Arsenic trioxide induces differentiation of CD133+ hepatocellular carcinoma cells and prolongs posthepatectomy survival by targeting GLI1 expression in a mouse model

Can arsenic do anything good? Arsenic nanodrugs in the fight against cancer - last decade review

Arsenic has been an element of great interest among scientists for many years as it is a widespread metalloid in our ecosystem. Arsenic is mostly recognized with negative connotations due to its toxicity. Surely, most of us know that a long time ago, arsenic trioxide was used in medicine to treat, mainly, skin diseases. However, not everyone knows about its very wide and promising use in the treatment of cancer. Initially, in the seventies, it was used to treat leukemia, but new technological possibilities and the development of nanotechnology have made it possible to use arsenic trioxide for the treatment of solid tumours. The most toxic arsenic compound - arsenic trioxide - as the basis of anticancer drugs in which they function as a component of nanoparticles is used in the fight against various types of cancer. This review aims to present the current solutions in various cancer treatment using arsenic compounds with different binding motifs and methods of preparation to create targeted nanoparticles, nanodiamonds, nanohybrids, nanodrugs, or nanovehicles.

Extirpating the cancer stem cell hydra: Differentiation therapy and Hyperthermia therapy for targeting the cancer stem cell hierarchy

Ever since the discovery of cancer stem cells (CSCs), they have progressively attracted more attention as a therapeutic target. Like the mythical hydra, this subpopulation of cells seems to contribute to cancer immortality, spawning more cells each time that some components of the cancer cell hierarchy are destroyed. Traditional modalities focusing on cancer treatment have emphasized apoptosis as a route to eliminate the tumor burden. A major problem is that cancer cells are often in varying degrees of dedifferentiation contributing to what is known as the CSCs hierarchy and cells which are known to be resistant to conventional therapy. Differentiation therapy is an experimental therapeutic modality aimed at the conversion of malignant phenotype to a more benign one. Hyperthermia therapy (HT) is a modality exploiting the changes induced in cells by the application of heat produced to aid in cancer therapy. While differentiation therapy has been successfully employed in the treatment of acute myeloid leukemia, it has not been hugely successful for other cancer types. Mounting evidence suggests that hyperthermia therapy may greatly augment the effects of differentiation therapy while simultaneously overcoming many of the hard-to-treat facets of recurrent tumors. This review summarizes the progress made so far in integrating hyperthermia therapy with existing modules of differentiation therapy. The focus is on studies related to the successful application of both hyperthermia and differentiation therapy when used alone or in conjunction for hard-to-treat cancer cell niche with emphasis on combined approaches to target the CSCs hierarchy.

The tumor microenvironment in the postsurgical liver: Mechanisms and potential targets of postoperative recurrence in human hepatocellular carcinoma

Surgery remains to be the mainstay of treatment for hepatocellular carcinoma (HCC). Nonetheless, its therapeutic efficacy is significantly impaired by postoperative recurrence, which occurs in more than half of cases as a result of intrahepatic metastasis or de novo tumorigenesis. For decades, most therapeutic strategies on inhibiting postoperative HCC recurrence have been focused on the residual tumor cells but satisfying therapeutic outcomes are barely observed in the clinic. In recent years, a better understanding of tumor biology allows us to shift our focus from tumor cells toward the postoperative tumor microenvironment (TME), which is gradually identified to play a pivotal role in tumor recurrence. In this review, we describe various surgical stress and surgical perturbation on postoperative TME. Besides, we discuss how such alternations in TME give rise to postoperative recurrence of HCC. Based on its clinical significance, we additionally highlight the potential of the postoperative TME as a target for postoperative adjuvant therapeutics.

Hepatogenesis and hepatocarcinogenesis: Alignment of the main signaling pathways

Development is a symphony of cells differentiation in which different signaling pathways are orchestrated at specific times and periods to form mature and functional cells from undifferentiated cells. The similarity of the gene expression profile in malignant and undifferentiated cells is an interesting topic that has been proposed for many years and gave rise to the differentiation-therapy concept, which appears a rational insight and should be reconsidered. Hepatocellular carcinoma (HCC), as the sixth common cancer and the third leading cause of cancer death worldwide, is one of the health-threatening complications in communities where hepatotropic viruses are endemic. Sedentary lifestyle and high intake of calories are other risk factors. HCC is a complex condition in which various dimensions must be addressed, including heterogeneity of cells in the tumor mass, high invasiveness, and underlying diseases that limit the treatment options. Under these restrictions, recognizing, and targeting common signaling pathways during liver development and HCC could expedite to a rational therapeutic approach, reprograming malignant cells to well-differentiated ones in a functional state. Accordingly, in this review, we highlighted the commonalities of signaling pathways in hepatogenesis and hepatocarcinogenesis, and comprised an update on the current status of targeting these pathways in laboratory studies and clinical trials.

Transarterial chemoembolization (TACE) plus apatinib-combined therapy versus TACE alone in the treatment of intermediate to advanced hepatocellular carcinoma patients: A real-world study

BACKGROUND

Apatinib exhibits the synergistic effect with transarterial chemoembolization (TACE) though inhibiting the neoangiogenetic reaction caused by TACE. In this real-world study, we aimed to evaluate the efficacy and safety of TACE plus apatinib-combined therapy (ACT) in intermediate to advanced hepatocellular carcinoma (HCC) patients.

METHODS

Data from 168 intermediate to advanced HCC patients who received TACE alone (N = 49) or TACE plus ACT (N = 119) were extracted. Besides, ACT was defined as apatinib with or without other therapy, such as arsenic trioxide, microwave ablation and radioactive seed implantation.

RESULTS

In TACE plus ACT group, the median overall survival (OS) was 30 months (95% confidence interval (CI): 24-40 months) with 1-year, 3-year and 5-year OS rate of 84.0%, 41.2% and 21.5%, respectively. While in TACE group, the median OS was only 14 months (95%CI: 11-17 months) with 1-year, 3-year and 5-year OS rate of 55.1%, 18.4% and 16.1%, separately. By comparation, the OS was prolonged in TACE plus ACT group compared with TACE group (P<0.001). After adjusted by multivariate Cox's regression analysis, TACE plus ACT (vs. TACE) independently related to the longer OS (hazard ratio: 0.504, P = 0.001). In TACE plus ACT group, the most frequent adverse events included hand-foot syndrome (95.8%), hypertension (95.8%), fatigue (90.8%), albuminuria (85.7%), anorexia (79.0%), diarrhea (66.4%), myelosuppression (58.8%), nausea/vomiting (49.6%) and abdominal pain (39.5%), besides, no grade 4 adverse events and treatment-related death occurred.

