E2A Modulates Stemness, Metastasis, and Therapeutic Resistance of Breast Cancer

Intersecting pathways: The role of hybrid E/M cells and circulating tumor cells in cancer metastasis and drug resistance

Cancer metastasis and therapy resistance are intricately linked with the dynamics of Epithelial-Mesenchymal Transition (EMT) and Circulating Tumor Cells (CTCs). EMT hybrid cells, characterized by a blend of epithelial and mesenchymal traits, have emerged as pivotal in metastasis and demonstrate remarkable plasticity, enabling transitions across cellular states crucial for intravasation, survival in circulation, and extravasation at distal sites. Concurrently, CTCs, which are detached from primary tumors and travel through the bloodstream, are crucial as potential biomarkers for cancer prognosis and therapeutic response. There is a significant interplay between EMT hybrid cells and CTCs, revealing a complex, bidirectional relationship that significantly influences metastatic progression and has a critical role in cancer drug resistance. This resistance is further influenced by the tumor microenvironment, with factors such as tumor-associated macrophages, cancer-associated fibroblasts, and hypoxic conditions driving EMT and contributing to therapeutic resistance. It is important to understand the molecular mechanisms of EMT, characteristics of EMT hybrid cells and CTCs, and their roles in both metastasis and drug resistance. This comprehensive understanding sheds light on the complexities of cancer metastasis and opens avenues for novel diagnostic approaches and targeted therapies and has significant advancements in combating cancer metastasis and overcoming drug resistance.

Senescence-related signatures predict prognosis and response to immunotherapy in colon cancer

Background

Colorectal cancer (CRC) is one of the most common cancers. Cellular senescence plays a vital role in carcinogenesis by activating many pathways. In this study, we aimed to identify biomarkers for predicting the survival and recurrence of CRC through cellular senescence-related genes.

Methods

Utilizing The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases, RNA-sequencing data and clinical information for CRC were collected. A risk model for predicting overall survival was established based on five differentially expressed genes using least absolute shrinkage and selection operator-Cox regression (LASSO-Cox regression), receiver operating characteristic (ROC), and Kaplan-Meier analyses. The study also delved into both the tumor microenvironment and the response to immunotherapy. Moreover, we gathered clinical sample data from our center in order to confirm the findings of public database analysis.

Results

Through ROC and Kaplan-Meier analyses, a risk model was developed using five cellular senescence-related genes [i.e., CDKN2A, SERPINE1, SNAI1, CXCL1, and ETS2] to categorize patients into high- and low-risk groups. In the TCGA-colon adenocarcinoma (COAD) and GEO-COAD cohorts, the high-risk group was associated with a bleaker forecast (P<0.05), immune cell inactivation, and insensitivity to immunotherapy in IMvigor210 database (http://research-pub.gene.com/IMvigor210CoreBiologies/). Clinical samples were then used to confirm that ETS2 and CDKN2A could serve as independent prognostic biomarkers in CRC.

Conclusions

Gene signatures related to cellular senescence, specifically involving CDKN2A and ETS2, are emerging as promising biomarkers for predicting CRC prognosis and guiding immunotherapy.

Identification of lineage-specific epigenetic regulators FOXA1 and GRHL2 through chromatin accessibility profiling in breast cancer cell lines

