Targeting cancer stem cells in cholangiocarcinoma (Review)

A live single-cell reporter system reveals drug-induced plasticity of a cancer stem cell-like population in cholangiocarcinoma

Cancer stem cells (CSC) play an important role in carcinogenesis and are acknowledged to be responsible for chemoresistance in cholangiocarcinoma (CCA). Studying CCA CSC has been challenging, due to lack of consensus CSC markers, and to their plastic nature. Since dual expression of the core pluripotent factors SOX2/OCT4 has been shown to correlate with poor outcome in CCA patients, we selected the SOX2/OCT4 activating short half-life GFP-based live reporter (SORE6-dsCopGFP) to study CSC dynamics at the single-cell level. Transduction of five human CCA cell lines resulted in the expression of 1.8-13.1% GFP-positive (SORE6POS) cells. By live imaging, we found that SORE6POS CCA cells possess self-renewal capacity and that they can be induced to differentiate. Significantly, the SORE6POS cells were highly tumorigenic, both in vitro and in vivo, thus implicating the characteristics of primary CSCs. When we then analyzed for selected CSC-related markers, we found that the majority of both CD133+/CD44+, and CD133+/LGR5+ CCA cells were SORE6POS cells. Exposing transduced cells to standard CCA chemotherapy revealed higher growth rate inhibition at 50% (GR50s) for SORE6POS cells compared to GFP-negative (SORE6NEG) ones indicating that these CSC-like cells were more resistant to the treatment. Moreover, the chemotherapy induced SORE6POS from SORE6NEG cells, while retaining the existing SORE6POS population. Finally, treatment of transduced cells with CDK4/6 inhibitors in vitro for 3 days resulted in a lowered CSC number in the culture. Thus, applying a live reporter system allowed us to elucidate the stem cell diversity and drug-induced plasticity of CCA CSCs. These findings have clear implications for future management of such patients.

Regulation of Hippo-YAP signaling axis by Isoalantolactone suppresses tumor progression in cholangiocarcinoma

Cholangiocarcinoma (CCA) is a devastating malignancy characterized by aggressive tumor growth and limited treatment options. Dysregulation of the Hippo signaling pathway and its downstream effector, Yes-associated protein (YAP), has been implicated in CCA development and progression. In this study, we investigated the effects of Isoalantolactone (IALT) on CCA cells to elucidate its effect on YAP activity and its potential clinical significance. Our findings demonstrate that IALT exerts cytotoxic effects, induces apoptosis, and modulates YAP signaling in SNU478 cells. We further confirmed the involvement of the canonical Hippo pathway by generating LATS1/LATS2 knockout cells, highlighting the dependence of IALT-mediated apoptosis and YAP phosphorylation on the Hippo-LATS signaling axis. In addition, IALT suppressed cell growth and migration, partially dependent on YAP-TEAD activity. These results provide insights into the therapeutic potential of targeting YAP in CCA and provide a rationale for developing of YAP-targeted therapies for this challenging malignancy.

LOXL1-AS1 inhibits JAK2 ubiquitination and promotes cholangiocarcinoma progression through JAK2/STAT3 signaling

This study thoroughly investigated the role of the long non-coding RNA LOXL1-AS1 in the pathogenesis of cholangiocarcinoma (CCA). Through bioinformatics analysis and tissue samples validation, the study found that LOXL1-AS1 was significantly elevated in CCA, with its high expression closely tied to clinical pathological features and prognosis. In vitro and in vivo experiments revealed that LOXL1-AS1 was crucial in regulating CCA cell apoptosis, proliferation, migration, and invasion. Further investigations using FISH, subcellular localization experiments, RNA pull down, and RIP uncovered that LOXL1-AS1 primarily resided in the cytoplasm and influenced CCA progression by modulating the JAK2/STAT3 signaling pathway. Notably, LOXL1-AS1 might regulate the activity of JAK2 through modulating its ubiquitination and degradation. YY1 had also been found to act as an upstream transcription factor of LOXL1-AS1 to impact CCA cell malignancy. These findings shed light on the pivotal role of LOXL1-AS1 in CCA and offered potential directions for novel therapeutic strategies, providing a fresh perspective on tumor pathogenesis.

