Internal tandem duplications of the FMS-like tyrosine kinase 3 (FLT3) gene are one of the most frequent gene mutations in acute myeloid leukemia (AML) and are associated with poor clinical outcome. The remission rate is high with intensive chemotherapy, but most patients eventually relapse. During the last decade, FLT3 mutations have emerged as an attractive target for a molecularly specific treatment strategy. Targeting FLT3 receptor tyrosine kinases in AML has shown encouraging results in the treatment of FLT3 mutated AML, but in most patients responses are incomplete and not sustained. Newer, more specific compounds seem to have a higher potency and selectivity against FLT3. During therapy with FLT3 tyrosine kinase inhibitors (TKIs) the induction of acquired resistance has emerged as a clinical problem. Therefore, optimization of the targeted therapy and potential treatment options to overcome resistance is currently the focus of clinical research. In this review we discuss the use and limitations of TKIs as a therapeutic strategy for the treatment of FLT3 mutated AML, including mechanisms of resistance to TKIs as well as possible novel strategies to improve FLT3 inhibitor therapy.
Acute myeloid leukemia; FLT3 mutations; molecular tailored therapy; tyrosine kinase inhibitors; mechanism of resistance
Fludarabine (Flu), clofarabine (Clo) and busulfan (Bu) are used in allogeneic hematopoietic stem cell transplant (allo-HSCT). We reported that combining [Flu + Clo + Bu] had a synergistic cytotoxicity in AML cells. We hypothesized that combining [Flu + Clo + Bu] with the histone deacetylase inhibitor SAHA will further enhance cytotoxicity. We exposed the acute myeloid leukemia (AML) cell lines KBM3/Bu2506 and OCI-AML3 to Flu, Clo, Bu and SAHA alone and in various combinations. [Flu + Clo + Bu + SAHA] resulted in synergistic cytotoxicity, which can be attributed to (1) activated DNA-damage response and cell cycle checkpoint activation through the ATM–CHK2–P53 (or P73) pathway or ATM–CHK2–cdc25–cdc2 pathway, (2) histone modifications and (3) activated apoptosis pathway. The [Flu + Clo + Bu + SAHA] combination causes mitochondrial outer membrane permeabilization, leakage of cytochrome c and Smac/Diablo into the cytosol with caspase activation, and release of apoptosis-inducing factor (AIF) into the nucleus resulting in nuclear fragmentation and cell death. These results provide a mechanistic basis for using SAHA in future clinical trials with double nucleoside analog-busulfan combinations in pretransplant conditioning therapy.
DNA alkylator; nucleoside analog; SAHA; AML; drug cytotoxicity
The optimal treatment for chronic myeloid leukemia (CML) relapsing following allogeneic bone marrow transplantation (alloBMT) is unknown. We performed a single-center retrospective analysis of 71 consecutive patients undergoing alloBMT for CML from 1995–2008. A multi-state model was used to quantify the cumulative incidences of complete molecular response (CMR) and death following alloBMT. The primary analysis was the comparison of three treatment interventions (tyrosine kinase inhibitor: TKI, donor lymphocyte infusion: DLI, and TKI+DLI) for relapsed disease post-alloBMT. Forty-five (63%) patients relapsed post-alloBMT (molecular relapse: n=16, cytogenetic relapse: n=20, hematologic relapse: n=2, advanced phase relapse: n=7) and 40 patients underwent one of three treatments: TKI-only (n=13), DLI-only (n=11), or TKI+DLI (n=16). Although not statistically significant, the TKI-only group had the highest cumulative incidence of CMR and the lowest cumulative incidence of death compared to DLI and TKI+DLI. These data support the finding that TKI therapy is active in the post-alloBMT setting.
chronic myeloid leukemia; relapse; allogeneic transplantation
Identification of the genomic regions most intimately associated with non-Hodgkin's lymphoma (NHL) pathogenesis is confounded by the genetic heterogeneity of human populations. We hypothesize that the restricted genetic variation of purebred dogs, combined with the contrasting architecture of the human and canine karyotypes, will increase the penetrance of fundamental NHL-associated chromosomal aberrations in both species. We surveyed non-random aneuploidy in 150 canine NHL cases, revealing limited genomic instability compared to their human counterparts and no evidence for CDKN2A/B deletion in canine B-cell NHL. ‘Genomic recoding’ of canine NHL data into a ‘virtual human’ chromosome format showed remarkably few regions of copy number aberration (CNA) shared between both species; restricted to regions of dog chromosomes 13 and 31, and human chromosomes 8 and 21. Our data suggest that gene discovery in NHL may be enhanced through comparative studies exploiting the less complex association between CNAs and tumor pathogenesis in canine patients.
