Hypoxia promotes erythroid differentiation through the development of progenitors and proerythroblasts

Oxygen is a critical noncellular component of the bone marrow microenvironment that plays an important role in the development of hematopoietic cell lineages. In this study, we investigated the impact of low oxygen (hypoxia) on ex vivo myeloerythroid differentiation of human cord blood-derived CD34⁺ hematopoietic stem and progenitor cells. We characterized the culture conditions to demonstrate that low oxygen inhibits cell proliferation and causes a metabolic shift in the stem and progenitor populations. We found that hypoxia promotes erythroid differentiation by supporting the development of progenitor populations. Hypoxia also increases the megakaryoerythroid potential of the common myeloid progenitors and the erythroid potential of megakaryoerythroid progenitors and significantly accelerates maturation of erythroid cells. Specifically, we determined that hypoxia promotes the loss of CD71 and the appearance of the erythroid markers CD235a and CD239. Further, evaluation of erythroid populations revealed a hypoxia-induced increase in proerythroblasts and in enucleation of CD235a⁺ cells. These results reveal the extensive role of hypoxia at multiple steps during erythroid development. Overall, our work establishes a valuable model for further investigations into the relationship between erythroid progenitors and/or erythroblast populations and their hypoxic microenvironment.

Pan-myeloid Differentiation of Human Cord Blood Derived CD34+ Hematopoietic Stem and Progenitor Cells

Ex vivo differentiation of human hematopoietic stem cells is a widely used model for studying hematopoiesis. The protocol described here is for cytokine induced differentiation of CD34⁺ hematopoietic stem and progenitor cells to the four myeloid lineage cells. CD34⁺ cells are isolated from human umbilical cord blood and co-cultured with MS-5 stromal cells in the presence of cytokines. Immunophenotypic characterization of the stem and progenitor cells, and the differentiated myeloid lineage cells are described. Using this protocol, CD34⁺ cells may be incubated with small molecules or transduced with lentiviruses to express myeloid disease mutations to investigate their impact on myeloid differentiation.

Myeloid Disease Mutations of Splicing Factor SRSF2 Cause G2-M Arrest and Skewed Differentiation of Human Hematopoietic Stem and Progenitor Cells

Myeloid malignancies, including myelodysplastic syndromes, chronic myelomonocytic leukemia, and acute myeloid leukemia, are characterized by abnormal proliferation and differentiation of hematopoietic stem and progenitor cells (HSPCs). Reports on analysis of bone marrow samples from patients have revealed a high incidence of mutations in splicing factors in early stem and progenitor cell clones, but the mechanisms underlying transformation of HSPCs harboring these mutations remain unknown. Using ex vivo cultures of primary human CD34⁺ cells as a model, we find that mutations in splicing factors SRSF2 and U2AF1 exert distinct effects on proliferation and differentiation of HSPCs. SRSF2 mutations cause a dramatic inhibition of proliferation via a G2-M phase arrest and induction of apoptosis. U2AF1 mutations, conversely, do not significantly affect proliferation. Mutations in both SRSF2 and U2AF1 cause abnormal differentiation by skewing granulo-monocytic differentiation toward monocytes but elicit diverse effects on megakaryo-erythroid differentiation. The SRSF2 mutations skew differentiation toward megakaryocytes whereas U2AF1 mutations cause an increase in the erythroid cell populations. These distinct functional consequences indicate that SRSF2 and U2AF1 mutations have cell context-specific effects and that the generation of myeloid disease phenotype by mutations in the genes coding these two proteins likely involves different intracellular mechanisms. Stem Cells 2018;36:1663-1675.

Targeting polo-like kinase 1, a regulator of p53, in the treatment of adrenocortical carcinoma

Background

Adrenocortical carcinoma (ACC) is an aggressive cancer with a 5 year survival rate of 20–30 %. Various factors have been implicated in the pathogenesis of ACC including dysregulation of the G2/M transition and aberrant activity of p53 and MDM2. Polo-like kinase 1 (PLK-1) negatively modulates p53 functioning, promotes MDM2 activity through its phosphorylation, and is involved in the G2/M transition. Gene expression profiling of 44 ACC samples showed that increased expression of PLK-1 in 29 % of ACC. Consequently, we examined PLK-1’s role in the modulation of the p53 signaling pathway in adrenocortical cancer.

Methods

We used siRNA knock down PLK-1 and pharmacological inhibition of PLK-1 and MDM2 ACC cell lines SW-13 and H295R. We examined viability, protein expression, p53 transactivation, and induction of apoptosis.

