Salinomycin inhibits metastatic colorectal cancer growth and interferes with Wnt/β-catenin signaling in CD133+ human colorectal cancer cells

GTP binding protein 2 maintains the quiescence, self-renewal, and chemoresistance of mouse colorectal cancer stem cells via promoting Wnt signaling activation

Colorectal cancer (CRC) is one of the most common cancers and the second most deadly cancer across the globe. Colorectal cancer stem cells (CCSCs) fuel CRC growth, metastasis, relapse, and chemoresistance. A complete understanding of the modulatory mechanisms of CCSC biology is essential for developing efficacious CRC treatment. In the current study, we characterized the expression and function of GTP binding protein 2 (GTPBP2) in a chemical-induced mouse CRC model. We found that GTPBP2 was expressed at a higher level in CD133+CD44+ CCSCs compared with other CRC cells. Using a lentivirus-based Cas9/sgRNA system, GTPBP2 expression was ablated in CRC cells in vitro. GTPBP2 deficiency caused the following effects on CCSCs: 1) Significantly accelerating proliferation and increasing the proportions of cells at G1, S, and G2/M phase; 2) Impairing resistance to 5-Fluorouracil; 3) Weakening self-renewal but not impacting cell migration. In addition, GTPBP2 deficiency remarkably decreased β-catenin expression while increasing β-catenin phosphorylation in CCSCs. These effects of GTPBP2 were present in CCSCs but not in other CRC cell populations. The Wnt agonist SKL2001 completely abolished these changes in GTPBP2-deficient CCSCs. When GTPBP2-deficient CCSCs were implanted in nude mice, they exhibited consistent changes compared with GTPBP2-expressing CCSCs. Collectively, this study indicates that GTPBP2 positively modulates Wnt signaling to reinforce the quiescence, self-renewal, and chemoresistance of mouse CCSCs. Therefore, we disclose a novel mechanism underlying CCSC biology and GTPBP2 could be a therapeutic target in future CRC treatment.

Inhibition of Wnt/β-catenin signaling by monensin in cervical cancer

The challenging clinical outcomes associated with advanced cervical cancer underscore the need for a novel therapeutic approach. Monensin, a polyether antibiotic, has recently emerged as a promising candidate with anti-cancer properties. In line with these ongoing efforts, our study presents compelling evidence of monensin's potent efficacy in cervical cancer. Monensin exerts a pronounced inhibitory impact on proliferation and anchorage-independent growth. Additionally, monensin significantly inhibited cervical cancer growth in vivo without causing any discernible toxicity in mice. Mechanism studies show that monensin's anti-cervical cancer activity can be attributed to its capacity to inhibit the Wnt/β-catenin pathway, rather than inducing oxidative stress. Monensin effectively reduces both the levels and activity of β-catenin, and we identify Akt, rather than CK1, as the key player involved in monensin-mediated Wnt/β-catenin inhibition. Rescue studies using Wnt activator and β-catenin-overexpressing cells confirmed that β-catenin inhibition is the mechanism of monensin's action. As expected, cervical cancer cells exhibiting heightened Wnt/β-catenin activity display increased sensitivity to monensin treatment. In conclusion, our findings provide pre-clinical evidence that supports further exploration of monensin's potential for repurposing in cervical cancer therapy, particularly for patients exhibiting aberrant Wnt/β-catenin activation.

EGFR-targeting peptide conjugated polymer-lipid hybrid nanoparticles for delivery of salinomycin to osteosarcoma

CONTEXT

Salinomycin (SAL) is a chemotherapeutic drug with anti-osteosarcoma efficacy, but its hydrophobic properties have hindered its application. Nanoparticles have been widely used as drug carriers to improve the solubility of hydrophobic drugs. The dodecapeptide GE11 has been shown to have great binding affinity to the epidermal growth factor receptor (EGFR), which is highly overexpressed in osteosarcoma.

MATERIALS AND METHODS

We designed novel SAL-loaded GE11-conjugated polymer-lipid hybrid nanoparticles (GE11-NPs-SAL) to target osteosarcoma. The characterization and antitumor activity of GE11-NPs-SAL were evaluated both in vitro and in vivo.

RESULTS

The results showed that GE11-NPs-SAL had a size of ~100 nm with a high encapsulation efficacy of ~80%. Compared with the non-targeted nanoparticles, GE11-NPs-SAL showed increased internalization in osteosarcoma cells and improved therapeutic efficacy in osteosarcoma both in vitro and in vivo.

CONCLUSIONS

GE11-NPs-SAL is a promising treatment for osteosarcoma.

The role and implication of autophagy in cholangiocarcinoma

Cholangiocarcinoma (CCA) is a malignant tumor that originates from the biliary epithelial cells. It is characterized by a difficult diagnosis and limited treatment options. Autophagy is a cellular survival mechanism that maintains nutrient and energy homeostasis and eliminates intracellular pathogens. It is involved in various physiological and pathological processes, including the development of cancer. However, the role, mechanism, and potential therapeutic targets of autophagy in CCA have not been thoroughly studied. In this review, we introduce the classification, characteristics, process, and related regulatory genes of autophagy. We summarize the regulation of autophagy on the progression of CCA and collect the latest research progress on some autophagy modulators with clinical potential in CCA. In conclusion, combining autophagy modulators with immunotherapy, chemotherapy, and targeted therapy has great potential in the treatment of CCA. This combination may be a potential therapeutic target for CCA in the future.

