Changes in chronic myeloid leukemia treatment modalities and outcomes after introduction of second-generation tyrosine kinase inhibitors as first-line therapy: a multi-institutional retrospective study by the CML Cooperative Study Group

This study investigated changes in treatment modalities and outcomes of chronic myeloid leukemia in the chronic phase (CP-CML) after the approval of second-generation tyrosine kinase inhibitors (2G-TKIs) for first-line therapy. Patients were grouped into those who underwent TKI therapy up to December 2010 (imatinib era group, n = 185) and after January 2011 (2G-TKI era group, n = 425). All patients in the imatinib era group were initially treated with imatinib, whereas patients in the 2G-TKI era group were mostly treated with dasatinib (55%) or nilotinib (36%). However, outcomes including progression-free survival, overall survival, and CML-related death (CRD) did not differ significantly between groups. When stratified by risk scores, the prognostic performance of the ELTS score was superior to that of the Sokal score. Even though both scoring systems predicted CRD in the imatinib era, only the ELTS score predicted CRD in the 2G-TKI era. Notably, the outcome of patients classified as high-risk by ELTS score was more favorable in the 2G-TKI era group than in the imatinib era group. Thus, expanding treatment options may have improved patient outcomes in CP-CML, particularly in patients classified as high-risk by ELTS score.

RUNX1::RUNX1T1 Acute Myeloid Leukemia Cytogenetically Showing t(6;8)(p23;q22)

Runt-related transcription factor 1 (RUNX1)::RUNX1 partner transcriptional co-repressor 1 (RUNX1T1) acute myeloid leukemia (AML) is a subtype of acute leukemia primarily classified as French American British M2. RUNX1::RUNX1T1 transcript is formed by a reciprocal translocation between chromosomes 8q22 and 21q22. However, we encountered a case of AML that showed molecular positivity for RUNX1::RUNX1T1 fusion transcript but exhibited cytogenetically atypical translocation t(6;8). Fluorescence in situ hybridization (FISH) analysis, in combination with G-banding, clarified the three-way translocation t(6;21;8)(p25;q22;q22), which was partially cryptic. The case emphasizes the importance of employing molecular analysis alongside cytogenetics to determine disease subtypes in patients with acute leukemia.

An observational study of once-weekly carfilzomib in patients with multiple myeloma in Japan (Weekly-CAR study)

Background: The ARROW study demonstrated that once-weekly carfilzomib and dexamethasone (wKd) therapy significantly prolonged progression-free survival compared with twice-weekly carfilzomib and dexamethasone therapy in relapsed or refractory multiple myeloma patients. Aim: To describe the treatment patterns, effectiveness and safety of wKd therapy in real-world settings in Japan. Methods: We investigated data from the medical records of 126 Japanese patients with relapsed or refractory multiple myeloma. Results: The overall response rate was 66.3%. The median progression-free survival was 9.5 months. The incidence of treatment-emergent adverse events of any grade and grade ≥3 were 45.8 and 20.8%, respectively. Conclusion: There were no new or unexpected safety signals in this study. This study demonstrated the effectiveness and safety profiles of wKd therapy in Japan.

Management and Risk Factors for Pleural Effusion in Japanese Patients with Chronic Myeloid Leukemia Treated with First-line Dasatinib in Real-world Clinical Practice

Objective Pleural effusion (PE) is a common adverse event that occurs during dasatinib therapy for chronic myeloid leukemia (CML). However, the pathomechanism of PE and appropriate management of Asian patients with CML have not been elucidated. This study investigated the incidence rate, risk, and appropriate management of PE in Asian patients with CML treated with dasatinib. Methods We retrospectively collected data on patients in the chronic phase of CML who received first-line dasatinib therapy and were registered in the CML-Cooperative Study Group database. Patients We identified 44 cases of PE in a series of 89 patients and analyzed previously reported risk factors and effective management of PE. Results A univariate analysis revealed that age, diabetes mellitus, chronic renal failure, hypertension, the history of cardiovascular events, and dasatinib dose were significantly associated with PE. A multivariate analysis revealed that age ≥65 years old was the only independent risk factor for PE. Dasatinib dose reduction and switching to a tyrosine kinase inhibitor showed a statistically significant difference in effectively reducing PE volume compared to single diuretic use. Conclusion Although further studies are warranted, our observations showed that advanced age is a significant risk factor for PE, and tyrosine kinase inhibitor dose reduction or replacement of dasatinib may be an effective management strategy for PE in Asian CML patients who received first-line treatment with dasatinib in real-world clinical practice.

Clinical management of second-generation tyrosine kinase inhibitor therapy in patients with newly diagnosed chronic myeloid leukemia in the chronic phase, focusing on age and dose effects

ABL1-tyrosine kinase inhibitors (TKIs) are an established treatment choice for patients with chronic myeloid leukemia in the chronic phase (CML-CP). However, effects of TKI dose modification have not been well investigated. In this study, we retrospectively analyzed 178 patients with newly diagnosed CML-CP who were treated with dasatinib or nilotinib, focusing on age and dose effects. Efficacy as measured by cumulative major molecular response (MMR) and molecular response 4.5 rates did not differ significantly between the younger group and elderly group. Elderly patients who started nilotinib at a reduced dose had similar or better efficacy outcomes (including cumulative MMR and continuation ratios) than other groups, and elderly patients who started dasatinib at a reduced dose had the lowest MMR ratio and longest MMR duration. Effects of dose modification based on age and TKI selection can be attributed to flexible management of TKI therapy in real-world practice, but further studies are required to validate the findings of this study.

Importance of TKI treatment duration in treatment-free remission of chronic myeloid leukemia: results of the D-FREE study

Treatment-free remission (TFR) is a new goal for patients with chronic myeloid leukemia in chronic phase (CML-CP) with a sustained deep molecular response (DMR) to treatment with tyrosine kinase inhibitors (TKIs). However, optimal conditions for successful TFR in patients treated with second-generation (2G)-TKIs are not fully defined. In this D-FREE study, treatment discontinuation was attempted in newly diagnosed CML-CP patients treated with the 2G-TKI dasatinib who achieved BCR-ABL1 levels of ≤ 0.0032% (MR4.5) on the international scale (BCR-ABL1IS) and maintained these levels for exactly 1 year. Of the 173 patients who received dasatinib induction therapy for up to 2 years, 123 completed and 60 (48.8%) reached MR 4.5. Among the first 21 patients who maintained MR4.5 for 1 year and discontinued dasatinib, 17 experienced molecular relapse defined as loss of major molecular response (BCR-ABL1IS > 0.1%) confirmed once, or loss of MR4 (BCR-ABL1IS > 0.01%) confirmed on 2 consecutive assessments. The estimated molecular relapse-free survival rate was 16.7% at 12 months. This study was prematurely terminated according to the protocol's safety monitoring criteria. The conclusion was that sustained DMR for just 1 year is insufficient for TFR in CML-CP patients receiving dasatinib for less than a total of 3 years of treatment.

