Tetrameric Acetyl-CoA Acetyltransferase 1 Is Important for Tumor Growth.

Mitochondrial acetyl-CoA acetyltransferase 1 (ACAT1) regulates pyruvate dehydrogenase complex (PDC) by acetylating pyruvate dehydrogenase (PDH) and PDH phosphatase. How ACAT1 is "hijacked" to contribute to the Warburg effect in human cancer remains unclear. We found that active, tetrameric ACAT1 is commonly upregulated in cells stimulated by EGF and in diverse human cancer cells, where ACAT1 tetramers, but not monomers, are phosphorylated and stabilized by enhanced Y407 phosphorylation. Moreover, we identified arecoline hydrobromide (AH) as a covalent ACAT1 inhibitor that binds to and disrupts only ACAT1 tetramers. The resultant AH-bound ACAT1 monomers cannot reform tetramers. Inhibition of tetrameric ACAT1 by abolishing Y407 phosphorylation or AH treatment results in decreased ACAT1 activity, leading to increased PDC flux and oxidative phosphorylation with attenuated cancer cell proliferation and tumor growth. These findings provide a mechanistic understanding of how oncogenic events signal through distinct acetyltransferases to regulate cancer metabolism and suggest ACAT1 as an anti-cancer target.

Metabolic Rewiring by Oncogenic BRAF V600E Links Ketogenesis Pathway to BRAF-MEK1 Signaling.

Many human cancers share similar metabolic alterations, including the Warburg effect. However, it remains unclear whether oncogene-specific metabolic alterations are required for tumor development. Here we demonstrate a "synthetic lethal" interaction between oncogenic BRAF V600E and a ketogenic enzyme 3-hydroxy-3-methylglutaryl-CoA lyase (HMGCL). HMGCL expression is upregulated in BRAF V600E-expressing human primary melanoma and hairy cell leukemia cells. Suppression of HMGCL specifically attenuates proliferation and tumor growth potential of human melanoma cells expressing BRAF V600E. Mechanistically, active BRAF upregulates HMGCL through an octamer transcription factor Oct-1, leading to increased intracellular levels of HMGCL product, acetoacetate, which selectively enhances binding of BRAF V600E but not BRAF wild-type to MEK1 in V600E-positive cancer cells to promote activation of MEK-ERK signaling. These findings reveal a mutation-specific mechanism by which oncogenic BRAF V600E "rewires" metabolic and cell signaling networks and signals through the Oct-1-HMGCL-acetoacetate axis to selectively promote BRAF V600E-dependent tumor development.

Tyr phosphorylation of PDP1 toggles recruitment between ACAT1 and SIRT3 to regulate the pyruvate dehydrogenase complex.

Mitochondrial pyruvate dehydrogenase complex (PDC) is crucial for glucose homeostasis in mammalian cells. The current understanding of PDC regulation involves inhibitory serine phosphorylation of pyruvate dehydrogenase (PDH) by PDH kinase (PDK), whereas dephosphorylation of PDH by PDH phosphatase (PDP) activates PDC. Here, we report that lysine acetylation of PDHA1 and PDP1 is common in epidermal growth factor (EGF)-stimulated cells and diverse human cancer cells. K321 acetylation inhibits PDHA1 by recruiting PDK1, and K202 acetylation inhibits PDP1 by dissociating its substrate PDHA1, both of which are important in promoting glycolysis in cancer cells and consequent tumor growth. Moreover, we identified mitochondrial ACAT1 and SIRT3 as the upstream acetyltransferase and deacetylase, respectively, of PDHA1 and PDP1, while knockdown of ACAT1 attenuates tumor growth. Furthermore, Y381 phosphorylation of PDP1 dissociates SIRT3 and recruits ACAT1 to PDC. Together, hierarchical, distinct posttranslational modifications act in concert to control molecular composition of PDC and contribute to the Warburg effect.

Lysine acetylation activates 6-phosphogluconate dehydrogenase to promote tumor growth.

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.

Safety and survival outcomes for bloodless transplantation in patients with myeloma.

