Browsing by Subject "cancer"
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Item A novel method for finding small highly discriminant gene sets(Texas A&M University, 2004-11-15) Gardner, Jason H.In a normal microarray classification problem there will be many genes, on the order of thousands, and few samples, on the order of tens. This necessitates a massive feature space reduction before classification can take place. While much time and effort has gone into evaluating and comparing the performance of different classifiers, less thought has been spent on the problem of efficient feature space reduction. There are in the microarray classification literature several widely used heuristic feature reduction algorithms that will indeed find small feature subsets to classify over. These methods work in a broad sense but we find that they often require too much computation, find overly large gene sets or are not properly generalizable. Therefore, we believe that a systematic study of feature reduction, as it is related to microarray classification, is in order. In this thesis we review current feature space reduction algorithms and propose a new, mixed model algorithm. This mixed-modified algorithm uses the best aspects of the filter algorithms and the best aspects of the wrapper algorithms to find very small yet highly discriminant gene sets. We also discuss methods to evaluate alternate, ambiguous gene sets. Applying our new mixed model algorithm to several published datasets we find that our new algorithm outperforms current gene finding methods.Item Biological and functional consequences of polymorphisms in the XPD gene(2006-10-23) Kevin James Wolfe; Sherif Z.Abdel-Rahman, Ph.D.; Thomas E. Albrecht, Ph.D.; Rodney S. Nairn, Ph.D.; Randa A. El-Zein, MD. Ph.D.; Mary Treinen-Moslen, Ph.D.; Jonathan B. Ward, Ph.D.Epidemiological studies have documented many associations between single nucleotide polymorphisms (SNPs) in the nucleotide excision repair gene XPD (ERCC2) and cancer risk. Little is known, however, about the underlying mechanisms for these associations. I used lymphocytes from healthy subjects to explore novel mechanisms which could explain the reported risk-modifying effects on disease susceptibility of three SNPs in the XPD gene, the synonymous C156A SNP in exon 6 and the nonsynonymous SNPs Asp312Asn in exon 10 and Lys751Gln in exon 23. Baseline and NNK-induced chromosomal aberrations (Ca) were assessed by cytogenetic analysis and then P values were calculated as estimates of sub-population differences for increased frequencies of CAs associated with the three XPD polymorphisms. I found significant elevation in baseline frequencies of CAs among smokers with the variant 312Asn polymorphism (P=0.028). Elevations in NNK-induced aberrations were found among younger subjects (age<39 years) with the 156A or the 751Gln polymorphism, (P=0.025 and P=0.037, respectively) and in females compared to males with a combination of the 312Asn and the 751Gln polymorphisms (P=0.045). Application of real time PCR showed that each SNP, alone and in combination, significantly decreased constitutive XPD mRNA levels (P<0.003) in lymphocytes. Decreases in XPD mRNA levels were significantly higher in older subjects and in smokers. Localized Mfold structure analysis of the mRNA sequence surrounding the studied SNPs were predicted to alter mRNA secondary structure, which indicated that these SNPs potentially affect local folding and mRNA stability. UVC treatment of cells with wild type XPD produced a significant increase (P=0.03) in XPD protein levels by 30 min, which surprisingly coincided with a decrease in XPD mRNA transcript copy number (P=0.0002). Fluorescent confocal microscopy demonstrated that this increase in XPD protein appeared largely due to an increase in nuclear localization of XPD, which was evident at 30 min and persistent at 6 hrs. New observations from this project provide possible mechanistic explanations for the association of polymorphisms in XPD with increased genetic damage (CAs) and cancer risk.Item DNA Damage Causes p27^(Kip1) Accumulation Through COP1 Signaling(2014-05-06) Choi, Hyun Hop27 is a critical CDK inhibitor involved in cell cycle regulation, but its response to DNA damage remains unclear. Constitutive photomorphogenesis 1 (COP1), a p53- targeting E3 ubiquitin ligase, is downregulated by DNA damage, but the biological consequences of this phenomenon