Networking of differentially expressed genes in human cancer cells resistant to methotrexate

BACKGROUND: The need for an integrated view of data obtained from high-throughput technologies gave rise to network analyses. These are especially useful to rationalize how external perturbations propagate through the expression of genes. To address this issue in the case of drug resistance, we constructed biological association networks of genes differentially expressed in cell lines resistant to methotrexate (MTX). METHODS: Seven cell lines representative of different types of cancer, including colon cancer (HT29 and Caco2), breast cancer (MCF-7 and MDA-MB-468), pancreatic cancer (MIA PaCa-2), erythroblastic leukemia (K562) and osteosarcoma (Saos-2), were used. The differential expression pattern between sensitive and MTX-resistant cells was determined by whole human genome microarrays and analyzed with the GeneSpring GX software package. Genes deregulated in common between the different cancer cell lines served to generate biological association networks using the Pathway Architect software. RESULTS: Dikkopf homolog-1 (DKK1) is a highly interconnected node in the network generated with genes in common between the two colon cancer cell lines, and functional validations of this target using small interfering RNAs (siRNAs) showed a chemosensitization toward MTX. Members of the UDP-glucuronosyltransferase 1A (UGT1A) family formed a network of genes differentially expressed in the two breast cancer cell lines. siRNA treatment against UGT1A also showed an increase in MTX sensitivity. Eukaryotic translation elongation factor 1 alpha 1 (EEF1A1) was overexpressed among the pancreatic cancer, leukemia and osteosarcoma cell lines, and siRNA treatment against EEF1A1 produced a chemosensitization toward MTX. CONCLUSIONS: Biological association networks identified DKK1, UGT1As and EEF1A1 as important gene nodes in MTX-resistance. Treatments using siRNA technology against these three genes showed chemosensitization toward MTX

Generation of an induced pluripotent stem cell line from a healthy Caucasian male

The effects of genetic mutations on protein function can be studied in a physiologically relevant environment using tissue-specific cells differentiated from patient-derived induced pluripotent stem cells (iPSC). However, it is crucial to use iPSC derived from healthy individuals as control. We generated an iPS cell line from skin fibroblasts of a healthy Caucasian male by nucleofection of non-integrating episomal vectors. This cell line has normal karyotype, expresses pluripotency surface markers and pluripotency genes, and successfully differentiates into cells of the 3 germ layers. Therefore, it can be used as control for any disease of interest that is modelled using iPSC

Large Genomic Imbalances in Brugada Syndrome

Purpose Brugada syndrome (BrS) is a form of cardiac arrhythmia which may lead to sudden cardiac death. The recommended genetic testing (direct sequencing of SCN5A) uncovers disease-causing SNVs and/or indels in ~20% of cases. Limited information exists about the frequency of copy number variants (CNVs) in SCN5A in BrS patients, and the role of CNVs in BrS-minor genes is a completely unexplored field. Methods 220 BrS patients with negative genetic results were studied to detect CNVs in SCN5A. 63 cases were also screened for CNVs in BrS-minor genes. Studies were performed by Multiplex ligation-dependent probe amplification or Next-Generation Sequencing (NGS). Results The detection rate for CNVs in SCN5A was 0.45% (1/220). The detected imbalance consisted of a duplication from exon 15 to exon 28, and could potentially explain the BrS phenotype. No CNVs were found in BrS-minor genes. Conclusion CNVs in current BrS-related genes are uncommon among BrS patients. However, as these rearrangements may underlie a portion of cases and they undergo unnoticed by traditional sequencing, an appealing alternative to conventional studies in these patients could be targeted NGS, including in a single experiment the study of SNVs, indels and CNVs in all the known BrS-related genes

Identificació dels nodes genòmics de resposta al tractament quimioterapèutic: Teràpia combinada amb siRNA.

