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Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize anabundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Supplemental material, sj-docx-1-tam-10.1177_17588359221111703 for Association of proton pump inhibitor use with survival outcomes in cancer patients treated with immune checkpoint inhibitors: a systematic review and meta-analysis by Baoqing Chen, Chen Yang, Mihnea P. Dragomir, Dongmei Chi, Wenyan Chen, David Horst, George A. Calin and Qiaoqiao Li in Therapeutic Advances in Medical Oncology

Supplemental material, sj-docx-1-tam-10.1177_17588359221111703 for Association of proton pump inhibitor use with survival outcomes in cancer patients treated with immune checkpoint inhibitors: a systematic review and meta-analysis by Baoqing Chen, Chen Yang, Mihnea P. Dragomir, Dongmei Chi, Wenyan Chen, David Horst, George A. Calin and Qiaoqiao Li in Therapeutic Advances in Medical Oncology

Noncoding RNAs play regulatory roles in physiopathology, but their involvement in neurodevelopmental diseases is poorly understood. Rett syndrome is a severe, progressive neurodevelopmental disorder linked to loss-of-function mutations of the MeCP2 gene for which no cure is yet available. Analysis of the noncoding RNA profile corresponding to the brain-abundant circular RNA (circRNA) and transcribed-ultraconserved region (T-UCR) populations in a mouse model of the disease reveals widespread dysregulation and enrichment in glutamatergic excitatory signaling and microtubule cytoskeleton pathways of the corresponding host genes. Proteomic analysis of hippocampal samples from affected individuals confirms abnormal levels of several cytoskeleton-related proteins together with key alterations in neurotransmission. Importantly, the glutamate receptor GRIA3 gene displays altered biogenesis in affected individuals and in vitro human cells and is influenced by expression of two ultraconserved RNAs. We also describe post-transcriptional regulation of SIRT2 by circRNAs, which modulates acetylation and total protein levels of GluR-1. As a consequence, both regulatory mechanisms converge on the biogenesis of AMPA receptors, with an effect on neuronal differentiation. In both cases, the noncoding RNAs antagonize MeCP2-directed regulation. Our findings indicate that noncoding transcripts may contribute to key alterations in Rett syndrome and are not only useful tools for revealing dysregulated processes but also molecules of biomarker value., Graphical abstract, circRNAs and T-UCRs identify convergent pathways in mouse and human models of Rett syndrome. GRIA3 biogenesis is altered in affected individuals and human cells influenced by two ultraconserved RNAs. SIRT2 is post-transcriptionally regulated by circRNAs. Noncoding RNAs antagonize MeCP2-directed regulation, highlighting the potential of noncoding RNAs (ncRNAs) as biomarkers in Rett syndrome.

The specialized literature emphasizes the fact that vitamin D has a potentially beneficial effect in the context of the current COVID-19 pandemic. The purpose of this article is to highlight the role of vitamin D, both prophylactic and curative, in the treatment of patients diagnosed with COVID-19. Even though its relevance is still unknown and causes various controversies, there is currently no specific treatment for patients diagnosed with COVID-19. There are various prevention strategies with new vaccination schedules, but additional randomized and clinical trials are still needed to combat this pandemic. In addition to the systemic manifestations of SARS-CoV-2 infection, oral manifestations of this disease have also been described in the literature. The etiology of oral manifestations associated with COVID-19 infection and vitamin D deficiency remains controversial. In the present studies, oral manifestations such as salivary gland infections, aphthae, erythema, gingivitis, ulcers, etc. have been reported. This is a new topic, and the prevalence of manifestations is described in only a few studies, which is inconsistent with the number of COVID-19 cases reported since the beginning of the pandemic. The clinical symptomatology in patients with current COVID-19 infection is polymorphic. Whether the oral manifestation is directly caused by SARS-CoV-2 or a secondary manifestation remains an important topic to analyze and discuss.

