Cooperative interaction between ERα and the EMT-inducer ZEB1 reprograms breast cancer cells for bone metastasis

Inhibition of mitochondrial genome-encoded mitomiR-3 contributes to ZEB1 mediated GPX4 downregulation and pro-ferroptotic lipid metabolism to induce ferroptosis in breast cancer cells

Ferroptosis, an iron-dependent form of regulated cell death driven by lipid peroxidation, represents a unique vulnerability in cancer cells. However, current ferroptosis-inducing therapies face clinical limitations due to poor cancer cell specificity, systemic toxicity, and off-target effects. Therefore, a deeper understanding of molecular regulators of ferroptosis sensitivity is critical for developing targeted therapies. The metabolic plasticity of cancer cells determines their sensitivity to ferroptosis. While mitochondrial dysfunction contributes to metabolic reprogramming in cancer, its role in modulating ferroptosis remains poorly characterized. Previously, studies have identified that mitochondrial genome also encodes several non-coding RNAs. We identified 13 novel mitochondrial genome-encoded miRNAs (mitomiRs) that are aberrantly overexpressed in triple-negative breast cancer (TNBC) cell lines and patient tumors. We observed higher levels of mitomiRs in basal-like triple-negative breast cancer (TNBC) cells compared to mesenchymal stem-like TNBC cells. Strikingly, 11 of these mitomiRs directly target the 3'UTR of ZEB1, a master regulator of epithelial-to-mesenchymal transition (EMT). Using mitomiR-3 mimic, inhibitor and sponges, we demonstrated its role as a key regulator of ZEB1 expression in TNBC cells. Inhibition of mitomiR-3 via sponge construct in basal-like TNBC, MDA-MB-468 cells, promoted ZEB1 upregulation and induced a mesenchymal phenotype. Further, mitomiR-3 inhibition in TNBC cells contributed to reduced cancer cell proliferation, migration, and invasion. Mechanistically, mitomiR-3 inhibition in TNBC cells promote metabolic reprogramming toward pro-ferroptotic pathways, including iron accumulation, increased polyunsaturated fatty acid (PUFA) metabolites, and lipid peroxidation, contributing to ferroptotic cell death via ZEB1-mediated downregulation of GPX4, a critical ferroptosis defense enzyme. We observed that mitomiR-3 inhibition significantly suppressed tumor growth in vivo. Our identified mitomiR-3 has low expression in normal breast cells, minimizing potential off-target toxicity, making them a promising target for pro-ferroptotic cancer therapy. Our study reveals a novel link between mitochondrial miRNAs and ferroptosis sensitivity in TNBC paving a way for miRNA-based therapeutics.

Estrogen-induced FXR1 promotes endocrine resistance and bone metastasis in breast cancer via BCL2 and GPX4

Estrogen signaling dysregulation plays a critical role in the development of anti-estrogen resistance and bone metastasis of ER+ mammary carcinoma. Using quantitative proteomic screening, we identified FXR1 as an estrogen-regulated RNA-binding protein associated with anti-estrogen resistance. Mechanistically, estrogen and IGF1 facilitate FXR1 protein translation via the PI3K/AKT/mTOR/EIF4E pathway. FXR1 enhances cellular resistance to apoptosis and ferroptosis by facilitating the maturation of BCL2 pre-mRNA and stabilizing GPX4 mRNA, respectively. Anti-estrogen resistant cells exhibit elevated FXR1 expression, and FXR1 depletion restores their sensitivity to tamoxifen. Moreover, combining FXR1 depletion with a ferroptosis inducer induces synergistic lethal in anti-estrogen resistant cells. Finally, we provide proof-of-concept evidence supporting FXR1 antagonism as a potential treatment for bone metastases in ER+ breast cancer. Our findings highlight FXR1 as a promising therapeutic target to improve existing therapeutic regimes for ER+ breast cancer patients.

