Ripe papaya pectins inhibit the proliferation of colon cancer spheroids and the formation of chemically induced aberrant crypts in rats colons.

Pectins are a class of soluble polysaccharides that can have anticancer properties through several mechanisms. This study aimed to characterize the molecular structure of water-soluble fractions (WSF) derived from ripe and unripe papayas and assess their biological effects in two models: the 3D colon cancer spheroids to measure cell viability and cytotoxicity, and the in vivo model to investigate the inhibition of preneoplastic lesions in rats. WSF yield was slightly higher in ripe papaya, and both samples mainly consisted of pectin. Both pectins inhibited the growth of colon cancer HT29 and HCT116 spheroids. Unripe pectin disturbed HT29/NIH3T3 spheroid formation, decreased HCT116 spheroid viability, and increased spheroid cytotoxicity. Ripe pectin had a more substantial effect on the reduction of spheroid viability for HT29 spheroids. Furthermore, in vivo experiments on a rat model revealed a decrease in aberrant crypt foci (ACF) formation for both pectins and increased apoptosis in colonocytes for ripe papaya pectins. The results suggest potential anticancer properties of papaya pectin, with ripe pectin showing a higher potency.

Past, present, and future of chemically induced hepatocarcinogenesis rodent models: Perspectives concerning classic and new cancer hallmarks.

Hepatocellular carcinoma (HCC), the main primary liver cancer, accounts for 5 % of all incident cases and 8.4 % of all cancer-related deaths worldwide. HCC displays a spectrum of environmental risk factors (viral chronic infections, aflatoxin exposure, alcoholic- and nonalcoholic fatty liver diseases) that result in molecular complexity and heterogeneity, contributing to a rising epidemiological burden, poor prognosis, and non-satisfactory treatment options. The emergence of HCC (i.e., hepatocarcinogenesis) is a multistep and complex process that addresses many (epi)genetic alterations and phenotypic traits, the so-called cancer hallmarks. "Polymorphic microbiomes", "epigenetic reprogramming", "senescent cells" and "unlocking phenotypic plasticity" are trending hallmarks/enabling features in cancer biology. As the main molecular drivers of HCC are still undruggable, chemically induced in vivo models of hepatocarcinogenesis are useful tools in preclinical research. Thus, this narrative review aimed at recapitulating the basic features of chemically induced rodent models of hepatocarcinogenesis, eliciting their permanent translational value regarding the "classic" and the "new" cancer hallmarks/enabling features. We gathered state-of-art preclinical evidence on non-cirrhotic, inflammation-, alcoholic liver disease- and nonalcoholic fatty liver-associated HCC models, demonstrating that these bioassays indeed express the recently added hallmarks, as well as reflect the interplay between classical and new cancer traits. Our review demonstrated that these protocols remain valuable for translational preclinical application, as they recapitulate trending features of cancer science. Further "omics-based" approaches are warranted while multimodel investigations are encouraged in order to avoid "model-biased" responses.

Butyrate-containing structured lipids act on HDAC4, HDAC6, DNA damage and telomerase activity during promotion of experimental hepatocarcinogenesis.

Hepatocellular carcinoma (HCC) presents with a high treatment resistance and poor prognosis. Early diagnosis and preventive approaches such as chemoprevention are essential for the HCC control. Therefore, we evaluated the chemopreventive effects of butyrate-containing structured lipids (STLs) administered during the promotion stage of hepatocarcinogenesis in rats submitted to the 'resistant hepatocyte' (RH) model. Administration of butyrate-containing STLs inhibited the incidence and mean number of visible hepatic nodules per rat and reduced the number and area of glutathione S-transferase placental form-positive (GST-P+) preneoplastic focal lesions in the livers. This was accompanied by the induction of apoptosis and an increased level of hepatic butyric acid. Treatment with butyrate-containing STLs resulted in increased histone H3 lysine 9 (H3K9) acetylation, reduction of total histone deacetylase (HDAC) activity, and lower levels of HDAC4 and HDAC6 proteins. The chemopreventive effect of butyrate-containing STLs was also associated with the increased nuclear compartmentalization of p53 protein and reduced expression of the Bcl-2 protein. In addition, rats treated with butyrate-containing STLs showed decreased DNA damage and telomerase activity in the livers. These results demonstrate that the suppressive activity of butyrate-containing STLs is associated with inhibition of elevated during hepatocarcinogenesis chromatin-modifying proteins HDAC4 and HDAC6, subcellular redistribution of the p53 protein, and decreased DNA damage and telomerase activity.