Breast cancer is a heterogeneous disease, and breast cancer cell lines are invaluable for studying this heterogeneity. However, the epigenetic diversity across these cell lines remains poorly understood. In this study, we performed genome-wide chromatin accessibility analysis on 23 breast cancer cell lines, including 2 estrogen receptor (ER)-positive/human epidermal growth factor receptor 2 (HER2)-negative (ER+/HER2-), 3 ER+/HER2+, 3 HER2+, and 15 triple-negative breast cancer (TNBC) lines. These cell lines were classified into three groups based on their chromatin accessibility: the receptor-positive group (Group-P), TNBC basal group (Group-B), and TNBC mesenchymal group (Group-M). Motif enrichment analysis revealed that only Group-P exhibited coenrichment of forkhead box A1 (FOXA1) and grainyhead-like 2 (GRHL2) motifs, whereas Group-B was characterized by the presence of the GRHL2 motif without FOXA1. Notably, Group-M did not show enrichment of either FOXA1 or GRHL2 motifs. Furthermore, gene ontology analysis suggested that group-specific accessible regions were associated with their unique lineage characteristics. To investigate the epigenetic landscape regulatory roles of FOXA1 and GRHL2, we performed knockdown experiments targeting FOXA1 and GRHL2, followed by assay for transposase-accessible chromatin sequencing analysis. The findings revealed that FOXA1 maintains Group-P-specific regions while suppressing Group-B-specific regions in Group-P cells. In contrast, GRHL2 preserves commonly accessible regions shared between Group-P and Group-B in Group-B cells, suggesting that FOXA1 and GRHL2 play a pivotal role in preserving distinct chromatin accessibility patterns for each group. Specifically, FOXA1 distinguishes between receptor-positive and TNBC cell lines, whereas GRHL2 distinguishes between basal-like and mesenchymal subtypes in TNBC lines.

DeepFGRN: inference of gene regulatory network with regulation type based on directed graph embedding

The inference of gene regulatory networks (GRNs) from gene expression profiles has been a key issue in systems biology, prompting many researchers to develop diverse computational methods. However, most of these methods do not reconstruct directed GRNs with regulatory types because of the lack of benchmark datasets or defects in the computational methods. Here, we collect benchmark datasets and propose a deep learning-based model, DeepFGRN, for reconstructing fine gene regulatory networks (FGRNs) with both regulation types and directions. In addition, the GRNs of real species are always large graphs with direction and high sparsity, which impede the advancement of GRN inference. Therefore, DeepFGRN builds a node bidirectional representation module to capture the directed graph embedding representation of the GRN. Specifically, the source and target generators are designed to learn the low-dimensional dense embedding of the source and target neighbors of a gene, respectively. An adversarial learning strategy is applied to iteratively learn the real neighbors of each gene. In addition, because the expression profiles of genes with regulatory associations are correlative, a correlation analysis module is designed. Specifically, this module not only fully extracts gene expression features, but also captures the correlation between regulators and target genes. Experimental results show that DeepFGRN has a competitive capability for both GRN and FGRN inference. Potential biomarkers and therapeutic drugs for breast cancer, liver cancer, lung cancer and coronavirus disease 2019 are identified based on the candidate FGRNs, providing a possible opportunity to advance our knowledge of disease treatments.

circPVT1 promotes silica-induced epithelial-mesenchymal transition by modulating the miR-497-5p/TCF3 axis

Epithelial-mesenchymal transition (EMT) is a vital pathological feature of silica-induced pulmonary fibrosis. However, whether circRNA is involved in the process remains unclear. The present study aimed to investigate the role of circPVT1 in the silica-induced EMT and the underlying mechanisms. We found that an elevated expression of circPVT1 promoted EMT and enhanced the migratory capacity of silica-treated epithelial cells. The isolation of cytoplasmic and nuclear separation assay showed that circPVT1 was predominantly expressed in the cytoplasm. RNA immunoprecipitation assay and RNA pull-down experiment indicated that cytoplasmic-localized circPVT1 was capable of binding to miR-497-5p. Furthermore, we found that miR-497-5p attenuated the silica-induced EMT process by targeting transcription factor 3 (TCF3), an E-cadherin transcriptional repressor, in the silica-treated epithelial cells. Collectively, these results reveal a novel role of the circPVT1/miR-497-5p/TCF3 axis in the silica-induced EMT process in lung epithelial cells. Once validated, this finding may provide a potential theoretical basis for the development of interventions and treatments for pulmonary fibrosis.

