Cancer Stem Cell-like Characteristics Research Articles

Trapped in Cells: A Selective Accumulation Approach for Type-I Photodynamic Ablation of Cancer Stem-like Cells.

Aldehyde dehydrogenase (ALDH) is an enzyme responsible for converting aldehyde functional groups into carboxylate metabolites. Elevated ALDH activity is a characteristic feature of cancer stem-like cells (CSCs). As a novel approach to target the CSC trait of overexpressing ALDH, we aimed to utilize ALDH activity for the selective accumulation of a photosensitizer in ALDHHigh CSCs. A novel ALDH substrate photosensitizer, SCHO, with thionylated coumarin and N-ethyl-4-(aminomethyl)benzaldehyde was developed to achieve this goal. Our study demonstrated the efficient metabolism of the aldehyde unit of SCHO into carboxylate, leading to its accumulation in ALDHHigh MDA-MB-231 cells. Importantly, we established the selectivity of SCHO as an ALDHHigh cell photosensitizer as it is not a substrate for ABC transporters. SCHO-based photodynamic therapy triggers apoptosis and pyroptosis in MDA-MB-231 cells and further reduces the characteristics of CSCs. Our study presents a novel strategy to target CSCs by exploiting their cellular metabolism to enhance photosensitizer accumulation, highlighting the potential of photodynamic therapy as a powerful tool for eliminating ALDHHigh CSCs.

Abstract 5436: A therapeutically targetable dysadherin/YAP axis promotes cancer stem features and tumor aggressiveness in hepatocellular carcinoma

Abstract Hepatocellular carcinoma (HCC) remains one of the most challenging tumors to treat. Cancer stem-like cells (CSCs) are believed to be important in HCC development, immune evasion, and treatment resistance. Dysadherin is a cell membrane glycoprotein linked to cancer progression by endowing HCC with CSC features. However, the underlying mechanism of increasing CSC characteristics in refractory advanced HCC is not entirely understood. A comprehensive bioinformatics study revealed that dysadherin-expressing HCC cells were associated with cancer stemness and the YAP signaling activation. Dysadherin knockdown or overexpression in liver cancer cell lines attenuated or increased cancer stemness and aggressiveness via YAP signaling, respectively. Correspondingly, dysadherin deficiency lowered cancer stemness and aggressiveness in the HCC mouse model by blocking the YAP pathway. Mechanistically, dysadherin promoted YAP nuclear localization, which activated stem cell transcription factors such as OCT4, KLF4, and MYC. Of note, our comprehensive gain and loss of function studies in CSCs demonstrated that targeting the dysadherin/YAP axis could boost sorafenib’s therapeutic effect and suppress PD-L1 expression, which helps tumor cells escape from immune surveillance. Thus, our results highlight that the dysadherin/YAP axis drives the aggressive phenotype of HCC, providing a potential therapeutic strategy for HCC. Citation Format: So-El Jeon, Tae-Young Jang, Choong-Jae Lee, Hyeon-Ji Yun, Yeong-Hoon Cho, Da-Ye Lim, Jeong-Seok Nam. A therapeutically targetable dysadherin/YAP axis promotes cancer stem features and tumor aggressiveness in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5436.

The TGFβ2-Snail1-miRNATGFβ2 Circuitry is Critical for the Development of Aggressive Functions in Breast Cancer.

There have been contradictory reports on the biological role of transforming growth factor-βs (TGFβs) in breast cancer (BC), especially with regard to their ability to promote epithelial-mesenchymal transition (EMT). Here, we show that TGFβ2 is preferentially expressed in mesenchymal-like BCs and maintains the EMT phenotype, correlating with cancer stem cell-like characteristics, growth, metastasis and chemo-resistance and predicting worse clinical outcomes. However, this is only true in ERα- BC. In ERα+ luminal-type BC, estrogen receptor interacts with p-Smads to block TGFβ signalling. Furthermore, we also identify a microRNAs (miRNAs) signature (miRNAsTGFβ2 ) that is weakened in TGFβ2-overexpressing BC cells. We discover that TGFβ2-Snail1 recruits enhancer of zeste homolog-2 to convert miRNAsTGFβ2 promoters from an active to repressive chromatin configuration and then repress miRNAsTGFβ2 transcription, forming a negative feedback loop. On the other hand, miRNAsTGFβ2 overexpression reverses the mesenchymal-like traits in agreement with the inhibition of TGFβ2-Snail1 signalling in BC cells. These findings clarify the roles of TGFβ2 in BC and suggest novel therapeutic strategies based on the TGFβ2-Snail1-miRNAsTGFβ2 loop for a subset type of human BCs.