are poorly understood. Here, we report that p27 levels were elevated after DNA damage, with concurrent reduction of COP1 levels. Mechanistic studies showed that COP1 directly interacted with p27 through a VP motif on p27 and functions as an E3 ligase of p27 to accelerate the ubiquitin-mediated degradation of p27. Also, COP1 overexpression lead to cytoplasmic distribution of p27, thereby accelerating p27 degradation. COP1 overexpression resulted in elevation of Aurora A kinase. COP1 and Aurora A levels were positively correlated in patient samples and associated with poor overall survival. We found that COP1 expression promoted cell proliferation, cell transformation, and tumor progression, manifesting its role in cancer promotion whereas p27 negatively regulated COP1 function and prevented tumor growth in a mouse xenograft model of human cancer. Together, these findings define a mechanism for posttranslational regulation of p27 after DNA damage that can explain the correlation between COP1 overexpression and p27 downregulation during tumorigenesis.Item Engineering functionalized gold nanoparticles as a molecular-specific contrast agent to enhance optoacoustic detection of breast cancer cells(2008-12-02) Mohammad Eghtedari; Massoud Motamedi; Vicente Resto; Nicholas A Kotov; Malcolm Brodwick; Gracie VargasMolecular targeting of malignant tumors is a promising field of research that could potentially revolutionize the diagnosis and treatment of many types of cancer including breast. Delivering molecular specific contrast agents to breast cancer cells would enhance the sensitivity and specificity of imaging methods to detect cancer foci at earlier stages, when complete cure is possible. Optoacoustic tomography (OAT) is a non-invasive imaging modality that can be used to produce an image of the distribution of light absorbing components deep within a turbid medium such as human breast. OAT could potentially be used to image breast tumors based on their enhanced angiogenesis; however, its sensitivity and specificity would be limited due to the lack of abnormal angiogenesis at the early stages of tumor growth.\r\nGold nanoparticles generate strong acoustic signal upon pulse laser irradiation and thus are detectable at low concentrations using optoacoustic technique. The goal of this dissertation is to engineer functionalized gold nanoparticles and employ them as a contrast agent for optoacoustic detection of cancer cells.\r\nTo achieve this goal: 1) gold nanoparticles were fabricated in different shape and sizes and their physicochemical properties were optimized for both tumor targeting and optoacoustic detection; 2) the biological properties of fabricated gold nanoparticles were evaluated in vitro and in vivo by determining their stability, toxicity, biodistribution, and molecular targeting properties; 3) the performance of gold nanoparticles to target cancer cells and function as a contrast agent for OAT were assessed in vitro using breast phantoms and then in vivo using animal models.\r\nItem Evaluation of anticancer potential of sorghums with different genetic characteristics and levels of phenolic compounds(2009-05-15) Guajardo Flores, SaraTo evaluate the anticancer potential of sorghum phenolic compounds, different experiments including in vitro and in vivo tests were performed. A set of 25 sorghum samples was evaluated for phenolic (total phenols, flavonoids, anthocyanins and tannins) content, hydrophilic and lipophilic antioxidant capacity using de Oxygen Radical Absorbance Capacity assay (ORAC), and screened for citotoxic properties in mammary, colon and hepatic mammalian cancer cell lines in vitro. Results indicated that there was a wide variability in the phytochemical profile among the different sorghums. Among the 25 samples, sumac sorghum bran had the highest amount of phenolic compounds, flavonoids, tannins and the highest ORAC values. It exerted the highest percent inhibition (near 100%) in mammary, colon and liver cancer cell lines. Sumac sorghum bran was selected for further investigation. Methanolic extracts from sumac whole grain, bran and tannin removed bran were tested in vitro at different concentrations in hormone dependent MCF-7 mammary cancer cells and non hormone dependent Caco2 and HepG2 colon and liver cancer cells. Results indicated that the methanolic extract from sumac bran inhibited 100% of MCF-7 cancer cells at a concentration of 0.5 