Transcription Factor TCF3 Promotes Macrophage-Mediated Inflammation and MMP Secretion in Abdominal Aortic Aneurysm by Regulating miR-143-5p /CCL20

ABSTRACT

Damage to the abdominal aortic wall and the local inflammatory response are key factors resulting in abdominal aortic aneurysm (AAA) formation. During this process, macrophage polarization plays a key role. However, in AAA, the regulatory mechanism of macrophages is still unclear, and further research is needed. In this study, we found that the transcription factor TCF3 was expressed at low levels in AAA. We overexpressed TCF3 and found that TCF3 could inhibit MMP and inflammatory factor expression and promote M2 macrophage polarization, thereby inhibiting the progression of AAA. Knocking down TCF3 could promote M1 polarization and MMP and inflammatory factor expression. In addition, we found that TCF3 increased miR-143-5p expression through transcriptional activation of miR-143-5p , which further inhibited expression of the downstream chemokine CCL20 and promoted M2 macrophage polarization. Our research indicates that TCF3-mediated macrophage polarization plays a key regulatory role in AAA, complementing the role and mechanism of macrophages in the occurrence and development of AAA and providing a scientific basis for AAA treatment.

Exportin XPO7 acts as an oncogenic factor in prostate cancer via upregulation of TCF3

PURPOSE

As a nuclear transport protein, XPO7 has been observed to show abnormal expression in various types of human cancers. However, the role of XPO7 in PCa remains elusive.

METHODS

Here, in this study, immunohistochemistry and bioinformatics were used to determine the expression pattern and prognostic significance of XPO7. To investigate the functions of XPO7 in vitro and in vivo, we knocked down XPO7 in PCa cell lines and established xenograft mice models. Then, we used multiple experiments to determine the cell proliferation, migration, invasion, cell cycle and EMT in PCa cells after XPO7 modulation. Mechanistically, we conducted RNA-seq and identified the regulating effect of XPO7 on cell cycle-related and PI3K-AKT pathways. Furthermore, we assessed the regulating correlation between XPO7 and TCF3 and verified by a series of rescue experiments.

RESULTS

We found a higher XPO7 expression in prostate cancer tissues and predicted a poorer prognosis of prostate cancer. Then, we further revealed that the ectopic expression of XPO7 in PCa cells facilitated cells proliferation, migration, cell cycle progression and EMT in vitro and promoted tumor growth in vivo. Mechanistically, we conducted RNA-seq and identified the regulating effect of XPO7 on cell cycle-related and PI3K-AKT pathways. Furthermore, a significantly positive correlation was discovered between the expression of XPO7 and TCF3. In addition, XPO7 may regulate PCa through mediating TCF3 expression. TCF3 depletion could alleviate the influence of XPO7 overexpression on malignant phenotypes of PCa cells.

CONCLUSIONS

These findings indicate that XPO7 promotes PCa initiation and progression and that targeting XPO7 might be therapeutically beneficial to patients with PCa.

Recent Advances in Transcription Factors Biomarkers and Targeted Therapies Focusing on Epithelial-Mesenchymal Transition

Transcription factors involve many proteins in the process of transactivating or transcribing (none-) encoded DNA to initiate and regulate downstream signals, such as RNA polymerase. Their unique characteristic is that they possess specific domains that bind to specific DNA element sequences called enhancer or promoter sequences. Epithelial-mesenchymal transition (EMT) is involved in cancer progression. Many dysregulated transcription factors-such as Myc, SNAIs, Twists, and ZEBs-are key drivers of tumor metastasis through EMT regulation. This review summarizes currently available evidence related to the oncogenic role of classified transcription factors in EMT editing and epigenetic regulation, clarifying the roles of the classified conserved transcription factor family involved in the EMT and how these factors could be used as therapeutic targets in future investigations.

Biology of breast cancer brain metastases and novel therapies targeting the blood brain barrier: an updated review

Brain metastasis (BM) is a critical cause of morbidity and mortality in patients with breast cancer (BC). Compared with other cancer cells, BC cells (BCs) exhibit special features in the metastatic process. However, the underlying mechanisms are still unclear, especially the crosstalk between tumour cells and the microenvironment. To date, novel therapies for BM, including targeted therapy and antibody‒drug conjugates, have been developed. Due to an improved understanding of the blood‒brain barrier (BBB) and blood-tumour barrier (BTB), the development and testing of therapeutic agents in clinical phases have substantially increased. However, these therapies face a major challenge due to the low penetration of the BBB or BTB. As a result, researchers have increasingly focused on finding ways to promote drug penetration through these barriers. This review provides an updated overview of breast cancer brain metastases (BCBM) and summarizes the newly developed therapies for BCBM, especially drugs targeting the BBB or BTB.

