Absence of p16, p21 and p53 gene alterations in hepatocellular carcinomas induced by N-nitrosodiethylamine or a choline-deficient L-amino acid-defined diet in rats

MiR-30e-3p Influences Tumor Phenotype through MDM2/TP53 Axis and Predicts Sorafenib Resistance in Hepatocellular Carcinoma

The molecular background of hepatocellular carcinoma (HCC) is highly heterogeneous, and biomarkers predicting response to treatments are an unmet clinical need. We investigated miR-30e-3p contribution to HCC phenotype and response to sorafenib, as well as the mutual modulation of TP53/MDM2 pathway, in HCC tissues and preclinical models. MiR-30e-3p was downregulated in human and rat HCCs, and its downregulation associated with TP53 mutations. TP53 contributed to miR-30e-3p biogenesis, and MDM2 was identified among its target genes, establishing an miR-30e-3p/TP53/MDM2 feedforward loop and accounting for miR-30e-3p dual role based on TP53 status. EpCAM, PTEN, and p27 were demonstrated as miR-30e-3p additional targets mediating its contribution to stemness and malignant features. In a preliminary cohort of patients with HCC treated with sorafenib, increased miR-30e-3p circulating levels predicted the development of resistance. In conclusion, molecular background dictates miR-30e-3p dual behavior in HCC. Mdm2 targeting plays a predominant tumor suppressor function in wild-type TP53 contexts, whereas other targets such as PTEN, p27, and EpCAM gain relevance and mediate miR-30e-3p oncogenic role in nonfunctional TP53 backgrounds. Increased circulating levels of miR-30e-3p predict the development of sorafenib resistance in a preliminary series of patients with HCC and deserve future investigations. SIGNIFICANCE: The dual role of miR-30e-3p in HCC clarifies how the molecular context dictates the tumor suppressor or oncogenic function played by miRNAs.

High-fat diet modifies expression of hepatic cellular senescence gene p16(INK4a) through chromatin modifications in adult male rats

Background

Liver is the crucial organ as a hub for metabolic reactions. p16(INK4a) is a well-established cyclin-dependent kinase (CDK) inhibitor that plays important role in the molecular pathways of senescence, which lead to irreversible cell cycle arrest with secretion of proinflammatory cytokines and mitochondrial dysfunction. This study tested the hypothesis that cellular senescence regulated by p16(INK4a) is associated with high-fat diet in adult male rats.

Methods

Sprague Dawley rats were fed a high-fat (HF) diet or a control (C) diet for 9 weeks after weaning. At 12 weeks of age, liver samples of male rats were collected to investigate the key genes and liver physiological status.

Results

Both mRNA and protein expression level of cellular senescence marker, p16(INK4a), was increased significantly in HF group when compared to C group. A decrease of tri-methylated histone H3 lysine 27 (H3K27Me3) in the coding region of p16(INK4a) was observed. On the other hand, mRNA and protein expression of another inhibitor of cyclin-dependent kinase, p21(Cip1), was decreased significantly in HF group; however, no significant chromatin modification was found in this gene. Histological analysis demonstrated hepatic steatosis in HF group as well as severe fat accumulation.

Conclusions

Our study demonstrated that HF diet regulated cellular senescence marker p16(INK4a) through chromatin modifications, which may promote hepatic fat accumulation and steatosis.

Absence of p53 gene expression in selenium molecular prevention of chemically induced hepatocarcinogenesis in rats

BACKGROUND/AIM

p53 pathway is thought by many researchers to be critically involved in selenium's chemoprevention or in hepatocarcinogenesis. The aim of this study was to investigate the gene expression of p53, p21 and B-cell lymphoma-2 (bcl-2) using preventive and therapeutic approaches of selenium in chemically induced hepatocarcinogenesis in rats.

MATERIALS AND METHODS

Rats were divided randomly into six groups: Negative control, positive control (diethyl nitrosamine +2-acetylaminofluorene), preventive group, preventive control (respective control for preventive group), therapeutic group and therapeutic control (respective control for therapeutic group). p53, p21 and bcl-2 genes on liver tissues were measured using real-time polymerase chain reaction.