Dualistic role of ZEB1 and ZEB2 in tumor progression

It is generally accepted that ZEB1 and ZEB2 act as master regulators of the epithelial-mesenchymal transition, which arguably is the key mechanism of metastasis. Accordingly, they are deemed as negative predictors of the survival of cancer patients by promoting the emergence of secondary foci of the disease. Paradoxically, in some types of cancer types the opposite effect is observed, i.e. ZEB1 and ZEB2 are associated with better prognosis for cancer patients. In this review, we discuss the hypothesis that the tumorigenic effects of ZEB1/ZEB2 can be different in various tissues depending on the initial status of these proteins in the corresponding healthy tissues. Emerging evidence suggests that ZEB1 and ZEB2 are constitutively expressed in several healthy tissues, performing vital functions. Consequently, reducing the expression of ZEB1 and ZEB2 could negatively affect these tissues causing various diseases, including cancer. Finally, the dualistic role of ZEB1 and ZEB2 as immune modulators and their effect on tumor microenvironment is also discussed.

Metastasis and chemoresistance in breast cancer: Crucial function of ZEB1/2 proteins

Breast cancer remains one of the leading causes of mortality worldwide. While advancements in chemotherapy, immunotherapy, radiotherapy, and targeted therapies have significantly improved breast cancer treatment, many patients are diagnosed at advanced stages, where tumor cells exhibit aggressive behavior and therapy resistance. Understanding the mechanisms driving breast cancer progression is therefore critical. Metastasis is a major factor that drastically reduces patient prognosis and survival, accounting for most breast cancer-related deaths. ZEB proteins have emerged as key regulators of cancer metastasis. Beyond their role in metastasis, ZEB proteins also influence drug resistance. This review focuses on the role of ZEB1 and ZEB2 in regulating breast cancer metastasis. These proteins interact with components of the tumor microenvironment (TME) to drive cancer progression and metastasis. Additionally, ZEB proteins regulate angiogenesis through interactions with VEGF. Targeting ZEB proteins offers potential therapeutic benefits, particularly for aggressive breast cancer subtypes such as triple-negative breast cancer (TNBC), which often show poor therapeutic response. ZEB proteins also influence the sensitivity of breast cancer cells to chemotherapy, making them promising targets for enhancing treatment efficacy. Given their upregulation in breast cancer, ZEB proteins can serve as valuable diagnostic and prognostic markers.

TRIM44 facilitates aggressive behaviors in multiple myeloma through promoting ZEB1 deubiquitination

BACKGROUND

Tripartite motif-containing 44 (TRIM44) involves in various tumor development. This study investigated role of TRIM44 in multiple myeloma (MM).

MATERIALS AND METHODS

TRIM44 levels in bone marrow tissues and MM cell lines was detected by quantitative reverse transcription PCR (RT-qPCR). Cell viability, migration, and invasion of MM cells were evaluated under the interference of TRIM44 expression. The role of TRIM44 on regulating tumor growth in vivo was also investigated in subcutaneous tumor xenograft models. The protein interact between TRIM44 and Zinc Finger E-Box Binding Homeobox 1 (ZEB1) was also studied according IP followed by western blotting assay.

RESULTS

TRIM44 was all highly expressed in collected bone marrow tissues and MM cell lines. Cell viability, migration, and invasion of MM cells with low expression of TRIM44 was significantly inhibited. Over-expression of TRIM44 can down-regulate the ZEB1 ubiquitination to enhance the protein stability.

CONCLUSIONS

TRIM44 exerts as an oncogenic factor to induce the oncogenesis of MM by stabilizing ZEB1.

