FRINK Linked Data Fragments server

Matches in SemOpenAlex for { <https://semopenalex.org/work/W69332521> ?p ?o ?g. }

• W69332521 abstract "Despite new methods and combined strategies, conventional cancer chemotherapy still lacksspecificity and induces drug resistance. Gene therapy can offer the potential to obtain the success inthe clinical treatment of cancer and this can be achieved by replacing mutated tumour suppressorgenes, inhibiting gene transcription, introducing new genes encoding for therapeutic products, orspecifically silencing any given target gene. Concerning gene silencing, attention has recentlyshifted onto the RNA interference (RNAi) phenomenon. Gene silencing mediated by RNAimachinery is based on short RNA molecules, small interfering RNAs (siRNAs) and microRNAs(miRNAs), that are fully o partially homologous to the mRNA of the genes being silenced,respectively. On one hand, synthetic siRNAs appear as an important research tool to understand thefunction of a gene and the prospect of using siRNAs as potent and specific inhibitors of any targetgene provides a new therapeutical approach for many untreatable diseases, particularly cancer. Onthe other hand, the discovery of the gene regulatory pathways mediated by miRNAs, offered to theresearch community new important perspectives for the comprehension of the physiological and,above all, the pathological mechanisms underlying the gene regulation. Indeed, changes in miRNAsexpression have been identified in several types of neoplasia and it has also been proposed that theoverexpression of genes in cancer cells may be due to the disruption of a control network in whichrelevant miRNA are implicated. For these reasons, I focused my research on a possible linkbetween RNAi and the enzyme cyclooxygenase-2 (COX-2) in the field of colorectal cancer (CRC),since it has been established that the transition adenoma-adenocarcinoma and the progression ofCRC depend on aberrant constitutive expression of COX-2 gene. In fact, overexpressed COX-2 isinvolved in the block of apoptosis, the stimulation of tumor-angiogenesis and promotes cellinvasion, tumour growth and metastatization.On the basis of data reported in the literature, the first aim of my research was to develop aninnovative and effective tool, based on the RNAi mechanism, able to silence strongly andspecifically COX-2 expression in human colorectal cancer cell lines. In this study, I firstly showthat an siRNA sequence directed against COX-2 mRNA (siCOX-2), potently downregulated COX-2gene expression in human umbilical vein endothelial cells (HUVEC) and inhibited PMA-inducedangiogenesis in vitro in a specific, non-toxic manner. Moreover, I found that the insertion of aspecific cassette carrying anti-COX-2 shRNA sequence (shCOX-2, the precursor of siCOX-2previously tested) into a viral vector (pSUPER.retro) greatly increased silencing potency in a coloncancer cell line (HT-29) without activating any interferon response. Phenotypically, COX-2deficient HT-29 cells showed a significant impairment of their in vitro malignant behaviour. Thus,results reported here indicate an easy-to-use, powerful and high selective virus-based method toknockdown COX-2 gene in a stable and long-lasting manner, in colon cancer cells. Furthermore,they open up the possibility of an in vivo application of this anti-COX-2 retroviral vector, astherapeutic agent for human cancers overexpressing COX-2.In order to improve the tumour selectivity, pSUPER.retro vector was modified for the shCOX-2expression cassette. The aim was to obtain a strong, specific transcription of shCOX-2 followed byCOX-2 silencing mediated by siCOX-2 only in cancer cells. For this reason, H1 promoter in basicpSUPER.retro vector [pS(H1)] was substituted with the human Cox-2 promoter [pS(COX2)] andwith a promoter containing repeated copies of the TCF binding element (TBE) [pS(TBE)]. Thesepromoters were choosen because they are partculary activated in colon cancer cells. COX-2 waseffectively silenced in HT-29 and HCA-7 colon cancer cells by using enhanced pS(COX2) andpS(TBE) vectors. In particular, an higher siCOX-2 production followed by a stronger inhibition ofCox-2 gene were achieved by using pS(TBE) vector, that represents not only the most effective, butalso the most specific system to downregulate COX-2 in colon cancer cells.Because of the many limits that a retroviral therapy could have in a possible in vivo treatment ofCRC, the next goal was to render the enhanced RNAi-mediate COX-2 silencing more suitable forthis kind of application. Xiang and et al. (2006) demonstrated that it is possible to induce RNAi inmammalian cells after infection with engineered E. Coli strains expressing Inv and HlyA genes,which encode for two bacterial factors needed for successful transfer of shRNA in mammaliancells. This system, called “trans-kingdom” RNAi (tkRNAi) could represent an optimal approach forthe treatment of colorectal cancer, since E. Coli in normally resident in human intestinal flora andcould easily vehicled to the tumor