Long-term survival and functional outcomes of critically ill patients with hematologic malignancies: a Canadian multicenter prospective study

PURPOSE

Patients with hematologic malignancy (HM) commonly develop critical illness. Their long-term survival and functional outcomes have not been well described.

METHODS

We conducted a prospective, observational study of HM patients admitted to seven Canadian intensive care units (ICUs) (2018-2020). We followed survivors at 7 days, 6 months and 12 months following ICU discharge. The primary outcome was 12-month survival. We evaluated functional outcomes at 6 and 12 months using the functional independent measure (FIM) and short form (SF)-36 as well as variables associated with 12-month survival.

RESULTS

We enrolled 414 patients including 35% women. The median age was 61 (interquartile range, IQR: 52-69), median Sequential Organ Failure Assessment (SOFA) score was 9 (IQR: 6-12), and 22% had moderate-severe frailty (clinical frailty scale [CFS] ≥ 6). 51% had acute leukemia, 38% lymphoma/multiple myeloma, and 40% had received a hematopoietic stem cell transplant (HCT). The most common reasons for ICU admission were acute respiratory failure (50%) and sepsis (40%). Overall, 203 (49%) were alive 7 days post-ICU discharge (ICU survivors). Twelve-month survival of the entire cohort was 21% (43% across ICU survivors). The proportion of survivors with moderate-severe frailty was 42% (at 7 days), 14% (6 months), and 8% (12 months). Median FIM at 7 days was 80 (IQR: 50-109). Physical function, pain, social function, mental health, and emotional well-being were below age- and sex-matched population scores at 6 and 12 months. Frailty, allogeneic HCT, kidney injury, and cardiac complications during ICU were associated with lower 12- month survival.

CONCLUSIONS

49% of all HM patients were alive at 7 days post-ICU discharge, and 21% at 12 months. Survival varied based upon hematologic diagnosis and frailty status. Survivors had important functional disability and impairment in emotional, physical, and general well-being.

Abstract 4833: Inhibiting the mitochondrial RNA degradosome complex SUV3 and PNPase increases dsRNA in the cytoplasm, triggers a viral mimicry response and kills AML cells and progenitors

Eukaryotic cells have two separate genomes; nuclear chromosomal DNA and circular mitochondrial DNA. Mitochondrial DNA lacks introns, and encodes 2 rRNAs, 22 t-RNAs and 13 of the 90 proteins that constitute the mitochondrial respiratory chain. To maintain homeostasis, mitochondrial RNA degradation machinery regulates RNA turnover. ATP-dependent helicase, SUV3 (gene SUPV3L1), and exonuclease PNPase (gene PNPT1) function as a complex to degrade mitochondrial dsRNA. By immunoblotting, PNPase and SUV3 proteins were increased in 7/7 AML patient samples and 13/13 of AML cell lines, compared to the normal hematopoietic cells. Analysis of the TARGET AML dataset revealed AML patients with increased expression of SUPV3L1 (p = 0.051, p= 0.045) and PNPT1 (p = 0.0013, p = 0.018) had decreased overall and event free survival. Genetic knockdown or knockout using shRNA or sgRNA against PNPT1 or SUPV3L1 decreased growth and viability of OCI-AML2, TEX, K562, U937, NB4 and OCI-AML 8227 cells. Furthermore, SUPV3L1 & PNPT1 ranked in the top 5.2% and 7.4% of essential genes in 26 leukemia cell lines in CRISPR screens and 2.7% and 4.9% in RNAi screens (depmap.org). Knockdown of PNPT1 & SUPV3L1 also reduced the clonogenic growth of OCI-AML2, TEX and U937 cells and significantly reduced engraftment of TEX cells into the marrow of immune deficient mice, demonstrating the functional importance on leukemia initiating cells in vivo. SUPV3L1 knockdown in primary AML cells reduced engraftment in marrow of immune deficient mice. Bioinformatics analysis to detect processes associated with PNPT1 and SUPV3L1, we identified associations with Response to exogenous dsRNA, Response to virus, and RNA catabolic process ontologies. Consistent with this, we observed knockdown of PNPT1 or SUPV3L1 increased expression of genes (INFgR1, ICAM, IRF7 & JAK/STAT) suggesting an interferon response. As PNPT1 and SUPV3L1 degrade mitochondrial dsRNA, we measured levels of dsRNA after knockdown of these genes. Knockdown of PNPT1 and SUPV3L1 in OCI-AML2 cells increased levels of cytoplasmic/mitochondrial dsRNA 3-4 fold compared to control. Knockdown of PNPT1 and SUPV3L1 also increased dsRNA in 143B cells, but not Rho (0) 143B cells that lack mitochondrial DNA. Upregulation of inflammatory genes leads to viral mimicry and can increase sensitivity to immune mediated killing. We observed enhanced sensitivity to Double Negative T (DNT) cells mediated killing in PNPT1 and SUPV3L1 knockdown OCI-AML2 cells compared to control cells. In summary, RNA degradosome complex proteins SUPV3L1 and PNPT1 are overexpressed in AML, and are essential for the survival of AML cells and AML stem/progenitors. These enzymes regulate levels of mitochondrial dsRNA, and their inhibition leads to increased cytoplasmic dsRNA triggering a viral mimicry response and enhanced sensitivity to immune-mediated killing.

Citation Format: Geethu Emily Thomas, Kazem Nouri, Jong Bok Lee, Rose Hurren, Yongran Yan, Neil MacLean, Yulia Jitkova, Li Ma, Xiao Ming Wang, Chaitra Sarathy, Andrea Arruda, Mark D. Minden, Li Zhang, Vito Spadavecchio, Aaron Schimmer. Inhibiting the mitochondrial RNA degradosome complex SUV3 and PNPase increases dsRNA in the cytoplasm, triggers a viral mimicry response and kills AML cells and progenitors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4833.

Mutational profile, outcomes, and impact of allogeneic hematopoietic stem cell transplantation in adult patients with acute myeloid leukemia and inconclusive cytogenetic analysis

BACKGROUND

Inconclusive cytogenetic analysis (IC) at baseline has been reported as a predictor of poor prognosis in patients with acute myeloid leukemia (AML). The mutational profile in this group of patients, and its impact on outcomes have not been reported.

METHODS

We retrospectively analyzed adult patients (≥18 years) with newly diagnosed AML treated with intensive induction chemotherapy between 2015 and 2019. Patients with any documented cytogenetic abnormalities were excluded. Targeted next generation sequencing (NGS) was performed in all patients. Baseline characteristics, mutation profile, and outcomes were compared between patients with normal cytogenetics(NC) and those with IC.

RESULTS

Sixty-one patients (males 39.3%; median age 59 years) had IC at diagnosis. The proportion of patients with mutations in genes with proven prognostic impact were not different between AML patients with IC and NC. AML patients with NC were more likely to harbor the prognostically favorable NPM1^mut /FLT3-ITD^wt mutational combination conferring "favorable" risk status. As a result, a larger proportion of patients in the IC group underwent allogeneic hematopoietic stem cell transplantation (allo HCT; 54.1% vs. 39.6%; p = .02). The 2-year RFS (55.9% vs. 58.5%; p = .29) and OS (61.9% vs. 66.9%; p = .48) were similar in IC and NC patients. There was no difference in survival of patients who underwent allo HCT when compared with patients who did not (p = .99).

CONCLUSIONS

Inconclusive cytogenetic analysis may not be an independent prognostic indicator in AML. In such patients, molecular abnormalities detected through NGS or whole genome sequencing are more likely to be informative.

Activation of RAS/MAPK pathway confers MCL-1 mediated acquired resistance to BCL-2 inhibitor venetoclax in acute myeloid leukemia

Despite high initial response rates, acute myeloid leukemia (AML) treated with the BCL-2-selective inhibitor venetoclax (VEN) alone or in combinations commonly acquires resistance. We performed gene/protein expression, metabolomic and methylation analyses of isogenic AML cell lines sensitive or resistant to VEN, and identified the activation of RAS/MAPK pathway, leading to increased stability and higher levels of MCL-1 protein, as a major acquired mechanism of VEN resistance. MCL-1 sustained survival and maintained mitochondrial respiration in VEN-RE cells, which had impaired electron transport chain (ETC) complex II activity, and MCL-1 silencing or pharmacologic inhibition restored VEN sensitivity. In support of the importance of RAS/MAPK activation, we found by single-cell DNA sequencing rapid clonal selection of RAS-mutated clones in AML patients treated with VEN-containing regimens. In summary, these findings establish RAS/MAPK/MCL-1 and mitochondrial fitness as key survival mechanisms of VEN-RE AML and provide the rationale for combinatorial strategies effectively targeting these pathways.

