[Show abstract][Hide abstract] ABSTRACT: Abstract Quantitative detection of BCR-ABL1 transcript is essential in monitoring residual disease of Philadelphia chromosome positive B lymphoblastic leukemia (Ph+ B-LL). We studied the kinetics of BCR-ABL1 transcript in 41 Ph+ B-LL patients in correlation with their clinical outcome. Twenty three patients achieved complete molecular remission at 6 months post-treatment. This was associated with a lower relapse risk and better overall survival. Likewise, sustainable complete molecular remission in 27 patients was associated with superior clinical outcome. Sporadic low level BCR-ABL1 was detected in 12 of 27 patients who had attained complete molecular remission. The relapse rate was significantly higher in non-transplant patients with persistent positive BCR-ABL1 than patients transplanted when BCR-ABL1 was detectable. All 8 patients harboring ABL1 kinase domain mutations died of disease or were transferred to hospice care. We concluded that monitoring the level of BCR-ABL1 transcript after hematologic remission has predictive value to the long term outcome.
[Show abstract][Hide abstract] ABSTRACT: Resistance to the BCR-ABL inhibitor imatinib mesylate (IM) poses a major problem for the treatment of chronic myeloid leukemia (CML). IM resistance often results from a secondary mutation in BCR-ABL that interferes with drug binding. However, in many instances, there is no mutation in BCR-ABL, and the basis of such BCR-ABL-independent IM resistance remains to be elucidated. To gain insight into BCR-ABL-independent IM resistance mechanisms, we performed a large-scale RNA interference screen and identified IM-sensitizing genes (IMSGs) whose knockdown renders BCR-ABL(+) cells IM-resistant. In these IMSG knockdown cells, RAF/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling is sustained after IM treatment because of up-regulation of PRKCH, which encodes the protein kinase C (PKC) family member PKCη, an activator of CRAF. PRKCH is also up-regulated in samples from CML patients with BCR-ABL-independent IM resistance. Combined treatment with IM and trametinib, a U.S. Food and Drug Administration-approved MEK inhibitor, synergistically kills BCR-ABL(+) IMSG knockdown cells and prolongs survival in mouse models of BCR-ABL-independent IM-resistant CML. Finally, we showed that CML stem cells contain high levels of PRKCH, and this contributes to their intrinsic IM resistance. Combined treatment with IM and trametinib synergistically kills CML stem cells with negligible effect on normal hematopoietic stem cells. Collectively, our results identify a therapeutically targetable mechanism of BCR-ABL-independent IM resistance in CML and CML stem cells.
Science translational medicine 09/2014; 6(252):252ra121. · 14.41 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND. Anemia, or low blood hemoglobin (Hgb) levels, afflicts 2 billion people worldwide. Currently, Hgb levels are typically measured from blood samples using hematology analyzers, which are housed in hospitals, clinics, or commercial laboratories and require skilled technicians to operate. A reliable, inexpensive point-of-care (POC) Hgb test would enable cost-effective anemia screening and chronically anemic patients to self-monitor their disease. We present a rapid, stand-alone, and disposable POC anemia test that, via a single drop of blood, outputs color-based visual results that correlate with Hgb levels. METHODS. We tested blood from 238 pediatric and adult patients with anemia of varying degrees and etiologies and compared hematology analyzer Hgb levels with POC Hgb levels, which were estimated via visual interpretation using a color scale and an optional smartphone app for automated analysis. RESULTS. POC Hgb levels correlated with hematology analyzer Hgb levels (r = 0.864 and r = 0.856 for visual interpretation and smartphone app, respectively), and both POC test methods yielded comparable sensitivity and specificity for detecting any anemia (n = 178) (<11 g/dl) (sensitivity: 90.2% and 91.1%, specificity: 83.7% and 79.2%, respectively) and severe anemia (n = 10) (<7 g/dl) (sensitivity: 90.0% and 100%, specificity: 94.6% and 93.9%, respectively). CONCLUSIONS. These results demonstrate the feasibility of this POC color-based diagnostic test for self-screening/self-monitoring of anemia. TRIAL REGISTRATION. Not applicable. FUNDING. This work was funded by the FDA-funded Atlantic Pediatric Device Consortium, the Georgia Research Alliance, Children's Healthcare of Atlanta, the Georgia Center of Innovation for Manufacturing, and the InVenture Prize and Ideas to Serve competitions at the Georgia Institute of Technology.