One of the essential regulators of arterial blood pressure, the renin-angiotensin-aldosterone system (RAAS) seems to be one of the most complex mechanisms in the human body. Since the discovery of its key components and their actions, new substances and functions are still being unraveled. The main pathway begins with the secretion of renin in the kidney and culminates with the synthesis of angiotensin II (Ang II)—a strong vasoconstrictor—thanks to the angiotensin-converting enzyme (ACE). Research conducted in 2000 identified another enzyme, named ACE2, that converts Ang II into Ang-(1–7), a heptapeptide with opposing effects to those of Ang II: vasodilation and anti-inflammatory properties. This particular enzyme became of paramount importance during the last two decades, as a result of the confrontation of the human race with life-threatening epidemics. Multiple studies have been performed in order to uncover the link between ACE2 and human coronaviruses, the results of which we systemized in order to create an overview of the pathogenic mechanism. Human coronaviruses, such as SARS-CoV and SARS-CoV-2, attach to ACE2 via their spike proteins (S), causing the destruction of the enzyme. Because ACE2 limits the production of Ang II (by converting it into Ang-(1–7)), its destruction leads to a dysregulated inflammatory response. The purpose of this review is to decipher the complex pathophysiological mechanisms underlying the multiorgan complications (oral, cardiac, pulmonary, systemic) that appear as a result of the interaction of the SARS CoV-2 virus with the angiotensin-converting enzyme type 2.

Deep learning models for object detection have gotten larger and larger over the years, spanning from 3.9M trainable parameters for EfficientDet to 209M for the AmoebaNet-based NAS-FPN detector. Different strategies are currently being researched in order to improve the efficiency of deep learning models for object detection, one of which is running the training and inference of the neural network in low precision. Interesting results have been achieved by researchers, starting from the original paradigm of using operators and doing the necessary operations in IEEE single precision (FP32), to achieving similar accuracies of the models using custom minifloat formats (FP8). The results can be pushed even further by using genetic algorithms for hyperparameter tuning, in order to find specific hyperparameter for the FP8 version of the model. In this paper, we will present the results of our experiments utilizing YOLOv3 with hybrid floating-point format (HFP8). One of the experiments in this paper shows how our solution can be used for checking social distancing guidelines which is a very important topic in the current COVID-19 pandemic.

Table S2. Downregulated mRNAs after miR-1287 overexpression in the cell line SUM159. This list shows 126 mRNAs that were at least 1.5-fold downregulated with a p-value of

Immune cells of myeloid origin, including microglia, macrophages, and myeloid-derived suppressor cells adopt immunosuppressive phenotypes that support gliomagenesis. Here, we tested an a priori hypothesis that single nucleotide polymorphisms (SNPs) in genes related to glioma-associated myeloid cell regulation and function are also associated with patient survival after glioma diagnosis. Subjects for this study were 992 glioma patients treated at The University of Texas MD Anderson Cancer Center in Houston, Texas between 1992 and 2008. Haplotype-tagging SNPs in 91 myeloid-associated genes were analyzed for association with survival by Cox regression. Individual SNP- and gene-based tests were performed separately in glioblastoma (WHO grade IV, n = 511) and lower-grade glioma (WHO grade II-III, n = 481) groups. After adjustment for multiple testing, no myeloid-associated gene variants were significantly associated with survival in glioblastoma. Two SNPs, rs147960238 in CD163 (p = 2.2 × 10-5) and rs17138945 in MET (p = 5.6 × 10-5) were significantly associated with survival of patients with lower-grade glioma. However, these associations were not confirmed in an independent analysis of 563 lower-grade glioma cases from the University of California at San Francisco Adult Glioma Study (p = 0.65 and p = 0.41, respectively). The results of this study do not support a role for inherited polymorphisms in myeloid-associated genes in affecting survival of patients diagnosed with glioblastoma or lower-grade glioma.

Supplementary Figures S1â 21. (DOC 61 mb)

Medical sciences: correction for "Small molecule enoxacin is a cancer-specific growth inhibitor that acts by enhancing TAR RNA-binding protein 2-mediated microRNA processing," by SoniaMelo, Alberto Villanueva, Catia Moutinho, Veronica Davalos, Riccardo Spizzo, Cristina Ivan, Simona Rossi, Fernando Setien, Oriol Casanovas, Laia Simo-Riudalbas, Javier Carmona, Jordi Carrere, August Vidal, Alvaro Aytes, Sara Puertas, Santiago Ropero, Raghu Kalluri, Carlo M. Croce, George A. Calin, and Manel Esteller, which appeared in issue 11, March 15, 2011, of Proc Natl Acad Sci USA (108:4394-4399; first published February 28, 2011; 10.1073/pnas.1014720108).