Prognostic impact of the adverse molecular-genetic profile on long-term outcomes following allogeneic hematopoietic stem cell transplantation in acute myeloid leukemia

The impact of adverse risk genetic profiles on outcomes in acute myeloid leukemia (AML) patients following allogeneic hematopoietic stem cell transplantation (HCT) has not been fully elucidated. Accordingly, we have profiled somatic mutations at diagnosis using next-generation sequencing (NGS) in 178 AML patients who received allogeneic HCT. NGS revealed 598 somatic mutations in 165/178 patients (92.7%). Frequently mutated genes include DNMT3A, TET2, NPM1, RUNX1, IDH2, and FLT3. Commonly detected cytogenetic profiles include normal karyotype, trisomy 8, monosomal karyotype (MK), deletion 5, complex karyotype (CK), and monosomy 7. In univariate analyses, TP53 mutation, MK, CK, and monosomy 7 were associated with decreased overall survival (OS), relapse-free survival (RFS), and a higher relapse incidence (RI). We defined adverse molecular-genetic profile as harboring at least one of the molecular/genetic abnormalities of TP53 mutation, MK, CK, monosomy 7, and deletion 5. The patients harboring adverse molecular-genetic profile (n = 30) showed a lower 2-year OS (24.9% vs. 57.9%; p = 0.003), RFS (23.7% vs. 57.9%; p = 0.002), and higher RI (47.2% and 17.2%; p = 0.001) after HCT when compared to patients without those lesions. Multivariate analysis confirmed adverse molecular-genetic profile as an independent prognostic factor, associated with decreased OS (HR 2.19), RFS (HR 2.23), and higher RI (HR 2.94).

Global Interactome Mapping of Mitochondrial Intermembrane Space Proteases Identifies a Novel Function for HTRA2

A number of unique proteases localize to specific sub-compartments of the mitochondria, but the functions of these enzymes are poorly defined. Here, in vivo proximity-dependent biotinylation (BioID) is used to map the interactomes of seven proteases localized to the mitochondrial intermembrane space (IMS). In total, 802 high confidence proximity interactions with 342 unique proteins are identified. While all seven proteases co-localized with the IMS markers OPA1 and CLPB, 230 of the interacting partners are unique to just one or two protease bait proteins, highlighting the ability of BioID to differentiate unique interactomes within the confined space of the IMS. Notably, high-temperature requirement peptidase 2 (HTRA2) interacts with eight of 13 components of the mitochondrial intermembrane space bridging (MIB) complex, a multiprotein assembly essential for the maintenance of mitochondrial cristae structure. Knockdown of HTRA2 disrupts cristae in HEK 293 and OCI-AML2 cells, and leads to increased intracellular levels of the MIB subunit IMMT. Using a cell-free assay it is demonstrated that HTRA2 can degrade recombinant IMMT but not two other core MIB complex subunits, SAMM50 and CHCHD3. The IMS protease interactome thus represents a rich dataset that can be mined to uncover novel IMS protease biology.

Connections Between Clonal Hematopoiesis, Cardiovascular Disease, and Cancer: A Review

Importance

Clonal hematopoiesis (CH) has been recently described as a novel driver for cancer and cardiovascular disease (CVD). Clonal hematopoiesis is a common, age-associated disorder marked by expansion of hematopoietic clones carrying recurrent somatic mutations. Current literature suggests that patients with CH have a higher risk of subsequent hematological malignant conditions and mortality attributable to excess CVD. This review discusses the association of cancer with CVD with CH as a potential unifying factor.

Observations

The prevalence of CH varies based on the sequencing depth, diagnostic criteria, and patient age and ranges from less than 1% in those younger than 40 years to more than 15% to 20% in those 90 years and older. Clonal hematopoiesis is associated with a 0.5% to 1.0% absolute annual risk of hematological malignant condition and a 2-fold to 4-fold higher risk of coronary artery disease, stroke, and CVD deaths, independent of traditional cardiovascular risk factors. In fact, CH appears to have a relative risk similar to that of traditional cardiovascular risk factors for CVD. Experimental studies suggest that the link between CVD and CH is causal, with inflammation as 1 potential mechanism. There may be also a link between CH and CVD in survivors of cancer; however, data to support this association are currently limited.

Conclusions and Relevance

Clonal hematopoiesis represents a premalignant state, with carriers having an increased risk of hematological malignant conditions. Although most carriers will not develop a malignant condition, CH confers an increased risk of CVD, possibly via inflammation. Clonal hematopoiesis may also contribute to CVD in survivors of cancer, although this hypothesis requires validation. Clinically, as advanced sequencing techniques become available, CH may pave the way for precision medicine in the field of cardio-oncology.

Abstract 4529: Mapping the protein interactome of mitochondrial intermembrane space proteases identifies a novel function for HTRA2

Mitochondria possess unique proteases that localize to specific sub-compartments of the organelle. However, the functions of these proteases are largely ill-defined. Here, we used proximity-dependent biotinylation (BioID) to map the interactomes of seven proteases located in the intermembrane space of the mitochondria. The mitochondrial intermembrane space proteases HTRA2, OMA1, YME1L1, LACTB, IMMP1L, IMMP2L and PARL were cloned in-frame with the abortive E. coli biotin ligase BirA*, and expressed in 293 T-REx cells. Cell culture media was spiked with biotin for 24 hrs, the cells lysed, and biotinylated proteins were isolated and identified by mass spectrometry. In total, we identified 342 different proteins as high confidence interactors of the seven mitochondrial proteases. Of these, 272 are assigned a GO mitochondrial annotation, and 230 proteins interacted with only 1 or 2 proteases in our dataset. Validation efforts were focused on high temperature requirement peptidase A 2 (HTRA2). HTRA2 is a serine protease that is released into the cytoplasm during apoptosis where it binds Inhibitor of Apoptosis Proteins (IAPs). However, little is known about the function of HTRA2 in the mitochondria. HTRA2 interacted with 60 mitochondrial, 11 nuclear and 4 cytoplasmic proteins, including its known interactor XIAP, and consistent with its known localization to these cellular compartments. HTRA2 interacted with 8 out of 13 components of the MIB complex, a multiprotein assembly that is essential for proper mitochondrial cristae formation. Knockdown of HTRA2 with shRNA in 293T-REx cells disrupted cristae formation and this phenotype was rescued by expression of an shRNA-resistant HTRA2 cDNA. Compared to normal hematopoietic cells, HTRA2 mRNA expression levels are increased in a subgroup of primary AML cells. HTRA2 knockdown in OCI-AML2 leukemia cells led to a similar disruption of mitochondrial cristae. Knockdown of HTRA2 in OCI-AML2 cells led to increased levels of the MIB subunit IMMT, but not two other MIB complex subunits, SAMM50 and CHCHD3. Finally, in cell-free assays, we demonstrate that recombinant HTRA2 can degrade recombinant IMMT, but not SAMM50 or CHCHD3.Thus, we have mapped the interactomes of the proteases of the mitochondrial intermembrane space. Through this effort, we discovered that HTRA2 regulates protein levels of the MIB complex subunit IMMT and that disruption of this process affects mitochondrial cristae formation.

Citation Format: Aaron D. Botham, Etienne Coyaud, Sanjit Nirmalanandhan, Marcela Gronda, Rose Hurren, Neil Maclean, Jonathan St. Germain, Sara Mirali, Estelle Laurent, Brian Raught, Aaron Schimmer. Mapping the protein interactome of mitochondrial intermembrane space proteases identifies a novel function for HTRA2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4529.

