Accessories to the crime: functions of cells recruited to the tumor microenvironment

To meet the requirements for rapid tumor growth, a complex array of non-neoplastic cells are recruited to the tumor microenvironment. These cells facilitate tumor development by providing matrices, cytokines, growth factors, as well as vascular networks for nutrient and waste exchange, however their precise origins remain unclear. Through multicolored tissue transplant procedures; we have quantitatively determined the contribution of bone marrow-derived and adipose-derived cells to stromal populations within syngeneic ovarian and breast murine tumors. Our results indicate that subpopulations of tumor-associated fibroblasts (TAFs) are recruited from two distinct sources. The majority of fibroblast specific protein (FSP) positive and fibroblast activation protein (FAP) positive TAFs originate from mesenchymal stem/stromal cells (MSC) located in bone marrow sources, whereas most vascular and fibrovascular stroma (pericytes, α-SMA⁺ myofibroblasts, and endothelial cells) originates from neighboring adipose tissue. These results highlight the capacity for tumors to utilize multiple sources of structural cells in a systematic and discriminative manner.

Differential impact of structurally different anti-diabetic drugs on proliferation and chemosensitivity of acute lymphoblastic leukemia cells

Hyperglycemia during hyper-CVAD chemotherapy is associated with poor outcomes of acute lymphoblastic leukemia (ALL) (Cancer 2004; 100: 1179-85). The optimal clinical strategy to manage hyperglycemia during hyper-CVAD is unclear. To examine whether anti-diabetic pharmacotherapy can influence chemosensitivity of ALL cells, we examined the impacts of different anti-diabetic agents on ALL cell lines and patient samples. Pharmacologically achievable concentrations of insulin, aspart and glargine significantly increased the number of ALL cells, and aspart and glargine did so at lower concentrations than human insulin. In contrast, metformin and rosiglitazone significantly decreased the cell number. Human insulin and analogs activated AKT/mTOR signaling and stimulated ALL cell proliferation (as measured by flow cytometric methods), but metformin and rosiglitazone blocked AKT/mTOR signaling and inhibited proliferation. Metformin 500 μM and rosiglitazone 10 μM were found to sensitize Reh cells to daunorubicin, while aspart, glargine and human insulin (all at 1.25 mIU/L) enhanced chemoresistance. Metformin and rosiglitazone enhanced daunorubicin-induced apoptosis, while insulin, aspart and glargine antagonized daunorubicin-induced apoptosis. In addition, metformin increased etoposide-induced and L-asparaginase-induced apoptosis; rosiglitazone increased etoposide-induced and vincristine-induced apoptosis. In conclusion, our results suggest that use of insulins to control hyperglycemia in ALL patients may contribute to anthracycline chemoresistance, while metformin and thiazolidinediones may improve chemosensitivity to anthracycline as well as other chemotherapy drugs through their different impacts on AKT/mTOR signaling in leukemic cells. Our data suggest that the choice of anti-diabetic pharmacotherapy during chemotherapy may influence clinical outcomes in ALL.

A randomized controlled trial of an intensive insulin regimen in patients with hyperglycemic acute lymphoblastic leukemia

Hyperglycemia during hyper-CVAD (fractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone alternating with methotrexate and high-dose cytarabine, with methylprednisolone premedication) chemotherapy is associated with poor outcomes of acute lymphoblastic leukemia (ALL). To examine whether intensive insulin therapy could improve outcomes, a randomized trial was conducted that compared glargine plus aspart vs. conventional therapy. Intensive insulin did not improve ALL clinical outcomes despite improved glycemic control. Secondary analysis suggests that the choice of antidiabetic pharmacotherapy may influence ALL outcomes.

INTRODUCTION

Hyperglycemia during hyper-CVAD (fractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone alternating with methotrexate and high-dose cytarabine, with methylprednisolone premedication) chemotherapy is associated with poor outcomes of acute lymphoblastic leukemia (ALL).

PATIENTS AND METHODS

To examine whether an intensive insulin regimen could improve outcomes compared with conventional antidiabetic pharmacotherapy, a randomized trial was conducted that compared glargine plus aspart vs. conventional therapy (control). Between April 2004 and July 2008, 52 patients newly diagnosed with ALL, Burkitt lymphoma, or lymphoblastic lymphoma who were on hyper-CVAD in the inpatient setting and had a random serum glucose level >180 mg/dL on ≥2 occasions during chemotherapy were enrolled.

RESULTS

The trial was terminated early due to futility regarding ALL clinical outcomes despite improved glycemic control. Secondary analysis revealed that molar insulin-to-C-peptide ratio (I/C) > 0.175 (a surrogate measure of exogenous insulin usage) was associated with decreased overall survival, complete remission duration and progression-free survival (PFS), whereas metformin and/or thiazolidinedione usage were associated with increased PFS. In multivariate analyses, factors that significantly predicted short overall survival included age ≥ 60 years (P = .0002), I/C ≥ 0.175 (P = .0016), and average glucose level ≥ 180 mg/dL (P = .0236). Factors that significantly predicted short PFS included age ≥ 60 years (P = .0008), I/C ≥ 0.175 (P = .0002), high systemic risk (P = .0173) and average glucose level ≥ 180 mg/dL (P = .0249). I/C ≥ 0.175 was the only significant (P = .0042) factor that predicted short complete remission duration.