Clinical entity of cytomegalovirus disease in patients with malignant lymphoma on bendamustine therapy: a single-institution experience

We investigated the incidence, risk factors, and clinical outcomes of cytomegalovirus (CMV) disease in patients with B-cell lymphoma treated with a bendamustine-containing regimen. The incidence of CMV disease was analyzed after starting treatment with 139 regimens in 126 patients. Clinically significant CMV disease was observed in seven patients. The median duration between bendamustine initiation and the diagnosis of CMV disease was 69 d (range, 40-233), and the median of cycles completed at onset was 2 (range, 1-6). Furthermore, the incidence of CMV disease was significantly higher in the elderly patients than that in the younger patients. The target organs of CMV disease were the liver, gastrointestinal tract, lungs, and retinas. Antiviral therapy was administered to all patients. However, the recurrence of CMV disease was observed in two patients. This study provides information that could contribute to clinicians' decision-making on lymphoma therapy using bendamustine.

Chronic myeloid leukemia: the cutting-edge evidence and things we should know

The prognosis of patients with chronic myeloid leukemia has dramatically improved along with the progress of therapy. However, some concerns remain unresolved, and new treatment strategies have been implemented recently. In this Progress in Hematology corner, the following four issues are presented and discussed: (1) Guidelines for the treatment of chronic myeloid leukemia from the NCCN and ELN: Differences and similarities; (2) Asciminib as a third-line option in chronic myeloid leukemia; (3) Dose optimization of tyrosine kinase inhibitor therapy in chronic myeloid leukemia; and (4) Genetic landscape of chronic myeloid leukemia. All these review articles will provide critical information for hematologists and let us know things we should learn in order to treat patients with this disease adequately.

[Thrombotic microangiopathy with gastrointestinal hemorrhage during carfilzomib therapy for multiple myeloma]

A 70-year-old woman was admitted to the hospital with loss of appetite and melena. She was diagnosed with multiple myeloma 7 years ago and had been on carfilzomib, lenalidomide, and dexamethasone (KRd) therapy for a month because her disease had a relapsed/refractory. On admission, her laboratory tests revealed hemolytic anemia with schizocytes, thrombocytopenia, and acute renal dysfunction. TMA (thrombotic microangiography) caused by carfilzomib was suspected. The possibility of thrombotic thrombocytopenia was considered, and steroid pulse therapy was initiated. Her condition improved significantly after she stopped taking carfilzomib, plasma exchange, hemodiafiltration, steroid pulse therapy, and abstaining from food. The previously reported cases of carfilzomib-induced TMA included fever, gastrointestinal symptoms (nausea/vomiting, diarrhea), and acute renal disorders (lower extremity edema, decreasing urine output). As far as we know, this is the first case of carfilzomib-induced TMA with bleeding as the first symptom.

Outcomes of adolescents and young adults with chronic-phase chronic myeloid leukaemia treated with tyrosine kinase inhibitors

INTRODUCTION

Few studies have reported the outcomes of adolescents and young adults (AYAs) with chronic-phase chronic myeloid leukaemia (CML-CP) on tyrosine kinase inhibitors (TKIs).

MATERIALS AND METHODS

We retrospectively analysed the clinical features, treatment response, and long-term outcomes of 42 AYA patients, in comparison to older patients. The initial therapies of AYA patients between 2001 and 2016 included imatinib (n = 24), dasatinib (n = 13) and nilotinib (n = 5).

RESULTS

In AYA patients, the peripheral blood (PB) white blood cell count and percentage of blasts at the diagnosis were significantly higher, haemoglobin levels were lower and the spleen size was larger. The major molecular response (MMR), event-free survival (EFS) and overall survival (OS) rates were comparable. A sub-analysis comparing imatinib to second-generation TKIs as the initial therapy also showed that their prognosis was comparable.

DISCUSSION

In conclusion, the tumour burden at the diagnosis of CML-CP is higher in AYA patients; however, their prognosis was not worse in comparison to older patients treated with TKIs. KEY MESSAGESFew studies have reported the outcomes of adolescents and young adults (AYAs) with chronic-phase chronic myeloid leukaemia (CML-CP) on tyrosine kinase inhibitors (TKIs). This study showed the tumour burden at the diagnosis of CML-CP is higher in AYA pa tients; however, their prognosis was not worse in comparison to older patients treated with TKIs. Understanding the biological and non-biological features of AYA patients with CML-CP on TKI therapy is essential for better management and to improve the outcomes.

Von Willebrand factor activity levels are influenced by driver mutation status in polycythemia vera and essential thrombocythemia patients with well-controlled platelet counts

Von Willebrand factor ristocetin cofactor (VWF activity) and platelet count (PLT) are negatively correlated in patients with polycythemia vera (PV) and essential thrombocythemia (ET). However, VWF activity does not always normalize upon controlling PLT in those patients. To address this issue, we investigated the correlation between VWF activity and PLT in PV and ET patients. The negative correlation between VWF activity and PLT was stronger in calreticulin mutation-positive (CALR+) ET than in Janus kinase 2 mutation-positive (JAK2+) PV or ET groups. When PLT were maintained at a certain level (<600 × 10⁹ /L), low VWF activity (<50%) was more frequently observed in JAK2+ PV patients than in JAK2+ ET (p=0.013) or CALR+ ET (p=0.013) groups, and in PV and ET patients with ≥50% JAK2+ allele burden than in those with allele burden <50% (p=0.015). High VWF activity (>150%) was more frequent in the JAK2+ ET group than in the CALR+ ET group (p=0.005), and often associated with vasomotor symptoms (p=0.002). This study suggests that some patients with JAK2+ PV or ET have VWF activity outside the standard range even with well-controlled PLT, and that the measurement of VWF activity is useful for assessing the risk of thrombosis and hemorrhage.

Clinical impact of central nervous system-directed therapies on intravascular large B-cell lymphoma: A single institution's experience

Intravascular large B-cell lymphoma (IVLBCL) is a rare subtype of B-cell lymphoma characterized by aggressive disease progression with a high incidence of central nervous system (CNS) involvement. We retrospectively analyzed 16 patients with de novo IVLBCL treated at our hospital between 2004 and 2018 with either standard therapy plus CNS-directed therapy or standard therapy alone. CNS-directed therapy was associated with a significantly better 2-year CNS-free survival (100% vs. 63%, p = 0.0191), despite no significant effects on progression-free or overall survival. Further studies should assess CNS-focused treatment in patients with IVLBCL with or without primary CNS involvement.

Ideal dose intensity of R-CHOP in diffuse large B-cell lymphoma

INTRODUCTION

The standard of care for diffuse large B-cell lymphoma (DLBCL) is rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP). However, its ideal dose intensity varies among cases.