Clonorchis sinensis infection amplifies hepatocellular carcinoma stemness, predicting unfavorable prognosis.

Extensive evidence links Clonorchis sinensis (C. sinensis) to cholangiocarcinoma; however, its association with hepatocellular carcinoma (HCC) is less acknowledged, and the underlying mechanism remains unclear. This study was designed to investigate the association between C. sinensis infection and HCC and reveal the relationship between C. sinensis infection and cancer stemness. A comprehensive analysis of 839 HCC patients categorized into C. sinensis (-) HCC and C. sinensis (+) HCC groups was conducted. Chi-square and Mann-Whitney U tests were used to assess the association between C. sinensis infection and clinical factors. Kaplan-Meier and Cox regression analyses were used to evaluate survival outcomes. Immunohistochemistry was used to determine CK19 and EpCAM expression in HCC specimens. Compared to C. sinensis (-) HCC patients, C. sinensis (+) HCC patients exhibited advanced Barcelona Clinic Liver Cancer (BCLC) stage, higher male prevalence and more liver cirrhosis as well as elevated alpha-fetoprotein (AFP), carbohydrate antigen 19-9 (CA19-9), eosinophil, complement 3 (C3), and complement 4 (C4) values. C. sinensis infection correlated with shorter overall survival (OS) (p < 0.05) and recurrence-free survival (RFS) (p < 0.05). Furthermore, Cox multivariate analysis revealed that C. sinensis infection was an independent prognostic factor for OS in HCC patients. Importantly, C. sinensis infection upregulated the expression of HCC cancer stem cell markers CK19 and EpCAM. HCC patients with C. sinensis infection exhibit a poor prognosis following hepatectomy. Moreover, C. sinensis infection promotes the acquisition of cancer stem cell-like characteristics, consequently accelerating the malignant progression of HCC. Clonorchis sinensis (C. sinensis) is a prominent food-borne parasite prevalent in regions such as China, particularly in Guangxi. C. sinensis has been associated with various hepatobiliary system injuries, encompassing inflammation, periductal fibrosis, cholangiocarcinoma and even hepatocellular carcinoma (HCC). A substantial body of evidence links C. sinensis to cholangiocarcinoma, However, the connection between C. sinensis and HCC and the intricate mechanisms underlying its contribution to HCC development remain incompletely elucidated. Our study demonstrates clear clinicopathological associations between C. sinensis and HCC, such as gender, BCLC stage, liver cirrhosis, MVI, AFP, CA19-9, circulating eosinophils and complements. Furthermore, we found that the co-occurrence of C. sinensis exhibited a significant association with shorter OS and RFS in patients diagnosed with HCC. A major finding was that C. sinensis infection promotes the acquisition of cancer stem cell-like characteristics, consequently accelerating the malignant progression of HCC. Our results provide a more comprehensive comprehension of the interplay between C. sinensis and HCC, shedding fresh light on the carcinogenic potential of C. sinensis.

SOX2 Expression Does Not Guarantee Cancer Stem Cell-like Characteristics in Lung Adenocarcinoma.