CONCLUSIONS

A glargine-plus-aspart intensive insulin regimen did not improve ALL outcomes in patients with hyperglycemia. Exogenous insulin may be associated with poor outcomes, whereas metformin and thiazolidinediones may be associated with improved outcomes. Analysis of these results suggests that the choice of antidiabetic pharmacotherapy may influence ALL outcomes.

A phase I first-in-human trial of bardoxolone methyl in patients with advanced solid tumors and lymphomas

PURPOSE

Bardoxolone methyl, a novel synthetic triterpenoid and antioxidant inflammation modulator, potently induces Nrf2 and inhibits NF-κB and Janus-activated kinase/STAT signaling. This first-in-human phase I clinical trial aimed to determine the dose-limiting toxicities (DLT), maximum tolerated dose (MTD), and appropriate dose for phase II studies; characterize pharmacokinetic and pharmacodynamic parameters; and assess antitumor activity.

EXPERIMENTAL DESIGN

Bardoxolone methyl was administered orally once daily for 21 days of a 28-day cycle. An accelerated titration design was employed until a grade 2-related adverse event occurred. A standard 3 + 3 dose escalation was then employed until the MTD was reached. Single dose and steady-state plasma pharmacokinetics of the drug were characterized. Assessment of Nrf2 activation was examined in peripheral blood mononuclear cells (PBMC) by measuring NAD(P)H:quinone oxidoreductase (NQO1) mRNA levels. Immunohistochemical assessment of markers of inflammation, cell cycle, and apoptosis was carried out on tumor biopsies.

RESULTS

The DLTs were grade 3 reversible liver transaminase elevations. The MTD was established as 900 mg/d. A complete tumor response occurred in a mantle cell lymphoma patient, and a partial response was observed in an anaplastic thyroid carcinoma patient. NQO1 mRNA levels increased in PBMCs, and NF-κB and cyclin D1 levels decreased in tumor biopsies. Estimated glomerular filtration rate (eGFR) was also increased.

CONCLUSIONS

Bardoxolone methyl was well tolerated with an MTD of 900 mg/d. The increase in eGFR suggests that bardoxolone methyl might be beneficial in chronic kidney disease. Objective tumor responses and pharmacodynamic effects were observed, supporting continued development of other synthetic triterpenoids in cancer.

Human extramedullary bone marrow in mice: a novel in vivo model of genetically controlled hematopoietic microenvironment

The interactions between hematopoietic cells and the bone marrow (BM) microenvironment play a critical role in normal and malignant hematopoiesis and drug resistance. These interactions within the BM niche are unique and could be important for developing new therapies. Here, we describe the development of extramedullary bone and bone marrow using human mesenchymal stromal cells and endothelial colony-forming cells implanted subcutaneously into immunodeficient mice. We demonstrate the engraftment of human normal and leukemic cells engraft into the human extramedullary bone marrow. When normal hematopoietic cells are engrafted into the model, only discrete areas of the BM are hypoxic, whereas leukemia engraftment results in widespread severe hypoxia, just as recently reported by us in human leukemias. Importantly, the hematopoietic cell engraftment could be altered by genetical manipulation of the bone marrow microenvironment: Extramedullary bone marrow in which hypoxia-inducible factor 1α was knocked down in mesenchymal stromal cells by lentiviral transfer of short hairpin RNA showed significant reduction (50% ± 6%; P = .0006) in human leukemic cell engraftment. These results highlight the potential of a novel in vivo model of human BM microenvironment that can be genetically modified. The model could be useful for the study of leukemia biology and for the development of novel therapeutic modalities aimed at modifying the hematopoietic microenvironment.

Effects of PPARγ Ligands on Leukemia

Peroxisome proliferator-activated receptors (PPARs) and retinoic acid receptors (RARs), members of the nuclear receptor superfamily, are transcription factors that regulate a variety of important cellular functions. PPARs form heterodimers retinoid X receptor (RXR), an obligate heterodimeric partner for other nuclear receptors. Several novel links between retinoid metabolism and PPAR responses have been identified, and activation of PPAR/RXR expression has been shown to increase response to retinoids. PPARγ has emerged as a key regulator of cell growth and survival, whose activity is modulated by a number of synthetic and natural ligands. While clinical trials in cancer patients with thiazolidinediones (TZD) have been disappointing, novel structurally different PPARγ ligands, including triterpenoids, have entered clinical arena as therapeutic agents for epithelial and hematopoietic malignancies. Here we shall review the antitumor advances of PPARγ, alone and in combination with RARα ligands in control of cell proliferation, differentiation, and apoptosis and their potential therapeutic applications in hematological malignancies.

