Clinical significance of end of induction measurable residual disease monitoring in B-cell acute lymphoblastic leukemia: A single center experience.

The assessment of measurable residual disease (MRD) has emerged as a powerful prognostic tool for both pediatric and adult acute lymphoblastic leukemia (ALL). This retrospective study aimed to evaluate the prognostic relevance of the end of induction MRD in B-cell acute lymphoblastic leukemia (B ALL) patients. The study included 481 patients who underwent treatment for B ALL between August 2012 and March 2019 and had their MRD at the end of induction assessed by flow cytometry. Baseline demographic characteristics were collected from the patient's clinical records. Event free survival (EFS) and relapse free survival (RFS) were calculated using Kaplan-Meier analysis and survival estimates were compared using the log-rank test. End of induction MRD and baseline karyotype were the strongest predictors of EFS and RFS on multivariate analysis. The EFS was inversely related to the MRD value and the outcomes were similar in patients without morphological remission at the end of induction and patients in remission with MRD ≥1.0%. Even within the subgroups of ALL based on age, karyotype, BCR::ABL1 translocation and the treatment protocol, end of induction MRD positive patients had poor outcomes compared to patients who were MRD negative. The study outcome would help draft end of induction MRD-based treatment guidelines for the management of B ALL patients.

Chemotherapeutic drugs elicit stemness and metabolic alteration to mediate acquired drug-resistant phenotype in acute myeloid leukemia cell lines.

Chemotherapy resistance leading to disease relapse is a significant barrier in treating acute myeloid leukemia (AML). Metabolic adaptations have been shown to contribute to therapy resistance. However, little is known about whether specific therapies cause specific metabolic changes. We established cytarabine-resistant (AraC-R) and Arsenic trioxide-resistant (ATO-R) AML cell lines, displaying distinct cell surface expression and cytogenetic abnormalities. Transcriptomic analysis revealed a significant difference in the expression profiles of ATO-R and AraC-R cells. Geneset enrichment analysis showed AraC-R cells rely on OXPHOS, while ATO-R cells on glycolysis. ATO-R cells were also enriched for stemness gene signatures, whereas AraC-R cells were not. The mito stress and glycolytic stress tests confirmed these findings. The distinct metabolic adaptation of AraC-R cells increased sensitivity to the OXPHOS inhibitor venetoclax. Cytarabine resistance was circumvented in AraC-R cells by combining Ven and AraC. In vivo, ATO-R cells showed increased repopulating potential, leading to aggressive leukemia compared to the parental and AraC-R. Overall, our study shows that different therapies can cause different metabolic changes and that these metabolic dependencies can be used to target chemotherapy-resistant AML.

Metabolic adaptation drives arsenic trioxide resistance in acute promyelocytic leukemia.

Acquired genetic mutations can confer resistance to arsenic trioxide (ATO) in the treatment of acute promyelocytic leukemia (APL). However, such resistance-conferring mutations are rare and do not explain most disease recurrence seen in the clinic. We have generated stable ATO-resistant promyelocytic cell lines that are less sensitive to all-trans retinoic acid (ATRA) and the combination of ATO and ATRA compared with the sensitive cell line. Characterization of these resistant cell lines that were generated in-house showed significant differences in immunophenotype, drug transporter expression, anti-apoptotic protein dependence, and promyelocytic leukemia-retinoic acid receptor alpha (PML-RARA) mutation. Gene expression profiling revealed prominent dysregulation of the cellular metabolic pathways in these ATO-resistant APL cell lines. Glycolytic inhibition by 2-deoxyglucose (2-DG) was sufficient and comparable to the standard of care (ATO) in targeting the sensitive APL cell line. 2-DG was also effective in the in vivo transplantable APL mouse model; however, it did not affect the ATO-resistant cell lines. In contrast, the resistant cell lines were significantly affected by compounds targeting mitochondrial respiration when combined with ATO, irrespective of the ATO resistance-conferring genetic mutations or the pattern of their anti-apoptotic protein dependency. Our data demonstrate that combining mitocans with ATO can overcome ATO resistance. We also show that this combination has potential for treating non-M3 acute myeloid leukemia (AML) and relapsed APL. The translation of this approach in the clinic needs to be explored further.