AREAS COVERED

This review provides the latest insights on the dose intensity of R-CHOP for DLBCL patients. Specifically, we discussed the optimal dose intensity for elderly patients, the optimal number of treatment cycles for limited or advanced-stage diseases, and the role of dose-intensified therapies or adding targeted inhibitors.

EXPERT OPINION

Performing a comprehensive or simplified geriatric assessment can distinguish elderly DLBCL patients who will likely benefit from curative R-CHOP. Very elderly or medically unfit patients may need dose reduction in R-CHOP; the Age, Comorbidities, and Albumin index may aid decision-making. Four cycles of R-CHOP followed by two rituximab cycles comprise a new standard for low-risk, limited-stage DLBCL patients. Compared to eight cycles, six cycles of R-CHOP have similar efficacy and fewer toxicities for advanced-stage DLBCL. Dose-intensified therapy is not recommended in most DLBCL cases but may be considered for patients with double (or triple)-hit lymphoma. Applying targeted inhibitors and not merely escalating R-CHOP dose intensity through molecular subtyping will improve the treatment outcome for DLBCL.

[Novel therapies for chronic myeloid leukemia]

Tyrosine kinase inhibitors (TKIs) have dramatically improved the prognosis of chronic myeloid leukemia (CML). Five types of TKIs, including the third-generation TKI, ponatinib, are available in Japan, and TKI resistance has almost been overcome. However, TKI-related adverse events, such as vascular occlusive diseases that are frequently associated with ponatinib use, have become a critical concern. A recent dose optimization study of ponatinib demonstrated a dosing regimen that balances its risks and benefits in CML therapy. Furthermore, asciminib, a CML therapeutic drug with a new mechanism of action, has become available and is being applied clinically in Europe and the USA. This article outlines the latest treatments developed for CML in the chronic phase with prior therapy.

Relationship between Carnitine Deficiency and Tyrosine Kinase Inhibitor Use in Patients with Chronic Myeloid Leukemia

BACKGROUND

Some chemotherapeutic agents cause carnitine deficiency, which causes general fatigue. However, there is no study on carnitine deficiency in patients with chronic myeloid leukemia (CML) during tyrosine kinase inhibitor (TKI) therapy.

OBJECTIVE

In this study, we investigated carnitine concentrations in patients with CML receiving TKI therapy.

METHOD

This study included patients with well-controlled CML. Total carnitine and free carnitine concentrations were evaluated using the enzyme cycling method. The brief fatigue inventory (BFI) and cancer fatigue scale (CFS) were used to assess general fatigue developed during TKI therapy.

RESULTS

Fifty-five patients on TKI therapy were included. Of these, 12 (21.8%) patients had low free carnitine concentrations. Free carnitine concentrations were higher in men than in women. Younger age was closely associated with lower free carnitine concentrations. TKI type, TKI dose, treatment response, or therapy duration were not associated with free carnitine concentrations. None of the scores (the global fatigue score with the BFI and CFS score) correlated with carnitine concentrations. Concentrations of free carnitine in patients in the treatment-free remission group were slightly higher than those in the TKI group, with only 9.1% having a low concentration of free carnitine.

CONCLUSION

Carnitine deficiency is probably not a major cause of general fatigue but may occur in patients with CML receiving TKI therapy.

Absolute Lymphocyte Counts After Lenalidomide Initiation may Predict the Prognosis of Patients With Relapsed or Refractory Multiple Myeloma

BACKGROUND/AIM

We assessed the prognosis of patients with refractory or relapsed multiple myeloma (RRMM) by focusing on the change in absolute lymphocyte counts (ALCs) after lenalidomide and dexamethasone (Ld) initiation.

PATIENTS AND METHODS

In total, 72 patients with RRMM were treated with Ld. ALCs were evaluated before treatment and at 1, 2, and 3 months after Ld initiation. The median ALCs in the entire cohort before and at 1, 2, 3 months after Ld initiation were 1,131, 1,059, 1,222, and 1,162/μl, respectively.

RESULTS

ALCs before Ld initiation did not affect time to next treatment (TNT) or overall survival (OS). However, the patients with ALCs equal to or greater than the median at 3 months showed relatively better TNT than those with lower lymphocyte counts, with a significant difference. OS was also significantly longer in patients with higher ALCs.

CONCLUSION

Immunomodulation by lenalidomide may improve prognosis in patients with RRMM.

Maintenance Therapy With Bortezomib and Dexamethasone for Transplant-ineligible Patients With Multiple Myeloma

BACKGROUND/AIM

Here, we investigated whether bortezomib as a maintenance therapy affected outcomes in transplant-ineligible patients with multiple myeloma (MM).

PATIENTS AND METHODS

Following induction therapy with bortezomib, maintenance therapy with bortezomib (1.3 mg/m ² ) and dexamethasone (20 mg) was administered once or twice every 4 weeks until disease progression. The endpoints of this study were time to next treatment and overall survival.

RESULTS

Seventy-six newly diagnosed, transplant-ineligible patients were treated with a bortezomib-based regimen; 28 discontinued induction therapy, 27 did not receive maintenance therapy after induction therapy (the non-maintenance group), and 21 did (the maintenance group). In the three groups, the median times to the next required treatment were 3, 14, and 37 months, respectively. The 3-year overall survival rates were 55%, 69%, and 85%, respectively. There were no significant differences in patient characteristics between the non-maintenance and maintenance groups, except for poorer estimated glomerular filtration rates in the maintenance group.

CONCLUSION

Bortezomib maintenance therapy may be a useful option for transplant-ineligible patients with MM.

The EUTOS long-term survival score predicts disease-specific mortality and molecular responses among patients with chronic myeloid leukemia in a practice-based cohort

The European Treatment and Outcome Study (EUTOS) long‐term survival (ELTS) score predicts disease‐specific death in patients with chronic myeloid leukemia (CML) being treated with imatinib during the chronic phase (CP) of the disease. However, it is unclear whether the ELTS score predicts CML‐related events or treatment responses. This study evaluated the predictive value of the ELTS score regarding prognosis and treatment response in patients with CML‐CP. Clinical data were retrospectively obtained from patients enrolled in the CML Cooperative Study Group (CML‐CSG), which included patients diagnosed with CML‐CP from April 2001 to January 2016, and treated with any tyrosine kinase inhibitor (TKI) as first‐line therapy. Among 342 eligible patients, the ELTS scores indicated low‐, intermediate‐, and high‐risk in 74%, 21%, and 5% of patients, respectively. Patients with high ELTS scores had significantly higher disease‐specific mortality and worse event‐free survival, progression‐free survival, and overall survival. Among four risk scores, including the Sokal, Hasford, EUTOS, and ELTS scores, risk stratification by the ELTS score had the highest predictive value in assessing patient prognosis, and also in treatment responses. In fact, the EUTOS and ELTS scores were able to predict the major molecular response within 12 months. Most importantly, the ELTS score was the only scoring system that predicted deep molecular response at any time, regardless of risk level (65.0%, 43.7%, and 23.5% in low‐, intermediate‐, and high‐risk groups, respectively). Compared to other risk scores, the ELTS score was the most sensitive risk classification tool for the four endpoints of interest in this study, as well as molecular responses in patients with CML‐CP.

