An Atypical System for Studying Epithelial-Mesenchymal Transition in Hepatocellular Carcinoma

Melatonin modulates the Warburg effect and alters the morphology of hepatocellular carcinoma cell line resulting in reduced viability and migratory potential

AIMS

Hepatocellular Carcinoma (HCC) is a primary neoplasm derived from hepatocytes with low responsiveness and recurrent chemoresistance. Melatonin is an alternative agent that may be helpful in treating HCC. We aimed to study in HuH 7.5 cells whether melatonin treatment exerts antitumor effects and, if so, what cellular responses are induced and involved.

MAIN METHODS

We evaluated the effects of melatonin on cell cytotoxicity and proliferation, colony formation, morphological and immunohistochemical aspects, and on glucose consumption and lactate release.

KEY FINDINGS

Melatonin reduced cell motility and caused lamellar breakdown, membrane damage, and reduction in microvillus. Immunofluorescence analysis revealed that melatonin reduced TGF and N-cadherin expression, which was further associated with inhibition of epithelial-mesenchymal transition process. In relation to the Warburg-type metabolism, melatonin reduced glucose uptake and lactate production by modulating intracellular lactate dehydrogenase activity.

SIGNIFICANCE

Our results indicate that melatonin can act upon pyruvate/lactate metabolism, preventing the Warburg effect, which may reflect in the cell architecture. We demonstrated the direct cytotoxic and antiproliferative effect of melatonin on the HuH 7.5 cell line, and suggest that melatonin is a promising candidate to be further tested as an adjuvant to antitumor drugs for HCC treatment.

Downregulation of PDGF-D Inhibits Proliferation and Invasion in Breast Cancer MDA-MB-231 Cells

BACKGROUND

The platelet derived growth factor-D (PDGF-D) plays an important role in breast tumor aggressiveness. However, limited study has investigated the effect of silencing PDGF-D on the biological function of breast cancer. The purpose of this study is to clarify the potential value of PDGF-D as a target for breast cancer treatment.

METHODS

Reverse transcription-polymerase chain reaction and western blot were used to detect PDGF-D expression in 5 different breast cancer cells. The lentiviral vector was usd to silence PDGF-D in MDA-MB-231 cells. Then, Methyl Thiazolyl Tetrazolium was used to detect cell viability, 5-Ethynyl-2'- deoxyuridine and a soft agar assay were used to detect cell proliferation and clonality. Additionally, cell apoptosis after PDGF-D knockdown was measured by Annexin V/ Prodium Iodide staining, and cell migration was detected by trans-well assay. Survival rate and tumor size were measured by nude mice transplantation.

RESULTS

The MDA-MB-231 and SK-BR-3 cell lines showed higher PDGF-D expression than the MCF7 cell lines (P<.05). After the PDGF-D gene was silenced, the growth and colony forming abilitys ignificantly decreased (P<.05) together with the induction of apoptosis in MDA-MB-231 cells (P<.05). Moreover, MDA-MB-231 cells with PDGF-D silencing showed significantly diminished aggressive migration and invasion potential compared to other cells (P<.05). In vivo experiments also indicated that PDGF-D silencing inhibited tumor growth and improved the survival rate of tumor-bearing mice.

CONCLUSION

Downregulation of PDGF-D had dramatic effects on breast cancer cell proliferation, apoptosis and migration, which indicates that it plays an important role in breast cancer development and progression.

Endothelial Cell-Derived TGF-β Promotes Epithelial-Mesenchymal Transition via CD133 in HBx-Infected Hepatoma Cells