High-dose therapy (HDT) and autologous stem cell transplantation (ASCT) are established components in the treatment of multiple myeloma; however, undergoing transplantation usually requires hematopoietic support, which poses a challenge among patients who are unwilling to receive blood products. Most transplant centers decline HDT/ASCT to these patients because of safety concerns. Here, the authors' institutional data on safety, engraftment parameters, and survival outcomes after bloodless ASCT (BL-ASCT) are examined among patients with myeloma. This retrospective case-control study included patients who underwent BL-ASCT and Transfusion-supported ASCT (TS-ASCT) at Emory University Hospital between August 2006 and August 2016. In total, 24 patients who underwent BL-ASCT and 70 who underwent TS-ASCT were included. The median time for neutrophil engraftment, platelet engraftment and the median length of hospital stay all were equivalent for both groups. There were no transplant-related cardiovascular complications or mortality in either the BL-ASCT group or the TS-ASCT group. The median progression-free survival was 36 months and 44 months in the BL-ASCT and TS-ASCT groups, respectively (P = .277), and the median OS was not reached in either group at a median follow-up of 59 months after ASCT (P = .627). There was no transplant-related mortality at the 100-day or 1-year mark in either group. BL-ASCT is safe and feasible; transplant-related mortality, cardiovascular and hematologic complications are similar to those associated with TS-ASCT. Furthermore, BL-ASCT can yield similar engraftment and survival parameters comparable to those observed with TS-ASCT.

HMG-CoA synthase 1 is a synthetic lethal partner of BRAFV600E in human cancers.

Contributions of metabolic changes to cancer development and maintenance have received increasing attention in recent years. Although many human cancers share similar metabolic alterations, it remains unclear whether oncogene-specific metabolic alterations are required for tumor development. Using an RNAi-based screen targeting the majority of the known metabolic proteins, we recently found that oncogenic BRAFV600E up-regulates HMG-CoA lyase (HMGCL), which converts HMG-CoA to acetyl-CoA and a ketone body, acetoacetate, that selectively enhances BRAFV600E-dependent MEK1 activation in human cancer. Here, we identified HMG-CoA synthase 1 (HMGCS1), the upstream ketogenic enzyme of HMGCL, as an additional "synthetic lethal" partner of BRAFV600E Although HMGCS1 expression did not correlate with BRAFV600E mutation in human melanoma cells, HMGCS1 was selectively important for proliferation of BRAFV600E-positive melanoma and colon cancer cells but not control cells harboring active N/KRAS mutants, and stable knockdown of HMGCS1 only attenuated colony formation and tumor growth potential of BRAFV600E melanoma cells. Moreover, cytosolic HMGCS1 that co-localized with HMGCL and BRAFV600E was more important than the mitochondrial HMGCS2 isoform in BRAFV600E-expressing cancer cells in terms of acetoacetate production. Interestingly, HMGCL knockdown did not affect HMGCS1 expression levels, whereas HMGCS1 knockdown caused a compensating increase in HMGCL protein level because of attenuated protein degradation. However, this increase did not reverse the reduced ketogenesis in HMGCS1 knockdown cells. Mechanistically, HMGCS1 inhibition decreased intracellular acetoacetate levels, leading to reduced BRAFV600E-MEK1 binding and consequent MEK1 activation. We conclude that the ketogenic HMGCS1-HMGCL-acetoacetate axis may represent a promising therapeutic target for managing BRAFV600E-positive human cancers.

Upper gastrointestinal acute graft-versus-host disease adds minimal prognostic value in isolation or with other graft-versus-host disease symptoms as currently diagnosed and treated.

