Cancer Stem Cells: A Potential Breakthrough in HCC-Targeted Therapy

Pressure loading regulates the stemness of liver cancer stem cells via YAP/BMF signaling axis

Cancer stem cells (CSCs) are considered the major cause of the occurrence, progression, chemoresistance/radioresistance, recurrence, and metastasis of cancer. Increased interstitial fluid pressure (IFP) is a key feature of solid tumors. Our previous study showed that the distribution of liver cancer stem cells (LCSCs) correlated with the mechanical heterogeneity within liver cancer tissues. However, the regulation of liver cancer's mechanical microenvironment on the LCSC stemness is not fully understood. Here, we employed a cellular pressure-loading device to investigate the effects of normal IFP (5 mmHg), as well as increased IFP (40 and 200 mmHg) on the stemness of LCSCs. Compared to the control LCSCs (exposure to 5 mmHg pressure loading), the LCSCs exposed to 40 mmHg pressure loading exhibited significantly upregulated expression of CSC markers (CD44, EpCAM, Nanog), enhanced sphere and colony formation capacities, and tumorigenic potential, whereas continuously increased pressure to 200 mmHg suppressed the LCSC characteristics. Mechanistically, pressure loading regulated Yes-associated protein (YAP) activity and Bcl-2 modifying factor (BMF) expression. YAP transcriptionally regulated BMF expression to affect the stemness of LCSCs. Knockdown of YAP and overexpression of BMF attenuated pressure-mediated stemness and tumorgenicity, while YAP-deficient and BMF-deletion recused pressure-dependent stemness on LCSCs, suggesting the involvement of YAP/BMF signaling axis in this process. Together, our findings provide a potential target for overcoming the stemness of CSCs and elucidate the significance of increased IFP in cancer progression.

Targeting Hepatic Cancer Stem Cells (CSCs) and Related Drug Resistance by Small Interfering RNA (siRNA)

Tumor recurrence after curative therapy and hepatocellular carcinoma (HCC) cells' resistance to conventional therapies is the reasons for the worse clinical results of HCC patients. A tiny population of cancer cells with a strong potential for self-renewal, differentiation, and tumorigenesis has been identified as cancer stem cells (CSCs). The discovery of CSC surface markers and the separation of CSC subpopulations from HCC cells have been made possible by recent developments in the study of hepatic (liver) CSCs. Hepatic CSC surface markers include epithelial cell adhesion molecules (EpCAM), CD133, CD90, CD13, CD44, OV-6, ALDH, and K19. CSCs have a significant influence on the development of cancer, invasiveness, self-renewal, metastasis, and drug resistance in HCC, and thus provide a therapeutic chance to treat HCC and avoid its recurrence. Therefore, it is essential to develop treatment approaches that specifically and effectively target hepatic stem cells. Given this, one potential treatment approach is to use particular small interfering RNA (siRNA) to target CSC, disrupting their behavior and microenvironment as well as changing their epigenetic state. The characteristics of CSCs in HCC are outlined in this study, along with new treatment approaches based on siRNA that may be used to target hepatic CSCs and overcome HCC resistance to traditional therapies.

Mitochondria's Role in the Maintenance of Cancer Stem Cells in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the predominant form of liver cancer and is recognized as a major contributor to cancer-related mortality worldwide. Cancer stem cells (CSCs) are a tiny group of cancer cells that possess a significant ability to regenerate themselves, form tumors, and undergo differentiation. CSCs have a pivotal role in the initiation, spread, recurrence, and resistance to treatment of cancer. As a result, they are very susceptible to being targeted for therapeutic intervention. The potential to cure HCC may be achieved by efficiently targeting drugs that eradicate cancer stem cells. Mitochondria have a crucial function in granting drug resistance to cancer stem cells by means of mitochondrial metabolism, biogenesis, and dynamics. Dysfunction in mitochondrial metabolic processes, such as mitochondrial oxidative phosphorylation (OXPHOS), calcium signaling, and reactive oxygen species (ROS) generation, contributes to the initiation and progression of human malignancies, including HCC. ROS have both beneficial and detrimental effects depending on their concentration. Consequently, ROS have become a prominent subject in the study of the fundamental mechanisms of HCC. Furthermore, an imbalance in the process of creating new mitochondria is a characteristic feature of CSCs, and an increase in mitochondrial biogenesis is associated with the heightened resistance observed in CSCs. This article provides a detailed examination of the involvement of mitochondria in the preservation of CSCs, as well as the spread of HCC. A deeper understanding of how mitochondria participate in tumorigenesis and drug resistance could result in the discovery of novel cancer treatments.

Heterogeneity of hepatocellular carcinoma: from mechanisms to clinical implications

Hepatocellular Carcinoma (HCC) is one of the most common types of primary liver cancer. Current treatment options have limited efficacy against this malignancy, primarily owing to difficulties in early detection and the inherent resistance to existing drugs. Tumor heterogeneity is a pivotal factor contributing significantly to treatment resistance and recurrent manifestations of HCC. Intratumoral heterogeneity is an important aspect of the spectrum of complex tumor heterogeneity and contributes to late diagnosis and treatment failure. Therefore, it is crucial to thoroughly understand the molecular mechanisms of how tumor heterogeneity develops. This review aims to summarize the possible molecular dimensions of tumor heterogeneity with an emphasis on intratumoral heterogeneity, evaluate its profound impact on the diagnosis and therapeutic strategies for HCC, and explore the suitability of appropriate pre-clinical models that can be used to best study tumor heterogeneity; thus, opening new avenues for cancer treatment.

Engineering principles for rationally design therapeutic strategies against hepatocellular carcinoma

The search for new therapeutic strategies against cancer has favored the emergence of rationally designed treatments. These treatments have focused on attacking cell plasticity mechanisms to block the transformation of epithelial cells into cancerous cells. The aim of these approaches was to control particularly lethal cancers such as hepatocellular carcinoma. However, they have not been able to control the progression of cancer for unknown reasons. Facing this scenario, emerging areas such as systems biology propose using engineering principles to design and optimize cancer treatments. Beyond the possibilities that this approach might offer, it is necessary to know whether its implementation at a clinical level is viable or not. Therefore, in this paper, we will review the engineering principles that could be applied to rationally design strategies against hepatocellular carcinoma, and discuss whether the necessary elements exist to implement them. In particular, we will emphasize whether these engineering principles could be applied to fight hepatocellular carcinoma.