Butyrate-containing structured lipids inhibit RAC1 and epithelial-to-mesenchymal transition markers: a chemopreventive mechanism against hepatocarcinogenesis.

Hepatocellular carcinoma (HCC) is one of the most aggressive human cancers. The rising incidence of HCC worldwide and its resistance to pharmacotherapy indicate that the prevention of HCC development may be the most impactful strategy to improve HCC-related morbidity and mortality. Among the broad range of chemopreventive agents, the use of dietary and nutritional agents is an attractive and promising approach; however, a better understanding of the mechanisms of their potential cancer suppressive action is needed to justify their use. In the present study, we investigated the underlying molecular pathways associated with the previously observed suppressive effect of butyrate-containing structured lipids (STLs) against liver carcinogenesis using a rat "resistant hepatocyte" model of hepatocarcinogenesis that resembles the development of HCC in humans. Using whole transcriptome analysis, we demonstrate that the HCC suppressive effect of butyrate-containing STLs is associated with the inhibition of the cell migration, cytoskeleton organization, and epithelial-to-mesenchymal transition (EMT), mediated by the reduced levels of RACGAP1 and RAC1 proteins. Mechanistically, the inhibition of the Racgap1 and Rac1 oncogenes is associated with cytosine DNA and histone H3K27 promoter methylation. Inhibition of the RACGAP1/RAC1 oncogenic signaling pathways and EMT may be a valuable approach for liver cancer prevention.

ß-ionone inhibits nonalcoholic fatty liver disease and its association with hepatocarcinogenesis in male Wistar rats.

Among the primary neoplasias that affect the liver, hepatocellular carcinoma (HCC) is the most frequent and the third leading cause of death related to cancer. Several risk factors predispose individuals to HCC such as nonalcoholic fatty liver disease (NAFLD), whose incidence has significantly increased worldwide. ß-ionone (ßI) isoprenoid is a known chemopreventive of hepatocarcinogenesis. However, the effects of this compound on NAFLD isolated or in association with hepatocarcinogenesis have not yet been evaluated. A high-fat emulsion administered for 6 weeks resulted in NAFLD in male rats, and oral treatment with ßI during this period significantly attenuated its development. Moreover, the presence of NAFLD potentiated hepatocarcinogenesis induced by the resistant hepatocyte (RH) model in these animals by increasing the number and percentage of the liver section area occupied by placental glutathione S-transferase (GST-P)-positive persistent preneoplastic lesions (pPNLs), that are thought to evolve into HCC. This indicates that this NAFLD/RH protocol is suitable for studies of the influence of NAFLD on the HCC development. Therefore, here we also investigated the chemopreventive effect of ßI under these two associated conditions. In this context, ßI reduced the number and percentage of the liver section area occupied by pPNLs, as well as cell proliferation and the number of oval cells, which are considered potential targets for the development of HCC. Thus, ßI presents not only a promising inhibitory effect on NAFLD isolated but also chemopreventive activity when it is associated with hepatocarcinogenesis.

Antiangiogenic effects of the chemopreventive agent tributyrin, a butyric acid prodrug, during the promotion phase of hepatocarcinogenesis.