mg/ml and that the citotoxic effect could be partially due to the tannin content of the extract. Concentrations of 0.5 and 1.5 mg/ml were selected for an in vivo preventive cancer study with 7,12-dymethylbenz(a)-anthracene (DMBA) induced female rats. Bran at low and high concentrations and the correspondent amount of methanol extracts were included in the diet. It was observed that sumac methanol extract at low concentration promoted tumor appearance and development, whereas sumac bran had a preventive effect, however, there were no significant differences in rats treated and un-treated with sumac. Differences between in vitro and in vivo results could be due to the degree of absorption of tannins during the in vivo experiment. To obtain additional data about the effect of sumac extracts on cancer development, a quinone reductase enzyme bioassay was performed. Methanol and hexane extracts from sumac bran induced phase II enzymes in vitro. Phytochemicals of sumac bran sorghum including phenolic compounds and lipid like compounds appeared to have potential for cancer prevention.Item I'm Too Young for This: Adolescent and Young Adult Cancer Survivorship(2014-07-25) Vollmer Dahlke, DeborahAs of January 1, 2012, an estimated 13.7 million cancer survivors were alive in the United States. The number of cancer survivors is expected to reach 18 million by the year 2022. Adolescent and Young Adult (AYA) cancer survivors, ages 15-39, are a population that experiences disparities in care, including a lack of evidence for increased survival. This thesis presents three papers, each using different methods. The first, an analysis of AYA breast cancer survivors? risk factors including access to clinical trials, uses geographic information systems to map patients? distance to trials and logistic regression to analyze demographic and clinical risk factors. The second paper applies quantitative and qualitative analyses in an evaluation of a public and professional education project on AYA survivorship. The third paper uses qualitative methods and a theory-based taxonomy to assess the use of behavior change theories in mobile health (mHealth) applications for cancer survivorship. The results demonstrate the multifactorial elements that impact AYA cancer survivorship, and suggest the need for interventions and expanded research. Additional research is needed to understand the unique physical and biological characteristics of AYAs, in particular those of AYA breast cancer survivors. The thesis illuminates the challenges AYA survivors experience with late effects?physical, psychosocial and financial?and the need for ongoing education for healthcare professionals. In considering the potential of mHealth applications for health behaviors change among AYAs and other cancer survivors, the study articulates concerns about the limited use of theory in the majority of mHealth apps, and suggests the need for intervention designers to reflect more deeply on theoretical models. This thesis contributes to the field of AYA survivorship research in its evidence assessing risk factors including distance to cancer trials for AYA breast cancer patients, by identifying ongoing educational needs for both survivors and providers and by assessing lack of theory and potential for improvement among mHealth interventions. It offers suggestions for future research, policies, and program changes, including the use of emerging mobile technology and sensors to engage AYA survivors both as participants and designers of research that could improve their quality of life and wellbeing.Item Improving Targeted Radionuclide Therapy Using Nuclear Nanotechnology(2013-05-03) Evans, Jordan AndrewThe objectives of this thesis are to produce radioactive antibody-conjugated gold nanoparticles to improve the efficacy of targeted radionuclide therapy for the treatment of cancer, and to demonstrate that this product can be produced at Texas A&M University. We have proposed a method for determining the distribution of radioactive nuclei per nanoparticle, which is critical for determining radiotherapeutic efficacy. Using the distribution of radioactive nuclei per nanoparticle, we have produced methods for calculating the radiative dose to tissue using nano-improved targeted radionuclide therapy, but more importantly we propose procedures to experimentally determine the efficacy of targeted radionuclide therapy improved by application