NUDT15 c.415C>T Polymorphism Predicts 6-MP Induced Early Myelotoxicity in Patients with Acute Lymphoblastic Leukemia Undergoing Maintenance Therapy.

PURPOSE: Severe myelosuppression in patients with acute lymphoblastic leukemia (ALL) undergoing 6-MP-based maintenance therapy is attributed to TPMT gene polymorphisms, which is rare in Asian populations. This study aims to evaluate the role of selected polymorphisms in NUDT15, ITPA, and MRP4 genes in addition to TPMT in predicting 6-MP intolerance during ALL maintenance therapy. PATIENTS AND METHODS: We screened for the presence of NUDT15*3 (c.415 C>T, rs116855232); MRP4 c.2269 C>T (rs3765534), ITPA c.94 C>A (rs1127354) polymorphisms in addition to TPMT *2 (rs1800462), *3A (*3B and *3C; rs1800460 and rs1142345) in ALL patients with documented severe neutropenia (cohort-1; n=42). These polymorphisms were then screened in a prospective cohort of ALL patients (cohort-2; n=133) and compared with 6-MP dose reduction, early/late myelotoxicity. RESULTS: Nineteen (45%) patients in cohort-1 and 18 (14%) in cohort-2 had NUDT15 c.415 C>T variant while 4 (3%) patients in cohort-2 had TPMT*3C variant. Five (12%) in cohort-1 and 30 (24%) in cohort-2 had ITPA c.94 C>A variant while 9 (22%) and 15 (12%) had MRP4 c.2269 C>T variant in cohorts-1 and 2, respectively. All in cohort-1 and 36 (27%) in cohort-2 had severe myelotoxicity. Twenty-eight patients (66.6%) in cohort-1 and 40 (30%) patients in cohort-2 had significant 6-MP dose reduction. NUDT15 c.415 C>T variant explained severe myelotoxicity in 63% and 33% in cohort 1 and 2. TPMT*3C and ITPA c.94 C>A variants also explained myelotoxicity in cohort-2 (Median ANC: 376 vs 1014 mm3; p=0.04 and 776 vs 1023 mm3; p=0.04 respectively). NUDT15 c.415 C>T polymorphism explained significant myelotoxicity (507 vs 1298 mm3; p<0.0001) in the multivariate analysis as well (ß=-0.314, p<0.0001). CONCLUSION: NUDT15 c.415 C>T (15*3), TPMT*3C, as well as ITPA c.94 C>A and MRP4 c.2269 C>T polymorphisms explain hematotoxicities. Preemptive genotype-based (NUDT15*3, TPMT, ITPA c.94 C>A) 6-MP dosing could improve the outcome after maintenance therapy.

Systematic application of fluorescence in situ hybridization and immunophenotype profile for the identification of ZNF384 gene rearrangements in B cell acute lymphoblastic leukemia.

INTRODUCTION: ZNF384 gene fusions resulting from translocations with several partner genes have been described in B cell acute lymphoblastic leukemia (B-ALL) with a characteristic immunophenotype (aberrant CD13 and or CD33 with dim CD10). The prognosis of patients with this rearrangement appears to depend on the fusion partner. ZNF384 rearrangements have been identified by high through put technologies such as RNA sequencing in most of the studies published. We tested the feasibility of using the characteristic immunophenotype as a tool to screen for patients with ZNF384 translocations which can be subsequently confirmed by cytogenetic / molecular methodologies. METHODS: ZNF384 rearrangements in B-ALL patients at diagnosis with CD10 <80% and were negative for the BCR-ABL1 fusion (n = 109) were identified by fluorescence in situ hybridization followed by confirmation by reverse transcriptase-polymerase chain reaction and Sanger sequencing. The end of induction measurable residual disease evaluated by flow cytometry for these patients was obtained from patient records. RESULTS: ZNF384 translocations were identified in 14 patients and were cytogenetically cryptic in 13. EP300-ZNF384 was the most common fusion partner (n = 12), while TAF15-ZNF384 and TCF3-ZNF384 were identified in 1 patient each. End of induction MRD by flow cytometry was positive in 5 of 8 patients with the EP300-ZNF384 fusion treated at our center. CONCLUSION: Our findings show a practical approach for the identification of ZNF384 gene rearrangements by widely available technologies and indicate that the response to therapy may be heterogeneous even in this subset, which has been reported as having a favorable prognosis.