Metabolic Reprogramming and Adaption in Breast Cancer Progression and Metastasis

Recent evidence has revealed that cancer is not solely driven by genetic abnormalities but also by significant metabolic dysregulation. Cancer cells exhibit altered metabolic demands and rewiring of cellular metabolism to sustain their malignant characteristics. Metabolic reprogramming has emerged as a hallmark of cancer, playing a complex role in breast cancer initiation, progression, and metastasis. The different molecular subtypes of breast cancer exhibit distinct metabolic genotypes and phenotypes, offering opportunities for subtype-specific therapeutic approaches. Cancer-associated metabolic phenotypes encompass dysregulated nutrient uptake, opportunistic nutrient acquisition strategies, altered utilization of glycolysis and TCA cycle intermediates, increased nitrogen demand, metabolite-driven gene regulation, and metabolic interactions with the microenvironment. The tumor microenvironment, consisting of stromal cells, immune cells, blood vessels, and extracellular matrix components, influences metabolic adaptations through modulating nutrient availability, oxygen levels, and signaling pathways. Metastasis, the process of cancer spread, involves intricate steps that present unique metabolic challenges at each stage. Successful metastasis requires cancer cells to navigate varying nutrient and oxygen availability, endure oxidative stress, and adapt their metabolic processes accordingly. The metabolic reprogramming observed in breast cancer is regulated by oncogenes, tumor suppressor genes, and signaling pathways that integrate cellular signaling with metabolic processes. Understanding the metabolic adaptations associated with metastasis holds promise for identifying therapeutic targets to disrupt the metastatic process and improve patient outcomes. This chapter explores the metabolic alterations linked to breast cancer metastasis and highlights the potential for targeted interventions in this context.

Partial Inhibition of Epithelial-to-Mesenchymal Transition (EMT) Phenotypes by Placenta-Derived DBMSCs in Human Breast Cancer Cell Lines, In Vitro

Stem cell-based therapies hold significant potential for cancer treatment due to their unique properties, including migration toward tumor niche, secretion of bioactive molecules, and immunosuppression. Mesenchymal stem cells (MSCs) from adult tissues can inhibit tumor progression, angiogenesis, and apoptosis of cancer cells. We have previously reported the isolation and characterization of placenta-derived decidua basalis mesenchymal stem cells (DBMSCs), which demonstrated higher levels of pro-migratory and anti-apoptotic genes, indicating potential anti-cancer effects. In this study, we analyzed the anti-cancer effects of DBMSCs on human breast cancer cell lines MDA231 and MCF7, with MCF 10A used as control. We also investigated how these cancer cells lines affect the functional competence of DBMSCs. By co-culturing DBMSCs with cancer cells, we analyzed changes in functions of both cell types, as well as alterations in their genomic and proteomic profile. Our results showed that treatment with DBMSCs significantly reduced the functionality of MDA231 and MCF7 cells, while MCF 10A cells remained unaffected. DBMSC treatment decreased epithelial-to-mesenchymal transition (EMT)-related protein levels in MDA231 cells and modulated expression of other cancer-related genes in MDA231 and MCF7 cells. Although cancer cells reduced DBMSC proliferation, they increased their expression of anti-apoptotic genes. These findings suggest that DBMSCs can inhibit EMT-related proteins and reduce the invasive characteristics of MDA231 and MCF7 breast cancer cells, highlighting their potential as candidates for cell-based cancer therapies.

Influence of Epithelial-Mesenchymal Transition on Risk of Relapse and Outcome to Eribulin or Cyclin-Dependent Kinase Inhibitors in Metastatic Breast Cancer

PURPOSE

The presence of epithelial-mesenchymal transition (EMT) in breast cancer (BC) cells has been linked to worse prognosis and may influence response to systemic treatment. We explored the effect of EMT in tumor samples of patients with metastatic BC on disease-free interval and overall survival in those patients receiving eribulin or cyclin-dependent kinase 4/6 inhibitors (CDK4/6i).

MATERIALS AND METHODS

Key inclusion criteria included available archived primary BC tissue and, where available, matched metastatic biopsy. Patients received eribulin and/or a CDK4/6i in the metastatic setting. Specimens were assessed for biomarkers by immunohistochemistry (CDH1, AE1/3, VIM, CDH2, ZEB1, pSMAD2, and SMAD4) and gene expression by droplet digital polymerase chain reaction (CDH1, CDH2, SNAI1 & 2, TWIST1, VIM, PTEN, and ZEB1 & 2).