RESULTS

The expression of p53 was only significant in the therapeutic control. The expression of bcl-2 was insignificant in all the groups. p21 expression was significant in all the groups except the preventive group.

CONCLUSIONS

The selenium molecular mechanism for liver cancer prevention is not through the p53 pathway. Also, the absence of p53 is not necessary for chemically induced liver cancer in rats.

Development of hepatocellular adenomas and carcinomas associated with fibrosis in C57BL/6J male mice given a choline-deficient, L-amino acid-defined diet

Development of hepatocellular carcinomas in rats caused by a choline-deficient, L-amino acid-defined (CDAA) diet, usually associated with fatty liver, fibrosis, cirrhosis and oxidative DNA damage, has been recognized as a useful model of hepatocarcinogenesis caused by endogenous factors. In the present study, in order to further explore involved factors and genes, we established an equivalent model in spontaneous liver tumor-resistant C57BL/6J mice. Six-week-old males and females were continuously fed the CDAA diet and histological liver lesions and oxidative DNA damage due to 8-hydroxydeoxyguanosine (8-OHdG) were examined after 22, 65 and 84 weeks. In male mice, fatty change and fibrosis were evident at 22 weeks, and preneoplastic foci of altered hepatocytes were seen at an incidence of 8/8 (100%) and a multiplicity of 6.6 +/- 4.0 per mouse at 65 weeks. Hepatocellular adenomas and carcinomas developed at incidences of 16/24 (66.7%) and 5/24 (20.8%), and multiplicities of 1.42 +/- 1.32 and 0.29 +/- 0.62, respectively, at 84 weeks. The female mice exhibited resistance to development of these lesions. The CDAA diet also increased 8-OHdG levels in male but not female mice. These results indicate that a CDAA diet causes hepatocellular preneoplastic foci, adenomas and carcinomas associated with fibrosis and oxidative DNA damage in mice, as in rats, providing a hepatocarcinogenesis model caused by endogenous factors in mice.

Increased expression of cyclooxygenase-2 protein during rat hepatocarcinogenesis caused by a choline-deficient, L-amino acid-defined diet and chemopreventive efficacy of a specific inhibitor, nimesulide

Expression of cyclooxygenase (COX)-2 protein during rat hepatocarcinogenesis associated with fatty change, fibrosis, cirrhosis and oxidative DNA damage, caused by a choline-deficient, L-amino acid-defined (CDAA) diet were investigated in F344 male rats, along with the chemopreventive efficacy of the specific COX-2 inhibitor, nimesulide (NIM). Nimesulide, which was administered in the diet at concentrations of 200, 400, 600 and 800 p.p.m. for 12 weeks, decreased the number and size of preneoplastic enzyme-altered liver foci, levels of oxidative DNA damage, and the grade and incidence of fibrosis in a dose-dependent manner. A preliminary long-term study of 65 weeks also revealed that 800 p.p.m. NIM decreased the multiplicity of neoplastic nodules and hepatocellular carcinomas and prevented the development of cirrhosis. Western blot analysis revealed that COX-2 protein was barely expressed in control livers and increased approximately 2.9-fold in the livers of rats fed on a CDAA diet for 12 weeks and approximately 4.5-5.4-fold in tumors, with a diameter larger than 5 mm, at 80 weeks. Immunohistochemically, COX-2 protein was positive in sinusoidal and stromal cells in fibrotic septa, which were identified by immunoelectron microscopy as Kupffer cells, macrophages, either activated Ito cells or fibroblasts, after exposure to the CDAA diet for 12 weeks, whereas it was only occasionally weakly positive in sinusoidal, probably Kupffer, cells in control livers. In neoplastic nodules in rats fed on a CDAA diet for 30 and 80 weeks, sinusoidal cells and cells with relatively large round nuclei and scanty cytoplasm were strongly positive for COX-2 protein, with the neoplastic hepatocytes in the minority of the nodules, but not the cancer cells, being moderately positive. These results clearly indicate that rat hepatocarcinogenesis, along with fatty change, fibrosis and cirrhosis, is associated with increased expression of COX-2 protein, and point to the chemopreventive efficacy of a selective COX-2 inhibitor against, at least, the early stages of hepatocarcinogenesis.