Agents that inhibit angiogenic factors may prevent the development of hepatocellular carcinoma (HCC). Thus, the objective of this study was to kinetically evaluate the antiangiogenic activity of tributyrin (TB), a butyric acid prodrug, in the promotion stage of hepatocarcinogenesis. For this purpose, the resistant hepatocyte (RH) model was used for induction of preneoplastic lesions in Wistar rats. During the promotion phase, the animals received TB or maltodextrin (MD) as control daily. The rats were killed at three time-points (P1, P2 and P3). Increased expression of Vegfa and Vegfr2 was observed during promotion phase of hepatocarcinogenesis, which was not reversed by TB treatment. However, TB treatment reduced the expression of cluster of differentiation (CD) 34-positive vessels at P3 and α-smooth muscle actin (α-SMA)-positive vessels at P2 compared with MD. Enhanced levels of hypoxia inducible factor-1α (HIF-1α) and phosphorylated extracellular signal-regulated kinases (pERK) were detected at P3 when compared with P1 and P2 in the MD treatment. TB treatment reduced the levels of HIF-1α and pERK at P3 relative to the MD control. Experiments with human umbilical vein endothelial cells (HUVEC) showed that sodium butyrate (NaBu) inhibited cell migration and tube formation, confirming the antiangiogenic activity of its prodrug TB. In conclusion, antiangiogenic activity of TB is an early event that already occurs in preneoplastic livers, reinforcing its potential chemopreventive effects against HCC.

Nutritional Epigenetics and the Prevention of Hepatocellular Carcinoma with Bioactive Food Constituents.

Hepatocellular carcinoma (HCC) is an aggressive and life-threatening disease often diagnosed at intermediate or advanced stages, which substantially limits therapeutic approaches to its successful treatment. This indicates that the prevention of HCC may be the most promising strategy in reducing its incidence and mortality. Emerging evidence indicates that numerous nutrients and nonnutrient dietary bioactive components can reduce the occurrence and/or delay the development of HCC through modifications of deregulated epigenetic mechanisms. This review examines the existing knowledge on the epigenetic mechanism-based studies in in vitro and in vivo models of HCC on the chemopreventive potential of epigenetic food components, including dietary methyl-group donors, epigallocatechin-3-gallate, sodium butyrate, resveratrol, curcumin, and sulforaphane, on liver carcinogenesis. Future direction and potential challenges in the effective use of bioactive food constituents in the prevention of HCC are highlighted and discussed.

Suppressing activity of tributyrin on hepatocarcinogenesis is associated with inhibiting the p53-CRM1 interaction and changing the cellular compartmentalization of p53 protein.

Hepatocellular carcinoma (HCC), an aggressive and the fastest growing life-threatening cancer worldwide, is often diagnosed at intermediate or advanced stages of the disease, which substantially limits therapeutic approaches for its successful treatment. This indicates that the prevention of hepatocarcinogenesis is probably the most promising approach to reduce both the HCC incidence and cancer-related mortality. In previous studies, we demonstrated a potent chemopreventive effect of tributyrin, a butyric acid prodrug, on experimental hepatocarcinogenesis. The cancer-inhibitory effect of tributyrin was linked to the suppression of sustained cell proliferation and induction of apoptotic cell death driven by an activation of the p53 apoptotic signaling pathway. The goal of the present study was to investigate the underlying molecular mechanisms linked to tributyrin-mediated p53 activation. Using in vivo and in vitro models of liver cancer, we demonstrate that an increase in the level of p53 protein in nuclei, a decrease in the level of cytoplasmic p53, and, consequently, an increase in the ratio of nuclear/cytoplasmic p53 in rat preneoplastic livers and in rat and human HCC cell lines caused by tributyrin or sodium butyrate treatments was associated with a marked increase in the level of nuclear chromosome region maintenance 1 (CRM1) protein. Mechanistically, the increase in the level of nuclear p53 protein was associated with a substantially reduced binding interaction between CRM1 and p53. The results demonstrate that the cancer-inhibitory activity of sodium butyrate and its derivatives on liver carcinogenesis may be attributed to retention of p53 and CRM1 proteins in the nucleus, an event that may trigger activation of p53-mediated apoptotic cell death in neoplastic cells.

The chemopreventive activity of butyrate-containing structured lipids in experimental rat hepatocarcinogenesis.