GART Functions as a Novel Methyltransferase in the RUVBL1/β-Catenin Signaling Pathway to Promote Tumor Stemness in Colorectal Cancer

Tumor stemness is associated with the recurrence and incurability of colorectal cancer (CRC), which lacks effective therapeutic targets and drugs. Glycinamide ribonucleotide transformylase (GART) fulfills an important role in numerous types of malignancies. The present study aims to identify the underlying mechanism through which GART may promote CRC stemness, as to developing novel therapeutic methods. An elevated level of GART is associated with poor outcomes in CRC patients and promotes the proliferation and migration of CRC cells. CD133+ cells with increased GART expression possess higher tumorigenic and proliferative capabilities both in vitro and in vivo. GART is identified to have a novel methyltransferase function, whose enzymatic activity center is located at the E948 site. GART also enhances the stability of RuvB-like AAA ATPase 1 (RUVBL1) through methylating its K7 site, which consequently aberrantly activates the Wnt/β-catenin signaling pathway to induce tumor stemness. Pemetrexed (PEM), a compound targeting GART, combined with other chemotherapy drugs greatly suppresses tumor growth both in a PDX model and in CRC patients. The present study demonstrates a novel methyltransferase function of GART and the role of the GART/RUVBL1/β-catenin signaling axis in promoting CRC stemness. PEM may be a promising therapeutic agent for the treatment of CRC.

Wdr5-mediated H3K4me3 coordinately regulates cell differentiation, proliferation termination, and survival in digestive organogenesis

Food digestion requires the cooperation of different digestive organs. The differentiation of digestive organs is crucial for larvae to start feeding. Therefore, during digestive organogenesis, cell identity and the tissue morphogenesis must be tightly coordinated but how this is accomplished is poorly understood. Here, we demonstrate that WD repeat domain 5 (Wdr5)-mediated H3K4 tri-methylation (H3K4me3) coordinately regulates cell differentiation, proliferation and apoptosis in zebrafish organogenesis of three major digestive organs including intestine, liver, and exocrine pancreas. During zebrafish digestive organogenesis, some of cells in these organ primordia usually undergo differentiation without apoptotic activity and gradually reduce their proliferation capacity. In contrast, cells in the three digestive organs of wdr5^-/- mutant embryos retain progenitor-like status with high proliferation rates, and undergo apoptosis. Wdr5 is a core member of COMPASS complex to implement H3K4me3 and its expression is enriched in digestive organs from 2 days post-fertilization (dpf). Further analysis reveals that lack of differentiation gene expression is due to significant decreases of H3K4me3 around the transcriptional start sites of these genes; this histone modification also reduces the proliferation capacity in differentiated cells by increasing the expression of apc to promote the degradation of β-Catenin; in addition, H3K4me3 promotes the expression of anti-apoptotic genes such as xiap-like, which modulates p53 activity to guarantee differentiated cell survival. Thus, our findings have discovered a common molecular mechanism for cell fate determination in different digestive organs during organogenesis, and also provided insights to understand mechanistic basis of human diseases in these digestive organs.

Recent advances in the development of transplanted colorectal cancer mouse models

Despite progress in prevention and treatment, colorectal cancer (CRC) remains the third most common malignancy worldwide and the second most common cause of cancer death in 2020. To evaluate various characteristics of human CRC, a variety of mouse models have been established. Transplant mouse models have distinct advantages in studying the clinical behavior and therapeutic progress of CRC. Host, xenograft, and transplantation routes are the basis of transplant mouse models. As the effects of the tumor microenvironment and the systemic environment on cancer cells are gradually revealed, 3 key elements of transplanted CRC mouse models have been revolutionized. This has led to the development of humanized mice, patient-derived xenografts, and orthotopic transplants that reflect the human systemic environment, patient's tumor of origin, and tumor growth microenvironments in immunodeficient mice, respectively. These milestone events have allowed for great progress in tumor biology and the treatment of CRC. This article reviews the evolution of these events and points out their strengths and weaknesses as innovative and useful preclinical tools to study CRC progression and metastasis and to exploit novel treatment schedules by establishing a testing platform. This review article depicts the optimal transplanted CRC mouse models and emphasizes the significance of surgical models in the study of CRC behavior and treatment response.

Salinomycin-Loaded High-Density Lipoprotein Exerts Promising Anti-Ovarian Cancer Effects by Inhibiting Epithelial-Mesenchymal Transition

Background

Effective treatments for ovarian cancer remain elusive, and survival rates have long been considered grim. Ovarian cancer stem cells (OCSCs) and epithelial–mesenchymal transition (EMT) are associated with cancer progression and metastasis, as well as drug resistance and eventual treatment failure. Salinomycin (Sal) has an extensive effect on a variety of cancer stem cells (CSCs); however, its poor water solubility and toxicity to healthy tissues at high doses limit further research into its potential as an anti-cancer drug. We proposed a therapeutic strategy by constructing a tumor-targeting carrier that mimics high-density lipoprotein (HDL) to synthesize salinomycin-loaded high-density lipoprotein (S-HDL). This strategy helps reduce the side effects of salinomycin, thereby improving its clinical benefits.

Methods

OCSCs were isolated from ovarian cancer cells (OCCs) and the uptake of HDL nanoparticles was observed using laser confocal microscopes. After the cell viability analysis revealed the inhibitory effect of S-HDL on OCCs and OCSCs, the main biological processes influenced by S-HDL were predicted with a transcriptome sequencing analysis and verified in vitro and in vivo.

Results

Cellular uptake analysis showed that the HDL delivery system was able to significantly enhance the uptake of Sal by OCCs, tentatively validating the targeting role of recombinant HDL, so that S-HDL could reduce the toxicity of Sal and increase its anti-ovarian cancer effects. Conversely, S-HDL could exert anti-ovarian cancer effects by inhibiting the proliferation of OCCs and OCSCs, promoting apoptosis, blocking EMT, and suppressing stemness and angiogenesis-related protein expression in vitro and in vivo.

Conclusion

S-HDL had stronger anti-ovarian cancer effects than unencapsulated Sal. Thus, it may be a potential agent for ovarian cancer treatment in the future.

Emerging drug targets for colon cancer: A preclinical assessment

INTRODUCTION

Colorectal cancer (CRC) is the second leading cause of cancer-related death in the United States. There have been improvements in screening, and therefore overall survival, but patients continue to present at late stages when minimal treatment options are available to them. While some targeted therapies have been introduced, their application is limited by patient-specific tumor characteristics. Additional targets for CRC in patients who present at a late stage, or who experience tumor relapse, need to be identified to continue to improve patient outcomes.