Alpha-synuclein suppresses mitochondrial protease ClpP to trigger mitochondrial oxidative damage and neurotoxicity

Both α-Synuclein (αSyn) accumulation and mitochondrial dysfunction have been implicated in the pathology of Parkinson's disease (PD). Although studies suggest that αSyn and its missense mutant, A53T, preferentially accumulate in the mitochondria, the mechanisms by which αSyn and mitochondrial proteins regulate each other to trigger mitochondrial and neuronal toxicity are poorly understood. ATP-dependent Clp protease (ClpP), a mitochondrial matrix protease, plays an important role in regulating mitochondrial protein turnover and bioenergetics activity. Here, we show that the protein level of ClpP is selectively decreased in αSyn-expressing cell culture and neurons derived from iPS cells of PD patient carrying αSyn A53T mutant, and in dopaminergic (DA) neurons of αSyn A53T mice and PD patient postmortem brains. Deficiency in ClpP induces an overload of mitochondrial misfolded/unfolded proteins, suppresses mitochondrial respiratory activity, increases mitochondrial oxidative damage and causes cell death. Overexpression of ClpP reduces αSyn-induced mitochondrial oxidative stress through enhancing the level of Superoxide Dismutase-2 (SOD2), and suppresses the accumulation of αSyn S129 phosphorylation and promotes neuronal morphology in neurons derived from PD patient iPS cells carrying αSyn A53T mutant. Moreover, we find that αSyn WT and A53T mutant interact with ClpP and suppress its peptidase activity. The binding of αSyn to ClpP further promotes a distribution of ClpP from soluble to insoluble cellular fraction in vitro and in vivo, leading to reduced solubility of ClpP. Compensating for the loss of ClpP in the substantia nigra of αSyn A53T mice by viral expression of ClpP suppresses mitochondrial oxidative damage, and reduces αSyn pathology and behavioral deficits of mice. Our findings provide novel insights into the mechanism underlying αSyn-induced neuronal pathology, and they suggest that ClpP might be a useful therapeutic target for PD and other synucleinopathies.

The experience of medical communication in adults with acute leukemia: Impact of age and attachment security

BACKGROUND

Health care providers' (HCPs) communication with cancer patients provides both information and support. Younger patient age and greater difficulty accepting support (attachment security) have been linked to poorer communication experiences with HCPs. The present secondary data analysis examined the impact of age group and attachment security on perceived communication problems with HCPs in adults with acute leukemia (AL).

METHODS

The sample included 95 younger (age < 40 years) and 225 older (age ≥ 40 years) patients with newly diagnosed or recently relapsed AL. We assessed avoidant and anxious attachment security (reluctance to accept support and fear of its unavailability, respectively) with the modified 16-item Experiences in Close Relationships Scale. The impact of age group and attachment security on perceived communication problems, measured with the Cancer Rehabilitation Evaluation System-Medical Interaction Subscale, was assessed based on the presence and extent of communication problems.

RESULTS

Younger patients (OR = 1.79-1.82, P = .030) and those with greater avoidant (OR = 1.44, P = .001) or anxious attachment (OR = 1.38, P = .009) were more likely to report communication problems. A similar relationship was found between age (β's = -.17-.19, P = .015-.025), avoidant (β = .29, P = .013), or anxious attachment (β = .17, P = .031), and the extent of communication problems. A significant age-group × avoidant-attachment interaction (β = -.31, P = .008) suggested that more avoidant attachment was associated with more perceived communication problems in the younger but not in the older group.

CONCLUSIONS

Younger patients with AL, especially those more reluctant to seek or accept support, perceive more communication problems with their HCPs than older patients. Greater attention by HCPs to their communication with younger patients is needed.

Octadecyloxyethyl Adefovir Exhibits Potent in vitro and in vivo Cytotoxic Activity and Has Synergistic Effects with Ara-C in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) continues to be a deadly disease, with only 50-70% of patients achieving complete remission and less than 30% of adults having sustained long-term remissions. In order to address these unmet medical needs, we carried out a high-throughput screen of an in-house library of on- and off-patent drugs with the OCI/AML-2 cell line. Through this screen, we discovered adefovir dipi-voxil (adefovir-DP) as being active against human AML. In addition to adefovir-DP, there are second-generation formulations of adefovir, including octadecyloxyethyl adefovir (ODE-adefovir) and hexadecyloxypropyl adefovir (HDP-adefovir), which were designed to overcome the pharmacokinetic problems of the parent compound adefovir. Given the known clinical benefit of nucleoside analogs for the treatment of AML, we undertook studies to evaluate the potential benefit of adefovir-based molecules. In AML cell lines and patient samples, adefovir-DP and ODE-adefovir were highly potent, whereas HDP-adefovir was significantly less active. Interestingly, ODE-adefovir was remarkably less toxic than adefovir-DP towards normal hematopoietic cells. In addition, ODE-adefovir at a dose of 15 mg/kg/day showed potent activity against human AML in a NOD/SCID mouse model, with a reduction of human leukemia in mouse bone marrow of > 40% in all mice tested within 20 days of treatment. Based on its chemical structure, we hypothesized that the cytotoxicity of ODE-adefovir toward AML was through cell cycle arrest and DNA damage. Indeed, ODE-adefovir treatment induced cell cycle arrest in the S phase and increased levels of pH2Ax, indicating the induction of DNA damage. Furthermore, there was an increase in phospho-p53, transactivation of proapoptotic genes and activation of the intrinsic apoptotic pathway. Subsequent investigation unveiled strong synergism between ODE-adefovir and ara-C, making their coadministration of potential clinical benefit. Expression of MRP4, a nucleoside transporter, appeared to influence the response of AML cells to ODE-adefovir, as its inhibition potentiated ODE-adefovir killing. Taken together, our findings indicate that clinical development of ODE-adefovir or related compounds for the treatment of AML is warranted.

Aspergillus galactomannan detection in exhaled breath condensate compared to bronchoalveolar lavage fluid for the diagnosis of invasive aspergillosis in immunocompromised patients

OBJECTIVES

Exhaled breath condensate (EBC) is a noninvasive means of sampling the airways that has shown significant promise in the diagnosis of many disorders. There have been no reports of its usefulness in the detection of galactomannan (GM), a component of the cell wall of Aspergillus. The suitability of EBC for the detection of GM for the diagnosis of invasive aspergillosis (IA) using the Platelia Aspergillus enzyme-linked immunosorbent assay was investigated.

METHODS

Prospective, cross-sectional study of lung transplant recipient and haemotologic malignancy patients at a university centre. EBC samples were compared to concomitant bronchoalveolar lavage (BAL) samples among lung transplant recipients and healthy controls. EBC was collected over 10 minutes using a refrigerated condenser according to the European Respiratory Society/American Thoracic Society recommendations, with the BAL performed immediately thereafter.

RESULTS

A total of 476 EBC specimens with 444 matched BAL specimens collected from lung transplant recipients (n = 197) or haemotologic malignancy patients (n = 133) were examined. Both diluted and untreated EBC optical density (OD) values (0.0830, interquartile range (IQR) 0.0680-0.1040; and 0.1130, IQR 0.0940-0.1383), respectively, from all patients regardless of clinical syndrome were significantly higher than OD values in healthy control EBCs (0.0508, IQR 0.0597-0.0652; p < 0.0001). However, the OD index values did not correlate with the diagnosis of IA (44 samples were associated with IA). Furthermore, no significant correlation was found between EBC GM and the matched BAL specimen.

CONCLUSIONS

GM is detectable in EBC; however, no correlation between OD index values and IA was noted in lung transplant recipients.

Characterizing the mitochondrial DNA polymerase gamma interactome by BioID identifies Ruvbl2 localizes to the mitochondria

Human mitochondrial DNA (mtDNA) is replicated by the mitochondrial DNA polymerase gamma (POLG). Using proximity dependent biotin labelling (BioID), we characterized the POLG interactome and identified new interaction partners involved in mtDNA maintenance, transcription, translation and protein quality control. We also identified interaction with the nuclear AAA+ ATPase Ruvbl2, suggesting mitochondrial localization for this protein. Ruvbl2 was detected in mitochondria-enriched fractions in leukemic cells. Additionally, transgenic overexpression of Ruvbl2 from an alternative translation initiation site resulted in mitochondrial co-localization. Overall, POLG interactome mapping identifies novel proteins which support mitochondrial biogenesis and a potential novel mitochondrial isoform of Ruvbl2.

Predictive value of molecular remissions postconsolidation chemotherapy in patients with Core Binding Factor Acute Myeloid Leukemia (CBF-AML) - a single center analysis

We analyzed the outcome of 80 sequential patients with core binding factor acute myeloid leukemia and evaluated the influence of molecular monitoring by quantitative reverse transcriptase polymerase chain reaction. With a median follow-up of 5 years, the estimated 5-year relapse-free survival and overall survival were 58% and 66%, respectively. Patients who were in molecular remission at the completion of consolidation chemotherapy had a 21% risk of relapse, while the relapse risk for those in molecular remission at the end of 2 years was 5.5%. Our data indicate that postconsolidation molecular remission does not necessarily preclude disease relapse and further monitoring is required. In contrast, molecular negativity by quantitative reverse transcriptase polymerase chain reaction at the end of 2 years is associated with a low risk of relapse.