Non-coding RNA mediated regulation of PI3K/Akt pathway in hepatocellular carcinoma: Therapeutic perspectives

Hepatocellular carcinoma (HCC) is among the primary reasons for fatalities caused by cancer globally, highlighting the need for comprehensive knowledge of its molecular aetiology to develop successful treatment approaches. The PI3K/Akt system is essential in the course of HCC, rendering it an intriguing candidate for treatment. Non-coding RNAs (ncRNAs), such as long ncRNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs), are important mediators of the PI3K/Akt network in HCC. The article delves into the complex regulatory functions of ncRNAs in influencing the PI3K/Akt system in HCC. The study explores how lncRNAs, miRNAs, and circRNAs impact the expression as well as the function of the PI3K/Akt network, either supporting or preventing HCC growth. Additionally, treatment strategies focusing on ncRNAs in HCC are examined, such as antisense oligonucleotide-based methods, RNA interference, and small molecule inhibitor technologies. Emphasizing the necessity of ensuring safety and effectiveness in clinical settings, limitations, and future approaches in using ncRNAs as therapies for HCC are underlined. The present study offers useful insights into the complex regulation system of ncRNAs and the PI3K/Akt cascade in HCC, suggesting possible opportunities for developing innovative treatment approaches to address this lethal tumor.

The roles of cancer stem cell-derived secretory factors in shaping the immunosuppressive tumor microenvironment in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most prevalent malignancies worldwide and has a poor prognosis. Although immune checkpoint inhibitors have entered a new era of HCC treatment, their response rates are modest, which can be attributed to the immunosuppressive tumor microenvironment within HCC tumors. Accumulating evidence has shown that tumor growth is fueled by cancer stem cells (CSCs), which contribute to therapeutic resistance to the above treatments. Given that CSCs can regulate cellular and physical factors within the tumor niche by secreting various soluble factors in a paracrine manner, there have been increasing efforts toward understanding the roles of CSC-derived secretory factors in creating an immunosuppressive tumor microenvironment. In this review, we provide an update on how these secretory factors, including growth factors, cytokines, chemokines, and exosomes, contribute to the immunosuppressive TME, which leads to immune resistance. In addition, we present current therapeutic strategies targeting CSC-derived secretory factors and describe future perspectives. In summary, a better understanding of CSC biology in the TME provides a rational therapeutic basis for combination therapy with ICIs for effective HCC treatment.

Overview of hepatocellular carcinoma: from molecular aspects to future therapeutic options

Hepatocellular carcinoma (HCC) is the seventh most highly prevalent malignant tumor globally and the second most common cause of mortality. HCC develops with complex pathways that occur through multistage biological processes. Non-alcoholic fatty liver disease, metabolic-associated fatty liver disease, alcoholic liver disease, autoimmune hepatitis, hepatitis B, and hepatitis C are the causative etiologies of HCC. HCC develops as a result of epigenetic changes, protein-coding gene mutations, and altered signaling pathways. Biomarkers and potential therapeutic targets for HCC open up new possibilities for treating the disease. Immune checkpoint inhibitors are included in the treatment options in combination with molecular targeted therapy.

CircRNAs regulate the crosstalk between inflammation and tumorigenesis: The bilateral association and molecular mechanisms

Inflammation, a hallmark of cancer, has been associated with tumor progression, transition into malignant phenotype and efficacy of the chemotherapeutic agents in cancer. Chronic inflammation provides a favorable environment for tumorigenesis by inducing immunosuppression, whereas acute inflammation prompts tumor suppression by generating anti-tumor immune responses. Inflammatory factors derived from interstitial cells or tumor cells can stimulate cell proliferation and survival by modulating oncogenes and/or tumor suppressors. Recently, a new class of RNAs, i.e., circular RNAs (circRNAs), has been implicated in inflammatory diseases. Although there are reports on circRNAs imparting functions in inflammatory insults, whether these circularized transcripts hold the potential to regulate inflammation-induced cancer or tumor-related inflammation, and modulate the interactions between tumor microenvironment (TME) and the inflammatory stromal/immune cells, awaits further elucidation. Contextually, the current review describes the molecular association between inflammation and cancer, and spotlights the regulatory mechanisms by which circRNAs can moderate TME in response to inflammatory signals/triggers. We also present comprehensive information about the immune cell(s)-specific expression and functions of the circRNAs in TME, modulation of inflammatory signaling pathways to drive tumorigenesis, and their plausible roles in inflammasomes and tumor development. Moreover, the therapeutic potential of these circRNAs in harnessing inflammatory responses in cancer is also discussed.

Furanocoumarin Notopterol: Inhibition of Hepatocellular Carcinogenesis through Suppression of Cancer Stemness Signaling and Induction of Oxidative Stress-Associated Cell Death

BACKGROUND

Hepatocellular carcinoma (HCC) remains an aggressive malignancy with a poor prognosis and a leading cause of cancer-related mortality globally. Cumulative evidence suggests critical roles for endoplasmic reticulum (ER) stress and unfolded protein response (UPR) in chronic liver diseases. However, the role of ER stress in HCC pathogenesis, aggressiveness and therapy response remains unclear and understudied.

OBJECTIVES

Against this background, the present study evaluated the therapeutic efficacy and feasibility of notopterol (NOT), a furanocoumarin and principal component of Notopterygium incisum, in the modulation of ER stress and cancer stemness, and the subsequent effect on liver oncogenicity.

METHODS

An array of biomolecular methods including Western blot, drug cytotoxicity, cell motility, immunofluorescence, colony and tumorsphere formation, flow-cytometric mitochondrial function, GSH/GSSG ratio, and tumor xenograft ex vivo assays were used in the study.