[cat] El treball realitzat en aquesta tesi doctoral constitueix un estudi farmacogenòmic de la resistència al metotrexat (MTX) en cèl·lules de càncer humà, mitjançant experiments amb microarrays per tal de comparar l'expressió gènica diferencial entre cèl·lules sensibles i resistents al MTX. En un primer estudi, vam utilizar com a model la línia cel·lular HT29 de càncer de colon, i vam identificar AKR1C1 com un gen sobreexpressat a les cèl·lules resistents al quimioteràpic. Vam analizar la regulació transcripcional d'aquest gen, mitjançada principalment per Sp1, vam determinar la seva relació amb el cicle cel·lular i amb l'apoptosi i vam establir un paper per AKR1C1 en la resistència al MTX. En un estudi posterior amb microarrays representatius del genoma humà complet, vam identificar un conjunt de gens sobreexpressats i amplificats a les cèl·lules HT29 resistents, amb una localització cromosòmica propera al gen dihidrofolat reductasa. L'anàlisi detallada dels gens diferencialment expressats CAV1, E-Cadherina, PKCi ENO2, ens va permetre determinar per a tots ells un paper en la resistència al MTX, essent els dos primers dianes potencials per al disseny d'una teràpia coadjuvant amb MTX. També vam estudiar la resposta gènica associada a la resistència al MTX en altres línies cel·lulars, representatives de càncer de colon, càncer de mama, càncer de pàncrees, leucèmia eritroblàstica i osteosacoma. Vam realitzar experiments de microarrays per a totes elles i vam obtenir llistes de gens diferencialment expressats. A partir d'aquestes dades, vam construir xarxes d'associació biològica de gens comuns diferencialment expressats en càncer de colon, en càncer de mama o entre les altres tres línies cel·lulars estudiades. Així, vam identificar gens que representaven un node de la xarxa (DKK1), o una xarxa sencera (formada per alguns membres de la família gènica UGT1A) o un gen comú deregulat en càncer de pàncrees, leucèmia eritroblàstica i osteosarcoma (EEF1A1). Validacions funcionals d'aquests gens van mostrar una sensibilització de les cèl·lules vers el MTX.[eng] This thesis represents a pharmacogenomic study on methotrexate (MTX) resistance in human cancer cells. Whole human genome microarrays allowed us to compare the gene expression patterns between cell lines sensitive or resistant to MTX. In a first approach, we used HT29 colon cancer cells as a model, and we identified AKR1C1 as a gene overexpressed in the resistant cells. We analyzed its transcriptional regulation, mainly mediated by Sp1, we determined its relationship with cell cycle and with apoptosis, and established a role for AKR1C1 on MTX resistance. In a second study, we identified a set of genes, located flanking the "dhfr locus", which were overexpressed and amplified in the resistant HT29 cells. Detailed analyses on CAV1, E-Cadherin, PKCand ENO2, four differentially expressed genes, allowed us to establish a role for all of them in MTX resistance, and to hypothesize that CAV1 and E-Cadherin may constitute potential targets for coadjuvant therapy. We also studied the gene expression profiles of MTX resistance in other cell lines, representative of colon cancer, breast cancer, pancreatic cancer, erythroblastic leukemia and osteosarcoma. We performed microarray experiments for all of them and obtained lists of genes differentially expressed. We generated biological association networks with genes in common between both colon cancer cell lines, between both breast cancer cell lines or among the other three cell lines studied. We identified a highly interconnected node in a network (DKK1), a network formed by some members of UGT1A family, and a gene deregulated in pancreatic cancer, erythroblastic leukemia and osteosarcoma (EEF1A1). Functional validations of these three genes showed a sensitization toward MTX

Role of Caveolin 1, E-Cadherin, Enolase 2 and PKCalpha on resistance to methotrexate in human HT29 colon cancer cells