Results

Knocking down expression of PLK-1 with siRNA or inhibition of PLK-1 by a small molecule inhibitor, BI-2536, resulted in a loss of viability of up to 70 % in the ACC cell lines H295R and SW-13. In xenograft models, BI-2536 demonstrated marked inhibition of growth of SW-13 with less inhibition of H295R. BI-2536 treatment resulted in a decrease in mutant p53 protein in SW-13 cells but had no effect on wild-type p53 protein levels in H295R cells. Additionally, inhibition of PLK-1 restored wild-type p53’s transactivation and apoptotic functions in H295R cells, while these functions of mutant p53 were restored only to a smaller extent. Furthermore, inhibition of MDM2 with nutlin-3 reduced the viability of both the ACC cells and also reactivated wild-type p53′s apoptotic function. Inhibition of PLK-1 sensitized the ACC cell lines to MDM2 inhibition and this dual inhibition resulted in an additive apoptotic response in H295R cells with wild-type p53.

Conclusions

These preclinical studies suggest that targeting p53 through PLK-1 is an attractive chemotherapy strategy warranting further investigation in adrenocortical cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s40169-015-0080-3) contains supplementary material, which is available to authorized users.

Abstract 1781: Whole-genome and RNA sequencing identify a novel recurrent translocation in adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is a lethal tumor of the adrenal cortex with limited treatment options. The only possibility for cure is complete surgical resection, but 50-70% of patients present with metastatic disease, precluding curative surgery. The outcome for patients with ACC has remained unchanged in the past 25 years, with the overall 5-year survival of patients undergoing surgical resection being ∼40%. Patients that present with advanced disease fare considerably worse with 5-year survival rates of 10-20%. The standard chemotherapy regimen of mitotane (the only approved agent), etoposide, doxorubicin, and cisplatin, has a response rate of 23.2%. A better understanding of pathobiology is needed to improve the treatment results for this disease.

Previous genomic studies combined with expression microarray studies have implicated lack of H19 expression coupled with IGF2 over-expression, beta-catenin activation, and loss of p53 pathway function as important events in ACC, but no single alteration has been seen in all ACC. We used a combination of whole genome sequencing, exome sequencing, and RNA-sequencing on three tumor/normal pairs from patients. Using data from spectral karyotyping of the two ACC cell lines, SW-13 and NCI-H295R, we mined the sequencing data for structural rearrangements in regions of common breakpoints. We identified

a novel recurrent translocation, t(4;8)(p16.2;p23.1) in all three tumors that was not present in the normal sequence. Using fluorescent in situ hybridization (FISH) we validated the translocation in the three tumors and both SW-13 and H295R. An additional five of five ACC scored positive for the translocation, as did three malignant non-ACC tumors (malignant pheochromocytoma, pancreatic neuroendocrine tumor, and carcinoid) suggesting that this finding has implications beyond ACC. The recurrent translocation t(4;8) (p16.2; p23.1) involves two genes of unknown function, BC042823 (uc003gho.2, IMAGE:5275587) on chromosome 4 and BC030294 (ucoo3wrb.1, IMAGE:5396854) on chromosome 8. RNA- sequencing data and RT-PCR with primers designed to both derivative chromosomes revealed transcription from both derivative chromosomes. The cDNA products were sequenced by Sanger sequencing and show partial homology to a non-coding RNA, LOC100506990, at chr8:12,338,893-12,452,929. RNA-sequencing data revealed this locus is highly transcribed in normal adrenal gland but reduced in expression in the three ACCs. In contrast to other recurrent translocations previously found in other cancers, this translocation is only present in 18-30% of the tumor nuclei scored by FISH, suggesting that it is a necessary alteration in malignant progression, but underscoring the question of how it might cooperate with events in other sub-clones to initiate tumor formation and progression.

Citation Format: Michael J. Demeure, Kaiti Schwartz, Aditi Bapat, Claire Linnehan, Hollie Benson, Rebecca Reiman, Lori Phillips, Christophe Legendre, Raghu Metpally, Ahmet Kurdoglu, David Craig, John Carpten, Winnie S. Liang, Waibhav Tembe, Kimberly J. Bussey. Whole-genome and RNA sequencing identify a novel recurrent translocation in adrenocortical carcinoma. [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 1781. doi:10.1158/1538-7445.AM2013-1781

Novel small-molecule inhibitor of apurinic/apyrimidinic endonuclease 1 blocks proliferation and reduces viability of glioblastoma cells

