A review on the diagnosis and treatment of hepatocellular carcinoma with a focus on the role of Wnts and the dickkopf family of Wnt inhibitors

Vitamin D potentiates anti-tumor activity of 5-fluorouracil via modulating caspase-3 and TGF-β1 expression in hepatocellular carcinoma-induced in rats

We investigated the role of vitamin D (Vit D) alone and in combination with 5-fluorouracil (5-FU) in thioacetamide (TAA)-induced hepatocellular carcinoma (HCC) in rats. Fifty male Sprague-Dawley rats were randomized into a control group and 4 groups that received TAA (200 mg/kg, i.p.) twice per week for 16 weeks. These 4 groups were further divided as follows: HCC group; 5-FU group (75 mg/kg, i.p., once weekly for 3 weeks starting from the 12th week); Vit D group (200 IU/kg daily by oral tube for 16 weeks); and 5-FU + Vit D group (received the previously mentioned dosage regimens of 5-FU and Vit D). HCC was detected by histopathological changes in liver sections and the elevation of serum α-fetoprotein (AFP). Treatment with 5-FU + Vit D significantly decreased gene expression of nuclear factor erythroid 2-related factor 2 (NrF2) and transforming growth factor β1 (TGF-β1) at both the gene and protein level and serum AFP concentrations in comparison with their corresponding monotherapy. Moreover, 5-FU + Vit D treatment enhanced apoptosis by increasing caspase-3 gene and protein expression. Conclusively, Vit D enhances antitumor activity of 5-FU in an HCC-induced model and improves liver function of treated animals. Combination therapy in a TAA-induced HCC rat model was more effective than 5-FU or Vit D through the modulation of TGF-β1, caspase-3, and NrF2 expressions.

Paracrine and autocrine regulation of gene expression by Wnt-inhibitor Dickkopf in wild-type and mutant hepatocytes

Background

Cells are able to communicate and coordinate their function within tissues via secreted factors. Aberrant secretion by cancer cells can modulate this intercellular communication, in particular in highly organised tissues such as the liver. Hepatocytes, the major cell type of the liver, secrete Dickkopf (Dkk), which inhibits Wnt/ β-catenin signalling in an autocrine and paracrine manner. Consequently, Dkk modulates the expression of Wnt/ β-catenin target genes. We present a mathematical model that describes the autocrine and paracrine regulation of hepatic gene expression by Dkk under wild-type conditions as well as in the presence of mutant cells.

Results

Our spatial model describes the competition of Dkk and Wnt at receptor level, intra-cellular Wnt/ β-catenin signalling, and the regulation of target gene expression for 21 individual hepatocytes. Autocrine and paracrine regulation is mediated through a feedback mechanism via Dkk and Dkk diffusion along the porto-central axis. Along this axis an APC concentration gradient is modelled as experimentally detected in liver. Simulations of mutant cells demonstrate that already a single mutant cell increases overall Dkk concentration. The influence of the mutant cell on gene expression of surrounding wild-type hepatocytes is limited in magnitude and restricted to hepatocytes in close proximity. To explore the underlying molecular mechanisms, we perform a comprehensive analysis of the model parameters such as diffusion coefficient, mutation strength and feedback strength.

Conclusions

Our simulations show that Dkk concentration is elevated in the presence of a mutant cell. However, the impact of these elevated Dkk levels on wild-type hepatocytes is confined in space and magnitude. The combination of inter- and intracellular processes, such as Dkk feedback, diffusion and Wnt/ β-catenin signal transduction, allow wild-type hepatocytes to largely maintain their gene expression.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-017-0470-9) contains supplementary material, which is available to authorized users.

Blocking Wnt Secretion Reduces Growth of Hepatocellular Carcinoma Cell Lines Mostly Independent of β-Catenin Signaling

Aberrant activation of Wnt/β-catenin signaling plays a key role in the onset and development of hepatocellular carcinomas (HCC), with about half of them acquiring mutations in either CTNNB1 or AXIN1. However, it remains unclear whether these mutations impose sufficient β-catenin signaling or require upstream Wnt ligand activation for sustaining optimal growth, as previously suggested for colorectal cancers. Using a panel of nine HCC cell lines, we show that siRNA-mediated knockdown of β-catenin impairs growth of all these lines. Blocking Wnt secretion, by either treatment with the IWP12 porcupine inhibitor or knockdown of WLS, reduces growth of most of the lines. Unexpectedly, interfering with Wnt secretion does not clearly affect the level of β-catenin signaling in the majority of lines, suggesting that other mechanisms underlie the growth-suppressive effect. However, IWP12 treatment did not induce autophagy or endoplasmic reticulum (ER) stress, which may have resulted from the accumulation of Wnt ligands within the ER. Similar results were observed for colorectal cancer cell lines used for comparison in various assays. These results suggest that most colorectal and liver cancers with mutations in components of the β-catenin degradation complex do not strongly rely on extracellular Wnt ligand exposure to support optimal growth. In addition, our results also suggest that blocking Wnt secretion may aid in tumor suppression through alternative routes currently unappreciated.

