RESUMO
In living organisms, cells sense mechanical forces (shearing, tensile, and compressive) and respond to those physical cues through a process called mechanotransduction. This process includes the simultaneous activation of biochemical signaling pathways. Recent studies mostly on human cells revealed that compressive forces selectively modulate a wide range of cell behavior, both in compressed and in neighboring less compressed cells. Besides participating in tissue homeostasis such as bone healing, compression is also involved in pathologies, including intervertebral disc degeneration or solid cancers. In this review, we will summarize the current scattered knowledge of compression-induced cell signaling pathways and their subsequent cellular outputs, both in physiological and pathological conditions, such as solid cancers.
Assuntos
Mecanotransdução Celular , Neoplasias , Humanos , Transdução de SinaisRESUMO
BACKGROUND AND AIMS: Earlier diagnosis and treatment of intrahepatic cholangiocarcinoma (iCCA) are necessary to improve therapy, yet limited information is available about initiation and evolution of iCCA precursor lesions. Therefore, there is a need to identify mechanisms driving formation of precancerous lesions and their progression toward invasive tumors using experimental models that faithfully recapitulate human tumorigenesis. APPROACH AND RESULTS: To this end, we generated a mouse model which combines cholangiocyte-specific expression of KrasG12D with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet-induced inflammation to mimic iCCA development in patients with cholangitis. Histological and transcriptomic analyses of the mouse precursor lesions and iCCA were performed and compared with human analyses. The function of genes overexpressed during tumorigenesis was investigated in human cell lines. We found that mice expressing KrasG12D in cholangiocytes and fed a DDC diet developed cholangitis, ductular proliferations, intraductal papillary neoplasms of bile ducts (IPNBs), and, eventually, iCCAs. The histology of mouse and human IPNBs was similar, and mouse iCCAs displayed histological characteristics of human mucin-producing, large-duct-type iCCA. Signaling pathways activated in human iCCA were also activated in mice. The identification of transition zones between IPNB and iCCA on tissue sections, combined with RNA-sequencing analyses of the lesions supported that iCCAs derive from IPNBs. We further provide evidence that tensin-4 (TNS4), which is stimulated by KRASG12D and SRY-related HMG box transcription factor 17, promotes tumor progression. CONCLUSIONS: We developed a mouse model that faithfully recapitulates human iCCA tumorigenesis and identified a gene cascade which involves TNS4 and promotes tumor progression.
Assuntos
Neoplasias dos Ductos Biliares/genética , Carcinoma Ductal/genética , Colangiocarcinoma/genética , Modelos Animais de Doenças , Neoplasias Hepáticas Experimentais/genética , Camundongos , Tensinas/genética , Animais , Neoplasias dos Ductos Biliares/induzido quimicamente , Neoplasias dos Ductos Biliares/metabolismo , Neoplasias dos Ductos Biliares/patologia , Carcinoma Ductal/induzido quimicamente , Carcinoma Ductal/metabolismo , Carcinoma Ductal/patologia , Carcinoma Papilar/induzido quimicamente , Carcinoma Papilar/genética , Carcinoma Papilar/metabolismo , Carcinoma Papilar/patologia , Colangiocarcinoma/induzido quimicamente , Colangiocarcinoma/metabolismo , Colangiocarcinoma/patologia , Colangite/induzido quimicamente , Colangite/complicações , Proteínas HMGB/genética , Proteínas HMGB/metabolismo , Neoplasias Hepáticas Experimentais/induzido quimicamente , Neoplasias Hepáticas Experimentais/metabolismo , Neoplasias Hepáticas Experimentais/patologia , Proteínas Proto-Oncogênicas p21(ras)/genética , Piridinas/toxicidade , Fatores de Transcrição SOXF/genética , Fatores de Transcrição SOXF/metabolismo , Transdução de Sinais , Tensinas/metabolismoRESUMO
BACKGROUND & AIMS: Alterations of individual genes variably affect the development of hepatocellular carcinoma (HCC). Thus, we aimed to characterize the function of tumor-promoting genes in the context of gene regulatory networks (GRNs). METHODS: Using data from The Cancer Genome Atlas, from the LIRI-JP (Liver Cancer - RIKEN, JP project), and from our transcriptomic, transfection and mouse transgenic experiments, we identify a GRN which functionally links LIN28B-dependent dedifferentiation with dysfunction of ß-catenin (CTNNB1). We further generated and validated a quantitative mathematical model of the GRN using human cell lines and in vivo expression data. RESULTS: We found that LIN28B and CTNNB1 form a GRN with SMARCA4, Let-7b (MIRLET7B), SOX9, TP53 and MYC. GRN functionality is detected in HCC and gastrointestinal cancers, but not in other cancer types. GRN status negatively correlates with HCC prognosis, and positively correlates with hyperproliferation, dedifferentiation and HGF/MET pathway activation, suggesting that it contributes to a transcriptomic profile typical of the proliferative class of HCC. The mathematical model predicts how the expression of GRN components changes when the expression of another GRN member varies or is inhibited by a pharmacological drug. The dynamics of GRN component expression reveal distinct cell states that can switch reversibly in normal conditions, and irreversibly in HCC. The mathematical model is available via a web-based tool which can evaluate the GRN status of HCC samples and predict the impact of therapeutic agents on the GRN. CONCLUSIONS: We conclude that identification and modelling of the GRN provide insights into the prognosis of HCC and the mechanisms by which tumor-promoting genes impact on HCC development. LAY SUMMARY: Hepatocellular carcinoma (HCC) is a heterogeneous disease driven by the concomitant deregulation of several genes functionally organized as networks. Here, we identified a gene regulatory network involved in a subset of HCCs. This subset is characterized by increased proliferation and poor prognosis. We developed a mathematical model which uncovers the dynamics of the network and allows us to predict the impact of a therapeutic agent, not only on its specific target but on all the genes belonging to the network.