Background: Methotrexate is one of the earliest cytotoxic drugs used in cancer therapy, and despite the isolation of multiple other folate antagonists, methotrexate maintains its significant role as a treatment for different types of cancer and other disorders. The usefulness of treatment with methotrexate is limited by the development of drug resistance, which may be acquired through different ways. To get insights into the mechanisms associated with drug resistance and sensitization we performed a functional analysis of genes deregulated in methotrexate resistant cells, either due to its co-amplification with the dhfr gene or as a result of a transcriptome screening using microarrays. Methods: Gene expression levels were compared between triplicate samples from either HT29 sensitive cells and resistant to 10(-5) M MTX by hybridization to the GeneChip (R) HG U133 PLUS 2.0 from Affymetrix. After normalization, a list of 3-fold differentially expressed genes with a p-value < 0.05 including multiple testing correction (Benjamini and Hochberg false discovery rate) was generated. RT-Real-time PCR was used to validate the expression levels of selected genes and copy-number was determined by qPCR. Functional validations were performed either by siRNAs or by transfection of an expression plasmid. Results: Genes adjacent to the dhfr locus and included in the 5q14 amplicon were overexpressed in HT29 MTX-resistant cells. Treatment with siRNAs against those genes caused a slight reduction in cell viability in both HT29 sensitive and resistant cells. On the other hand, microarray analysis of HT29 and HT29 MTX resistant cells unveiled overexpression of caveolin 1, enolase 2 and PKC alpha genes in resistant cells without concomitant copy number gain. siRNAs against these three genes effectively reduced cell viability and caused a decreased MTX resistance capacity. Moreover, overexpression of E-cadherin, which was found underexpressed in MTX-resistant cells, also sensitized the cells toward the chemotherapeutic agent. Combined treatments targeting siRNA inhibition of caveolin 1 and overexpression of E-cadherin markedly reduced cell viability in both sensitive and MTX-resistant HT29 cells. Conclusion: We provide functional evidences indicating that caveolin 1 and E-cadherin, deregulated in MTX resistant cells, may play a critical role in cell survival and may constitute potential targets for coadjuvant therapy

Generation of biological association networks: A novel strategy to detect new targets in cancer therapy

Podeu consultar el llibre complet a: http://www.trnres.com/ebookcontents.php?id=149The aim of this work was to design a novel strategy to detect new targets for anticancer treatments. The rationale was to build Biological Association Networks from differentially expressed genes in drug-resistant cells to identify important nodes within the Networks. These nodes may represent putative targets to attack in cancer therapy, as a way to destabilize the gene network developed by the resistant cells to escape from the drug pressure. As a model we used cells resistant to methotrexate (MTX), an inhibitor of DHFR. Selected node-genes were analyzed at the transcriptional level and from a genotypic point of view. In colon cancer cells, DHFR, the AKR1 family, PKC¿, S100A4, DKK1, and CAV1 were overexpressed while E-cadherin was lost. In breast cancer cells, the UGT1A family was overexpressed, whereas EEF1A1 was overexpressed in pancreatic cells. Interference RNAs directed against these targets sensitized cells towards MTX

Gene expression profiles in rat mesenteric lymph nodes upon supplementation with Conjugated Linoleic Acid during gestation and suckling

Background Diet plays a role on the development of the immune system, and polyunsaturated fatty acids can modulate the expression of a variety of genes. Human milk contains conjugated linoleic acid (CLA), a fatty acid that seems to contribute to immune development. Indeed, recent studies carried out in our group in suckling animals have shown that the immune function is enhanced after feeding them with an 80:20 isomer mix composed of c9,t11 and t10,c12 CLA. However, little work has been done on the effects of CLA on gene expression, and even less regarding immune system development in early life. Results The expression profile of mesenteric lymph nodes from animals supplemented with CLA during gestation and suckling through dam's milk (Group A) or by oral gavage (Group B), supplemented just during suckling (Group C) and control animals (Group D) was determined with the aid of the specific GeneChip® Rat Genome 230 2.0 (Affymettrix). Bioinformatics analyses were performed using the GeneSpring GX software package v10.0.2 and lead to the identification of 89 genes differentially expressed in all three dietary approaches. Generation of a biological association network evidenced several genes, such as connective tissue growth factor (Ctgf), tissue inhibitor of metalloproteinase 1 (Timp1), galanin (Gal), synaptotagmin 1 (Syt1), growth factor receptor bound protein 2 (Grb2), actin gamma 2 (Actg2) and smooth muscle alpha actin (Acta2), as highly interconnected nodes of the resulting network. Gene underexpression was confirmed by Real-Time RT-PCR. Conclusions Ctgf, Timp1, Gal and Syt1, among others, are genes modulated by CLA supplementation that may have a role on mucosal immune responses in early life

