Showing papers by "Aamir Ahmad published in 2015"

Functional role of miR-10b in tamoxifen resistance of ER-positive breast cancer cells through down-regulation of HDAC4

Abstract: For breast cancer patients diagnosed with estrogen receptor (ER)-positive tumors, treatment with tamoxifen is the gold standard. A significant number of patients, however, develop resistance to tamoxifen, and management of such tamoxifen-resistant patients is a major clinical challenge. With an eye to identify novel targets for the treatment of tamoxifen-resistant tumors, we observed that tamoxifen-resistant cells derived from ER-positive MCF-7 cells (MCF7TR) exhibit an increased expression of microRNA-10b (miR-10b). A role of miR-10b in drug-resistance of breast cancer cells has never been investigated, although its is very well known to influence invasion and metastasis. To dileneate a role of miR-10b in tamoxifen-resistance, we over-expressed miR-10b in MCF-7 cells and down-regulated its levels in MCF7TR cells. The mechanistic role of HDAC4 in miR-10b-mediated tamoxifen resistance was studied using HDAC4 cDNA and HDAC4-specific siRNA in appropriate models. Over-expression of miR-10b in ER-positive MCF-7 and T47D cells led to increased resistance to tamoxifen and an attenuation of tamoxifen-mediated inhibition of migration, whereas down-regulation of miR-10b in MCF7TR cells resulted in increased sensitivity to tamoxifen. Luciferase assays identified HDAC4 as a direct target of miR-10b. In MCF7TR cells, we observed down-regulation of HDAC4 by miR-10b. HDAC4-specific siRNA-mediated inactivation of HDAC4 in MCF-7 cells led to acquisition of tamoxifen resistance, and, moreover, reduction of HDAC4 in MCF7TR cells by HDAC4-specific siRNA transfection resulted in further enhancement of tamoxifen-resistance. We propose miR-10b-HDAC4 nexus as one of the molecular mechanism of tamoxifen resistance which can potentially be expolited as a novel targeted therapeutic approach for the clinical management of tamoxifen-resistant breast cancers.

miR-20b is up-regulated in brain metastases from primary breast cancers

Abstract: // Aamir Ahmad 1 , Kevin R. Ginnebaugh 1 , Seema Sethi 1 , Wei Chen 2 , Rouba Ali 2 , Sandeep Mittal 2,3 and Fazlul H. Sarkar 1,2 1 Department of Pathology, Wayne State University School of Medicine and Karmanos Cancer Institute, Detroit, Michigan, USA 2 Department of Oncology, Wayne State University School of Medicine and Karmanos Cancer Institute, Detroit, Michigan, USA 3 Department of Neurosurgery, Wayne State University School of Medicine and Karmanos Cancer Institute, Detroit, Michigan, USA Correspondence to: Fazlul H. Sarkar, email: // Keywords : miR-20b, breast cancer, brain metastasis Received : January 27, 2015 Accepted : March 02, 2015 Published : March 26, 2015 Abstract Brain metastases are frequent in patients with advanced breast cancer and are associated with poor prognosis. However, unique molecular biomarkers have not yet been established. We hypothesized that microRNA-20b (miR-20b) plays a role in breast cancer brain metastasis. Our study cohort comprised of eleven breast cancer patients with brain metastasis and nine control patients (age, stage, and follow-up matched) with b reast cancer without brain metastasis. Cases were reviewed microscopically to select tumor blocks with >50% tumor cells, RNA was extracted from formalin-fixed paraffin-embedded (FFPE) tumor tissue blocks and expression of miR-20b analyzed using qRT-PCR. We further tested the effect of miR-20b overexpression on colony formation and invasion in vitro using MCF-7 and MDA-MB-231 cells. In the patient-derived samples, miR-20b expression was significantly higher in brain metastases of breast cancer patients, compared to primary breast tumors as well as the patients without brain metastasis. miR-20b also significantly induced the colony formation and invasiveness of breast cancer cells. Further, miR-20b levels were observed to be high in brain-metastasizing cells, compared to bone-metastasizing cells. Together, our findings suggest a novel role of miR-20b in breast cancer brain metastasis that warrants further investigation for its potential to be developed as prognostic and/or therapeutic target.