RESULTS

Between 2002 and 2020, 127 patients were included (95 early-stage disease at diagnosis with metastatic relapse, 32 de novo metastatic disease). In metastatic samples, presence of ZEB1 overexpression was associated with shorter time to recurrence (48.1 months shorter; P = .003), with pSMAD2 overexpression suggesting clinical significance of 52.0 months shorter; P = .01. High gene expression levels for SNAIL1, TWIST1, and PTEN in the primary BC were associated with significantly longer survival in patients who received eribulin (P < .05); high VIM was associated with a clinically relevant trend toward shorter survival after a CDK4/6i (P = .013).

CONCLUSION

We demonstrate in our exploratory study that biomarkers involved in the process of EMT could have a prognostic impact in a cohort of patients with BC uniformly treated and with long-term follow-up. Genes known to be involved in EMT were associated with improved eribulin efficacy, while suggesting a poorer outcome with CDK4/6i.

SPP1+ TAM Regulates the Metastatic Colonization of CXCR4+ Metastasis-Associated Tumor Cells by Remodeling the Lymph Node Microenvironment

Lymph node metastasis, the initial step in distant metastasis, represents a primary contributor to mortality in patients diagnosed with oral squamous cell carcinoma (OSCC). However, the underlying mechanisms of lymph node metastasis in OSCC remain incompletely understood. Here, the transcriptomes of 56 383 single cells derived from paired tissues of six OSCC patients are analyzed. This study founds that CXCR4+ epithelial cells, identified as highly malignant disseminated tumor cells (DTCs), exhibited a propensity for lymph node metastasis. Importantly, a distinct subset of tumor-associated macrophages (TAMs) characterized by exclusive expression of phosphoprotein 1 (SPP1) is discovered. These TAMs may remodel the metastatic lymph node microenvironment by potentially activating fibroblasts and promoting T cell exhaustion through SPP1-CD44 and CD155-CD226 ligand-receptor interactions, thereby facilitating colonization and proliferation of disseminated tumor cells. The research advanced the mechanistic understanding of metastatic tumor microenvironment (TME) and provided a foundation for the development of personalized treatments for OSCC patients with metastasis.

Divergent iron regulatory states contribute to heterogeneity in breast cancer aggressiveness

Contact with dense collagen I (Col1) can induce collective invasion of triple negative breast cancer (TNBC) cells and transcriptional signatures linked to poor patient prognosis. However, this response is heterogeneous and not well understood. Using phenotype-guided sequencing analysis of invasive vs. noninvasive subpopulations, we show that these two phenotypes represent opposite sides of the iron response protein 1 (IRP1)-mediated response to cytoplasmic labile iron pool (cLIP) levels. Invasive cells upregulate iron uptake and utilization machinery characteristic of a low cLIP response, which includes contractility regulating genes that drive migration. Non-invasive cells upregulate iron sequestration machinery characteristic of a high cLIP response, which is accompanied by upregulation of actin sequestration genes. These divergent IRP1 responses result from Col1-induced transient expression of heme oxygenase I (HO-1), which cleaves heme and releases iron. These findings lend insight into the emerging theory that heme and iron fluxes regulate TNBC aggressiveness.

Monitoring Partial EMT Dynamics through Cell Mechanics Using Scanning Ion Conductance Microscopy

Tumor cells undergo an epithelial-mesenchymal transition (EMT) accompanied by a reduction in elasticity to initiate metastasis. However, in vivo, tumor cells typically exhibit partial EMT rather than fully EMT. Whether cell mechanics can accurately identify the status of partial EMT, especially the dynamic process, remains unclear. To elucidate the relationship between cell mechanics and partial EMT, we employed scanning ion conductance microscopy (SICM) to analyze the dynamic changes in cell mechanics during the TGFβ-induced partial EMT of HCT116 colon cancer cells. Cells undergoing partial EMT, characterized by increased expression of EMT transcription factors, Snai1 and Zeb1, and EMT-related genes, Fn1 and MMP9, while retaining the expression of the epithelial markers E-cadherin (E-cad) and EpCAM, did not exhibit significant changes in cell morphology, suggesting that morphological changes alone were inadequate for identifying partial EMT status. However, cell elasticity markedly decreased in partial EMT cells, and this reduction was reversed with the reversible transition of partial EMT. These findings suggest a strong correlation between cell mechanics and the dynamic process of partial EMT, indicating that cell mechanics could serve as a valuable label-free marker for identifying the status of partial EMT while preserving the physiological characteristics of tumor cells.