Single-cell RNA sequencing reveals cancer stem-like cells and dynamics in tumor microenvironment during cholangiocarcinoma progression

Cholangiocarcinoma is a malignancy of the bile ducts that is driven by activities of cancer stem-like cells and characterized by a heterogeneous tumor microenvironment. To better understand the transcriptional profiles of cancer stem-like cells and dynamics in the tumor microenvironment during the progression of cholangiocarcinoma, we performed single-cell RNA analysis on cells collected from three different timepoints of tumorigenesis in a YAP/AKT mouse model. Bulk RNA sequencing data from TCGA (The Cancer Genome Atlas program) and ICGC cohorts were used to verify and support the finding. In vitro and in vivo experiments were performed to assess the stemness of cancer stem-like cells. We identified Tm4sf1high malignant cells as cancer stem-like cells. Across timepoints of cholangiocarcinoma formation in YAP/AKT mice, we found dynamic change in cancer stem-like cell/stromal/immune cell composition. Nevertheless, the dynamic interaction among cancer stem-like cells, immune cells, and stromal cells at different timepoints was elaborated. Collectively, these data serve as a useful resource for better understanding cancer stem-like cell and malignant cell heterogeneity, stromal cell remodeling, and immune cell reprogramming. It also sheds new light on transcriptomic dynamics during cholangiocarcinoma progression at single-cell resolution.

HELLS modulates the stemness of intrahepatic cholangiocarcinoma through promoting senescence-associated secretory phenotype

The senescence-associated secretory phenotype (SASP) is closely associated with the tumorigenesis and progression of intrahepatic cholangiocarcinoma (ICC). However, it remains unclear its relation to stemness of ICC. In the study, the stemness indices of ICC were calculated using one-class linear regression (OCLR) and single-sample gene set enrichment analysis (ssGSEA) algorithms. A total of 14 senescence-related stemness genes (SRSGs) were identified using Pearson correlation analysis in ICC. Subsequently, a SRSGs-related classification was established using a consensus clustering for ICC. Different types of ICC exhibit distinct prognosis, immunity, metabolisms, and oncogenic signatures. Additionally, we constructed a risk score model for ICC using principal component analysis (PCA). The risk score was positively correlated with stemness, immune infiltration, metabolisms and oncogenic signatures, but negatively with prognosis in ICC. Patients with a high risk score may respond well to immunotherapy. Furthermore, we employed 3D fibrin gels to select tumor-repopulating cells (TRC) with stemness features. We found that HELLS, belonging to the 14 SRSGs, was up-regulated in ICC-TRC. And silencing HELLS significantly reduced the colony size, inhibited migration and invasion, and attenuated SASP in ICC-TRC. In summary, we provided a novel classification and risk score for ICC and uncovered a molecular mechanism via which CSLCs could obtain an active SASP.

RAB6A functions as a critical modulator of the stem-like subsets in cholangiocarcinoma

RAB6A is a member of RAB GTPase family and plays an important role in the targeted transport of neurotrophic receptors and inflammatory cytokines. RAB6A-mediated secretory pathway is involved in many physiological and pathological processes. Defects in RAB6A-mediated secretory pathway may lead to the development of many diseases, including cancer. However, its role in cholangiocarcinoma (CCA) has not yet been revealed. We explored the regulatory role of RAB6A in the stem-like subsets of CCA. We showed that RAB6A knockdown (KD) impedes cancer stem cells (CSCs) properties and epithelial-mesenchymal transition in vitro and that suppression of RAB6A inhibits tumor growth in vivo. We screened target cargos of RAB6A in CCA cells and identified a extracellular matrix component as the target cargo. RAB6A binds directly to OPN, and RAB6A KD suppressed OPN secretion and inhibited the interaction between OPN and αV integrin receptor. Moreover, RAB6A KD inhibited the AKT signaling pathway, which is a downstream effector of the integrin receptor signaling. In addition, shRNA targeting OPN blocked endogenous expression of OPN and consequently weakened CSCs properties in RAB6A-formed spheres. Similarly, inhibitor of AKT signaling, MK2206 also impedes oncogenic function of RAB6A in the stem-like subsets of CCA cells. In conclusion, our findings showed that RAB6A sustains CSCs phenotype maintenance by modulating the secretion of OPN and consequentially activating the downstream AKT signaling pathway. Targeting the RAB6A/OPN axis may be an effective strategy for CCA therapy.