Effectively targeting cancer stemness is essential for successful cancer therapy. Recent studies have revealed that SOX2, a pluripotent stem cell factor, significantly contributes to cancer stem cell (CSC)-like characteristics closely associated with cancer malignancy. However, its contradictory impact on patient survival in specific cancer types, including lung adenocarcinoma (LUAD), underscores the need for more comprehensive research to clarify its functional effect on cancer stemness. In this study, we demonstrate that SOX2 is not universally required for the regulation of CSC-like properties in LUAD. We generated SOX2 knockouts in A549, H358, and HCC827 LUAD cells using the CRISPR/Cas9 system. Our results reveal unchanged CSC characteristics, including sustained proliferation, tumor sphere formation, invasion, migration, and therapy resistance, compared to normal cells. Conversely, SOX2 knockdown using conditional shRNA targeting SOX2, significantly reduced CSC traits. However, these loss-of-function effects were not rescued by SOX2 resistant to shRNA, underscoring the potential for SOX2 protein level-independent results in prior siRNA- or shRNA-based research. Ultimately, our findings demonstrate that SOX2 is not absolutely essential in LUAD cancer cells. This emphasizes the necessity of considering cancer subtype-dependent and context-dependent factors when targeting SOX2 overexpression as a potential therapeutic vulnerability in diverse cancers.

THBS2 promotes gastric cancer progression and stemness via the Notch signaling pathway.

Thrombospondin-2 (THBS2), a secreted extracellular matrix protein, plays a crucial role in various biological processes including angiogenesis, tissue remodeling, and inflammation. Our study focuses on its function in human gastric cancer (GC). Through bioinformatics and tumor tissue analysis, we compared THBS2 expression in GC tissues and adjacent tissues, and predicted regulatory upstream and downstream molecules. The direct regulatory effect of miR-29b-3p on THBS2 was evaluated through dual-luciferase reporter assays, showing that miR-29b-3p targets the 3'-UTR of THBS2 mRNA, reducing its expression in GC cells. The influence of THBS2 on tumorigenesis and stemness was examined on protein expression levels via Western blot. In vivo, THBS2's role was investigated through xenograft and metastasis assays in nude mice, demonstrating that downregulation of THBS2 impairs GC tumorigenesis and liver metastasis. Our study identified THBS2 as a highly expressed prognostic factor in GC patients. Functionally, THBS2 promotes GC progression through the Notch signaling pathway by regulating Notch3, NEY1, and HES1 proteins, and sustains cancer stem cell-like characteristics by Notch3, including the expression of CD44, Nanog, OCT4, and SOX2. In sum, our study reveals that THBS2 promotes GC progression and stemness, modulated negatively by miR-29b-3p. This suggests potential therapeutic targets within the THBS2/Notch signaling axis for combating gastric cancer.

An In Vitro Model for Acute Myeloid Leukemia Relapse Using the SORE6 Reporter.

Many patients diagnosed with acute myeloid leukemia (AML) relapse within two years of the initial remission. The biology of AML relapse is incompletely understood, although cancer stem-like (CSL) cells have been hypothesized to be important. To test this hypothesis, we employed SORE6, a reporter designed to detect the transcriptional activity of the embryonic stem cell proteins Oct4 and Sox2, to identify/purify CSL cells in two FLT3-mutated AML cell lines. Both cell lines contained ~10% of SORE6+ cells in the steady state. Compared to SORE6- cells, SORE6+ cells exhibited more characteristics of CSL cells, with significantly higher chemoresistance and rates of spheroid formation. SORE6+ cells had substantially higher expression of Myc and FLT3 proteins, which are drivers of SORE6 activity. Using a mixture of SORE6-/SORE6+ cells that were molecularly barcoded, we generated an in vitro study model for AML relapse. Specifically, after 'in vitro remission' induced by Ara-C, both cell lines regenerated after 13 ± 3 days. Barcode analysis revealed that most of the regenerated cells were derived from the original SORE6+ cells. Regenerated cells exhibited more CSL features than did the original SORE6+ cells, even though a proportion of them lost SORE6 activity. In bone marrow samples from a patient cohort, we found that relapsed blasts expressed significantly higher levels of Myc, a surrogate marker of SORE6 activity, compared to pre-treatment blasts. To conclude, using our in vitro model, we have provided evidence that CSL cells contribute to AML relapse.

Two new adenopeptins B and C inhibit sphere formation of pancreatic cancer cells.