Selective Cytotoxicity of 1,3,4-Thiadiazolium Mesoionic Derivatives on Hepatocarcinoma Cells (HepG2)

In this work, we evaluated the cytotoxicity of mesoionic 4-phenyl-5-(2-Y, 4-X or 4-X-cinnamoyl)-1,3,4-thiadiazolium-2-phenylamine chloride derivatives (MI-J: X=OH, Y=H; MI-D: X=NO2, Y=H; MI-4F: X=F, Y=H; MI-2,4diF: X=Y=F) on human hepatocellular carcinoma (HepG2), and non-tumor cells (rat hepatocytes) for comparison. MI-J, M-4F and MI-2,4diF reduced HepG2 viability by ~ 50% at 25 μM after 24-h treatment, whereas MI-D required a 50 μM concentration, as shown by 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. The cytotoxicity was confirmed with lactate dehydrogenase assay, of which activity was increased by 55, 24 and 16% for MI-J, MI-4F and MI-2,4diF respectively (at 25 μM after 24 h). To identify the death pathway related to cytotoxicity, the HepG2 cells treated by mesoionic compounds were labeled with both annexin V and PI, and analyzed by flow cytometry. All compounds increased the number of doubly-stained cells at 25 μM after 24 h: by 76% for MI-J, 25% for MI-4F and MI-2,4diF, and 11% for MI-D. It was also verified that increased DNA fragmentation occurred upon MI-J, MI-4F and MI-2,4diF treatments (by 12%, 9% and 8%, respectively, at 25 μM after 24 h). These compounds were only weakly, or not at all, transported by the main multidrug transporters, P-glycoprotein, ABCG2 and MRP1, and were able to slightly inhibit their drug-transport activity. It may be concluded that 1,3,4-thiadiazolium compounds, especially the hydroxy derivative MI-J, constitute promising candidates for future investigations on in-vivo treatment of hepatocellular carcinoma.

Preliminary mechanism on the methylation modification of Dkk-1 and Dkk-3 in hepatocellular carcinoma

Wnt/β-catenin signaling pathway, having a crucial role in regulating diverse cellular processes, can be a new therapeutic target in cancer. To investigate the role of Dkk-1 (Dickkopf-1) and Dkk-3 in tumors and cirrhoses of the liver tissue in hepatocellular carcinoma (HCC), tissues from 38 patients with HCC resections including 5 patients who underwent hemangioma surgery of adjacent tumor tissues at the same time were obtained. Tissues were divided into three groups (nonfibrosis, cirrhosis, and carcinoma) through hematoxylin-eosin (HE) staining. Methylation-specific polymerase chain reaction (PCR) (MSP) measured the methylation status, and reverse transcription-PCR tested the messenger RNA (mRNA) levels, and immunohistochemical analysis provided levels of protein expression. The methylation detection rate of Dkk-1 and Dkk-3 was the highest (P < 0.05) and the mRNA levels of Dkk-1 and Dkk-3 were the lowest (P < 0.05) in the carcinoma tissues. The mRNA levels of β-catenin were significantly higher in the carcinoma tissue than the other tissues (P < 0.05). The expression of Dkk-1 and Dkk-3 was significantly higher in the carcinoma tissues than the other tissues (P < 0.05); but the β-catenin expression was the highest (P < 0.05). Compared with the control, the mRNA levels of β-catenin in the Dkk-1 and Dkk-3 silencing cells increased 5.34 (P < 0.05) and 3.5 times (P > 0.05). After the interference of 5-aza-2'-deoxycytidine, the mRNA levels of Dkk-1 and Dkk-3 significantly increased 58.9 and 59.3 times (P < 0.0001), and the mRNA levels of β-catenin decreased 6.02 times (P < 0.05). In the process of HCC, the abnormal activity of Wnt/β-catenin signaling may be associated with the methylation of Dkk-1 and Dkk-3.