Abemaciclib induces atypical cell death in cancer cells characterized by formation of cytoplasmic vacuoles derived from lysosomes

In the cell cycle, the G₁ /S transition is controlled by the cyclin-dependent kinase (CDK) 4/6-cyclin D complex. Constitutive activation of CDK4/6 dysregulates G₁ /S transition, leading to oncogenic transformation. We found that 3 CDK4/6 inhibitors, abemaciclib, ribociclib, and palbociclib, exerted a cytocidal effect as well as a cytostatic effect at the G₁ phase in cancer cell lines, including A549 human non-small cell lung cancer cells. Among these inhibitors, abemaciclib exhibited the most potent cytotoxic effect. The cell-death phenotype induced by abemaciclib, which entailed formation of multiple cytoplasmic vacuoles, was not consistent with apoptosis or necroptosis. Abemaciclib blocked autophagic flux, resulting in accumulation of autophagosomes, however vacuole formation and cell death induced by abemaciclib were independent of autophagy. In addition, methuosis, a cell-death phenotype characterized by vacuole formation induced by excessive macropinocytosis, was excluded because the vacuoles did not incorporate fluorescent dextran. Of note, both formation of vacuoles and induction of cell death in response to abemaciclib were inhibited by vacuolar-type ATPase (V-ATPase) inhibitors such as bafilomycin A1 and concanamycin A. Live-cell imaging revealed that the abemaciclib-induced vacuoles were derived from lysosomes that expanded following acidification. Transmission electron microscopy revealed that these vacuoles contained undigested debris and remnants of organelles. Cycloheximide chase assay revealed that lysosomal turnover was blocked by abemaciclib. Furthermore, mTORC1 inhibition along with partial lysosomal membrane permeabilization occurred after abemaciclib treatment. Together, these results indicate that, in cancer cells, abemaciclib induces a unique form of cell death accompanied by swollen and dysfunctional lysosomes.

[Transformation of CD5-positive nodal marginal zone lymphoma to diffuse large B-cell lymphoma]

Nodal marginal zone lymphoma (NMZL) is a form of nodal B-cell lymphoma exhibiting proliferation of abnormal lymphocytes at the circumference of the mantle zone in the lymph nodes. Although the outcome of patients with this disease is often favorable, we recently encountered a patient with a CD5-positive NMZL who was resistant to chemotherapy. A 67-year-old woman complaining of systemic lymph node swelling was referred to our hospital. After biopsy of the neck lymph node, she was diagnosed with CD5-positive NMZL. Disease progression was revealed after 16 months, and she was initially treated with chemotherapy consisting of rituximab, cyclophosphamide, vincristine, and prednisolone (R-CVP). However, this therapy was ineffective. Subsequent therapy with rituximab and bendamustine also failed to induce remission. A rebiopsy revealed that the NMZL had transformed into a diffuse large B-cell lymphoma. This patient died after 2 years from the initial diagnosis due to lymphoma progression. Cases of CD5-positive NMZL are rare; thus, it is difficult to study the clinical implications of CD5 expression in this disease. Here we describe the current understanding of CD5 expression in NMZL.

Potential role for second‑generation tyrosine kinase inhibitors in patients with chronic myeloid leukemia harboring additional clonal chromosome abnormalities: A retrospective CML Cooperative Study Group analysis

Tyrosine kinase inhibitor (TKI) treatment is the standard of care for patients with chronic myeloid leukemia (CML). Even in the imatinib era, the presence of 'clonal chromosomal abnormalities' in the Philadelphia chromosome (CCA/Ph+) at diagnosis reportedly increased the risk of disease progression and predicted shorter survival. However, it remains unclear whether CCA/Ph+ is a poor prognostic marker in the era of new‑generation TKIs. The data of patients with CML in the chronic phase (CP) that were extracted from the CML Cooperative Study Group database were retrospectively analyzed. Of the 328 eligible patients, 33 (10.1%) had CCA/Ph+, including 9 major route and 24 minor route aberrations. The characteristics of patients with and without CCA/Ph+ were similar; however, the proportion of blasts was higher among patients with CCA/Ph+. Notably, the survival rate of patients with CCA/Ph+ was not inferior to that of patients without CCA/Ph+, and there were no differences in responses to TKIs. All 9 patients with major route CCA/Ph+ attained a major molecular response (MMR) with no disease progression, and 8 ultimately achieved a deep molecular response. In particular, the median interval between TKI initiation and achievement of MMR was shorter in patients initially treated with a second‑generation TKI than in those treated with imatinib (5 vs. 10 months). The present retrospective study, thus, revealed favorable treatment outcomes in CML‑CP patients with CCA/Ph+ treated with second‑generation TKIs. The data indicated that administering second‑generation TKIs as first‑line treatments is preferable in CML‑CP patients with CCA/Ph+.

A novel fusion gene involving PDGFRB and GCC2 in a chronic eosinophilic leukemia patient harboring t(2;5)(q37;q31)

Background

Platelet‐derived growth factor receptor beta (PDGFRB) rearrangement has been reported in a number of patients with chronic eosinophilic leukemia (CEL), B‐acute lymphoblastic leukemia, myeloproliferative neoplasms, and juvenile myelomonocytic leukemia. Here, we report a case of CEL carrying a novel fusion gene involving PDGFRB and GRIP and coiled‐coil domain containing 2 (GCC2).

Patient and methods

A 54‐year‐old man presenting with a cough and dyspnea was diagnosed with acute eosinophilic pneumonia. Cytogenetic analysis of the bone marrow revealed the presence of t(2;5)(q37;q31). Fluorescence in situ hybridization analysis in the peripheral blood leukocytes revealed the presence of a split signal at PDGFRB gene. Imatinib treatment was effective, and disappearance of t(2;5)(q37;q31) in the bone marrow was confirmed after three months of imatinib therapy. Whole‐genome sequencing was performed in peripheral blood leukocytes collected before imatinib therapy.

Results

A novel fusion gene between exon 22 of GCC2 and exon 12 of PDGFRB was detected and the presence of GCC2‐PDGFRB was confirmed by PCR.

Conclusion

This is the first case report demonstrating the GCC2 gene as a partner of PDGFRB in the pathogenesis of CEL.