Overexpression of KiSS1 Induces the Proliferation of Hepatocarcinoma and Increases Metastatic Potential by Increasing Migratory Ability and Angiogenic Capacity

Liver cancer has a high prevalence, with majority of the cases presenting as hepatocellular carcinoma (HCC). The prognosis of metastatic HCC has hardly improved over the past decade, highlighting the necessity for liver cancer research. Studies have reported the ability of the KiSS1 gene to inhibit the growth or metastasis of liver cancer, but contradictory research results are also emerging. We, therefore, sought to investigate the effects of KiSS1 on growth and migration in human HCC cells. HepG2 human HCC cells were infected with lentivirus particles containing KiSS1. The overexpression of KiSS1 resulted in an increased proliferation rate of HCC cells. Quantitative polymerase chain reaction and immunoblotting revealed increased Akt activity, and downregulation of the G1/S phase cell cycle inhibitors. A significant increase in tumor spheroid formation with upregulation of β-catenin and CD133 was also observed. KiSS1 overexpression promoted the migratory, invasive ability, and metastatic capacity of the hepatocarcinoma cell line, and these effects were associated with changes in the expressions of epithelial mesenchymal transition (EMT)-related genes such as E-cadherin, N-cadherin, and slug. KiSS1 overexpression also resulted in dramatically increased tumor growth in the xenograft mouse model, and upregulation of proliferating cell nuclear antigen (PCNA) and Ki-67 in the HCC tumors. Furthermore, KiSS1 increased the angiogenic capacity by upregulation of the vascular endothelial growth factor A (VEGF-A) and CD31. Based on these observations, we infer that KiSS1 not only induces HCC proliferation, but also increases the metastatic potential by increasing the migratory ability and angiogenic capacity.

FBXO31 sensitizes cancer stem cells-like cells to cisplatin by promoting ferroptosis and facilitating proteasomal degradation of GPX4 in cholangiocarcinoma

BACKGROUND & AIMS

Cholangiocarcinoma (CCA) is a malignant tumour originating from the biliary epithelium that easily infiltrates, metastasizes and recurs. The deficiency of FBXO31 facilitates the initiation and progression of several types of cancer. However, the involvement of FBXO31 in CCA progression has remained unclear.

METHODS

qRT-PCR was used to detect the expression of FBXO31 in CCA. The biological functions of FBXO31 were confirmed in vivo and in vitro. Sphere formation and flow cytometry were used to identify the stem cell properties of CCA.

RESULTS

FBXO31 is downregulated in CCA and that deficiency of FBXO31 is associated with the TNM stage of CCA. Functional studies showed FBXO31 inhibits cell growth, migration, invasion, cancer stem cell (CSC) properties and epithelial-mesenchymal transition (EMT) in vitro and impedes tumour growth in vivo. In addition, overexpression of FBXO31 increases the cisplatin (CDDP) sensitivity of CCA cells. RNA-sequencing analysis revealed that FBXO31 is involved in redox biology and metal ion metabolism in CCA cells during CDDP treatment. Further studies revealed that FBXO31 enhances ferroptosis induced by CDDP in CCA and CSC-like cells. FBXO31 enhances ubiquitination of glutathione peroxidase 4 (GPX4), which leads to proteasomal degradation of GPX4. Moreover, overexpression of GPX4 compromises the promoting effects of FBXO31 on CDDP-induced ferroptosis in CCA and CSC-like cells.

CONCLUSIONS

Our studies indicate that FBXO31 functions as a tumour suppressor in CCA and sensitizes CSC-like cells to CDDP by promoting ferroptosis and facilitating the proteasomal degradation of GPX4.

