Regulators of liver cancer stem cells

Hepatocellular carcinoma(HCC)is a leading cause of cancer deaths.It is often detected at a stage when there are few therapeutic options.Liver cancer stem cells(LCSCs)are highly tumorigenic and resistant to chemotherapy and radiation therapy.Their presence in HCC is a major reason why HCC is difficult to treat.The development of LCSCs is regulated by a variety of factors.This review summarizes recent advances on the factors that regulate the development of LCSCs.Due to the importance of LCSCs in the development of HCC,a better understanding of how LCSCs are regulated will help to improve the treatments for HCC patients.

road to stemness in hepatocellular carcinoma

Carcinogenic process has been proposed to relay on the capacity to induce local tissue damage and proliferative repair. Liver has a great regeneration capacity and currently, most studies point towards the dominant role of hepatocytes in regeneration at all levels of liver damage. The most frequent liver cancer is hepatocellular carcinoma(HCC). Historical findings originally led to the idea that the cell of origin of HCC might be a progenitor cell. However, current linage tracing studies put the progenitor hypothesis of HCC origin into question. In agreement with their dominant role in liver regeneration, mature hepatocytes are emerging as the cell of origin of HCC, although, the specific hepatocyte subpopulation of origin is yet to be determined. The relationship between the cancer cell of origin(CCO) and cancer-propagating cells, known as hepatic cancer stem cell(HCSC) is unknown. It has been challenging to identify the definitive phenotypic marker of HCSC, probably due to the existence of different cancer stem cells(CSC) subpopulations with different functions within HCC. There is a dynamic interconversion among different CSCs, and between CSC and non-CSCs. Because of that, CSC-state is currently defined as a description of a highly adaptable and dynamic intrinsic property of tumor cells, instead of a static subpopulation of a tumor. Altered conditions could trigger the gain of stemness, some of them include: EMT-MET, epigenetics, microenvironment and selective stimulus such as chemotherapy. This CSC heterogeneity and dynamism makes them out reach from therapeutic protocols directed to a single target. A further avenue of research in this line will be to uncover mechanisms that trigger this interconversion of cell populations within tumors and target it.

Liver regeneration using decellularized splenic scaffold: a novel approach in tissue engineering

BACKGROUND： The potential application of decellularized liver scaffold for liver regeneration is limited by severe shortage of donor organs. Attempt of using heterograft scaffold is accompanied with high risks of zoonosis and immunological rejection. We proposed that the spleen, which procured more extensively than the liver, could be an ideal source of decellularized scaffold for liver regeneration. METHODS： After harvested from donor rat, the spleen was processed by 12-hour freezing/thawing ×2 cycles, then circulation perfusion of 0.02% trypsin and 3% Triton X-100 sequentially through the splenic artery for 32 hours in total to prepare decellularized scaffold. The structure and component characteristics of the scaffold were determined by hematoxylin and eosin and immumohistochemical staining, scanning electron microscope, DNA detection, porosity measurement, biocompatibility and cytocompatibility test. Recellularization of scaffold by 5×106 bone marrow mesenchymal stem cells（BMSCs） was carried out to preliminarily evaluate the feasibility of liver regeneration by BMSCs reseeding and differentiation in decellularized splenic scaffold.RESULTS： After decellularization, a translucent scaffold, which retained the gross shape of the spleen, was generated. Histological evaluation and residual DNA quantitation revealed the remaining of extracellular matrix without nucleus and cytoplasm residue. Immunohistochemical study proved the existence of collagens I, IV, fibronectin, laminin and elastin in decellularized splenic scaffold, which showed a similarity with decellularized liver. A scanning electron microscope presented the remaining three-dimensional porous structure of extracellular matrix and small blood vessels. The poros-ity of scaffold, aperture of 45.36±4.87 μm and pore rate of 80.14%±2.99% was suitable for cell engraftment. Subcutaneous implantation of decellularized scaffold presented good histocompatibility, and recellularization of the splenic scaffold demonstrated that BMSCs could locate and survive in the decellularized matrix. CONCLUSION： Considering the more extensive organ source and satisfying biocompatibility, the present study indicated that the three-dimensional decellularized splenic scaffold might have considerable potential for liver regeneration when combined with BMSCs reseeding and differentiation.