CONCLUSION

TACE plus ACT is a promising treatment choice for the intermediate to advanced HCC patients.

Hepatocellular Carcinoma Differentiation: Research Progress in Mechanism and Treatment

Hepatocellular carcinoma (HCC) is the most common primary malignant tumor of the liver. Although progress has been made in diagnosis and treatment, morbidity and mortality continue to rise. Chronic liver disease and liver cirrhosis are still the most important risk factors for liver cancer. Although there are many treatments, it can only be cured by orthotopic liver transplantation (OLT) or surgical resection. And the worse the degree of differentiation, the worse the prognosis of patients with liver cancer. Then it can be considered that restoring a better state of differentiation may improve the prognosis. The differentiation treatment of liver cancer is to reverse the dedifferentiation process of hepatocytes to liver cancer cells by means of drugs, improve the differentiation state of the tumor, and restore the normal liver characteristics, so as to improve the prognosis. Understanding the mechanism of dedifferentiation of liver cancer can provide ideas for drug design. Liver enrichment of transcription factors, imbalance of signal pathway and changes of tumor microenvironment can promote the occurrence and development of liver cancer, and restoring its normal level can inhibit the malignant behavior of tumor. At present, some drugs have been proved to be effective, but more clinical data are needed to support the effectiveness and reliability of drugs. The differentiation treatment of liver cancer is expected to become an important part of the treatment of liver cancer in the future.

Metallomic profile in non-cirrhotic hepatocellular carcinoma supports a phenomenon of metal metabolism adaptation in tumor cells

We have previously described a form of hepatocellular carcinoma (HCC) in non-cirrhotic liver (HCC-NC) developed by Peruvian patients. We analyzed the metallomic profile in hepatic tissues from two independent cohorts exhibiting HCC-NC. Clinical, histopathological data, and HCC and non-tumoral liver (NTL) samples of 38 Peruvian and 38 French HCC-NC patients, were studied. Twelve metals were quantified using ICP/MS: Mn, Fe, Cu, Co, Zn, As, Se, Rb, Mo, Cd, Pb, and Sn. Associations between metals and survival were assessed. Our data showed significant differences between cohorts. Mean ages were 40.6 ± 20, 67.5 ± 9 years old for Peruvians and French, respectively. Fifty percent of the Peruvian patients were positive for the HBsAg, versus 3% in French patients. Mn, Cu, Zn, As, Se, Rb, Mo, Cd, Sn metal concentrations were higher in NTL of Peruvians. Importantly, metal concentrations were lower in HCC areas compared to NTL tissues in both cohorts, except for Cu for which mean concentration was higher in HCC (p < 0.05). Se concentration in HCC was associated with extended survival only in Peruvians. Our data, obtained in Peruvian and French HCC-NC cohorts, highlights similarity in the metallomic profile of HCC compared to NTL during the hepatic tumorigenesis in these specific groups of patients.

The role of CD133 in hepatocellular carcinoma

Cancer stem cells (CSCs) represent a small subpopulation of cells found within tumors that exhibit properties of self-renewal, like normal stem cells. CSCs have been defined as a crucial factor involved in driving cancer relapse, chemoresistance and metastasis. Prominin-1 (CD133) is one of the most well-characterized markers of CSCs in various tumor types, including hepatocellular carcinoma (HCC). CD133+ cells have been demonstrated to be involved in metastasis, tumorigenesis, tumor recurrence, and resistance to treatment in HCC. CD133-related clinical prognosis prediction, and targeted therapy have highlighted the clinical significance of CD133 in HCC. However, there remains controversy over the role of CD133 in experimental and clinical research involving HCC. In this article, we summarize the fundamental cell biology of CD133 in HCC cells and discuss the important characteristics of CD133+ in HCC cells. Furthermore, the prognostic value of CD133, and therapeutic strategies for its targeting in HCC, is also reviewed.

Arsenic trioxide induces differentiation of cancer stem cells in hepatocellular carcinoma through inhibition of LIF/JAK1/STAT3 and NF-kB signaling pathways synergistically

OBJECTIVE

Differentiation-inducing therapy for tumors is a strategy that aims to induce the differentiation and maturation of cancer stem cells (CSCs). The differentiation-inducing capacity of arsenic trioxide (ATO) in hepatocellular carcinoma (HCC) and the underlying mechanism were previously unknown.

METHODS

In the present study, we explored the ATO-induced differentiation of CSCs in HCC by detecting the expression of CSC-related markers and tumorigenicity variation in vivo and in vitro. We developed a combined chemotherapeutic approach to HCC by characterizing the effects of combinatorial treatment with 5-fluorouracil (5-FU)/cisplatin and ATO in vitro and in patient-derived xenograft models. Changes in gene expression patterns were investigated by gene microarray analysis.

RESULTS

ATO effectively induced differentiation of CSCs by downregulation of CSC-related genes and suppression of tumorigenicity capability. Combinatorial treatment with ATO and 5-FU/cisplatin significantly enhanced therapeutic effects in HCC cells compared with the treatment with 5-FU/cisplatin alone. Synergistic inhibition of the LIF/JAK1/STAT3 and NF-kB signaling pathways by ATO and 5-FU/cisplatin is a potential molecular mechanism underlying the differentiation effect.

CONCLUSIONS

ATO induced the differentiation of HCC CSCs and potentiated the cytotoxic effects of 5-FU/cisplatin through synergistic inhibition of the LIF/JAK1/STAT3 and NF-kB signaling pathways. These results offer new insights for the clinical treatment of HCC.

Zinc offers splenic protection through suppressing PERK/IRE1-driven apoptosis pathway in common carp (Cyprinus carpio) under arsenic stress

Arsenic (As) occurs naturally and concentrations in water bodies can reach high levels, leading to accumulation in vital organs like the spleen. Being an important organ in immune response and blood development processes, toxic effects of As on the spleen could compromise immunity and cause associated disorders in affected individuals. Splenic detoxification is key to improving the chances of survival but relatively little is known about the mechanisms involved. Essential trace elements like zinc have shown immune-modulatory effects humans and livestock. This study aimed to investigate the mechanisms involved in As-induced splenic toxicity in the common carp (Cyprinus carpio), and the protective effects of zinc (Zn). Our findings suggest that environmental exposure to As caused severe histological injuries and Ca²⁺ accumulation in the spleen of common carp. Additionally, transcriptional and translational profiles of endoplasmic reticulum stress, apoptosis and autophagy-related genes of the spleen showed upward trends under As toxicity. Treatment with Zn appears to offer protection against As-induced splenic injury in common carp and the pathologic changes above were alleviated. Our results provide additional insight into the mechanism of As toxicity in common carp while elucidating the role of Zn, a natural immune-modulator, as a potential antidote against As poisoning.