Gene expression profiles in rat mesenteric lymph nodes upon supplementation with Conjugated Linoleic Acid during gestation and suckling

Background Diet plays a role on the development of the immune system, and polyunsaturated fatty acids can modulate the expression of a variety of genes. Human milk contains conjugated linoleic acid (CLA), a fatty acid that seems to contribute to immune development. Indeed, recent studies carried out in our group in suckling animals have shown that the immune function is enhanced after feeding them with an 80:20 isomer mix composed of c9,t11 and t10,c12 CLA. However, little work has been done on the effects of CLA on gene expression, and even less regarding immune system development in early life. Results The expression profile of mesenteric lymph nodes from animals supplemented with CLA during gestation and suckling through dam's milk (Group A) or by oral gavage (Group B), supplemented just during suckling (Group C) and control animals (Group D) was determined with the aid of the specific GeneChip® Rat Genome 230 2.0 (Affymettrix). Bioinformatics analyses were performed using the GeneSpring GX software package v10.0.2 and lead to the identification of 89 genes differentially expressed in all three dietary approaches. Generation of a biological association network evidenced several genes, such as connective tissue growth factor (Ctgf), tissue inhibitor of metalloproteinase 1 (Timp1), galanin (Gal), synaptotagmin 1 (Syt1), growth factor receptor bound protein 2 (Grb2), actin gamma 2 (Actg2) and smooth muscle alpha actin (Acta2), as highly interconnected nodes of the resulting network. Gene underexpression was confirmed by Real-Time RT-PCR. Conclusions Ctgf, Timp1, Gal and Syt1, among others, are genes modulated by CLA supplementation that may have a role on mucosal immune responses in early life

Overexpression of S100A4 in human cancer cell lines resistant to methotrexate

Background: Methotrexate is a chemotherapeutic drug that is used in therapy of a wide variety of cancers. The efficiency of treatment with this drug is compromised by the appearance of resistance. Combination treatments of MTX with other drugs that could modulate the expression of genes involved in MTX resistance would be an adequate strategy to prevent the development of this resistance. Methods: The differential expression pattern between sensitive and MTX-resistant cells was determined by whole human genome microarrays and analyzed with the GeneSpring GX software package. A global comparison of all the studied cell lines was performed in order to find out differentially expressed genes in the majority of the MTX-resistant cells. S100A4 mRNA and protein levels were determined by RT-Real-Time PCR and Western blot, respectively. Functional validations of S100A4 were performed either by transfection of an expression vector for S100A4 or a siRNA against S100A4. Transfection of an expression vector encoding for beta-catenin was used to inquire for the possible transcriptional regulation of S100A4 through the Wnt pathway. Results S100A4 is overexpressed in five out of the seven MTX-resistant cell lines studied. Ectopic overexpression of this gene in HT29 sensitive cells augmented both the intracellular and extracellular S100A4 protein levels and caused desensitization toward MTX. siRNA against S100A4 decreased the levels of this protein and caused a chemosensitization in combined treatments with MTX. beta-catenin overexpression experiments support a possible involvement of the Wnt signaling pathway in S100A4 transcriptional regulation in HT29 cells. Conclusions: S100A4 is overexpressed in many MTX-resistant cells. S100A4 overexpression decreases the sensitivity of HT29 colon cancer human cells to MTX, whereas its knockdown causes chemosensitization toward MTX. Both approaches highlight a role for S100A4 in MTX resistance