Cancer remains one of the leading causes of death worldwide, particularly pancreatic cancer being lethal because of its aggressiveness and lack of early detection methods. A factor that contributes to malignancy are cancer stem cell-like characteristics promoted by the tumor-stromal interaction. Given that fibroblast conditioned medium (CM) promotes sphere formation of cancer cells, a cancer stem cell-like characteristic, its inhibitor could be a new anticancer agent. By exploring microbial cultures as a source, we found new compounds, namely, adenopeptins B (1) and C (2), from Acremonium sp. ESF00140. 1 and 2 selectively and potently inhibited the sphere formation of pancreatic cancer cells cultured in the fibroblast CM compared with the control medium. Oxygen consumption rate (OCR) assays showed that 1 and 2 inhibit OCR in pancreatic cancer cells. Studies of similar compounds suggested mitochondrial complex V inhibition. Therefore, results of measuring the activity of human mitochondrial complex V revealed that 1 and 2 inhibited its activity. Oligomycin A, an inhibitor of mitochondrial complex V, as well as 1 and 2, strongly inhibited the sphere formation of pancreatic cancer cells cultured in fibroblast CM. The addition of 1 and 2 to pancreatic cancer cells cultured in fibroblast CM increased reactive oxygen species (ROS) production compared with that in the control medium. In pancreatic cancer cells cultured in fibroblast CM, mitochondria significantly influence sphere formation, and targeting their function with 1 and 2 might provide a new therapeutic approach for pancreatic cancer.

BCL7B, a SWI/SNF complex subunit, orchestrates cancer immunity and stemness

Cancer is one of the main causes of human death. Here, we focus on the B-cell lymphoma 7 protein family member B (BCL7B) gene, an accessory subunit of the SWI/SNF chromatin-remodelling complex. To characterize the function of BCL7B, heterozygous BCL7B-deficient stomach cancer cell lines were generated with the CRISPR/Cas9 genome editing system. The comprehensive gene expression patterns were compared between parental cells and each ΔBCL7B cell line by RNA-seq. The results showed marked downregulation of immune-related genes and upregulation of stemness-related genes in the ΔBCL7B cell lines. Moreover, by ChIP-seq analysis with H3K27me3 antibody, the changes of epigenetic modification sequences were compared between parental cells and each ΔBCL7B cell line. After machine learning, we detected the centroid sequence changes, which exerted an impact on antigen presentation. The regulation of BCL7B expression in cancer cells gives rise to cancer stem cell-like characteristics and the acquisition of an immune evasion phenotype.

Polyploidy, EZH2 upregulation, and transformation in cytomegalovirus-infected human ovarian epithelial cells

Human cytomegalovirus (HCMV) infection has been implicated in epithelial ovarian cancer (OC). Polyploidy giant cancer cells (PGCCs) have been observed in high-grade serous ovarian carcinoma (HGSOC); they possess cancer stem cell-like characteristics and give rise to progeny cells expressing epithelial-mesenchymal transition (EMT) markers. EZH2 plays a potential oncogenic role, correlating with high proliferative index and tumor grade in OC. Herein, we present the experimental evidence for HCMV as a reprogramming vector that elicited human ovarian epithelial cells (OECs) transformation leading to the generation of “CMV-transformed Ovarian cells” (CTO). The infection with the two high-risk clinical strains, namely HCMV-DB and BL provoked a distinct cellular and molecular mechanisms in infected OECs. EZH2 upregulation and cellular proliferation were curtailed by using EZH2 inhibitors. The HGSOC biopsies were characterized by an elevated EZH2 expression, possessing a strong positive correlation between the aforementioned marker and HCMV. From HGSOC biopsies, we isolated three HCMV clinical strains that transformed OECs generating CTO cells which displayed proliferative potentials in addition to EZH2 upregulation and PGCCs generation; these features were reduced upon EZH2 inhibition. High-risk HCMV strains transformed OECs confirming an HCMV-induced epithelial ovarian cancer model and highlighting EZH2 tumorigenic properties. Our findings might be highly relevant in the pathophysiology of ovarian tumors thereby nominating new targeted therapeutics.