Arsenic trioxide inhibits the growth of cancer stem cells derived from small cell lung cancer by downregulating stem cell-maintenance factors and inducing apoptosis via the Hedgehog signaling blockade

Background

Small cell lung cancer (SCLC) is the most deadly and aggressive type of primary lung cancer, with the 5-year survival rate lower than 5%. The FDA has approved arsenic trioxide (As₂O₃) for acute promyelocytic leukemia (APL) treatment. However, its role in SCLC-derived cancer stem cells (CSCs) remains largely unknown.

Methods

CSCs were enriched from SCLC cell lines by culturing them as spheres in conditioned serum-free medium. Then, qPCR, western blot, serial passage, limiting dilution, Transwell, and tumorigenesis assay were performed to verify the cells' stem phenotypic characteristics. Anticancer efficiency of As₂O₃ was assessed in these cells using CCK8, colony formation, sphere formation, flow cytometry, qPCR, western blot analysis in vitro, and tumor growth curve, immunofluorescence, and TUNEL staining analyses in vivo.

Results

The fifth-passage SCLC spheres showed a potent self-renewal capacity, higher clonal formation efficiency (CFE), SOX2, c-Myc, NANOG, and OCT4 levels, and invasion ability, and stronger tumorigenesis capacity than the parental SCLC cells, indicating that the SCLC sphere cells displayed CSC features. As₂O₃ inhibited the proliferation, clonality and sphere forming ability of SCLC-derived CSCs and suppressed the tumor growth of CSCs-derived xenograft tumors. As₂O₃ induced apoptosis and downregulation of SOX2 and c-Myc in vitro and in xenografts. Besides, SOX2 knockdown suppressed SCLC-derived CSCs to self-renew and induced apoptosis. Mechanistically, expression of GLI1 (a key transcription factor of Hedgehog pathway) and its downstream genes increased in SCLC-derived CSCs, compared to the parental cells. As₂O₃ dramatically downregulated GLI1 and its downstream genes in vitro and in vivo. The GLI inhibitor (GANT-61) recapitulated and enhanced the effects of As₂O₃ on SCLC-derived CSCs, including growth suppression, apoptosis induction, and GLI1, SOX2 and c-Myc downregulation.

Conclusions

Altogether, As₂O₃ effectively suppressed SCLC-derived CSCs growth by downregulating stem cell-maintenance factors and inducing apoptosis. These effects are mediated at least partly via the Hedgehog signaling blockade.

Dedifferentiation of hepatocellular carcinoma: molecular mechanisms and therapeutic implications

Hepatocellular carcinoma (HCC) is a common cancer with high morbidity and mortality. Poorer differentiation status indicates worse prognosis of HCC patients. Regain of better differentiation status may improve the prognosis. Differentiation therapy for HCC is based on the fact that agents may reverse the dedifferentiation process from hepatocytes to HCC cells and thus improve tumor differentiation status. Reversal of progenitor-like property and restoration of hepatic characteristics are main objectives of HCC differentiation therapy. Comprehending the mechanisms of HCC dedifferentiation provides ideas for drug design. Diverse dysregulated molecules and signalings cooperatively cause HCC dedifferentiation. Dysregulation of liver enriched transcription factors, especially hepatocyte nuclear factor 4α, was a critical determinant of HCC dedifferentiation. Aberrant pivotal signaling molecules such as transforming factor-β, β-catenin and Yes-associated protein caused disordered signalings, which promoted HCC dedifferentiation. Loss of epithelial morphology during epithelial-mesenchymal transition (EMT) concurred with HCC dedifferentiation. Some EMT-related molecules exerted double-sided role in concurrently inducing EMT and HCC dedifferentiation. Besides, microRNAs (e.g. miR-122 and miR-148a) as well as some impressive proteins (i.e. KLF4, gankyrin and CHD1L) functioned in manipulating HCC differentiation status. Restoring normal expression levels of these molecules could induce HCC differentiation and inhibited malignant tumor behaviors. Based on the knowledge above, some agents have been found effective in lab, but need more data to support their reliability. Additionally, peretinoin as a potential drug is in progress of several phase III clinical trials. It's promising that differentiation therapy for HCC may be a part of options in future HCC treatment.

Safety and Tolerability of Sonic Hedgehog Pathway Inhibitors in Cancer

The hedgehog pathway, for which sonic hedgehog (Shh) is the most prominent ligand, is highly conserved and is tightly associated with embryonic development in a number of species. This pathway is also tightly associated with the development of several types of cancer, including basal cell carcinoma (BCC) and acute promyelocytic leukemia, among many others. Inactivating mutations in Patched-1 (PTCH1), leading to ligand-independent pathway activation, are frequent in several cancer types, but most prominent in BCC. This has led to the development of several compounds targeting this pathway as a cancer therapeutic. These compounds target the inducers of this pathway in Smoothened (SMO) and the GLI transcription factors, although targeting SMO has had the most success. Despite the many attempts at targeting this pathway, only three US FDA-approved drugs for cancers affect the Shh pathway. Two of these compounds, vismodegib and sonidegib, target SMO to suppress signaling from either PTCH1 or SMO mutations that lead to upregulation of the pathway. The other approved compound is arsenic trioxide, which can suppress this pathway at the level of the GLI proteins, although current evidence suggests it also has other targets. This review focuses on the safety and tolerability of these clinically approved drugs targeting the Shh pathway, along with a discussion on other Shh pathway inhibitors being developed.