Phase I study of TH-302, a hypoxia-activated cytotoxic prodrug, in subjects with advanced leukemias

6585

Background: TH-302 is a 2-nitroimidazole prodrug of the DNA alkylator, bromo-isophosphoramide mustard designed to be selectively activated in hypoxic conditions. Preclinical data in mice with ALL have demonstrated marked expansion of hypoxia in areas of marrow leukemia infiltrates (Benito et al., PlosOne, in press). TH-302 also exhibited specific hypoxia-dependent cytotoxicity when tested against primary ALL and AML samples in vitro. Based on these findings, a phase 1 study of TH-302 was designed for advanced leukemias. Methods: Eligibility: ECOG ≤ 3, relapsed/refractory leukemias for which no standard therapy options were available, and acceptable hepatorenal function. A standard 3+3 dose escalation design was used with 40% dose increments. TH-302 was administered IV over 30-60 minutes daily on Days 1-5 of a 21-day cycle. The objectives were to determine the MTD and PK profile of TH-302 with this schedule and to assess preliminary clinical activity of TH-302. Results: 34 subjects with previously treated AML (n=26), ALL (n=6) or CML in blast phase (n=1) received TH-302 at doses of 120 (n=4), 170 (n=4), 240 (n=3), 330 (n=3), 460 (n=16) or 550 (n=4) mg/m². No skin or mucosal toxicity was noted in participants treated with TH-302 doses ≤240 mg/m2. At 330 mg/m2, grade 2 dermatological toxicities included skin ulcer (n=1) and hand/foot syndrome (n=1). Grade 2 mucositis (n=3) and grade 2 skin toxicity (e.g. skin rash, skin ulcers; n=3) were reported at 460 mg/m2; none were dose-limiting. Two of 3 evaluable subjects treated at the 550 mg/m2 cohort experienced DLTs of grade 3 esophagitis. Eight subjects had stable disease or better after 1 cycle. One ALL subject (at 120 mg/m2) cleared marrow blasts with persistent neutropenia. One AML subject (at 550 mg/m2) achieved CRp after 1 cycle with resolution of leukemia cutis. Conclusions: TH-302 administered daily for 5 consecutive days every 3 weeks is well-tolerated with increased incidence of skin and mucosal toxicity at higher dose levels. Clinical activity has been noted with a few objective responses, but majority of cytoreductions in the AML subset were transient. Clinical trials combining TH-302 with various chemotherapeutics with established efficacy in AML and ALL are planned.

AML patients with IDH1 or IDH2 mutations treated with hypomethylating agents: A case series

6576

Background: Isocitrate dehydrogenase 1 (IDH1) and IDH2 mutations play a significant role in acute myeloid leukemia (AML), yet optimal treatment for AML patients with IDH mutations remains unclear. IDH mutations have been associated with a globally hypermethylated genomic state, as the result of increased levels of 2-HG, a regulator of histone methylation. We sought to retrospectively determine responses of patients with IDH-mutated AML to treatment with hypomethylating agents. Methods: We reviewed clinical data for AML patients treated at The University of Texas M. D. Anderson Cancer Center from June 2001 to December 2011 whose stored leukemia samples from bone marrow aspirateshad been tested retrospectively for IDH1 and IDH2 mutations. We searched three databases that contained records for 407 AML patients. We selected patients who had been treated with the hypomethylating agents 5-azacitidine or decitabine, alone or in conjunction with other therapeutics. We retrospectively reviewed the patients’ medical records to obtain demographic, laboratory, treatment, and clinical data. We evaluated response measured by remission status, reduction in bone marrow blasts and peripheral blood blasts, and time to relapse. Results: We identified 104 patients (25.6%) who had either an IDH1 or IDH2 mutation, and of these, 8 patients had also been treated with hypomethylating agents. A ninth AML patient, who is IDH2-mutant, is currently undergoing treatment with decitabine alone. Of these 9 patients, three had a durable complete remission without recovery of blood counts (CRp), three had a partial response (PR), with or without blood count recovery, and three had no response. All 9 patients did have an initial decrease in the percentage of bone marrow blasts, peripheral blood blasts, or both. Conclusions: This series of patients demonstrates the possibility that AML patients with IDH1 or IDH2 mutations benefit from the use of hypomethylating agents, and suggests it is worthwhile to prospectively investigate treatment of patients with IDH-mutated AML using hypomethylating agents.

Targeting microenvironment-mediated resistance in leukemias: Phase I trial of mobilization and elimination of FLT3-ITD+ acute myelogenous leukemia (AML) stem/progenitor cells by plerixafor/g-CSF/sorafenib

TPS6635

Background: FLT3-ITD AML are associated with poor prognosis. We identified Sorafenib (S) as potent inhibitor of FLT3-ITD (Zhang W, JNCI, 2008; Borthakur G., Haematologica, 2010). FLT3-ITD is associated with overexpression of chemokine receptor CXCR4 and we found increased in vivo activity of S combined with CXCR4 inhibitor Plerixafor (P) and G-CSF (G) (Zeng Z et.al. Blood 2009). Here we report first data testing this concept in patients with R/R FLT3-ITD AML. Methods: G (10 ug/kg) and P(240 ug/kg) were given s.c. QOD on days 1 – 13, S (400-600mg), S on d 1 - 28(one cycle). G/P was held when blasts > 5x104/uL. CD34, 38, 123, CXCR4 (1D9, 12G5), VLA4, CD44 and phospho-proteins were measured by flow cytometry. Results: 10 patients have been treated so far : 2 achieved CRp, 4 PR and 4 failed (NR), for an overall response rate of 6/10; 3/6 responders and 4/4 NR were previously treated with FLT3 inhibitors. 4/10 pts. developed hyperleukocytosis (and missed 1 to 5 doses of G/P), 6 skin rash and 3 hypertension. Analysis of cells mobilized in 22 cycles revealed a 29-fold increase in WBC, 41-fold in absolute blasts, 77-fold in granulocytes. Increase in circulating stem/progenitor cells was as follows: CD34+: 231-fold, CD34+/38- : 90-, CD34+/38-/123+(LSC) : 148-, CXCR4+: 139-, VLA-4+ : 68- and CD44+: 82-fold. Increase in LSC was correlated with baseline blasts and VLA4, not with CXCR4. FISH confirmed mobilization of leukemic cells. Increased levels of pERK and pAKT were observed in mobilized cells. Conclusion: The combination of G-CSF+Plerixafor appears superior in increasing circulating leukemic blasts and stem/progenitor cells in FLT3-ITD AML, as compared to Plerixafor alone in R/R AML(blast increase 2.1-fold; Uy et al. Blood, in press). Treatment resulted in 2/10 CRp and 4/10 PRs. Mobilized stem/progenitor cells displayed increased MAPK/AKT signaling and increased CXCR4 expression. This is the first clinical report of G-CSF/Plerixafor for the “mobilization” of AML cells, aimed at removing them from their protective bone marrow microenvironment. The initial results are providing proof-of–principle of this concept.