Thrombopoietin Levels During Tyrosine Kinase Inhibitor Therapy for Chronic Myeloid Leukemia

BACKGROUND AND OBJECTIVE

Although it is well known that platelet depletion is one of the major adverse events related to tyrosine kinase inhibitor (TKI) therapy, the effect of TKIs on thrombopoietin (TPO), a stimulating factor for thrombopoiesis, has not been examined to date. In this study, we investigated the effect of TKIs on the levels of plasma TPO concentration in patients with well-controlled chronic myeloid leukemia receiving imatinib or dasatinib and those in treatment-free remission (TFR).

METHODS

Blood samples for blood cell counts and plasma TPO levels were obtained from 23 dasatinib-treated patients before and 1 h after intake, 11 patients treated with imatinib before and 2 h after intake, and nine TFR patients. Levels of plasma TPO were determined by using enzyme-linked immunosorbent assays.

RESULTS

Levels of TPO were significantly inversely correlated with platelet counts in the entire cohort (r = - 0.568, p < 0.0001). Dasatinib intake, but not imatinib, significantly reduced platelet counts after intake (p = 0.0009 in dasatinib and p = 0.5431 in imatinib). However, imatinib and dasatinib intake increased the levels of TPO in these patients (p = 0.0024, dasatinib; p = 0.0098, imatinib).

CONCLUSIONS

Our study results suggest that neither dasatinib nor imatinib therapy inhibits TPO production. Rather, transient increases in TPO levels seen with these two treatments might be a result of the decrease in TPO clearance these TKIs confer. However, further investigations are required to clarify the effect of TKIs on thrombopoiesis.

Comparison of the clinical outcomes of nilotinib and dasatinib therapies in newly diagnosed patients in the chronic phase of chronic myeloid leukemia: a retrospective analysis

Treatment with a tyrosine kinase inhibitor (TKI) is the standard of care for patients with chronic myeloid leukemia (CML). The new-generation TKIs, nilotinib and dasatinib, are found to have deeper and faster treatment response rates compared to imatinib in the first-line setting. However, a direct comparison between nilotinib and dasatinib has never been reported previously. Our study aims to compare the outcomes and molecular responses achieved following the first-line use of these two agents in patients with CML-CP. The database of the CML Cooperative Study Group was reviewed and patients with CML in the chronic phase (CP) who were given nilotinib or dasatinib as first-line therapy were identified. Out of 361 patients with CML-CP enrolled in our database, 58 and 63 had been treated with conventional doses of nilotinib (300 mg twice daily) and dasatinib (100 mg once daily), respectively, as first-line therapy. The patient demographics did not show significant differences between the groups. The event-free survival rates did not differ between these two groups. The major molecular response (MMR) and the deep molecular response (DMR) rates by 6, 12, 18, and 24 months did not differ between groups. Among the three scoring systems, only the Hasford score could predict the achievement of DMR, and all of them failed to predict the achievement of MMR in the entire cohort. Our data suggest that both nilotinib and dasatinib have comparable efficacies and promising outcomes.

Combined treatment with benzo[a]pyrene and 1α,25-dihydroxyvitamin D3 induces expression of plasminogen activator inhibitor 1 in monocyte/macrophage-derived cells

Benzo[a]pyrene (BaP) is an environmental pollutant found in cigarette smoke and is implicated as a causative agent of tobacco-related diseases, such as arteriosclerosis. In contrast, vitamin D signaling, which is principally mediated by conversion of vitamin D to the active form, 1α,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], decreases cardiovascular disease risk. However, combined treatment with BaP and 1,25(OH)₂D₃ enhances BaP toxicity, including BaP-DNA adduct formation. We further investigated the cross-talk between BaP and 1,25(OH)₂D₃ signaling pathways, and found that combined treatment with these compounds induces mRNA and protein expression of plasminogen activator inhibitor 1 (PAI-1) in monocyte/macrophage-derived THP-1 and U937 cells. Protein synthesis inhibitor treatment did not inhibit induction of the PAI-1 gene (SERPINE1) in these cells. BaP plus 1,25(OH)₂D₃ induced differentiation markers, inhibited cellular proliferation, and induced apoptosis and oxidative stress in these cells. Reactive oxygen species scavenger treatment suppressed apoptosis but not SERPINE1 induction in cells treated with BaP plus 1,25(OH)₂D₃. Thus, combined treatment with BaP and 1,25(OH)₂D₃ induced SERPINE1 mRNA expression in these cells through a mechanism that does not require de novo protein synthesis or reactive oxygen species production. These findings suggest that induction of the proinflammatory factor PAI-1 plays a role in BaP toxicity. Interestingly, PAI-1 knockdown decreased expression of the cell surface antigen CD14, a monocytic differentiation marker, in THP-1 cells treated with BaP plus 1,25(OH)₂D₃. PAI-1 induction may also be related to a function of monocytes/macrophages in response to xenobiotic and vitamin D signaling.

Efficacy and safety of nilotinib therapy in patients with newly diagnosed chronic myeloid leukemia in the chronic phase

ABL1-tyrosine kinase inhibitors (TKIs) have led to dramatic changes in treatment strategies for chronic myeloid leukemia in the chronic phase (CML-CP). However, clinical studies have highlighted increasing numbers of adverse events (AE) with TKIs. Although TKI modification plays a key role in AE management, this process is poorly understood, particularly in terms of the TKI nilotinib. In the present study, we retrospectively analyzed the records of 70 patients with newly diagnosed (ND)-CML-CP who were treated with nilotinib to investigate the drug potency of nilotinib and treatment management. During a median observation period of 3.4 years, 76% of patients continued nilotinib as a first-line treatment. The 1-year and overall major molecular response (MMR) rates and the overall molecular response (MR) 4.5 rate for all patients receiving first-line nilotinib therapy were 70, 84.2, and 50%, respectively. No case progressed to the accelerated or blast phase during the study. To avoid AEs during the early phase, nilotinib doses were reduced to < 600 mg/day in a third of patients (Reduced group); these patients experienced better therapeutic efficacy and a lower rate of AEs relative to those in Standard group (300 mg twice daily). Ten patients who received < 600 mg/day of nilotinib throughout the study had a 1-year MMR rate and overall MR4.5 rate of 90 and 60%, respectively. In summary, our findings indicate that careful management, including dose reduction, can yield better outcomes in patients with ND-CML-CP.