Comprehensive research into prognostic and immune signatures of transcription factor family in breast cancer

BACKGROUND

Breast cancer (BRCA) is the most common malignancy with high morbidity and mortality in women, and transcription factor (TF) is closely related to the occurrence and development of BRCA. This study was designed to identify a prognostic gene signature based on TF family to reveal immune characteristics and prognostic survival of BRCA.

METHODS

In this study, RNA-sequence with corresponding clinical data were obtained from The Cancer Genome Atlas (TCGA) and GSE42568. Prognostic differentially expressed transcription factor family genes (TFDEGs) were screened to construct a risk score model, after which BRCA patients were stratified into low-risk and high-risk groups based on their corresponding risk scores. Kaplan-Meier (KM) analysis was applied to evaluate the prognostic implication of risk score model, and a nomogram model was developed and validated with the TCGA and GSE20685. Furthermore, the GSEA revealed pathological processes and signaling pathways enriched in the low-risk and high-risk groups. Finally, analyses regarding levels of immune infiltration, immune checkpoints and chemotactic factors were all completed to investigate the correlation between the risk score and tumor immune microenvironment (TIME).

RESULTS

A prognostic 9-gene signature based on TFDEGs was selected to establish a risk score model. According to KM analyses, high-risk group witnessed a significantly worse overall survival (OS) than low-risk group in both TCGA-BRCA and GSE20685. Furthermore, the nomogram model proved great possibility in predicting the OS of BRCA patients. As indicted in GSEA analysis, tumor-associated pathological processes and pathways were relatively enriched in high-risk group, and the risk score was negatively correlated with ESTIMATE score, infiltration levels of CD4+ and CD8+T cells, as well as expression levels of immune checkpoints and chemotactic factors.

CONCLUSIONS

The prognostic model based on TFDEGs could distinguish as a novel biomarker for predicting prognosis of BRCA patients; in addition, it may also be utilized to identify potential benefit population from immunotherapy in different TIME and predict potential drug targets.

DNA methylation age in paired tumor and adjacent normal breast tissue in Chinese women with breast cancer

BACKGROUND

Few studies have examined epigenetic age acceleration (AA), the difference between DNA methylation (DNAm) predicted age and chronological age, in relation to somatic genomic features in paired cancer and normal tissue, with less work done in non-European populations. In this study, we aimed to examine DNAm age and its associations with breast cancer risk factors, subtypes, somatic genomic profiles including mutation and copy number alterations and other aging markers in breast tissue of Chinese breast cancer (BC) patients from Hong Kong.

METHODS

We performed genome-wide DNA methylation profiling of 196 tumor and 188 paired adjacent normal tissue collected from Chinese BC patients in Hong Kong (HKBC) using Illumina MethylationEPIC array. The DNAm age was calculated using Horvath's pan-tissue clock model. Somatic genomic features were based on data from RNA sequencing (RNASeq), whole-exome sequencing (WES), and whole-genome sequencing (WGS). Pearson's correlation (r), Kruskal-Wallis test, and regression models were used to estimate associations of DNAm AA with somatic features and breast cancer risk factors.

RESULTS

DNAm age showed a stronger correlation with chronological age in normal (Pearson r = 0.78, P < 2.2e-16) than in tumor tissue (Pearson r = 0.31, P = 7.8e-06). Although overall DNAm age or AA did not vary significantly by tissue within the same individual, luminal A tumors exhibited increased DNAm AA (P = 0.004) while HER2-enriched/basal-like tumors exhibited markedly lower DNAm AA (P = < .0001) compared with paired normal tissue. Consistent with the subtype association, tumor DNAm AA was positively correlated with ESR1 (Pearson r = 0.39, P = 6.3e-06) and PGR (Pearson r = 0.36, P = 2.4e-05) gene expression. In line with this, we found that increasing DNAm AA was associated with higher body mass index (P = 0.039) and earlier age at menarche (P = 0.035), factors that are related to cumulative exposure to estrogen. In contrast, variables indicating extensive genomic instability, such as TP53 somatic mutations, high tumor mutation/copy number alteration burden, and homologous repair deficiency were associated with lower DNAm AA.

