Qiu-Dong Zhao

Tumor-associated macrophages promote cancer stem cell-like properties via transforming growth factor-beta1-induced epithelial–mesenchymal transition in hepatocellular carcinoma

Tumor-associated macrophages (TAMs), a crucial component of immune cells infiltrated in tumor microenvironment, have been found to be associated with progression and metastasis of hepatocellular carcinoma (HCC). In this study, we aimed to clarify the mechanism underlying the crosstalk between TAMs and cancer stem cells (CSCs) in HCC. Mouse macrophage cell line RAW264.7 cells were used to investigate the effects of TAMs on mouse hepatoma cell line Hepa1-6 cells in vivo and vitro. A total of 90 clinical samples had pathology-proven HCC were used to evaluate the distribution of TAMs and CSCs and analyze their value in predicting the prognosis. In the study, we have found that the number of TAMs has a positive correlation with the density of CSCs in the marginal of human HCC. Our results show that, cocultured with TAM-conditioned medium (CM) promoted CSC-like properties in Hepa1-6 cells, which underwent EMT and gained higher invasive capability. TAMs secreted more transforming growth factor- beta1 (TGF-beta1) than other phenotypes of macrophage. Furthermore, depletion of TGF-beta1 blocked acquisition of CSC-like properties by inhibition of TGF-beta1-induced EMT. High expression of CD68 in the EpCAM positive expression HCC tissues was strongly associated with both poor cancer-free survival and overall survival in patients. Our results indicate that the TAMs promote CSC-like properties via TGF-beta1-induced EMT and they may contribute to investigate the prognosis of HCC.

Effects of Inflammatory Factors on Mesenchymal Stem Cells and Their Role in the Promotion of Tumor Angiogenesis in Colon Cancer

Mesenchymal stem cells (MSCs), which are modulated by cytokines present in the tumor microenvironment, play an important role in tumor progression. It is well documented that inflammation is an important part of the tumor microenvironment, so we investigated whether stimulation of MSCs by inflammatory cytokines would contribute to their ability to promote tumor growth. We first showed that MSCs could increase C26 colon cancer growth in mice. This growth-promoting effect was further accelerated when the MSCs were pre-stimulated by inflammatory factors IFN-γ and TNF-α. At the same time, we demonstrated that MSCs pre-stimulated by both inflammatory factors could promote tumor angiogenesis in vivo to a greater degree than untreated MSCs or MSCs pre-stimulated by either IFN-γ or TNF-α alone. A hen egg test-chorioallantoic membrane (HET-CAM) assay showed that treatment of MSC-conditioned medium can promote chorioallantoic membrane angiogenesis in vitro, especially treatment with conditioned medium of MSCs pretreated with IFN-γ and TNF-α together. This mechanism of promoting angiogenesis appears to take place via an increase in the expression of vascular endothelial growth factor (VEGF), which itself takes place through an increase in signaling in the hypoxia-inducible factor 1α (HIF-1α)-dependent pathway. Inhibition of HIF-1α in MSCs by siRNA was found to effectively reduce the ability of MSC to affect the growth of colon cancer in vivo in the inflammatory microenviroment. These results indicate that MSCs stimulated by inflammatory cytokines such as IFN-γ and TNF-α in the tumor microenvironment express higher levels of VEGF via the HIF-1α signaling pathway and that these MSCs then enhance tumor angiogenesis, finally leading to colon cancer growth in mice.

Hypoxia-induced autophagy contributes to the chemoresistance of hepatocellular carcinoma cells.

Hypoxia commonly exists in solid tumors. In this adverse condition, adaptive responses including autophagy are usually provoked to promote cell survival. In our study, autophagy, a lysosomal-mediated degradation pathway, is demonstrated a protective way to make hepatocellular carcinoma cells be resistant to chemotherapy under hypoxia. Compared with normoxia, chemotherapeutic agents-induced cell death under hypoxia was significantly decreased, as a result of the reduced apoptosis. However, when autophagy was inhibited by 3-MA or siRNA targeted Beclin 1, this reduction was reversed i.e. chemoresistance was attenuated, which means autophagy mediates the chemoresistance under hypoxia. In conclusion, autophagy decreases hepatoma cells sensitization to chemotherapeutic agents by affecting their apoptotic potential.