Ascitic autotaxin as a potential prognostic, diagnostic, and therapeutic target for epithelial ovarian cancer

BackgroundMalignant ascites contributes to the metastatic process by facilitating the multifocal dissemination of ovarian tumour cells onto the peritoneal surface. However, the prognostic and diagnostic relevance of ascitic fluid remains largely unknown. Herein, we investigated the potential clinical value and therapeutic utility of ascitic autotaxin (ATX) in epithelial ovarian cancer (EOC).MethodsATX expression was assessed in clinical samples. Spheroid-forming assay, real-time PCR, western blot analysis, invadopodia assay, and adhesion assays were performed.ResultsAscitic ATX expression was highly elevated in patients with ovarian cancer compared to those with benign ascites and was associated with advanced stage, high grade, and a short disease-free period in patients with EOC. Combining the diagnostic ability of ascitic ATX and serum CA-125 levels significantly improved the area under the curve (AUC) value for EOC compared to serum CA125 level alone. This marker combination showed a large odds ratio for short disease-free period in high-risk EOC groups. Functional studies revealed that ascitic ATX was required for maintaining cancer stem cell-like characteristics and invadopodia formation.ConclusionAscitic ATX levels may serve as a useful prognostic indicator for predicting aggressive behaviour in EOC. ATX-linked invadopodia are a potential target to prevent peritoneal dissemination in ovarian cancer.

AR antagonists develop drug resistance through TOMM20 autophagic degradation-promoted transformation to neuroendocrine prostate cancer

BackgroundProstate cancer(PCa) is the most commonly occurring male cancer in the USA. Abiraterone or Enzalutamide have been approved for the treatment of metastatic castration-resistant prostate cancer (CRPC). However, the treatment-emergent neuroendocrine PCa (t-NEPC) may develop, resulting in drug resistance in about 10–17% CRPC patients. The detailed mechanisms remain unclear..MethodsThe expression correlation of TOMM20 and AR in PCa was determined by analyzing publicly available datasets, or by IHC staining in tumor specimens. The protein interaction of TOMM20 and AR was validated by co-immunoprecipitation or GST pull-down assay. The impact of TOMM20 depletion on drug sensitivity were elucidated by assays of cell proliferation, invasion, sphere formation, xenograft growth and intravenous metastasis. The intracellular ROS level was measured by flow cytometry, and the NEPC transdifferentiation and characteristics of cancer stem-like cells were validated by RNA-seq, RT-PCR and western blotting.ResultsThe protein level of TOMM20 is positively correlated with AR in PCa cells and specimens. TOMM20 protein physically interacts with AR. AR antagonists induced the protein degradation of TOMM20 through autophagy-lysosomal pathway, thereby elevating the intracellular ROS level and activating PI3K/AKT signaling pathway. When TOMM20 was depleted, PCa cells underwent EMT, acquired the characteristics of cancer stem-like cells, and developed resistance to AR antagonists. The stable depletion of TOMM20 promoted the transdifferentiation of PCa adenocarcinoma into NEPC and metastasis. Conversely, the rescue of TOMM20 re-sensitized the resistant PCa cells to AR antagonists.ConclusionsTOMM20 protein degradation induced by AR antagonists promoted the transdifferentiation of PCa to NEPC, thereby revealing a novel molecular mechanism by which AR antagonists develop drug resistance through mitochondrial outer membrane-mediated signaling pathway. These findings suggested that the decreasing or loss of TOMM20 expression in PCa tissues might become a useful predictor of PCa resistance to AR antagonists.

ISG15 and ISGylation modulates cancer stem cell-like characteristics in promoting tumor growth of anaplastic thyroid carcinoma

