Abstract GMM-017: UPREGULATION OF MIR-328 CONTRIBUTES TO OVARIAN CANCER STEM CELL MAINTENANCE BY DOWNREGULATING DDB2

Cancer stem cells (CSCs) are a particular subpopulation of cells that are characterized by self renewal, differentiation and enhanced tumorigenicity. They are responsible for tumor metastasis, relapse and development of drug resistance. Thus, eradication of CSCs is essential for improved patient prognosis. Micro RNAs are a group of small non-coding, endogenous RNAs that are found to regulate cancer stem cell characteristics by binding to mRNA in a sequence specific manner. In ovarian cancers, a wide array of Micro RNAs have been found to show differential expression of which miR328-3p deserves special mention. In this study, a Micro RNA Nanostring profile analysis reveals a significant upregulation of miR-328-3p in ovarian cancer stem cells isolated from both ovarian cancer cell lines and primary ovarian tumors as compared to their corresponding bulk cells. Moreover, it was found that inhibition of miR-328 limited the CSC population in ovarian cancer cells whereas overexpression of miR-328 enriched the CSC population, thus accounting for miR-328 as an onco-miRNA. The upregulation of miR-328 not only increased the percentage of ALDH+ cells in ovarian cancer bulk cells, but also increased the tumorigenicity and sphere formation ability. This was supported by the orthotopic ovarian xenograft assay. Further investigation revealed that reduced phosphorylation of Erk in ovarian cancer stem cells owing to reduced levels of Reactive Oxygen species (ROS) could be a prospective mechanism behind elevated miR328 expression and maintenance of CSC characteristics. Inhibition of phosphorylated Erk expression in ovarian cancer bulk cells by use of commercially available Erk inhibitor, U0126, led to a significant increase in miR328 expression. Simultaneously, upregulation of phosphorylated Erk in ovarian cancer stem cells not only reduced miR328 expression, but also displayed a significant reduction in expression of cancer stem cell markers (Oct4, Sox2, Nanog), sphere formation ability and tumorigenesis. We obtained a similar trend of results on regulating the expression of pErk by use of Reactive Oxygen Species to ovarian cancer cells. These data further helped us confirm our speculation that reduced ROS promotes the maintenance of CSCs characteristics through inactivation of Erk signalling pathway. Besides, we also identified DDB2 as a direct target of miR328. Our previous findings demonstrate that DDB2 is able to limit ovarian CSC population by disrupting their self renewal capacity. Thus, we conclude that elevated miR328 in ovarian CSCs, resulting from inactivated Erk1/2 activity, is responsible for maintenance of stemness by inhibition of DDB2 expression. Targeting miR-328 could therefore be a novel therapeutic strategy to eradicate CSCs in ovarian cancer.

Citation Format: Amit Kumar Srivastava, Tiantian Cui, Ananya Banerjee, Chunhua Han, Shurui Cai, Lu Liu, Dayong Wu1, Ri Cui, Zaibo Li, Xiaoli Zhang, Guozhen Xie, Selvendiran Karuppalyah, Adam Karpf, Jinsong Liu, David Cohn, Qi-En Wang. UPREGULATION OF MIR-328 CONTRIBUTES TO OVARIAN CANCER STEM CELL MAINTENANCE BY DOWNREGULATING DDB2 [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr GMM-017.

Abstract 5380: Synergistic effects of clofarabine and decitabine in acute myeloid leukemia

Clofarabine (CLO) is a purine nucleoside analog with promising efficacy in acute myeloid leukemia (AML). Its mechanism of action involves inhibition of the ribonucleotide reductase (RR) that converts nucleotide diphosphates to the corresponding deoxynucleotide diphosphates. Expression of the small RR subunit, p53R2 (product of RRM2B), demonstrated that a shorter protein is associated with CLO resistance. We have also shown that decitabine (DEC), another active drug in AML, induces p53R2 mRNA and protein expression and therefore asked herein whether the combination will be synergistic in a human AML cell line, HEL. To understand the role of p53R2 in this interaction, we knocked it down (KD) with shRNAmir. HEL and HEL-p53R2KD cells were exposed to CLO and DEC for 24,48,72, and 96-hr. Cells were stained with trypan blue for cell viability. The Hill model was fit to each concentration-response curve for each drug. After fitting and determination of 50% inhibition concentration (IC50), five combination ratios of the IC50 (CLO:DEC; 1:1, 1:4, 4:1, 1.5:3.5; 3.5:1.5) were characterized. In addition, western blot analysis was performed for both cell lines to determine levels of P53R2 expression for the same concentration range and exposure time to each drug, and in combination. Bands in western blot were quantitated using densitometry. HSC70 was used as a house keeping gene. At 24 hr, the IC50 values for CLO and DEC in HEL cells were 500 nM. In p53R2KD cells, the IC50 values for CLO and DEC were 700 nM and 120 nM. As exposure time increased to 48, 72, or 96 hr, the potency increased 10-15-fold for clofarabine, while only 2-4-fold for decitabine. At 48 hr, IC50 values were less than 50 nM for clofarabine in both HEL and p53R2KD cells, while it was 145 and 215 nM for decitabine. For the combination treatment, a pharmacodynamic (PD) interaction model was developed to assess the degree of synergy between CLO and DEC on cell viability. A PD parameter, labeled as ψ, characterized the extent of the interaction. When ψ >=1, the interaction between the two drugs may be additive, while ψ<1 represents synergy and ψ>1 indicates antagonism. Following 24 hr of drug exposure of CLO and DEC at the 50% of the IC50 values for each drug combination, ψ was estimated to be 1.00 (CI 0.850-1.22) for P53R2KD and >1 for HEL cells. In addition, western blot analyses performed at 24-hr following combined drug exposure revealed that the upper band did not change as a function of drug concentration, while the lower band showed a concentration-dependent increase in p53R2 protein expression, especially in p53R2KD.