Background: Hepatitis B-X Protein (HBx) encoded in Hepatitis B virus (HBV) is known to play a critical role in development and progression of HBV induced hepatocellular carcinoma (HCC). HBx interacts with and activates various cells in HCC microenvironment to promote tumor initiation, progression and invasion. In this study, we investigated how surrounding stromal cells interact with HBx-infected hepatoma cells by a series of in vitro co-culture studies. Methods: Huh7 hepatoma cells were cultured and transfected with the mammalian expression vector pGFP-HBx. Co-culture assays were performed between HBx-transfected Huh7 cells and conditioned media (CM) from stromal cells [endothelial cell lines (HUVECs) and hepatic stellate cell lines (LX2 cells)]. The effect of these interactions was studied by a series of functional assays like chemotaxis, invasion, and wound healing scratch assays. Also, quantitative real time (RT)-PCRs of the mesenchymal genes was performed in the hepatoma cells with and without the co-cultures. Hep3B cells with an integrated HBV genome were taken as positive controls. Results: HBx-transfected Huh7 cells cultured in presence of CM from HUVECs illustrated enhanced migration and tube formation as compared to HBx-transfected cells cultured alone or co-cultured with LX2 cells. HBx-transfected hepatoma cells incubated with CM from HUVECs also expressed mesenchymal genes including Thy1, CDH2, TGFβR1, VIM, and CD133. ELISAs revealed increased levels of TGF-β in CM from HUVECs. In comparison to unstimulated HBx-transfected Huh7 cells, TGF-β stimulated cells displayed increased invasive properties and mesenchymal gene expression. RT-PCR and flow cytometry analysis further demonstrated that incubation with either CM from HUVECs or TGF-β significantly increased the expression of a stemness marker, CD133 in HBx-infected hepatoma cells. Gene inhibition experiments with CD133 siRNA showed a downregulation of mesenchymal gene expression and properties in TGF-β induced HBx-infected hepatoma cells as compared to that observed in control siRNA treated cells, indicating CD133 as one of the key molecules affecting epithelial to mesenchymal transition (EMT) in HBx-infected cells. Conclusion: The study indicates that secretory factors like TGF-β from neighboring endothelial cells may enhance expression of CD133 and impart an aggressive EMT phenotype to HBx-infected hepatoma cells in HBV induced HCC.

Clinical significance of C/D box small nucleolar RNA U76 as an oncogene and a prognostic biomarker in hepatocellular carcinoma

BACKGROUND

Recent evidence has suggested novel roles of small nucleolar RNAs (snoRNAs) in tumorigenicity. However, the roles of C/D box snoRNA U76 (SNORD76) in the development of hepatocellular carcinoma (HCC) remain unknown. Herein, we systematically evaluated dysregulation of snoRNAs in HCC and clarified the biomarker potential and biological significance of SNORD76 in HCC.

METHODS

We performed quantitative analyses of the expression of SNORD76 in 66 HCC specimens to compare its expression pattern between tumor tissue and matched non-tumor tissue. The effects of SNORD76 on HCC tumorigenicity were investigated in SK-Hep1 and Huh7 cells as well as in a xenograft nude mouse model.

RESULTS

SNORD76 expression was significantly upregulated in HCC tissues compared to corresponding non-tumor tissues. This upregulation of SNORD76 in HCC tumors was significantly associated with poorer patient survival. Furthermore, inhibiting SNORD76 expression suppressed cell proliferation by inducing G0/G1 cell cycle arrest and apoptosis. Low SNORD76 expression also resulted in decreased HCC growth in an animal model. Conversely, overexpressing SNORD76 promoted cell proliferation. SNORD76 increased HCC cell invasion by inducing epithelial-mesenchymal transition (EMT). Finally, we found that SNORD76 promoted HCC tumorigenicity through activation of the Wnt/β-catenin pathway.

CONCLUSIONS

Therefore, we demonstrated for the first time that SNORD76 may function as a novel tumor promoter in HCC and may serve as a promising prognostic biomarker in patients with HCC.

Unconventional MAPK-GSK-3β Pathway Behind Atypical Epithelial-Mesenchymal Transition In Hepatocellular Carcinoma

We recently reported an atypical epithelial mesenchymal transition (EMT) in human hepatoma cell culture Huh7.5, which was non-responsive to the canonical EMT-transcription factors. Here we characterize major pathways regulating this atypical EMT through whole genome transcriptome profiling and molecular analysis, and identify a unique regulation of EMT by GSK-3β. Our analysis reveals remarkable suppression of several key liver-specific markers in Huh7.5M cells indicating that EMT not only changes the epithelial properties, but alters the characteristics associated with hepatocytes as well. One key finding of this study is that GSK-3β, a known antagonist to β-Catenin signaling and a major pro-apoptotic regulator, is critical for the maintenance of EMT in Huh7.5M cells as its inhibition reversed EMT. Importantly, through these studies we identify that maintenance of EMT by GSK-3β in Huh7.5M is regulated by p38MAPK and ERK1/2 that has not been reported elsewhere and is distinct from another metastatic non-hepatic cell line MDA-MB-231. These data showcase the existence of non-canonical mechanisms behind EMT. The atypicalness of this system underlines the existence of tremendous diversity in cancer-EMT and warrants the necessity to take a measured approach while dealing with metastasis and cancer drug resistance.