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.

Single-cell landscape of intratumoral heterogeneity and tumor microenvironment remolding in pre-nodal metastases of breast cancer

BACKGROUND

The metastasis of cancer cells is influenced by both their intrinsic characteristics and the tumor microenvironment (TME). However, the molecular mechanisms underlying pre-nodal metastases of breast cancer remain unclear.

METHODS

We integrated a total of 216,963 cells from 54 samples across 6 single-cell datasets to profile the cellular landscape differences between primary tumors and pre-nodal metastases.

RESULTS

We revealed three distinct metastatic epithelial cell subtypes (Epi1, Epi2 and Epi3), which exhibited different metastatic mechanisms. Specifically, the marker gene KCNK15 of the Epi1 subtype exhibited increased gene expression along the cell differentiation trajectory and was specifically regulated by the transcription factor ASCL1. In the Epi3 subtype, we highlighted NR2F1 as a regulator targeting the marker gene MUCL1. Additionally, we found that the Epi2 and Epi3 subtypes shared some regulons, such as ZEB1 and NR2C1. Similarly, we identified specific subtypes of stromal and immune cells in the TME, and discovered that vascular cancer-associated fibroblasts might promote capillary formation through CXCL9+ macrophages in pre-nodal metastases. All three subtypes of metastatic epithelial cells were associated with poor prognosis.

CONCLUSIONS

In summary, this study dissects the intratumoral heterogeneity and remodeling of the TME in pre-nodal metastases of breast cancer, providing novel insights into the mechanisms underlying breast cancer metastasis.

Transcription factor ZEB1 coordinating with NuRD complex to promote oncogenesis through glycolysis in colorectal cancer

Background

Colorectal cancer (CRC) is an aggressive primary intestinal malignancy with the third-highest incidence and second-highest mortality among all cancer types worldwide. Transcription factors (TFs) regulate cell development and differentiation owing to their ability to recognize specific DNA sequences upstream of genes. Numerous studies have demonstrated a strong correlation between TFs, the etiology of tumors, and therapeutic approaches. Here, we aimed to explore prognosis-related TFs and comprehend their carcinogenic mechanisms, thereby offering novel insights into the diagnosis and management of CRC.

Materials and Methods

Differentially expressed TFs between CRC and normal tissues were identified leveraging The Cancer Genome Atlas database, Weighted correlation network analysis and Cox regression analysis were performed to identify prognosis-related TFs. The cellular functions of hub TF zinc finger E-box binding homeobox 1 (ZEB1) were determined using by 5-ethynyl-2'-deoxyuridine and cell invasion assays in CRC cells. RNA-sequencing, Kyoto Encyclopedia of Genes and Genomes enrichment, and gene set enrichment analyses were used to identify the cellular processes in which ZEB1 participates. Immunoaffinity purification, silver staining mass spectrometry, and a chromatin immunoprecipitation assay were conducted to search for proteins that might interact with ZEB1 and the target genes they jointly regulate.

Results

Thirteen central TFs related to prognosis were identified through bioinformatics analysis techniques. Among these TFs, ZEB1 emerged as the TF most closely associated with CRC, as determined through a combination of regulatory network diagrams, survival curves, and phenotype analyses. ZEB1 promotes CRC cell growth by recruiting the NuRD(MTA1) complex, and the ZEB1/NuRD(MTA1) complex transcriptionally represses glycolysis-associated tumor suppressor genes.