Mobilization of Copper ions by Flavonoids in Human Peripheral Lymphocytes Leads to Oxidative DNA Breakage: A Structure Activity Study.

Abstract: Epidemiological studies have linked dietary consumption of plant polyphenols with lower incidence of various cancers. In particular, flavonoids (present in onion, tomato and other plant sources) induce apoptosis and cytotoxicity in cancer cells. These can therefore be used as lead compounds for the synthesis of novel anticancer drugs with greater bioavailability. In the present study, we examined the chemical basis of cytotoxicity of flavonoids by studying the structure-activity relationship of myricetin (MN), fisetin (FN), quercetin (QN), kaempferol (KL) and galangin (GN). Using single cell alkaline gel electrophoresis (comet assay), we established the relative efficiency of cellular DNA breakage as MN > FN > QN > KL > GN. Also, we determined that the cellular DNA breakage was the result of mobilization of chromatin-bound copper ions and the generation of reactive oxygen species. The relative DNA binding affinity order was further confirmed using molecular docking and thermodynamic studies through the interaction of flavonoids with calf thymus DNA. Our results suggest that novel anti-cancer molecules should have ortho-dihydroxy groups in B-ring and hydroxyl groups at positions 3 and 5 in the A-ring system. Additional hydroxyl groups at other positions further enhance the cellular cytotoxicity of the flavonoids.

ASPP and iASPP: Implication in cancer development and progression.

Abstract: The well-known guardian of genome, p53 plays critical roles in the induction of apoptosis typically upon DNA damage whereas mutant p53 containing cells are unable to undergo apoptosis which leads to aggressive tumor growth and drug resistance. Moreover, another molecule regulating wild-ype p53 function is ASPP (apoptosis stimulating proteins of p53) family. ASPP family consists of ASPP1 and ASPP2, and functions as tumor suppressors whereas the inhibitor of ASPP (iASPP) functions as oncogene. By binding to apoptosis regulating proteins such as p53, p63, p73, Bcl-2, NF-κB p65, etc., ASPP1 and ASPP2 promote apoptosis while overexpression of iASPP inhibits apoptotic cell death typically after DNA damage. In cancer cells, the aberrant expressions of ASPP1, ASPP2 and iASPP have been observed, especially, the high expression of iASPP in cancers is associated with worse disease status, therapy resistance and poor survival of patients with cancers. The molecular interactions between the members of ASPP family and their binding proteins in apoptotic pathway together with other regulators such as miR-124, NF-κB regulated Twist, snail, etc. form a complex signal transduction network to control apoptosis and tumor growth. Therefore, targeting ASPP family could regulate the aberrant communications in the signal transduction network to induce apoptosis and drug sensitivity. Several peptides, miRNAs and natural agents have been used to target ASPP family and show encouraging results in the induction of apoptosis of cancer cells; however, more in vivo animal studies and clinical trials are needed to confirm the true value of targeting ASPP family in the treatment of cancers.

Molecular docking and inhibition of matrix metalloproteinase-2 by novel difluorinatedbenzylidene curcumin analog

Abstract: We recently described the synthesis and characterization of a novel difluorinatedbenzylidene analog of curcumin, commonly referred as CDF, which demonstrated significantly enhanced bioavailability and in vivo anticancer activity. CDF targets many factors similar to curcumin, albeit with more potency, as reported previously. To further highlight this differential behavior of CDF, we chose matrix metalloproteinase protein MMP-2 which is involved in the processes of invasion and metastasis of human tumors. Both curcumin and CDF were characterized for their binding characteristics using in silico docking studies; they were also evaluated via biological assays involving gelatin zymography, miRNA analysis, invasion assays and ELISA. CDF was found to inhibit MMP-2 expression and activity in A549 and H1299 NSCLC cells much more effectively than curcumin, validating molecular modeling results. miR-874, an MMP-2-targeting miRNA, was up-regulated by CDF. Thus, it appears that CDF can inhibit MMP-2 through multiple mechanisms. Our results are suggestive of a more potent inhibition of invasion and metastasis by CDF, compared to curcumin, thus warranting its further evaluation as an effective anticancer agent.