The PD model demonstrated a synergistic effect for CLO and DEC in the AML cell line HEL; knocking down p53R2 decreased this synergism, attesting to p53R2's role in both drugs’ mechanism of action. The increase in the lower band supports its role as part of clofarabine resistance. A clinical trial combining CLO and DEC in AML is warranted.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5380. doi:10.1158/1538-7445.AM2011-5380

Dynamic pressures on the diabetic foot

A retrospective study was conducted in order to investigate the relation between increased plantar pressure and ulcers in the diabetic foot and contribute more information on this subject. Maximal plantar pressure (MPP) is reported on various areas of the plantar aspects of the feet in 328 diabetic patients and 75 healthy subjects. An increase in MPP under all plantar areas except for the heels was found to be related with increasing severity of the diabetes symptoms. There was also a significant decrease in the application of high pressures to the heels, the metatarsal heads II-IV and the toes.

Long-term antibiotic treatment in geriatric diabetic foot infection

A case report involving a 77-year old diabetic patient with an arterial foot ulcer and subsequent osteomyelitic infection is presented. Due to the patient's ineligibility for surgical intervention, long term antibiotic treatment based upon multiple culture, bone biopsy, radiograms and isotope scanning was initiated. Complete resolution of the osteomyelitis defined by subjective as well as objective criteria was achieved after three months of antibiotic treatment. The common and atypical characteristics of the geriatric population coupled with treatment plan involving a multidisciplinary approach resulted in maintaining foot function and pain-free ambulation in this 77-year old patient.

Patterns of weight distribution under the metatarsal heads

The longitudinal arch between the heel and the forefoot and the transverse arch between the first and fifth metatarsal heads, absorb shock, energy and force. A device to measure plantar pressure was used in 66 normal healthy subjects and in 294 patients with various types of foot disorder. Only 22 (3%) of a total of 720 feet, had a dynamic metatarsal arch during the stance phase of walking, and all had known abnormality. Our findings show that there is no distal transverse metatarsal arch during the stance phase. This is important for the classification and description of disorders of the foot.

[3H]ICS 205-930 labels 5-HT3 recognition sites in membranes of cat and rabbit vagus nerve and superior cervical ganglion

The binding characteristics of [3H]ICS 205-930, a 5-hydroxytryptamine 5-HT3 receptor antagonist, were investigated in membranes prepared from cat and rabbit vagus nerve (VN) and superior cervical ganglion (SCG). The autoradiographic localisation of 5-HT3 recognition sites was also assessed using [3H]ICS 205-930 in slices from cat medulla oblongata, nodose ganglion and vagus nerve. [3H]ICS 205-930 bound to a homogeneous population of high affinity recognition sites in cat VN: Bmax = 201 +/- 43 fmol/mg protein, pKD = 9.26 +/- 0.17 and SCG: Bmax = 291 +/- 40 fmol/mg, pKD = 9.35 +/- 0.80 (n = 3). Competition experiments performed in membranes from cat VN and SCG with agonists and antagonists suggested the presence of a homogeneous population of [3H]ICS 205-930 recognition sites. Competition curves were steep and monophasic and were best fitted by a 1 receptor site model. The following rank order of affinity for [3H]ICS 205-930 binding sites was observed with antagonists: SDZ 206-830 = ICS 205-930 greater than BRL 43694 greater than SDZ 206-792 greater than quipazine greater than MDL 72222 greater than metoclopramide greater than mCPP and agonists: 2-methyl-5-HT = 5-HT greater than phenylbiguanide. A similar profile was observed for a limited series of compounds in rabbit membranes. Drugs acting at 5-HT1, 5-HT2 and dopamine receptors (domperidone, spiperone and metergoline) showed very low affinities for [3H]ICS 205-930 recognition sites. The sites labelled with [3H]ICS 205-930 in vagus nerve and superior cervical ganglion of both species displayed the pharmacological profile of a 5-HT3 receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Competitive interaction of agonists and antagonists with 5-HT3 recognition sites in membranes of neuroblastoma cells labelled with [3H]ICS 205-930