The Efficacy of Reduced-dose Dasatinib as a Subsequent Therapy in Patients with Chronic Myeloid Leukemia in the Chronic Phase: The LD-CML Study of the Kanto CML Study Group

Objective The aim of this study was to prospectively investigate the efficacy and safety profiles of low-dose dasatinib therapy (50 mg once daily). Methods Patients with chronic myeloid leukemia in the chronic phase (CML-CP) who were being treated with low-dose imatinib (≤200 mg/day), but were resistant to this agent were enrolled in the current study (referred to as the LD-CML study). Results There subjects included 9 patients (4 men and 5 women); all were treated with dasatinib at a dose of 50 mg once daily. Among 8 patients who had not experienced major molecular response (MMR; BCR-ABL1 transcript ≤0.1% according to International Scale [IS]) at study enrollment, 5 attained MMR by 12 months. In particular, 3 of 9 patients demonstrated a deep molecular response (DMR; IS ≤0.0069%) by 18 months. Five patients developed lymphocytosis accompanied by cytotoxic lymphocyte predominance. There was no mortality or disease progression, and all continue to receive dasatinib therapy at 18 months with only 2 patients requiring dose reduction. Toxicities were mild-to-moderate, and pleural effusion was observed in 1 patient (grade 1). Conclusion Low-dose dasatinib can attain MMR and DMR without severe toxicity in patients with CML-CP who are unable to achieve MMR with low-dose imatinib. Switching to low-dose dasatinib should therefore be considered for patients in this setting, especially if they are otherwise considering a cessation of treatment.

[Achievement of a stringent complete response with low-dose pomalidomide monotherapy in a multiple myeloma patient]

An 80-year-old man presented to our hospital with a thoracic vertebrae compression fracture. He was diagnosed with IgG-λ myeloma (International Staging System stage II, Durie-Salmon stage IIIA). Since melphalan-prednisolone (MP) was not effective, we treated him with lenalidomide and low-dose dexamethasone (DEX) (Ld), achieving a partial response. As DEX provoked edema and psychiatric symptoms, the patient disagreed with its use, and pomalidomide (POM) monotherapy was initiated. Although the POM dosage was reduced to 1-2 mg/day due to somnolence, which was reported as an adverse event, stringent complete response (sCR) was achieved and sustained for 10 months following 11 cycles of low-dose POM monotherapy. It is assumed that sCR was achieved with low-dose POM monotherapy due to its early introduction as well as there being no high-risk chromosomal abnormalities. Even though adverse events develop with a standard dose, a continuation of low-dose POM is considered more important than discontinuation.

Introduction of second-generation tyrosine kinase inhibitors may reduce the prognostic impact of high-risk patients, according to the European treatment and outcome study (EUTOS) score

Our study aims to highlight the critical role of the introduction of second generation tyrosine kinase inhibitors (2nd TKIs) on the prognosis of patients with chronic myeloid leukemia (CML) in chronic phase (CML-CP), as determined by European Treatment and Outcome Study (EUTOS) system. Patients who were diagnosed with CML-CP before March 2009 were classified into the imatinib group, and those diagnosed after April 2009 were classified into the 2nd TKI group. EUTOS high-risk patients exhibited significantly worse outcomes in terms of event-free survival (EFS), progression-free survival (PFS), and CML-associated death than those considered to be low-risk. Risk stratification by EUTOS score was predictive of risk-associated clinical outcomes in patients classified into the imatinib group; however, the EUTOS score failed to predict the outcomes of patients classified into the 2nd TKI group. Our data suggest that the introduction of 2nd TKIs might have improved treatment outcomes, particularly in EUTOS high-risk patients.

Clinical effect of immunophenotyping on the prognosis of multiple myeloma patients treated with bortezomib

In the present study, the effect of immunophenotyping on the prognoses of patients with multiple myeloma (MM) treated with bortezomib plus dexamethasone was investigated. The study involved 46 patients with MM, and analyzed the prognostic significance of the expression of cluster of differentiation (CD)45, CD56 and mature plasma cell (MPC)-1, and other factors including the International Staging System (ISS) stage, age, gender, the immunoglobulin subtype and the treatment line number prior to bortezomib treatment. Although CD56 and MPC-1 expression did not appear to affect the time to next treatment (TNT) or overall survival rate (OS), the univariate analysis determined that CD45 positivity was an adverse prognostic factor for TNT and OS, and that being male was significantly associated with inferior TNT and OS. Multivariate analyses determined that CD45 expression was prognostically significant for TNT and OS. In conclusion, CD45 positivity is an adverse prognostic factor in MM patients treated with bortezomib. The data from the present study demonstrate the clinical importance of classifying MM cells immunophenotypically to determine the prognoses of patients.

Incidences and outcomes of therapy-related chronic myeloid leukemia in the era of tyrosine kinase inhibitors: Surveillance of the CML Cooperative Study Group

This study was performed to investigate the features and outcome of patients with therapy-related chronic myeloid leukemia (TR-CML) who were treated with tyrosine kinase inhibitors (TKIs). The analysis included 308 patients with CML in the chronic phase who were extracted from the CML Cooperative Study Group database. Of these patients, 11 (3.6%) were identified as having TR-CML. No differences in age, sex, white blood cell count, hemoglobin level, platelet count, or European Treatment and Outcome Study risk were observed between patients with TR-CML vs. de novo CML. However, the responses of TR-CML patients to TKIs (6, 3, and 2 received imatinib, nilotinib, and dasatinib, respectively) were excellent; all achieved major or deep molecular response. Furthermore, the outcomes of TR-CML patients were relatively favorable; the 3-year event-free survival rates in the TR-CML and de novo CML patients were 100% and 94%, respectively; the difference was not statistically significant. In conclusion, our study showed that TR-CML patients could achieve a good clinical course with TKI therapy. Detailed investigations of TR-CML may provide new insights into CML biology.

Direct effect of dasatinib on signal transduction pathways associated with a rapid mobilization of cytotoxic lymphocytes

It has been shown that an increase in cytotoxic lymphocyte counts in the peripheral blood occurs rapidly after taking dasatinib, but the underlying mechanism is not yet elucidated. To investigate the influence of dasatinib on signal transduction pathways, we investigated the changes in JAK-STAT, mitogen-activated protein kinase (MAPK), and AKT in cytotoxic lymphocytes, including natural killer (NK) cells and cytotoxic T lymphocytes (CTLs), before and after dasatinib treatment in chronic myeloid leukemia patients. Among a total of 30 patients, 18 were treated with dasatinib, nine with imatinib, and three with nilotinib. At constitutive levels, the expression of phosphorylated proteins, pSTAT1, pSTAT3, and pERK in NK cells and pSTAT3 in CTLs, was significantly higher in dasatinib-treated patients. Among the patients evaluated, only dasatinib-treated patients showed inhibition of multiple signaling pathways after taking a tyrosine kinase inhibitor. The magnitude of pERK and pAKT inhibition was closely associated with an increase in NK cells and CTLs, respectively, after taking a tyrosine kinase inhibitor. Those responses were more evident in patients with cytomegalovirus IgG positivity. In this study, we demonstrated for the first time, the influence of dasatinib on cell events in cytotoxic lymphocytes in vivo and explained the possible underlying mechanism that results in lymphocyte mobilization after dasatinib treatment.