SCOPE: Emerging evidence indicates that the use of bioactive food components is a promising strategy to prevent the development of liver cancer. The goal of this study was to examine the chemopreventive effect of butyrate-containing structured lipids (STLs) produced by an enzymatic interesterification of tributyrin and flaxseed oil on rat hepatocarcinogenesis. METHODS AND RESULTS: Male Wistar rats were subjected to a classic "resistant hepatocyte" model of liver carcinogenesis and treated with STLs, tributyrin or flaxseed oil during the initial phases of hepatocarcinogenesis. Treatment with STLs and tributyrin strongly inhibited the development of preneoplastic liver lesions. The chemopreventive activity of tributyrin was associated with the induction of apoptosis and reduction of the expression of major activated hepatocarcinogenesis-related oncogenes. Treatment with STLs caused substantially greater inhibitory effects than tributyrin on oncogene expression. CONCLUSION: These results demonstrate that the tumor-suppressing activity of butyrate-containing STLs is associated with its ability to prevent and inhibit activation of major hepatocarcinogenesis-related oncogenes. Enrichment of histone H3K9me3 and H3K27me3 at the promoter of Myc and Ccnd1 genes may be related to the inhibitory effect on oncogene expression in the livers of STL-treated rats.

Potencial quimiopreventivo de lipídios estruturados obtidos por interesterificação da tributirina com o óleo de linhaça na hepatocarcinogênese / Chemopreventive potential of structured lipids obtained by interesterification of tributyrin with flaxseed oil in hepatocarcinogenesis

O carcinoma hepatocelular (HCC) apresenta mau prognóstico o que torna importante sua quimioprevenção. Nesse sentido, a tributirina (TB), um inibidor de desacetilases de histonas (HDACi), mostrou-se um quimiopreventivo promissor da hepatocarcinogênese. Avaliaram-se aqui efeitos quimiopreventivos de lipídios estruturados (EST) obtidos por interesterificação enzimática a partir da TB com o óleo de linhaça (LIN). Ratos foram tratados com EST (grupo EST; 165 mg/100g peso corpóreo [p.c]), TB (grupo TB; 200 mg/100g p.c), LIN (grupo LIN; 133 mg/100g p.c), mistura de TB com LIN (grupo LIN; 165 mg/100g p.c) ou maltodextrina (MD) (grupo MD; controle isocalórico; 300 mg/100g p.c) diariamente durante 8 semanas consecutivas por gavagem. Duas semanas após início dos tratamentos, os animais foram submetidos ao modelo de hepatocarcinogênese do "hepatócito resistente" (RH). Os grupos EST e TB apresentaram atividade quimiopreventiva bloqueadora e supressora, respectivamente, da hepatocarcinogênese. TB induziu a apoptose, ao contrário dos EST. O tratamento com TB resultou na acetilação e trimetilação da H3K9 e H3K27, enquanto EST atuaram somente na trimetilação das mesmas. Quando analisada a expressão de genes envolvidos com modificações em histonas, EST e TB reduziram a expressão de Ezh2 e de Hdac4. Por outro lado, somente os EST aumentaram a expressão de Hdac6. Tal efeito por parte dos EST merece ser mais investigado, uma vez que esta desacetilase vem sendo sugerida como alvo potencial para o desenvolvimento de fármacos. Em conclusão, a atividade quimiopreventiva de EST e da TB envolve na hepatocarcinogênese experimental mecanismos epigenéticos que podem ou não ser distintos

Hepatocellular carcinoma (HCC) has a poor prognosis, which makes its chemoprevention important. Tributyrin (TB), which is a histone deacetylase inhibitor (HDACi), is a promising chemopreventive agent of hepatocarcinogenesis. The chemopreventive effects of structured lipids (STLs) that were obtained by the enzymatic interesterification of TB with flaxseed oil (FSO) were evaluated in the present study. Rats were treated with STLs (STL group, 165 mg/100 g body weight (bw)), TB (TB group, 200 mg/100 g bw), FSO (FSO group, 133 mg/100 g bw), TB mixed with FSO (BLD group, 165 mg/100g bw) or maltodextrin (MD) (MD group; isocaloric control; 300 mg/100 g bw) daily for eight consecutive weeks by gavage. Two weeks after the initiation of treatment, the animals were subjected to the resistant hepatocyte hepatocarcinogenesis model (RH). The STL and TB groups developed blocker and suppressive chemopreventive activity against hepatocarcinogenesis, respectively. TB treatment induced apoptosis, unlike the STL treatment. Additionally, TB treatment resulted in the acetylation and trimethylation of H3K9 and H3K27, whereas the STLs acted only in the trimethylation of these histones. When analyzing the expression of genes involved in histone modifications, the STLs and TB reduced enhancer of zeste homolog 2 (Ezh2) and histone deacetylase 4 (Hdac4) gene expression. Conversely, only the STLs increased Hdac6 gene expression. This effect of the STLs warrants further investigation because this deacetylase has been suggested as a potential drug development target. In conclusion, the chemopreventive activities of the STLs and TB in experimental hepatocarcinogenesis involve epigenetic mechanisms that may be distinct