Direct Generation of Immortalized Erythroid Progenitor Cell Lines from Peripheral Blood Mononuclear Cells.

Reliable human erythroid progenitor cell (EPC) lines that can differentiate to the later stages of erythropoiesis are important cellular models for studying molecular mechanisms of human erythropoiesis in normal and pathological conditions. Two immortalized erythroid progenitor cells (iEPCs), HUDEP-2 and BEL-A, generated from CD34+ hematopoietic progenitors by the doxycycline (dox) inducible expression of human papillomavirus E6 and E7 (HEE) genes, are currently being used extensively to study transcriptional regulation of human erythropoiesis and identify novel therapeutic targets for red cell diseases. However, the generation of iEPCs from patients with red cell diseases is challenging as obtaining a sufficient number of CD34+ cells require bone marrow aspiration or their mobilization to peripheral blood using drugs. This study established a protocol for culturing early-stage EPCs from peripheral blood (PB) and their immortalization by expressing HEE genes. We generated two iEPCs, PBiEPC-1 and PBiEPC-2, from the peripheral blood mononuclear cells (PBMNCs) of two healthy donors. These cell lines showed stable doubling times with the properties of erythroid progenitors. PBiEPC-1 showed robust terminal differentiation with high enucleation efficiency, and it could be successfully gene manipulated by gene knockdown and knockout strategies with high efficiencies without affecting its differentiation. This protocol is suitable for generating a bank of iEPCs from patients with rare red cell genetic disorders for studying disease mechanisms and drug discovery.

Management of relapse in acute promyelocytic leukaemia treated with up-front arsenic trioxide-based regimens.

The standard of care for patients with acute promyelocytic leukaemia (APL) relapsing after front-line treatment with arsenic trioxide (ATO)-based regimens remains to be defined. A total of 67 patients who relapsed after receiving ATO-based up-front therapy and were also salvaged using an ATO-based regimen were evaluated. The median (range) age of patients was 28 (4-54) years. While 63/67 (94%) achieved a second molecular remission (MR) after salvage therapy, three (4·5%) died during salvage therapy. An autologous stem cell transplant (auto-SCT) was offered to all patients who achieved MR, 35/63 (55·6%) opted for auto-SCT the rest were administered an ATO + all-trans retinoic acid maintenance regimen. The mean (SD) 5-year Kaplan-Meier estimate of overall survival and event-free survival of those who received auto-SCT versus those who did not was 90·3 (5·3)% versus 58·6 (10·4)% (P = 0·004), and 87·1 (6·0)% versus 47·7 (10·3)% (P = 0·001) respectively. On multivariate analysis, failure to consolidate MR with an auto-SCT was associated with a significantly increased risk of relapse [hazard ratio (HR) 4·91, 95% confidence interval (CI) 1·56-15·41; P = 0·006]. MR induction with ATO-based regimens followed by an auto-SCT in children and young adults with relapsed APL who were treated with front-line ATO-based regimens was associated with excellent long-term survival.

Plasma imatinib levels and ABCB1 polymorphism influences early molecular response and failure-free survival in newly diagnosed chronic phase CML patients.