Molecular Targets of Naturopathy in Cancer Research: Bridge to Modern Medicine

Abstract: The relevance of naturopathy (defined as the practice of medicine for the treatment of human diseases with natural agents) in human cancer is beginning to be appreciated, as documented by renewed interest in nutraceutical research, the natural anticancer agents of dietary origin. Because of their pleiotropic effects and the ability to modulate multiple signaling pathways, which is a good attribute of natural agents, nutraceuticals have frequently been demonstrated to re-sensitize drug-resistant cancers. The effectiveness of nutraceuticals can be further enhanced if the tools for the relative assessment of their molecular targets are readily available. Such information can be critical for determining their most effective uses. Here, we discuss the anticancer potential of nutraceuticals and the associated challenges that have interfered with their translational potential as a naturopathic approach for the management of cancers. In the years to come, an efficient screening and assessment of molecular targets will be the key to make rapid progress in the area of drug design and discovery, especially focusing on evidence-based development of naturopathy for the treatment of human malignancies.

Targeting increased copper levels in diethylnitrosamine induced hepatocellular carcinoma cells in rats by epigallocatechin-3-gallate

Abstract: We have earlier elucidated a pathway for the anticancer action of plant polyphenolic compounds against malignant cells involving mobilisation of endogenous copper ions and the consequent prooxidant action. To further confirm our hypothesis in vivo, we induced hepatocellular carcinoma (HCC) in rats by diethylnitrosamine (DEN). We show that in such carcinoma cells, there is a progressive elevation in copper levels at various intervals after DEN administration. Concurrently with increasing copper levels, epigallocatechin-3-gallate (EGCG; a potent anticancer plant polyphenol found in green tea) mediated DNA breakage in malignant cells is also increased. The cell membrane permeable copper chelator neocuproine inhibited the EGCG-mediated cellular DNA degradation, whereas the membrane impermeable chelator bathocuproine was ineffective. Iron and zinc specific chelators desferoxamine mesylate and histidine, respectively, were also ineffective in inhibiting EGCG mediated DNA breakage. Through the use of specific scavengers, the mechanism of DNA breakage was determined to be mediated by reactive oxygen species. In summary, we provide an in vivo evidence of accumulating copper in hepatocellular carcinoma that is targeted by EGCG, leading to its anticancer role in a prooxidant manner. Our findings confirm a novel mechanism of anticancer activity of EGCG in particular and plant derived nutraceuticals in general.

Original Article Molecular docking and inhibition of matrix metalloproteinase-2 by novel difluorinatedbenzylidene curcumin analog

Abstract: We recently described the synthesis and characterization of a novel difluorinatedbenzylidene analog of curcumin, commonly referred as CDF, which demonstrated significantly enhanced bioavailability and in vivo an- ticancer activity. CDF targets many factors similar to curcumin, albeit with more potency, as reported previously. To further highlight this differential behavior of CDF, we chose matrix metalloproteinase protein MMP-2 which is involved in the processes of invasion and metastasis of human tumors. Both curcumin and CDF were characterized for their binding characteristics using in silico docking studies; they were also evaluated via biological assays involv- ing gelatin zymography, miRNA analysis, invasion assays and ELISA. CDF was found to inhibit MMP-2 expression and activity in A549 and H1299 NSCLC cells much more effectively than curcumin, validating molecular modeling results. miR-874, an MMP-2-targeting miRNA, was up-regulated by CDF. Thus, it appears that CDF can inhibit MMP-2 through multiple mechanisms. Our results are suggestive of a more potent inhibition of invasion and metastasis by CDF, compared to curcumin, thus warranting its further evaluation as an effective anticancer agent.

Rosin Surfactant QRMAE Can Be Utilized as an Amorphous Aggregate Inducer: A Case Study of Mammalian Serum Albumin.