CONCLUSIONS

Our findings provide additional insights into the complexity of breast tissue aging that is associated with the interaction of hormonal, genomic, and epigenetic mechanisms in an East Asian population.

Protocatechuic Aldehyde Alleviates d -Galactose-Induced Cardiomyocyte Senescence by Regulating the TCF3/ATG5 Axis

ABSTRACT

Cardiomyocyte senescence is an independent risk factor for cardiovascular diseases. Protocatechuic aldehyde (PCA) is a natural chemical in the Chinese medicinal herb Salvia miltiorrhiza . PCA could protect against oxidative stress and inflammation in the cardiovascular system. In present study, we treated H9C2 cells with d -galactose to establish an in vitro model of cardiomyocyte senescence and investigated the role and underlying mechanisms of PCA in myocardial cell senescence. It was found that d -galactose induced transcription factor 3 (TCF3) expression and decreased autophagy-related genes 5 (ATG5) expression. Meanwhile, inflammation and senescence were exacerbated by d -galactose. TCF3 transcriptionally inhibited ATG5 expression. TCF3 knockdown abolished the effects of d -galactose on H9C2 by activating ATG5-mediated autophagy. PCA hindered TCF3 and inflammation to alleviate the d -galactose-induced senescence of H9C2 cells in a dose-dependent manner. Whereas, the anti-inflammation and anti-senescence effects of PCA were reversed by TCF3 knockdown. Furthermore, absence of ATG5 partially eliminated the impacts of PCA on H9C2 cells treated with d -galactose. Conclusively, PCA alleviated d -galactose-induced senescence by downregulating TCF3, promoting ATG5-mediated autophagy, and inhibiting inflammation in H9C2 cells. These results elucidated the potential mechanism by which PCA alleviated cardiomyocyte senescence and enabled its application in treating cardiomyocyte senescence.

LINC00543 promotes colorectal cancer metastasis by driving EMT and inducing the M2 polarization of tumor associated macrophages

BACKGROUND

The interaction between the tumor-microenvironment (TME) and the cancer cells has emerged as a key player in colorectal cancer (CRC) metastasis. A small proportion of CRC cells which undergo epithelial-mesenchymal transition (EMT) facilitate the reshaping of the TME by regulating various cellular ingredients.

METHODS

Immunohistochemical analysis, RNA immunoprecipitation (RIP), RNA Antisense Purification (RAP), dual luciferase assays were conducted to investigate the biological function and regulation of LINC00543 in CRC. A series in vitro and in vivo experiments were used to clarify the role of LINC00543 in CRC metastasis.

RESULTS

Here we found that the long non-coding RNA LINC00543, was overexpressed in colorectal cancer tissues, which correlated with advanced TNM stage and poorer prognosis of CRC patients. The overexpression of LINC00543 promoted tumorigenesis and metastasis of CRC cells by enhancing EMT and remodeling the TME. Mechanistically, LINC00543 blocked the transport of pre-miR-506-3p across the nuclear-cytoplasmic transporter XPO5, thereby reducing the production of mature miR-506-3p, resulting in the increase in the expression of FOXQ1 and induction of EMT. In addition, upregulation of FOXQ1 induced the expression of CCL2 that accelerated the recruitment of macrophages and their M2 polarization.

CONCLUSIONS

Our study showed that LINC00543 enhanced EMT of CRC cells through the pre-miR-506-3p/FOXQ1 axis. This resulted in the upregulation of CCL2, leading to macrophages recruitment and M2 polarization, and ultimately stimulating the progression of CRC.

GABAergic signaling as a potential therapeutic target in cancers

GABA is the most common inhibitory neurotransmitter in the vertebrate central nervous system. Synthesized by glutamic acid decarboxylase, GABA could specifically bind with two GABA receptors to transmit inhibition signal stimuli into cells: GABAA receptor and GABAB receptor. In recent years, emerging studies revealed that GABAergic signaling not only participated in traditional neurotransmission but was involved in tumorigenesis as well as regulating tumor immunity. In this review, we summarize the existing knowledge of the GABAergic signaling pathway in tumor proliferation, metastasis, progression, stemness, and tumor microenvironment as well as the underlying molecular mechanism. We also discussed the therapeutical advances in targeting GABA receptors to provide the theoretical basis for pharmacological intervention of GABAergic signaling in cancer treatment especially immunotherapy.