RESULTS

Herein, we demonstrated that NOT significantly suppresses the viability, migration, and invasion capacity of the human HCC HepJ5 and Mahlavu cell lines by disrupting ATF4 expression, inhibiting JAK2 activation, and downregulating the GPX1 and SOD1 expression in vitro. NOT also markedly suppressed the expression of vimentin (VIM), snail, b-catenin, and N-cadherin in the HCC cells, dose-dependently. Treatment with NOT significantly attenuated cancer stem cells (CSCs)-like phenotypes, namely colony and tumorsphere formation, with the concomitant downregulation of stemness markers OCT4, SOX2, CD133, and upregulated PARP-1 cleavage, dose-dependently. We also demonstrated that NOT anticancer activity was strongly associated with increased cellular reactive oxidative stress (ROS) but, conversely, reduced mitochondrial membrane potential and function in the HepJ5 and Mahlavu cells in vitro. Our tumor xenograft studies showed that compared with sorafenib, NOT elicited greater tumor growth suppression without adverse changes in mice body weights. Compared with the untreated control and sorafenib-treated mice, NOT-treated mice exhibited markedly greater apoptosis ex vivo, and this was associated with the co-suppression of stemness and drug-resistance markers OCT4, SOX2, ALDH1, and the upregulation of endoplasmic reticulum stress and oxidative stress factors PERK and CHOP.

CONCLUSIONS

In summary, we demonstrated for the first time that NOT exhibits strong anticancer activity via the suppression of cancer stemness, enhanced endoplasmic reticulum stress and increased oxidative stress thus projecting NOT as a potentially effective therapeutic agent against HCC.

Fueling HCC Dynamics: Interplay Between Tumor Microenvironment and Tumor Initiating Cells

Liver cancer (hepatocellular carcinoma) is a common cancer worldwide. It is an aggressive cancer, with high rates of tumor relapse and metastasis, high chemoresistance, and poor prognosis. Liver tumor-initiating cells (LTICs) are a distinctive subset of liver cancer cells with self-renewal and differentiation capacities that contribute to intratumoral heterogeneity, tumor recurrence, metastasis, and chemo-drug resistance. LTICs, marked by different TIC markers, have high plasticity and use diverse signaling pathways to promote tumorigenesis and tumor progression. LTICs are nurtured in the tumor microenvironment (TME), where noncellular and cellular components participate to build an immunosuppressive and tumor-promoting niche. As a result, the TME has emerged as a promising anticancer therapeutic target, as exemplified by some successful applications of tumor immunotherapy. In this review, we discuss the plasticity of LTICs in terms of cellular differentiation, epithelial-mesenchymal transition, and cellular metabolism. We also discuss the various components of the TME, including its noncellular and cellular components. Thereafter, we discuss the mutual interactions between TME and LTICs, including recently reported molecular mechanisms. Lastly, we summarize and describe new ideas concerning novel approaches and strategies for liver cancer therapy.

MicroRNA-6838-5p suppresses the self-renewal and metastasis of human liver cancer stem cells through downregulating CBX4 expression and inactivating ERK signaling

Hepatocellular carcinoma (HCC) is the most common primary human liver malignancy with high mortality. Liver cancer stem cells (CSCs) have been demonstrated to contribute to the recurrence, metastasis and drug resistance of liver cancer. Human HCC cohort analysis indicated that the epigenetic regulator polycomb chromobox homologue 4 (CBX4) was overexpressed in human HCC. Moreover, we found that CBX4 expression was significantly higher in CD44⁺ CD133⁺ Hep3B CSCs. Functionally, we demonstrated that CBX4 regulated cell proliferation, self-renewal, and metastasis ability of Hep3B CSCs. Bioinformatics analysis predicted that CBX4 was a direct target of microRNA-6838-5p (miR-6838-5p), which was further confirmed by luciferase reporter assay. MiR-6838-6p was down-regulated in HCC tumors and overexpression of miR-6838-5p attenuated the malignant traits of human liver CSCs in vitro. In addition, we found that miR-6838-5p/CBX4 axis modulates the biological properties of human liver CSCs via regulating ERK signaling. Overexpression of miR-6838-5p suppressed Hep3B xenograft tumor growth in vivo, while CBX4 overexpression abrogated the suppression effect, restored the angiogenesis, epithelial-to-mesenchymal transition (EMT), and ERK signaling in Hep3B tumor. In summary, our findings suggest that miR-6838-5p/CBX4 axis regulates liver tumor development and metastasis, which could be utilized as potential therapeutic target for HCC treatment.

Recent progress in molecular mechanisms of postoperative recurrence and metastasis of hepatocellular carcinoma

Hepatectomy is currently considered the most effective option for treating patients with early and intermediate hepatocellular carcinoma (HCC). Unfortunately, the postoperative prognosis of patients with HCC remains unsatisfactory, predominantly because of high postoperative metastasis and recurrence rates. Therefore, research on the molecular mechanisms of postoperative HCC metastasis and recurrence will help develop effective intervention measures to prevent or delay HCC metastasis and recurrence and to improve the long-term survival of HCC patients. Herein, we review the latest research progress on the molecular mechanisms underlying postoperative HCC metastasis and recurrence to lay a foundation for improving the understanding of HCC metastasis and recurrence and for developing more precise prevention and intervention strategies.

A Novel 3D Culture Scaffold to Shorten Development Time for Multicellular Tumor Spheroids

Multicellular tumor spheroids and tumoroids are considered ideal in vitro models that reflect the features of the tumor microenvironment. Biomimetic components resembling the extracellular matrix form scaffolds to provide structure to 3-dimensional (3D) culture systems, supporting the growth of both spheroids and tumoroids. Although Matrigel has long been used to support 3D culture systems, batch variations, component complexity, and the use of components derived from tumors are complicating factors. To address these issues, we developed the ACD 3D culture system to provide better control and consistency. We evaluated spheroid and tumoroid formation using the ACD 3D culture system, including the assessment of cell viability and cancer marker expression. Under ACD 3D culture conditions, spheroids derived from cancer cell lines exhibited cancer stem cell characteristics, including a sphere-forming size and the expression of stem cell marker genes. The ACD 3D culture system was also able to support patient-derived primary cells and organoid cell cultures, displaying adequate cell growth, appropriate morphology, and resistance to oxaliplatin treatment. These spheroids could also be used for drug screening purposes. In conclusion, the ACD 3D culture system represents an efficient tool for basic cancer research and therapeutic development.