Journal of Clinical Investigation 08/2014; · 13.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ponatinib is the only currently approved tyrosine kinase inhibitor (TKI) that suppresses all BCR-ABL1 single mutants in Philadelphia chromosome-positive (Ph+) leukemia, including the recalcitrant BCR-ABL1T315I mutant. However, emergence of compound mutations in a BCR-ABL1 allele may confer ponatinib resistance. We found that clinically reported BCR-ABL1 compound mutants center on 12 key positions and confer varying resistance to imatinib, nilotinib, dasatinib, ponatinib, rebastinib, and bosutinib. T315I-inclusive compound mutants confer high-level resistance to TKIs, including ponatinib. In vitro resistance profiling was predictive of treatment outcomes in Ph+ leukemia patients. Structural explanations for compound mutation-based resistance were obtained through molecular dynamics simulations. Our findings demonstrate that BCR-ABL1 compound mutants confer different levels of TKI resistance, necessitating rational treatment selection to optimize clinical outcome.
[Show abstract][Hide abstract] ABSTRACT: The mitochondrial pyruvate dehydrogenase complex (PDC) plays a crucial role in regulation of glucose homoeostasis in mammalian cells. PDC flux depends on catalytic activity of the most important enzyme component pyruvate dehydrogenase (PDH). PDH kinase (PDK) inactivates PDC by phosphorylating PDH at specific serine residues including S293, while dephosphorylation of PDH by PDH phosphatase (PDP) restores PDC activity. The current understanding suggests that S293 phosphorylation of PDH impedes active site accessibility to its substrate pyruvate. Here we report that phosphorylation of a tyrosine residue Y301 also inhibits PDHA1 by blocking pyruvate binding through an independent mechanism in addition to S293 phosphorylation. In addition, we found that multiple oncogenic tyrosine kinases directly phosphorylate PDHA1 at Y301, and Y301 phosphorylation of PDHA1 is common in EGF-stimulated cells as well as diverse human cancer cells and primary leukemia cells from human patients. Moreover, expression of a phosphorylation-deficient PDHA1 Y301F mutant in cancer cells resulted in increased oxidative phosphorylation, decreased cell proliferation under hypoxia, and reduced tumor growth in mice. Together, our findings suggest that phosphorylation at distinct serine and tyrosine residues inhibits PDHA1 through distinct mechanisms to impact active site accessibility, which act in concert to regulate PDC activity and promote the Warburg effect.
Journal of Biological Chemistry 08/2014; · 4.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although the oxidative pentose phosphate pathway is important for tumor growth, how 6-phosphogluconate dehydrogenase (6PGD) in this pathway is upregulated in human cancers is unknown. We found that 6PGD is commonly activated in EGF-stimulated cells and human cancer cells by lysine acetylation. Acetylation at K76 and K294 of 6PGD promotes NADP(+) binding to 6PGD and formation of active 6PGD dimers, respectively. Moreover, we identified DLAT and ACAT2 as upstream acetyltransferases of K76 and K294, respectively, and HDAC4 as the deacetylase of both sites. Expressing acetyl-deficient mutants of 6PGD in cancer cells significantly attenuated cell proliferation and tumor growth. This is due in part to reduced levels of 6PGD products ribulose-5-phosphate and NADPH, which led to reduced RNA and lipid biosynthesis as well as elevated ROS. Furthermore, 6PGD activity is upregulated with increased lysine acetylation in primary leukemia cells from human patients, providing mechanistic insights into 6PGD upregulation in cancer cells.