Ganglioside GD2 identifies breast cancer stem cells and promotes tumorigenesis

Cancer stem cells (CSCs) are a small subpopulation of cancer cells that have increased resistance to conventional therapies and are capable of establishing metastasis. However, only a few biomarkers of CSCs have been identified. Here, we report that ganglioside GD2 (a glycosphingolipid) identifies a small fraction of cells in human breast cancer cell lines and patient samples that are capable of forming mammospheres and initiating tumors with as few as 10 GD2+ cells. In addition, the majority of GD2+ cells are also CD44hiCD24lo, the previously established CSC-associated cell surface phenotype. Gene expression analysis revealed that GD3 synthase (GD3S) is highly expressed in GD2+ as well as in CD44hiCD24lo cells and that interference with GD3S expression, either by shRNA or using a pharmacological inhibitor, reduced the CSC population and CSC-associated properties. GD3S knockdown completely abrogated tumor formation in vivo. Also, induction of epithelial-mesenchymal transition (EMT) in transformed human mammary epithelial cells (HMLER cells) dramatically increased GD2 as well as GD3S expression in these cells, suggesting a role of EMT in the origin of GD2+ breast CSCs. In summary, we identified GD2 as a new CSC-specific cell surface marker and GD3S as a potential therapeutic target for CSCs, with the possibility of improving survival and cure rates in patients with breast cancer.

Laser nanothermolysis of human leukemia cells using functionalized plasmonic nanoparticles

In the present work, we present the use of gold nanorods as plasmonic nanoparticles for selective photothermal therapy of human acute (HL-60) and chronicle (K-562) leukemia cells using a near-infrared laser. We improved a published methodology of gold nanorods conjugation to generate high yields of narrow band gold nanorods with an optical absorption centered at 760 nm. The manufactured nanorods were pegylated and conjugated with monoclonal antibody to become non-toxic as biocompatible nanothermolysis agent. Gold nanorods are synthesized and conjugated to CD33 monoclonal antibody. After pegylation, or conjugation with CD33 antibody, gold nanorods were non-toxic to acute and chronic leukemia cells. Our modified gold nanorods CD33 conjugates shown high level of accumulation for both leukemia cell lines, and successful used for nanothermolysis of human leukemia cells in vitro. Each sample was illuminated with 1 or 3 laser shots as for low and for high laser fluence. The radiation was provided by a Quanta Systems q-switched titanium sapphire laser, and the system was designed for maximum sample coverage using non-focused illumination. HL-60 and K-562 cells were treated for 45 min with gold nanorods CD33 conjugated, or with pegylated gold nanorods. The effect of pulsed-laser nanothermolysis for acute and chronic leukemia cells were investigated with cell counting for number of living cells, percentage of cell death and functional parameters such as damage of cell membrane and metabolic activity. Gold nanorods CD33 conjugates significantly increase cell damage for low fluence laser and completely destroyed cancer cells after 3 pulses for low fluence (acute leukemia) and for high fluence laser as for HL-60 (acute) and for K-562 (chronicle) leukemia cells.

Abstract 4264: NFκB activation in mesenchymal stromal cells induced by leukemia-stroma interaction plays a central role in stroma-mediated chemo-resistance of leukemic cells