comparative genomic hybridization (CGH); canine; lymphoma; chromosome; microarray
We hypothesized that GTI-2040, a 20-mer oligonucleotide complementary to the R2 subunit mRNA of ribonucleotide reductase, combined with high dose cytarabine (HiDAC) would result in enhanced cytotoxicity by favoring Ara-CTP DNA incorporation. In a phase I dose escalation trial, adults (≥60 years) with refractory or relapsed acute myeloid leukemia (AML) received daily HiDAC plus infusional GTI-2040. Using a novel assay, evidence of intracellular drug accumulation and target R2 down-regulation was observed. GTI-2040/HiDAC can be administered safely. However, with no complete remissions observed, alternative doses and schedules may need to be investigated to achieve clinical activity in older patients with AML.
Acute myeloid leukemia; antisense therapy; phase I study; GTI-2040; ribonucleotide reductase
Malignant B-cells express measurable levels of HLA class II proteins, but often escape immune recognition by CD4+ T cells. Resveratrol (Resv) has been the focus of numerous investigations due to its potential chemopreventive and anti-cancer effects, but it has never been tested in the regulation of immune components in B-cell tumors. Here, we show for the first time that Resv treatment enhances HLA class II-mediated immune detection of B-cell lymphomas by altering immune components and class II presentation in tumor cells. Resv treatment induced an upregulation of both classical and non-classical HLA class II proteins (DR and DM) in B-lymphoma cells. Resv also altered endolysosomal cathepsins (Cat S, B and D) and a thiol reductase (GILT), increasing HLA class II-mediated antigen (Ag) processing in B-cell lymphomas and their subsequent recognition by CD4+ T cells. Mechanistic study demonstrated that Resv treatment activated the recycling class II pathway of Ag presentation through upregulation of Rab 4B protein expression in B-lymphoma cells. These findings suggest that HLA class II-mediated immune recognition of malignant B-cells can be improved by Resv treatment, thus encouraging its potential use in chemoimmunotherapy of B-cell lymphoma.
B-cell lymphoma; resveratrol; apoptosis; HLA class II; rab 4b; endocytosis and recycling; Antigen presentation; CD4+ T cell recognition
Exposure to Agent Orange (AO) and the contaminating chemical 2,3,7,8-Tetrachlorodibenzodioxin (TCDD) has been associated with the development of chronic lymphocytic leukemia (CLL). Of the195 veterans diagnosed with CLL from 2001–2010 in a retrospective cohort from the Minneapolis VA, 33 (17%) were exposed to AO. Prognostic factors including Rai stage, lymphocyte doubling time and cytogenetics did not differ between exposed and unexposed patients. Exposed patients were younger at diagnosis (61 vs 72 years, p=0.001) and time to CLL treatment was shorter (9.6 vs 30.2 months, p=0.02). Overall survival did not differ between exposed and unexposed patients on Kaplan Meier analysis, but when adjusted for age, AO exposure had a hazard ratio of death of 1.8 compared to non-exposure (95% CI 0.7–4.5 p=0.24). The high estimate of the mortality hazard combined with the relatively low numbers in the exposure group suggests that further examination in a larger patient population is warranted.
Chronic lymphocytic leukemia; Agent Orange; prognosis; survival
The addition of arsenic trioxide (ATO) to frontline therapy of acute promyelocytic leukemia (APL) has been shown to result in significant improvements in disease-free survival (DFS). FLT3 mutations are frequently observed in APL, but its prognostic significance remains unclear. We analyzed 245 newly diagnosed adult patients with APL treated on intergroup trial C9710 and evaluated previously defined biological and prognostic factors and their relationship to FLT3 mutations and to additional karyotypic abnormalities. FLT3 mutations were found in 48% of patients, including 31% with an internal tandem duplication (FLT3-ITD), 14% with a point mutation (FLT3-D835) and 2% with both mutations. The FLT3-ITD mutant level was uniformly low, <0.5. Neither FLT3 mutation had an impact on remission rate, induction death rate, DFS or overall survival (OS). The addition of ATO consolidation improved outcomes regardless of FLT3 mutation type or level, initial white blood cell count, PML–RARA isoform type or transcript level. The presence of a complex karyotype was strongly associated with an inferior OS independently of post-remission treatment. In conclusion, the addition of ATO to frontline therapy overcomes the impact of previously described adverse prognostic factors including FLT3 mutations. However, complex karyotype is strongly associated with an inferior OS despite ATO therapy.