Targeting autophagy potentiates chemotherapy-induced apoptosis and proliferation inhibition in hepatocarcinoma cells

Induction of cell death and inhibition of cell growth are the main targets of cancer therapy. Here we evaluated the role of autophagy on chemoresistance of human hepatocarcinoma (HCC) cell lines, focusing on its crosstalk with cell apoptosis and proliferation. In this study, a chemotherapeutic agent (cisplatin or 5FU) induced the formation of autophagosomes in three human HCC cell lines and upregulated the expression of autophagy protein LC3-II. Inhibition of autophagy by 3-methyladenine or si-beclin 1 increased chemotherapy-induced apoptosis in HCC cells. Meanwhile, increased damage of the mitochondrial membrane potential was also observed in HCC cells when autophagy was inhibited. Furthermore, inhibition of autophagy reduced clone formation and impaired cell growth of HCC cells when treated with chemotherapy. Co-administration of an autophagy inhibitor (chloroquine) and chemotherapy significantly inhibited tumor growth in a mouse xenograft tumor model, with greater extent of apoptosis and impaired proliferation of tumor cells. This study suggests that autophagy is a potential novel target to improve therapy efficiency of conventional chemotherapeutics towards HCC.

Toll-like receptor 4 signaling promotes epithelial-mesenchymal transition in human hepatocellular carcinoma induced by lipopolysaccharide

BackgroundThe endotoxin level in the portal and peripheral veins of hepatocellular carcinoma (HCC) patients is higher and lipopolysaccharide (LPS), a cell wall constituent of gram-negative bacteria, has been reported to inhibit tumor growth. However, in this study, we found that LPS-induced toll-like receptor 4 (TLR4) signaling was involved in tumor invasion and survival, and the molecular mechanism was investigated,MethodsFour HCC cell lines and a splenic vein metastasis of the nude mouse model were used to study the invasion ability of LPS-induced HCC cells and the epithelia-mesenchymal transition (EMT) in vitro and in vivo. A total of 106 clinical samples from HCC patients were used to evaluate TLR4 expression and analyze its association with clinicopathological characteristicsResultsThe invitro and in vivo experiments demonstrated that LPS could significantly enhance the invasive potential and induce EMT in HCC cells with TLR4 dependent. Further studies showed that LPS could directly activate nuclear factor kappa B (NF-κB) signaling through TLR4 in HCC cells. Interestingly, blocking NF-κB signaling significantly inhibited transcription factor Snail expression and thereby inhibited EMT occurrence. High expression of TLR4 in HCC tissues was strongly associated with both poor cancer-free survival and overall survival in patients.ConclusionsOur results indicate that TLR4 signaling is required for LPS-induced EMT, tumor cell invasion and metastasis, which provide molecular insights for LPS-related pathogenesis and a basis for developing new strategies against metastasis in HCC.

Autophagy contributes to the survival of CD133+ liver cancer stem cells in the hypoxic and nutrient-deprived tumor microenvironment.

