specimens tested positive for Salmonella Virchow. Histopathological testing identified cystic lymphangiomas of the spleen. Despite problems with postoperative pain and a prolonged ileus, the patient made a full recovery. He received appropriate post-splenectomy vaccinations, along with a total of 2 weeks' intravenous ampicillin, followed by a 2-week course of oral amoxicillin. Non-typhoidal salmonellae are common foodborne pathogens. In Australia, they are the second most frequent bacterial isolates identified in cases of acute gastroenteritis, after Campylobacter jejuni. In 2010, OzFoodNet sites reported 11 992 cases of Salmonella infection, a rate of 53.7 cases per 100 000.1 Salmonella Virchow was the third most common isolate, after Salmonella Typhimurium and Salmonella Enteritidis. Non-typhoidal Salmonella infection outbreaks are most commonly associated with consumption of poultry and eggs, but have also been linked to fresh produce and, increasingly, contact with pet reptiles.2 Up to 8% of patients with gastroenteritis secondary to non-typhoidal Salmonella infection develop bacteraemia.3 Risk factors for invasive infection include extremes of age, immunosuppressed states, malignancy, HIV infection and use of tumour necrosis factor-blocking medication.4 Our case is unusual in that bacteraemia occurred in an otherwise immunocompetent host. Extraintestinal focal infections have been reported to occur in 5% to 10% of patients with non-typhoidal Salmonella bacteraemia.3 The best recognised complications are endovascular infections, most commonly involving the aorta, that result from seeding of atherosclerotic plaques and aneurysms.5 However, focal infections of almost all organ systems have been reported. Splenic abscesses are most commonly seen as a complication of infective endocarditis, occurring in about 5% of patients.6,7 They are also found as a rare complication of non-typhoidal Salmonella infections. In one case series of 49 patients from southern Taiwan, Salmonella species were the third most common pathogens isolated from splenic abscesses, accounting for 11% of cases.8 The most common presentations among the 49 patients with splenic abscesses were fever (47 patients), abdominal pain confined to the left upper quadrant (33 patients), left pleural effusion and splenomegaly (both 27 patients), all of which were present in our patient. About 50% of patients presenting with splenic abscesses have pre-existing anatomical abnormalities.9 The cystic lymphangiomas identified in our patient almost certainly predisposed him to developing splenic abscesses. According to the literature, the mainstay of treatment for splenic abscesses is splenectomy. Data from 287 cases published between 1987 and 1995 suggested that non-operative management, which included invasive treatment with percutaneous aspiration and catheter drainage, had a success rate of less than 65%.10 The same series suggested that antimicrobial therapy alone had a success rate of less than 50%. Salvage splenectomy, however, was not shown to result in increased mortality. Another retrospective study of 51 patients in a tertiary hospital between 1998 and 2003 reported survival rates of 48% with antimicrobial therapy alone, 45% with pigtail catheter insertion and drainage in addition to antimicrobial therapy, and 100% with splenectomy and antimicrobial therapy.11 These results may be influenced by selection bias but do suggest improved outcomes with splenectomy over less invasive strategies. Splenic abscesses are a rare but serious complication of non-typhoidal Salmonella bacteraemia that may occur in otherwise immunocompetent individuals. Splenic abscesses should be suspected in patients with unexplained fevers and left upper quadrant pain. The mainstay of treatment is splenectomy with appropriate antimicrobial therapy. A: Axial T2-weighted magnetic resonance image (MRI) of the abdomen, without contrast, showing an abscess in the inferior pole of the spleen (circle). B: Saggital T2-weighted MRI of the abdomen, without contrast, showing two splenic abscesses (circles).