Conclusion

Our study not only identified a hub biomarker related to CRC prognosis but also revealed the specific molecular mechanisms through which ZEB1 affects cancer progression. These insights provide crucial evidence for the diagnosis of CRC and potential treatment opportunities.

Hypoxia makes EZH2 inhibitor not easy-advances of crosstalk between HIF and EZH2

Histone methylation plays a crucial role in tumorigenesis. Enhancer of zeste homolog 2 (EZH2) is a histone methyltransferase that regulates chromatin structure and gene expression. EZH2 inhibitors (EZH2is) have been shown to be effective in treating hematologic malignancies, while their effectiveness in solid tumors remains limited. One of the major challenges in the treatment of solid tumors is their hypoxic tumor microenvironment. Hypoxia-inducible factor 1-alpha (HIF-1α) is a key hypoxia responder that interacts with EZH2 to promote tumor progression. Here we discuss the implications of the relationship between EZH2 and hypoxia for expanding the application of EZH2is in solid tumors.

GET: a foundation model of transcription across human cell types

Transcriptional regulation, involving the complex interplay between regulatory sequences and proteins, directs all biological processes. Computational models of transcription lack generalizability to accurately extrapolate in unseen cell types and conditions. Here, we introduce GET, an interpretable foundation model designed to uncover regulatory grammars across 213 human fetal and adult cell types. Relying exclusively on chromatin accessibility data and sequence information, GET achieves experimental-level accuracy in predicting gene expression even in previously unseen cell types. GET showcases remarkable adaptability across new sequencing platforms and assays, enabling regulatory inference across a broad range of cell types and conditions, and uncovering universal and cell type specific transcription factor interaction networks. We evaluated its performance on prediction of regulatory activity, inference of regulatory elements and regulators, and identification of physical interactions between transcription factors. Specifically, we show GET outperforms current models in predicting lentivirus-based massive parallel reporter assay readout with reduced input data. In fetal erythroblasts, we identify distal (>1Mbp) regulatory regions that were missed by previous models. In B cells, we identified a lymphocyte-specific transcription factor-transcription factor interaction that explains the functional significance of a leukemia-risk predisposing germline mutation. In sum, we provide a generalizable and accurate model for transcription together with catalogs of gene regulation and transcription factor interactions, all with cell type specificity.

LncRNA-SERB promotes vasculogenic mimicry (VM) formation and tumor metastasis in renal cell carcinoma

A growing body of evidence shows that vasculogenic mimicry (VM) is closely related to the invasion and metastasis of many tumor cells. Although the estrogen receptor (ER) can promote initiation and progression of renal cell carcinoma (RCC), how the downstream biomolecules are involved, and the detailed mechanisms of how ER expression is elevated in RCC remain to be further elucidated. Here, we discovered that long noncoding RNA (LncRNA)-SERB is highly expressed in tumor cells of RCC patients. We used multiple RCC cells and an in vivo mouse model for our study, and results indicated that LncRNA-SERB could boost RCC VM formation and cell invasion in vitro and in vivo. Although a previous report showed that ERβ can affect the VM formation in RCC, it is unclear which factor could upregulate ERβ. This is the first study to show LncRNA-SERB can be the upstream regulator of ERβ to control RCC progression. Mechanistically, LncRNA-SERB may increase ERβ via binding to the promoter area, and ERβ functions through transcriptional regulation of zinc finger E-box binding homeobox 1 (ZEB1) to regulate VM formation. These results suggest that LncRNA-SERB promotes RCC cell VM formation and invasion by upregulating the ERβ/ZEB1 axis and that therapeutic targeting of this newly identified pathway may better inhibit RCC progression.