The chemopreventive activity of the histone deacetylase inhibitor tributyrin in colon carcinogenesis involves the induction of apoptosis and reduction of DNA damage.

The chemopreventive activity of the histone deacetylase inhibitor (HDACi) tributyrin (TB), a prodrug of butyric acid (BA), was evaluated in a rat model of colon carcinogenesis. The animals were treated with TB (TB group: 200mg/100g of body weight, b.w.) or maltodextrin (MD isocaloric control group: 300 mg/100g b.w.) daily for 9 consecutive weeks. In the 3rd and 4th weeks of treatment, the rats in the TB and MD groups were given DMH (40 mg/kg b.w.) twice a week. After 9 weeks, the animals were euthanized, and the distal colon was examined. Compared with the control group (MD group), TB treatment reduced the total number of aberrant crypt foci (ACF; p<0.05) as well as the ACF with ≥4 crypts (p<0.05), which are considered more aggressive, but not inhibited the formation of DMH-induced O6-methyldeoxyguanosine DNA adducts. The TB group also showed a higher apoptotic index (p<0.05) and reduced DNA damage (p<0.05) compared with MD group. TB acted as a HDACi, as rats treated with the prodrug of BA had higher levels of histone H3K9 acetylation compared with the MD group (p<0.05). TB administration resulted in increased colonic tissue concentrations of BA (p<0.05) compared with the control animals. These results suggest that TB can be considered a promising chemopreventive agent for colon carcinogenesis because it reduced the number of ACF, including those that were more aggressive. Induction of apoptosis and reduction of DNA damage are cellular mechanisms that appear to be involved in the chemopreventive activity of TB.

ß-ionone inhibits persistent preneoplastic lesions during the early promotion phase of rat hepatocarcinogenesis: TGF-α, NF-κB, and p53 as cellular targets.

Dietary isoprenic derivatives such as ß-ionone (ßI) are a promising class of chemopreventive agents. In this study, cellular aspects of ßI protective activities during early hepatocarcinogenesis were evaluated. Male Wistar rats were submitted to "resistant hepatocyte" model and then received daily 16 mg/100 g body weight (b.w.) of ßI (ßI group) or only 0.25 mL/100 g b.w. of corn oil (vehicle, control group [CO]) during 4 wk, specifically during early promotion phase. Compared to controls, ßI inhibited (P < 0.05) the development of persistent preneoplastic lesions (pPNL), considered to be potential hepatocellular carcinoma (HCC) progression sites, and increased remodeling PNL (rPNL) (P < 0.05) that tend to regress to a normal phenotype. Increased ßI hepatic levels (P < 0.05), in the ßI group, were associated with its chemopreventive actions. Compared to control rats, ßI reduced the frequency of both pPNL and rPNL positive for tumor growth factor (TGF)-α (P < 0.05), reduced the frequency of pPNL stained for p65 (nuclear factor-kappaB; NF-κB) (P < 0.05), and reduced the frequency of pPNL positive for cytoplasmic p53 (P < 0.05). Our data demonstrated that ßI targets TGF-α, NF-κB, and p53 in initial phases of hepatocarcinogenesis and specifically inhibits PNL with increased probability to progress to HCC. This isoprenoid may represent a chemopreventive agent of choice for HCC control.

