Genetically induced hepatocellular carcinoma (HCC) models are generally used to investigate carcinogenesis pathways, but very few attempts were made to valorize them for pharmacological testing. This ...study describes a micro-computed tomography (micro-CT) - based methodology for the diagnostic and lifelong follow-up of HCC in the hepatocyte-specific Trim24-null mouse line. Myo-inositol trispyrophosphate (ITPP) was tested as anti-cancer drug.
Partial hepatectomy was performed in 2 months-old Trim24-null mice, in order to accelerate the carcinogenesis process. HCC diagnosis was obtained by micro-CT scan with double contrast agent: 10 μl/g Fenestra™ LC was injected intraperitoneally 6 h prior to imaging and 10 μl/g Fenestra™ VC was injected intravenously 15 min prior to imaging. Twenty three hepatocyte-specific Trim24-null mice were considered for ITPP testing (3 mg/g/week intraperitoneally during 10 months in 12 mice, versus 11 controls). Lifelong follow-up was performed using micro-CT. Comparative analysis was performed using unpaired t test with Welch correction and survival curves were compared by log-rank test. Gene expression analysis was performed using the RT q-PCR technique.
Double contrast micro-CT scan allowed HCC diagnosis as hypodense, isodense or hyperdense nodules. Positive predictive value was 81.3 %. Negative predictive value was 83.3 %. Tumor growth could be objectified by micro-CT scan before the ITPP treatment was started, and at 3 and 9 months follow-up. Significant progression of tumor volume was demonstrated in the both groups, with no difference between groups (p > 0.05). In the ITPP group, a mild decrease in tumor doubling time was first observed (31.9 +/- 12 days, p > 0.05) followed by a significant increase (59.8 +/- 18.3 days, p = 0.008). However, tumor doubling time was not different between groups (p > 0.05). Median survival after treatment initiation was 223 days (controls) versus 296 days (ITPP group, p = 0.0027). HIF1α, VEGF, glutamine synthase, osteopontin expression levels were not significantly modified at the end of follow-up. In the ITPP group, the p53 expression profile was inversed as compared to the control group, higher in non-tumor livers than in tumors.
ITPP treatment allowed for a two-month survival improvement, with better tolerance of tumor burden and apoptosis increase in non-tumor, pathological livers.
TRIM involvement in transcriptional regulation Cammas, Florence; Khetchoumian, Konstantin; Chambon, Pierre ...
Advances in experimental medicine and biology,
01/2012, Letnik:
770
Journal Article
Recenzirano
Members of the tripartite motif (TRIM) protein family are found in all multicellular eukaryotes and function in a wide range of cellular processes such as cell cycle regulation, differentiation, ...development, oncogenesis and viral response. Over the past few years, several TRIM proteins have been reported to control gene expression through regulation of the transcriptional activity of numerous sequence-specific transcription factors. These proteins include the transcriptional intermediary factor 1 (TIF1) regulators, the promyelocytic leukemia tumor suppressor PML and the RET finger protein (RFP). In this chapter, we will consider the molecular interactions made by these TRIM proteins and will attempt to clarify some of the molecular mechanisms underlying their regulatory effect on transcription.
The definition of embryonic potency and induction of specific cell fates are intimately linked to the tight control over TGFbeta signaling. Although extracellular regulation of ligand availability ...has received considerable attention in recent years, surprisingly little is known about the intracellular factors that negatively control Smad activity in mammalian tissues. By means of genetic ablation, we show that the Smad4 inhibitor ectodermin (Ecto, also known as Trim33 or Tif1gamma) is required to limit Nodal responsiveness in vivo. New phenotypes, which are linked to excessive Nodal activity, emerge from such a modified landscape of Smad responsiveness in both embryonic and extra-embryonic territories. In extra-embryonic endoderm, Ecto is required to confine expression of Nodal antagonists to the anterior visceral endoderm. In trophoblast cells, Ecto precisely doses Nodal activity, balancing stem cell self-renewal and differentiation. Epiblast-specific Ecto deficiency shifts mesoderm fates towards node/organizer fates, revealing the requirement of Smad inhibition for the precise allocation of cells along the primitive streak. This study unveils that intracellular negative control of Smad function by ectodermin/Tif1gamma is a crucial element in the cellular response to TGFbeta signals in mammalian tissues.