Upper gastrointestinal acute graft-versus-host disease is reported in approximately 30% of hematopoietic stem cell transplant recipients developing acute graft-versus-host disease. Currently classified as Grade II in consensus criteria, upper gastrointestinal acute graft-versus-host disease is often treated with systemic immunosuppression. We reviewed the Center for International Blood and Marrow Transplant Research database to assess the prognostic implications of upper gastrointestinal acute graft-versus-host disease in isolation or with other acute graft-versus-host disease manifestations. 8567 adult recipients of myeloablative allogeneic hematopoietic stem cell transplant receiving T-cell replete grafts for acute leukemia, chronic myeloid leukemia or myelodysplastic syndrome between 2000 and 2012 were analyzed. 51% of transplants were from unrelated donors. Reported upper gastrointestinal acute graft-versus-host disease incidence was 12.1%; 2.7% of recipients had isolated upper gastrointestinal acute graft-versus-host disease, of whom 95% received systemic steroids. Patients with isolated upper gastrointestinal involvement had similar survival, disease-free survival, transplant-related mortality, and relapse as patients with Grades 0, I, or II acute graft-versus-host disease. Unrelated donor recipients with isolated upper gastrointestinal acute graft-versus-host disease had less subsequent chronic graft-versus-host disease than those with Grades I or II disease (P=0.016 and P=0.0004, respectively). Upper gastrointestinal involvement added no significant prognostic information when present in addition to other manifestations of Grades I or II acute graft-versus-host disease. If upper gastrointestinal symptoms were reclassified as Grade 0 or I, 425 of 2083 patients (20.4%) with Grade II disease would be downgraded, potentially impacting the interpretation of clinical trial outcomes. Defining upper gastrointestinal acute graft-versus-host disease as a Grade II entity, as it is currently diagnosed and treated, is not strongly supported by this analysis. The general approach to diagnosis, treatment and grading of upper gastrointestinal symptoms and their impact on subsequent acute graft-versus-host disease therapy warrants reevaluation.

Immune responses and long-term disease recurrence status after telomerase-based dendritic cell immunotherapy in patients with acute myeloid leukemia.

BACKGROUND: Telomerase activity in leukemic blasts frequently is increased among patients with high-risk acute myeloid leukemia (AML). In the current study, the authors evaluated the feasibility, safety, immunogenicity, and therapeutic potential of human telomerase reverse transcriptase (hTERT)-expressing autologous dendritic cells (hTERT-DCs) in adult patients with AML. METHODS: hTERT-DCs were produced from patient-specific leukapheresis, electroporated with an mRNA-encoding hTERT and a lysosomal-targeting sequence, and cryopreserved. A total of 22 patients with a median age of 58 years (range, 30-75 years) with intermediate-risk or high-risk AML in first or second complete remission (CR) were enrolled. hTERT-DCs were generated for 24 patients (73%). A median of 17 intradermal vaccinations (range, 6-32 intradermal vaccinations) containing 1×107 cells were administered as 6 weekly injections followed by 6 biweekly injections. A total of 21 patients (16 in first CR, 3 in second CR, and 2 with early disease recurrence) received hTERT-DCs. RESULTS: hTERT-DCs were well tolerated with no severe toxicities reported, with the exception of 1 patient who developed idiopathic thrombocytopenic purpura. Of the 19 patients receiving hTERT-DCs in CR, 11 patients (58%) developed hTERT-specific T-cell responses that primarily were targeted toward hTERT peptides with predicted low human leukocyte antigen (HLA)-binding affinities. With a median follow-up of 52 months, 58% of patients in CR (11 of 19 patients) were free of disease recurrence at the time of their last follow-up visit; 57% of the patients who were aged ≥60 years (4 of 7 patients) also were found to be free of disease recurrence at a median follow-up of 54 months. CONCLUSIONS: The generation of hTERT-DCs is feasible and vaccination with hTERT-DCs appears to be safe and may be associated with favorable recurrence-free survival. Cancer 2017;123:3061-72. © 2017 American Cancer Society.

Allogeneic transplantation for advanced acute myeloid leukemia: The value of complete remission.

BACKGROUND: Patients with acute myeloid leukemia (AML) without complete remission (CR) or in first relapse (Rel1) can have extended leukemia control and survival after allogeneic hematopoietic cell transplantation (HCT). For patients in Rel1 or primary induction failure (PIF), transplantation versus treatment to achieve a second CR (CR2) and subsequent HCT might yield similar outcomes, but available comparative data are scarce. METHODS: Survival was analyzed in 4682 HCT recipients according to disease status: PIF (N = 1440), Rel1 (failing ≥1 reinduction; N = 1256), and CR2 (N = 1986). RESULTS: Patient, disease, and transplantation characteristics were similar, except that patients in CR2 more often had performance scores of 90% to 100%, de novo AML, and longer CR1 duration. Adverse cytogenetics were more common in patients who experienced PIF. The 5-year survival rate adjusted for performance score, cytogenetic risk, and donor type for CR2 was 39% (95% confidence interval [CI], 37%-41%) compared with 18% (95% CI, 16%-20%) for HCT in Rel1 and 21% (95% CI, 19%-23%) in PIF (P < .0001). CONCLUSIONS: Although survival is superior for patients who undergo HCT in CR2, transplantation for selected patients in Rel1 or PIF may still be valuable. These data can guide decision making about additional salvage therapy versus prompt HCT for patients not in CR, but they also highlight that AML is intrinsically more treatable in patients who have favorable-risk cytogenetics, those with longer CR1 duration, and younger patients with better performance status. Cancer 2017;123:2025-2034. © 2017 American Cancer Society.