PurposeThe IL11 receptor (IL11R) is an established molecular target in primary tumors of bone, such as osteosarcoma, and in secondary bone metastases from solid tumors, such as prostate cancer. However, its potential role in management of hematopoietic malignancies has not yet been determined. Here, we evaluated the IL11R as a candidate therapeutic target in human leukemia and lymphoma.Experimental design and resultsFirst, we show that the IL11R protein is expressed in a variety of human leukemia- and lymphoma-derived cell lines and in a large panel of bone marrow samples from leukemia and lymphoma patients, whereas expression is absent from nonmalignant control bone marrow. Moreover, a targeted peptidomimetic prototype (termed BMTP-11), specifically bound to leukemia and lymphoma cell membranes, induced ligand-receptor internalization mediated by the IL11R, and resulted in a specific dose-dependent cell death induction in these cells. Finally, a pilot drug lead-optimization program yielded a new myristoylated BMTP-11 analogue with an apparent improved antileukemia cell profile.ConclusionsThese results indicate (i) that the IL11R is a suitable cell surface target for ligand-directed applications in human leukemia and lymphoma and (ii) that BMTP-11 and its derivatives have translational potential against this group of malignant diseases.

Prostate cancer antigen 3 (PCA3) is the most specific prostate cancer biomarker but its function remains unknown. Here we identify PRUNE2, a target protein-coding gene variant, which harbors the PCA3 locus, thereby classifying PCA3 as an antisense intronic long noncoding (lnc)RNA. We show that PCA3 controls PRUNE2 levels via a unique regulatory mechanism involving formation of a PRUNE2/PCA3 double-stranded RNA that undergoes adenosine deaminase acting on RNA (ADAR)-dependent adenosine-to-inosine RNA editing. PRUNE2 expression or silencing in prostate cancer cells decreased and increased cell proliferation, respectively. Moreover, PRUNE2 and PCA3 elicited opposite effects on tumor growth in immunodeficient tumor-bearing mice. Coregulation and RNA editing of PRUNE2 and PCA3 were confirmed in human prostate cancer specimens, supporting the medical relevance of our findings. These results establish PCA3 as a dominant-negative oncogene and PRUNE2 as an unrecognized tumor suppressor gene in human prostate cancer, and their regulatory axis represents a unique molecular target for diagnostic and therapeutic intervention.

Although numerous studies highlighted the role of Epstein-Barr Virus (EBV) in B-cell transformation, the involvement of EBV proteins or genome in the development of the most frequent adult leukemia, chronic lymphocytic leukemia (CLL), has not yet been defined. We hypothesized that EBV microRNAs contribute to progression of CLL and demonstrated the presence of EBV miRNAs in B-cells, in paraffin-embedded bone marrow biopsies and in the plasma of patients with CLL by using three different methods (small RNA-sequencing, quantitative reverse transcription PCR [q-RT-PCR] and miRNAs in situ hybridization [miRNA-ISH]). We found that EBV miRNA BHRF1-1 expression levels were significantly higher in the plasma of patients with CLL compared with healthy individuals (p&nbsp

In cancer therapy the platinum-based drugs are used frequently with a good clinical outcome, but besides unwanted side effects which occur, the tumour cells subjected to treatment are prone to develop tolerance or even multidrug resistance (MDR). Metal compounds with a central atom other than platinum are efficient in targeting the chemoresistant cells, therefore the biological outcome of two recently synthesized gallium phosphinoarylbisthiolato complexes was studied, having the formula [X][Ga{PPh(2-SC6H4)2-κ(3)S,S',P}{PPh(2-SC6H4)2-κ(2)S,S'}] where [X] is either the NEt3H (1) or PPh4 (2) cation. Compounds 1 and 2 display in vitro cytotoxicity against both platinum-sensitive and platinum-resistant cell lines (A2780 and A2780cis). Morphological and ultrastructural evidence points toward their capacity to impair tumour cells survival. This behaviour is based on malignant cells capacity to selectively intake gallium, and to bind to the cellular DNA. They are able to cause massive DNA damage in treated cancer cells, focusing on 7-methylguanine and 8-oxoguanine sites and oxidizing the pyrimidine bases; this leads to early apoptosis of a significant percent of treated cells. The intrinsic and extrinsic apoptotic pathways are influenced through the modulation of gene expression following the treatment with complexes 1 and 2, which accompanies the negative regulation of P-glycoprotein 1 (Pgp-1), an important cellular ABC-type transporter from the multidrug resistance (MDR) family. The studied Ga(III) compounds demonstrated the capacity to counteract the chemoresistance mechanisms in the tumours defiant to standard drug action. Compound 2 shows a good anticancer potential and it could represent an alternative to platinum-based drugs especially in the situation of standard treatment failure.