Arsenic trioxide inhibits liver cancer stem cells and metastasis by targeting SRF/MCM7 complex

Hepatocellular carcinoma (HCC) has a high mortality rate due to the lack of effective treatments and drugs. Arsenic trioxide (ATO), which has been proved to successfully treat acute promyelocytic leukemia (APL), was recently reported to show therapeutic potential in solid tumors including HCC. However, its anticancer mechanisms in HCC still need further investigation. In this study, we demonstrated that ATO inhibits tumorigenesis and distant metastasis in mouse models, corresponding with a prolonged mice survival time. Also, ATO was found to significantly decrease the cancer stem cell (CSC)-associated traits. Minichromosome maintenance protein (MCM) 7 was further identified to be a potential target suppressed dramatically by ATO, of which protein expression is increased in patients and significantly correlated with tumor size, cellular differentiation, portal venous emboli, and poor patient survival. Moreover, MCM7 knockdown recapitulates the effects of ATO on CSCs and metastasis, while ectopic expression of MCM7 abolishes them. Mechanistically, our results suggested that ATO suppresses MCM7 transcription by targeting serum response factor (SRF)/MCM7 complex, which functions as an important transcriptional regulator modulating MCM7 expression. Taken together, our findings highlight the importance of ATO in the treatment of solid tumors. The identification of SRF/MCM7 complex as a target of ATO provides new insights into ATO’s mechanism, which may benefit the appropriate use of this agent in the treatment of HCC.

ZnAs@SiO2 nanoparticles as a potential anti-tumor drug for targeting stemness and epithelial-mesenchymal transition in hepatocellular carcinoma via SHP-1/JAK2/STAT3 signaling

Rationale: Current therapies for hepatocellular carcinoma (HCC) are hampered by treatment failure and recurrence due to the remaining treatment-resistant liver cancer stem cells (CSCs). Stemness and epithelial-mesenchymal transition (EMT) are regarded as two fundamental characteristics of liver CSCs necessary for cancer progression; thus, drugs that simultaneously target both characteristics should prove effective in eliminating HCC and impeding recurrence. In this study, we developed new arsenic trioxide (ATO)-based nanoparticles (NPs), which are expected to be more effective than the current HCC therapy, and explored their potential mechanism.

Methods: A “one-pot” reverse emulsification approach was employed to prepare the ZnAs@SiO₂ NPs. HCC cell lines, MHCC97L and Hep3b, were used to analyze the antitumor activity of ZnAs@SiO₂ NPs in vitro and in vivo by quantifying cell growth and metastasis as well as to study the effect on stemness and EMT. SHP-1 siRNA was used to validate the role of the SHP-1/JAK2/STAT3 signaling pathway in mediating inhibition of stemness and EMT by ZnAs@SiO₂.

Results: Compared with the current ATO treatment, ZnAs@SiO₂ NPs promoted apoptosis and significantly inhibited proliferation, migration, and invasion of both MHCC97L and Hep3b cells. In the in vivo assay, ZnAs@SiO₂ NPs inhibited tumor growth by 2.2-fold and metastasis by 3.5-fold as compared to ATO. The ZnAs@SiO₂ NPs also inhibited tumor spheroid formation in vitro and tumor initiation in vivo and induced significant changes in the expression of stemness markers (CD133, Sox-2, and Oct-4) and EMT markers (E-cadherin, Vimentin, and Slug) both in vitro and in vivo. These effects of ZnAs@SiO₂ that correlated with prognosis of HCC were mediated by the SHP-1/JAK2/STAT3 signaling.

Conclusions: ZnAs@SiO₂ NPs can effectively suppress tumor initiation, growth, metastasis, and inhibit stemness and EMT through regulation of SHP-1/JAK2/STAT3 signaling pathway in liver cancer cells in vitro and in vivo. Thus, ZnAs@SiO₂ NPs have immense potential for HCC treatment in the future.

Toxic effects of arsenic trioxide on Echinococcus granulosus protoscoleces through ROS production, and Ca2+-ER stress-dependent apoptosis

Cystic echinococcosis is a severe parasitic disease that commonly affects the liver and causes abscesses or rupture into the surrounding tissues, leading to multiple complications, such as shock, severe abdominal pain, and post-treatment abscess recurrence. Currently, there are no efficient measures to prevent these complications. We previously confirmed that arsenic trioxide (As2O3) exhibited in vitro cytotoxicity against Echinococcus granulosus protoscoleces. In the present study, we aimed to explore the mechanism of As2O3-induced E. granulosus protoscoleces apoptosis. After exposing E. granulosus protoscoleces to 0, 4, 6, and 8 μM As2O3, reactive oxygen species (ROS) level was detected by fluorescence microscopy; superoxide dismutase (SOD), and caspase-3 activities were measured; intracellular Ca2+ was detected by flow cytometry; GRP-78 and caspase-12 protein levels were measured by western blot analysis. Our results showed that the expression of caspase-3 was gradually increased and the expression of SOD was gradually decreased in As2O3-treated groups of protoscoleces. Simultaneously, fluorescence microscopy and flow cytometry showed that the ROS level and the intracellular Ca2+ level were increased in a time- and dose-dependent manner. Western blot analysis showed that the expressions of GRP-78 and caspase-12 were higher in As2O3-treated groups than in the control group. These results suggest that As2O3-induced apoptosis in E. granulosus protoscoleces is related to elevation of ROS level, disruption of intracellular Ca2+ homeostasis, and endoplasmic reticulum stress. These mechanisms can be targeted in the future by safer and more effective drugs to prevent recurrence of cystic echinococcosis.

Matrix stiffness-mediated effects on stemness characteristics occurring in HCC cells

Matrix stiffness as an important physical attribute of extracellular matrix exerts significant impacts on biological behaviors of cancer cells such as growth, proliferation, motility, metabolism and invasion. However, its influence on cancer stemness still remains elusive. Here, we explore whether matrix stiffness-mediated effects on stemness characteristics occur in HCC cells. As the substrate stiffness increased, HCC cells exhibited high proportion of cells with CD133(+)/EpCAM(+), high expression levels of CD133, EpCAM, Nanog and SOX2, greater self-renewing ability and oxaliplatin resistance. Simultaneously, their phosphorylation levels of Akt and mTOR, as well as p-4E-BP and SOX2 expressions were also obviously upregulated. Conversely, knockdown of integrin β1 partially attenuated higher stiffness-mediated stemness characteristics in HCC cells, and reversed the phosphorylation levels of Akt and mTOR, and expressions of p-4E-BP and SOX2, suggesting that integrin β1 may deliver higher stiffness signal into HCC cells and activate mTOR signaling pathway. Additionally, mTOR inhibitor suppressed the mTOR phosphorylation level and expression levels of p-4E-BP and SOX2 in HCC cells grown on higher stiffness substrate, as well as depressed their stemness properties significantly, favoring a regulating role of mTOR signaling pathway in matrix stiffness-mediated effects on stemness. In summary, matrix stiffness may be involved in the process of stemness regulation via activating integrin β1/Akt/mTOR/SOX2 signaling pathway. To the best of our knowledge, this study first reveals a novel regulating pathway to direct the stemness characteristics in HCC cells.