BackgroundAnaplastic thyroid carcinoma (ATC) was a rare and extremely malignant endocrine cancer with the distinct hallmark of high proportion of cancer stem cell-like characteristics. Therapies aiming to cancer stem-like cells (CSCs) were emerging as a new direction in cancer treatment, but targeting ATC CSCs remained challenging, mainly due to incomplete insights of the regulatory mechanism of CSCs. Here, we unveiled a novel role of ISG15 in the modulation of ATC CSCs.MethodsThe expression of ubiquitin-like proteins were detected by bioinformatics and immunohistochemistry. The correlation between ISG15 expression and tumor stem cells and malignant progression of ATC was analyzed by single-cell RNA sequence from the Gene Expression Omnibus. Flow cytometry combined with immunofluorescence were used to verify the enrichment of ISG15 and ISGyaltion in cancer stem cells. The effect and mechanism of ISG15 and KPNA2 on cancer stem cell-like characteristics of ATC cells were determined by molecular biology experiments. Mass spectrometry combined with immunoprecipitation to screen the substrates of ISG15 and validate its ISGylation modification. Nude mice and zebrafish xenograft models were utilized to demonstrate that ISG15 regulates stem cell characteristics and promotes malignant progression of ATC.ResultsWe found that among several ubiquitin proteins, only ISG15 was aberrantly expressed in ATC and enriched in CSCs. Single-cell sequencing analysis revealed that abnormal expression of ISG15 were intensely associated with stemness and malignant cells in ATC. Inhibition of ISG15 expression dramatically attenuated clone and sphere formation of ATC cells, and facilitated its sensitivity to doxorubicin. Notably, overexpression of ISGylation, but not the non-ISGylation mutant, effectively reinforced cancer stem cell-like characteristics. Mechanistically, ISG15 mediated the ISGylation of KPNA2 and impeded its ubiquitination to promote stability, further maintaining cancer stem cell-like characteristics. Finally, depletion of ISG15 inhibited ATC growth and metastasis in xenografted mouse and zebrafish models.ConclusionOur studies not only provided new insights into potential intervention strategies targeting ATC CSCs, but also uncovered the novel biological functions and mechanisms of ISG15 and ISGylation for maintaining ATC cancer stem cell-like characteristics.Graphical

Retraction.

Retraction: Le Kang, Jun Mao, Yajun Tao, Bo Song, Wei Ma, Ying Lu, Lijing Zhao, Jiazhi Li, Baoxue Yang, Lianhong Li, MicroRNA-34a suppresses the breast cancer stem cell-like characteristics by downregulating Notch1 pathway, Cancer Science 2015, 106 (6), pp. 700-708 (https://onlinelibrary.wiley.com/doi/10.1111/cas.12656). The above article, published online on 17 March 2015 in Wiley Online Library (wileyonlinelibrary.com) has been retracted by agreement between the authors, the journal Editor in Chief Masanori Hatakeyama, Japanese Cancer Association and John Wiley and Sons Australia, Ltd. following an investigation on overlapping images in Figure 3B. The authors asked to retract this manuscript as the experimental data in the article could not be reproduced as the original data are no longer available. Therefore, the article's conclusions cannot be verified and must be considered unreliable.

Effect of LGR4/EGFR signaling on cell growth and cancer stem cell-like characteristics in liver cancer

PurposeHepatocellular carcinoma (HCC) is the most common primary liver cancer. Leucine-rich repeat containing G-protein-coupled receptors 4 (LGR4) participates in tumor progression, invasion, and metastasis. Our study aimed to investigate the effect of LGR4 with epidermal growth factor receptor (EGFR) in HCC cells. MethodsWe employed Hep3B and Huh7 cells to conduct our research. Comprehensive biological activities were characterized by CCK8 and transwell assay. Molecular biology techniques were used to determine the expression of proteins. Hep3B was employed to conduct subcutaneous tumor in mice. The tumor growth and the expression levels of proteins were assessed. ResultsLGR4 overexpression could promote the cells proliferation, migration, and invasion ability, while siLGR4 and siEGFR could inhibit cells biological activities. In addition, LGR4 overexpression promoted the expression levels of RSPO2, β-catenin, EGFR and cancer stem cells (CSCs) markers, whereas silence of LGR4 or EGFR could diminish the expression levels of β-catenin and CSCs markers. Furthermore, knockdown of LGR4 or EGFR also inhibited tumor growth and reduced the expression levels of RSPO2, CD133, CD44, Nanog, β-catenin in vivo. ConclusionOur data suggest that LGR4 /EGFR signaling in HCC leads to induce tumor growth, which then contributes to stem cell characteristics. It maybe a new perspective for the targeted therapy of HCC treatment.

Preclinical and Clinical Trials of New Treatment Strategies Targeting Cancer Stem Cells in Subtypes of Breast Cancer.