AREAS COVERED

This review focuses on emerging pathways and drug targets for the treatment of colorectal cancer. The shift to the cancer stem cell model and potential targets involving Wnt, NF-κB, phosphodiesterases, RAS, and guanylyl cyclase C, are discussed. The current utility of checkpoint inhibitors and evolving immunological options are examined.

EXPERT OPINION

Surgery and current systemic cytotoxic therapies are inadequate to appropriately treat the full spectrum of CRC, especially in those patients who present with metastatic or treatment-refractory disease. In addition to the identification of new, more generalizable targets, additional focus is being placed on novel administrations. Immuno-oncologic options and stem cell-targeting therapies for mCRC will become available to patients and may increase survival.

The Effect of Metformin on the Proliferation, Apoptosis and CD133 mRNA Expression of Colon Cancer Stem Cells by Upregulation of miR 342-3p

Objective

To explore whether metformin (MET) can affect the biological behaviour and CD133 mRNA expression of CD133⁺ colon cancer stem cells (CCSCs) through miR-342-3p.

Methods

The direct immunomagnetic bead method was used to select CD133⁺ CCSCs from the SW480 and HCT116 cell lines, and miRNA-tailing qRT-PCR was used to detect the expression changes of tumor suppressor-related miRNAs (miR-34a, miR-126, miR-143, miR-145, miR-342-3p, miR-342-5p) after MET intervention. Then, miR-342-3p with markedly significant differential expression was selected as the target miRNA. The lentiviruses LV16-hsa-miR-342-3p inhibitor and LV16-NC were used for the transfection inhibition test. CCK-8, flow cytometry, and qRT-PCR were used to detect the cell viability, apoptosis rate, and CD133 mRNA expression of CD133⁺ CCSCs.

Results

Under the high-glucose environment, the expression of tumor suppressor-related miRNAs in CCSCs changed differently (p <0.05), MET also had different effects on the expression of tumor suppressor-related miRNA under different glucose concentrations (p<0.05). Among them, MET upregulates the expression of miR-342-3p in CCSCs for the first time. The results of the lentiviruses transfection inhibition test showed that after miR-342-3p was inhibited, the cell viability and apoptosis rate of CD133⁺ CCSCs did not change significantly compared with before inhibition (p>0.05), but the expression of CD133 mRNA markedly increased (p<0.05). Meanwhile, after MET intervention, the apoptosis rate and the expression of CD133 mRNA of CD133⁺ CCSCs was significantly increased, and the proliferation of CD133⁺ CCSCs was obviously inhibited (p<0.05).

Conclusion

MET upregulating the expression of miR-342-3p may not have a significant effect on the proliferation and apoptosis of CD133⁺ CCSCs, but it can reduce the expression of CD133 mRNA in CD133⁺ CCSCs.

BCL9 regulates CD226 and CD96 checkpoints in CD8+ T cells to improve PD-1 response in cancer

To date, the overall response rate of PD-1 blockade remains unsatisfactory, partially due to limited understanding of tumor immune microenvironment (TIME). B-cell lymphoma 9 (BCL9), a key transcription co-activator of the Wnt pathway, is highly expressed in cancers. By genetic depletion and pharmacological inhibition of BCL9 in tumors, we found that BCL9 suppression reduced tumor growth, promoted CD8⁺ T cell tumor infiltration, and enhanced response to anti-PD-1 treatment in mouse colon cancer models. To determine the underlying mechanism of BCL9's role in TIME regulation, single-cell RNA-seq was applied to reveal cellular landscape and transcription differences in the tumor immune microenvironment upon BCL9 inhibition. CD155-CD226 and CD155-CD96 checkpoints play key roles in cancer cell/CD8⁺ T cell interaction. BCL9 suppression induces phosphorylation of VAV1 in CD8⁺ T cells and increases GLI1 and PATCH expression to promote CD155 expression in cancer cells. In The Cancer Genome Atlas database analysis, we found that BCL9 expression is positively associated with CD155 and negatively associated with CD226 expression. BCL9 is also linked to adenomatous polyposis coli (APC) mutation involved in patient survival following anti-PD-1 treatment. This study points to cellular diversity within the tumor immune microenvironment affected by BCL9 inhibition and provides new insights into the role of BCL9 in regulating CD226 and CD96 checkpoints.

Selective Inhibition of Esophageal Cancer Stem-like Cells with Salinomycin

BACKGROUND

Targeting Cancer Stem-Like Cells (CSLCs) can provide promising new therapeutic strategies to inhibit cancer progression, metastasis and recurrence. Salinomycin (Sal), an antibacterial ionophore, has been shown to inhibit CSCs specifically. Recently, it has been reported that Sal can destabilize TAZ, the hypo pathway transducer in CSLCs.

OBJECTIVES

Here, in the current study, we aimed to assess the differential toxicity of Sal in esophageal CSLCs and its relation to TAZ gene expression.

METHODS

The esophageal cancer cell line, KYSE-30, was used for the enrichment of CSLCs. The expression of TAZ was knocked down using specific siRNA transfection and then the cytotoxicity of Sal was measured using XTT assay. The qRT-PCR method was used for gene expression assessment and the sphere formation ability was monitored using light microscopy.

RESULTS

Our findings showed that esophageal CSLCs over-express stemness-associated genes, including SOX2, OCT4 as well as TAZ (~14 fold, P value=0.02) transcription coactivator. We found Sal can selectively inhibit KYSE-30 CSLCs viability and sphere formation ability; however, TAZ knockdown does not change its differential toxicity.

CONCLUSION

Overall, our results indicated that Sal can selectively decrease the viability of esophageal CSLCs in a TAZ-independent manner.