Antitumor activity and inhibitory effects on cancer stem cell-like properties of Adeno-associated virus (AAV) -mediated Bmi-1 interference driven by Bmi-1 promoter for gastric cancer

Bmi-1 is aberrantly activated in various cancers and plays a vital role in maintaining the self-renewal of stem cells. Our previous research revealed that Bmi-1 was overexpressed in gastric cancer (GC) and it's overexpression was an independent negative prognostic factor, suggesting it can be a therapeutic target. The main purpose of this investigation was to explore the antitumor activity of Bmi-1 interference driven by its own promoter (Ad-Bmi-1i) for GC. In this study, we used adenoviral vector to deliver Bmi-1 shRNA driven by its own promoter to treat GC. Our results revealed that Ad-Bmi-1i could selectively silence Bmi-1 in GC cells which overexpress Bmi-1 and suppress the malignant phenotypes and stem-like properties of GC cells in vitro and in vivo. Moreover, direct injection of Ad-Bmi-1i into xenografts suppressed tumor growth and destroyed cancer cells in vivo. Ad-Bmi-1i inhibited the proliferation of GC cells mainly via inducing senescence in vitro, but it suppressed tumor through inducing senescence and apoptosis, and inhibiting angiogenesis in vivo. Bmi-1 knockdown by Ad-Bmi-1i downregulated VEGF via inhibiting AKT activity. These results suggest that Ad-Bmi-1i not only inhibits tumor growth and stem cell-like phenotype by inducing cellular senescence directly, but also has an indirect anti-tumor activity by anti-angiogenesis effects via regulating PTEN/AKT/VEGF pathway. Transfer of gene interference guided by its own promoter by an adeno-associated virus (AAV) vector might be a potent antitumor approach for cancer therapy.

CD133 promotes gallbladder carcinoma cell migration through activating Akt phosphorylation

Gallbladder carcinoma (GBC) is the fifth most common malignancy of gastrointestinal tract. The prognosis of gallbladder carcinoma is extremely terrible partially due to metastasis. However, the mechanisms underlying gallbladder carcinoma metastasis remain largely unknown. CD133 is a widely used cancer stem cell marker including in gallbladder carcinoma. Here, we found that CD133 was highly expressed in gallbladder carcinoma as compared to normal tissues. CD133 was located in the invasive areas in gallbladder carcinoma. Down-regulation expression of CD133 inhibited migration and invasion of gallbladder carcinoma cell without obviously reducing cell proliferation. Mechanism analysis revealed that down-regulation expression of CD133 inhibited Akt phosphorylation and increased PTEN protein level. The inhibitory effect of CD133 down-regulation on gallbladder carcinoma cell migration could be rescued by Akt activation. Consistent with this, addition of Akt inhibitor Wortmannin markedly inhibited the migration ability of CD133-overexpressing cells. Thus, down-regulation of CD133 inhibits migration of gallbladder carcinoma cells through reducing Akt phosphorylation. These findings explore the fundamental biological aspect of CD133 in gallbladder carcinoma progression, providing insights into gallbladder carcinoma cell migration.

Identification of stem-like cells and clinical significance of candidate stem cell markers in gastric cancer

The existence of gastric cancer stem cells (CSCs) has not been definitively proven and specific cell surface markers for identifying gastric CSCs have largely not been identified. Our research aimed to isolate potential gastric CSCs and clarify their clinical significance, while defining markers for GCSC identification and verification. Here, we report that spheroid cells possess stem cell-like properties, and overexpress certain stem cell markers. CD133 or CD44-positive cells also exhibit properties of CSCs. The expression of Oct4, Sox2, Gli1, CD44, CD133, p-AKT, and p-ERK was significantly higher in metastatic lesions compared to that in primary lesions. Elevated expression of some of these proteins was correlated with a more aggressive phenotype and poorer prognosis, including Oct4, Sox2, Gli1, CD44, and p-ERK. Multivariate Cox proportional hazards model analysis showed that only CD44 is an independent factor. Knockdown of CD44 down-regulated the stem cell-like properties, which was accompanied by the down-regulation of p-ERK and Oct4. Oct4 overexpression could reverse the decreased CSCs properties induced by CD44 knockdown. Taken together, our research revealed that spheroid cell culture, and CD133 or CD44-labeled FACS methods can be used to isolate gastric CSCs. Some CSC markers have clinical significance in predicting the prognosis. CD44 is an independent prognostic factor and maintains the properties of CSCs in CD44-p-ERK-Oct4 positive feedback loop.

Approaches for targeting cancer stem cells drug resistance

INTRODUCTION

Several reports have suggested that a population of undifferentiated cells known as cancer stem cells (CSCs), is responsible for cancer formation and maintenance. In the last decade, the presence of CSCs in solid cancers have been reported. Areas covered: This review summarizes the main approaches for targeting CSCs drug resistance. It is indeed known that CSCs may contribute to resistance to conventional chemotherapy, radiotherapy and targeted agents. Among the mechanisms by which CSCs escape anticancer therapies, removal of therapeutic agents by drug efflux pumps, enhanced DNA damage repair, activation of mitogenic/anti-apoptotic pathways; the main features of CSCs, stemness and EMT, are involved, as well as the capability to evade immune response. Expert opinion: Different approaches are suitable to target CSCs mediated drug resistance. Some of them are currently under clinical evaluation in different cancer types. A better understanding of CSC biology, as well as more accurate study design, may maximize the therapeutic effects of these agents. In this respect, it is important to establish: (i) which molecules should be targeted; (ii) what drug combinations may be suitable; (iii) which patient settings will CSC targeting offer the highest clinical benefit; and (iv) how to integrate therapeutic approaches targeting CSCs with standard cancer therapy.