Association of pleural effusion with an early molecular response in patients with newly diagnosed chronic-phase chronic myeloid leukemia receiving dasatinib: Results of a D-First study

Despite the efficacy and safety of dasatinib treatment for chronic-phase chronic myeloid leukemia (CML-CP), adverse effects such as pleural effusion (PE) are still a serious concern. We determined the clinical significance of PE incidence using patient data derived from the D-First clinical study. In the present study, chest radiography and quantification of specific lymphocyte subsets were performed routinely after initiation of dasatinib treatment. Among 52 patients with newly diagnosed CML-CP, 17 (33%) developed PE within 18 months after initial dasatinib administration, but all cases were moderate (Grade 1, 10 patients; Grade 2, 7 patients). CD56+ lymphocyte counts at 1 month correlated significantly with the incidence of PE, whereas lymphocytosis did not. The major molecular response (MMR) rate at 3 months (although not at later times) was significantly higher in PE-positive patients than PE-negative patients (59% versus 24%, respectively; P=0.013). Deep molecular response rates did not differ significantly between the PE groups at any time point during the observation period. Our results suggest that an immune-mediated mechanism involving natural killer cells underlies the development of PE in patients receiving dasatinib for 18 months. This mechanism likely promotes transient tumor regression in patients newly diagnosed with CML-CP.

Lyn, a tyrosine kinase closely linked to the differentiation status of primary acute myeloid leukemia blasts, associates with negative regulation of all-trans retinoic acid (ATRA) and dihydroxyvitamin D3 (VD3)-induced HL-60 cells differentiation

Background

Lyn, an import member of Src family kinases (SFKs), is supposed to be implicated in acute myeloid leukemia (AML) pathogenesis and development by participation in AML differentiation, yet the details still remain incompletely understood. The expression status of Lyn and its correlation with multiple clinical parameters including cell differentiation degree, different cytogenetic risk classification, and the activity of myeloperoxidase (MPO) were thus investigated. To address the mechanisms underlying the involvement of Lyn in differentiation induction, the effects of dasatinib, an inhibitor for SFKs including Lyn, on the alterations of all-trans retinoic acid (ATRA)- or dihydroxyvitamin D3 (VD3)-induced differentiation, and c-Myc protein expression were investigated.

Methods

Primary AML blasts were obtained from 31 newly diagnosed AML patients with different French-American-British (FAB) subtypes. The expression of phosphorylated and total Lyn, c-Myc, and CD11b, CD11c and CD15 was analyzed by flow cytometry. The activation of Akt and Erk known to be involved in the regulation of c-Myc expression was investigated using western blotting.

Results

Significant higher expression levels of total Lyn were observed in AML patients with favorable cytogenetics, higher MPO activity and FAB M2 subtype. A clear positive correlation between the expression levels of Lyn and differentiation status of primary AML blasts was observed. Dasatinib inhibited the expression of phosphorylated Lyn, and further enhanced the differentiation-inducing activity of ATRA and VD3 in HL-60 cells. Augmented downregulation of c-Myc protein expression was observed in the combination treatment with ATRA, VD3 and dasatinib compared to treatment with each reagent alone in HL-60 cells. The suppression of the activation of Akt and Erk was also observed concomitantly.

Conclusions

The expression level of total Lyn is closely linked to the differentiation status of AML blasts. The enhancement of differentiation-inducing activity of ATRA/VD3 by dasatinib suggested that Lyn was associated in the negative regulation of ATRA/VD3-induced HL-60 cells differentiation. The enhancement probably was attributed to the downregulation of c-Myc implicated with the suppression of the activation of Akt and Erk. These results provide novel insights into a possible combinational therapeutic approach by targeting Lyn for AML patients, and offer new possibilities for the combination therapy with VD3 and dasatinib.

Clinical significance of co-expression of MYC and BCL2 protein in aggressive B-cell lymphomas treated with a second line immunochemotherapy

The clinical significance of concurrent expression of MYC and BCL2 protein, known as "double-expressor lymphoma" (DEL), among patients with relapsed or refractory aggressive B-cell lymphomas, remains unclear. A retrospective analysis was performed of 38 patients treated with a salvage treatment consisting of rituximab, ifosfamide, etoposide, cytarabine and dexamethasone followed by consolidative high-dose chemotherapies. A total of 17 cases (45%) were categorized as DEL using immunohistochemical assay with a cut-off value of positivity of 40% for MYC and 50% for BCL2, respectively. DEL was associated with a lower overall response rate (35% vs 71%, p = 0.0481), worse 2-year progression-free survival (9% vs 67%, p = 0.001) and overall survival (35% vs 71%, p = 0.037). This analysis suggests that DEL is common among patients with relapsed/refractory aggressive B-cell lymphomas and that such patients require novel treatment strategies.

Higher Red Blood Cell Distribution Width Is an Adverse Prognostic Factor in Chronic-phase Chronic Myeloid Leukemia Patients Treated with Tyrosine Kinase Inhibitors

The significance of red blood cell distribution width (RDW) was evaluated in patients with chronic myeloid leukemia (CML) in the chronic phase (CP). Eighty-four patients with newly-diagnosed CML-CP treated with any tyrosine kinase inhibitor (TKI) were analyzed. Patients were divided into two groups: a low-RDW group (RDW values ≤15%, n=31) and a high-RDW group (RDW values >15%, n=53). The 5-year event-free survival (EFS) and transformation-free survival (TFS) rates differed significantly between the low- and high-RDW groups (100% and 68%, respectively, in EFS, p=0.0071 and 100% and 81%, respectively, in TFS, p=0.039). The stratification by RDW had an impact on overall 5-year survival (100% in the low and 77% in the high RDW groups, p=0.047). We conclude that the RDW has a critical role in risk stratification of CML-CP patients for predicting treatment responses and outcomes.

Early cytotoxic lymphocyte expansion contributes to a deep molecular response to dasatinib in patients with newly diagnosed chronic myeloid leukemia in the chronic phase: results of the D-first study

Dasatinib is one of the key treatment options for chronic myeloid leukemia (CML) patients. Increase in lymphocyte counts has been known to be predictive of a good treatment response under dasatinib treatment as a second line therapy. However, clinical significance of lymphocyte dynamics in the upfront setting has yet to be clarified. To investigate the significance of lymphocyte dynamics in newly diagnosed chronic phase (CP)-CML, patient data of D-First study (ClinicalTrials.gov NCT01464411) were analyzed. Fifty-two CML-CP patients enrolled to this study were treated with dasatinib (100 mg day(-1) ) and all were followed-up for 18 months. The incidence of lymphocyosis was observed in 14 (27%), but it was not associated with deep molecular response achievement. However, natural killer (NK) cell or cytotoxic T lymphocyte (CTL) counts at 1 month were significantly higher in patients with deep molecular response (DMR) by 18 months compared to those without DMR. When the patients were divided into two groups according to those calculated thresholds by receiver operating characteristic curve (407/μL for NK cells and 347/μL for CTLs), the cumulative DMR rates by 18 months were significantly better in higher value group compared to lower value group. In contrast, regulatory T cell counts were significantly lower at 12 and 15 months in patients achieved DMR. These results suggest the presence of dual effects of dasatinib on immune system through the cytotoxic lymphocytes activation and Treg deregulation in different periods in newly diagnosed CML-CP.