A prognostic and immune related risk model based on zinc homeostasis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide. The dysfunction of zinc homeostasis participates in the early and advancing malignancy of HCC. However, the prognostic ability of zinc homeostasis in HCC has not been clarified yet. Here, we showed a zinc-homeostasis related risk model in HCC. Five signature genes including ADAMTS5, PLOD2, PTDSS2, KLRB1, and UCK2 were screened out via survival analyses and regression algorithms to construct the nomogram with clinical characteristics. Experimental researches indicated that UCK2 participated in the progression of HCC. Patients with higher risk scores always had worse outcomes and were more associated with immune suppression according to the analyses of immune related-pathway activation, cell infiltration, and gene expression. Moreover, these patients were likely to exhibit more sensitivity to sorafenib and other antitumor drugs. This study highlights the significant prognostic role of zinc homeostasis and suggests potential treatment strategies in HCC.

Hydrostatic pressure mediates epithelial-mesenchymal transition of cholangiocytes through RhoA/ROCK and TGF-β/smad pathways

Biomechanical cue within the tissue microenvironment is known to play a critical role in regulating cell behaviors and maintaining tissue homeostasis. As hydrostatic pressure often increases in biliary system under pathological states, we investigated the effect of the moderate elevation of the hydrostatic pressure on biliary epithelial cells, especially on the epithelial-mesenchymal transition (EMT). Human intrahepatic biliary epithelial cells were loaded to hydrostatic pressure using a commercial device. We found that loading the cells to 50 mmHg hydrostatic pressure induced obvious morphological changes and significantly upregulated vimentin, ZEB1, and pSmad2/3, fibronectin, and collagen 1α. All changes induced by hydrostatic pressure loading were effectively mitigated by either ROCK inhibitor (Y-27632) or ALK5 inhibitor (SB-431542). Our in vitro experimental data suggests that hydrostatic pressure loading induces EMT of cholangiocytes through RhoA/ROCK and TGF-β/Smad pathways. Elevated hydrostatic pressure in biliary duct system under pathological states may promote the biliary epithelial cells shifting to profibrotic and mesenchymal characteristics.

Cancer-associated fibroblast-secreted FGF7 as an ovarian cancer progression promoter

BACKGROUND

Ovarian cancer (OC) is distinguished by its aggressive nature and the limited efficacy of current treatment strategies. Recent studies have emphasized the significant role of cancer-associated fibroblasts (CAFs) in OC development and progression.

METHODS

Employing sophisticated machine learning techniques on bulk transcriptomic datasets, we identified fibroblast growth factor 7 (FGF7), derived from CAFs, as a potential oncogenic factor. We investigated the relationship between FGF7 expression and various clinical parameters. A series of in vitro experiments were undertaken to evaluate the effect of CAFs-derived FGF7 on OC cell activities, such as proliferation, migration, and invasion. Single-cell transcriptomic analysis was also conducted to elucidate the interaction between FGF7 and its receptor. Detailed mechanistic investigations sought to clarify the pathways through which FGF7 fosters OC progression.

RESULTS

Our findings indicate that higher FGF7 levels correlate with advanced tumor stages, increased vascular invasion, and poorer prognosis. CAFs-derived FGF7 significantly enhanced OC cell proliferation, migration, and invasion. Single-cell analysis and in vitro studies revealed that CAFs-derived FGF7 inhibits the ubiquitination and degradation of hypoxia-inducible factor 1 alpha (HIF-1α) via FGFR2 interaction. Activation of the FGF7/HIF-1α pathway resulted in the upregulation of mesenchymal markers and downregulation of epithelial markers. Importantly, in vivo treatment with neutralizing antibodies targeting CAFs-derived FGF7 substantially reduced tumor growth.

CONCLUSION

Neutralizing FGF7 in the medium or inhibiting HIF-1α signaling reversed the effects of FGF7-mediated EMT, emphasizing the dependence of FGF7-mediated EMT on HIF-1α activation. These findings suggest that targeting the FGF7/HIF-1α/EMT axis may offer new therapeutic opportunities to intervene in OC progression.

The mechanism of PFK-1 in the occurrence and development of bladder cancer by regulating ZEB1 lactylation

BACKGROUND

Bladder cancer (BC) is one of the most common malignancies of the genitourinary system. Phosphofructokinase 1 (PFK-1) is one of member of PFK, which plays an important role in reprogramming cancer metabolism, such as lactylation modification. Zinc finger E-box-binding homeobox 1 (ZEB1) has been demonstrated to be a oncogene in many cancers. Therefore, this study was performed to explore the effects of PFK-1 on the lactylation of ZEB1 in BC development.