Acute promyelocytic leukemia; arsenic trioxide; FLT3 mutations; mutant level; complex karyotype; prognosis
Epstein–Barr virus (EBV) is associated with aggressive B cell lymphomas (BCLs). Latent membrane protein 1 (LMP1) of EBV is an oncogenic protein required for EBV B cell transformation. However, LMP1 is a weak oncogene in mice. Mice expressing Myc inserted 5′ of the Eμ enhancer (iMycEμ), mimicking the t(8;14) translocation of endemic Burkitt lymphoma, develop delayed onset BCLs. To investigate potential cooperation between LMP1 and oncogenic MYC, we produced mice expressing the LMP1 signaling domain via a hybrid CD40–LMP1 transgene (mCD40–LMP1), and the dysregulated MYC protein of aggressive EBV+ BCLs. mCD40-LMP1/iMycEμ mice trended toward earlier BCL onset. BCLs from mCD40–LMP1/iMycEμ mice expressed LMP1 and were transplantable into immunocompetent recipients. iMycEμ and mCD40–LMP1/iMycEμ mice developed BCLs with similar immunophenotypes. LMP1 signaling was intact in BCLs as shown by inducible interleukin-6. Additionally, LMP1 signaling to tumor cells induced the two isoforms of Pim1, a constitutively active prosurvival kinase implicated in lymphomagenesis.
LMP1; MYC; lymphoma
The interferon consensus sequence binding protein (Icsbp) is a transcription factor that influences multiple aspects of myelopoiesis. Expression of Icsbp is decreased in the bone marrow of human subjects with chronic myeloid leukemia (CML), and studies in murine models suggest that Icsbp functions as an anti-oncogene for CML. We previously identified a set of Icsbp target genes that may contribute to this anti-oncogene effect. The set includes PTPN13, the gene encoding Fas-associated phosphatase 1 (Fap1, a Fas antagonist). We previously demonstrated that myeloid progenitor cells from Icsbp-knockout mice exhibit Fap1-dependent Fas resistance. In the present study, we determined that the Fas resistance of Bcr−abl+ cells is Icsbp- and Fap1-dependent. We also found that treatment of Bcr−abl+ bone marrow cells with a Fap1-blocking peptide prevents in vitro selection of a tyrosine kinase inhibitor (TKI)-resistant population. Therefore, these results have implications for therapeutic targeting of the Fas-resistant leukemia stem cell population and addressing TKI resistance in CML.
Leukemia; gene regulation; apoptosis
Alemtuzumab consolidation has been investigated to improve remission duration after fludarabine-based induction for chronic lymphocytic leukemia (CLL). The impact on genomic high-risk disease remains unknown. CALGB 19901 and 10101 enrolled previously untreated patients to receive alemtuzumab consolidation after fludarabine-based induction. Immunoglobulin heavy chain gene mutation status (IGVH) and interphase cytogenetics were assessed retrospectively. Treatment response with these alemtuzumab-containing regimens was similar, regardless of genomic risk, except for patients harboring del(17p), where few complete remissions were observed. PFS was similar between IGVH groups, but OS was inferior in IGVH unmutated patients (P=0.03). Cytogenetic risk group was associated with PFS and OS (P=0.01 for both), with similarly short PFS in del(17p) and del(11q) and particularly short OS in del(17p) patients. Cytogenetic risk group remained signficantly associated with PFS and OS when controlling for other prognostic factors (PFS: P=0.009; OS: P=0.02), as did the negative association of IGVH unmutated disease with OS (P=0.004). Results were similar when restricting to patients who received at least one dose of alemtuzumab consolidation, demonstrating limited ability to overcome the poor outcome associated with high-risk genetic features.
CLL; alemtuzumab; clinical trial; cytogenetics; immunoglobulin genes
The endoplasmic reticulum (ER) plays a vital function in multiple cellular processes. There is a growing interest in developing therapeutic agents that can target the ER in cancer cells, inducing a stress response that leads to cell death. However, ER stress-inducing agents can also induce autophagy, a survival strategy of cancer cells. Therefore, by inhibiting autophagy we can increase the efficacy of the ER stress-inducing agents. Nelfinavir, a human immunodeficiency virus (HIV) protease inhibitor with anti-cancer properties, can induce ER stress. Nelfinavir’s effects on chronic lymphocytic leukemia (CLL) are yet to be elucidated. Herein we demonstrate that nelfinavir induces ER morphological changes and stress response, along with an autophagic protective strategy. Our data reveal that chloroquine, an autophagy inhibitor, significantly increases nelfinavir cytotoxicity. These results identify a novel strategy potentially effective in CLL treatment, by repositioning two well-known drugs as a combinatorial therapy with anti-cancer properties.