RB1 deficiency in triple-negative breast cancer induces mitochondrial protein translation

Triple-negative breast cancer (TNBC) includes basal-like and claudin-low subtypes for which no specific treatment is currently available. Although the retinoblastoma tumor-suppressor gene (RB1) is frequently lost together with TP53 in TNBC, it is not directly targetable. There is thus great interest in identifying vulnerabilities downstream of RB1 that can be therapeutically exploited. Here, we determined that combined inactivation of murine Rb and p53 in diverse mammary epithelial cells induced claudin-low-like TNBC with Met, Birc2/3-Mmp13-Yap1, and Pvt1-Myc amplifications. Gene set enrichment analysis revealed that Rb/p53-deficient tumors showed elevated expression of the mitochondrial protein translation (MPT) gene pathway relative to tumors harboring p53 deletion alone. Accordingly, bioinformatic, functional, and biochemical analyses showed that RB1-E2F complexes bind to MPT gene promoters to regulate transcription and control MPT. Additionally, a screen of US Food and Drug Administration-approved (FDA-approved) drugs identified the MPT antagonist tigecycline (TIG) as a potent inhibitor of Rb/p53-deficient tumor cell proliferation. TIG preferentially suppressed RB1-deficient TNBC cell proliferation, targeted both the bulk and cancer stem cell fraction, and strongly attenuated xenograft growth. It also cooperated with sulfasalazine, an FDA-approved inhibitor of cystine xCT antiporter, in culture and xenograft assays. Our results suggest that RB1 deficiency promotes cancer cell proliferation in part by enhancing mitochondrial function and identify TIG as a clinically approved drug for RB1-deficient TNBC.

Abstract 210: Targeting the mitochondrial DNA polymerase gamma with 2’3’-dideoxycytidine as a novel therapeutic strategy for acute myeloid leukemia

A subset of AML cells display unique mitochondrial characteristics such as increased mitochondrial DNA (mtDNA), mt mass, and sensitivity to inhibition of mtDNA transcription and protein translation. Given these unique mitochondrial characteristics, we evaluated the effect of inhibiting mtDNA replication by targeting the mtDNA polymerase gamma (POLG). POLG is a nuclear-encoded gene that replicates and repairs mtDNA. POLG mRNA is increased in leukemia cell lines and a subset of AML patients.

We evaluated the preclinical efficacy of targeting POLG using the nucleoside analog 2’,3’-dideoxycytidine (ddC), an FDA-approved anti-retroviral drug that cross-reacts with POLG.

Treatment with ddC at 500nM depleted mtDNA by &gt;90%, decreased mtDNA-encoded COXI and COXII proteins and basal oxygen consumption, and induced apoptosis in AML cell lines (OCI-AML2, TEX, K562). ddC further decreased cell viability in a subset of primary AML cells, while normal peripheral blood stem cells (PBSC’s) were resistant to ddC in vitro.

Next, we assessed the preclinical efficacy and toxicity of ddC in an OCI-AML2 xenograft model of human AML. Treatment with 35mg/kg of i.p. ddC induced tumor regression and decreased tumor mass by &gt;75% compared to vehicle. No toxicity was observed including changes in liver enzymes or organ histology. We also observed reductions in COXI and COXII protein in tumors but not liver excised from treated mice.

We next investigated the mechanism for preferential sensitivity to ddC in AML cells. A two-fold greater decrease in mtDNA content was observed in AML cells treated with ddC compared to PBSC’s, in part explaining the heightened sensitivity. However, the increased sensitivity to ddC in AML was not due to increased mtDNA turnover as mtDNA depletion after ethidium bromide treatment was comparable between AML and PBSC’s.

Therefore, we investigated the role of ddC uptake and metabolism. ddC is transported by nucleoside transporters (ENT’s, CNT’s) and activated by cytoplasmic nucleoside kinases to ddC-triphosphate (ddC-TP). Analysis of Haferlach et. al. (2010) dataset demonstrated that a subset of AML cells have higher mRNA expression of hENT2 and hCNT1, and the nucleoside diphosphate kinases NME1,2,3,5 compared to normal hematopoietic cells. Using mass spectrometry, we observed higher levels of ddC and ddCTP in sensitive AML cells compared to resistant cells. Lastly, knockdown of the deoxycytidine kinase rescued ddC cytotoxicity in TEX cells.

In summary, targeting POLG with ddC displays anti-leukemic activity in both in vitro and in vivo models of AML. The preferential toxicity of ddC is due, in part, to increased rates of uptake and activation in AML along as well as their increased sensitivity to inhibition of oxidative phosphorylation. Thus, POLG inhibitors such as ddC may have clinical utility in a subset of AML.

Citation Format: Sanduni Liyanage, Rose Hurren, Xiaoming Wang, Neil Maclean, Rebecca Laposa, Aaron Schimmer. Targeting the mitochondrial DNA polymerase gamma with 2’3’-dideoxycytidine as a novel therapeutic strategy for acute myeloid leukemia. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 210.

Blastic plasmacytoid dendritic cell neoplasm with leukemic presentation: 10-Color flow cytometry diagnosis and HyperCVAD therapy

Few studies describe the comprehensive immunophenotypic pattern of blastic plasmacytoid dendritic cell neoplasm (BPDCN) in the bone marrow and its treatment. This retrospective analysis evaluates the diagnostic flow cytometry (FCM) pattern and outcome of nine patients diagnosed with BPDCN. A four-tube 10-color FCM panel used for diagnosis of acute leukemia (AL), showed cells in the blast gate (CD45dim/low SSC) and were positive for CD4(bright), CD33(dim), CD56(heterogenous), CD123(bright), CD36, CD38, HLA-DR, CD71. Seven patients received front-line induction therapy with HyperCVAD with an overall response rate of 86%. Five of six responders underwent planned allogeneic hematopoietic cell transplantation (allo-HCT). For a median follow up of 13.3 months, the 1-year disease free survival and overall survival were 56 and 67%, respectively. An accurate diagnosis of BPDCN can be made by 10-color FCM using a four-tube AL panel demonstrating a characteristic pattern of antigen expression. Front-line induction chemotherapy with HyperCVAD can yield high remission rates, but allo-HCT is required for long-term durable remissions.

Effect of Red Blood Cell Transfusion Dependence on the Natural History of Myeloproliferative Neoplasm-Associated Myelofibrosis

BACKGROUND

There are 2 widely used criteria for red blood cell (RBC) transfusion dependence in persons with myeloproliferative neoplasm (MPN)-associated myelofibrosis: (1) the International Working Group-Myelofibrosis Research and Therapy (IWG-MRT) criteria (receipt of 2 U RBC in the preceding month); and (2) the Rand-Delphi definition (2 U RBC per month averaged over 3 months). We studied effect of these criteria on survival and risk of leukemic transformation in 259 subjects with MPN-associated myelofibrosis.

PATIENTS AND METHODS

On the basis of hemoglobin (Hb) and transfusion history, subjects were assigned to 1 of the 4 cohorts: (1) Hb ≥ 100 g/L (n = 136; 52%) and no RBC transfusions in the preceding 4 months; (2) Hb < 100 g/L, and no RBC transfusions in the preceding 4 months (n = 56; 22%); (3) subjects who met IWG-MRT criteria, but not the Rand-Delphi criteria for RBC transfusion dependence (n = 34; 13%); and (4) subjects who met the Rand-Delphi criteria for RBC transfusion dependence (n = 33; 13%).

RESULTS

Three-year probability of survival among the 4 cohorts was 81% (95% confidence interval [CI], 71-87), 55% (95% CI, 36-71), 52% (95% CI, 31-69), and 47% (95% CI, 24-67), respectively (P = .0005). There was no significant difference in baseline characteristics or survival between cohorts 3 and 4 and they were combined for subsequent analyses. In multivariate analyses, subjects who met either definition of RBC transfusion dependence had significantly worse survival (hazard ratio, 2.61; 95% CI, 1.38-4.96; P = .01).