[Diagnostic value of brain biopsy in intravascular large B-cell lymphoma mimicking progressive multifocal leukoencephalopathy: case report]

We report a 68-years-old woman with systemic sclerosis and interstitial pneumonia (IP). She had developed subacute progressively encephalopathy and dementia while treated with oral cyclophosphamide and prednisolone. She admitted to our hospital because of syncope. Laboratory tests indicated slight elevated cerebrospinal fluid protein, and levels of serum C-reactive protein (CRP), levels of soluble IL-2 receptor was normal. But, magnetic resonance imaging (MRI) of the brain showed multiple infarct-like lesions mainly in the white matter, which mimics progressive multiple leukoencephalopathy (PML). Twenty days after admission, the retested MRI of the brain disclosed initial lesions progressively enlarged and numbers of the lesions were increased. The polymerase chain reaction (PCR) for JC virus of cerebrospinal fluid was negative. To make diagnosis, brain biopsy was performed. Microscopic examination revealed that small vessels were filled with lymphoma cells (CD20+, CD79+, CD3-), and intravascular lymphoma (IVL) was diagnosed. She treated with regimens of R-CHOP. After chemotherapy her consciousness and dementia were gradually improved. IVL of central nerve system (CNS) is a rare disease, and its common symptoms are ischemia, infarction and dementia. Diagnosis of IVL of CNS is difficult when the lesion mimics PML, and patient with similar laboratory examinations and radiographic findings of PML should undergo brain biopsy detected malignant cell in small vessels, which is a value of diagnosis.

Shorter halving time of BCR-ABL1 transcripts is a novel predictor for achievement of molecular responses in newly diagnosed chronic-phase chronic myeloid leukemia treated with dasatinib: Results of the D-first study of Kanto CML study group

To investigate the factors that affect molecular responses on dasatinib treatment in patients with chronic-phase chronic myeloid leukemia (CML-CP), we performed a clinical trial named the "D-First study." Fifty-two patients with newly diagnosed CML-CP were enrolled in this study and received 100 mg dasatinib once daily. A deep molecular response (DMR) was defined as <50 copies/μg RNA of BCR-ABL1 transcript value corrected by GAPDH, which ensures <0.01% of BCR-ABL1 transcript value according to International Scale (BCR-ABL1(IS)). The halving time for BCR-ABL1 transcripts was calculated using transcript levels before dasatinib treatment, transcript levels after 3 months of treatment, and the treatment time between these two points. In terms of molecular response, 38 of 51 (75%) patients reached major molecular response (MMR) by 12 months, and the rate of DMR by 18 months was 59% (30/51). While both BCR-ABL1 transcript levels before treatment and a shorter halving time of BCR-ABL1 transcripts (≤14 days) were significant factors affecting achievement of MMR by 12 months, the Sokal score at diagnosis was not associated with MMR. Importantly, the halving time was the only factor that predicted achievement of DMR by 18 months. We showed that patients with CML-CP treated with dasatinib can be stratified according to the early treatment response as determined by the halving time of BCR-ABL1 transcripts. These data emphasize the significance of the early response from dasatinib treatment in achieving a DMR. (ClinicalTrials.gov; NCT01464411).

Granulocyte colony-stimulating factor potentiates all-trans retinoic acid-induced granulocytic differentiation in acute promyelocytic leukemia cell line HT93A

BACKGROUND

Granulocyte colony-stimulating factor (G-CSF) promotes proliferation, survival, and differentiation of myeloid-linage leukemic cells, as well as normal hematopoietic cells. Terminal granulocytic differentiation can be induced in acute promyelocytic (APL) cell line HT93A by G-CSF and all-trans retinoic acid (ATRA). Because the detailed mechanism has never been shown, we investigated the signal transduction pathway in granulocytic differentiation by G-CSF, alone or in combination with ATRA.

METHODS

HT93A cell viability and growth were investigated by trypan blue exclusion assay. Cell differentiation was assessed by CD11b and CD34 expressions. Intracellular protein expressions were also evaluated by flow cytometry after fixation and permeabilization.

RESULTS

ATRA (100 nM) induced granulocytic differentiation (upregulation of CD11b and downregulation of CD34) and the effect was potentiated by addition of G-CSF, while G-CSF alone had no effect on HT93A cells. The addition of G-CSF to ATRA had little or no effect on NB4 and THP-1 cells in comparison to ATRA alone. G-CSF receptor expression was reduced by ATRA treatment in a time-dependent manner. After 5 days' incubation with ATRA, the expression levels of signal transducer and activator of transcription (STAT) 3, and phosphorylated STAT3 and STAT5, were significantly reduced. STAT5 was strongly activated by G-CSF stimulation in ATRA-pretreated cells in comparison to untreated cells. In contrast, STAT3 showed no response to G-CSF. Janus kinase (JAK) inhibitor ruxolitinib (320 nM) had little or no effect on ATRA-induced differentiation, but eliminated the enhancing effect of G-CSF, as evidenced by the levels of CD11b and CD34 expression. These results suggest G-CSF activates STAT5 through the JAK pathway in combination with ATRA, resulting in myeloid differentiation in HT93A cells.

CONCLUSIONS

In conclusion, activation of the JAK-STAT pathway is likely essential for inducting differentiation in the APL cell line HT93A; thus, monitoring its expression and activation is important for predicting clinical efficacy and understanding the mechanisms of cytokine-dependent myelopoiesis, proliferation, and differentiation of acute myeloid leukemia.

ETV6/ARG oncoprotein confers autonomous cell growth by enhancing c-Myc expression via signal transducer and activator of transcription 5 activation in the acute promyelocytic leukemia cell line HT93A

We investigated the role of ETV6/ARG fusion gene by exposing the HT93A cell line to nilotinib. HT93A cells were cultured with or without nilotinib±50 ng/mL of granulocyte colony-stimulating factor (G-CSF). Nilotinib treatment inhibited cell growth by increasing the percentage of cells in G0/G1 phase through the decrease of phosphorylated signal transducer and activator of transcription 3 (STAT3) (Y705), STAT5 (Y694) and c-Myc expression. After stimulation with G-CSF, STAT5 but not STAT3 was significantly phosphorylated in both nilotinib-treated and untreated cells. Moreover, combination therapy with nilotinib and G-CSF returned the expression level of c-Myc, cell growth and cell cycle distribution to the control level. These findings suggest that the ETV6/ARG oncoprotein contributes to autonomous cell growth by compensating for the requirement of growth factor through activating STAT5 signaling, which leads to the up-regulation of c-Myc. Our data suggest that ETV6/ARG oncoprotein is a potential target in the treatment of leukemia.