DNMT and EZH2 inhibitors synergize to activate therapeutic targets in hepatocellular carcinoma

The development of more effective targeted therapies for hepatocellular carcinoma (HCC) patients due to its aggressiveness is urgently needed. DNA methyltransferase inhibitors (DNMTis) represented the first clinical breakthrough to target aberrant cancer epigenomes. However, their clinical efficacies are still limited, in part due to an "epigenetic switch" in which a large group of genes that are demethylated by DNMTi treatment remain silenced by polycomb repressive complex 2 (PRC2) occupancy. EZH2 is the member of PRC2 that catalyzes the placement of H3K27me3 marks. EZH2 overexpression is correlated with poor HCC patient survival. We tested the combination of a DNMTi (5-aza-2'-deoxycytidine, DAC) and the EZH2 inhibitor (EZH2i) GSK126 in human HCC cell lines on drug sensitivity, DNA methylation, nucleosome accessibility, and gene expression profiles. Compared with single agent treatments, all HCC cell lines studied showed increased sensitivity after receiving both drugs concomitant with prolonged anti-proliferative changes and sustained reactivation of nascently-silenced genes. The increased number of up-regulated genes after combination treatment correlated with prolonged anti-proliferation effects and increased nucleosome accessibility. Combination treatments also activate demethylated promoters that are repressed by PRC2 occupancy. Furthermore, 13-31% of genes down-regulated by DNA methylation in primary HCC tumors were reactivated through this combination treatment scheme in vitro. Finally, the combination treatment also exacerbates anti-tumor immune responses, while most of these genes were downregulated in over 50% of primary HCC tumors. We have linked the anti-tumor effects of DAC and GSK126 combination treatments to detailed epigenetic alterations in HCC cells, identified potential therapeutic targets and provided a rationale for treatment efficacy for HCC patients.

Connexin32 regulates expansion of liver cancer stem cells via the PI3K/Akt signaling pathway

Liver cancer stem cells (LCSCs) are responsible for liver cancer recurrence, metastasis, and drug resistance. Previous studies by the authors demonstrated that upregulated expression of connexin 32 (Cx32) reversed doxorubicin resistance and reduced invasion and metastasis of liver cancer cells. However, the role of Cx32 in expansion of LCSCs remains unclear. A total of 85 patients were enrolled in the present study and followed-up for 5 years. The expression of Cx32 in hepatocellular carcinoma (HCC) tissues and corresponding paracancerous tissues were detected by immunohistochemistry (IHC). Cx32 was silenced in HepG2 cells and overexpressed in HCCLM3 cells and the stemness of liver cells was examined by detecting the expression of LCSC markers (EpCAM, CD133, Nanog, Oct4, Sox9, c-Myc), sphere formation, and xenograft tumorigenesis. Finally, the effect of the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway on Cx32-regulated LCSC expansion was investigated. Cx32 was downregulated in LCSCs and HCC tissues, and predicted poor prognosis in patients with HCC. Overexpression of Cx32 in HCCLM3 cells significantly inhibited LCSC expansion, tumorigenesis, and phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) pathway activity. By contrast, silencing of Cx32 in HepG2 cells upregulated expansion of LCSCs and PI3K/Akt pathway activity. Modulating the activity of the PI3K/Akt pathway by SC-79 and LY294002 in HepG2 and HCCLM3 cells, respectively, confirmed that Cx32 could affect the expansion of LCSCs through PI3K/Akt signaling. In conclusion, the present study demonstrated that Cx32 regulated the expansion of LCSCs, and increased expression of Cx32 significantly inhibited the expansion of LCSCs, suggesting that Cx32 may be an optimal target for intervention of HCC.

Improving the Therapeutic Efficacy of Sorafenib for Hepatocellular Carcinoma by Repurposing Disulfiram

Background

Sorafenib, a kinase inhibitor, is a standard treatment for advanced hepatocellular carcinoma (HCC) but provides only a limited survival benefit. Disulfiram (DSF), a drug for treating alcoholism and a chelator of copper (Cu), forms a complex with Cu (DSF/Cu). DSF/Cu is a potent inducer of autophagic apoptosis of cancer stem cells, which can demonstrate drug resistance. Thus, we hypothesized that DSF/Cu could increase the sensitivity of HCC cells to sorafenib by targeting hepatic cancer stem cells.

Methods

The synergistic effect of DSF/Cu and sorafenib on human HCC cell lines was assessed by cell viability MTT assay. Changes in stemness gene expression in HCC cells were investigated by assessing the presence of hepatic cancer stem cells (HCSCs) (defined as ALDH+ cells) using flow cytometry, sphere formation ability as an index of in vitro tumorigenicity, and expression of stemness gene-encoded proteins by western blot. Autophagic apoptosis and the ERK signaling pathway were also assessed by western blot. Most importantly, the in vivo anti-tumor efficacy of DSF/Cu and sorafenib was tested using orthotopic HCC xenografts in mice.

Results

Compared with sorafenib alone, DSF/Cu + sorafenib synergistically inhibited proliferation of all HCC cell lines, decreased the stemness of HCC cells, and increased the autophagy and apoptosis of HCC cells. The mechanism by which DSF/Cu mediated these phenomena with sorafenib was sustained activation of the ERK pathway. The combination of DSF/Cu (formed with endogenous Cu2+) and sorafenib was significantly more effective than sorafenib alone in inhibiting the growth of orthotopic HCC xenografts in mice. This in vivo anti-tumor efficacy was associated with decreased stemness in treated HCC tumors.

Conclusions

DSF/Cu and sorafenib can synergistically and effectively treat HCC by targeting HCSCs in vitro and in vivo. Our data provide a foundation for clinical translation.

Identification and Validation of a Potential Stemness-Associated Biomarker in Hepatocellular Carcinoma

Background

Cancer stem cells (CSCs) are typically related to metastasis, recurrence, and drug resistance in malignant tumors. However, the biomarker and mechanism of CSCs need further exploration. This study is aimed at comprehensively depicting the stemness characteristics and identify a potential stemness-associated biomarker in hepatocellular carcinoma (HCC).

Methods

The data of HCC patients from The Cancer Genome Atlas (TCGA) were collected and divided based on the mRNA expression-based stemness index (mRNAsi) in this study. Weighted gene coexpression network analysis (WGCNA) and the protein-protein interaction (PPI) network were performed, and the genes were screened through the Cytoscape software. Then, we constructed a prognostic expression signature using the multivariable Cox analysis and verified using the GEO and ICGC databases. Even more importantly, we used the three-dimensional (3D) fibrin gel to enrich the tumor-repopulating cells (TRCs) to validate the expression of the signature in CSCs by quantitative RT-PCR.