[Show abstract][Hide abstract] ABSTRACT: Many cancer cells rely more on aerobic glycolysis (the Warburg effect) than mitochondrial oxidative phosphorylation and catabolize glucose at a high rate. Such a metabolic switch is suggested to be due in part to functional attenuation of mitochondria in cancer cells. However, how oncogenic signals attenuate mitochondrial function and promote the switch to glycolysis remains unclear. We previously reported that tyrosine phosphorylation activates and inhibits mitochondrial pyruvate dehydrogenase kinase (PDK) and phosphatase (PDP), respectively, leading to enhanced inhibitory serine phosphorylation of pyruvate dehydrogenase (PDH) and consequently inhibition of pyruvate dehydrogenase complex (PDC) in cancer cells. In particular, Y381 phosphorylation of PDP1 dissociates deacetylase SIRT3 and recruits acetyltransferase ACAT1 to PDC, resulting in increased inhibitory lysine acetylation of PDHA1 and PDP1. Here we report that phosphorylation at another tyrosine residue, Y94, inhibits PDP1 by reducing the binding ability of PDP1 to lipoic acid, which is covalently attached to the L2 domain of dihydrolipoyl acetyl-transferase (E2) to recruit PDP1 to PDC. We found that multiple oncogenic tyrosine kinases directly phosphorylated PDP1 at Y94, and Y94 phosphorylation of PDP1 was common in diverse human cancer cells and primary leukemia cells from patients. Moreover, expression of a phosphorylation-deficient PDP1 Y94F mutant in cancer cells resulted in increased oxidative phosphorylation, decreased cell proliferation under hypoxia, and reduced tumor growth in mice. Together, our findings suggest that phosphorylation at different tyrosine residues inhibits PDP1 through independent mechanisms, which act in concert to regulate PDC activity and promote the Warburg effect.
Journal of Biological Chemistry 06/2014; · 4.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ABSTRACT The therapeutic landscape of chronic-phase chronic myeloid leukemia (CP-CML) has truly been revolutionized with the advent of BCR-ABL1 tyrosine-kinase inhibitor (TKI) therapy. First-line therapy with the TKI imatinib has produced high rates of remissions among treatment-naive patients, as well as patients previously treated with interferon. However, imatinib resistance and intolerance remain significant clinical challenges. Dasatinib, nilotinib, bosutinib, and ponatinib are more recently developed TKIs that have been shown to be very effective as second- or later-line treatment for CML after imatinib failure. Dasatinib and nilotinib are also approved for use in newly diagnosed patients with CP-CML, and produce faster responses when compared with first-line imatinib. Resistance or intolerance can occur with any of the currently available TKIs, necessitating a change to an alternate TKI or consideration of allogeneic hematopoietic stem cell transplant. Treatment options and outcomes for patients whose first-line therapy has failed are reviewed in depth in this article.
Leukemia and Lymphoma 06/2014; · 2.61 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose
Hematopoietic stem cell transplantation (HSCT) is the mainstay of treatment for adults with acute leukemia. Total body irradiation (TBI) remains an important part of the conditioning regimen for HCST. For those patients unable to tolerate myeloablative TBI (mTBI), reduced intensity TBI (riTBI) is commonly used. In this study we compared outcomes of patients undergoing mTBI with those of patients undergoing riTBI in our institution.
Methods and Materials
We performed a retrospective review of all patients with acute leukemia who underwent TBI-based conditioning, using a prospectively acquired database of HSCT patients treated at our institution. Patient data including details of the transplantation procedure, disease status, Karnofsky performance status (KPS), response rates, toxicity, survival time, and time to progression were extracted. Patient outcomes for various radiation therapy regimens were examined. Descriptive statistical analysis was performed.
Between June 1985 and July 2012, 226 patients with acute leukemia underwent TBI as conditioning for HSCT. Of those patients, 180 had full radiation therapy data available; 83 had acute lymphoblastic leukemia and 94 had acute myelogenous leukemia; 45 patients received riTBI, and 135 received mTBI. Median overall survival (OS) was 13.7 months. Median relapse-free survival (RFS) for all patients was 10.2 months. Controlling for age, sex, KPS, disease status, and diagnosis, there were no significant differences in OS or RFS between patients who underwent riTBI and those who underwent mTBI (P=.402, P=.499, respectively). Median length of hospital stay was shorter for patients who received riTBI than for those who received mTBI (16 days vs 23 days, respectively; P<.001), and intensive care unit admissions were less frequent following riTBI than mTBI (2.22% vs 12.69%, respectively, P=.043). Nonrelapse survival rates were also similar (P=.186).