Figure S1. (A) Measurement of miR-1287-5p in mammospheres compared to control cells by quantitative RT-PCR in four BC cell lines including two triple negative (SUM159 and MDA-MB-231) confirms the results of the microarray analysis. MiR-1287-5p is downregulated in mammospheres compared to adherent growing parental cells; *p

Additional file 1: Table S1. The year of diagnosis of patients from SEER database included in the study (nâ =â 2267).

Figure S1. (A) Measurement of miR-1287-5p in mammospheres compared to control cells by quantitative RT-PCR in four BC cell lines including two triple negative (SUM159 and MDA-MB-231) confirms the results of the microarray analysis. MiR-1287-5p is downregulated in mammospheres compared to adherent growing parental cells; *p

Table S1. Primer sequences used for quantitative RT-PCR analysis. (DOCX 15 kb)

Additional file 2: Table S2. Clinicopathologic characteristics of all MBC patients (nâ =â 2267).

Additional file 1: Table S1. The year of diagnosis of patients from SEER database included in the study (nâ =â 2267).

Additional file 2: Table S2. Clinicopathologic characteristics of all MBC patients (nâ =â 2267).

The involvement of microRNAs in malignant transformation and cancer progression was previously grounded. The observations made by multiple published studies led to the conclusion that some of these small sequences could be eventually used as biomarkers for diagnosis/prognosis. This meta-analysis investigated whether microRNA-181 family members could predict the outcome of patients carrying different types of cancer. We searched the PubMed and Embase databases for studies evaluating the expression levels of miR-181a/b/c/d in patients with cancer, selecting the publications that assessed the relation between low and high levels of one of these four microRNAs and patients’ outcome. Hazard ratios (HRs) or risk ratios (RRs) were extracted from the studies, and random-effect model was performed to investigate the role of miR-181 in the outcome of these patients. The meta-analysis comprised 26 studies including 2653 cancer patients from 6 countries. The results showed significant association between the expression of miR-181 family members and colorectal cancer. Considering the heterogeneity of the pathologies, the analysis, including all types of cancer and the expression of all the miR-181 family members together, showed no association with distinct outcome (HR = 1.099, p = 0.435). When the analysis was performed on each microRNA separately, the expression of miR-181c was significantly associated with the outcome of patients with cancer (HR = 2.356, p = 0.011) and miR-181a expression levels significantly correlated with survival in patients with non-small-cell lung cancer (HR = 0.177, p

The cancer-risk-associated rs6983267 single nucleotide polymorphism (SNP) and the accompanying long noncoding RNA CCAT2 in the highly amplified 8q24.21 region have been implicated in cancer predisposition, although causality has not been established. Here, using allele-specific CCAT2 transgenic mice, we demonstrate that CCAT2 overexpression leads to spontaneous myeloid malignancies. We further identified that CCAT2 is overexpressed in bone marrow and peripheral blood of myelodysplastic/myeloproliferative neoplasms (MDS/MPN) patients. CCAT2 induces global deregulation of gene expression by down-regulating EZH2 in vitro and in vivo in an allele-specific manner. We also identified a novel non-APOBEC, non-ADAR, RNA editing at the SNP locus in MDS/MPN patients and CCAT2-transgenic mice. The RNA transcribed from the SNP locus in malignant hematopoietic cells have different allelic composition from the corresponding genomic DNA, a phenomenon rarely observed in normal cells. Our findings provide fundamental insights into the functional role of rs6983267 SNP and CCAT2 in myeloid malignancies.