Achieving early molecular response (EMR) has been shown to be associated with better event free survival in patients with chronic phase chronic myeloid leukemia (CP-CML) on Imatinib therapy. We prospectively evaluated the factors influencing the 2-year failure free survival (FFS) and EMR to imatinib therapy in these patients including day29 plasma Imatinib levels, genetic variants and the gene expression of target genes in imatinib transport and biotransformation. Patients with low and intermediate Sokal score had better 2-year FFS compared to those with high Sokal Score (p = 0.02). Patients carrying ABCB1-C1236T variants had high day29 plasma imatinib levels (P = 0.005), increased EMR at 3 months (P = 0.044) and a better 2 year FFS (P = 0.003) when compared to those with wild type genotype. This translates to patients with lower ABCB1 mRNA expression having a significantly higher intracellular imatinib levels (P = 0.029). Higher day29 plasma imatinib levels was found to be strongly associated with patients achieving EMR at 3 months (P = 0.022), MMR at 12 months (P = 0.041) which essentially resulted in better 2-year FFS (p = 0.05). Also, patients who achieved EMR at 3 months, 6 months and MMR at 12 months had better FFS when compared to those who did not. This study suggests the incorporation of these variables in to the imatinib dosing algorithm as predictive biomarkers of response to Imatinib therapy.

Prognostic value of MRD monitoring based on BCR-ABL1 copy numbers in Philadelphia chromosome positive acute lymphoblastic leukemia.

Assessment of measurable residual disease (MRD) has emerged as a powerful prognostic tool in pediatric and adult acute lymphoblastic leukemia (ALL). In this single-centre retrospective study, we evaluated the prognostic relevance of MRD based on BCR-ABL1 copy numbers in Ph + ALL patients between 2006 and 2018. Molecular responses were evaluated at 3, 6, 9 and 12 months after the initiation of treatment. Patients who had their MRD assessed at three or more time points were categorized into MRD good risk or poor risk based on BCR-ABL1/ABL1 copy number ratio. MRD positive patients consistently showed a trend toward poor survival and on multivariate analysis, MRD poor risk patients had adverse outcomes when compared to MRD good risk patients in terms of overall (OS; p = .031) and event-free (EFS; p < .001) survival. In conclusion, molecular MRD based on BCR-ABL1 copy number ratio is an ideal prognostic indicator in Ph + ALL patients undergoing treatment.

A phase II study evaluating the role of bortezomib in the management of relapsed acute promyelocytic leukemia treated upfront with arsenic trioxide.

The standard-of-care for patients with acute promyelocytic leukemia (APL) relapsing after upfront arsenic trioxide (ATO) therapy is not defined. The present study was undertaken to evaluate the safety of addition of bortezomib to ATO in the treatment of relapsed APL based on our previously reported preclinical data demonstrating synergy between these agents. This was an open label, nonrandomized, phase II, single-center study. We enrolled 22 consecutive patients with relapsed APL. The median age was 26.5 years (interquartile range 17.5 to 41.5). The median time from initial diagnosis to relapse was 23.1 months (interquartile range 15.6 to 43.8). All patients achieved hematological remission at a median time of 45 days (range 40-63). Nineteen patients were in molecular remission at the end of induction. Grade 3 adverse events occurred in eight instances with one patient requiring discontinuation of therapy for grade 3 neuropathy. Twelve (54.5%) patients underwent autologous transplantation (auto-SCT) in molecular remission while the rest opted for maintenance therapy. The median follow-up was 48 months (range 28-56.3). Of the patients undergoing auto-SCT, all except one was alive and relapse free at last follow-up. Of the patients who opted for maintenance therapy, three developed a second relapse. For treatment of APL relapsing after upfront ATO therapy, addition of bortezomib to a standard ATO-based salvage regimen is safe and effective. This trial was registered at www.clinicaltrials.gov as NCT01950611.

Resource utilization and cost effectiveness of treating acute promyelocytic leukaemia using generic arsenic trioxide.