Assuntos
Carcinoma Hepatocelular/genética , Redes Reguladoras de Genes/efeitos dos fármacos , Neoplasias Hepáticas/genética , Modelos Teóricos , beta Catenina/genética , beta Catenina/metabolismo , Animais , Carcinoma Hepatocelular/patologia , Estudos de Coortes , Células Hep G2 , Humanos , Neoplasias Hepáticas/patologia , Camundongos , Camundongos Transgênicos , Prognóstico , Proteínas de Ligação a RNA/antagonistas & inibidores , Proteínas de Ligação a RNA/metabolismo , Análise de Sequência de RNA , Transcriptoma , TransfecçãoRESUMO
Testosterone production by Leydig cells is a tightly regulated process requiring synchronized expression of several steroidogenic genes by numerous transcription factors. Myocyte enhancer factor 2 (MEF2) are transcription factors recently identified in somatic cells of the male gonad. In other tissues, MEF2 factors are essential regulators of organogenesis and cell differentiation. So far in the testis, MEF2 factors were found to regulate Leydig cell steroidogenesis by controlling Nr4a1 and Star gene expression. To expand our understanding of the role of MEF2 in Leydig cells, we performed microarray analyses of MEF2-depleted MA-10 Leydig cells, and the results were analyzed using Partek and Ingenuity Pathway Analysis software. Several genes were differentially expressed in MEF2-depleted Leydig cells, and 16 were validated by quantitative RT-PCR. A large number of these genes are known to be involved in fertility, gonad morphology, and steroidogenesis. These include Ahr, Bmal1, Cyp1b1, Hsd3b1, Hsd17b7, Map2k1, Nr0b2, Pde8a, Por, Smad4, Star, and Tsc22d3, which were all downregulated in the absence of MEF2. In silico analyses revealed the presence of MEF2-binding sites within the first 2 kb upstream of the transcription start site of the Por, Bmal1, and Nr0b2 promoters, suggesting direct regulation by MEF2. Using transient transfections in MA-10 Leydig cells, small interfering RNA knockdown, and a MEF2-Engrailed dominant negative, we found that MEF2 activates the Por, Bmal1, and Nr0b2 promoters and that this requires an intact MEF2 element. Our results identify novel target genes for MEF2 and define MEF2 as an important regulator of Leydig cell function and male reproduction.
Assuntos
Células Intersticiais do Testículo/metabolismo , Fatores de Transcrição MEF2/metabolismo , Regiões Promotoras Genéticas , Testosterona/metabolismo , Animais , Linhagem Celular Tumoral , Masculino , Camundongos , Fosfoproteínas/metabolismo , Transcrição GênicaRESUMO
In Leydig cells, steroidogenic acute regulatory protein (STAR) participates in cholesterol shuttling from the outer to the inner mitochondrial membrane, the rate-limiting step in steroidogenesis. Steroid hormone biosynthesis and steroidogenic gene expression are regulated by LH, which activates various signaling pathways and transcription factors, including cAMP/Ca(2+)/CAMK (Ca(2+)/calmodulin-dependent kinase)-myocyte enhancer factor 2 (MEF2). The 4 MEF2 transcription factors are essential regulators of cell differentiation and organogenesis in numerous tissues. Recently, MEF2 was identified in Sertoli and Leydig cells of the testis. Here, we report that MEF2 regulates steroidogenesis in mouse MA-10 Leydig cells by acting on the Star gene. In MA-10 cells depleted of MEF2 using siRNAs (small interfering RNAs), STAR protein levels, Star mRNA levels, and promoter activity were significantly decreased. On its own, MEF2 did not activate the mouse Star promoter but was found to cooperate with forskolin/cAMP. By chromatin immunoprecipitation and DNA precipitation assays, we confirmed MEF2 binding to a consensus element located at -232 bp of the Star promoter. Mutation or deletion of the MEF2 element reduced but did not abrogate the MEF2/cAMP cooperation, indicating that MEF2 cooperates with other DNA-bound transcription factor(s). We identified GATA4 (GATA binding protein 4) as a partner for MEF2 in Leydig cells, because mutation of the GATA element abrogated the MEF2/cAMP cooperation on a reporter lacking a MEF2 element. MEF2 and GATA4 interact as revealed by coimmunoprecipitation, and MEF2 and GATA4 transcriptionally cooperate on the Star promoter. Altogether, our results define MEF2 as a novel regulator of steroidogenesis and Star transcription in Leydig cells and identify GATA4 as a key partner for MEF2-mediated action.