of radioactive nanomaterials in combination with immunotherapy, nanomaterial cytotoxicity, and other cancer therapies such as chemotherapy. These methods can also be used to determine the efficacy of combinatory treatments as a function of time. Characterization of the antibody-nanoparticle attachment is critical; we have demonstrated successful antibody-nanoparticle conjugation using atomic force microscopy, dynamic light scattering, and agarose gel electrophoresis, providing more conclusive evidence of successful conjugation compared to flow cytometry. We provide a mathematical derivation from basic electron-transport principles which demonstrates the theoretical dosimetric advantages of applying radioactive nanomaterials to targeted radionuclide therapy. The general formulae can be applied to any tumor size, any radionuclide, and any pharmacokinetic nanoparticle distribution throughout the body, ultimately allowing a quick method of approximating the necessary activation time and treatment dosage parameters for a specific patient without burdensome Monte Carlo computational simulations. We further demonstrated that nano-TRT dosage to tumors should be considered as a function of radial position rather than average, as the dose across the tumor may be noticeably non-uniform causing some portions of the tumor to receive (potentially) significantly less dose than average.Item Inhibition of invasive breast cancer cell growth by selected peach and plum phenolic antioxidants(Texas A&M University, 2006-04-12) Vizzotto, MarciaFruits and vegetables are known to play an important role in human health due to the range of phytochemicals they contain. Twenty-one peach genotypes and 45 plum genotypes with different flesh and skin color were analyzed for their antioxidant content and antioxidant activity. Anthocyanin content, phenolic content and antioxidant activity were higher in red-flesh than in light-colored flesh peaches. Carotenoid content was higher in yellow-flesh peaches. Among the peaches, the antioxidant activity was well correlated with phenolic content. The anthocyanin content among the plums increased with the red color intensity. Red-flesh plums generally had higher phenolic content than the other plums. Antioxidant activity was higher in red-flesh genotypes; however, it was strongly correlated only with the phenolic content in light-colored flesh plums. Extracts from selected genotypes of peaches and plums and their fractions were evaluated against two breast cancer cell lines (MDA-MB-435 and MCF-7) and one non-cancerous breast line (MCF-10A). The cells were cultured in the presence of peach and plum extracts and their fractions at various concentrations (0-500 ??g/ml) and the cell viability and antiproliferation activity was evaluated by MTT assay and Coulter Counter. There was a dose-dependent reduction on cell viability of estrogen-negative MDA-MB-435 breast cancer cells. Only weak activity against MCF-7 was observed at high extract concentrations. There was no activity against MCF-10A after 24 h treatment. Fraction I, which consists of mainly phenolic acids such as chlorogenic acid and a caffeic acid derivative, reduces MDA-MB-435 breast cancer cell viability with the lowest IC50. The second most effective fraction was Fraction II which contained anthocyanins. Fraction III (flavonols) and Fraction IV (polymerized compounds) had no effect on the cell lines. Phenolic acids present in fraction I induced apoptosis in MDA-MB-435 estrogen receptor-negative cell line. Fraction I did not induced apoptosis in MCF-10A, a noncancerous cell line even at higher concentrations than the ones tested in MDA-MB- 435. Apoptosis induced by Fraction I was caspase 3 and PARP independent. After treatment with 50 ??g of chlorogenic acid equivalent/ml there was an activation of p- ERK.Item ?It?s Not If I Get Cancer, It?s When I Get Cancer?: Exploring Previvors? Management of Uncertainty for Hereditary Cancer in Clinical Encounters(2014-07-10) Dean, Marleah LynnThe purpose of this dissertation study was to identify previvors? sources of uncertainty and strategies for managing uncertainty and understand how previvors? uncertainty influence what type of preventative health decisions they make and how those decisions affect their subsequent sense of uncertainty. A previvor is an individual who is highly predisposed to breast and ovarian cancer due to a genetic mutation called