CONCLUSION

RBC transfusion dependence is associated with worse survival irrespective of definition of transfusion dependence. No effect of anemia or RBC transfusion dependence on leukemic transformation was observed.

Depression and hopelessness in patients with acute leukemia: the psychological impact of an acute and life-threatening disorder

OBJECTIVE

Acute leukemia (AL) is a life-threatening cancer associated with substantial morbidity and mortality, particularly in older adults. Given that there has been little research on the psychological impact of such malignancies with acute onset, we assessed the prevalence and correlates of depression and hopelessness in patients with AL.

METHODS

Three hundred forty-one participants were recruited within 1 month of diagnosis or relapse and completed the Beck Depression Inventory-II (BDI-II), Beck Hopelessness Scale (BHS), Memorial Symptom Assessment Scale, and other psychosocial measures. Multivariate regression analyses identified correlates of depression and hopelessness.

RESULTS

17.8% reported clinically significant depressive symptoms (BDI-II ≥ 15), 40.4% of which were in the moderate-severe range (BDI-II ≥ 20). 8.5% reported significant symptoms of hopelessness (BHS ≥ 8). Depression was associated with greater physical symptom burden (adjusted R(2)  = 48.4%), while hopelessness was associated with older age and lower self-esteem (adjusted R(2)  = 45.4%). Both were associated with poorer spiritual well-being.

CONCLUSIONS

Clinically significant depressive symptoms were common early in the course of AL and related to physical symptom burden. Hopelessness was less common and associated with older age and lower self-esteem. The results suggest that whereas depression in AL may be related to disease burden, the preservation of hope may be linked to individual resilience, life stage, and realistic prognosis.Copyright © 2015 John Wiley & Sons, Ltd.

Abstract 3039: Targeting mitochondrial DNA polymerase gamma (POLG) as a novel therapeutic strategy for acute myeloid leukemia (AML)

Mitochondria contain their own 16.6kb genome (mtDNA) which encodes 13 protein-coding genes essential for electron transport chain activity. In mammalian cells, it is replicated solely by the nuclear-encoded mitochondrial DNA polymerase gamma (POLG), which exists as a heterotrimer with POLG2 to perform replication and repair of mtDNA. Through bioinformatic analyses, we observed increased POLG expression in a subset of AML cell lines compared to other cancer cell lines. As a subset of AML patients also have unique mitochondrial characteristics, including increased mitochondrial mass and mtDNA content compared to normal hematopoietic stem cells (Skrtic et. al., Cancer Cell, 20:674, 2011), we addressed the effects of targeting POLG as a novel therapeutic strategy for AML.

OCI-AML2 and TEX leukemia cells were treated with the anti-retroviral drug 2′,3′-dideoxycytidine(ddC) that exhibits off-target inhibition of POLG catalytic activity. At concentrations as low as 200nM, ddC depleted mtDNA, decreased mRNA expression of mtDNA transcripts, reduced the expression of mitochondrial encoded proteins COX 1 and 2 subunits that form the catalytic core of respiratory chain complex IV, decreased basal oxygen consumption rate (OCR), and reduced the proliferation and viability of AML cells. However, AML cells had large reserves in their mtDNA; as significant changes in mitochondrial proteins, metabolism, proliferation and viability were only observed with a threshold of &gt;95% depletion of mtDNA. In contrast, lesser reductions in mtDNA content with ddC did not significantly affect levels of mitochondrial transcripts, metabolism, or cell viability.

Next, we used a genetic approach and explored the impact of knocking down POLG with multiple independent shRNA in AML cells. POLG knockdown in OCI-AML2 cells depleted mtDNA content by 60% compared to controls. Consistent with the findings with ddC, mtDNA depletion to this extent produced only quantitatively minor changes in the protein expression of the mtDNA-encoded COX 1 and 2 and basal OCR. Despite the minimal effect on mitochondrial metabolism, POLG knockdown decreased the growth and viability of OCI-AML2 cells, and increased apoptosis, as measured by Annexin V staining. Results of electron microscopy analyses indicate that POLG knockdown disrupted mitochondrial cristae structure compared to controls.

In summary, these results indicate that POLG plays a role in maintaining AML cell viability and mitochondrial structure and this function is independent of mtDNA replication and oxidative metabolism.

Citation Format: Sanduni Liyanage, Rose Hurren, Rebecca Laposa, Aaron Schimmer. Targeting mitochondrial DNA polymerase gamma (POLG) as a novel therapeutic strategy for acute myeloid leukemia (AML). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3039. doi:10.1158/1538-7445.AM2015-3039

Identification of 53 compounds that block Ebola virus-like particle entry via a repurposing screen of approved drugs

In light of the current outbreak of Ebola virus disease, there is an urgent need to develop effective therapeutics to treat Ebola infection, and drug repurposing screening is a potentially rapid approach for identifying such therapeutics. We developed a biosafety level 2 (BSL-2) 1536-well plate assay to screen for entry inhibitors of Ebola virus-like particles (VLPs) containing the glycoprotein (GP) and the matrix VP40 protein fused to a beta-lactamase reporter protein and applied this assay for a rapid drug repurposing screen of Food and Drug Administration (FDA)-approved drugs. We report here the identification of 53 drugs with activity of blocking Ebola VLP entry into cells. These 53 active compounds can be divided into categories including microtubule inhibitors, estrogen receptor modulators, antihistamines, antipsychotics, pump/channel antagonists, and anticancer/antibiotics. Several of these compounds, including microtubule inhibitors and estrogen receptor modulators, had previously been reported to be active in BSL-4 infectious Ebola virus replication assays and in animal model studies. Our assay represents a robust, effective and rapid high-throughput screen for the identification of lead compounds in drug development for the treatment of Ebola virus infection.

Abstract 2510: A porphodimethene chemical inhibitor of uroporphyrinogen decarboxylase

Uroporphyrinogen decarboxylase (UROD), a heme biosynthetic pathway enzyme that converts uroporphyrinogen to coproporphyrinogen, was recently identified as a potential anticancer target. UROD inhibition leads to an increase in reactive oxygen species (ROS), likely mediated by the Fenton reaction, which decreases cancer cell viability and sensitizes cells to cisplatin and radiation. Because there is no known chemical UROD inhibitor suitable for translational research, we aimed to design, synthesize, and characterize such a compound. In silico design and docking was used to identify a potential porphyrin analogue. Subsequent synthesis produced a porphodimethene (named PI-16) that inhibited UROD in an enzymatic assay (IC50 = 9.9 µM). PI-16 did not affect porphobilinogen deaminase (at 62.5 µM), thereby exhibiting some specificity. In cellular assays, PI-16 reduced FaDu and ME-180 cancer cell viability with half maximal effective concentrations of 22.7 µM and 26.9 µM, respectively, whereas normal oral epithelial (NOE) cells were only minimally affected. PI-16 combined effectively with cisplatin and radiation, with potent synergy being observed with cisplatin (Chou-Talalay combination index &lt; 1). This work presents the first known synthetic UROD inhibitor, and sets the foundation for the design, synthesis, and characterization of higher affinity and more effective compounds.

Citation Format: Kenneth W. Yip, Zhan Zhang, Noriko Sakemura-Nakatsugawa, Jui-Wen Huang, Shijun Yue, Yulia Jitkova, Terence To, Emil Pai, Aaron Schimmer, Jonathan Lovell, Jonathan Sessler, Fei-Fei Liu. A porphodimethene chemical inhibitor of uroporphyrinogen decarboxylase. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2510. doi:10.1158/1538-7445.AM2014-2510

Abstract 4317: Inhibiting the mitochondrial DNA polymerase gamma (POLG) with 2′,3′-dideoxycytidine reduces oxidative phosphorylation and increases apoptosis in acute myeloid leukemia (AML) cells

Mitochondria contain their own genome and translation machinery, which are required for aerobic energy production through oxidative phosphorylation. A subset of AML patients are sensitive to inhibitors of mitochondrial translation, likely due to increased mitochondrial mass, increased mitochondrial DNA (mtDNA) and reliance on oxidative phosphorylation (Skrtic et. al., Cancer Cell, 20:674, 2011). In the current study we addressed a complementary approach of inhibiting mtDNA replication by targeting the mitochondrial DNA polymerase gamma (POLG). POLG is encoded by the nuclear genome and is the only known DNA polymerase in mammalian mitochondria. POLG indirectly controls electron transport chain (ETC) function since it replicates the mitochondrial genome that encodes 13 proteins essential for ETC activity.