Within the bone marrow (BM) microenvironment, BM mesenchymal stromal cells (BM-MSC) produce cytokines and chemokines and initiate cellular adhesion-mediated signals that tightly regulate normal and malignant hematopoietic cell development. This rich environment serves as a sanctuary for malignant hematopoietic cells, offering protection from chemotherapeutic agents and promoting residual disease with greater potential for developing acquired drug resistance. In this study we utilized gene expression profiling (GEP) as a genome-wide exploratory approach to characterize changes caused by the interaction between leukemic cells and BM-MSC, and how these changes can contribute to the observed microenvironment-mediated chemoresistance. Co-culture of REH, a pre-B-ALL cell line, with normal-donor BM-MSCs for 48 hours upregulated a variety of genes encoding cytokines and chemokines in BM-MSCs such as CXCR6, CCL5, CCL2, IL32, IL34, IL8, IL6, CXCL12, and the VLA4 ligand VCAM-1. These microarray-based GEP findings were confirmed by qRT-PCR. Gene Set Enrichment Analysis (GSEA) implicated activation of NFκB in BM-MSCs as a potential cause of these changes. Similar upregulation of NFκB target genes was found in MSC co-cultured with the AML cell line OCI-AML3, suggesting that NFκB activation is a common consequence of leukemia-stroma interation. Given known paracrine functions of NFκB-regulated target genes such as IL-8, we hypothesized that stromal NFκB activation contributes to stroma-mediated chemo-resistance of leukemic cells. Stable transduction of BM-MSC to overexpress a super-repressor form of IαBβ (IαBβ-SR), to block canonical-pathway NFκB activation in the stromal compartment, significantly reduced the stroma-mediated chemo-resistance to Vincristine (VCR) of REH cells. NFκB inhibition using a specific IKKα inhibitor (MLN120B), affecting both BM-MSC and tumor cells, highly increased the apoptotic effects in leukemia-stroma co-cultures of VCR in REH cells and NALM6, another pre-B-ALL cell line. Similar results were obtained with CDDO-Me, another NFκB inhibitor. Altogether these results indicate that the interaction of leukemic cells with BM stromal cells activates NFκB in the stromal compartment, with subsequent transcriptional upregulation of a number of cytokines and chemokines ultimately favoring the survival of leukemic cells. We propose that targeting NFκB may ameliorate stroma-mediated chemo-resistance and help in eliminating bone-marrow resident leukemic cells.

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 4264. doi:1538-7445.AM2012-4264

Abstract 3021: FLT3/ITD acute myeloid leukemia (AML) cells show C-MYC- and PIM-1-mediated CDC25A overexpression despite the presence of intrinsic DNA damage

Activating mutations of FLT3 occur in 30% of patients with AML, and are associated with poor prognosis. It has been reported that FLT3/ITD AML cells are sensitive to MDM2 inhibition-induced apoptosis (Blood 2010;116:71) and indeed, FLT3 inhibition synergizes with MDM2 inhibition in the induction of apoptosis in FLT3/ITD AML (Leukemia 2010;24:33). Considering the rarity of TP53 mutations in FLT3/ITD AML, use of MDM2 inhibitors in AML with mutant FLT3 may offer clinical benefits. We investigated the FLT3/ITD-specific p53 signaling profile that may be associated with high susceptibility of FLT3/ITD cells to MDM2 inhibition. [Methods] The MDM2 inhibitor Nutlin-3a was used. Murine pro-B cells stably transfected with expression vectors that encoded wild-type human FLT3 (Ba/F3-FLT3 cells) or human FLT3 containing an ITD mutation (Ba/F3-ITD cells) were provided by Dr Donald Small and AML samples were obtained from patients after informed consent. Apoptosis was quantified by Annexin binding assay and cells were transfected by the Amaxa Nucleofector I. Statistical analysis was performed using t test or Mann-Whitney U test. [Results] Ba/F3-ITD cells were more susceptible to Nutlin-induced apoptosis but not to AraC or doxorubicin than Ba/F3-FLT3 cells; high Nutlin-3a sensitivity was associated with efficient BAX activation (P < .001). Basal levels of total and phospho p53 were 7 times higher in Ba/F3-ITD than in Ba/F3-FLT3 cells; levels of γH2AX, a DNA damage marker, were 6 times higher in Ba/F3-ITD than in Ba/F3-FLT3 cells, and reactive oxygen species levels were also high in Ba/F3-ITD cells (26.2 ± 3.2% vs 6.1 ± 0.1%; P < .001). Although steady state p53 activation was not sufficient to inhibit cell growth or induce cell death in Ba/F3-ITD cells, Nutlin-3a potently activated p53 signaling and induced apoptosis. Interestingly, CDC25A, which is specifically degraded in response to DNA damage, was 30 times higher in Ba/F3-ITD cells compared to Ba/F3-FLT3 cells, despite the presence of DNA damage. Among patient AML samples (n=37), CDC25A levels were significantly higher in samples with mutant FLT3 (n=16) than those with wild-type FLT3 (n=21) (1.7 ± 1.2 vs 17.1 ± 6.7; P < .001). Knockdown experiments showed that CDC25A over-expression was partially induced by C-MYC and PIM-1. Nutlin-3a reduced CDC25A mRNA levels by 63.9 ± 0.4 % (P < 0.01). The proteasome inhibitor MG132 or the pan-caspase inhibitor Z-VAD-FMK did not rescue the CDC25A reduction. [Conclusion] CDC25A over-expression was closely associated with FLT3/ITD in AML. FLT3/ITD cells showed C-MYC- and PIM-1-mediated CDC25A over-expression despite the presence of intrinsic DNA damage. CDC25A over-expression has been reported in a variety of human cancers, and CDC25A has been considered a therapeutic target. CDC25A down-regulation may be potential mechanism by which MDM2 inhibition induces cell death in FLT3/ITD AML cells.