BRCA1/2. Previvors have a 44 to 87 percent risk of developing cancer during their lifetime. Consequently, previvors live in a constant state of uncertainty?wondering not if they might get cancer but when?and must make certain preventative health decisions to reduce their cancer risk. To understand previvors? health experiences, thirty-four, semi-structured interviews were conducted with female previvors. Participants were recruited through Facing Our Risk of Cancer Empowered?s (FORCE) social media pages. Interviews were recorded and transcribed. The constant comparison method was employed to code the interview transcriptions, and the interview transcripts? themes served as the units of analysis. First, analysis revealed two main uncertainty sources for previvors?medical uncertainty and familial uncertainty. Medical uncertainty types include the unknown future, peaks and valleys associated with medical consultations, and personal cancer scares. Familial uncertainty encompasses traumatic family cancer experiences and being a mother and being present in children?s lives. Second, four uncertainty management strategies?seeking clinicians as an informational source, seeking clinicians as a partner for decision-making, seeking clinicians as an emotional support, and seeking referrals from clinicians for emotional support?were identified as ways previvors try to manage their uncertainties. Ultimately, previvors? uncertainty sources and uncertainty management strategies impacted their health decision-making with preventative surgeries as the most common health decision. Overall, the purpose of this research was to gain insight into previvors? uncertain health experiences in order to improve patient-centered communication between previvors and clinicians and ultimately better previvors? health and well-being. This research contributes to the literature by extending the exploration of uncertainty management to a new population, reinforcing the belief that chronic uncertainty should be managed not reduced, supporting health and illness uncertainty theories, and providing practical recommendations for clinician-patient communication.Item Mechanism Based Anticancer Drugs that Degrade Sp Transcription Factors(2013-03-14) Chadalapaka, GayathriCurcumin is the active component of tumeric, and this polyphenolic compound has been extensively investigated as an anticancer drug that modulates multiple pathways and genes. We demonstrated that curcumin inhibited 253JB-V and KU7 bladder cancer cell growth, and this was accompanied by induction of apoptosis and decreased expression of the proapoptotic protein survivin and the angiogenic proteins vascular endothelial growth factor (VEGF) and VEGF receptor 1 (VEGFR1). Since expression of survivin, VEGF and VEGFR1 are dependent on specificity protein (Sp) transcription factors, we also investigated the effects of curcumin on downregulation of Sp protein expression as an underlying mechanism for the apoptotic and antiangiogenic activity of this compound. Curcumin decreases expression of Sp1, Sp3 and Sp4 in blader cancer cells indicating that the cancer chemotherapeutic activity of curcumin is due, in part, to decreased expression of Sp transcription factors and Sp-dependent genes. Betulinic acid (BA) and curcumin are phytochemical anticancer agents, and we hypothesized that both compounds decrease EGFR expression in bladder cancer through downregulation of specificity protein (Sp) transcription factors. BA and curcumin decreased expression of EGFR, Sp1, Sp3, Sp4 and Sp-dependent proteins in 253JB-V and KU7 cells; EGFR was also decreased in cells transfected with a cocktail (iSp) containing small inhibitory RNAs for Sp1, Sp3 and Sp4 showing that EGFR is an Sp-regulated gene. Methyl 2-cyano-3,11-dioxo-18?