The chemopreventive activity of the butyric acid prodrug tributyrin in experimental rat hepatocarcinogenesis is associated with p53 acetylation and activation of the p53 apoptotic signaling pathway.

The reversibility of non-genotoxic phenotypic alterations has been explored in order to develop novel preventive and therapeutic approaches for cancer control. Previously, it has been demonstrated that histone deacetylase (HDAC) inhibitor tributyrin, a butyric acid prodrug, to have chemopreventive effects on rat hepatocarcinogenesis. The goal of this study was to determine molecular mechanisms associated with the chemopreventive activity of tributyrin. Male Wistar rats were allocated randomly to untreated control group and two experimental groups. Rats in the experimental group 1 were treated with maltodextrin (3g/kg body wt), and rats in experimental group 2 were treated with tributyrin (2g/kg body wt) daily for 8 weeks. Two weeks after treatment initiation, rats from experimental groups were subjected to a 'resistant hepatocyte' model of hepatocarcinogenesis. Treatment with tributyrin resulted in lower HDAC activity and Hdac3 and Hdac4 gene expression, and an increase of histone H3 lysine 9 and 18 and histone H4 lysine 16 acetylation as compared with the experimental group 1. In addition to the increase in histone acetylation, tributyrin caused an increase in the acetylation of the nuclear p53 protein. These changes were accompanied by a normalization of the p53-signaling network, particularly by the upregulation of pro-apoptotic genes, and a consequent increase of apoptosis and autophagy in the livers of tributyrin-treated rats. These results indicate that the chemopreventive activity of tributyrin may be related to an increase of histone and p53 acetylation, which could lead to the induction of the p53 apoptotic pathway.

Anticarcinogenic actions of tributyrin, a butyric acid prodrug.

Bioactive food compounds (BFCs) exhibit potential anticarcinogenic effects that deserve to be explored. Butyric acid (BA) is considered a promising BFC and has been used in clinical trials; however, its short half-life considerably restricts its therapeutic application. Tributyrin (TB), a BA prodrug present in milk fat and honey, has more favorable pharmacokinetic properties than BA, and its oral administration is also better tolerated. In vitro and in vivo studies have shown that TB acts on multiple anticancer cellular and molecular targets without affecting non-cancerous cells. Among the TB mechanisms of action, the induction of apoptosis and cell differentiation and the modulation of epigenetic mechanisms are notable. Due to its anticarcinogenic potential, strategies as lipid emulsions, nanoparticles, or structured lipids containing TB are currently being developed to improve its organoleptic characteristics and bioavailability. In addition, TB has minimal toxicity, making it an excellent candidate for combination therapy with other agents for the control of cancer. Despite the lack of data available in the literature, TB is a promising molecule for anticancer strategies. Therefore, additional preclinical and clinical studies should be performed using TB to elucidate its molecular targets and anticarcinogenic potential.

Lutein presents suppressing but not blocking chemopreventive activity during diethylnitrosamine-induced hepatocarcinogenesis and this involves inhibition of DNA damage.

Cancer chemopreventive agents are classified as blocking or suppressing agents if they inhibit initiation or promotion/progression phase of carcinogenesis, respectively. Two experiments were conducted in order to classify lutein as a blocking and/or suppressing agent during rat hepatocarcinogenesis. Inhibitory effects of lutein on hepatic preneoplastic lesions (PNL) and DNA strand breakage induced in Wistar rats by the resistant hepatocyte model of hepatocarcinogenesis (initiation with diethylnitrosamine and promotion with 2-acetylaminofluorene coupled with partial hepatectomy) were investigated when the carotenoid was administered specifically during initiation (experiment 1) or promotion (experiment 2) phase. Animals received by gavage during 2 (experiment 1) or six (experiment 2) consecutive weeks on alternate days 70 mg/kg body weight of lutein. Rats treated with only corn oil during these same periods and submitted to this model were used as controls. Treatment with lutein during initiation did not inhibit nor induced (P>0.05) hepatic preneoplastic lesions and DNA damage. On the other hand, treatment during promotion inhibited (P<0.05) the size of hepatic macroscopic nodules and DNA damage and increased (P<0.05) lutein hepatic levels that reached levels seen in human liver samples. Lutein presented inhibitory actions during promotion but not initiation of hepatocarcinogenesis, being classified as a suppressing agent. This reinforces lutein as a potential agent for liver cancer chemoprevention.