Radiotherapy and the gut microbiome: facts and fiction

An ever-growing body of evidence has linked the gut microbiome with both the effectiveness and the toxicity of cancer therapies. Radiotherapy is an effective way to treat tumors, although large variations exist among patients in tumor radio-responsiveness and in the incidence and severity of radiotherapy-induced side effects. Relatively little is known about whether and how the microbiome regulates the response to radiotherapy. Gut microbiota may be an important player in modulating “hot” versus “cold” tumor microenvironment, ultimately affecting treatment efficacy. The interaction of the gut microbiome and radiotherapy is a bidirectional function, in that radiotherapy can disrupt the microbiome and those disruptions can influence the effectiveness of the anticancer treatments. Limited data have shown that interactions between the radiation and the microbiome can have positive effects on oncotherapy. On the other hand, exposure to ionizing radiation leads to changes in the gut microbiome that contribute to radiation enteropathy. The gut microbiome can influence radiation-induced gastrointestinal mucositis through two mechanisms including translocation and dysbiosis. We propose that the gut microbiome can be modified to maximize the response to treatment and minimize adverse effects through the use of personalized probiotics, prebiotics, or fecal microbial transplantation. 16S rRNA sequencing is the most commonly used approach to investigate distribution and diversity of gut microbiome between individuals though it only identifies bacteria level other than strain level. The functional gut microbiome can be studied using methods involving metagenomics, metatranscriptomics, metaproteomics, as well as metabolomics. Multiple ‘-omic’ approaches can be applied simultaneously to the same sample to obtain integrated results. That said, challenges and remaining unknowns in the future that persist at this time include the mechanisms by which the gut microbiome affects radiosensitivity, interactions between the gut microbiome and combination treatments, the role of the gut microbiome with regard to predictive and prognostic biomarkers, the need for multi “-omic” approach for in-depth exploration of functional changes and their effects on host-microbiome interactions, and interactions between gut microbiome, microbial metabolites and immune microenvironment.

A perspective on medicinal chemistry approaches towards adenomatous polyposis coli and Wnt signal based colorectal cancer inhibitors

Colorectal cancer (CRC) is one of the major causes of carcinogenic mortality in numbers only after lung and breast cancers. The mutations in adenomatous polyposis coli (APC) gene leads to formation of colorectal polyps in the colonic region and which develop as a malignant tumour upon coalition with patient related risk factors. The protein-protein interaction (PPI) of APC with Asef (A Rac specific guanine nucleotide exchange factor) overwhelms the patient's conditions by rapidly spreading in the entire colorectal region. Most mutations in APC gene occur in mutated cluster region (MCR), where it specifically binds with the cytosolic β-catenin to regulate the Wnt signalling pathway required for CRC cell adhesion, invasion, progression, differentiation and stemness in initial cell cycle phages. The current broad spectrum perspective is attempted to elaborate the sources of identification, development of selective APC inhibitors by targeting emopamil-binding protein (EBP) & dehydrocholesterol reductase-7 & 24 (DHCR-7 & 24); APC-Asef, β-catenin/APC, Wnt/β-catenin, β-catenin/TCF4 PPI inhibitors with other vital Wnt signal cellular proteins and APC/Pol-β interface of colorectal cancer. In this context, this perspective would serve as a platform for design of new medicinal agents by targeting cellular essential components which could accelerate anti-colorectal potential candidates.

Salinomycin nanocrystals for colorectal cancer treatment through inhibition of Wnt/β-catenin signaling

Salinomycin (SAL) is one of the first discovered inhibitors of human cancer stem cells (CSCs), which acts via blocking the Wnt/β-catenin pathway. However, SAL has not been clinically used to treat human diseases due to its poor aqueous solubility and considerable toxicity. In this study, we developed salinomycin nanocrystals (SAL NCs) to treat colorectal cancer through the inhibitory enhancement of Wnt/β-catenin signaling. The as-prepared SAL NCs exhibited excellent size distribution, stability, and improved water solubility. In vitro cellular uptake and in vivo fluorescence imaging studies showed that SAL NCs increased cellular uptake efficiency compared with free SAL. As a result, SAL NCs exhibited significant higher cytotoxicity, 1.5-3 times better Wnt inhibitory effect, and 10 times better cancer stem cell inhibitory effect than free SAL. Furthermore, compared with free SAL, SAL NCs exhibited 2 times better anti-colon tumor effect in APC^min/+ transgenic mice through oral administration. Our results indicated that SAL NCs with enhanced cellular internalization and tumor tissue accumulation may be a promising agent for colorectal cancer management.

Napabucasin overcomes cisplatin resistance in ovarian germ cell tumor-derived cell line by inhibiting cancer stemness

Background

Cisplatin resistance of ovarian yolk sac tumors (oYST) is a clinical challenge due to dismal patient prognosis, even though the disease is extremely rare. We investigated potential association between cisplatin resistance and cancer stem cell (CSC) markers in chemoresistant oYST cells and targeting strategies to overcome resistance in oYST.

Methods

Chemoresistant cells were derived from chemosensitive human oYST cells by cultivation in cisplatin in vitro. Derivative cells were characterized by chemoresistance, functional assays, flow cytometry, gene expression and protein arrays focused on CSC markers. RNAseq, methylation and microRNA profiling were performed. Quail chorioallantoic membranes (CAM) with implanted oYST cells were used to analyze the micro-tumor extent and interconnection with the CAM. Tumorigenicity in vivo was determined on immunodeficient mouse model. Chemoresistant cells were treated by inhibitors intefering with the CSC properties to examine the chemosensitization to cisplatin.

Results

Long-term cisplatin exposure resulted in seven-fold higher IC₅₀ value in resistant cells, cross-resistance to oxaliplatin and carboplatin, and increased migratory capacity, invasiveness and tumorigenicity, associated with hypomethylation of differentially methylated genes/promotors. Resistant cells exhibited increased expression of prominin-1 (CD133), ATP binding cassette subfamily G member 2 (ABCG2), aldehyde dehydrogenase 3 isoform A1 (ALDH3A1), correlating with reduced gene and promoter methylation, as well as increased expression of ALDH1A3 and higher overall ALDH enzymatic activity, rendering them cross-resistant to DEAB, disulfiram and napabucasin. Salinomycin and tunicamycin were significantly more toxic to resistant cells. Pretreatment with napabucasin resensitized the cells to cisplatin and reduced their tumorigenicity in vivo.

Conclusions

The novel chemoresistant cells represent unique model of refractory oYST. CSC markers are associated with cisplatin resistance being possible targets in chemorefractory oYST.