We explored the impact of inhibiting POLG in AML cells with the nucleoside analogue reverse transcriptase inhibitor 2′,3′-dideoxycytidine (ddC), an FDA-approved antiviral drug that demonstrates off-target inhibition of POLG. In OCI-AML2 and TEX leukemia cells, treatment with 0.2-2µM ddC reduced levels of mtDNA in a dose- and time-dependent manner, with &gt;90% depletion of mtDNA after 6 days of treatment with 0.2µM ddC (p &lt;0.01). mtDNA depletion resulted in decreased protein expression of the mtDNA-encoded cytochrome c oxidases (COX) 1 and 2, that form the catalytic core of ETC complex IV. In contrast, levels of COX4, a nuclear-encoded subunit of the same respiratory complex were unaltered by ddC. Likewise, 0.2 and 2µM ddC reduced mRNA transcript levels of all mtDNA-encoded proteins. ddC (2 µM, 3 days) also decreased the activity of respiratory chain complex IV by greater than 50%.

Importantly, AML cells appear to have a large reserve in their mtDNA content; in both TEX and OCI-AML2 cells, mtDNA depletion down to 5% of control was required for levels of mtDNA-encoded transcripts or proteins to be significantly reduced. ddC treatments (2µM, 6-10 days) that depleted mtDNA beyond the above threshold reduced the proliferation (p&lt;0.05) and increased apoptosis (p&lt;0.01) of OCI-AML2 and TEX cells. In addition, 2µM ddC diminished the basal oxygen consumption rate (p&lt;0.05), a measure of oxidative phosphorylation in OCI-AML2 cells and TEX cells without altering mitochondrial mass.

In summary, treatment of AML cells with ddC depletes mtDNA, decreases mitochondrial bioenergetics and causes cell kill. However, AML cells have large reserves in their mtDNA content and can withstand depletion of up to 95% of their mtDNA without loss of oxidative metabolism.

Citation Format: Sanduni Liyanage, Rose Hurren, Rebecca Laposa, Aaron Schimmer. Inhibiting the mitochondrial DNA polymerase gamma (POLG) with 2′,3′-dideoxycytidine reduces oxidative phosphorylation and increases apoptosis in acute myeloid leukemia (AML) cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4317. doi:10.1158/1538-7445.AM2014-4317

Finding new bearings: a qualitative study on the transition from inpatient to ambulatory care of patients with acute myeloid leukemia

PURPOSE

Treatment of adult acute myeloid leukemia (AML) is intensive, with induction treatment initiated in an inpatient setting and subsequent consolidation therapy often conducted in an outpatient setting. The purpose of the present qualitative paper is to provide insight into the experience of patients in the transition from inpatient to ambulatory care.

METHODS

Participants were 35 AML patients who were interviewed about their experience of the illness and treatment. Utilizing the grounded theory method, we describe the adjustment of participants to the transition to ambulatory care.

RESULTS

As outpatients, participants described adjusting to the intensity of ambulatory treatment and to the need to assume greater responsibility for their care. They also expressed a growing desire to understand their long-term care plan, compared to their preference to focus on the present prior to discharge, and they were struggling to construct a new sense of identity.

CONCLUSIONS

AML patients are now leaving acute care settings sicker and earlier. Considering their perceptions can inform interventions to facilitate adjustment during the transition to outpatient care.

Hemochromatosis enhances tumor progression via upregulation of intracellular iron in head and neck cancer

Introduction

Despite improvements in treatment strategies for head and neck squamous cell carcinoma (HNSCC), outcomes have not significantly improved; highlighting the importance of identifying novel therapeutic approaches to target this disease. To address this challenge, we proceeded to evaluate the role of iron in HNSCC.

Experimental Design

Expression levels of iron-related genes were evaluated in HNSCC cell lines using quantitative RT-PCR. Cellular phenotypic effects were assessed using viability (MTS), clonogenic survival, BrdU, and tumor formation assays. The prognostic significance of iron-related proteins was determined using immunohistochemistry.

Results

In a panel of HNSCC cell lines, hemochromatosis (HFE) was one of the most overexpressed genes involved in iron regulation. In vitro knockdown of HFE in HNSCC cell lines significantly decreased hepcidin (HAMP) expression and intracellular iron level. This in turn, resulted in a significant decrease in HNSCC cell viability, clonogenicity, DNA synthesis, and Wnt signalling. These cellular changes were reversed by re-introducing iron back into HNSCC cells after HFE knockdown, indicating that iron was mediating this phenotype. Concordantly, treating HNSCC cells with an iron chelator, ciclopirox olamine (CPX), significantly reduced viability and clonogenic survival. Finally, patients with high HFE expression experienced a reduced survival compared to patients with low HFE expression.

Conclusions

Our data identify HFE as potentially novel prognostic marker in HNSCC that promotes tumour progression via HAMP and elevated intracellular iron levels, leading to increased cellular proliferation and tumour formation. Hence, these findings suggest that iron chelators might have a therapeutic role in HNSCC management.

Abducted by the illness: a qualitative study of traumatic stress in individuals with acute leukemia

Symptoms of traumatic stress are common in acute leukemia. The goal of the present qualitative study was to understand this traumatic stress, as perceived by patients. Participants were 43 patients with acute leukemia in Toronto, Canada. Participants were asked in serial interviews about their experience of diagnosis and treatment. A total of 65 interviews were analyzed utilizing the grounded theory method. Our findings provide insight into the traumatic experience of the diagnosis and treatment, as well as the initial psychological response to this trauma. Patients coped by surrendering control to the medical team, in whom they felt great trust. Patients also expressed a strong preference for limited information, with a preference to avoid discussions about overall prognosis. These results may inform interventions to relieve traumatic stress in this high risk population.

Abstract 4123: Investigation of growth factor signaling through macrophage colony stimulating factor (CSF-1) and its receptor (FMS) in the bone marrow stromal microenvironment in acute myeloid leukemia (AML)

Acute myeloid leukemia (AML) is a highly heterogeneous and growth factor-dependent disease of the bone marrow. The bone marrow stromal microenvironment plays a critical role in providing growth and survival signals. hFMS, the human homologue of the Feline (McDonough strain) Sarcoma virus oncogene, also known as macrophage colony stimulating factor 1 receptor (CSF1R, FMS, CD115) is a tyrosine kinase receptor found on mononuclear phagocytes that promotes their growth and differentiation. The human macrophage CSF-1 ligand (MCSF-1, CSF-1) produced by supporting cells in the bone marrow acts on FMS. CSF-1 has a full length secreted isoform v1 and a membrane-bound isoform v3. Upon activation, FMS modulates the activity of important effectors of growth and survival pathways such as the mitogen-activated protein kinase (MAPK)/ERK and phosphoinositol-3 kinase (PI3K)/Akt pathways, respectively. There is a variable association of Fms with the stem cell marker CD34 on AML cells and this suggests different structures within an AML hierarchy. To better understand stromal cell interactions mediated by the CSF-1/FMS axis and examine the high engraftment failures of AML human samples in mice, AML cells were grown on murine stromal cells that were ‘humanized’ through lentiviral-mediated introduction of human CSF-1. The soluble v1 and membrane-bound v3 isoforms of CSF-1 were investigated. We found that stroma-presented CSF-1 effectively supports the growth of leukemic cells in short and long-term growth cultures, with the v3 CSF-1 variant sustaining better growth than v1. Interestingly the FMS-(low)/CD34+ subpopulation displayed significantly better growth on stroma compared to the FMS+ populations. Eventually this subpopulation gave rise to FMS+ cells, suggesting that it may harbor stem or initiating properties. In interrogating molecular signaling events induced by the CSF-1/FMS interaction, we found that the membrane-bound v3 isoform leads to increases in phosphorylation of effectors of the MAPK and PI3k/Akt pathways, namely Akt, p70S6K and 4E-BP1, whereas the v1 variant does not elicit such signals as robustly in leukemic cells grown on stroma. Taken together, this indicates that the manner in which the ligand is presented (soluble vs. membrane-bound) impacts the growth, survival and molecular signaling arising from the leukemic-stromal cell interaction. Future work will involve generation of gene and protein expression profiles of leukemic and stromal cells after grown in co-culture in aims of identifying targets induced by the soluble vs. membrane-bound forms of CSF-1. Particular identification of druggable targets in both leukemic and stromal cell compartments will allow for the design of therapeutic strategies to interfere with leukemic-stromal cell interactions driven by the CSF-1/FMS axis.