Farnesol and geraniol chemopreventive activities during the initial phases of hepatocarcinogenesis involve similar actions on cell proliferation and DNA damage, but distinct actions on apoptosis, plasma cholesterol and HMGCoA reductase.

Chemopreventive activities of farnesol (FOH) and geraniol (GOH) were evaluated during the initial phases of hepatocarcinogenesis. Rats received during eight consecutive weeks 25 mg/100 g body weight FOH (FOH group) or GOH (GOH group), or only corn oil (CO group, controls). Incidence (%) and mean number of visible hepatocyte nodules/animal were inhibited in FOH group (13% and 4 +/- 1; P < 0.05), but not in GOH group (42% and 18 +/- 17, P > 0.05), compared to CO group (100% and 42 +/- 17). Mean area (mm2) and % liver section area occupied by total hepatic placental glutathione S-transferase positive preneoplastic lesions (PNLs) were reduced in FOH group (0.09 +/- 0.06; 2.8 +/- 1.3; P < 0.05) compared to CO group (0.18 +/- 0.12; 10.0 +/- 2.8), while in GOH group only the mean area of these PNL was reduced (0.11 +/- 0.09; P < 0.05), but not the % liver section area occupied by them (5.1 +/- 1.1; P > 0.05). Compared to CO group, FOH and GOH groups showed reduced (P < 0.05) PNL cell proliferation and DNA damage, but only GOH group showed increased PNL apoptosis (P < 0.05). FOH group, but not GOH group, presented reduced (P < 0.05) total plasma cholesterol levels and increased (P < 0.05) hepatic levels of 3-hydroxy-3-methylglutaryl coenzyme A (HMGCoA) reductase mRNA, compared to CO group. No differences (P > 0.05) were observed between CO, FOH and GOH regarding hepatic levels of farnesoid X activated receptor (FXR) protein. Results indicate that FOH and GOH could represent promising chemopreventive agents against hepatocarcinogenesis. Inhibition of cell proliferation and DNA damage relate to both isoprenoids' anticarcinogenic actions while induction of apoptosis specifically relates to GOH protective actions. Inhibition of HMGCoA reductase activity could be associated with FOH, but not GOH anticarcinogenic actions. FXR does not seem to be involved in the isoprenoids' chemopreventive activities.

All-trans and 9-cis retinoic acids, retinol and beta-carotene chemopreventive activities during the initial phases of hepatocarcinogenesis involve distinct actions on glutathione S-transferase positive preneoplastic lesions remodeling and DNA damage.

Chemopreventive activities of all-trans retinoic acid (AtRA), 9-cis retinoic acid (9cRA), retinol (ROL) and beta-carotene (betaC) were evaluated during hepatocarcinogenesis. Rats received 1 mg/100 g body wt AtRA (AtRA group), 9cRA (9cRA group), ROL (ROL group), 7 mg/100 g body wt betaC (betaC group) or corn oil (CO group, controls). Hepatocyte nodule incidence was reduced (P < 0.05) in betaC group (46%), but not (P > 0.05) in AtRA (92%), 9cRA (92%) and ROL (82%) groups, compared with the CO group (100%). Multiplicity of these preneoplastic lesions (PNL) was different (P < 0.05) between CO group (44 +/- 9) and 9cRA (11 +/- 4), ROL (7 +/- 3) and betaC (4 +/- 2) groups, except for AtRA group (27 +/- 9; P > 0.05). Number/cm(2) liver section, mean area (mm(2)) and percent liver section area occupied by total (persistent + remodeling) placental glutathione S-transferase (GST-P) positive PNL was reduced (P < 0.05) in AtRA (107 +/- 13; 0.12 +/- 0.06; 13.9 +/- 3.9), 9cRA (71 +/- 12; 0.12 +/- 0.06; 6.8 +/- 2.2), ROL (96 +/- 13; 0.11 +/- 0.22; 6.8 +/- 2.0) and betaC (106 +/- 13; 0.08 +/- 0.03; 10.8 +/- 2.5) groups compared with CO group (166 +/- 14; 0.18 +/- 0.09; 28.6 +/- 5.2). Percent of remodeling GST-P positive PNL was increased (P < 0.05) in 9cRA (92 +/- 1), ROL (96 +/- 1) and betaC (93 +/- 1) groups, but not (P > 0.05) in AtRA group (90 +/- 2), compared with the CO group (86 +/- 1). Compared with the CO group, all groups present in PNL reduced (P < 0.05) cell proliferation and no differences (P > 0.05) in apoptosis. DNA damage [comet length (mum)] was reduced (P < 0.05) in ROL (87.9 +/- 2.6) and betaC (89.2 +/- 4.0) groups, but not in AtRA (94.8 +/- 4.1) and 9cRA (94.2 +/- 1.5) groups, compared with the CO group (100.4 +/- 3.9). AtRA, 9cRA, ROL and betaC presented chemopreventive activities against hepatocarcinogenesis. These involve inhibition of cell proliferation, but not induction of apoptosis. Increased remodeling of GST-P positive PNL relates to 9cRA, ROL and betaC actions, while inhibition of DNA damage relates to ROL and betaC actions.