Transcriptomic insight into salinomycin mechanisms in breast cancer cell lines: synergistic effects with dasatinib and induction of estrogen receptor β

BACKGROUND

Tumors are heterogeneous in nature, composed of different cell populations with various mutations and/or phenotypes. Using a single drug to encounter cancer progression is generally ineffective. To improve the treatment outcome, multiple drugs of distinctive mechanisms but complementary anticancer activities (combination therapy) are often used to enhance antitumor efficacy and minimize the risk of acquiring drug resistance. We report here the synergistic effects of salinomycin (a polyether antibiotic) and dasatinib (a Src kinase inhibitor).

METHODS

Functionally, both drugs induce cell cycle arrest, intracellular reactive oxygen species (iROS) production, and apoptosis. We rationalized that an overlapping of the drug activities should offer an enhanced anticancer effect, either through vertical inhibition of the Src-STAT3 axis or horizontal suppression of multiple pathways. We determined the toxicity induced by the drug combination and studied the kinetics of iROS production by fluorescence imaging and flow cytometry. Using genomic and proteomic techniques, including RNA-sequencing (RNA-seq), reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and Western Blot, we subsequently identified the responsible pathways that contributed to the synergistic effects of the drug combination.

RESULTS

Compared to either drug alone, the drug combination showed enhanced potency against MDA-MB-468, MDA-MB-231, and MCF-7 human breast cancer (BC) cell lines and tumor spheroids. The drug combination induces both iROS generation and apoptosis in a time-dependent manner, following a 2-step kinetic profile. RNA-seq data revealed that the drug combination exhibited synergism through horizontal suppression of multiple pathways, possibly through a promotion of cell cycle arrest at the G1/S phase via the estrogen-mediated S-phase entry pathway, and partially via the BRCA1 and DNA damage response pathway.

CONCLUSION

Transcriptomic analyses revealed for the first time, that the estrogen-mediated S-phase entry pathway partially contributed to the synergistic effect of the drug combination. More importantly, our studies led to the discoveries of new potential therapeutic targets, such as E2F2, as well as a novel drug-induced targeting of estrogen receptor β (ESR2) approach for triple-negative breast cancer treatment, currently lacking of targeted therapies.

Long Non-coding RNA TDRKH-AS1 Promotes Colorectal Cancer Cell Proliferation and Invasion Through the β-Catenin Activated Wnt Signaling Pathway

Colorectal cancer (CRC) is a common cancer worldwide, with a lower 5-years survival rate. Recently, long non-coding RNAs (lncRNAs) have been well-studied as the oncogenes or the tumor suppressors in multiple malignancies, including CRC. However, their biological functions and potential mechanisms in human cancer remain unclear. Here, we evaluated the expression of TDRKH-AS1 in CRC tissues and identified its potential targets. We found that TDRKH-AS1 is upregulated in majority of CRC patients, which is also significantly correlated with their malignant characteristics and their dismal prognoses. The high expression of TDRKH-AS1 can promote cancer cell proliferation substantially and invasion based on in vitro experiments. We also recognized that the TDRKH-AS1 targets the β-catenin in the Wnt signaling pathway to exert its carcinogenic activity. TDRKH-AS1 could serve as a promising prognostic predictor and a potential therapeutic target for further early diagnoses and treatments via a non-invasive method.

Mouse models of colorectal cancer: Past, present and future perspectives

Colorectal cancer (CRC) is the third most common diagnosed malignancy among both sexes in the United States as well as in the European Union. While the incidence and mortality rates in western, high developed countries are declining, reflecting the success of screening programs and improved treatment regimen, a rise of the overall global CRC burden can be observed due to lifestyle changes paralleling an increasing human development index. Despite a growing insight into the biology of CRC and many therapeutic improvements in the recent decades, preclinical in vivo models are still indispensable for the development of new treatment approaches. Since the development of carcinogen-induced rodent models for CRC more than 80 years ago, a plethora of animal models has been established to study colon cancer biology. Despite tenuous invasiveness and metastatic behavior, these models are useful for chemoprevention studies and to evaluate colitis-related carcinogenesis. Genetically engineered mouse models (GEMM) mirror the pathogenesis of sporadic as well as inherited CRC depending on the specific molecular pathways activated or inhibited. Although the vast majority of CRC GEMM lack invasiveness, metastasis and tumor heterogeneity, they still have proven useful for examination of the tumor microenvironment as well as systemic immune responses; thus, supporting development of new therapeutic avenues. Induction of metastatic disease by orthotopic injection of CRC cell lines is possible, but the so generated models lack genetic diversity and the number of suited cell lines is very limited. Patient-derived xenografts, in contrast, maintain the pathological and molecular characteristics of the individual patient’s CRC after subcutaneous implantation into immunodeficient mice and are therefore most reliable for preclinical drug development – even in comparison to GEMM or cell line-based analyses. However, subcutaneous patient-derived xenograft models are less suitable for studying most aspects of the tumor microenvironment and anti-tumoral immune responses. The authors review the distinct mouse models of CRC with an emphasis on their clinical relevance and shed light on the latest developments in the field of preclinical CRC models.

Overcoming Resistance to Platinum-Based Drugs in Ovarian Cancer by Salinomycin and Its Derivatives-An In Vitro Study

Polyether ionophore salinomycin (SAL) and its semi-synthetic derivatives are recognized as very promising anticancer drug candidates due to their activity against various types of cancer cells, including multidrug-resistant populations. Ovarian cancer is the deadliest among gynecologic malignancies, which is connected with the development of chemoresistant forms of the disease in over 70% of patients after initial treatment regimen. Thus, we decided to examine the anticancer properties of SAL and selected SAL derivatives against a series of drug-sensitive (A2780, SK-OV-3) and derived drug-resistant (A2780 CDDP, SK-OV-3 CDDP) ovarian cancer cell lines. Although SAL analogs showed less promising IC₅₀ values than SAL, they were identified as the antitumor agents that significantly overcome the resistance to platinum-based drugs in ovarian cancer, more potent than unmodified SAL and commonly used anticancer drugs—5-fluorouracil, gemcitabine, and cisplatin. Moreover, when compared with SAL used alone, our experiments proved for the first time increased selectivity of SAL-based dual therapy with 5-fluorouracil or gemcitabine, especially towards A2780 cell line. Looking closer at the results, SAL acted synergistically with 5-fluorouracil towards the drug-resistant A2780 cell line. Our results suggest that combinations of SAL with other antineoplastics may become a new therapeutic option for patients with ovarian cancer.