Breast cancer (BC) can be classified into various histological subtypes, each associated with different prognoses and treatment options, including surgery, radiation, chemotherapy, and endocrine therapy. Despite advances in this area, many patients still face treatment failure, the risk of metastasis, and disease recurrence, which can ultimately lead to death. Mammary tumors, like other solid tumors, contain a population of small cells known as cancer stem-like cells (CSCs) that have high tumorigenic potential and are involved in cancer initiation, progression, metastasis, tumor recurrence, and resistance to therapy. Therefore, designing therapies specifically targeting at CSCs could help to control the growth of this cell population, leading to increased survival rates for BC patients. In this review, we discuss the characteristics of CSCs, their surface biomarkers, and the active signaling pathways associated with the acquisition of stemness in BC. We also cover preclinical and clinical studies that focus on evaluating new therapy systems targeted at CSCs in BC through various combinations of treatments, targeted delivery systems, and potential new drugs that inhibit the properties that allow these cells to survive and proliferate.

CTTN Overexpression Confers Cancer Stem Cell-like Properties and Trastuzumab Resistance via DKK-1/WNT Signaling in HER2 Positive Breast Cancer

Despite the therapeutic success of trastuzumab, HER2 positive (HER2+) breast cancer patients continue to face significant difficulties due to innate or acquired drug resistance. In this study we explored the potential role of CTTN in inducing trastuzumab resistance of HER2+ breast cancers. Genetic changes of CTTN and survival of HER2+ breast cancer patients were analyzed in multiple breast cancer patient cohorts (METABRIC, TCGA, Kaplan-Meier (KM) plotter, and Hanyang University cohort). The effect of CTTN on cancer stem cell activity was assessed using the tumorsphere formation, ALDEFLUOR assay, and by in vivo xenograft experiments. CTTN-induced trastuzumab resistance was assessed by the sulforhodamine B (SRB) assay, colony formation assays, and in vivo xenograft model. RNA-seq analysis was used to clarify the mechanism of trastuzumab resistance conferred by CTTN. Survival analysis indicated that CTTN overexpression is related to a poor prognosis in HER2+ breast cancers (OS, p = 0.05 in the Hanyang University cohort; OS, p = 0.0014 in KM plotter; OS, p = 0.008 and DFS, p = 0.010 in METABRIC). CTTN overexpression-induced cancer stem cell-like characteristics in experiments of tumorsphere formation, ALDEFLUOR assays, and in vivo limiting dilution assays. CTTN overexpression resulted in trastuzumab resistance in SRB, colony formation assays, and in vivo xenograft models. Mechanistically, the mRNA and protein levels of DKK-1, a Wnt antagonist, were downregulated by CTTN. Treatment of the β-catenin/TCF inhibitor reversed CTTN-induced cancer stem cell-like properties in vitro. Combination treatment with trastuzumab and β-catenin/TCF inhibitor overcame trastuzumab resistance conferred by CTTN overexpression in in vitro colony formation assays. CTTN activates DKK-1/Wnt/β-catenin signaling to induce trastuzumab resistance. We propose that CTTN is a novel biomarker indicating a poor prognosis and a possible therapeutic target for overcoming trastuzumab resistance.

Extracellular Vesicles in Cancer Drug Resistance: Implications on Melanoma Therapy.

Extracellular vesicles (EVs) are involved in the pathogenesis of neoplastic diseases. Their role in mediating drug resistance has been widely described in several types of cancers, including melanoma. EVs can mediate drug resistance through several different mechanisms, such as drug-sequestration, transfer of pro-survival proteins and RNA, induction of cancer stem cell-like features and interaction with cells of the tumor microenvironment and immune-system. Melanoma is a highly immunogenic tumor originating from the malignant transformation of melanocytes. Several therapeutic strategies currently used in the treatment of melanoma and the combination of BRAF and MEK-inhibitors, as well as immune check-point inhibitors (ICI), have consistently improved the overall survival time of melanoma patients. However, the development of resistance is one of the biggest problems leading to a poor clinical outcome, and EVs can contribute to this. EVs isolated from melanoma cells can contain "sequestered" chemotherapeutic drugs in order to eliminate them, or bioactive molecules (such as miRNA or proteins) that have been proven to play a crucial role in the transmission of resistance to sensitive neoplastic cells. This leads to the hypothesis that EVs could be considered as resistance-mediators in sensitive melanoma cells. These findings are a pivotal starting point for further investigations to better understand EVs' role in drug resistance mechanisms and how to target them. The purpose of this review is to summarize knowledge about EVs in order to develop a deeper understanding of their underlying mechanisms. This could lead to the development of new therapeutic strategies able to bypass EV-mediated drug-resistance in melanoma, such as by the use of combination therapy, including EV release inhibitors.