CMV reactivation drives posttransplant T-cell reconstitution and results in defects in the underlying TCRß repertoire.

Although cytomegalovirus (CMV) reactivation has long been implicated in posttransplant immune dysfunction, the molecular mechanisms that drive this phenomenon remain undetermined. To address this, we combined multiparameter flow cytometric analysis and T-cell subpopulation sorting with high-throughput sequencing of the T-cell repertoire, to produce a thorough evaluation of the impact of CMV reactivation on T-cell reconstitution after unrelated-donor hematopoietic stem cell transplant. We observed that CMV reactivation drove a >50-fold specific expansion of Granzyme B(high)/CD28(low)/CD57(high)/CD8(+) effector memory T cells (Tem) and resulted in a linked contraction of all naive T cells, including CD31(+)/CD4(+) putative thymic emigrants. T-cell receptor ß (TCRß) deep sequencing revealed a striking contraction of CD8(+) Tem diversity due to CMV-specific clonal expansions in reactivating patients. In addition to querying the topography of the expanding CMV-specific T-cell clones, deep sequencing allowed us, for the first time, to exhaustively evaluate the underlying TCR repertoire. Our results reveal new evidence for significant defects in the underlying CD8 Tem TCR repertoire in patients who reactivate CMV, providing the first molecular evidence that, in addition to driving expansion of virus-specific cells, CMV reactivation has a detrimental impact on the integrity and heterogeneity of the rest of the T-cell repertoire. This trial was registered at www.clinicaltrials.gov as #NCT01012492.

Improved survival after acute graft-versus-host disease diagnosis in the modern era.

A cute graft-versus-host disease remains a major threat to a successful outcome after allogeneic hematopoietic cell transplantation. While improvements in treatment and supportive care have occurred, it is unknown whether these advances have resulted in improved outcome specifically among those diagnosed with acute graft-versus-host disease. We examined outcome following diagnosis of grade II-IV acute graft-versus-host disease according to time period, and explored effects according to original graft-versus-host disease prophylaxis regimen and maximum overall grade of acute graft-versus-host disease. Between 1999 and 2012, 2,905 patients with acute myeloid leukemia (56%), acute lymphoblastic leukemia (30%) or myelodysplastic syndromes (14%) received a sibling (24%) or unrelated donor (76%) blood (66%) or marrow (34%) transplant and developed grade II-IV acute graft-versus-host disease (n=497 for 1999-2001, n=962 for 2002-2005, n=1,446 for 2006-2010). The median (range) follow-up was 144 (4-174), 97 (4-147) and 60 (8-99) months for 1999-2001, 2002-2005, and 2006-2010, respectively. Among the cohort with grade II-IV acute graft-versus-host disease, there was a decrease in the proportion of grade III-IV disease over time with 56%, 47%, and 37% for 1999-2001, 2002-2005, and 2006-2012, respectively (P<0.001). Considering the total study population, univariate analysis demonstrated significant improvements in overall survival and treatment-related mortality over time, and deaths from organ failure and infection declined. On multivariate analysis, significant improvements in overall survival (P=0.003) and treatment-related mortality (P=0.008) were only noted among those originally treated with tacrolimus-based graft-versus-host disease prophylaxis, and these effects were most apparent among those with overall grade II acute graft-versus-host disease. In conclusion, survival has improved over time for tacrolimus-treated transplant recipients with acute graft-versus-host disease.

Allogeneic Hematopoietic Cell Transplantation for Patients with Mixed Phenotype Acute Leukemia.