Geranylgeraniol and beta-ionone inhibit hepatic preneoplastic lesions, cell proliferation, total plasma cholesterol and DNA damage during the initial phases of hepatocarcinogenesis, but only the former inhibits NF-kappaB activation.

Chemopreventive activities of the isoprenoids geranylgeraniol (GGO) and beta-ionone (BI) were evaluated during initial phases of hepatocarcinogenesis. Rats received 8 or 16 mg/100 g body wt GGO (GGO8 and GGO16 groups) or BI (BI8 and BI16 groups), or only corn oil (CO group, controls) daily for 7 weeks. Incidence (%) and the mean number of visible hepatocyte nodules/animal were inhibited in the GGO8 (64% and 21 +/- 40), GGO16 (33% and 3 +/- 5), BI8 (50% and 13 +/- 34) and BI16 (42% and 9 +/- 19) groups compared with the CO group (100% and 34 +/- 51) (P < 0.05, except for the GGO8 group). Number/cm(2) liver section, mean area (mm(2)) and % liver section area occupied by persistent hepatic placental glutathione S-transferase positive preneoplastic lesions (PNL) were reduced in the GGO8 (11 +/- 9; 0.26 +/- 0.35; 2.7 +/- 3.0), GGO16 (6 +/- 6; 0.18 +/- 0.16; 0.9 +/- 0.9), BI8 (9 +/- 5; 0.13 +/- 0.20; 1.1 +/- 1.2) and BI16 (8 +/- 6; 0.08 +/- 0.09; 0.6 +/- 0.4) groups compared with the CO group (26 +/- 18; 0.29 +/- 0.34; 7.0 +/- 5.5) (P < 0.05). GGO16 and BI16 groups showed smaller visible hepatocyte nodules, reduced PNL cell proliferation and total plasma cholesterol levels compared with the CO group (P < 0.05), but did not show any differences (P > 0.05) in PNL apoptosis. DNA damage expressed as comet length (microm) was reduced in the GGO8 (96.7 +/- 1.5), GGO16 (94.2 +/- 1.5), BI8 (97.1 +/- 1.1) and BI16 (95.1 +/- 1.5) groups compared with the CO group (102.1 +/- 1.7) (P < 0.05). In comparison with normal animals, the CO group animals showed increased (P < 0.05) nuclear levels of nuclear factor kappa B (NF-kappaB) p65 subunit in hepatic cells, which were decreased (P < 0.05) in the GGO16 group animals. Anticarcinogenic actions of these isoprenoids seem to follow a dose-response relationship. Results indicate that GGO and BI could be represented as promising chemopreventive agents against hepatocarcinogenesis. Inhibition of cell proliferation and DNA damage seems to be important for the anticarcinogenic actions of isoprenoids, while the inhibition of NF-kappaB activation seems to be specifically related to GGO actions.