Purpose: The oncogenic miR-155 is upregulated in many human cancers, and its expression is increased in more aggressive and therapy-resistant tumors, but the molecular mechanisms underlying miR-155-induced therapy resistance are not fully understood. The main objectives of this study were to determine the role of miR-155 in resistance to chemotherapy and to evaluate anti-miR-155 treatment to chemosensitize tumors. Experimental Design: We performed in vitro studies on cell lines to investigate the role of miR-155 in therapy resistance. To assess the effects of miR-155 inhibition on chemoresistance, we used an in vivo orthotopic lung cancer model of athymic nude mice, which we treated with anti-miR-155 alone or in combination with chemotherapy. To analyze the association of miR-155 expression and the combination of miR-155 and TP53 expression with cancer survival, we studied 956 patients with lung cancer, chronic lymphocytic leukemia, and acute lymphoblastic leukemia. Results: We demonstrate that miR-155 induces resistance to multiple chemotherapeutic agents in vitro, and that downregulation of miR-155 successfully resensitizes tumors to chemotherapy in vivo. We show that anti-miR-155-DOPC can be considered non-toxic in vivo. We further demonstrate that miR-155 and TP53 are linked in a negative feedback mechanism and that a combination of high expression of miR-155 and low expression of TP53 is significantly associated with shorter survival in lung cancer. Conclusions: Our findings support the existence of an miR-155/TP53 feedback loop, which is involved in resistance to chemotherapy and which can be specifically targeted to overcome drug resistance, an important cause of cancer-related death. Clin Cancer Res; 23(11); 2891–904. ©2016 AACR.

Simple Summary DNA regions having high sequence similarity among human, rat and mouse genomes are defined as Ultraconserved Regions. Non-coding RNA transcripts originating by these regions may play relevant roles in the onset and progression of multiple cancer types. We recently found that ultra-conserved-transcript-8+ (uc.8+) levels correlate with the grading and staging of bladder cancer. The aim of this study is to systematically evaluate the expression of ultra-conserved-transcript-8+ (uc.8+) in biopsies and assess its intracellular localization. Furthermore, we aimed to correlate uc.8+ levels with clinical parameters and patient survival. Our analysis indicates that uc.8+ can localize both in the cytoplasm and nucleus of bladder cells at early stages of tumorigenesis, while in tumors at advanced stages, uc.8+ has a prevalent cytoplasmic localization. These data provide relevant information about uc.8+ localization as a hallmark of tumor stage. Finally, using advanced computer-based techniques, we predicted the binding of uc.8+ to RNA-binding proteins. Our study overall suggests that uc.8+ localization can be used as a prognostic biomarker for bladder cancer. Abstract Non-coding RNA transcripts originating from Ultraconserved Regions (UCRs) have tissue-specific expression and play relevant roles in the pathophysiology of multiple cancer types. Among them, we recently identified and characterized the ultra-conserved-transcript-8+ (uc.8+), whose levels correlate with grading and staging of bladder cancer. Here, to validate uc.8+ as a potential biomarker in bladder cancer, we assessed its expression and subcellular localization by using tissue microarray on 73 human bladder cancer specimens. We quantified uc.8+ by in-situ hybridization and correlated its expression levels with clinical characteristics and patient survival. The analysis of subcellular localization indicated the simultaneous presence of uc.8+ in the cytoplasm and nucleus of cells from the Low-Grade group, whereas a prevalent cytoplasmic localization was observed in samples from the High-Grade group, supporting the hypothesis of uc.8+ nuclear-to-cytoplasmic translocation in most malignant tumor forms. Moreover, analysis of uc.8+ expression and subcellular localization in tumor-surrounding stroma revealed a marked down-regulation of uc.8+ levels compared to the paired (adjacent) tumor region. Finally, deep machine-learning approaches identified nucleotide sequences associated with uc.8+ localization in nucleus and/or cytoplasm, allowing to predict possible RNA binding proteins associated with uc.8+, recognizing also sequences involved in mRNA cytoplasm-translocation. Our model suggests uc.8+ subcellular localization as a potential prognostic biomarker for bladder cancer.