MDACT: A New Principle of Adjunctive Cancer Treatment Using Combinations of Multiple Repurposed Drugs, with an Example Regimen

In part one of this two-part paper, we present eight principles that we believe must be considered for more effective treatment of the currently incurable cancers. These are addressed by multidrug adjunctive cancer treatment (MDACT), which uses multiple repurposed non-oncology drugs, not primarily to kill malignant cells, but rather to reduce the malignant cells' growth drives. Previous multidrug regimens have used MDACT principles, e.g., the CUSP9v3 glioblastoma treatment. MDACT is an amalgam of (1) the principle that to be effective in stopping a chain of events leading to an undesired outcome, one must break more than one link; (2) the principle of Palmer et al. of achieving fractional cancer cell killing via multiple drugs with independent mechanisms of action; (3) the principle of shaping versus decisive operations, both being required for successful cancer treatment; (4) an idea adapted from Chow et al., of using multiple cytotoxic medicines at low doses; (5) the idea behind CUSP9v3, using many non-oncology CNS-penetrant drugs from general medical practice, repurposed to block tumor survival paths; (6) the concept from chess that every move creates weaknesses and strengths; (7) the principle of mass-by adding force to a given effort, the chances of achieving the goal increase; and (8) the principle of blocking parallel signaling pathways. Part two gives an example MDACT regimen, gMDACT, which uses six repurposed drugs-celecoxib, dapsone, disulfiram, itraconazole, pyrimethamine, and telmisartan-to interfere with growth-driving elements common to cholangiocarcinoma, colon adenocarcinoma, glioblastoma, and non-small-cell lung cancer. gMDACT is another example of-not a replacement for-previous multidrug regimens already in clinical use, such as CUSP9v3. MDACT regimens are designed as adjuvants to be used with cytotoxic drugs.

Characterization of Immunogenicity of Malignant Cells with Stemness in Intrahepatic Cholangiocarcinoma by Single-Cell RNA Sequencing

Cancer stem cells (CSCs) are responsible for long-term maintenance of tumors and thought to play a role in treatment resistance. The interaction between stemness and immunogenicity of CSCs in the intrahepatic cholangiocarcinoma (iCCA) is largely unknown. Here, we used single-cell transcriptomic data to study immunogenicity of malignant cells in human iCCA. Using an established computerized method CytoTRACE, we found significant heterogeneity in stemness/differentiation states among malignant cells. We demonstrated that the high stemness malignant cells express much lower levels of major histocompatibility complex II molecules when compared to low stemness malignant cells, suggesting a role of immune evasion in high stemness malignant cells. In addition, high stemness malignant iCCA cells exhibited significant expression of certain cytokine members, including CCL2, CCL20, CXCL1, CXCL2, CXCL6, CXCL8, TNFRSF12A, and IL6ST, indicating communication with surrounding immune cells. These results indicate that high stemness malignant cells retain their intrinsic immunological feature that facilitate the escape of immune surveillance.

Antitumor activity of T cells secreting αCD133-αCD3 bispecific T-cell engager against cholangiocarcinoma

Cholangiocarcinoma (CCA) is a lethal cancer of bile duct epithelial cells with a high mortality rate and limited therapeutic options. An effective treatment is, therefore, urgently needed to improve treatment outcomes for these patients. To develop a new therapeutic option, we engineered T cells secreting αCD133-αCD3 bispecific T-cell engager and evaluated their antitumor effects against CD133-expressing CCA cells. The cDNA encoding αCD133-αCD3 bispecific T-cell engager (αCD133-αCD3-ENG) was cloned into pCDH lentiviral construct and its expression was tested in Lenti-X 293T cells. T cells from healthy donors were then transduced with engineered lentiviruses to create T cells secreting αCD133-αCD3 engager to evaluate their antitumor activities. The average transduction efficiency into T cells was approximately 60.03±21.65%. In the co-culture system containing T cells secreting αCD133-αCD3 engager (as effector cells) and mWasabi-luciferase-expressing CCA cells (KKU-100 and KKU-213A; as target cells), the effector T cells exhibited significantly higher cytolytic activities against the target CCA cells (49.0±9.76% and 64.10±13.18%, respectively) than those observed against the untransduced T cells (10.97±10.65%; p = 0.0103 and 9.80±11.05%; p = 0.0054) at an effector-to-target ratio of 5:1. In addition, the secreted αCD133-αCD3 engager significantly redirected both transduced T cells and bystander T cells to kill the target CCA cells (up to 73.20±1.68%; p<0.05). Moreover, the transduced and bystander T cells could kill the target CCA spheroids at a rate approximately 5-fold higher than that of the no treatment control condition (p = 0.0011). Our findings demonstrate proof-of-principle that T cells secreting αCD133-αCD3 engager can be an alternative approach to treating CD133-positive CCA, and they pave the way for future in vivo study and clinical trials.