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 3021. doi:1538-7445.AM2012-3021

Abstract 3871: Insulin-like growth factor 1 receptor (IGF1R) inhibitor BMS754807 is active against FLT3-ITD mutated acute myelogenous leukemia and activity is p53 dependent

The Internal tandem mutation (ITD) in the FLT3 gene is associated with shorter remission duration, overall survival and relapse free survival in patients with normal karyotype acute myelogenous leukemia (AML). FLT3-ITD inhibitors are in clinical development but single agent clinical activity is of limited duration with activation of parallel signaling pathways potentially contributing to most relapses thus highlighting the need for new agents. Because common signaling pathways are activated downstream of FLT3 and IGF1R, we investigated the preclinical activity of IGF1R antagonist BMS754807 against AML cells with FLT3-ITD mutations. Results: BMS 754807 induced apoptosis (Annexin V binding by flow cytometry) in MOLM13 cells (AML cell line with FLT3-ITD mutation and wild type p53) at 48 hrs at submicromolar concentrations, while OCI AML3 cells (p53 and FLT3 wild type) were resistant. Similarly, murine BAF3 cells expressing human FLT3-ITD underwent prompt apoptosis with BMS 754807 while the same cells with human wt-FLT3 were resistant to BMS 754807(IC50s 2.5 μmol vs >10 μmol). Western blot analysis confirmed reduction in FLT3, Akt, ERK, S6 ribosomal protein and GSK3 beta phosphorylation and increase in p53 levels in MOLM13 cells. Interestingly, apoptosis induction was not associated with caspase activation. Moreover, apoptosis induction by BMS 754807 appeared to be p53 dependent as MOLM13 cells with stable expression of short hairpin RNA (sh-RNA) targeting p53 (p53-shRNA) were resistant, while MOLM13 cells expressing scramble sh-RNA underwent apoptosis comparable to parental MOLM13 cells. Surface expression of IGF1R was comparable among parental and p53-shRNA MOLM13 cells. Apoptosis induction by BMS 754807 in p53-WT and FLT3-ITD cells was associated with phosphorylation of p53 at serine 15. Conclusion: BMS 754807 has selective activity against AML cells with FLT3-ITD mutation and this activity is p53 dependent and associated with phosphorylation of p53 at serine 15. Results suggest that IGF1R inhibition has therapeutic potential as novel targeted therapy for AML with FLT3-ITD mutation.

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 3871. doi:1538-7445.AM2012-3871

Abstract 3659: The AKT inhibitor MK-2206 promotes apoptosis in acute myeloid leukemia cells

The need for improved therapies for acute myeloid leukemia (AML) is urgent as the disease is still highly fatal. Protein Kinase B (AKT) activation has been shown to predict poor clinical outcome for patients with AML. In 253 newly diagnosed AML cases, we have found that AKT phosphorylation on Thr308 analyzed by reverse-phase protein arrays was significantly higher in patients with unfavorable cytogenetics (p=0.037). The adverse prognostic factor of high levels of pAKT was observed among patients with intermediate-risk cytogenetics (p=0.013), as it was associated with an inferior survival (median survival 44.2 weeks) compared to patients with low or intermediate pAKT (78.7 weeks). Recently, Merck Sharp & Dohme Corp. has developed a compound, MK-2206, that is a highly specific allosteric inhibitor for all three AKT isoforms. In the current study, we have determined that MK-2206 as a single agent used at clinically achievable concentrations suppresses cell growth of a variety of AML derived cell lines including OCI-AML3, U937, and MOLM13. MK-2206 can also induce apoptosis in blast cells derived from AML patients. Consistent with its role as an AKT inhibitor, the drug suppresses phosphorylation of AKT at serine 473 and inhibits phosphorylation of AKT downstream targets including S6 ribosomal protein, 4-EBP1, and PRAS40 in the AML cells. We recently identified that low expression of the PP2A isoform that acts as the AKT phosphatase (i.e. the one containing the B55α subunit) in AML negatively correlates with AKT T308 phosphorylation and activation in a cohort of 511 AML patients (Ruvolo et al Leukemia, 2011). Patients with low B55α expression exhibited shorter complete remission duration. We suppressed B55α expression by shRNA in OCI-AML3 cells to determine if loss of the AKT phosphatase promotes AKT activation and chemoresistance. Cells with reduced B55α exhibited higher levels of AKT phosphorylation and were more resistant to killing by the conventional chemotherapy agent AraC. OCI-AML3 B55α shRNA transductant cells were also more resistant to MK-2206 compared to cells expressing control non-specific shRNA. These results suggest that AKT phosphatase activity in AML may affect response to MK-2206. A recent study in liver cancer demonstrated that MK-2206 synergized with the multi-kinase inhibitor Sorafenib. Since Sorafenib targets the Fms-like tyrosine kinase 3 (FLT3) and mutations that activate the kinase in AML confer poor prognosis, we examined if MK-2206 could synergize with Sorafenib to kill leukemia cells with mutation of FLT3 internal tandem duplication (ITD) mutation. The combination of MK-2206 and Sorafenib was effective at killing MOLM13 cells and AML blast cells with the FLT3-ITD. Taken together, these findings suggest that MK-2206 may be effective to block AKT signaling pathways and could be beneficial as a therapeutic agent perhaps as a single agent or in combination with a drug such as Sorafenib in the therapy of AML.