[3H]ICS 205-930 labelled 5-HT3 recognition sites in membranes prepared from murine neuroblastoma N1E-115 cells. Binding was rapid, reversible, saturable and stereoselective to an apparently homogeneous population of sites. Kinetic studies revealed that agonists and antagonists produced a monophasic dissociation reaction of [3H]ICS 205-930 from its recognition sites. The dissociation rate constant of the radioligand was similar whether the dissociation was induced by an agonist or an antagonist. Competition studies carried out with agonists and antagonists also suggested the presence of a homogeneous population of [3H]ICS 205-930 recognition sites. Competition curves were best fit for a 1 site model. [3H]ICS 205-930 binding sites displayed the pharmacological profile of a 5-HT3 receptor. The interactions of agonists and antagonists with [3H]ICS 205-930 recognition sites were apparently competitive in nature, as demonstrated in kinetic and equilibrium experiments. In saturation experiments carried out with [3H]ICS 205-930 in the presence and the absence of unlabelled agonists and antagonists, apparent Bmax values were not reduced whereas apparent Kd values were increased in the presence of competing ligands. There was a good agreement between apparent pKB values calculated for the competing ligands in saturation experiments and pKd values calculated from competition experiments. The present data demonstrate that [3H]ICS 205-930 labels a homogeneous population of sites at which agonists and antagonists interact competitively.

[125I]SCH 23982, a 'selective' D-1 receptor antagonist, labels with high affinity 5-HT1C sites in pig choroid plexus

[125I]SCH 23982, a ligand reported to be very selective for dopamine D-1 receptors, binds with high affinity to membranes of pig choroid plexus (KD = 186 pM, Bmax = 142 fmol/mg protein). Saturation and competition experiments suggested that [125I]SCH 23982 labels a homogeneous population of sites. The rank order for affinity of agonists, 5-HT greater than or equal to DOI (1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane) much greater than dopamine greater than fenoldopam, and antagonists, metergoline greater than mesulergine = mianserin greater than SCH 23390 greater than methiothepin greater than ketanserin greater than fluphenazine much greater than (-)-sulpiride greater than (+)-sulpiride, was compatible with labelling of 5-HT1C receptors by [125I]SCH 23982. It also correlates very significantly with [3H]mesulergine binding to pig choroid plexus membranes. The effects of SCH 23390 and its analogues should not be systematically attributed to an interaction with D-1 receptors.

Characterisation of 5-HT3 recognition sites in membranes of NG 108-15 neuroblastoma-glioma cells with [3H]ICS 205-930

1. The binding characteristics of [3H]ICS 205-930, a potent and selective 5-hydroxytryptamine 5-HT3 receptor antagonist, were investigated in membranes prepared from murine neuroblastoma-glioma NG 108-15 cells. 2. [3H]ICS 205-930 bound rapidly, reversibly and stereoselectively to a homogeneous population of high affinity recognition sites: Bmax = 58 +/- 3 fmol/mg protein, pKD = 9.01 +/- 0.08 (n = 11). Non linear regression and Scatchard analysis of saturation data suggested the existence of a single class of [3H]ICS 205-930 recognition sites on NG 108-15 cells. The binding was rapid, stable and reversible. The affinity of [3H]ICS 205-930 determined in kinetic studies was in agreement with that obtained under equilibrium conditions. 3. Competition studies performed with a variety of agonists and antagonists also suggested the presence of a homogeneous population of [3H]ICS 205-930 recognition sites. All competition curves were steep and monophasic and were best fit by a 1 receptor site model. [3H]ICS 205-930 binding sites displayed the pharmacological profile of a 5-HT3 receptor. Potent 5-HT3 receptor antagonists showed nanomolar affinities for [3H]ICS 205-930 binding sites with the following rank order of potency: SDZ 206-830 greater than ICS 205-930 greater than SDZ 206-792 greater than BRL 43694 greater than quipazine greater than BRL 24924 greater than SDZ 210-204 greater than MDL 72222 greater than SDZ 210-205. Metoclopramide, mCP and mianserin showed submicromolar affinity.(ABSTRACT TRUNCATED AT 250 WORDS)