Mitochondrial Involvement in Migration, Invasion and Metastasis

Mitochondria in addition to be a main cellular power station, are involved in the regulation of many physiological processes, such as generation of reactive oxygen species, metabolite production and the maintenance of the intracellular Ca²⁺ homeostasis. Almost 100 years ago Otto Warburg presented evidence for the role of mitochondria in the development of cancer. During the past 20 years mitochondrial involvement in programmed cell death regulation has been clarified. Moreover, it has been shown that mitochondria may act as a switchboard between various cell death modalities. Recently, accumulated data have pointed to the role of mitochondria in the metastatic dissemination of cancer cells. Here we summarize the modern knowledge concerning the contribution of mitochondria to the invasion and dissemination of tumor cells and the possible mechanisms behind that and attempts to target metastatic cancers involving mitochondria.

Mechanism of a Novel Camptothecin-Deoxycholic Acid Derivate Induced Apoptosis against Human Liver Cancer HepG2 Cells and Human Colon Cancer HCT116 Cells

BACKGROUND

Camptothecin (CPT) is known as an anticancer drug in traditional Chinese medicine. However, due to the lack of targeting, low solubility, and instability of CPT, its therapeutic applications are hampered. Therefore, we synthesized a series of CPT-bile acid analogues that obtained a national patent to improve their tumour-targeting chemotherapeutic effects on liver or colon cancers. Among these analogues, the compound G2 shows high antitumor activity with enhanced liver targeting and improved oral absorption. It is significant to further investigate the possible anticancer mechanism of G2 for its further clinical research and application.

OBJECTIVE

We aimed to unearth the anticancer mechanism of G2 in HepG2 and HCT116 cells.

METHODS

Cell viability was measured using MTT assay; cell cycle, Mitochondrial Membrane Potential (MMP), and cell apoptosis were detected by flow cytometer; ROS was measured by Fluorescent Microplate Reader; the mRNA and protein levels of cell cycle-related and apoptosis-associated proteins were examined by RT-PCR and western blot, respectively.

RESULTS

We found that G2 inhibited cells proliferation of HepG2 and HCT116 remarkably in a dosedependent manner. Moreover, G2-treatment led to S and G2/M phase arrest in both cells, which could be elucidated by the change of mRNA levels of p21, p27 and Cyclin E and the increased protein level of p21. G2 also induced dramatically ROS accumulated and MMP decreased, which contributed to the apoptosis through activation of both the extrinsic and intrinsic pathways via changing the genes and proteins expression involved in apoptosis pathway in both of HepG2 and HCT116 cells.

CONCLUSION

These findings suggested that the apoptosis in both cell lines induced by G2 was related to the extrinsic and intrinsic pathways.

Salinomycin exerts anti-colorectal cancer activity by targeting the β-catenin/T-cell factor complex

Background and Purpose

Salinomycin is a well‐known inhibitor of human cancer stem cells (CSCs). However, the molecular mechanism(s) by which salinomycin targets colorectal CSCs is poorly understood. Here, we have investigated underlying antitumour mechanisms of salinomycin in colorectal cancer cells and three tumour models.

Experimental Approach

The inhibitory effect of salinomycin on the Wnt/β‐catenin pathway was analysed with the SuperTopFlash reporter system. The mRNA expression of Wnt target genes was evaluated with real‐time PCR. Effects of salinomycin on β‐catenin/TCF4E interaction were examined using co‐immunoprecipitation and an in vitro GST pull‐down assay. Cell proliferation was determined by BrdU incorporation and soft agar colony formation assay. The stemness of the cells was assessed by sphere formation assay. Antitumour effects of salinomycin on colorectal cancers was evaluated with colorectal CSC xenografts, APC^min/+ transgenic mice, and patient‐derived colorectal tumour xenografts.

Key Results

Salinomycin blocked β‐catenin/TCF4E complex formation in colorectal cancer cells and in an in vitro GST pull‐down assay, thus decreasing expression of Wnt target genes. Salinomycin also suppressed the transcriptional activity mediated by β‐catenin/LEF1 or β‐catenin/TCF4E complex and exhibited an inhibitory effect on the sphere formation, proliferation, and anchorage‐independent growth of colorectal cancer cells. In colorectal tumour xenografts and APC^min/+ transgenic mice, administration of salinomycin significantly reduced tumour growth and the expression of CSC‐related Wnt target genes including LGR5.

Conclusions and Implications

Our study suggested that salinomycin could suppress the growth of colorectal cancer by disrupting the β‐catenin/TCF complex and thus may be a promising agent for colorectal cancer treatment.

Salinomycin and its derivatives - A new class of multiple-targeted "magic bullets"

The history of drug development clearly shows the scale of painstaking effort leading to a finished product - a highly biologically active agent that would be at the same time no or little toxic to human organism. Moreover, the aim of modern drug discovery can move from "one-molecule one-target" concept to more promising "one-molecule multiple-targets" one, particularly in the context of effective fight against cancer and other complex diseases. Gratifyingly, natural compounds are excellent source of potential drug leads. One of such promising naturally-occurring drug candidates is a polyether ionophore - salinomycin (SAL). This compound should be identified as multi-target agent for two reasons. Firstly, SAL combines a broad spectrum of bioactivity, including antibacterial, antifungal, antiviral, antiparasitic and anticancer activity, with high selectivity of action, proving its significant therapeutic potential. Secondly, the multimodal mechanism of action of SAL has been shown to be related to its interactions with multiple molecular targets and signalling pathways that are synergistic for achieving a therapeutic anticancer effect. On the other hand, according to the Paul Ehrlich's "magic bullet" concept, invariably inspiring the scientists working on design of novel target-selective molecules, a very interesting direction of research is rational chemical modification of SAL. Importantly, many of SAL derivatives have been found to be more promising as chemotherapeutics than the native structure. This concise review article is focused both on the possible role of SAL and its selected analogues in future antimicrobial and/or cancer therapy, and on the potential use of SAL as a new class of multiple-targeted "magic bullet" because of its multimodal mechanism of action.