Arsenite inhibits the function of CD133+ CD13+ liver cancer stem cells by reducing PML and Oct4 protein expression

Cancer stem cells (CSCs) can form new tumors and contribute to post-operative recurrence and metastasis. We showed that CD133⁺CD13⁺ hepatocytes isolated from HuH7 cells and primary HCC cells display biochemical and functional characteristics typical of CSCs, suggesting that CD133⁺CD13⁺ hepatocytes in primary HCC tumors function as CSCs. We also found that arsenite treatment reduced the viability and stemness of CD133⁺CD13⁺ hepatocytes, enhanced the sensitivity of HuH7 cells to pirarubicin, and reduced the tumorigenicity of CD133⁺CD13⁺ hepatocytes xenografts in mice. The effects of sodium arsenite treatment in CD133⁺CD13⁺ hepatocytes were mediated by the post-transcriptional suppression of PML expression and the inhibition of Oct4, Sox2, and Klf4 expression at the transcriptional level. Incomplete rescue of Oct4 expression in arsenic-treated cells ectopically expressing an siRNA-resistant PML transcript suggested that OCT4 regulation in liver CSCs involves other factors in addition to PML. Our findings provide evidence of a specific role for PML in regulating Oct4 levels in liver CSCs and highlight the clinical importance of arsenic for improving the efficacy of other chemotherapeutic agents and the prevention of post-operative HCC recurrence and metastasis.

Anti-Cancer Stem-like Cell Compounds in Clinical Development - An Overview and Critical Appraisal

Cancer stem-like cells (CSC) represent a subpopulation of tumor cells with elevated tumor-initiating potential. Upon differentiation, they replenish the bulk of the tumor cell population. Enhanced tumor-forming capacity, resistance to antitumor drugs, and metastasis-forming potential are the hallmark traits of CSCs. Given these properties, it is not surprising that CSCs have become a therapeutic target of prime interest in drug discovery. In fact, over the last few years, an enormous number of articles describing compounds endowed with anti-CSC activities have been published. In the meanwhile, several of these compounds and also approaches that are not based on the use of pharmacologically active compounds (e.g., vaccination, radiotherapy) have progressed into clinical studies. This article gives an overview of these compounds, proposes a tentative classification, and describes their biological properties and their developmental stage. Eventually, we discuss the optimal clinical setting for these compounds, the need for biomarkers allowing patient selection, the redundancy of CSC signaling pathways and the utility of employing combinations of anti-CSC compounds and the therapeutic limitations posed by the plasticity of CSCs.

Metformin sensitizes sorafenib to inhibit postoperative recurrence and metastasis of hepatocellular carcinoma in orthotopic mouse models

Background

Sorafenib is recognized as a standard treatment for advanced hepatocellular carcinoma (HCC). However, many patients have to adopt dose reduction or terminate the use of sorafenib because of side effects. In addition, a large number of patients are resistant to sorafenib. Thus, it is essential to investigate the underlying mechanisms of the resistance to sorafenib and seek potential strategy to enhance its efficacy.

Methods

The protein expression of hypoxia-inducible factors (HIF)-2α, 30-kDa HIV Tat-interacting protein (TIP30), E-cadherin, N-cadherin, and pAMPK was detected by Western blot. Cell viability assays were performed to study the influence of metformin and sorafenib on cell proliferation. Annexin V-FITC apoptosis assays were used to detect the influence of metformin and sorafenib on cell apoptosis. The relationship between HIF-2α and TIP30 was studied using gene silencing approach and chromatin immunoprecipitation assay. To investigate the effect of metformin and sorafenib on postoperative recurrence and lung metastasis of HCC in tumor-bearing mice, the mice were orally treated either with metformin or sorafenib once a day for continuous 37 days after the operation to remove the lobe where the tumor was implanted. CD31, Ki67, and TUNEL were examined by immunohistochemistry.

Results

Our study demonstrated that metformin synergized with sorafenib reduced HIF-2α expression as examined by Western blot. Gene silencing approach indicated TIP30 was upregulated after knocking-down of HIF-2α and chromatin immunoprecipitation assay revealed that HIF-2α could bind to TIP30 promoter under hypoxic condition. Cell Counting Kit-8 (CCK8) cell viability assay and Annexin V-FITC apoptosis assay showed that metformin in combination with sorafenib suppressed cell proliferation and promoted cell apoptosis. Besides, combined therapy suppressed epithelial-mesenchymal transition (EMT) process both in vitro and in vivo. Moreover, metformin in combination with sorafenib significantly minimized postoperative recurrence and lung metastasis of HCC in orthotopic mouse model. Combined therapy inhibited CD31 and Ki67 expression but promoted TUNEL expression.

Conclusions

Metformin may potentially enhance the effect of sorafenib to inhibit HCC recurrence and metastasis after liver resection by regulating the expression of HIF-2α and TIP30.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-016-0253-6) contains supplementary material, which is available to authorized users.

Arsenic trioxide inhibits cancer stem-like cells via down-regulation of Gli1 in lung cancer

Cancer stem cells (CSCs) are responsible for the tumorigenesis and recurrence, so targeting CSCs is a potential effective method to cure cancers. Activated Hedgehog signaling pathway has been proved to be implicated in the maintenance of self-renewal of CSCs, and arsenic trioxide (As2O3) has been reported to inhibit Gli1, a key transcription factor of Hedgehog pathway. In this study, we evaluated whether As2O3 has inhibitory effects on cancer stem-like cells (CSLCs) in lung cancer and further explored the possible mechanism. CCK8 assay and colony formation assay were performed to demonstrate the ability of As2O3 to inhibit the growth of NCI-H460 and NCI-H446 cells, which represented non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC), respectively. Tumor sphere formation assay was carried out to evaluate the effects of As2O3 on stem cell-like subpopulations. The expression of stem cell biomarkers CD133 and stem cell transcription factors such as Sox2 and Oct4 were detected. Moreover, the effects of As2O3 on expression of Gli1 and its target genes were observed. We found that As2O3 inhibited the cell proliferation and reduced the colony formation ability. Importantly, As2O3 decreased the formation of tumor spheres. The expression of stem cell biomarker CD133 and stem cell transcription factors such as Sox2 and Oct4 were markedly reduced by As2O3 treatment. Furthermore, As2O3 decreased the expression of Gli1, N-myc and GAS1. Our results suggested that As2O3 is a promising agent to inhibit CSLCs in lung cancer. In addition, the mechanism of CSLCs inhibition might involve Gli1 down-regulation.

CCN: core regulatory proteins in the microenvironment that affect the metastasis of hepatocellular carcinoma?