Apurinic/apyrimidinic (AP) endonuclease 1 (Ape1) is an essential DNA repair protein that plays a critical role in repair of AP sites via base excision repair. Ape1 has received attention as a druggable oncotherapeutic target, especially for treating intractable cancers such as glioblastoma. The goal of this study was to identify small-molecule inhibitors of Ape1 AP endonuclease. For this purpose, a fluorescence-based high-throughput assay was used to screen a library of 60,000 small-molecule compounds for ability to inhibit Ape1 AP endonuclease activity. Four compounds with IC(50) values less than 10 microM were identified, validated, and characterized. One of the most promising compounds, designated Ape1 repair inhibitor 03 [2,4,9-trimethylbenzo[b][1,8]-naphthyridin-5-amine; AR03), inhibited cleavage of AP sites in vivo in SF767 glioblastoma cells and in vitro in whole cell extracts and inhibited purified human Ape1 in vitro. AR03 has low affinity for double-stranded DNA and weakly inhibits the Escherichia coli endonuclease IV, requiring a 20-fold higher concentration than for inhibition of Ape1. AR03 also potentiates the cytotoxicity of methyl methanesulfonate and temozolomide in SF767 cells. AR03 is chemically distinct from the previously reported small-molecule inhibitors of Ape1. AR03 is a novel small-molecule inhibitor of Ape1, which may have potential as an oncotherapeutic drug for treating glioblastoma and other cancers.

Abstract 1963: Novel small molecule inhibitor of the endonuclease function of the APE1 DNA repair and redox signaling enzyme blocks proliferation and reduces viability of glioblastoma cells

The DNA Base Excision Repair (BER) pathway repairs DNA damaged by endogenous and exogenous agents including chemotherapeutic agents. Removal of the damaged base by a DNA glycosylase creates an apurinic / apyrimidinic (AP) site. AP Endonuclease1 (APE1), a critical component in this pathway that hydrolyzes the phosphodiester backbone 5’ to the AP site. Failure to repair AP sites leads to DNA strand breaks, enhanced cytotoxicity, cell cycle arrest and increased apoptosis. In addition to APE1's role in repair, it also functions as a redox signaling factor to activate key transcription factors such as AP1 (Fos/Jun), p53, NFkB, HIF-1α, and others controlling the expression of genes important for cell survival and cancer promotion and progression. APE1 has been shown to have an altered level of expression in a variety of cancers including pancreatic, breast, prostate, gliomas, sarcomas and others. High APE1 expression has also been associated with chemoradiotherapy poor outcome, poor complete response rate, shorter local relapse-free interval, poorer survival and high angiogenesis. Due to APE1's critical role in repairing chemotherapy- and IR-induced DNA damage, we hypothesize that inhibiting APE1's DNA repair activity would not only allow us to further elucidate the role of DNA repair that elevated levels of APE1 play in tumors, but would also allow us to delineate the importance of its DNA repair and redox functions in normal cellular processes. While reducing the amount of APE1 in cancer cells using anti-sense oligonucleotide technology and RNA interference sensitizes tumor cells to chemotherapeutic agents, it may not be the most efficacious route of treatment.

We have concluded a screen of small molecule compounds for their ability to inhibit APE1 AP endonuclease activity. Four families of compounds with IC50 values less than 10 μM were identified, validated and characterized. One of the most promising compounds, designated AR03 inhibited cleavage of AP sites in vivo in SF767 glioblastoma cells, in vitro in whole cell extracts and inhibits purified human APE1 in vitro. AR03 has low affinity for dsDNA and it does not affect the redox function of APE1. AR03 also potentiates the cytotoxicity of methyl methane sulfonate (MMS) and temozolomide (TMZ) in SF767 cells. AR03 is chemically distinct from all the previously reported small molecule inhibitors of APE1 which are either ineffective in vivo due to poor cellular uptake, not tested in cellular based scenarios, or lacking in specificity.

Thus, AR03 is a novel small molecule inhibitor of APE1, which may have potential as an oncotherapeutic drug for treating glioblastoma and other cancers. Additional studies are needed to determine the effect of AR03 in combination with other cancer chemotherapeutic agents, in combination with other APE1 inhibitors or other emerging BER targets such as PARP.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1963.

Semi-automated high-throughput fluorescent intercalator displacement-based discovery of cytotoxic DNA binding agents from a large compound library

High-throughput fluorescent intercalator displacement (HT-FID) was adapted to the semi-automated screening of a commercial compound library containing 60,000 molecules resulting in the discovery of cytotoxic DNA-targeted agents. Although commercial libraries are routinely screened in drug discovery efforts, the DNA binding potential of the compounds they contain has largely been overlooked. HT-FID led to the rapid identification of a number of compounds for which DNA binding properties were validated through demonstration of concentration-dependent DNA binding and increased thermal melting of A/T- or G/C-rich DNA sequences. Selected compounds were assayed further for cell proliferation inhibition in glioblastoma cells. Seven distinct compounds emerged from this screening procedure that represent structures unknown previously to be capable of targeting DNA leading to cell death. These agents may represent structures worthy of further modification to optimally explore their potential as cytotoxic anti-cancer agents. In addition, the general screening strategy described may find broader impact toward the rapid discovery of DNA targeted agents with biological activity.