Arsenic trioxide (ATO)-based regimens are the standard of care for treating acute promyelocytic leukaemia (APL) and have replaced chemotherapy-based approaches. However, the cost of "patented" ATO is prohibitive because of patent rights. "Generic" ATO has been used in a few countries, but its implications for health resource utilization (HRU) and cost of treatment are unknown. We hypothesized that treating APL patients using generic ATO (APL-ATO) will be cost effective compared to the chemotherapy-based regimen (APL-CT). In a single-centre retrospective study, we used a bottom-up costing method to compare the direct medical cost of treatment and HRU between APL-ATO and APL-CT. These costs and the survival and relapse probabilities were imputed in a three-state Markov decision model to estimate the cost effectiveness of APL-ATO compared to APL-CT. The mean cost of treatment for APL-ATO (n = 30, $8500 ± 2078) was significantly less than for APL-CT (n = 30, $22 600 ± 5528) (P < 0·001). APL-ATO reduced hospitalization, antibiotic and antifungal usage (P < 0·001). In the Markov model, five-year treatment costs were significantly lower for APL-ATO ($11 131) than for APL-CT ($17 926) (P < 0·001). Treatment cost and health resource utilization were significantly lower for generic ATO-treated APL patients compared to the chemotherapy-based regimen.

Adult Acute Lymphoblastic Leukemia: Limitations of Intensification of Therapy in a Developing Country.

Purpose Limited data exist on intensifying chemotherapy regimens in the treatment of adult acute lymphoblastic leukemia (ALL) outside the setting of a clinical trial. Materials and Methods Retrospectively, data from 507 consecutive adults (age ≥ 15 years) with a diagnosis of ALL treated at our center were analyzed. Standard-risk (SR) patients were offered treatment with a modified German Multicenter ALL (GMALL) regimen, whereas high-risk (HR) patients were offered intensification of therapy with hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone (HCVAD). Because of resource constraints, a proportion of HR patients opted to receive the same treatment regimen as used for SR patients. Results There were 344 SR patients (67.8%) and 163 HR patients (32.2%) at diagnosis. Among the HR patients, 53 (32.5%) opted to receive intensification with the HCVAD regimen. The SR cohort showed a superior 5-year event-free survival rate compared with the HR cohort (47.3% v 23.6%, respectively; P < .001). Within the HR subgroup, there was no statistically significant difference in overall survival or event-free survival between patients who received the modified GMALL regimen (n = 59) and patients who received HCVAD (n = 53). Conclusion Intensified therapy in the HR subset was associated with a significant increase in early treatment-related mortality and cost of treatment. A modified GMALL regimen was found to be cost-effective with clinical outcomes comparable to those achieved with more intensive regimens.

Arsenic Trioxide Enhances the NK Cell Cytotoxicity Against Acute Promyelocytic Leukemia While Simultaneously Inhibiting Its Bio-Genesis.

Natural killer cells (NK) contribute significantly to eradication of cancer cells, and there is increased interest in strategies to enhance it's efficacy. Therapeutic agents used in the treatment of cancer can impact the immune system in a quantitative and qualitative manner. In this study, we evaluated the impact of arsenic trioxide (ATO) used in the management of acute promyelocytic leukemia (APL) on NK cell reconstitution and function. In patients with APL treated with single agent ATO, there was a significant delay in the reconstitution of circulating NK cells to reach median normal levels from the time of diagnosis (655 days for NK cells vs 145 and 265 days for T cells and B cells, respectively). In vitro experiments demonstrated that ATO significantly reduced the CD34 hematopoietic stem cell (HSC) differentiation to NK cells. Additional experimental data demonstrate that CD34+ sorted cells when exposed to ATO lead to a significant decrease in the expression of IKZF2, ETS1, and TOX transcription factors involved in NK cell differentiation and maturation. In contrast, exposure of NK cells and leukemic cells to low doses of ATO modulates NK cell receptors and malignant cell ligand profile in a direction that enhances NK cell mediated cytolytic activity. We have demonstrated that NK cytolytic activity toward NB4 cell line when exposed to ATO was significantly higher when compared with controls. We also validated this beneficial effect in a mouse model of APL were the median survival with ATO alone and ATO + NK was 44 days (range: 33-46) vs 54 days (range: 52-75). In conclusion, ATO has a differential quantitative and qualitative effect on NK cell activity. This information can potentially be exploited in the management of leukemia.