Hepatocellular carcinoma (HCC) results from an underlying chronic liver inflammatory disease, such as chronic hepatitis B or C virus infections, and the general prognosis of patients with HCC still remains extremely dismal because of the high frequency of HCC metastases. Throughout the process of tumor metastasis, tumor cells constantly communicate with the surrounding microenvironment and improve their malignant phenotype. Therefore, there is a strong rationale for targeting the tumor microenvironment as primary treatment of HCC therapies. Recently, CCN family proteins have emerged as localized multitasking signal integrators in the inflammatory microenvironment. In this review, we summarize the current knowledge of CCN family proteins in inflammation and the tumor. We also propose that the CCN family proteins may play a central role in signaling the tumor microenvironment and regulating the metastasis of HCC.

Lasting glycolytic stress governs susceptibility to urethane-induced lung carcinogenesis in vivo and in vitro

Urethane is a recognized genotoxic carcinogen in fermented foods and beverages. This study is to compare susceptibility of ICR mice, BALB/c mice and C57BL/6 mice to urethane-induced lung carcinogenesis. The mice were injected intraperitoneally with 600 mg/kg of urethane for three times or ten times at 7-day intervals. At week 26, lung carcinogenic incidence was found in 40% ICR mice, 20% BALB/c mice and 10% C57BL/6 mice of the 3× injection group, respectively, whereas 100% lung tumor incidence took place in three mouse strains of the 10× injection group. In the 10× injection group, urethane induced lasting glycolytic stress of lung with an increase in lactate, monocarboxylate transporter 1 (MCT-1), reactive oxygen species(ROS) and 7,8-dihydro-8-oxo-29-deoxyguanosine (8-OHdG) and a decrease in pyruvate dehydrogenase (PDH) and cytochrome C oxidase (COX). In the 3× injection group, urethane also promoted lung glycolytic stress at the end of urethane injection but it lasted no more than 7 days besides in lung tumor-bearing mice. Metformin as a glycolytic enhancer promoted urethane carcinogenic efficacy in the 3× injection group, whereas 2-deoxy-glucose (2-DG) as a glycolytic inhibitor decreased urethane carcinogenic efficacy in the 10× injection group. Further, urethane promoted tumor survival in A549 cells by inducing cancer stem-like cellular state. These data suggest that lasting glycolytic stress is sufficient for urethane-induced lung tumorigenesis, and that urethane 10× injection-induced lung cancer can serve as a valuable model for lung tumor biology and tumor prevention.

Exosomes derived from miR-122-modified adipose tissue-derived MSCs increase chemosensitivity of hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) displays high resistance to conventional chemotherapy. Considering that microRNA-122 (miR-122) performs an essential function to promote chemosensitivity of HCC cells, an effective vehicle-mediated miR-122 delivery may represent a promising strategy for HCC chemotherapy. An increasing interest is focused on the use of exosomes as biological vehicles for microRNAs (miRNA) transfer. Mesenchymal stem cells (MSCs) are known for their capacity to produce large amounts of exosomes. This study aimed to determine whether adipose tissue-derived MSC (AMSC) exosomes can be used for miR-122 delivery.

Methods

AMSCs were transfected with a miR-122 expression plasmid. At 48 h after transfection, AMSC-derived exosomes (122-Exo) were harvested and added to recipient HCC cells. Expression levels of miR-122 in AMSCs, exosomes, and HCC cells were quantified by real-time PCR. The mRNA and protein levels of miR-122-target genes in recipient HCC cells were quantified by real-time PCR and Western blot, respectively. The effects of 122-Exo on cell viability, apoptosis, and cell cycle of HCC cells were evaluated by MTT and flow cytometry analysis. Xenograft models were used to determine whether 122-Exo can sensitize HCC cells to sorafenib in vivo.

Results

Data showed that miR-122-transfected AMSC can effectively package miR-122 into secreted exosomes, which can mediate miR-122 communication between AMSCs and HCC cells, thereby rendering cancer cells sensitive to chemotherapeutic agents through alteration of miR-122-target gene expression in HCC cells. Moreover, intra-tumor injection of 122-Exo significantly increased the antitumor efficacy of sorafenib on HCC in vivo.

Conclusions

The findings suggest that the export of miR-122 via AMSC exosomes represents a novel strategy to enhance HCC chemosensitivity.

Genome-wide screen identified let-7c/miR-99a/miR-125b regulating tumor progression and stem-like properties in cholangiocarcinoma

Cholangiocarcinoma (CCA), which is a poor prognosis malignancy that arises from the malignant transformation of cholangiocytes, is associated with chronic inflammation of the biliary epithelium. Thus far, the molecular mechanisms of the origin and neoplastic processes of CCA that are promoted by inflammation are still unclear and need to be fully elucidated. Here using small RNA sequencing to determine the microRNA (miRNA) expression profiles in CCA, we found that let-7c, miR-99a and miR-125b, which are three miRNAs of the same cluster, were downregulated in CCA and targeted interleukin 6 (IL-6), IL-6R and type 1 insulin-like growth factor, which are important cytokines and receptors of the IL-6/signal transducer and activator 3 (STAT3) pathway and have key roles in inflammation and CCA initiation. We also found that enforced expression of let-7c, miR-99a or miR-125b could reduce the activity of STAT3 and further suppress CCA tumorigenicity in vivo and inhibit the migration and invasion of CCA cells in vitro. Surprisingly, let-7c/miR-99a/miR-125b cluster also significantly decreased the ability of CCA cells for cancer stem cell-like mammosphere generation by downregulating CD133 and CD44, which suggests the pivotal roles of let-7c, miR-99a and miR-125b in CCA by regulating both inflammation and stem-like properties. Our findings showed potential links between miRNAs and inflammation, and provide a potential treatment strategy for developing an miRNA-based therapy via IL-6/STAT3 targeting for CCA.

All-trans retinoic acid arrests cell cycle in leukemic bone marrow stromal cells by increasing intercellular communication through connexin 43-mediated gap junction

Background

Gap junctional intercellular communication (GJIC) is typically decreased in malignant tumors. Gap junction is not presented between hematopoietic cells but occurred in bone marrow stromal cells (BMSCs). Connexin 43 (Cx43) is the major gap junction (GJ) protein; our previous study revealed that Cx43 expression and GJIC were decreased in acute leukemic BMSCs. All-trans retinoic acid (ATRA) increases GJIC in a variety of cancer cells and has been used to treat acute promyelocytic leukemia, but the effects of ATRA on leukemic BMSCs is unknown. In this study, we evaluated the potential effects of ATRA on cell cycle, proliferation, and apoptosis of leukemic BMSCs. Effects of ATRA on Cx43 expression and GJIC were also examined.