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 3659. doi:1538-7445.AM2012-3659

Abstract 2008: Broad spectrum BH3 mimetic BI-97D6 induces apoptosis of acute myeloid leukemia cells even when co-cultured with supporting stromal cells

The BCL2 family of proteins contains members that possess potent anti-apoptotic function (e.g. BCL2, MCL-1) as well as pro-death members (e.g. BAX, BIM). Aberrant expression of anti-apoptotic members such as BCL2 or suppression of pro-apoptotic members such as BAX or BIM can lead to tumor formation and promote resistance to therapy in many types of cancer including Acute Myeloid Leukemia (AML). A recent model of tumorigenesis/chemoresistance suggests cancer cells become dependent on pro-survival molecules including BCL2 and MCL-1. This model suggests that the “addicted” malignant cells can be eliminated by targeting the survival molecule that supports the tumor cell. Recent efforts to target a broad group of BCL2 family members has evolved using small molecule inhibitors to target the BH3 domain since the association between the two groups of BCL2 family members involves this domain. While compounds including ABT-737 have shown promise for treatment of some cancers, the compound binds poorly to MCL-1 and related BCL2 family members such as BCL2A1 and thus cells that rely on these anti-apoptotic BCL2 family members display resistance to the compound. Furthermore, we and others have recently found that ABT-737 can promote MCL-1 expression likely via a mechanism involving ERK. A superior approach would be to develop a single BH-3 mimetic agent that is effective at inhibiting MCL-1 as well as other BCL2 family members. In the current study, we examine if the Apogossypol analog BI-97D6 (Wei et al, J Med Chem. 2010), which has efficacy against MCL-1 as well as BCL2 and BCL-XL, has potential an effective anti-leukemia agent. BI-97D6 is novel as an Apogossypol compound since it acts as a true BH3 mimetic. Other gossypol and apopgossypol compounds have been shown to promote death by ER stress mediated mechanisms. In AML cells, we found that BI-97D6 does not induce CHOP expression or JNK activation, which are features of ER stress induction. Bax/Bak knock out MEFs were resistant BI-97D6, indicating that the drug acts specifically as a BH3 mimetic. BI-97D6 interferes with the association of MCL-1 with BIM and induces the death conformation of BAX in OCI-AML3 cells. The drug is effective at killing a variety of AML derived cell lines with IC50 values at 72 hours in the nanomolar range (i.e. below 50 nM for OCI-AML3, HL60, and MOLM13). Bone marrow-derived mesenchymal stromal cells (BM MSC) have been shown to protect leukemia cells from conventional chemotherapy agents such as AraC. There was no difference in BI-97D6 mediated killing of OCI-AML3 cells whether the cells were treated in co-culture with BM MSC or alone. These results suggest that BI-97D6 could have efficacy against AML, regardless of MCL-1 levels, which is not diminished by the protective effects of the BM microenvironment. Further mechanistic details are under investigation.

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 2008. doi:1538-7445.AM2012-2008

[Measurement of ocular lens ionizing radiation exposure after radioiodine therapy]

AIM

Current reports for the radiation cataracts contained a warning for deterministic effects at 1-2 Gy radiation single exposure for lens. Recently, the German Radiation Protection Board (SSK) published a document (234. SSK-Board) in that threshold dose for radiation cataracts is claimed at 0.5 Gy. The lens of the eye is recognized as one of the most radiosensitive tissues in the human body, and the International Commission on Radiological Protection (ICRP 103) has defined a limit of 150 mSv for its exposure.Recently, the ICRP lowered this limit down to 20 mSv per year.However, this limit does not apply to patients. Therefore, the question of the lens radiation exposure for patients underwent a radioiodine therapy (RIT) is a point at issue.

PATIENTS, METHODS

A total of 41 patients (age: 22-92 years) underwent a radioiodine therapy were included in the study. Optical stimulated luminescence dosimeters were used to measure the radiation exposure. The dosimeters were fastened nearby the patient's eye lens. The measurement was carried out up to 48 h after radioiodine application and the patients were divided into three groups. Group 1: patients underwent a diagnostic 131I whole body scan (mean activity: 370 MBq); group 2: thyriod carcinoma patients under RIT (mean activity: 3700 MBq); group 3: hyperthyroid patients under RIT (activity: 180-1237 MBq).

RESULTS

The cumulative exposure of the eye lens during the stay at the therapy unit (48 h) was 4.8 ± 0.7 mGy in group 1, 24.5-50.5 mGy in group 2 and 2.7-26.3 mGy in group 3, respectively. For the calculation of the expected cumulative dose, including follow-up after patient's dismissal, the effective half-lives were involved. The cumulative doses were obtained to be 6 ± 1 mGy in the first group, 63 ± 15 mGy in the second and 5-148 mGy in the third.

CONCLUSION

The results show that there exists a low risk for radiation cataract in a nuclear medicine therapy unit. After serial radioiodine therapies radiation-induced lens opacity cannot be expected.

Targeting survivin in leukemia

Survivin, a member of the inhibitors of apoptosis family of proteins, is one of the most frequently upregulated transcripts in solid tumors and hematopoietic malignancies. Survivin’s importance in tumorigenesis is attributed to the fact that it has two functions: to suppress apoptosis and to regulate cell division. The combination of these two functions gives a significant growth and survival advantage on neoplastic cells. This, together with its overexpression in cancer cells, its association with resistance to chemo- and other therapies, and the resulting poor prognosis observed in certain tumors makes survivin a promising target for therapy. In this review, we describe what is currently know about survivin regulation in normal and malignant cells, focusing in particular on the aberrant expression of the protein in leukemia and its possible clinical implications. Various strategies to target survivin will also be described.