Acute biphenotypic leukemias or mixed phenotype acute leukemias (MPAL) are rare and considered high risk. The optimal treatment and the role of allogeneic hematopoietic stem cell transplantation (alloHCT) are unclear. Most prior case series include only modest numbers of patients who underwent transplantation. We analyzed the outcome of 95 carefully characterized alloHCT patients with MPAL reported to the Center for International Blood and Marrow Transplant Research between 1996 and 2012. The median age was 20 years (range, 1 to 68). Among the 95 patients, 78 were in first complete remission (CR1) and 17 were in second complete remission (CR2). Three-year overall survival (OS) of 67% (95% confidence interval [CI], 57 to 76), leukemia-free survival of 56% (95% CI, 46 to 66), relapse incidence of 29% (95% CI, 20 to 38), and nonrelapse mortality of 15% (95% CI, 9 to 23) were encouraging. OS was best in younger patients (<20 years), but no significant differences were observed between those 20 to 40 years of age and those who were 40 years or older. A matched-pair analysis showed similar outcomes comparing MPAL cases to 375 acute myelogenous leukemia or 359 acute lymphoblastic leukemia cases. MPAL patients had more acute and a trend for more chronic graft-versus-host disease. No difference was observed between patients who underwent transplantation in CR1 versus those who underwent transplantation in CR2. AlloHCT is a promising treatment option for pediatric and adult patients with MPAL with encouraging long-term survival.

Factors influencing long-term efficacy and tolerability of bosutinib in chronic phase chronic myeloid leukaemia resistant or intolerant to imatinib.

The dual SRC/ABL1 tyrosine kinase inhibitor bosutinib is indicated for adults with Ph+ chronic myeloid leukaemia (CML) resistant/intolerant to prior therapy. This analysis of an ongoing phase 1/2 study (NCT00261846) assessed effects of baseline patient characteristics on long-term efficacy and safety of bosutinib 500 mg/day in adults with imatinib (IM)-resistant (IM-R; n = 196)/IM-intolerant (IM-I; n = 90) chronic phase (CP) CML. Median treatment duration was 24·8 months (median follow-up, 43·6 months). Cumulative major cytogenetic response (MCyR) rate [95% confidence interval (CI)], was 59% (53-65%); Kaplan-Meier (KM) probability of maintaining MCyR at 4 years was 75% (66-81%). Cumulative incidence of on-treatment progression/death at 4 years was 19% (95% CI, 15-24%); KM 2-year overall survival was 91% (87-94%). Significant baseline predictors of both MCyR and complete cytogenetic response (newly attained/maintained from baseline) at 3 and 6 months included prior IM cytogenetic response, baseline MCyR, prior interferon therapy and <6 months duration from diagnosis to IM treatment initiation and no interferon treatment before IM. The most common adverse event (AE) was diarrhoea (86%). Baseline bosutinib-sensitive BCR-ABL1 mutation was the only significant predictor of grade 3/4 diarrhoea; no significant predictors were identified for liver-related AEs. Bosutinib demonstrates durable efficacy and manageable toxicity in IM-R/IM-I CP-CML patients.

Long-term bosutinib for chronic phase chronic myeloid leukemia after failure of imatinib plus dasatinib and/or nilotinib.

Bosutinib is an Src/Abl tyrosine kinase inhibitor (TKI) indicated for adults with Ph+ chronic myeloid leukemia (CML) resistant/intolerant to prior TKIs. This long-term update of an ongoing phase 1/2 study evaluated the efficacy and safety of third-/fourth-line bosutinib in adults with chronic phase (CP) CML. Median durations of treatment and follow-up were 8.6 (range, 0.2-87.7) months and 32.7 (0.3-93.3) months, respectively. Cumulative confirmed complete hematologic response (cCHR) and major cytogenetic response (MCyR) rates were 74% (95% CI, 65-81%) and 40% (31-50%), respectively; Kaplan-Meier (K-M) probability of maintaining cCHR or MCyR at 4 years was 63% (95% CI, 50-73%) and 69% (52-81%). Cumulative incidence of on-treatment disease progression (PD)/death at 4 years was 24% (95% CI, 17-33%); K-M 4-year overall survival was 78% (68-85%). Baseline Ph+ cells ≤35 vs. ≥95% was prognostic of MCyR and CCyR by 3 and 6 months, increased baseline basophils was prognostic of PD/death, and no prior response to second-line TKI was prognostic of death. Common adverse events included diarrhea (83%), nausea (48%), vomiting (38%), and thrombocytopenia (39%). Bosutinib demonstrates durable efficacy and a toxicity profile similar to previous bosutinib studies in CP CML patients resistant/intolerant to multiple TKIs, representing an important treatment option for patients in this setting. This trial is registered at www.clinicaltrials.gov (NCT00261846). Am. J. Hematol. 91:1206-1214, 2016. © 2016 Wiley Periodicals, Inc.