SummaryLong noncoding RNAs (lncRNAs) significantly influence the development and regulation of genome expression in cells. Here, we demonstrate the role of lncRNA ceruloplasmin (NRCP) in cancer metabolism and elucidate functional effects leading to increased tumor progression. NRCP was highly upregulated in ovarian tumors, and knockdown of NRCP resulted in significantly increased apoptosis, decreased cell proliferation, and decreased glycolysis compared with control cancer cells. In an orthotopic mouse model of ovarian cancer, siNRCP delivered via a liposomal carrier significantly reduced tumor growth compared with control treatment. We identified NRCP as an intermediate binding partner between STAT1 and RNA polymerase II, leading to increased expression of downstream target genes such as glucose-6-phosphate isomerase. Collectively, we report a previously unrecognized role of the lncRNA NRCP in modulating cancer metabolism. As demonstrated, DOPC nanoparticle-incorporated siRNA-mediated silencing of this lncRNA in vivo provides therapeutic avenue toward modulating lncRNAs in cancer.

We are glad to share with you our third Journal Club and to highlight some of the most interesting papers published recently. [...]

Tese de Doutoramento em Ciências da Saúde, Non-coding RNAs are a class of RNA transcripts that do not codify for protein. Included in this class are the microRNAs, small RNAs with approximately 20 nucleotides in length. microRNAs act post-transcriptionally by binding to 5´- ultraconserved regions, coding regions or 3´-ultraconserved regions of messenger RNAs and inhibit its translation or cause messenger RNA cleavage. Additionally, microRNAs can also bind to pseudogenes and are involved in RNA decoy functions. A single microRNA can bind to several RNAs and a single RNA can be targeted by different microRNAs. Therefore, microRNAs constitute master regulators of gene expression and major key players in the control of cellular functions. microRNAs are deregulated in all tumor types and can act as tumor suppressors or as oncogenes in a tissue- and cell-specific manner. microRNAs control biological mechanisms essential for cancer cells, such as proliferation, cell death, cell cycle, metabolism, hypoxia, angiogenesis, inflammation, migration, invasion, metastasis and cancer stem cells self-renewal. Besides microRNAs´ importance as diagnostic and prognostic tools in cancer, and due to their involvement in cancer biology, microRNAs have been regarded as new therapeutic targets. This thesis focuses on the role of microRNAs on colorectal cancer. Despite the great improvement in therapeutics, colorectal cancer is still one of the most commonly diagnosed tumor types and a frequent cause of cancer-related death. We intend to understand the biological effects of miR-28 in this tumor type. To achieve this goal both in vitro and in vivo approaches were used. In the microRNA biogenesis pathway, usually a primary-microRNA is processed into a precursor-microRNA, which originates a single mature microRNA. However, in some cases, two mature miRNAs are processed. This occurs with the precursor-miR-28 that is processed into two mature microRNAs that were named miR-28-5p and miR-28- 3p. We identified for the first time that both mature forms of miR-28 were deregulated in colorectal cancer. Contrary to some tumor and cell types in which miR-28 was found to be upregulated, in colorectal cancer miR-28 is downregulated in tumor compared with normal colorectal tissue. However, the two mature forms have distinct functions. Our in vitro results revealed that miR-28-5p overexpression decreased proliferation, increased apoptosis, caused a G1-arrest in the cell cycle, and decreased migration and invasion, while miR-28-3p overexpression had no effect on proliferation but increased migration and invasion. This was the first description of miR-28 dual role in colorectal cancer cells. As miR-28 mature forms are transcribed together, we analyzed the overall result in vivo. Xenografts of colorectal cancer cells overexpressing miR-28 caused a slower tumor growth in mice, while increased metastasis, when compared with the control group. In this thesis we also discuss the strategies to inhibit or restore microRNAs function. The dual role of miR-28 has great impact on the design of therapies using microRNAs, in particular for upregulation of microRNA levels using expression vectors. Variation in expression levels of microRNAs has a tremendous impact on the intracellular signaling networks. We determined that miR-28-5p targets Cyclin D1, an important regulator of cell cycle progression, in particular of the G1-S phase transition. Additionally, miR-28-5p directly targets HOXB3, a transcription factor described to be upregulated