Results

mRNAsi was significantly elevated in tumor and high-mRNAsi score was associated with poor overall survival in HCC. The positive stemness-associated (blue) module with 737 genes were screened based on WGCNA, and Budding uninhibited by benzimidazoles 1 (BUB1) was identified as the hub gene highly related to stemness in HCC. Then, the prognostic value and stemness characteristics were well validated in the ICGC and GSE14520 cohorts. Further analysis showed the expression of BUB1 was elevated in TRCs.

Conclusion

BUB1, as a potential stemness-associated biomarker, could serve as a therapeutic CSCs-target and predicted the clinical outcomes of patients with HCC.

JIB-04, a Pan-Inhibitor of Histone Demethylases, Targets Histone-Lysine-Demethylase-Dependent AKT Pathway, Leading to Cell Cycle Arrest and Inhibition of Cancer Stem-Like Cell Properties in Hepatocellular Carcinoma Cells

JIB-04, a pan-histone lysine demethylase (KDM) inhibitor, targets drug-resistant cells, along with colorectal cancer stem cells (CSCs), which are crucial for cancer recurrence and metastasis. Despite the advances in CSC biology, the effect of JIB-04 on liver CSCs (LCSCs) and the malignancy of hepatocellular carcinoma (HCC) has not been elucidated yet. Here, we showed that JIB-04 targeted KDMs, leading to the growth inhibition and cell cycle arrest of HCC, and abolished the viability of LCSCs. JIB-04 significantly attenuated CSC tumorsphere formation, growth, relapse, migration, and invasion in vitro. Among KDMs, the deficiency of KDM4B, KDM4D, and KDM6B reduced the viability of the tumorspheres, suggesting their roles in the function of LCSCs. RNA sequencing revealed that JIB-04 affected various cancer-related pathways, especially the PI3K/AKT pathway, which is crucial for HCC malignancy and the maintenance of LCSCs. Our results revealed KDM6B-dependent AKT2 expression and the downregulation of E2F-regulated genes via JIB-04-induced inhibition of the AKT2/FOXO3a/p21/RB axis. A ChIP assay demonstrated JIB-04-induced reduction in H3K27me3 at the AKT2 promoter and the enrichment of KDM6B within this promoter. Overall, our results strongly suggest that the inhibitory effect of JIB-04 on HCC malignancy and the maintenance of LCSCs is mediated via targeting the KDM6B-AKT2 pathway, indicating the therapeutic potential of JIB-04.

Hypoxia‑inducible factor‑1α: A critical target for inhibiting the metastasis of hepatocellular carcinoma (Review)

Metastasis is one of the major reasons for patient mortality in hepatocellular carcinoma (HCC), and the progression of HCC to a metastatic state depends on the local microenvironment. Hypoxia is a key condition affecting the microenvironment of HCC. Currently, various studies have shown that the expression of hypoxia-ainducible factor-1α (HIF-1α) is associated with the invasion and metastasis of HCC. High expression of HIF-1α often leads to poor prognosis in patients with HCC. In this review, the molecular structure of HIF-1α is described, and the expression pattern of HIF-1α in HCC under hypoxia, which is associated with metastasis and poor prognosis in HCC, is explained. The molecular mechanisms of HIF-1α function and the metastasis of HCC are further discussed. The modulation of HIF-1α can reduce sorafenib resistance and improve the prognosis of patients after TACE. Therefore, HIF-1α may be a critical target for inhibiting HCC metastasis in the future.

Data Centric Molecular Analysis and Evaluation of Hepatocellular Carcinoma Therapeutics Using Machine Intelligence-Based Tools

PURPOSE

Computational approaches have been used at different stages of drug development with the purpose of decreasing the time and cost of conventional experimental procedures. Lately, techniques mainly developed and applied in the field of artificial intelligence (AI), have been transferred to different application domains such as biomedicine.

METHODS

In this study, we conducted an investigative analysis via data-driven evaluation of potential hepatocellular carcinoma (HCC) therapeutics in the context of AI-assisted drug discovery/repurposing. First, we discussed basic concepts, computational approaches, databases, modeling approaches, and featurization techniques in drug discovery/repurposing. In the analysis part, we automatically integrated HCC-related biological entities such as genes/proteins, pathways, phenotypes, drugs/compounds, and other diseases with similar implications, and represented these heterogeneous relationships via a knowledge graph using the CROssBAR system.

RESULTS

Following the system-level evaluation and selection of critical genes/proteins and pathways to target, our deep learning-based drug/compound-target protein interaction predictors DEEPScreen and MDeePred have been employed for predicting new bioactive drugs and compounds for these critical targets. Finally, we embedded ligands of selected HCC-associated proteins which had a significant enrichment with the CROssBAR system into a 2-D space to identify and repurpose small molecule inhibitors as potential drug candidates based on their molecular similarities to known HCC drugs.

CONCLUSIONS

We expect that these series of data-driven analyses can be used as a roadmap to propose early-stage potential inhibitors (from database-scale sets of compounds) to both HCC and other complex diseases, which may subsequently be analyzed with more targeted in silico and experimental approaches.

Three dimensional in vitro culture systems in anticancer drug discovery targeted on cancer stem cells

Worldwide, tumors are one of the most common causes of death. Every year 3.7 million new cases occur in Europe and more than 1.9 million patients die (WHO data). Most of the fields of research are focused on developing new therapeutic strategies that will be effective in eliminating the tumor, preventing its remission, and avoiding or reducing the side effects of therapy. In the past, generally classical 2D cell cultures or immunodeficient animal models had been used to cultivate and test drugs on human cancer cell lines. Nowadays, there are increasing interests in three-dimensional (3D) cell cultures, a method with significant differences from flat cultured cells, both considering gene expressions and cell-cell interactions. Various evidence suggests that high tumorigenic properties might be dependent on the occurrence of a small cell population, pointed out to be responsible for metastasis and recurrence. This population is called cancer stem cells (CSCs), hinted to have a lot of similarities with normal stem cells. CSCs are the main reason for chemotherapy failure as well as multi-drug resistance (MDR). CSCs can also interact through the cytokine network, with other cells like the macrophages of the inflammatory system. The big advantage of a 3D culture is the possibility to isolate and investigate the CSCs population surrounded by its environment. This article aims to sum up known 3D cell cultures, especially in the field of CSCs research due to the importance of the tumor's environment on stem cell's markers expression and their development.