COL14A1 promotes self-renewal of human liver cancer stem cells through activation of ERK signaling

Objective:Liver cancer stem cells(CSCs)are the culprits of hepatocellular carcinoma metastasis and recurrence.Only by eliminating tumor stem cells can malignant tumors be fundamentally cured.This study aimed to identify the role and underlying mechanism of aberrant Collagen Type XIV Alpha 1 Chain(COL14A1)overexpression in liver CSCs,and improve understanding of the molecular basis of hepatocellular carcinoma metastasis and recurrence.Methods:First,quantitative real-time polymerase chain reaction was used to confirm aberrant high-expression of COL14A1 in liver CSCs.Next,interference experiments were performed to determine the key role of COL14A1.To explore the mechanism of COL14A1 overexpression in liver CSCs,putative microRNA(miRNAs)targeting COL14A1 were analyzed using the miRTarBase database.Next,quantitative real-time polymerase chain reaction,western blotting,and luciferase reporter assays were performed to verify the interaction between miR-7108-3p and COL14A1.Lastly,key target proteins of the COL14A1-extracellular-regulated signal kinase(ERK)signaling pathway were identified through western blotting analysis.This study was approved by the Ethics Committee of Shanghai Fourth People’s Hospital,Tongji University School of Medicine,China(approval No.2019tjdx17)on February 21,2019.Results:COL14A1 is abnormally highly expressed in liver CSCs,which is necessary for liver CSCs to maintain their self-renewal capability.Mechanistically,COL14A1 is post-transcriptionally regulated by miR-7108-3p in a negative manner.Low expression of miR-7108-3p increased translation of COL14A1,which subsequently activated ERK signaling,ultimately maintaining the self-renewal and stem cell-like properties of liver CSCs.Conclusion:COL14A1,which is negatively regulated by miR-7108-3p,was found to play a crucial role in maintaining the selfrenewal and stem cell-like properties of liver CSCs through activation of ERK signaling.

Microenvironment of Liver Regeneration in Liver Cancer

The occurrence and development of liver cancer are essentially the most serious outcomes of uncontrolled liver regeneration. The progression of liver cancer is inevitably related to the abnormal microenvironment of liver regeneration. The deterioration observed in the microenvironment of liver regeneration is a necessary condition for the occurrence, development and metastasis of cancer. Therefore, the use of a technique to prevent and treat liver cancer via changes in the microenvironment of liver regeneration is a novel strategy. This strategy would be an effective way to delay, prevent or even reverse cancer occurrence, development and metastasis through an improvement in the liver regeneration microenvironment along with the integrated regulation of multiple components, targets, levels, channels and time sequences. In addition, the treatment of ＂tonifying Shen（Kidney） to regulate liver regeneration and repair by affecting stem cells and their microenvironment＂ can regulate ＂the dynamic imbalance between the normal liver regeneration and the abnormal liver regeneration＂; this would improve the microenvironment of liver regeneration, which is also a mechanism by which liver cancer may be prevented or treated.

Role of Liver Progenitor Cell in Liver Regeneration Cellular Cross-Talks and Signals

The liver is well known for its ability to regenerate in response to injury. After partial hepatectomy and some chemicals induced acute liver injury, existing hepatocytes can expand to repair the liver function. While adult liver stem/progenitor cells(LPCs) are evoked and differentiate into functional hepatocytes and cholangiocytes to compensate the damaged liver once hepatocyte proliferation is severely impaired. A number of evidences suggest that adjacent hepatic stellate cells(HSCs) or invading leukocytes may be involved in LPCs directed regeneration through governning two major events including fibrogenic and inflammatory responses respectively or simultaneously. As such, a microenvironment(or "niche") composed of different cell sources or factors presents diversity, which eventually mediates LPCs response to biliary or hepatocellular regeneration. This mini review aims at summarizing the latest development on the roles of HSCs, macrophages and lymphocytes as well as corresponding signaling pathways in liver progenitor cells mediated biliary and hepatocellular regeneration, and discussing therapeutic potential of liver progenitor cells in hepatic diseases.