Salinomycin: Anti-tumor activity in a pre-clinical colorectal cancer model

Objectives

Salinomycin is a polyether antibiotic with selective activity against human cancer stem cells. The impact of salinomycin on patient-derived primary human colorectal cancer cells has not been investigated so far. Thus, here we aimed to investigate the activity of salinomycin against tumor initiating cells isolated from patients with colorectal cancer.

Methods

Primary tumor-initiating cells (TIC) isolated from human patients with colorectal liver metastases or from human primary colon carcinoma were exposed to salinomycin and compared to treatment with 5-FU and oxaliplatin. TICs were injected subcutaneously into NOD/SCID mice to induce a patient-derived mouse xenograft model of colorectal cancer. Animals were treated either with salinomycin, FOLFOX regimen, or salinomycin and FOLFOX. Human colorectal cancer cells were used to delineate an underlying molecular mechanism of salinomycin in this tumor entity.

Results

Applying TICs isolated from human patients with colorectal liver metastases or from human primary colon carcinoma, we demonstrated that salinomycin exerts increased antiproliferative activity compared to 5-fluorouracil and oxaliplatin treatment. Consistently, salinomycin alone or in combination with FOLFOX exerts superior antitumor activity compared to FOLFOX therapy in a patient-derived mouse xenograft model of colorectal cancer. Salinomycin induces apoptosis of human colorectal cancer cells, accompanied by accumulation of dysfunctional mitochondria and reactive oxygen species. These effects are associated with expressional down-regulation of superoxide dismutase-1 (SOD1) in response to salinomycin treatment.

Conclusion

Collectively, the results of this pre-clinical study indicate that salinomycin alone or in combination with 5-fluorouracil and oxaliplatin exerts increased antitumoral activity compared to common chemotherapy.

Targeting Mitochondria for Treatment of Chemoresistant Ovarian Cancer

Ovarian cancer is the leading cause of death from gynecologic malignancy in the Western world. This is due, in part, to the fact that despite standard treatment of surgery and platinum/paclitaxel most patients recur with ultimately chemoresistant disease. Ovarian cancer is a unique form of solid tumor that develops, metastasizes and recurs in the same space, the abdominal cavity, which becomes a unique microenvironment characterized by ascites, hypoxia and low glucose levels. It is under these conditions that cancer cells adapt and switch to mitochondrial respiration, which becomes crucial to their survival, and therefore an ideal metabolic target for chemoresistant ovarian cancer. Importantly, independent of microenvironmental factors, mitochondria spatial redistribution has been associated to both tumor metastasis and chemoresistance in ovarian cancer while specific sets of genetic mutations have been shown to cause aberrant dependence on mitochondrial pathways in the most aggressive ovarian cancer subtypes. In this review we summarize on targeting mitochondria for treatment of chemoresistant ovarian cancer and current state of understanding of the role of mitochondria respiration in ovarian cancer. We feel this is an important and timely topic given that ovarian cancer remains the deadliest of the gynecological diseases, and that the mitochondrial pathway has recently emerged as critical in sustaining solid tumor progression.

Ionophores: Potential Use as Anticancer Drugs and Chemosensitizers

Ion homeostasis is extremely important for the survival of both normal as well as neoplastic cells. The altered ion homeostasis found in cancer cells prompted the investigation of several ionophores as potential anticancer agents. Few ionophores, such as Salinomycin, Nigericin and Obatoclax, have demonstrated potent anticancer activities against cancer stem-like cells that are considered highly resistant to chemotherapy and responsible for tumor relapse. The preclinical success of these compounds in in vitro and in vivo models have not been translated into clinical trials. At present, phase I/II clinical trials demonstrated limited benefit of Obatoclax alone or in combination with other anticancer drugs. However, future development in targeted drug delivery may be useful to improve the efficacy of these compounds. Alternatively, these compounds may be used as leading molecules for the development of less toxic derivatives.

Intestinal microbiota: a novel perspective in colorectal cancer biotherapeutics

It is believed that genetic factors, immune system dysfunction, chronic inflammation, and intestinal microbiota (IM) dysbiosis contribute to the pathogenesis of colorectal cancer (CRC). The beneficial role played by the direct regulation of IM in inflammatory bowel disease treatment is identified by the decreased growth of harmful bacteria and the increased production of anti-inflammatory factors. Interestingly, gut microbiota has been proven to inhibit tumor formation and progression in inflammation/carcinogen-induced CRC mouse models. Recently, evidence has indicated that IM is involved in the negative regulation of tumor immune response in tumor microenvironment, which then abolishes or accelerates anticancer immunotherapy in several tumor animals. In clinical trials, a benefit of IM-based CRC therapies in improving the intestinal immunity balance, epithelial barrier function, and quality of life has been reported. Meanwhile, specific microbiota signature can modulate host's sensitivity to chemo-/radiotherapy and the prognosis of CRC patients. In this review, we aim to 1) summarize the potential methods of IM-based therapeutics according to the recent results; 2) explore its roles and underlying mechanisms in combination with other therapies, especially in biotherapeutics; 3) discuss its safety, deficiency, and future perspectives.