Omental adipose tissue-derived stromal cells promote vascularization and growth of endometrial tumors

PURPOSE

Adipose tissue contains a population of tumor-tropic mesenchymal progenitors, termed adipose stromal cells (ASC), which engraft in neighboring tumors to form supportive tumor stroma. We hypothesized that intra-abdominal visceral adipose tissue may contain a uniquely tumor-promoting population of ASC to account for the relationship between excess visceral adipose tissue and mortality of intra-abdominal cancers.

EXPERIMENTAL DESIGN

To investigate this, we isolated and characterized ASC from intra-abdominal omental adipose tissue (O-ASC) and characterized their effects on endometrial cancer progression as compared with subcutaneous adipose-derived mesenchymal stromal cells (SC-ASC), bone marrow-derived mesenchymal stromal cells (BM-MSC), and lung fibroblasts. To model chronic recruitment of ASC by tumors, cells were injected metronomically into mice bearing Hec1a xenografts.

RESULTS

O-ASC expressed cell surface markers characteristic of BM-MSC and differentiated into mesenchymal lineages. Coculture with O-ASC increased endometrial cancer cell proliferation in vitro. Tumor tropism of O-ASC and SC-ASC for human Hec1a endometrial tumor xenografts was comparable, but O-ASC more potently promoted tumor growth. Compared with tumors in SC-ASC-injected mice, tumors in O-ASC-injected mice contained higher numbers of large tortuous desmin-positive blood vessels, which correlated with decreased central tumor necrosis and increased tumor cell proliferation. O-ASC exhibited enhanced motility as compared with SC-ASC in response to Hec1a-secreted factors.

CONCLUSIONS

Visceral adipose tissue contains a population of multipotent MSCs that promote endometrial tumor growth more potently than MSCs from subcutaneous adipose tissue. We propose that O-ASCs recruited to tumors express specific factors that enhance tumor vascularization, promoting survival and proliferation of tumor cells.

Prognostic significance of alterations in IDH enzyme isoforms in patients with AML treated with high-dose cytarabine and idarubicin

BACKGROUND

IDH1 and IDH2 gene mutations are novel, recurring molecular aberrations among patients with normal karyotype acute myeloid leukemia (AML).

METHODS

Among 358 patients with AML treated on 4 protocols using high-dose ara-C plus idarubicin induction, pretreatment samples were available for 170 (median age 53 years, [range, 17-73]; 96% ≤65) and were evaluated for IDH1R132, IDH2R172, and IDH2R140 mutations or the codon 105 single nucleotide polymorphism (SNP) in IDH1.

RESULTS

IDH1 and IDH2 mutations were present in 12 (7%) and 24 (14%) of patients, and IDH1 G105 SNP in 24 (14%). Overall, 52 (30%) patients had IDH gene alterations. There was no association with complete response (CR), remission duration, overall survival, and event-free survival and any of the IDH alterations, and no association with a higher CR rate or survival with the 4 regimens for the 52 patients with aberrant IDH. Among the patients with diploid karyotype and NPM1(mut) FLT3(WT) genotype, those with IDH1 or IDH2 mutations had an inferior outcome.

CONCLUSIONS

IDH aberrations and IDH1 codon 105 SNP occur in about 30% of younger patients with AML, mostly with diploid karyotype. Using high-dose ara-C-based induction regimens, we did not detect an association with outcome for any of the aberrations.

Phosphorylated CXCR4 is associated with poor survival in adults with B-acute lymphoblastic leukemia

BACKGROUND

CXC chemokine receptor 4 (CXCR4) is activated by phosphorylation (pCXCR4) and is essential for the migration of hematopoietic precursors to bone marrow. CXCR4 overexpression predicts a poor prognosis in patients with acute myeloid leukemia. Data regarding the prognostic impact of CXCR4 in patients with B-acute lymphoblastic leukemia (B-ALL) are sparse and limited to the pediatric population.

METHODS

The authors analyzed CXCR4 and pCXCR4 expression in 54 adults with newly diagnosed B-ALL. CXCR4 was assessed by flow cytometry (FC) and immunohistochemistry (IHC) using an anti-CXCR4 antibody. pCXCR4 expression was assessed using an anti-pCXCR4 antibody.

RESULTS

The study group included 30 men and 24 women with a median age of 42 years (range, 17-84 years). Philadelphia chromosome was present in 19 patients. The median follow-up was 16 months (range, 17-84 months). Forty-nine patients had a complete response, and 12 patients relapsed with a median relapse free survival >120 weeks. Fifteen patients (28%) died with a median survival >125 weeks. CXCR4 detected by FC and IHC was highly correlated (P < .001). CXCR4 was not associated with clinical or laboratory findings or survival. In contrast, pCXCR4 was associated with higher leukocyte count (P = .006) and serum bilirubin level (P = .03). In multivariate analysis, pCXCR4 expression (P = .027), high serum creatinine level (P < .01), presence of the Philadelphia chromosome (P = .017), and late clinical response (P < .001) were associated with worse overall survival.

CONCLUSIONS

The current results indicated that detection of the activated form of CXCR4, pCXCR4, provides independent prognostic information in adult patients with B-ALL.