Citation Format: Ayesha Rashid, Mohamed Fateen, Aaron Schimmer, Mark Minden. Investigation of growth factor signaling through macrophage colony stimulating factor (CSF-1) and its receptor (FMS) in the bone marrow stromal microenvironment in acute myeloid leukemia (AML). [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4123. doi:10.1158/1538-7445.AM2013-4123

Symptom burden and supportive care in patients with acute leukemia

We examined the symptoms and referral rates to specialized palliative care and psychosocial oncology services of patients with acute leukemia. The Memorial Symptom Assessment Scale (MSAS) was completed by 249 adult patients with acute leukemia. Patients reported a median of 9 physical and 2 psychological symptoms, and those with intense lack of energy, difficulty sleeping and pain were more likely to report intense worrying/sadness (P<0.001). No patients with moderate-severe pain were referred for specialized symptom control and only 13% of those with severe worrying/sadness were referred to psychiatry/psychology within one month of the assessment. Patients in this population have a substantial symptom burden; further research is needed to determine the benefit of early referral to specialized supportive care services.

Abstract 1123: AML cells have low reserve capacity in their respiratory chain complexes leading to increased sensitivity to palmitate-induced cell death

Mitochondria contain their own DNA that encodes 13 proteins that comprise the respiratory chain. Recently we demonstrated that inhibiting mitochondrial protein synthesis is preferentially cytotoxic to AML cells and stem cells over normal hematopoietic stem cells due to dysregulated mitochondrial biogenesis in AML. Given the dysregulated mitochondrial biogenesis in primary AML cells, we examined the activity of the respiratory chain complexes in primary AML and normal PBSCs. The enzymatic activity of the respiratory chain complexes were equivalent between primary AML cell and normal hematopoietic cells. We then evaluated the reserve capacity of the respiratory chain complexes. Primary AML cells (n=11) and PBSCs (n =5) were treated with increasing concentrations of chemical respiratory complex inhibitors and the effects on oxygen consumption were measured using the 96-well Seahorse XF Extracellular Flux (XF) Analyzer. AML cells with increased mitochondrial mass displayed heightened sensitivity to the complex inhibitors and less reserve capacity in the respiratory complex compared to normal hematopoietic cells. For example, the mean concentration of the complex III inhibitor antimycin required to reduce oxygen consumption by 50% in primary AML cells was 13.7 ± 1.6 nM vs 29.0 ± 2.4 nM (p=0.0007) for normal hematopoietic cells. Thus, small reductions in the enzyme activity of the respiratory complexes produced greater reductions in oxygen consumption in AML cells compared to normal hematopoietic cells. The reduced capacity of the respiratory chain in primary AML cells highlighted a potential therapeutic approach. We speculated that increasing electron flux through the respiratory chain would preferentially overwhelm the capacity of the complexes in AML cells. To test this strategy, AML cell lines and primary AML samples were treated with increasing concentrations of the fatty acid substrate palmitate to increase the production of Acetyl-CoA and increase flux of electrons through the respiratory chain. Treatment of AML cells with palmitate transiently increased oxygen consumption. However, by 4 hours after treatment, reactive oxygen species increased, oxygen consumption decreased and cell death ensued. In contrast, cell lines with greater reserve capacity including normal hematopoietic cells displayed no change in oxygen consumption, reactive oxygen species or cell viability after palmitate treatment. Thus, we have demonstrated that AML cells have reduced reserve capacity in their respiratory chain leading to heightened sensitivity to reductions in respiratory complexes by inhibiting mitochondrial protein synthesis. The reduced reserve capacity also heightens their sensitivity to increased electron flux through the respiratory chain. As such, targeting the aberrant metabolism of AML may be a novel therapeutic strategy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1123. doi:1538-7445.AM2012-1123

Traumatic stress in acute leukemia

OBJECTIVE

Acute leukemia is a condition with an acute onset that is associated with considerable morbidity and mortality. However, the psychological impact of this life-threatening condition and its intensive treatment has not been systematically examined. In the present study, we investigate the prevalence and correlates of post-traumatic stress symptoms in this population.

METHODS

Patients with acute myeloid, lymphocytic, and promyelocytic leukemia who were newly diagnosed, recently relapsed, or treatment failures were recruited at a comprehensive cancer center in Toronto, Canada. Participants completed the Stanford Acute Stress Reaction Questionnaire, Memorial Symptom Assessment Scale, CARES Medical Interaction Subscale, and other psychosocial measures. A multivariate regression analysis was used to assess independent predictors of post-traumatic stress symptoms.

RESULTS

Of the 205 participants, 58% were male, mean age was 50.1 ± 15.4 years, 86% were recently diagnosed, and 94% were receiving active treatment. The mean Stanford Acute Stress Reaction Questionnaire score was 30.2 ± 22.5, with 27 of 200 (14%) patients meeting criteria for acute stress disorder and 36 (18%) for subsyndromal acute stress disorder. Post-traumatic stress symptoms were associated with more physical symptoms, physical symptom distress, attachment anxiety, and perceived difficulty communicating with health-care providers, and poorer spiritual well-being (all p < 0.05).

CONCLUSIONS

The present study demonstrates that clinically significant symptoms of traumatic stress are common in acute leukemia and are linked to the degree of physical suffering, to satisfaction with relationships with health-care providers, and with individual psychological characteristics. Longitudinal study is needed to determine the natural history, but these findings suggest that intervention may be indicated to alleviate or prevent traumatic stress in this population.

Abstract C170: The combination of statins and dipyridamole is effective preclinically in AML, MM, and breast cancer

Statins are drugs that have been utilized for years to treat hyperlipidemia through inhibition of the rate-limiting enzyme of the mevalonate (MVA) pathway, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR). Preclinical evidence has demonstrated statins to possess anti-cancer properties against a wide range of tumors but not normal cells. Through the use of a chemical library screen, we hypothesize that the identification of compounds which potentiate the anti-cancer effects of statins will uncover novel molecular pathways and/or targets that can be exploited in combination with the MVA pathway to maximize tumor cell death.

A pilot 100-compound library, composed of off-patent pharmacologically active drugs clinically used for a wide spectrum of diseases was screened in the multiple myeloma (MM) KMS11 cell line. Dipyridamole (DP), a commonly prescribed anti-platelet agent potentiated the anti-cancer effects of atorvastatin. The DP-statin combination was synergistic and capable of inducing apoptosis in a variety of acute myelogenous leukemia (AML), MM and breast cancer cell lines. The DP-statin combination also induced apoptosis in primary AML patient samples, but was not toxic to normal PBSCs. In an in vivo AML tumor model, the DP-statin combination was found to be effective at inhibiting tumor growth.

DP is known to elicit numerous effects, amongst them, phosphodiesterase (PDE) inhibition. In AML cell lines, activators of the PKA pathway including other PDE inhibitors, also induced apoptosis in combination with statins similar to DP. Interestingly, the DP-statin combination prevented the increase of HMGCR, which occurs following statin treatment as part of a classic feedback response. Further mechanistic investigations to determine how DP potentiates statin-induced apoptosis are underway. As both statins and DP are pre-approved for use in humans, off-patent, and readily available, they have the potential to directly impact patient care.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C170.

Phase II study of obatoclax mesylate (GX15-070), a small-molecule BCL-2 family antagonist, for patients with myelofibrosis

BACKGROUND

Myelofibrosis (MF) is a disease characterized by the overexpression of the antiapoptotic BCL-2 family of proteins (eg, BCL-XL and MCL-1).

PATIENTS AND METHODS

We conducted a multicenter, open-label, noncomparative phase II study of obatoclax mesylate, a small-molecule pan-BCL-2 antagonist, in patients with MF. Obatoclax was administered as a 24-hour infusion (on an outpatient basis) every 2 weeks at a fixed dose of 60 mg.