JIB-04, A Small Molecule Histone Demethylase Inhibitor, Selectively Targets Colorectal Cancer Stem Cells by Inhibiting the Wnt/β-Catenin Signaling Pathway

Although several epigenetic modulating drugs are suggested to target cancer stem cells (CSCs), additional identification of anti-CSC drugs is still necessary. Here we showed that JIB-04, a pan-selective inhibitor of histone demethylase(s), was identified as a small molecule that selectively target colorectal CSCs. Our data showed that JIB-04 is capable of reducing self-renewal and stemness of colorectal CSCs in three different colorectal cancer cell lines. JIB-04 significantly attenuated CSC tumorsphere formation, growth/relapse, invasion, and migration in vitro. Furthermore, JIB-04-treated colorectal cancer cells showed reduced tumorigenic activity in vivo. RNA sequencing analysis revealed that JIB-04 affected various cancer-related signaling pathways, especially Wnt/β-catenin signaling, which is crucial for the proliferation and maintenance of colorectal cancer cells. qRT-PCR and TOP/FOP flash luciferase assays showed that JIB-04 down-regulated the expression of Wnt/β-catenin-regulated target genes associated with colorectal CSC function. Overall, the effects of JIB-04 were equal to or greater than those of salinomycin, a known anti-colorectal CSC drug, despite the lower concentration of JIB-04 compared with that of salinomycin. Our results strongly suggest that JIB-04 is a promising drug candidate for colorectal cancer therapy.

BCN057 induces intestinal stem cell repair and mitigates radiation-induced intestinal injury

BACKGROUND

Radiation-induced gastrointestinal syndrome (RIGS) results from the acute loss of intestinal stem cells (ISC), impaired epithelial regeneration, and subsequent loss of the mucosal barrier, resulting in electrolyte imbalance, diarrhea, weight loss, sepsis, and mortality. The high radiosensitivity of the intestinal epithelium limits effective radiotherapy against abdominal malignancies and limits the survival of victims of nuclear accidents or terrorism. Currently, there is no approved therapy to mitigate radiation toxicity in the intestine. Here we demonstrate that BCN057, an anti-neoplastic small molecular agent, induces ISC proliferation and promotes intestinal epithelial repair against radiation injury.

METHODS

BCN057 (90 mg/kg body weight, subcutaneously) was injected into C57Bl6 male mice (JAX) at 24 h following abdominal irradiation (AIR) and was continued for 8 days post-irradiation. BCN057-mediated rescue of Lgr5-positive ISC was validated in Lgr5-EGFP-Cre-ERT2 mice exposed to AIR. The regenerative response of Lgr5-positive ISC was examined by lineage tracing assay using Lgr5-EGFP-ires-CreERT2-TdT mice with tamoxifen administration to activate Cre recombinase and thereby marking the ISC and their respective progeny. Ex vivo three-dimensional organoid cultures were developed from surgical specimens of human colon or from mice jejunum and were used to examine the radio-mitigating role of BCN057 on ISC ex vivo. Organoid growth was determined by quantifying the budding crypt/total crypt ratio. Statistical analysis was performed using Log-rank (Mantel-Cox) test and paired two-tail t test.

RESULTS

Treatment with BCN057 24 h after a lethal dose of AIR rescues ISC, promotes regeneration of the intestinal epithelium, and thereby mitigates RIGS. Irradiated mice without BCN057 treatment suffered from RIGS, resulting in 100% mortality within 15 days post-radiation. Intestinal organoids developed from mice jejunum or human colon demonstrated a regenerative response with BCN057 treatment and mitigated radiation toxicity. However, BCN057 did not deliver radio-protection to mouse or human colon tumor tissue.

CONCLUSION

BCN057 is a potential mitigator against RIGS and may be useful for improving the therapeutic ratio of abdominal radiotherapy. This is the first report demonstrating that a small molecular agent mitigates radiation-induced intestinal injury by inducing ISC self-renewal and proliferation.

Salinomycin inhibits cholangiocarcinoma growth by inhibition of autophagic flux

Introduction

Cholangiocarcinoma is characterized by aggressive tumor growth, high recurrence rates, and resistance against common chemotherapeutical regimes. The polyether-antibiotic Salinomycin is a promising drug in cancer therapy because of its ability to overcome apoptosis resistance of cancer cells and its selectivity against cancer stem cells. Here, we investigated the effectiveness of Salinomycin against cholangiocarcinoma in vivo, and analyzed interference of Salinomycin with autophagic flux in human cholangiocarcinoma cells.

Results

Salinomycin reduces tumor cell viability, proliferation, migration, invasion, and induced apoptosis in vitro. Subcutaneous and intrahepatic cholangiocarcinoma growth in vivo was inhibited upon Salinomycin treatment. Analysis of autophagy reveals inhibition of autophagic activity. This was accompanied by accumulation of mitochondrial mass and increased generation of reactive oxygen species.

Conclusions

This study demonstrates the effectiveness of Salinomycin against cholangiocarcinoma in vivo. Inhibition of autophagic flux represents an underlying molecular mechanism of Salinomycin against cholangiocarcinoma.

Methods

The two murine cholangiocarcinoma cell lines p246 and p254 were used to analyze tumor cell proliferation, viability, migration, invasion, and apoptosis in vitro. For in vivo studies, murine cholangiocarcinoma cells were injected into syngeneic C57-BL/6-mice to initiate subcutaneous cholangiocarcinoma growth. Intrahepatic tumor growth was induced by electroporation of oncogenic transposon-plasmids into the left liver lobe. For mechanistic studies in human cells, TFK-1 and EGI-1 were used, and activation of autophagy was analyzed after exposure to Salinomycin.

Salinomycin's potential to eliminate glioblastoma stem cells and treat glioblastoma multiforme (Review)

Glioblastoma multiforme (GBM) is the most common and deadliest form of primary brain tumor. Despite treatment with surgery, radiotherapy, and chemotherapy with the drug temozolomide, the expected survival after diagnosis remains low. The median survival is only 14.6 months and the two-year survival is a mere 30%. One reason for this is the heterogeneity of GBM including the presence of glioblastoma cancer stem cells (GSCs). GSCs are a subset of cells with the unique ability to proliferate, differentiate, and create tumors. GSCs are resistant to chemotherapy and radiation and thought to play an important role in recurrence. In order to effectively treat GBM, a drug must be identified that can kill GSCs. The ionophore salinomycin has been shown to kill cancer stem cells and is therefore a promising future treatment for GBM. This study focuses on salinomycin's potential to treat GBM including its ability to reduce the CSC population, its toxicity to normal brain cells, its mechanism of action, and its potential for combination treatment.