tissue. For this reason, I tested the improved COX-2 silencingmediated by pS(COX2) and pS(TBE) vectors by using tkRNAi system. Results obtained in HT-29and HCA-7 cell lines were in high agreement with data previously collected after the transfection ofpS(COX2) and pS(TBE) vectors in the same cell lines. These findings suggest that tkRNAi systemfor COX-2 silencing, in particular mediated by pS(TBE) vector, could represent a promising toolfor the treatment of colorectal cancer.Flanking the studies addressed to the setting-up of a RNAi-mediated therapeutical strategy, Iproposed to get ahead with the comprehension of new molecular basis of human colorectal cancer.In particular, it is known that components of the miRNA/RNAi pathway may be altered during theprogressive development of colorectal cancer (CRC), and it has been already demonstrated thatsome miRNAs work as tumor suppressors or oncomiRs in colon cancer. Thus, my hypothesis wasthat overexpressed COX-2 protein in colon cancer could be the result of decreased levels of one ormore tumor suppressor miRNAs.In this thesis, I clearly show an inverse correlation between COX-2 expression and the human miR-101(1) levels in colon cancer cell lines, tissues and metastases. I also demonstrate that the in vitromodulating of miR-101(1) expression in colon cancer cell lines leads to significant variations inCOX-2 expression, and this phenomenon is based on a direct interaction between miR-101(1) andCOX-2 mRNA. Moreover, I started to investigate miR-101(1) regulation in the hypoxicenvironment since adaptation to hypoxia is critical for tumor cell growth and survival and it isknown that COX-2 can be induced directly by hypoxia-inducible factor 1 (HIF-1). Surprisingly, Iobserved that COX-2 overexpression induced by hypoxia is always coupled to a significantdecrease of miR-101(1) levels in colon cancer cell lines, suggesting that miR-101(1) regulationcould be involved in the adaption of cancer cells to the hypoxic environment that stronglycharacterize CRC tissues." @default.
• W69332521 created "2016-06-24" @default.
• W69332521 creator A5054581382 @default.
• W69332521 date "2008-04-03" @default.
• W69332521 modified "2023-09-23" @default.
• W69332521 title "RNA Interference and cyclooxygenase-2 (COX-2) regulation in colon cancer cells" @default.
• W69332521 doi "https://doi.org/10.6092/unibo/amsdottorato/680" @default.
• W69332521 hasPublicationYear "2008" @default.
• W69332521 type Work @default.
• W69332521 sameAs 69332521 @default.
• W69332521 citedByCount "0" @default.
• W69332521 crossrefType "dissertation" @default.
• W69332521 hasAuthorship W69332521A5054581382 @default.
• W69332521 hasConcept C104317684 @default.
• W69332521 hasConcept C119056186 @default.
• W69332521 hasConcept C145059251 @default.
• W69332521 hasConcept C150194340 @default.
• W69332521 hasConcept C166703698 @default.
• W69332521 hasConcept C2191507 @default.
• W69332521 hasConcept C22615655 @default.
• W69332521 hasConcept C54355233 @default.
• W69332521 hasConcept C67705224 @default.
• W69332521 hasConcept C70721500 @default.
• W69332521 hasConcept C86803240 @default.
• W69332521 hasConceptScore W69332521C104317684 @default.
• W69332521 hasConceptScore W69332521C119056186 @default.
• W69332521 hasConceptScore W69332521C145059251 @default.
• W69332521 hasConceptScore W69332521C150194340 @default.
• W69332521 hasConceptScore W69332521C166703698 @default.
• W69332521 hasConceptScore W69332521C2191507 @default.
• W69332521 hasConceptScore W69332521C22615655 @default.
• W69332521 hasConceptScore W69332521C54355233 @default.
• W69332521 hasConceptScore W69332521C67705224 @default.
• W69332521 hasConceptScore W69332521C70721500 @default.
• W69332521 hasConceptScore W69332521C86803240 @default.
• W69332521 hasLocation W693325211 @default.
• W69332521 hasOpenAccess W69332521 @default.
• W69332521 hasPrimaryLocation W693325211 @default.
• W69332521 hasRelatedWork W1694951464 @default.
• W69332521 hasRelatedWork W1975308625 @default.
• W69332521 hasRelatedWork W1989328481 @default.
• W69332521 hasRelatedWork W2005490924 @default.
• W69332521 hasRelatedWork W2010202610 @default.
• W69332521 hasRelatedWork W2015146505 @default.
• W69332521 hasRelatedWork W2027873015 @default.
• W69332521 hasRelatedWork W2060799314 @default.
• W69332521 hasRelatedWork W2077576784 @default.
• W69332521 hasRelatedWork W2106603079 @default.
• W69332521 hasRelatedWork W2110033155 @default.
• W69332521 hasRelatedWork W2110166030 @default.
• W69332521 hasRelatedWork W2123375447 @default.
• W69332521 hasRelatedWork W2467177869 @default.
• W69332521 hasRelatedWork W2531546252 @default.
• W69332521 hasRelatedWork W2570461157 @default.
• W69332521 hasRelatedWork W2596052773 @default.
• W69332521 hasRelatedWork W2996527417 @default.
• W69332521 hasRelatedWork W3516480 @default.
• W69332521 hasRelatedWork W569190272 @default.
• W69332521 isParatext "false" @default.
• W69332521 isRetracted "false" @default.
• W69332521 magId "69332521" @default.
• W69332521 workType "dissertation" @default.