-olean-1,12- dien-30-oate (CDODA-Me) is a synthetic triterpenoid derived from glycyrrhetinic acid which inhibits proliferation of KU7 and 253JB-V bladder cancer cells. CDODA-Me also decreased expression of specificity protein-1 (Sp1), Sp3 and Sp4 transcription factors. Similar results were observed for a structurally-related triterpenoid, methyl 2-cyano-3,12-dioxooleana-1,9-dien-28-oate (CDDO-Me), which is currently in clinical trials for treatment of leukemia. Celastrol, a naturally occurring triterpenoid acid from an ivy-like vine exhibits anticancer activity against bladder cancer cells. Celastrol decreased cell proliferation, induced apoptosis and decreased expression of specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 and several Sp-dependent genes like Fibroblast growth factor receptor 3 (FGFR3). In vivo studies using KU7 cells as xenografts showed that celastrol represents novel class of anticancer drugs that acts, in part, through targeting downregulation of Sp transcription factors.Item A mechanism of activation of c-MET receptor tyrosine kinase(2006-06-23) Payal Sheth; Lisa A. Elferink; Vincent J. Hilser; Stanley J. Watowich; Rolf Konig; James C. Lee; Bing Suc-MET receptor tyrosine kinase-mediated signaling governs numerous important cellular responses including cellular proliferation, differentiation, migration and apoptosis. Deregulation of these signals result in malignant behaviors, often leading to cancers. While the identity of the many signaling molecules that are activated following hepatocyte-growth factor (HGF)-induced activation of c-MET had been established, little was known about the mechanism of activation of c-MET. From a therapeutic perspective, it is necessary to understand the detailed molecular mechanisms regulating c-MET activation to selectively target these molecules. c-MET, in presence of its cognate ligand, is oligomerized, and is autophosphorylated on specific tyrosines on its cytoplasmic domain. The phosphorylated tyrosines in specific sub-domains of c-MET cytoplasmic region perform specific functions including increase in catalytic activity and recruitment of effector molecules. Classically, it has been believed that the sole role of ligand-induced oligomerization was to autophosphorylate the receptor, thereby switching the receptor’s kinase activity on. However, in light of a recent body of evidence suggesting that certain RTKs are kinase active on cell surface in absence of ligand-induced oligomerization, we hypothesized that oligomerization could be important for other aspects of RTK activation. Using c-MET as our model system, we investigated the role of oligomerization, irrespective of its role in autophosphorylation, in regulating c-MET activation. Previous studies from our laboratory have conclusively shown that oligomerization increases c-MET’s substrate binding affinity and substrate phosphorylation kcat. The work presented here addresses the role of oligomerization in regulating c-MET’s susceptibility to dephosphorylation, another important regulator of c-MET activation. The biochemical parameters measured for c-MET are used to build a unified kinetic model for c-MET activation. The model building and its subsequent validation using cell culture experiments are described here. Furthermore, the model is probed using parameter sensitivity analyses to understand how oligomerization-induced changes in the kinetic, thermodynamic and dephosphorylation properties of c-MET work synergistically to selectively induce specific signaling from the dimeric and not the monomeric receptor. Using these data, we propose an alternative feed-forward model for c-MET activation mechanism differs from the traditional view of the RTK activation.Item Near-infrared narrow-band imaging of gold/silica nanoshells in tumors(2009-05) Puvanakrishnan, Priyaveena; Tunnell, James W.; Rylander, H. GradyGold nanoshells (GNS) are a new class of nanoparticles that can be optically tuned to scatter or absorb light from the near-ultraviolet to near-infrared (NIR) region by varying the core (dielectric silica) /shell (gold) ratio. In addition to spectral tunability, GNS are inert and bioconjugatable making them potential labels for in vivo imaging and therapy of tumors. We report the use of GNS as exogenous contrast agents for enhanced visualization of tumors using narrow band imaging (NBI). NBI takes advantage of the strong NIR absorption of GNS to distinguish between blood and nanoshells in the tumor by imaging in narrow wavelength bands in the visible and NIR, respectively. Using tissue-simulating phantoms, we determined the optimum wavelengths to enhance contrast between blood and GNS. We then used the optimum wavelengths for ex-vivo imaging of tumors extracted from human colon cancer xenograft bearing mice injected with GNS. Systemically delivered GNS accumulated passively in tumor xenografts by enhanced permeability and retention (EPR) effect. Ex-Vivo NBI of tumor xenografts demonstrated tumor specific heterogeneous distribution of GNS with a clear distinction from the tumor vasculature. The