Inhibitory Effects of LOXL2 Knockdown On Cellular Functions of Liver Cancer Stem Cells

Background and aim: Lysyl oxidase-like 2 (LOXL2) plays a role in tumor microenvironment formation and metastasis of hepatocellular carcinoma (HCC), which has a high mortality burden. Liver cancer stem cells (LCSCs) are related with the major malignant phenotypes of HCC. The function of LOXL2 in regulation of LCSCs remains unknown.Methods: CD133+HepG2 and CD133+Hep3B cells were sorted by fluorescence-activated cell sorting (FACS) from two human hepatoblastoma cell lines. Spheroid formation, apoptosis, cell cycle, as well as transwell assays were performed upon LOXL2 knock down in CD133+HepG2 and CD133+Hep3B cells. Protein and mRNA levels were quantified by Western blotting, Immunofluorescence and real-time PCR. Results: Knockdown of LOXL2 decreased spheroid formation, migration and invasion (p < 0.05), also induced apoptosis (p < 0.05) and cell cycle arrest (p < 0.05) in CD133+HepG2 and CD133+Hep3B cells. Knockdown of LOXL2 effectively inhibited expression of the anti-apoptosis proteins baculoviral IAP repeat-containing 3 (BIRC3) and murine double minute 2 (MDM2) (p < 0.01), as well as autophagy marker microtubule-associated protein 1 light chain 3 B (LC3) and autophagy gene ATG5 in CD133+HepG2 and CD133+Hep3B cells (p < 0.01). Conclusions: The results revealed that LOXL2 inhibition could reduce the proliferation and expansion of LCSCs, making LOXL2 inhibitors an attractive and novel therapeutic strategy of HCC.

PCGF2 and PCGF4 Opposite Drive Stem-like Properties in Hepatocellular Carcinoma

Background: PCGF4 is highly expressed in liver cancer and can be used as a marker for liver cancer stem cells. However, PCGF2, a homologue of PCGF4, is not clear whether it is expressed in HCC, and whether it regulates the stemness of liver cancer stem cells.Methods: IHC and Western blot were used to detect the expression of PCGF2 and PCGF4 protein in human HCC tissues and cell lines. Flow cytometry and sphere formation were performed to detect the effect of PCGF2 or PCGF4 on the stem-like properties of liver cancer stem cells. Kaplan-Meier curves were conducted for OS and DFS. Cell viability was measured at the indicated time points using Cell Counting Kit-8. We performed KEGG analysis on these target genes through the cluster profiler package of the R language.Results: IHC results showed that PCGF2 was lower expressed in HCC, while PCGF4 was higher expressed in HCC compared with matched paracancerous, and this higher expression exhibited poor prognosis in HCC. Up regulation of PCGF2 was also accompanied with decreased stem-like properties and sphere formation in HCC cell lines. Interestingly, down regulating PCGF4 got the similar results as up regulating PCGF2. Furthermore, up regulating PCGF2 or down regulating PCGF4 cells performed more sensitivity to sorafenib. We also found that PCGF2 and PCGF4 oppositely regulated the drives stem-like properties by p38 MAPK signal pathway.Conclusion: PCGF2 was a novel negative regulator of LCSCs that inhibiting the stem cell population, reducing the sphere formation ability of liver cancer stem cells, and increasing the sensitivity of sorafenib by targeting p38 MAPK signaling. PCGF2 was supposed to be a novel therapeutic target for Liver cancer stem cell.

The inhibition of ABCB1/MDR1 or ABCG2/BCRP enables doxorubicin to eliminate liver cancer stem cells

Two ATP-binding cassette transporters, ABCB1/MDR1 and ABCG2/BCRP, are considered the most critical determinants for chemoresistance in hepatocellular carcinoma. However, their roles in the chemoresistance in liver cancer stem cells remain elusive. Here we explored the role of inhibition of MDR1 or ABCG2 in sensitizing liver cancer stem cells to doxorubicin, the most frequently used chemotherapeutic agent in treating liver cancer. We show that the inhibition of MDR1 or ABCG2 in Huh7 and PLC/PRF/5 cells using either pharmacological inhibitors or RNAi resulted in the elevated level of intracellular concentration of doxorubicin and the accompanied increased apoptosis as determined by confocal microscopy, high-performance liquid chromatography, flow cytometry, and annexin V assay. Notably, the inhibition of MDR1 or ABCG2 led to the reversal of the chemoresistance, as evident from the enhanced death of the chemoresistant liver cancer stem cells in tumorsphere-forming assays. Thus, the elevation of effective intracellular concentration of doxorubicin via the inhibition of MDR1 or ABCG2 represents a promising future strategy that transforms doxorubicin from a traditional chemotherapy agent into a robust killer of liver cancer stem cells for patients undergoing transarterial chemoembolization.

Mutant MEG3 Enhances the Activity of Telomerase by Increasing DNA Damage Repair in Human Liver Cancer Stem Cells

Background: Long noncoding RNAs have recently considered as central regulators in diverse biological processes and emerged as vital players controlling tumorigenesis. Although wild MEG3 acts as a suppressor in several cancers, the function of mutant MEG3 is also unclear during tumorigenesis.Methods: Lentivalus infection,RT-PCR,Western blotting and tumorigenesis test in vitro and in vivo were performed.Results: our results suggest that mutant MEG3 promotes the growth of human liver cancer stem cells in vivo and in vitro.Mechanistically, our results show that mutant MEG3 enhances acetylation modification of HistoneH4 on K16.Then, mutant MEG3 enhances the expression of SETD2 dependent on H4K16Ac.Moreover, mutant MEG3 increases the DNA damage repair through SETD2.Ultimately, mutant MEG3 increases the telomeras activity dependent on DNA damage repair.Strikingly,TERT determines the cancerous function of mutant MEG3 in liver cancer stem cells. Therefore, we shed light on the fact that targeting mutant MEG3 could be a viable approach for cancer treatment.Conclusions: these observations will play an important role in finding effective tumor treatment targets.