Glucose and Amino Acid Metabolic Dependencies Linked to Stemness and Metastasis in Different Aggressive Cancer Types

Malignant cells are commonly characterised by being capable of invading tissue, growing self-sufficiently and uncontrollably, being insensitive to apoptosis induction and controlling their environment, for example inducing angiogenesis. Amongst them, a subpopulation of cancer cells, called cancer stem cells (CSCs) shows sustained replicative potential, tumor-initiating properties and chemoresistance. These characteristics make CSCs responsible for therapy resistance, tumor relapse and growth in distant organs, causing metastatic dissemination. For these reasons, eliminating CSCs is necessary in order to achieve long-term survival of cancer patients. New insights in cancer metabolism have revealed that cellular metabolism in tumors is highly heterogeneous and that CSCs show specific metabolic traits supporting their unique functionality. Indeed, CSCs adapt differently to the deprivation of specific nutrients that represent potentially targetable vulnerabilities. This review focuses on three of the most aggressive tumor types: pancreatic ductal adenocarcinoma (PDAC), hepatocellular carcinoma (HCC) and glioblastoma (GBM). The aim is to prove whether CSCs from different tumour types share common metabolic requirements and responses to nutrient starvation, by outlining the diverse roles of glucose and amino acids within tumour cells and in the tumour microenvironment, as well as the consequences of their deprivation. Beyond their role in biosynthesis, they serve as energy sources and help maintain redox balance. In addition, glucose and amino acid derivatives contribute to immune responses linked to tumourigenesis and metastasis. Furthermore, potential metabolic liabilities are identified and discussed as targets for therapeutic intervention.

Bie Jia Jian Pill Combined with Bone Mesenchymal Stem Cells Regulates microRNA-140 to Suppress Hepatocellular Carcinoma Stem Cells

Background and Objectives

Cancer stem cells (CSCs) with tumorigenic potential are reported as the crucial factors of hepatocellular carcinoma (HCC) recurrence and therapy resistance. Bone mesenchymal stem cells (BMSCs) are documented to play an important role in the protection of hepatocytes. Bie Jia Jian pill (BJJP), a Traditional Chinese Medicine, has been used to treat liver fibrosis and liver cancer. This study aimed to explore the potential role of combined use of BJJP with BMSCs in HCC cell lines.

Methods and Results

Flow cytometry was used to identify BMSCs isolated from BALB/c mice and CSCs enriched from Huh7 cells by measuring CD24, CD133, CD44, CD73, CD105, CD166, CD29, CD14 and CD34. Differentiation potential of BMSCs was also determined. Cell viability and proliferation ability of CSCs were determined by CCK-8 assay and clone formation assay. The expressions of CSCs biomarkers and Wnt/β-catenin signal pathway related proteins were determined by PCR and western blot. TOP-Flash/FOP-Flash luciferase assay was applied to measure the activity of β-catenin/TCF. Compared with untreated CSCs, BJJP or BMSCs treatment alone on CSCs lead to increased miR-140 expression and cell apoptosis, as well as decreased expressions of CD24, CD133, EpCAM and cell viability. Downregualted expressions of Wnt/β-catenin signal pathway related proteins, Wnt3a and β-catenin were found in response to BJJP or BMSCs treatment alone. The combination of BJJP＋BMSCs treatment on CSCs could further enhance the suppressive effect on CSCs. Down-regulation of miR-140 in CSCs partially blocked the effects of BMSCs or BMSCs＋BJJP on the expressions of Wnt3a and β-catenin as well as the cell viability and apoptosis of CSCs. Reversed expression pattern was found in CSCs transfected with miR-140 overexpression.

Conclusions

Taken together, we demonstrate that BJJP＋BMSCs together could further enhance the suppressive effect on CSCs through regulating miR-140 and suppressing Wnt/β-catenin signal pathway. This study demonstrated the potential of BJJP＋BMSCs in therapeutic treatment of HCC.

Immunological Value of Prognostic Signature Based on Cancer Stem Cell Characteristics in Hepatocellular Carcinoma

Background: Liver cancer stem cells, characterized by self-renewal and initiating cancer cells, were decisive drivers of progression and therapeutic resistance in hepatocellular carcinoma (HCC). However, a comprehensive understanding of HCC stemness has not been identified.

Methods: RNA sequencing information, corresponding clinical annotation, and mutation data of HCC were downloaded from The Cancer Genome Atlas-LIHC project. Two stemness indices, mRNA expression-based stemness index (mRNAsi) and epigenetically regulated-mRNAsi, were used to comprehensively analyze HCC stemness. Estimation of Stromal and Immune Cells in Malignant Tumors using Expression Data and single-sample gene-set enrichment analysis algorithm were performed to characterize the context of tumor immune microenvironment (TIME). Next, differentially expressed gene (DEG) analysis and weighted gene co-expression network analysis (WGCNA) were employed to identify significant mRNAsi-related modules with hub genes. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment pathways were analyzed to functionally annotate these key genes. The least absolute shrinkage and selection operator (LASSO) Cox regression analysis was performed to establish a prognostic signature. Kaplan–Meier survival curves and receiver operating characteristic (ROC) analysis were applied for prognostic value validation. Seven algorithms (XCELL, TIMER, QUANTISEQ, MCPcounter, EPIC, CIBERSORT, and CIBERSORT-ABS) were utilized to draw the landscape of TIME. Finally, the mutation data were analyzed by employing “maftools” package.

Results: mRNAsi was significantly elevated in HCC samples. mRNAsi escalated as tumor grade increased, with poor prognosis presenting the higher stemness index. The stemness-related (greenyellow) modules with 175 hub genes were screened based on DEGs and WGCNA. A prognostic signature was established using LASSO analysis of prognostic hub genes to classify samples into two risk subgroups, which exhibited good prognostic performance. Additionally, prognostic risk-clinical nomogram was drawn to estimate risk quantitatively. Moreover, risk score was significantly associated with contexture of TIME and immunotherapeutic targets. Finally, potential interaction between risk score with tumor mutation burden (TMB) was elucidated.