results of the present study demonstrate the feasibility of using GNS as contrast agents to visualize tumor tissues using NBI technique.Item New Directions for Cancer Drug Research of Ruthenium and Rhodium Compounds: Investigation of Cytotoxicities, Mechanisms of Cancer Cell Death, and Cellular Targets(2014-07-02) Pena Maceda, BrunoThe discovery of the antitumor properties of cisplatin revolutionized the field of medicinal inorganic chemistry and fostered the development of metal-based anticancer drugs, a topic that continues to play a prominent role in chemotherapy. Ruthenium (Ru) compounds are a promising class of anticancer compounds that display improved therapeutic activities, different mechanisms of action, and reduced side-effects as compared to cisplatin. Two ruthenium compounds are being tested in clinical trials for the treatment of cancer malignancies for which platinum drugs are inactive and several other transition metal complexes are in preclinical studies. In an effort to expand the current state-of-the art in cancer metallotherapeutics, two new classes of ruthenium compounds were synthesized and fully characterized. The first class of complexes is based on Ru(II) coordination compounds of general formula [Ru(N^N)_(2)(N^O^(?))][PF_(6)], where N^N is a bidentate polypyridyl ligand (bpy = 2,2?-bipyridine; phen = 1,10-phenanthroline) and N^O^(?) is a bidentate nitrogen/oxygen-donor anionic ligand (dphol = dibenzo[a,c]phenazin-10-olate; hbtz = 2-(benzo[d]thiazol-2-yl)phenolate). These molecules exhibit cytotoxic properties that are comparable or more effective than cisplatin against lung cancer cells and were found to induce cellular death through the intrinsic pathway of apoptosis. The second class of molecules consist of organometallic Ru(II) compounds of formula [Ru(phpy)(N^N_(1))(N^N_(2))][PF_(6)], where phpy is cyclometallated 2-phenylpyridine and N^N are bidentate polypyridyl ligands. The compounds [Ru(phpy)(bpy)(dppn)][PF_(6)] and [Ru(phpy)(pap)(dppn)][PF_(6)] (dppn = benzo[i]dipyrido[3,2-a:2?,3?-c]phenazine; pap = 2-(phenylazo)pyridine) are the most potent members of the series against cervical and ovarian cancer cells and are also active in the multidrug resistant NCI/ADR-RES ovarian cancer cell line. In addition, the compound [Ru(phpy)(biq)_(2)][PF_(6)] (biq = 2,2?-biquinoline) was shown to exhibit an enhancement of its cytotoxicity when irradiated with red light, results that poise Ru(II) cyclometallated compounds as promising candidates for further development in cancer chemotherapy and photochemotherapy. Finally, an unprecedented fluorophore-labeled metal-metal bonded dirhodium compound was synthesized and characterized, and its cellular distribution and subcellular localization were studied in living cancer cells by using confocal fluorescence microscopy. This fluorescent compound traverses the cellular membrane of lung cancer cells and localizes in lysosomes and mitochondria. In contrast to previous reports of dirhodium anticancer compounds, it does not target the cell nucleus, supporting the contention that other cellular targets can be reached by tuning the ligand environment around the dirhodium core, opening new avenues for drug design.Item Role of MMP2, MMP3 and MMP9 in the development of breast cancer brain and lung metastasis in a syngeneic rat model(Texas A&M University, 2005-11-01) Mendes, Odete RodriguesIn order to study the expression of MMP2, MMP 3 and MMP9 in breast cancer brain and lung metastasis, we used a syngeneic rat model of distant metastasis of ENU1564, a carcinogen-induced mammary adenocarcinoma cell line. At six weeks post inoculation we observed development of micro-metastasis in the brain and lung. Immunohistochemistry and Western blotting analyses showed that MMP 2, -3 and -9 protein expression is consistently significantly higher in neoplastic brain tissue compared to normal brain tissue. Lung metastases express abundant MMP2, -3 and -9 in neoplastic cell cytoplasm. In situ zymography revealed gelatinase activity within the brain metastasis. Gel zymography showed an increase in MMP2 and MMP3 activity in brain metastasis. Furthermore, we were able to significantly decrease the development of breast cancer brain and lung metastasis in animals by treatment with PD 166793, a selective synthetic MMP inhibitor. In addition, PD 166793 decreased the in vitro invasive cell behavior of ENU1546. TIMP2 overexpression also decreased