RNA expression of genes involved in cytarabine metabolism and transport predicts cytarabine response in acute myeloid leukemia.

BACKGROUND: Variation in terms of outcome and toxic side effects of treatment exists among acute myeloid leukemia (AML) patients on chemotherapy with cytarabine (Ara-C) and daunorubicin (Dnr). Candidate Ara-C metabolizing gene expression in primary AML cells is proposed to account for this variation. METHODS: Ex vivo Ara-C sensitivity was determined in primary AML samples using MTT assay. mRNA expression of candidate Ara-C metabolizing genes were evaluated by RQPCR analysis. Global gene expression profiling was carried out for identifying differentially expressed genes between exvivo Ara-C sensitive and resistant samples. RESULTS: Wide interindividual variations in ex vivo Ara-C cytotoxicity were observed among samples from patients with AML and were stratified into sensitive, intermediately sensitive and resistant, based on IC50 values obtained by MTT assay. RNA expression of deoxycytidine kinase (DCK), human equilibrative nucleoside transporter-1 (ENT1) and ribonucleotide reductase M1 (RRM1) were significantly higher and cytidine deaminase (CDA) was significantly lower in ex vivo Ara-C sensitive samples. Higher DCK and RRM1 expression in AML patient's blast correlated with better DFS. Ara-C resistance index (RI), a mathematically derived quotient was proposed based on candidate gene expression pattern. Ara-C ex vivo sensitive samples were found to have significantly lower RI compared with resistant as well as samples from patients presenting with relapse. Patients with low RI supposedly highly sensitive to Ara-C were found to have higher incidence of induction death (p = 0.002; RR: 4.35 [95% CI: 1.69-11.22]). Global gene expression profiling undertaken to find out additional contributors of Ara-C resistance identified many apoptosis as well as metabolic pathway genes to be differentially expressed between Ara-C resistant and sensitive samples. CONCLUSION: This study highlights the importance of evaluating expression of candidate Ara-C metabolizing genes in predicting ex vivo drug response as well as treatment outcome. RI could be a predictor of ex vivo Ara-C response irrespective of cytogenetic and molecular risk groups and a potential biomarker for AML treatment outcome and toxicity. Original submitted 22 December 2014; Revision submitted 9 April 2015.

Comparison of newly diagnosed and relapsed patients with acute promyelocytic leukemia treated with arsenic trioxide: insight into mechanisms of resistance.

There is limited data on the clinical, cellular and molecular changes in relapsed acute promyeloytic leukemia (RAPL) in comparison with newly diagnosed cases (NAPL). We undertook a prospective study to compare NAPL and RAPL patients treated with arsenic trioxide (ATO) based regimens. 98 NAPL and 28 RAPL were enrolled in this study. RAPL patients had a significantly lower WBC count and higher platelet count at diagnosis. IC bleeds was significantly lower in RAPL cases (P=0.022). The ability of malignant promyelocytes to concentrate ATO intracellularly and their in-vitro IC50 to ATO was not significantly different between the two groups. Targeted NGS revealed PML B2 domain mutations in 4 (15.38%) of the RAPL subset and none were associated with secondary resistance to ATO. A microarray GEP revealed 1744 genes were 2 fold and above differentially expressed between the two groups. The most prominent differentially regulated pathways were cell adhesion (n=92), cell survival (n=50), immune regulation (n=74) and stem cell regulation (n=51). Consistent with the GEP data, immunophenotyping revealed significantly increased CD34 expression (P=0.001) in RAPL cases and there was in-vitro evidence of significant microenvironment mediated innate resistance (EM-DR) to ATO. Resistance and relapse following treatment with ATO is probably multi-factorial, mutations in PML B2 domain while seen only in RAPL may not be the major clinically relevant cause of subsequent relapses. In RAPL additional factors such as expansion of the leukemia initiating compartment along with EM-DR may contribute significantly to relapse following treatment with ATO based regimens.