Liver cancer stem cells (LCSCs) can drive and maintain hepatocellular carcinoma (HCC) growth, metastasis, and recurrence. Therefore, they are potentially responsible for the poor prognosis of HCC. Oxygen and nutrient deficiencies are common characteristics of the tumor microenvironment. However, how LCSCs adapt to oxygen- and nutrient-deprived conditions is unclear. Here, we used immunofluorescent staining and flow cytometry analysis to show that CD133+ cells were significantly enriched after hypoxia and nutrient starvation (H/S) in the human HCC cell line Huh7. Sorted CD133+ cells showed higher survival, less apoptosis, and possess higher clonogenic ability under H/S compared to the CD133- population. Under H/S, electron microscopy revealed more advanced autophagic vesicles in CD133+ cells. Additionally, CD133+ cells had higher autophagy levels as measured by both RT-qPCR and Western blotting. CD133+ cells had more accumulated GFP-LC3 puncta, which can be detected by fluorescence microscopy. The autophagic inhibitor chloroquine (CQ) significantly increased apoptosis and decreased the clonogenic capacity of CD133+ cells under H/S. Pre-culturing in H/S enhanced the sphere-forming capacity of CD133+ cells. However, CQ significantly impaired this process. Therefore, autophagy is essential for LCSCs maintenance. CD133+ cells were also found to have a higher tumor-forming ability in vivo, which could be inhibited by CQ administration. Collectively, our results indicate that the involvement of autophagy in maintenance of CD133+ LCSCs under the oxygen- and nutrient-deprived conditions that are typical of the tumor microenvironment in HCC. Therefore, autophagy inhibitors may make LCSCs more sensitive to the tumor microenvironment and be useful in improving anti-cancer treatments.

Inhibition of autophagy enhances anticancer effects of bevacizumab in hepatocarcinoma

Angiogenesis inhibitors have long been considered desirable anticancer agents. However, it was found that many tumors could develop resistance to antiangiogenesis inhibitors. Antiangiogenic therapy results in metabolic stress. Autophagy is an important survival mechanism in cancer cells under metabolic stress; however, it remains unknown if autophagy contributes to antiangiogenesis resistance. In this study, we reported that bevacizumab treatment reduced the development of new blood vessels and inhibited cell growth in xenografts of hepatocellular carcinoma (HCC) tumors. Bevacizumab treatment also upregulated expression of the autophagy-related genes (Beclin1 and LC3) and increased autophagosome formation. Our in vitro studies demonstrated that autophagy inhibition significantly increased apoptosis of HCC cells during nutrient starvation or hypoxia. In addition, the combined treatment of an autophagy inhibitor and bevacizumab markedly inhibited the tumor growth of HCC xenografts, led to enhanced apoptosis, and impaired the proliferation of tumor cells compared with treatment with either drug alone. Furthermore, autophagy inhibition led to enhanced reactive oxygen species (ROS) generation in HCC cells exposed to nutrient starvation or hypoxia in vitro and increased DNA oxidative damage in vivo. Antioxidants reduced nutrient starvation or the hypoxia-induced cell death of HCC cells after autophagy inhibition. Our results suggest that autophagy modulates ROS generation and contributes to cell survival under metabolic stress. Therefore, autophagy inhibition may be a novel way of increasing the efficicacy of antiangiogenic agents in the treatment of HCC.

Toll like receptor 4 facilitates invasion and migration as a cancer stem cell marker in hepatocellular carcinoma

Cancer stem cells (CSCs) or tumor-initiating cells (TICs), a small subset of tumor cells, are involved in tumor initiation, progression, recurrence and metastasis. In human hepatocellular carcinoma (HCC), TICs are enriched with cell surface markers and play a key role in chemotherapy resistance, tumor invasion and migration. Toll like receptor 4 (TLR4), acting as a receptor for lipopolysaccharide (LPS), has been reported to be responsible for carcinogenesis, invasion, metastasis and cancer progression. In our study, two HCC cell lines and a splenic vein metastasis of the nude mouse model were used to study the invasive ability of TLR4 positive HCC cells in vitro and in vivo. Stem-like features were also detected in TLR4 positive HCC cells. A total of 88 clinical samples from HCC patients were used to evaluate the association of TLR4 and stem-cell marker expression, and the relationship between TLR4 expression and clinicopathological characteristics was analyzed. The in vitro and in vivo experiments indicated that TLR4 positive HCC cells displayed significantly enhanced invasion and migration, and stem-like properties were also detected in TLR4 positive HCC cells. Clinically, TLR4 expression levels were found to be significantly higher in HCC tissues with microvascular invasion. Additionally, high expression of TLR4 in HCC tissues was strongly associated with both early recurrence and poor survivals in patients. Our results indicated that there was a relationship between TLR4 expression and CSCs features, TLR4 may act as a CSC marker, prompting tumor invasion and migration, which contributes to the poor prognosis of HCC.