Conclusion: This work comprehensively elucidated that stemness characteristics served as a crucial player in clinical outcome, complexity of TIME, and immunotherapeutic prediction from both mRNAsi and mRNA level. Quantitative identification of stemness characteristics in individual tumor will contribute into predicting clinical outcome, mapping landscape of TIME further optimizing precision immunotherapy.

GNS561, a New Autophagy Inhibitor Active against Cancer Stem Cells in Hepatocellular Carcinoma and Hepatic Metastasis from Colorectal Cancer

Patients with advanced hepatocellular carcinoma (HCC) or metastatic colorectal cancer (mCRC) have a very poor prognosis due to the lack of efficient treatments. As observed in several other tumors, the effectiveness of treatments is mainly hampered by the presence of a highly tumorigenic sub-population of cancer cells called cancer stem cells (CSCs). Indeed, CSCs are resistant to chemotherapy and radiotherapy and can regenerate the tumor bulk. Hence, innovative drugs that are efficient against both bulk tumor cells and CSCs would likely improve cancer treatment. In this study, we demonstrated that GNS561, a new autophagy inhibitor that induces lysosomal cell death, showed significant activity against not only the whole tumor population but also a sub-population displaying CSC features (high ALDH activity and tumorsphere formation ability) in HCC and in liver mCRC cell lines. These results were confirmed in vivo in HCC from a DEN-induced cirrhotic rat model in which GNS561 decreased tumor growth and reduced the frequency of CSCs (CD90+CD45-). Thus, GNS561 offers great promise for cancer therapy by exterminating both the tumor bulk and the CSC sub-population. Accordingly, a global phase 1b clinical trial in liver cancers was recently completed.

Linking Tumor Microenvironment to Plasticity of Cancer Stem Cells: Mechanisms and Application in Cancer Therapy

Cancer stem cells (CSCs) are a minority subset of cancer cells that can drive tumor initiation, promote tumor progression, and induce drug resistance. CSCs are difficult to eliminate by conventional therapies and eventually mediate tumor relapse and metastasis. Moreover, recent studies have shown that CSCs display plasticity that renders them to alter their phenotype and function. Consequently, the varied phenotypes result in varied tumorigenesis, dissemination, and drug-resistance potential, thereby adding to the complexity of tumor heterogeneity and further challenging clinical management of cancers. In recent years, tumor microenvironment (TME) has become a hotspot in cancer research owing to its successful application in clinical tumor immunotherapy. Notably, emerging evidence shows that the TME is involved in regulating CSC plasticity. TME can activate stemness pathways and promote immune escape through cytokines and exosomes secreted by immune cells or stromal cells, thereby inducing non-CSCs to acquire CSC properties and increasing CSC plasticity. However, the relationship between TME and plasticity of CSCs remains poorly understood. In this review, we discuss the emerging investigations on TME and CSC plasticity to illustrate the underlying mechanisms and potential implications in suppressing cancer progression and drug resistance. We consider that this review can help develop novel therapeutic strategies by taking into account the interlink between TME and CSC plasticity.

Multifunctional Role of Astrocyte Elevated Gene-1 (AEG-1) in Cancer: Focus on Drug Resistance

Simple Summary

Chemotherapy is a major mode of treatment for cancers. However, cancer cells adapt to survive in stressful conditions and in many cases, they are inherently resistant to chemotherapy. Additionally, after initial response to chemotherapy, the surviving cancer cells acquire new alterations making them chemoresistant. Genes that help adapt the cancer cells to cope with stress often contribute to chemoresistance and one such gene is Astrocyte elevated gene-1 (AEG-1). AEG-1 levels are increased in all cancers studied to date and AEG-1 contributes to the development of highly aggressive, metastatic cancers. In this review, we provide a comprehensive description of the mechanism by which AEG-1 augments tumor development with special focus on its ability to regulate chemoresistance. We also discuss potential ways to inhibit AEG-1 to overcome chemoresistance.

Abstract

Cancer development results from the acquisition of numerous genetic and epigenetic alterations in cancer cells themselves, as well as continuous changes in their microenvironment. The plasticity of cancer cells allows them to continuously adapt to selective pressures brought forth by exogenous environmental stresses, the internal milieu of the tumor and cancer treatment itself. Resistance to treatment, either inherent or acquired after the commencement of treatment, is a major obstacle an oncologist confronts in an endeavor to efficiently manage the disease. Resistance to chemotherapy, chemoresistance, is an important hallmark of aggressive cancers, and driver oncogene-induced signaling pathways and molecular abnormalities create the platform for chemoresistance. The oncogene Astrocyte elevated gene-1/Metadherin (AEG-1/MTDH) is overexpressed in a diverse array of cancers, and its overexpression promotes all the hallmarks of cancer, such as proliferation, invasion, metastasis, angiogenesis and chemoresistance. The present review provides a comprehensive description of the molecular mechanism by which AEG-1 promotes tumorigenesis, with a special emphasis on its ability to regulate chemoresistance.

Roles Played by YY1 in Embryonic, Adult and Cancer Stem Cells

Accumulating evidence strongly indicates that the presence of cancer stem cells (CSCs) leads to the emergence of worse clinical scenarios, such as chemo- and radiotherapy resistance, metastasis, and cancer recurrence. CSCs are a highly tumorigenic population characterized by self-renewal capacity and differentiation potential. Thus, CSCs establish a hierarchical intratumor organization that enables tumor adaptation to evade the immune response and resist anticancer therapy. YY1 functions as a transcription factor, RNA-binding protein, and 3D chromatin regulator. Thus, YY1 has multiple effects and regulates several molecular processes. Emerging evidence indicates that the development of lethal YY1-mediated cancer phenotypes is associated with the presence of or enrichment in cancer stem-like cells. Therefore, it is necessary to investigate whether and to what extent YY1 regulates the CSC phenotype. Since CSCs mirror the phenotypic behavior of stem cells, we initially describe the roles played by YY1 in embryonic and adult stem cells. Next, we scrutinize evidence supporting the contributions of YY1 in CSCs from a number of various cancer types. Finally, we identify new areas for further investigation into the YY1-CSCs axis, including the participation of YY1 in the CSC niche.