Targeting key proteins involved in transcriptional regulation for cancer therapy: Current strategies and future prospective

The key proteins involved in transcriptional regulation play convergent roles in cellular homeostasis, and their dysfunction mediates aberrant gene expressions that underline the hallmarks of tumorigenesis. As tumor progression is dependent on such abnormal regulation of transcription, it is important to discover novel chemical entities as antitumor drugs that target key tumor-associated proteins involved in transcriptional regulation. Despite most key proteins (especially transcription factors) involved in transcriptional regulation are historically recognized as undruggable targets, multiple targeting approaches at diverse levels of transcriptional regulation, such as epigenetic intervention, inhibition of DNA-binding of transcriptional factors, and inhibition of the protein-protein interactions (PPIs), have been established in preclinically or clinically studies. In addition, several new approaches have recently been described, such as targeting proteasomal degradation and eliciting synthetic lethality. This review will emphasize on accentuating these developing therapeutic approaches and provide a thorough conspectus of the drug development to target key proteins involved in transcriptional regulation and their impact on future oncotherapy.

The NOP14 nucleolar protein suppresses the function and stemness of melanoma stem-like cells through Wnt/beta-catenin signaling inactivation

Cancer stem cells (CSCs) are closely related to tumor occurrence, development, metastasis, drug resistance, and recurrence. The role of CSCs in melanoma is poorly understood. Our previous studies suggested that the NOP14 nucleolar protein (NOP14) is involved in melanoma pathogenesis regulation. Importantly, NOP14 overexpression inhibits the Wnt/beta (β)-catenin signaling pathway, an important mechanism regulating CSCs stemness. Therefore, in this study, we aimed to explore the role of NOP14 in the stemness and function of CSCs in melanoma in vitro. CD133, a stem cell marker, was used to identify melanoma stem-like cells (SLCs). NOP14 overexpression subsequently decreased the proportion of CD133⁺ SLCs, impaired the colony-forming capabilities, and downregulated the expression of Nanog, SOX2, and OCT4 stem cell markers in A375 and A875 cells, suggesting that NOP14 suppresses the stemness of melanoma SLCs. NOP14 overexpression suppressed the migration, invasion, and angiogenesis-inducing ability of A375-SLCs and A875-SLCs. NOP14 overexpression also inactivated Wnt/β-catenin signaling in melanoma CD133⁺ SLCs. The Wnt signaling activator BML-284 alleviated the effect of NOP14 overexpression on the stemness and function of melanoma CSCs. In conclusion, NOP14 suppresses the stemness and function of melanoma SLCs by inactivating Wnt/β-catenin signaling. Thus, NOP14 is a novel target for CSC treatment in melanoma.

Abbreviations: CSCs, cancer stem cells; SLCs, stem-like cells; NOP14, NOP14 nucleolar protein; SCID, severe combined immunodeficiency; β-catenin, beta-catenin; lv-NOP14, lentivirals expressing NOP14; PBS, phosphate buffer saline; HUVECs, human umbilical vein endothelial cells.

Drug Discovery in Liver Disease Using Kinome Profiling

The liver is one of the most important organs, playing critical roles in maintaining biochemical homeostasis. Accordingly, disease of the liver is often debilitating and responsible for untold human misery. As biochemical nexus, with kinases being master regulators of cellular biochemistry, targeting kinase enzymes is an obvious avenue for treating liver disease. Development of such therapy, however, is hampered by the technical difficulty of obtaining comprehensive insight into hepatic kinase activity, a problem further compounded by the often unique aspects of hepatic kinase activities, which makes extrapolations from other systems difficult. This consideration prompted us to review the current state of the art with respect to kinome profiling approaches towards the hepatic kinome. We observe that currently four different approaches are available, all showing significant promise. Hence we postulate that insight into the hepatic kinome will quickly increase, leading to rational kinase-targeted therapy for different liver diseases.