Lactate, histone lactylation and cancer hallmarks

Histone lactylation, an indicator of lactate level and glycolysis, has intrinsic connections with cell metabolism that represents a novel epigenetic code affecting the fate of cells including carcinogenesis. Through delineating the relationship between histone lactylation and cancer hallmarks, we propose histone lactylation as a novel epigenetic code priming cells toward the malignant state, and advocate the importance of identifying novel therapeutic strategies or dual-targeting modalities against lactylation toward effective cancer control. This review underpins important yet less-studied area in histone lactylation, and sheds insights on its clinical impact as well as possible therapeutic tools targeting lactylation.

FBXL2 promotes E47 protein instability to inhibit breast cancer stemness and paclitaxel resistance

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with a high risk of metastasis and recurrence. Although chemotherapy has greatly improved the clinical outcome of TNBC patients, acquired drug resistance remains a huge challenge for TNBC treatment. Breast cancer stem cells (BCSCs) play a critical role in breast cancer development, metastasis, recurrence, and chemotherapy resistance. Thus, it is of great importance to decipher the underlying molecular mechanism of BCSCs regulation for TNBC drug resistance. In this study, we demonstrate that the F-box protein FBXL2 is a critical negative regulator of BCSCs stemness and that downregulation of FBXL2 plays a causal role in TNBC drug resistance. We show that expression levels of FBXL2 significantly influence CD44^high/CD24^low subpopulation and the mammosphere formation ability of TNBC cells. Ectopic expression of FBXL2 inhibits initiation of TNBC and overcomes paclitaxel resistance in vivo. In addition, activation of FBXL2 by nebivolol, a clinically used small-molecule inhibitor of the beta-1 receptor, markedly overcomes BCSCs-induced paclitaxel resistance. Mechanistically, we show that FBXL2 targets transcriptional factor E47 for polyubiquitin- and proteasome-mediated degradation, resulting in inhibition of BCSC stemness. Clinical analyses indicate that low expression of FBXL2 correlates with high expression of E47 as well as with high stemness features, and is associated with poor clinical outcomes of breast cancer patients. Taken together, these results highlight that the FBXL2-E47 axis plays a critical role in the regulation of BCSC stemness and paclitaxel resistance. Thus, targeting FBXL2 might be a potential therapeutic strategy for drug-resistant TNBC.

Epithelial–mesenchymal transition: The history, regulatory mechanism, and cancer therapeutic opportunities

Epithelial–mesenchymal transition (EMT) is a program wherein epithelial cells lose their junctions and polarity while acquiring mesenchymal properties and invasive ability. Originally defined as an embryogenesis event, EMT has been recognized as a crucial process in tumor progression. During EMT, cell–cell junctions and cell–matrix attachments are disrupted, and the cytoskeleton is remodeled to enhance mobility of cells. This transition of phenotype is largely driven by a group of key transcription factors, typically Snail, Twist, and ZEB, through epigenetic repression of epithelial markers, transcriptional activation of matrix metalloproteinases, and reorganization of cytoskeleton. Mechanistically, EMT is orchestrated by multiple pathways, especially those involved in embryogenesis such as TGFβ, Wnt, Hedgehog, and Hippo, suggesting EMT as an intrinsic link between embryonic development and cancer progression. In addition, redox signaling has also emerged as critical EMT modulator. EMT confers cancer cells with increased metastatic potential and drug resistant capacity, which accounts for tumor recurrence in most clinic cases. Thus, targeting EMT can be a therapeutic option providing a chance of cure for cancer patients. Here, we introduce a brief history of EMT and summarize recent advances in understanding EMT mechanisms, as well as highlighting the therapeutic opportunities by targeting EMT in cancer treatment.