Autophagy, an accomplice or antagonist of drug resistance in HCC?

Hepatocellular carcinoma (HCC) is a highly lethal malignancy characterized by poor prognosis and a low 5-year survival rate. Drug treatment is proving to be effective in anti-HCC. However, only a small number of HCC patients exhibit sensitive responses, and drug resistance occurs frequently in advanced patients. Autophagy, an evolutionary process responsible for the degradation of cellular substances, is closely associated with the acquisition and maintenance of drug resistance for HCC. This review focuses on autophagic proteins and explores the intricate relationship between autophagy and cancer stem cells, tumor-derived exosomes, and noncoding RNA. Clinical trials involved in autophagy inhibition combined with anticancer drugs are also concerned.

Inhibition of Bone Morphogenetic Protein 2 Suppresses the Stemness Maintenance of Cancer Stem Cells in Hepatocellular Carcinoma via the MAPK/ERK Pathway

Background

Hepatocellular carcinoma (HCC) remains a life-threatening malignant tumor. Cancer stem cells (CSCs) harbor tumor-initiating capacity and can be used as a therapeutic target for human malignancies. Bone morphogenetic proteins (BMPs) play a regulatory role in CSCs. This study investigated the role and mechanism of BMP2 in CSCs in HCC.

Methods

BMP2 expression in HCC tissues and cells, and CSCs from HepG2 cells and SMMC7721 cells (HepG2-CSCs and SMMC7721-CSCs) was measured. The association between BMP2 expression and prognosis of HCC patients was analyzed. CSCs were interfered with BMP2 to evaluate the abilities of colony and tumor sphere formation, levels of stemness-related markers, epithelial-mesenchymal transition (EMT), and invasion and migration. Levels of MAPK/ERK pathway-related proteins in HepG2-CSCs were detected after BMP2 knockdown. The effect of the activated MAPK/ERK pathway on HepG2-CSCs was assessed. Finally, the effect of BMP2 inhibition on CSCs in HCC was verified in vivo.

Results

BMP2 showed obvious upregulation in HCC tissues and cells and was further upregulated in CSCs in HCC, with its higher expression indicative of worse prognosis. Silencing BMP2 inhibited colony and tumor sphere formation, levels of stemness-related markers, as well as EMT, invasion and migration of HepG2-CSCs and SMMC7721-CSCs. The MAPK/ERK pathway was suppressed after BMP2 knockdown, and its activation reversed the inhibitory effect of shBMP2 on hepatic CSCs. BMP2 accelerated tumor growth and EMT of CSCs in HCC in vivo.

Conclusion

We concluded that BMP2 knockdown inhibited the EMT, proliferation and invasion of CSCs in HCC, thereby hindering the stemness maintenance via suppressing the MAPK/ERK pathway.

Targeting Ca2+ Signaling in the Initiation, Promotion and Progression of Hepatocellular Carcinoma

Simple Summary

Liver cancer (hepatocellular carcinoma) is a significant health burden worldwide. It is often not detected until at an advanced stage when there are few treatment options available. Changes in calcium concentrations within liver cancer cells are essential for regulating their growth, death, and migration (metastasis). Our aim was to review published papers which have identified proteins involved in calcium signaling as potential drug targets for the treatment of liver cancer. About twenty calcium signaling proteins were identified, including those involved in regulating calcium concentrations in the cytoplasm, endoplasmic reticulum and mitochondria. A few of these have turned out to be sites of action of natural products previously known to inhibit liver cancer. More systematic studies are now needed to determine which calcium signaling proteins might be used clinically for treatment of liver cancer, especially advanced stage cancers and those resistant to inhibition by current drugs.

Abstract

Hepatocellular carcinoma (HCC) is a considerable health burden worldwide and a major contributor to cancer-related deaths. HCC is often not noticed until at an advanced stage where treatment options are limited and current systemic drugs can usually only prolong survival for a short time. Understanding the biology and pathology of HCC is a challenge, due to the cellular and anatomic complexities of the liver. While not yet fully understood, liver cancer stem cells play a central role in the initiation and progression of HCC and in resistance to drugs. There are approximately twenty Ca²⁺-signaling proteins identified as potential targets for therapeutic treatment at different stages of HCC. These potential targets include inhibition of the self-renewal properties of liver cancer stem cells; HCC initiation and promotion by hepatitis B and C and non-alcoholic fatty liver disease (principally involving reduction of reactive oxygen species); and cell proliferation, tumor growth, migration and metastasis. A few of these Ca²⁺-signaling pathways have been identified as targets for natural products previously known to reduce HCC. Promising Ca²⁺-signaling targets include voltage-operated Ca²⁺ channel proteins (liver cancer stem cells), inositol trisphosphate receptors, store-operated Ca²⁺ entry, TRP channels, sarco/endoplasmic reticulum (Ca²⁺+Mg²⁺) ATP-ase and Ca²⁺/calmodulin-dependent protein kinases. However, none of these Ca²⁺-signaling targets has been seriously studied any further than laboratory research experiments. The future application of more systematic studies, including genomics, gene expression (RNA-seq), and improved knowledge of the fundamental biology and pathology of HCC will likely reveal new Ca²⁺-signaling protein targets and consolidate priorities for those already identified.

MicroRNAs Modulate Drug Resistance-Related Mechanisms in Hepatocellular Carcinoma

Primary liver cancer [hepatocellular carcinoma (HCC)] is one of the most common malignant tumors worldwide, causing serious health threats because of its high morbidity and mortality, rapid growth, and strong invasiveness. Patients with HCC frequently develop resistance to the current chemotherapeutic drugs, and this is largely attributed to the high-level heterogeneity of the tumor tissue. MicroRNAs (miRNAs) are a group of master regulators for multiple physiological and pathological processes and play important roles in the tumorigenesis. More recent studies have indicated that miRNAs also play a non-negligible role in the development of drug resistance in liver cancer. In this review, we summarize the data from the latest studies on the mechanisms of drug resistance in liver cancer, including autophagy, membrane transporters, epithelial-mesenchymal transitions (EMTs), tumor microenvironment, and genes and proteins that are associated with apoptosis. The data herein will provide valuable information for the development of novel approaches to tackle drug resistance in the management of liver cancer.