No differences in OS or RFS were seen between all patients undergoing riTBI and those undergoing mTBI, despite older age and potential increased comorbidity of riTBI patients. riTBI regimens were associated with shorter length of hospital stay, fewer intensive care unit admissions, and similar rates of nonrelapse survival, which may reflect reduced toxicity. Prospective trials comparing riTBI and mTBI are warranted.
International journal of radiation oncology, biology, physics 06/2014; 89(2):360–369. · 4.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Bosutinib is an oral tyrosine kinase inhibitor (TKI) with very potent dual inhibitory activity against SRC and abelson gene. Bosutinib was approved in 2012 for the treatment of resistant Philadelphia chromosome positive chronic myeloid leukemia (CML). Bosutinib is a very effective TKI against all phases of intolerant or resistant CML regardless of the presence or absence of an abelson gene domain mutation, except for cases with detectable T315I or V299L. Bosutinib is overall well tolerated and associated with a unique, but manageable toxicity profile. Factors that influence the prescribing pattern of this drug are complex and include physicians', and increasingly patients and families' preference, patients' comorbid conditions, schedule of administration, as well as financial factors. This paper provides an overview of CML, the TKI market, pharmacokinetics, pharmacodynamics, clinical efficacy, safety and tolerability of bosutinib.
Expert Review of Anticancer Therapy 05/2014; · 3.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Bosutinib is an orally active, dual Src/Abl tyrosine kinase inhibitor for treatment of chronic myeloid leukemia (CML) following resistance/intolerance to prior therapy. Here we report the data from the 2-year follow-up of a phase 1/2 open-label study evaluating the efficacy and safety of bosutinib as second-line therapy in 288 patients with chronic phase CML resistant (n = 200) or intolerant (n = 88) to imatinib. The cumulative response rates to bosutinib were as follows: 85% achieved/maintained complete hematologic response, 59% achieved/maintained major cytogenetic response (including 48% with complete cytogenetic response), and 35% achieved major molecular response. Responses were durable, with 2-year estimates of retaining response >70%. Two-year probabilities of progression-free survival and overall survival were 81% and 91%, respectively. The most common toxicities were primarily gastrointestinal adverse events (diarrhea [84%], nausea [45%], vomiting [37%]), which were primarily mild to moderate, typically transient, and first occurred early during treatment. Thrombocytopenia was the most common grade 3/4 hematologic laboratory abnormality (24%). Outcomes were generally similar among imatinib-resistant and imatinib-intolerant patients and did not differ with age. The longer-term results of the present analysis confirm that bosutinib is an effective and tolerable second-line therapy for patients with imatinib-resistant or imatinib-intolerant chronic phase CML.
American Journal of Hematology 04/2014; · 3.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ABSTRACT Omacetaxine mepesuccinate promotes apoptosis by inhibiting production of short-lived oncoproteins. The efficacy and safety of omacetaxine in patients with advanced chronic myeloid leukemia (CML) previously treated with tyrosine kinase inhibitors were assessed in two phase II trials (CML-202 and CML-203). Fifty-five patients in accelerated phase (AP-CML) and 44 in myeloid blast phase (BP-CML) received subcutaneous omacetaxine 1.25 mg/m(2) BID days 1-14 every 28 days until hematologic response/improvement or any cytogenetic response, then days 1-7 every 28 days until disease progression. The primary endpoint was maintenance or attainment of major hematologic response (MHR); cytogenetic responses were also evaluated. MHR was 37% in patients with AP-CML and 9% with BP-CML (22% and 5% in those with a history of T315I). Most grade 3/4 adverse events were related to myelosuppression, and were generally manageable. Omacetaxine demonstrates activity and an acceptable safety profile in pretreated patients with advanced CML, irrespective of mutational status.