Background Progenitor Activation Is Associated With Recurrence After Hepatectomy of Combined Hepatocellular-Cholangiocarcinoma

Hepatic progenitor cells (HPC) play important roles in both liver regeneration and carcinogenesis. Combined hepatocellular‐cholangiocarcinoma (CHC), a malignant primary liver tumor with poor prognosis, is thought to be of HPC origin. However, the prognostic significance of this etiology is not well defined. Therefore, we retrospectively investigated the relationship of HPC‐related pathological features and long‐term outcome in patients with CHC in our department. In a cohort of 80 patients identified between 1997 and 2003, including 70 patients who underwent resection with curative intent, overall survival (OS) and disease‐free survival (DFS) were correlated with the proliferative activity of nontumor ductular reaction (DR) and the expression levels of HPC and biliary markers including α‐fetoprotein (AFP), keratin 7 (K7), keratin 19 (K19), oval cell (OV)‐6, epithelial cell adhesion molecule (EpCAM), and c‐Kit in both tumor and nontumor liver. We found that nontumor ductular reactions (DRs), specifically the proliferating cell nuclear antigen (PCNA) labeling index of the ductular reaction (PI‐DR), a surrogate for transit‐amplifying compartments, was an independent prognostic factor for both OS and DFS. By contrast, intratumoral expression of only one marker, absence of AFP, was associated with OS. PI‐DR was also independently associated with synchronous “multicentric occurrence” in hepatocellular carcinoma components, a feature of CHC that may predispose to metachronous multifocal tumorigenesis. Conclusion: Proliferative ductular reaction related to HPC activation is associated with recurrence of CHC. Background HPC activation is strongly associated with multifocal occurrence and related tumor recurrence, highlighting the critical role of background liver disease, a “field effect,” in the recurrence of CHC. (Hepatology 2012;56:1804–1816)

Overexpression of SIRT1 promotes metastasis through epithelial-mesenchymal transition in hepatocellular carcinoma

BackgroundSIRT1 is a member of the mammalian sirtuin family with the ability to deacetylate histone and nonhistone proteins. The correlation between SIRT1 expression and tumor metastasis in several types of cancer has aroused widespread concern. This study investigated SIRT1 expression and its prognostic value in hepatocellular carcinoma (HCC). The function of SIRT1 in hepatocarcinogenesis was further investigated in cell culture and mouse models.MethodsWestern blotting and immunohistochemistry were used to explore SIRT1 expression in HCC cell lines and primary HCC clinical specimens. The functions of SIRT1 in the migration and invasion in the HCC cell line were analyzed by infecting cells with adenovirus containing full-length SIRT1 or sh-RNA. The effect of SIRT1 on tumorigenicity in nude mice was also investigated.ResultsSIRT1 expression was significantly overexpressed in the tumor tissues and HCC cell lines. SIRT1 significantly promoted the ability of migration and invasion in HCC cells. In addition, experiments with a mouse model revealed that SIRT1 overexpression enhanced HCC tumor metastasis in vivo. Furthermore, we demonstrated that SIRT1 significantly enhanced the invasive and metastatic potential by inducing epithelial-mesenchymal transition in HCC cells. A clinicopathological analysis showed that SIRT1 expression was significantly correlated with tumor size, tumor number, and TNM staging. Kaplan–Meier survival curves revealed that positive SIRT1 expression was associated with poor prognosis in patients with HCC.ConclusionsOur data suggest that SIRT1 may play an important role in HCC progression and could be a potential molecular therapy target for HCC.