Assessing the impact of a targeted educational initiative on colorectal cancer lymph node retrieval: A Fox Chase Cancer Center Partners' quality initiative

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Background: The retrieval of ≥12 lymph nodes in a colorectal cancer surgical specimen is an established quality metric. The impact of targeted education to improve nodal yield at community hospitals has not been studied. We initiated an intensive educational program through the Fox Chase Cancer Center Partner (FCCCP) hospitals to improve nodal retrieval in colon cancer specimens. Methods: At 12 FCCCP community hospitals from 2004–05, educational initiatives were conducted by FCCC staff and included group presentations at hospital tumor boards, cancer and quality committees, and regional CME. Individual presentations to pathologists and surgeons were held. Tumor registry data were retrospectively collected from FCCCP from 2003 (pre-intervention) to 2006 (post-intervention) for patients undergoing curative colon cancer surgery. Data abstracted were age, sex, race, stage, surgical procedure, and total number of nodes examined. The primary end point was % surgical specimens with ≥12 lymph nodes. Obtaining at least 250 records per year would allow ≥90% power to detect a change from a baseline level of ∼40% to ≥50% after intervention. Results: Data from 4,208 patients from 12 FCCCP hospitals were collected. Overall characteristics: male/female (48%/52%), race (W 83%, AA 7%, other 10%), age (<50:6%, 50–70: 34%, >70:60%), node ± (39%/61%). The % of colon cancer operations with ≥12 nodes significantly increased over the four years of the study (Table, p<.00001). This difference persisted when pooling years before and after the intervention (2003–04 vs. 2005–06, p <0.0001). There was no difference in nodal yield between two pre-intervention years (2003 vs. 2004, p=0.1). No differences in other characteristics such as age, sex, race, or % lymph node positive were noted between years. Conclusions: A multi-intervention targeted educational initiative in a large community cancer network is feasible and associated with increased colon cancer nodal retrieval.

[Table: see text]

No significant financial relationships to disclose.

Going ape as an approach to cancer therapeutics

The DNA base excision repair (BER) pathway repairs alkylation and oxidative DNA damage caused by endogenous and exogenous agents, including chemotherapeutic agents. Upon removal of the damaged base AP endonuclease 1 (Ape1), a critical component of the pathway cleaves the abasic site to facilitate repair. Ape1 is a multifunctional protein which plays a role not only in DNA repair but it also functions as a reduction-oxidation factor, known as Ref-1 in the literature, to increase the DNA binding ability of several transcription factors involved in different growth signaling pathways. Elevated levels of Ape1 have been linked to resistance to chemotherapy, poor prognosis, and poor survival. Reducing the amount of Ape1 protein in cancer cells and tumors using RNA interference and anti-sense oligonucleotide technology sensitizes mammalian tumor cells to a variety of laboratory and chemotherapeutic agents. Therefore, selective inhibition of Ape1's DNA repair activity is a promising avenue to develop novel cancer therapeutics.

Membrane thickness design of implantable bio-MEMS sensors for the in-situ monitoring of blood flow

This paper presents some ideas for the membrane thickness design of of implantable bio-micro-electro-mechanical systems (bio-MEMS) for the in situ monitoring of blood flow. The objective is to develop a smart wireless sensing unit for non-invasive early stenosis detection in heart bypass grafts. The design includes considerations of nonlinear material models, multiscale blood flows, and appropriate analyical models for data interpretation, as well as preliminary studies of the pressure and flow sensing concepts. The paper also examines the use of surface coatings for the design on biocompatibility and non-adhesion of blood platelets and constituents. The implications of the results are discussed for in vivo deployment of such sensor systems.

Pentostatin increases the acute toxicity of high dose cyclophosphamide

One dose of pentostatin was added to a standard cyclophosphamide (CY) based transplant regimen in two patients in an attempt to decrease the rate of non-engraftment in haploidentical allogeneic BMT. Despite a normal cardiac history and evaluation prior to transplant, both patients suffered fatal cardiac toxicity within 48 h of receiving the chemotherapy. This phenomenon was further investigated in an animal model. Laboratory rats were treated with progressive doses of CY in a range that produces acute cardiac toxicity. Successive groups of rats were treated with either pentostatin or fludarabine and CY at 400 mg/kg. Neither pentostatin nor fludarabine alone produced early mortality. However, a marked increase in early mortality was noted in those animals treated with pentostatin and high-dose CY. The addition of fludarabine did not increase the early toxicity of CY. Autopsy revealed no gross or microscopic abnormalities in the animals. The implications of adding agents that interfere with adenosine metabolism to CY based transplant regimens is discussed.