Loxl3 Promotes Melanoma Progression and Dissemination Influencing Cell Plasticity and Survival

Simple Summary

Malignant melanoma is the most lethal skin cancer due to its aggressive clinical behavior and therapeutic resistance. A comprehensive knowledge of the molecular mechanisms underlying melanoma progression is urgently needed to improve the survival of melanoma patients. Phenotypic plasticity of melanoma cells has emerged as a key process in melanomagenesis and therapy resistance. This phenotypic plasticity is sustained by an epithelial-to-mesenchymal (EMT)-like program that favors multiple intermediate states and allows adaptation to changing microenvironments along melanoma progression. Given the essential role of lysyl oxidase-like 3 (LOXL3) in human melanoma cell survival and its contribution to EMT, we generated mice with conditional melanocyte-specific targeting of Loxl3, concomitant to Braf activation and Pten deletion. Our results supported a key role of Loxl3 for melanoma progression, metastatic dissemination, and genomic stability, and supported its contribution to melanoma phenotypic plasticity by modulating the expression of several EMT transcription factors (EMT-TFs).

Abstract

Malignant melanoma is a highly aggressive tumor causing most skin cancer-related deaths. Understanding the fundamental mechanisms responsible for melanoma progression and therapeutic evasion is still an unmet need for melanoma patients. Progression of skin melanoma and its dissemination to local or distant organs relies on phenotypic plasticity of melanoma cells, orchestrated by EMT-TFs and microphthalmia-associated TF (MITF). Recently, melanoma phenotypic switching has been proposed to uphold context-dependent intermediate cell states benefitting malignancy. LOXL3 (lysyl oxidase-like 3) promotes EMT and has a key role in human melanoma cell survival and maintenance of genomic integrity. To further understand the role of Loxl3 in melanoma, we generated a conditional Loxl3-knockout (KO) melanoma mouse model in the context of BrafV600E-activating mutation and Pten loss. Melanocyte-Loxl3 deletion increased melanoma latency, decreased tumor growth, and reduced lymph node metastatic dissemination. Complementary in vitro and in vivo studies in mouse melanoma cells confirmed Loxl3’s contribution to melanoma progression and metastasis, in part by modulating phenotypic switching through Snail1 and Prrx1 EMT-TFs. Importantly, a novel LOXL3-SNAIL1-PRRX1 axis was identified in human melanoma, plausibly relevant to melanoma cellular plasticity. These data reinforced the value of LOXL3 as a therapeutic target in melanoma.

Triptonide effectively inhibits triple-negative breast cancer metastasis through concurrent degradation of Twist1 and Notch1 oncoproteins

Background

Triple-negative breast cancer (TNBC) is highly metastatic and lethal. Due to a lack of druggable targets for this disease, there are no effective therapies in the clinic.

Methods

We used TNBC cells and xenografted mice as models to explore triptonide-mediated inhibition of TNBC metastasis and tumor growth. Colony formation assay was used to quantify the tumorigenesis of TNBC cells. Wound-healing and cell trans-well assays were utilized to measure cell migration and invasion. Tube formation assay was applied to access tumor cell-mediated vasculogenic mimicry. Western blot, quantitative-PCR, immunofluorescence imaging, and immunohistochemical staining were used to measure the expression levels of various tumorigenic genes in TNBC cells.

Results

Here, we showed that triptonide, a small molecule from the traditional Chinese medicinal herb Tripterygium wilfordii Hook F, potently inhibited TNBC cell migration, invasion, and vasculogenic mimicry, and effectively suppressed TNBC tumor growth and lung metastasis in xenografted mice with no observable toxicity. Molecular mechanistic studies revealed that triptonide strongly triggered the degradation of master epithelial-mesenchymal transition (EMT)-inducing protein Twist1 through the lysosomal system and reduced Notch1 expression and NF-κB phosphorylation, which consequently diminished the expression of pro-metastatic and angiogenic genes N-cadherin, VE-cadherin, and vascular endothelial cell growth factor receptor 2 (VEGFR2).

Conclusions

Triptonide effectively suppressed TNBC cell tumorigenesis, vasculogenic mimicry, and strongly inhibited the metastasis of TNBC via degradation of Twist1 and Notch1 oncoproteins, downregulation of metastatic and angiogenic gene expression, and reduction of NF-κB signaling pathway. Our findings provide a new strategy for treating highly lethal TNBC and offer a potential new drug candidate for combatting this aggressive disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-021-01488-7.