Tyr-301 phosphorylation inhibits pyruvate dehydrogenase by blocking substrate binding and promotes the Warburg effect.

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 inactivates PDC by phosphorylating PDH at specific serine residues, including Ser-293, whereas dephosphorylation of PDH by PDH phosphatase restores PDC activity. The current understanding suggests that Ser-293 phosphorylation of PDH impedes active site accessibility to its substrate pyruvate. Here, we report that phosphorylation of a tyrosine residue Tyr-301 also inhibits PDH α 1 (PDHA1) by blocking pyruvate binding through a novel mechanism in addition to Ser-293 phosphorylation. In addition, we found that multiple oncogenic tyrosine kinases directly phosphorylate PDHA1 at Tyr-301, and Tyr-301 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.

Tyr-94 phosphorylation inhibits pyruvate dehydrogenase phosphatase 1 and promotes tumor growth.

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, Tyr-381 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, Tyr-94, inhibits PDP1 by reducing the binding ability of PDP1 to lipoic acid, which is covalently attached to the L2 domain of dihydrolipoyl acetyltransferase (E2) to recruit PDP1 to PDC. We found that multiple oncogenic tyrosine kinases directly phosphorylated PDP1 at Tyr-94, and Tyr-94 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.

Long-term efficacy and safety of bosutinib in patients with advanced leukemia following resistance/intolerance to imatinib and other tyrosine kinase inhibitors.

Long-term efficacy and safety of bosutinib (≥4 years follow-up from last enrolled patient) were evaluated in an ongoing phase 1/2 study in the advanced leukemia cohort with prior treatment failure (accelerated-phase [AP, n = 79] chronic myeloid leukemia [CML], blast-phase [BP, n = 64] CML, acute lymphoblastic leukemia [ALL, n = 24]). Fourteen AP, 2 BP, and 1 ALL patient remained on bosutinib at 4 years (vs. 38, 8, 1 at 1 year); median (range) treatment durations: 10.2 (0.1-88.6), 2.8 (0.03-55.9), 0.97 (0.3-89.2) months. Among AP and BP patients, 57% and 28% newly attained or maintained baseline overall hematologic response (OHR); 40% and 37% attained/maintained major cytogenetic response (MCyR) by 4 years (most by 12 months). In responders at 1 versus 4 years, Kaplan-Meier (KM) probabilities of maintaining OHR were 78% versus 49% (AP) and 28% versus 19% (BP); KM probabilities of maintaining MCyR were 65% versus 49% (AP) and 21% versus 21% (BP). Most common AEs (AP, BP) were gastrointestinal (96%; 83%), primarily diarrhea (85%; 64%), which was typically low grade (maximum grade 1/2: 81%; 59%) and transient; no patient discontinued due to diarrhea. Serious AEs occurred in 44 (56%) AP and 37 (58%) BP patients, most commonly pneumonia (n = 9) for AP and pyrexia (n = 6) for BP; 11 and 13 died within 30 days of last dose (2 considered bosutinib-related [AP] per investigator). Responses were durable in ∼50% AP responders at 4 years (∼25% BP patients responded at year 1, suggesting possible bridge-to-transplant role in BP patients); toxicity was manageable.

Mobilization of hematopoietic progenitors from normal donors using the combination of granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor results in fewer plasmacytoid dendritic cells in the graft and enhanced donor T cell engraftment with Th1 polarization: results from a randomized clinical trial.

Granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) both mobilize CD34(+) stem cells into the blood when administered before apheresis but have distinct effects on dendritic cell (DC) differentiation. We previously demonstrated that the combination of GM+G-CSF results in fewer plasmacytoid DCs (pDCs) when used to mobilize peripheral blood stem cells for autologous transplantation. To test the hypothesis that the content of pDCs in an allograft can be modulated with the cytokines used for mobilization, we randomized the human leukocyte antigen-matched sibling donors of 50 patients with hematological malignancies to a mobilization regimen of either GM+G-CSF (n = 25) or G-CSF alone (n = 25). Primary and secondary endpoints included the cellular constituents of the mobilized grafts, the kinetics of posttransplantation immune reconstitution, and clinical outcomes of the transplantation recipients. Grafts from donors receiving GM+G-CSF contained equivalent numbers of CD34(+) cells with fewer pDCs and T cells, with a higher fraction of Th1-polarized donor T cells than G-CSF mobilized grafts. Immune recovery was enhanced among recipients of GM+G-CSF. Survival was not significantly different between transplantation recipients in the two arms. The use of GM+G-CSF modulates immune function and recovery after allogeneic transplantation and should be explored in larger studies powered to evaluate clinical outcomes.

In vivo T cell costimulation blockade with abatacept for acute graft-versus-host disease prevention: a first-in-disease trial.

We performed a first-in-disease trial of in vivo CD28:CD80/86 costimulation blockade with abatacept for acute graft-versus-host disease (aGVHD) prevention during unrelated-donor hematopoietic cell transplantation (HCT). All patients received cyclosporine/methotrexate plus 4 doses of abatacept (10 mg/kg/dose) on days -1, +5, +14, +28 post-HCT. The feasibility of adding abatacept, its pharmacokinetics, pharmacodynamics, and its impact on aGVHD, infection, relapse, and transplantation-related mortality (TRM) were assessed. All patients received the planned abatacept doses, and no infusion reactions were noted. Compared with a cohort of patients not receiving abatacept (the StdRx cohort), patients enrolled in the study (the ABA cohort) demonstrated significant inhibition of early CD4(+) T cell proliferation and activation, affecting predominantly the effector memory (Tem) subpopulation, with 7- and 10-fold fewer proliferating and activated CD4(+) Tem cells, respectively, at day+28 in the ABA cohort compared with the StdRx cohort (P < .01). The ABA patients demonstrated a low rate of aGVHD, despite robust immune reconstitution, with 2 of 10 patients diagnosed with grade II-IV aGVHD before day +100, no deaths from infection, no day +100 TRM, and with 7 of 10 evaluable patients surviving (median follow-up, 16 months). These results suggest that costimulation blockade with abatacept can significantly affect CD4(+) T cell proliferation and activation post-transplantation, and may be an important adjunct to standard immunoprophylaxis for aGVHD in patients undergoing unrelated-donor HCT.

Epsilon aminocaproic acid prevents bleeding in severely thrombocytopenic patients with hematological malignancies.

BACKGROUND: Despite prophylactic platelet transfusions, bleeding remains a significant problem in thrombocytopenic patients. METHODS: The antifibrinolytic agent epsilon aminocaproic acid (EACA) was administered to 44 chronically (median duration, 273 days) and severely (platelet count, 8 × 10(9)/L; range, 1 × 10(9)/L-19 × 10(9)/L) thrombocytopenic patients with hematological malignancies. Prophylactic EACA at a dose of 1 g twice daily was orally administered for a median duration of 47 days (range, 7 days-209 days) until the platelet count recovered to > 30; × 10(9) /L. Platelets were only transfused if bleeding occurred. RESULTS: While receiving EACA, 59% of the patients did not bleed, 25% had 19 episodes of spontaneously resolving minor bleeding that did not require platelet transfusion, and 16% received a median of 4 platelet transfusions (range, 1 transfusion-8 transfusions) for 1 major traumatic and 9 spontaneous grade 2 to grade 3 bleeding (based on the World Health Organization classification of idiopathic thrombocytopenic purpura). No EACA toxicities were noted, and venous thromboses were not observed. CONCLUSIONS: EACA is well tolerated and is associated with a low risk of major bleeding in patients with hematological malignancies who are experiencing chronic severe thrombocytopenia.