Nelfinavir; autophagy; ER stress; drug screening; chronic lymphocytic leukemia
Twenty severe aplastic anemia (SAA) patients underwent allogeneic stem cell transplantation (allo-SCT) with fludarabine (FLU), cyclophosphamide and antithymocyte globulin from a matched related (n=7, age ≥ 40) or unrelated donor (n=13, any age). Median age was 34 years (range 1–59). Median time from diagnosis to allo-SCT was 12 months (range 2–244). Seventeen out of 19 evaluable patients engrafted (90%). There were two secondary graft failures (10%). Median time to neutrophil recovery was 15 days (range 8–30). Chimerism studies indicated ≥90% donor-derived engraftment in 16/19 evaluable patients (75%). Four out of 20 patients (20%) developed acute (grade II–IV) GVHD, and 6/16 evaluable patients (37%) developed chronic GVHD. We observed EBV reactivation and viremia in seven patients, which was successfully treated with rituximab in all but one instance (where it was self-limiting). Thirteen patients (62%) are alive (including eight of the last nine treated) with a median follow-up of 30 months (range 3–112). Seven patients expired (graft rejection n=1, GVHD n=1, multiorgan failure n=1, infection n=2, EBV post-transplant lymphoproliferative disorder/PTLD n=2). Total body irradiation-free, FLU-based conditioning for matched related and unrelated allo-SCT is feasible with high engraftment rates. EBV PTLD remains a drawback of this approach.
Aplastic anemia; bone marrow failure; stem cell transplantation; bone marrow transplantation; conditioning regimen; fludarabine
This study utilized claims data from a national US commercial health insurer to examine rates of cytopenia-related complications (significant bleeding, infection) and health care utilization (emergency room visits, inpatient hospitalizations) among patients with myelodysplastic syndromes (MDS) within predefined periods of transfusion activity and active therapy. Periods with no transfusions, regardless of relationship to treatment intervention, were associated with lower rates of cytopenia-related complications. These data suggest that eliminating or reducing the need for transfusions may help to reduce MDS-related medical problems, and treatment toward that goal should be considered in patients with MDS needing transfusions.
MDS; myelodysplastic syndromes; transfusion; outcomes; cytopenia; utilization
Older patients with Burkitt lymphoma/leukemia (BL) have inferior outcomes. Because cyclophosphamide is highly active in BL and can be dose-escalated without stem-cell rescue, we designed a short, cyclophosphamide-intensive regimen without anthracyclines for patients aged ≥30 with untreated, non-HIV-associated BL/atypical BL. Two cycles involving cyclophosphamide 1500 mg/m2, vincristine, rituximab, prednisone, methotrexate 3 g/m2, and intrathecal cytarabine were delivered 2 weeks apart, followed by intensification with high-dose cyclophosphamide (50 mg/kg/day for 4 days) and rituximab. Of 21 patients, median age 53 (range, 34–75), 71% had stage IV, 95% were high-risk and 29% had performance status 3–4. Response occurred in all evaluable patients post-cycle 2 and in 76% post-intensification. Five non-relapse deaths occurred (four before intensification). The estimated 1-year and 3-year event-free survival was 52%; 1-year and 3-year overall survival was 57%. Seventeen (81%) received intensification (median 30 days to intensification). Brief, anthracycline-sparing, intensive cyclophosphamide (BASIC) therapy yields durable remissions in poorer-risk BL/atypical BL.
Atypical Burkitt lymphoma; Burkitt lymphoma; cyclophosphamide; unclassifiable B-cell lymphoma
Unrelated cord blood transplantation (CBT) is an alternative treatment option for patients who lack a matched donor. However, the optimal type and intensity of the preparative regimen remains unclear. We evaluated the toxicity and outcomes of a conditioning regimen consisting of melphalan 140 mg/m2 (day −8), thiotepa 10 mg/kg (day −7), fludarabine 160 mg/m2 over 4 days (days −6 to −3), and rabbit ATG 1.25 mg/kg (day −4) and 1.75 mg/kg (day −3) (FMT). Forty-seven patients with advanced hematologic malignancies with a median age of 23 years (30 adults and 17 children) were treated. Sixty percent of patients were in remission at transplant. Ninety-one percent of the patients engrafted neutrophils after a median of 22 days, and all but one of the patients achieving donor engraftment had hematopoietic recovery with 100% cord blood-derived cells. Grade 3 gastrointestinal toxicity was the major non-hematopoietic toxicity occurring in 32% of patients. Cumulative incidence of day-100 grade II-IV aGVHD and cGVHD were 53% and 34%, respectively, and non-relapse mortality at day 100 and 2 years was 11% and 40%. Two-year disease-free and overall survival rates were 31% and 44%, respectively. These results suggest that FMT is a feasible conditioning regimen for patients undergoing CBT.
Unrelated cord blood transplantation; reduced-intensity conditioning; fludarabine; melphalan; thiotepa