Methods

Human BMSCs obtained from 25 patients with primary acute leukemia, and 10 normal healthy donors were cultured. Effects of ATRA on cell cycle, cell proliferation, and apoptosis were examined with or without co-treatment with amphotericin-B. Cx43 expression was examined at both the mRNA and protein expression levels. GJIC was examined by using a dye transfer assay and measuring the rate of fluorescence recovery after photobleaching (FRAP).

Results

ATRA arrested the cell cycle progression, inhibited cell growth, and increased apoptosis in leukemic BMSCs. Both Cx43 expression and GJIC function were increased by ATRA treatment. Most of the observed effects mediated by ATRA were abolished by amphotericin-B pretreatment.

Conclusions

ATRA arrests cell cycle progression in leukemic BMSCs, likely due to upregulating Cx43 expression and enhancing GJIC function.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-015-0212-7) contains supplementary material, which is available to authorized users.

Association Between Expression of Cancer Stem Cell Markers and Poor Differentiation of Hepatocellular Carcinoma: A Meta-Analysis (PRISMA)

The role of cancer stem cell (CSC) markers in differentiation of hepatocellular carcinoma (HCC) remains uncertain. We conducted a meta-analysis to first investigate the association between expression of CSC markers (CD133, CD90, CD44, and EpCAM) and poor differentiation of HCC, and second, to determine if these CSC markers can be classified as biomarkers for patient classification and HCC differentiated therapy.The relevant literature was searched using PubMed, EMBASE, Elsevier, and Chinese Biological Medicine databases for association between CSC markers and HCC from January 1, 2000 to June 30, 2014. Data were synthesized using random-effect or fixed-effect models. The effect sizes were estimated by measuring odds ratios (OR) with 95% confidence interval (CI).The meta-analysis included 27 studies consisting of 2897 patients with HCC. The positive expression of CSC markers was associated with poor differentiation (OR = 2.37, 95% CI = 2.03-2.77, P < 0.00001). Similarly, the positive expression of CSC markers was only associated with HCC tissues compared with noncancerous liver tissues (OR = 9.26, 95% CI = 3.10-27.65, P < 0.0001). CD90 has a specificity of 91.9% for HCC and a sensitivity of 48.22% in predicting poor differentiation.The positive expression of CSC markers is associated with poor differentiation and aggressive phenotype of patients with HCC. The CD90 marker might be a promising target for patient with HCC classification and differentiation therapy.

Randomized clinical control study of locoregional therapy combined with arsenic trioxide for the treatment of hepatocellular carcinoma

BACKGROUND

The objective of this study was to determine the efficacy and safety of locoregional therapy (LRT) combined with arsenic trioxide (As2 O3 ) treatment in primary hepatocellular carcinoma (HCC) patients.

METHODS

One hundred twenty-five primary HCC patients were recruited for a randomized controlled study. Patients were randomly divided into group A (n = 61) and group B (n = 64). All patients received transarterial chemoembolization. Group A patients were given As2 O3 at 10 mg/d for 4 courses (21 days per course) with a 2-week interval between courses. Survival times, therapeutic responses, extrahepatic metastases, and adverse events were recorded.

RESULTS

A better therapeutic response was found in group A patients, as shown by higher objective response rate (ORR) and clinical benefit rate (CBR) values in group A versus group B (ORR, 81.96% [95% confidence interval (CI), 72.32%-91.62%] vs 59.37% [95% CI, 47.34%-71.41%], χ(2)  = 7.650, P < .05; CBR, 95.08% [95% CI, 89.66%-100.00%] vs 81.25% [95% CI, 71.69%-90.81%], χ(2)  = 5.659, P < .05). There were fewer patients with extrahepatic metastases in group A versus group B (group A, 6 cases or 9.84% [95% CI, 2.36%-17.31%]; group B, 12 cases or 18.75% [95% CI, 9.19%-28.31%]). The survival rate for group A patients was significantly higher than that for group B patients (P < .05). No significant differences were found between the 2 groups in terms of hematology or digestive system, liver, or kidney dysfunction except for facial and limb edema.

CONCLUSIONS

LRT combined with As2 O3 treatment prevents extrahepatic metastasis and prolongs the survival time for primary HCC patients.

Management of hepatocellular carcinoma: Predictive value of immunohistochemical markers for postoperative survival

Hepatocellular carcinoma (HCC) accounts for over 90% of all primary liver cancers. With an ever increasing incidence trend year by year, it has become the third most common cause of death from cancer worldwide. Hepatic resection is generally considered to be one of the most effective therapies for HCC patients, however, there is a high risk of recurrence in postoperative HCC. In clinical practice, there exists an urgent need for valid prognostic markers to identify patients with prognosis, hence the importance of studies on prognostic markers in improving the prediction of HCC prognosis. This review focuses on the most promising immunohistochemical prognostic markers in predicting the postoperative survival of HCC patients.

Inhibition of the cancer stem cells-like properties by arsenic trioxide, involved in the attenuation of endogenous transforming growth factor beta signal

The elevation of cancer stem cells (CSCs)-like properties is involved in the initiation and progression of various human cancers. Current standard practices for treatment of cancers are less than satisfactory because of CSCs-mediated recurrence. For this reason, targeting the CSCs or the cancer cells with CSCs-like properties has become the new approach for the cancer treatments. In addition to treating leukemia, arsenic trioxide (As₂O₃) also suppresses other solid tumors. However, the roles of As₂O₃ in the regulation of CSCs-like properties remain largely uninvestigated. Here by using sphere formation assay, luciferase reporter assay, and some other molecular biology approaches, we found that As₂O₃ attenuated the CSCs-like properties in human hepatocellular carcinoma (HCC). Briefly, in HCC cells and mice xenograft models, As₂O₃ improved the expression of miR-491 by DNA-demethylation. MiR-491, which targeted the SMAD3-3'-UTR, decreased the expressions of SMAD3, and inhibited the CSCs-like properties in HCC cells. Knockdown of either miR-491 or SMAD3 attenuated the As₂O₃-induced inhibition of endogenous transforming growth factor beta signal and the CSCs-like properties. Further, in HCC patients, miR-491 is inversely correlated with the expressions of SMAD3, CD133, and the metastasis/recurrence outcome. By understanding a novel mechanism whereby As₂O₃ inhibits the CSCs-like properties in HCC, our study would help in the design of future strategies of developing As₂O₃ as a potential HCC chemopreventive agent when used alone or in combination with other current drugs.