Retinoic acid (RA), the active derivative of vitamin A, is an important signaling molecule that controls various developmental processes and influence the proliferation and differentiation of a ...variety of cell types. RA exerts its biological functions primarily through binding to and activating nuclear RA receptors (RARs, which include the RAR alpha, beta and gamma isotypes RARA, RARB and RARC). Aberrant expression or impaired function of these nuclear receptors has been linked to diverse types of cancer. RARs are RA-dependent transcription factors that regulate gene expression through the recruitment of different co-regulators (co-activators and co-repressors). TRIM24 (formerly known as TIF1 alpha) was among the first co-regulators identified as interacting with RARs in a ligand-dependent fashion, and it was recently shown to function in mice as a potent liver-specific tumor suppressor by attenuating Rara-mediated transcription. The fact that Trim24(-/-), but not Trim24(-/-)Rara(+/-), mutant mice are highly predisposed to the development of hepatocellular carcinoma (HCC) has significant implications in cancer research. This result, along with the observation that in response to pharmacological inhibition of the RA signaling, hepatocytes lacking Trim24 loose their ability to proliferate, strongly implicates Rara as a proto-oncogene in hepatocytes and demonstrates that overactivated RA signaling is deleterious to liver homeostasis.
Calcification of arteries is a major risk factor for cardiovascular mortality in humans. Using genetic approaches, we demonstrate here that the transcriptional intermediary factor 1alpha (TIF1alpha), ...recently shown to function as a tumor suppressor in murine hepatocytes, also participates in a molecular cascade that prevents calcifications in arterioles and medium-sized arteries. We further provide genetic evidence that this function of TIF1alpha is not exerted in hepatocytes. The sites of ectopic calcifications in mutant mice lacking TIF1alpha resemble those seen in mice carrying an activating mutation of the calcium sensor receptor (Casr) gene and, in TIF1alpha-deficient kidneys, Casr expression is increased together with that of many other vitamin D receptor (VDR) direct target genes, namely Car2, Cyp24a1, Trpv5, Trpv6, Calb1, S100g, Pthlh, and Spp1. Thus, our data indicate that TIF1alpha represses the VDR pathway in kidney and suggest that an up-regulation of Casr expression in this organ could account for ectopic calcifications generated upon TIF1alpha deficiency. Interestingly, the calcifying arteriopathy of TIF1alpha-null mutant mice shares features with the human age-related Mönckeberg's disease and, overall, the TIF1alpha-null mutant pathological phenotype supports the hypothesis that aging is promoted by increased activity of the vitamin D signaling pathway.
Calcification of arteries is a major risk factor for cardiovascular mortality in humans. Using genetic approaches, we demonstrate here that the transcriptional intermediary factor 1α (TIF1α), ...recently shown to function as a tumor suppressor in murine hepatocytes, also participates in a molecular cascade that prevents calcifications in arterioles and medium-sized arteries. We further provide genetic evidence that this function of TIF1α is not exerted in hepatocytes. The sites of ectopic calcifications in mutant mice lacking TIF1α resemble those seen in mice carrying an activating mutation of the calcium sensor receptor (Casr) gene and, in TIF1α-deficient kidneys, Casr expression is increased together with that of many other vitamin D receptor (VDR) direct target genes, namely Car2, Cyp24a1, Trpv5, Trpv6, Calb1, S100g, Pthlh, and Spp1. Thus, our data indicate that TIF1α represses the VDR pathway in kidney and suggest that an up-regulation of Casr expression in this organ could account for ectopic calcifications generated upon TIF1α deficiency. Interestingly, the calcifying arteriopathy of TIF1α-null mutant mice shares features with the human age-related Monckeberg's disease and, overall, the TIF1α-null mutant pathological phenotype supports the hypothesis that aging is promoted by increased activity of the vitamin D signaling pathway. PUBLICATION ABSTRACT
In previous studies transcriptional intermediary factor 1alpha (TIF1alpha) was identified as a direct binding partner and potential transcriptional coactivator for nuclear receptors (NRs) but its ...overexpression inhibited, rather than enhanced, transcriptional activation by NRs. Here we show that TIF1alpha bound to and enhanced the function of the C-terminal activation domain (AD) of coactivator associated arginine methyltransferase 1 (CARM1) and the N-terminal AD of glucocorticoid receptor-interacting protein 1 (GRIP1). Furthermore, although TIF1alpha had little or no NR coactivator activity by itself, it cooperated synergistically with GRIP1 and CARM1 to enhance NR-mediated transcription. Inhibition of endogenous TIF1alpha expression reduced transcriptional activation by the GRIP1 N-terminal domain but not by the CARM1 C-terminal domain, suggesting that TIF1alpha may be more important for mediating the activity of the former than the latter. Reduction of endogenous TIF1alpha levels also compromised the androgen-dependent induction of an endogenous target gene of the androgen receptor. Finally, TIF1alpha formed a ternary complex with the GRIP1 N-terminal and CARM1 C-terminal domains. Thus, we conclude that TIF1alpha cooperates with NR coactivators GRIP1 and CARM1 by forming a stable ternary complex with them and enhancing the AD function of one or both of them.
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