Abstract: Quaternary amine of diethylaminoethyl rosin ester (QRMAE), chemically synthesized biocompatible rosin based cationic surfactant, has various biological applications including its use as a food product additive. In this study, we examined the amorphous aggregation behavior of mammalian serum albumins at pH 7.5, i.e., two units above their isoelectric points (pI ~5.5), and the roles played by positive charge and hydrophobicity of exogenously added rosin surfactant QRMAE. The study was carried out on five mammalian serum albumins, using various spectroscopic methods, dye binding assay, circular dichroism and electron microscopy. The thermodynamics of the binding of mammalian serum albumins to cationic rosin modified surfactant were established using isothermal titration calorimetry (ITC). It was observed that a suitable molar ratio of protein to QRMAE surfactant enthusiastically induces amorphous aggregate formation at a pH above two units of pI. Rosin surfactant QRMAE-albumins interactions revealed a unique interplay between the initial electrostatic and the subsequent hydrophobic interactions that play an important role towards the formation of hydrophobic interactions-driven amorphous aggregate. Amorphous aggregation of proteins is associated with varying diseases, from the formation of protein wine haze to the expansion of the eye lenses in cataract, during the expression and purification of recombinant proteins. This study can be used for the design of novel biomolecules or drugs with the ability to neutralize factor(s) responsible for the aggregate formation, in addition to various other industrial applications.

Development of patient-derived xenograft models from a spontaneously immortal low-grade meningioma cell line, KCI-MENG1

Abstract: There is a paucity of effective therapies for recurrent/aggressive meningiomas. Establishment of improved in vitro and in vivo meningioma models will facilitate development and testing of novel therapeutic approaches. A primary meningioma cell line was generated from a patient with an olfactory groove meningioma. The cell line was extensively characterized by performing analysis of growth kinetics, immunocytochemistry, telomerase activity, karyotype, and comparative genomic hybridization. Xenograft models using immunocompromised SCID mice were also developed. Histopathology of the patient tumor was consistent with a WHO grade I typical meningioma composed of meningothelial cells, whorls, and occasional psammoma bodies. The original tumor and the early passage primary cells shared the standard immunohistochemical profile consistent with low-grade, good prognosis meningioma. Low passage KCI-MENG1 cells were composed of two cell types with spindle and round morphologies, showed linear growth curve, had very low telomerase activity, and were composed of two distinct unrelated clones on cytogenetic analysis. In contrast, high passage cells were homogeneously round, rapidly growing, had high telomerase activity, and were composed of a single clone with a near triploid karyotype containing 64–66 chromosomes with numerous aberrations. Following subcutaneous and orthotopic transplantation of low passage cells into SCID mice, firm tumors positive for vimentin and progesterone receptor (PR) formed, while subcutaneous implant of high passage cells yielded vimentin-positive, PR-negative tumors, concordant with a high-grade meningioma. Although derived from a benign meningioma specimen, the newly-established spontaneously immortal KCI-MENG1 meningioma cell line can be utilized to generate xenograft tumor models with either low- or high-grade features, dependent on the cell passage number (likely due to the relative abundance of the round, near-triploid cells). These human meningioma mouse xenograft models will provide biologically relevant platforms from which to investigate differences in low- vs. high-grade meningioma tumor biology and disease progression as well as to develop novel therapies to improve treatment options for poor prognosis or recurrent meningiomas.

Review of pelvic collateral pathways in aorto-iliac occlusive disease: demonstration by CT angiography:

Abstract: The pelvic collateral system is a robust network of communicating vessels that provide the functional reserve to withstand chronic aorto-iliac occlusive disease. For establishment of collateral circulation, the afferent vessel must originate proximal to the occlusion and anastomose with vessel/s distal to the occlusion. These collateral pathways can be classified as viscero-systemic, systemic-systemic, and visceral-visceral. CT angiography (CTA) is often the initial modality for evaluating patients with atherosclerotic vascular disease, because it is non-invasive and has been shown to be comparable to conventional angiography. Most collateral pathways are well demonstrated on CTA, which therefore is a useful tool for preoperative planning and regional interventional procedures.