RESULTS

A total of 22 patients were enrolled, with a median age of 63 years (range, 43-89 years). Twelve were men, and all 22 patients were previously treated (median of 2 previous therapies). Ten patients (45%) had a Lille score of 1, and 9 patients (41%) had a Lille score of 2. Thirteen (59%) were red blood cell transfusion dependent. A median of 7 cycles of obatoclax were administered. No patient achieved complete or partial response according to International Working Group criteria. One patient (4%) demonstrated a clinical improvement (in terms of hemoglobin and platelet count) after 7 cycles of therapy. The improvement was sustained for 4 cycles of therapy, after which he underwent allogeneic stem cell transplantation. The most common adverse events included low-grade ataxia and fatigue in 50% of the patients. Dose reduction because of toxicity was required in 1 patient, whereas 2 patients were taken off the study because of grade 3 ataxia and grade 3 heart failure. Grade 3/4 anemia and thrombocytopenia were evident in 6 (27%) and 4 (18%) patients, respectively.

CONCLUSION

Obatoclax exhibits no significant clinical activity in patients with MF at the dose and schedule evaluated.

Role of peroxisome proliferator-activated receptor-gamma and its coactivator DRIP205 in cellular responses to CDDO (RTA-401) in acute myelogenous leukemia

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a member of the nuclear receptor (NR) family of transcription factors with important regulatory roles in cellular growth, differentiation, and apoptosis. Using proteomic analysis, we showed expression of PPARgamma protein in a series of 260 newly diagnosed primary acute myelogenous leukemia (AML) samples. Forced expression of PPARgamma enhanced the sensitivity of myeloid leukemic cells to apoptosis induced by PPARgamma agonists 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO) and 15-deoxy-(12,14)-15DPGJ(2), through preferential cleavage of caspase-8. No effects on cell cycle distribution or differentiation were noted, despite prominent induction of p21 in PPARgamma-transfected cells. In turn, antagonizing PPARgamma function by small interfering RNA or pharmacologic PPARgamma inhibitor significantly diminished apoptosis induction by CDDO. Overexpression of coactivator protein DRIP205 resulted in enhanced differentiation induction by CDDO in AML cells through PPARgamma activation. Studies with DRIP205 deletion constructs showed that the NR boxes of DRIP205 are not required for this coactivation. In a phase I clinical trial of CDDO (RTA-401) in leukemia, CDDO induced an increase in PPARgamma mRNA expression in six of nine patient samples; of those, induction of differentiation was documented in four patients and that of p21 in three patients, all expressing DRIP205 protein. In summary, these findings suggest that cellular levels of PPARgamma regulate induction of apoptosis via caspase-8 activation, whereas the coactivator DRIP205 is a determinant of induction of differentiation, in response to PPARgamma agonists in leukemic cells.

Abstract A27: Chronic exposure of malignant hematological cell lines to bortezomib induces de novo hot spot mutations in the PSMB5 gene

The proteasome inhibitor Bortezomib (BTZ, Velcade®) specifically inhibits the catalytic beta 5 subunit of the proteasome. The introduction of BTZ has shown promising results in the treatment of Multiple Myeloma (MM), Non-Hodgkin lymphoma and leukemia. Despite these encouraging results, clinical trials in MM also revealed that a significant proportion of patients acquired resistance to BTZ mono-therapy. We have developed a BTZ-resistant cell line model by chronic exposure to stepwise increasing concentrations of BTZ, including the AML THP-1 cell-line (Oerlemans & Franke et al, Blood 2008), the T-ALL CCRF-CEM-C7 cell-line and the MM RPMI-8226 cell line (Franke et al, Blood 2009 vol 114(22), abstr 940). Cells were initially selected for growth at 7 nM BTZ to acquire low levels of BTZ resistance (2–3 fold higher IC50 concentrations) and subsequently challenged to concentrations of BTZ up to 500 nM to provoke higher resistance levels. Abilities to resist a BTZ concentration of 100 nM could be achieved relatively fast in the CEM cell line (within 16 weeks), intermediate in the THP-1 cell line (within 22 weeks) and relatively slowly in the 8226 cell line (within 60 weeks). Subsequent sequencing of the PSMB5 gene, encoding the beta 5 proteasome subunit, revealed a series of mutations in individual BTZ-resistant subclones, all resulting in amino-acid changes residing within the highly conserved BTZ binding pocket.

The relatively fast induction of mutations provoked the question whether there might already exist a subclone within the cell line that harbours the mutation. To distinguish between the outgrowth of a pre-existing resistant subclone and the occurrence of de novo mutations, we generated new BTZ resistant CEM and THP-1 cells (CEM-BR2 and THP-1-BR2). Interestingly, the new CEM-BR2 cells had a different nucleotide change (G322A resulting in a Ala49Thr substitution) from the original BTZ resistant CEM-BR1 (C323T and G332T resulting in Ala49Val and Cys52Phe amino acid substitutions, respectively). Of note, this new CEM-BR2 mutation represented the same mutation as seen in the original BTZ resistant THP-1-BR1. In addition, the new THP-1-BR2 cells also showed a different mutation (A309G) in the PSMB5 gene, introducing a Met45Val amino-acid substitution) compared to the original BTZ resistant THP-1 cells that showed a Met45Iso substitution. These results indicate that the mutations are acquired during BTZ exposure and are mainly induced in specific hot-spots (dominantly Ala49) within the PSMB5 gene. To explore whether mutation-induced resistance could be bypassed, a new proteasome inhibitor, 5-amino-8-hydroxyquinole (5AHQ), acting as a non-competitive inhibitor of the non-catalytic alpha-7 subunit of the proteasome (Li et al. ASH 2008) was studied in our model system. Strikingly, all BTZ-resistant selectants retained full sensitivity towards 5AHQ (IC50: 4–7 μM, measured in a 4-day MTT cytotoxicity assay) as compared to parental cells.

To determine whether mutation induction also occurs in patients treated with BTZ, screening for their presence in clinical samples of BTZ refractory patients is warranted. The notion that 5AHQ can overcome BTZ resistance related to single and multiple mutations in the PSMB5 gene, supports further research in this drug and its analogues. This study is supported by VUmc - Stichting Translational Research (STR) and The Netherlands Organization for Health Research and Development (ZonMw).

Citation Information: Clin Cancer Res 2010;16(7 Suppl):A27

A safety and schedule seeking trial of Bcl-2 inhibitor obatoclax in previously untreated older patients with acute myeloid leukemia (AML)

3579

Background: Obatoclax (Ob) is a small-molecule inhibitor of all Bcl-2 prosurvival proteins. In a previous study a 70 year old patient with untreated AML had a cytogenetic CR 8 days after receiving 20 mg/m2 of Ob over 24 hrs. This study evaluated the single-agent response rate in older patients with previously untreated AML. Methods: A Safety phase to evaluate escalating doses of Ob given by 3-hr infusion was performed. Based on previous results, the dose of 60 mg over 24 hrs was used for the 24-hr infusion arm of the Schedule Seeking phase, in which Ob was administered as either a 3-hr or 24-hr infusion for 3 consecutive days every 2 wks. The endpoint of the Schedule Seeking phase was CR after C2 in 16 randomized patients. Eligibility criteria included age ≥ 70, untreated AML (1 prior Rx allowed in Safety phase), ECOG PS ≤2, adequate renal and hepatic function. PK samples were collected during C1. Results: 18 patients (8 male; median age 82) were enrolled. 2/3 patients enrolled into the 1st cohort (30 mg x 3 days) of the Safety phase had DLT events (ataxia and somnolence). 3 patients enrolled into a 20 mg x 3 days cohort had no DLTs; this dose was used for Schedule Seeking patients receiving 3-hr infusions. In the Schedule Seeking phase, 7 patients were randomized to receive 20 mg by 3-hr infusion and 5 were randomized to receive 60 mg by 24-hr infusion. The most common (>25%) AEs were euphoric mood (50%), ataxia (38%), & somnolence (38%). Efficacy data after C2 show that 3 patients in the 20 mg 3-hr infusion cohort in the Safety phase and 1 at the same dose & schedule in the Schedule Seeking phase had ≥50% decrease in BM blasts after C2, which was not seen in the 60 mg 24-hr infusion cohort. There were no CRs. There was a single death by D28 (24-hr infusion). There were significant differences in PK by infusion schedule. Conclusions: MTD for Ob as a 3-hr infusion administered in older patients with AML on 3 consecutive days is 20 mg/day, and both this regimen and 60 mg as a 24-hr infusion x 3 days were well tolerated. Evidence of biological activity was seen with the 3-hr infusion schedule but not with the 24-hr infusion schedule, suggesting that efficacy may be improved with the 3-hr infusion schedule and may be related to PK differences.

[Table: see text]