the development of breast cancer lung metastasis in our model. Our results suggest that MMP2, -3 and -9 may be involved in the process of metastasis of breast cancer to the brain and lung. Because astrocytes have been associated with breast cancer brain metastasis we evaluated the role of astrocytes and ERK2 pathway in MMP2 up-regulation in BC brain metastasis. A significant decrease in brain metastases development, and orthotopic tumor size and weight were observed in animals inoculated with ENU1564-TIMP2 cells. These were associated with decreased MMP2 activity, as demonstrated by gel zymography. Rat astrocyte-conditioned media increased expression of MMP2 in ENU15645 cells and increased in vitro cell invasion of ENU1564 and ENU1564-TIMP2 cells. Blockage of ERK1/2 phosphorylation by treatment with PD98059 decreased the expression of MMP2 in cancer cells grown in rat astrocyte-conditioned media. We determine that MMP2 plays a role in in vivo development of breast cancer brain metastases. Additionally, we conclude that astrocytes are associated with expression of MMP2 in cancer cells via ERK1/2 signaling pathway.Item Signaling crosstalk in cancers(2008-04-03) Zhenyu Ji; Xiaodong Cheng; Scott R. Gilbertson; Miriam Falzon; Mark B. Evers; Jingwu Xie; Jingson LiuDeregulation of cellular signaling contributes to the malignant phenotype of cancer. In this dissertation, cross-talk among oncogenic signaling pathways was investigated in two common human cancers. \r\n Pancreatic cancer has a well known spectrum of genetic alterations, among which KRAS mutation is the most prominent component with a detection frequency as high as 90%. Hedgehog signaling pathway is involved in developmental process and it’s reactivated in the early stage of carcinogenesis of pancreatic cancer. The coincidence of KRAS mutation and abnormal hedgehog activation indicates that there’s a potential link between them. We found that oncogenic KRAS activated hedgehog signaling in pancreatic cancer cells through RAF/MEK/MAPK subpathway, but not PI3K/AKT subpathway. Inactivation of KRAS/MEK pathway activity by a KRAS specific siRNA or MEK inhibitors inhibits GLI transcriptional activity and GLI1 expression, and promotes GLI1 protein degradation in pancreatic cancer cell lines with activating KRAS mutation. Furthermore, Suppressing Gli activity leads to a selective attenuation of the oncogenic transformation activity of mutant KRAS-expressing pancreatic cancer cells. These results indicate that hedgehog pathway activation play an important role in oncogenic KRAS mediated transformation during the pancreatic cancer formation. \r\n In addition to its role in pancreatic cancer, hedgehog signaling was also activated in acute lymphoblastic leukemia (ALL). We found that hedgehog pathway activity was correlated to glucocorticoid (GC) sensitivity status in ALL cells. GC resistant ALL cells had higher hedgehog activity when compared to their sensitive counterpart. Increasing intracellular cAMP levels by forskolin overcomes GC resistance in ALL cells. Our studies demonstrate that PKA is responsible for the observed synergism with GC while Epac isn’t. We find that endogenous PKA activity is higher in the GC-sensitive clone than in the GC-resistant clones. Inhibiting hedgehog pathways activity by specific inhibitors alone leads to cell cycle arrest and apopotosis in ALL cells. These results suggest that Hh activity is critical for leukemia cell growth and survival and that the level of Hh activity is in part responsible for the synergism between cAMP and GC. \r\n To identify the mechanism contributing to the PKA activity difference, we measured PKA subunits expression levels and found that regulatory subunit RIIâ is preferentially expressed in the GC sensitive clone C7-14 cells compared to the GC resistant clone C1-15 cells. Down-regulation of RIIbeta by siRNA transfection leads to enhanced GC resistance in CEM cells, which indicates RIIbeta expression is required for GC sensitivity. We also found that activation of PKA II by selective agonists recapitulated forskolin’s effects of promoting apoptosis and antagonizing Akt activity in both GC sensitive and resistant cells. However, PKA I agonists did not have the same effect. These results demonstrate that PKA II is critical for cAMP-promoted apoptosis in ALL cells and its activation or with GC combination could be a novel approach against lymphoid malignancy. \r\n