in colon cancer. On the other hand, miR-28-3p directly regulates the expression of NM23-H1, an anti-metastatic gene. miR-28 is part of an extensive number of microRNAs deregulated in colorectal cancer. It is essential to understand the effect of the microRNAs in cancer to be able to interfere with the tumor biology and consequently generate therapeutic strategies based on microRNAs as an approach to fight cancer., RNAs não codificantes são uma classe de transcritos de RNA que não codificam proteína. Dentro desta classe encontram-se os microRNAs, pequenos RNAs com 20 nucleótidos de comprimento. Os microRNAs actuam após a transcrição e ligam-se por complementariedade de bases a RNAs mensageiros, nas suas regiões 5´- ou 3´-ultraconversadas e nas regiões codificantes. Os microRNAs inibem a tradução ou causam a degradação do RNA mensageiro. Além disso, os microRNAs podem também ligar-se a pseudo-genes e estar envolvidos em funções de RNA “decoy”. Um único microRNA pode ligar-se a vários RNAs, e um único RNA pode ser o alvo de vários microRNAs. Assim sendo, os microRNAs constituem excelentes reguladores da expressão genética e são elementos chave no controlo das funções celulares. Os microRNAs estão desregulados em todos os tipos de tumor e podem actuar como supressores tumorais ou como oncogenes, dependendo do tipo de tecido e de célula. Os microRNAs controlam mecanismos biológicos essenciais para as células neoplásicas, incluindo a proliferação, a morte e o ciclo celular, o metabolismo, a hipoxia, a angiogénese, a inflamação, a migração, a invasão, a metastização e a autorenovação das células estaminais tumorais. Para além da importância dos microRNAs como ferramentas de diagnóstico e prognóstico oncológico, e devido ao seu envolvimento na biologia tumoral, os microRNAs têm sido apresentados como novos alvos terapêuticos. Esta tese analisa o papel dos microRNAs no cancro colorectal. Apesar dos significativos avanços terapêuticos, o cancro colorectal continua a ser um dos tipos tumorais mais diagnosticados e uma frequente causa de morte por cancro. No trabalho aqui apresentado, pretende-se analisar o efeito biológico do miR-28 neste tipo tumoral. Para atingir este objectivo utilizámos ferramentas in vitro e in vivo.Geralmente, na via da biogénese dos microRNAs, um microRNA-primário é processado constituindo o microRNA-precursor que, por sua vez, origina um único microRNA maduro. No entanto, em alguns casos, são originados dois microRNAs maduros. Esta situação ocorre com o precursor do miR-28 que é processado em dois microRNAs maduros designados de miR-28-5p e miR-28-3p. Identificámos, pela primeira vez, ambas as formas do miR-28 maduro como estando desreguladas em cancro colorectal. Contrariamente a outros tipos de tumores/células nas quais o miR- 28 está sobreexpresso, no cancro colorectal o miR-28 está subexpresso no tumor quando comparado com os seus níveis de expressão no tecido colorectal normal. No entanto, as duas formas maduras têm funções distintas. Os estudos in vitro revelaram que a sobreexpressão do miR-28-5p diminui a proliferação, aumenta a apoptose, impede a progressão do ciclo celular na fase G1, e diminui a migração e a invasão; enquanto que a sobreexpressão do miR-28-3p não tem efeito na proliferação mas aumenta a migração e a invasão. Esta é a primeira descrição do duplo papel do miR-28 em neoplasia colorectal. Visto que as formas maduras do miR-28 são transcritas conjuntamente, analisámos o resultado global da expressão do miR-28 in vivo. A injecção, em murganhos, de células neoplásicas colorectais que sobreexpressam miR- 28 causou um crescimento mais lento dos tumores, mas provocou um aumento no número de metastases, quando comparámos com o grupo control. Nesta tese, discutimos as estratégias para inibir ou restaurar a função dos microRNAs. O duplo papel do miR-28 tem um vasto impacto no desenho de terapias que recorram a microRNAs, em particular na sobreexpressão dos níveis de microRNAs usando vectores de expressão. A variação dos níveis de microRNAs tem um impacto tremendo na rede de sinalização intracellular. Observámos que o miR-28-5p tem como alvo a Cyclin D1, um importante regulador da progressão no ciclo celular, em particular na transição G1-S. Além disso, o miR-28-5p tem como alvo directo o HOXB3, um factor de transcrição descrito como estando sobreexpresso no cancro do colon. Por outro lado, o miR-28-3p regula directamente a expressão de NM23-H1, um gene anti-metastático. O miR-28 faz parte de um extenso número de microRNAs que está desregulado em neoplasias. Compreender o efeito dos microRNAs no cancro é essencial para interferir com a sua biologia e, consequentemente, gerar estratégias terapêuticas utilizando microRNAs na luta contra esta doença devastadora.