Role of JNK and NF-κB in mediating the effect of combretastatin A-4 and brimamin on endothelial and carcinoma cells

Abstract: The 4,5-diarylimidazole brimamin is an analog of the natural vascular-disrupting agent combretastatin A-4 (CA-4) with improved water solubility, tolerance by animals and efficacy in multidrug-resistant tumors. Here, we aimed at identifying the major mechanisms underlying the in vitro and in vivo actions of brimamin on endothelial and carcinoma cells, including vascularization. The contribution of specific signaling kinases to the effects of brimamin on cytoskeleton organization and the viability and differentiation of endothelial cells was assessed by MTT and tube formation assays in the presence or absence of specific kinase inhibitors. Changes in DNA affinity and expression of NF-κB in endothelial and carcinoma-derived cells and their solid tumors (xenografts) treated with brimamin were ascertained by electrophoretic mobility shift assays and Western blotting. The anti-vascular effect of brimamin in solid tumors was verified by CD31 immunostaining. We found that brimamin can inhibit tubulin polymerization and cause a reorganization of F-actin in Ea.hy926 endothelial cells. Its inhibitory effect on tube formation was found to depend on functional Rho kinase and JNK. JNK inhibition was found to suppress the induction of endothelial cell apoptosis by brimamin. In CA-4-refractory human BxPC-3 pancreas carcinoma-derived and triple-negative MDA-MB-231 breast carcinoma-derived cells brimamin was found to inhibit growth and to induce apoptosis at low nanomolar concentrations by blocking NF-κB activation in a dose-dependent manner. Brimamin was also found to reduce the in vivo growth rate and vascularization of MDA-MB-231 xenografts in mice. Residual tumor cells of these treated xenografts showed a relatively low expression of the p65 subunit of NF-κB. Our data indicate that cellular JNK and Rho kinase activities are crucial for the cytotoxic and cytoskeleton reorganizing effects of brimamin on endothelial cells. In addition, we found that in resistant carcinoma cells and xenografts brimamin can induce down-regulation of anti-apoptotic NF-κB expression and signaling. Its chemical properties and efficacy against clinically relevant cancer entities make brimamin a promising candidate vascular-disrupting agent.

miRNAs in Cancer Stem Cells

Abstract: microRNAs, or miRNAs, play critical roles in cell differentiation and organogenesis by regulating stem cell self-renewal and differentiation. They are important regulators of cancer stem cell formation, survival, and growth, and their aberrant expression may increase drug resistance and promote invasion and metastasis. miRNAs regulate TGF-β, Wnt, notch, and hedgehog signal transductions, which are critical in stem cell development and differentiation. Targeted miRNA regulation by synthetic oligonucleotides, novel agents, or nutraceuticals that inhibit cancer stem cell development and differentiation, in combination with conventional chemotherapeutics, promises better treatment outcomes.

Cancer Stem Cells in Recurrent and Drug-Resistant Lung Cancers

Abstract: With a 5-year survival rate of less than 20%, lung cancer is a leading cause of cancerrelated deaths worldwide. Considering the treatments currently in place, this statistic is frankly shocking. A possible explanation for the disconnect between sophisticated treatments and the survival rate can be found in the Cancer Stem Cell (CSC) hypothesis. The CSC hypothesis suggests the idea of a subpopulation of tumor cells with the abilities of self-renewal, cancer initiation, and further maintenance of tumors. Lung CSCs have been associated with resistance to radiation and chemotherapeutic treatments. CSCs have also been implicated in recurrent cancers; if the CSCs are not completely killed off after treatment, the cancer tends to reemerge. Extensive investigation of CSCs to determine their responsibility in recurrent and drug-resistant cancers heavily relied on the use of specific markers present in CSCs, including CD133, ALDH, ABCG2, and Nanog. Yet another method that results in increased resistance to treatment is epithelial mesenchymal transition, or EMT. Through this process, epithelial cells lose the epithelial phenotype and gain mesenchymal properties. One of these properties is increased drugresistance, rendering EMT culpable – at least in part – for drug-resistance in cancer cells . Furthermore, since miRNA-based therapies are coming to light, various miRNAs will be discussed in terms of their relationship to chemoresistance as well as CSCs in general. Finally, a discussion of the natural and synthetic anti-cancer compounds curcumin, CDF, and BR-DIM will