Anticancer Properties of a New Platinum (IV) Agent on HT1080 Cancer Stem-Like Cells: An in Vitro Study

According to the cancer stem cell (CSC) theory, a subpopulation of cells demonstrating stem-like cell properties is responsible for tumorigenicity, self-renewal capacity, therapeutic resistance, and recurrence. Due to the resistance of CSCs, it is necessary to develop drugs with appropriate efficacy. Although cisplatin is a potent antitumor agent widely used in the treatment of different cancers, its severe side effects and resistance remain a challenge in clinical practice. Research has shown that platinum (IV) has considerably fewer side effects and is associated with much less drug resistance. In this study, the toxicity and effectiveness of [Pt(dpyam)Cl4], where dpyam is 2,2'-dipyridylamine as a platinum (IV) agent, was investigated to find a reliable alternative to cisplatin. For this purpose, cancer stem-like cells (CS-LCs) with CD44+/CD133+ phenotype were isolated from HT1080 cells. EJ138, HT1080, and CS-LCs derived from HT1080 cells were selected to compare the effectiveness of Pt (IV) complex versus cisplatin. MTT, apoptosis, and cell cycle analysis were carried out to evaluate drug toxicity. Sphere and colony formation assays confirmed the potentiality of Pt (IV) complex and cisplatin to target stemness characteristics of CS-LCs. Although toxicity results were in favor of cisplatin, the anticancer activity of the synthesized Pt (IV) complex was also considerable. Regarding other studies that proposed high selective toxicity of Pt (IV), it could be a candidate for additional improvements.

Actin-like Protein 6A Expression Correlates with Cancer Stem Cell-like Features and Poor Prognosis in Ovarian Cancer.

Ovarian cancer has the highest mortality rate among gynecological cancers, often diagnosed at the late stage and lacking an effective targeted therapy. Although the study of malignant features of cancer, considered to be cancer stem cells (CSCs), is emerging, the aim of this study was to predict and explore the possible mechanism and clinical value of genetic markers in the development of ovarian cancer from a combined database with CSCs features. The common differentially expressed genes (DEGs) were selected in GSE185833 and GSE176246 datasets from the Gene Expression Omnibus (GEO). The GSE185833 dataset was created to reveal gene expression profiles of peritoneal metastasis tissues using single-cell sequencing, and the GSE176246 dataset was determined from gene expression profiles of chemotherapy-refractory ovarian cancer cell lines compared with ovarian cancer cell lines by RNA-seq analysis. By analyzing the correlation between common DEGs and prognosis of ovarian cancer and its possible pathways and functions were predicted by The Cancer Genome Atlas (TCGA) database. The expression levels of 11 genetic markers were significantly elevated in highly invasive and chemoresistant ovarian cancer. The expression of Actin-like protein 6A (ACTL6A) was found to be correlated with survival prognosis, and the total survival time of the patients with high expression of ACTL6A was shorter than those with low expression. Gene set enrichment analysis (GSEA) showed that ACTL6A positively enriched the gene set of 'Cell cycle' and ACTL6A negatively enriched the gene set of focal adhesion. CP724714, a human epidermal growth factor receptor 2 (HER2) inhibitor, could serve as a therapeutic option when ACTL6A levels are high in ovarian cancer cells. The high expression of ACTL6A is a poor prognostic factor in ovarian cancer and may serve as an effective biomarker for predicting treatment-refractory, metastasis, and prognosis of patients with ovarian cancer. The use of HER2 inhibitors is a promising therapeutic strategy against chemoresistant ovarian cancer.