METHODS

Cell viability was measured using the CCK-8 kit. The glucose assay kit and lactate assay kit were used to detect glucose utilization and lactate production. The DNA was purified and quantified by qRT-PCR.

RESULTS

In the present study, we found that ZEB1 expression levels were significantly elevated in bladder cancer cells. Impaired PFK-1 expression inhibits proliferation, migration, and invasion of BC cells and suppresses tumour growth in vivo. We subsequently found that knockdown of PFK-1 decreases glycolysis, including reduced glucose consumption, lactate production and total extracellular acidification rate (ECAR). Mechanistically, PFK-1 inhibits histone lactylation of bladder cancer cells, and thus inhibits the transcription activity of ZEB1.

CONCLUSION

Our results suggest that PFK-1 can inhibit the malignant phenotype of bladder cancer cells by mediating the lactylation of ZEB1. These findings suggested PFK-1 to be a new potential target for bladder cancer therapy.

Divergent iron-regulatory states contribute to heterogeneity in breast cancer aggressiveness

Primary tumors with similar mutational profiles can progress to vastly different outcomes where transcriptional state, rather than mutational profile, predicts prognosis. A key challenge is to understand how distinct tumor cell states are induced and maintained. In triple negative breast cancer cells, invasive behaviors and aggressive transcriptional signatures linked to poor patient prognosis can emerge in response to contact with collagen type I. Herein, collagen-induced migration heterogeneity within a TNBC cell line was leveraged to identify transcriptional programs associated with invasive versus non-invasive phenotypes and implicate molecular switches. Phenotype-guided sequencing revealed that invasive cells upregulate iron uptake and utilization machinery, anapleurotic TCA cycle genes, actin polymerization promoters, and a distinct signature of Rho GTPase activity and contractility regulating genes. The non-invasive cell state is characterized by actin and iron sequestration modules along with glycolysis gene expression. These unique tumor cell states are evident in patient tumors and predict divergent outcomes for TNBC patients. Glucose tracing confirmed that non-invasive cells are more glycolytic than invasive cells, and functional studies in cell lines and PDO models demonstrated a causal relationship between phenotype and metabolic state. Mechanistically, the OXPHOS dependent invasive state resulted from transient HO-1 upregulation triggered by contact with dense collagen that reduced heme levels and mitochondrial chelatable iron levels. This induced expression of low cytoplasmic iron response genes regulated by ACO1/IRP1. Knockdown or inhibition of HO-1, ACO1/IRP1, MRCK, or OXPHOS abrogated invasion. These findings support an emerging theory that heme and iron flux serve as important regulators of TNBC aggressiveness.

Package delivered: folate receptor-mediated transporters in cancer therapy and diagnosis

Neoplasias pose a significant threat to aging society, underscoring the urgent need to overcome the limitations of traditional chemotherapy through pioneering strategies. Targeted drug delivery is an evolving frontier in cancer therapy, aiming to enhance treatment efficacy while mitigating undesirable side effects. One promising avenue utilizes cell membrane receptors like the folate receptor to guide drug transporters precisely to malignant cells. Based on the cellular folate receptor as a cancer cell hallmark, targeted nanocarriers and small molecule-drug conjugates have been developed that comprise different (bio) chemistries and/or mechanical properties with individual advantages and challenges. Such modern folic acid-conjugated stimuli-responsive drug transporters provide systemic drug delivery and controlled release, enabling reduced dosages, circumvention of drug resistance, and diminished adverse effects. Since the drug transporters' structure-based de novo design is increasingly relevant for precision cancer remediation and diagnosis, this review seeks to collect and debate the recent approaches to deliver therapeutics or diagnostics based on folic acid conjugated Trojan Horses and to facilitate the understanding of the relevant chemistry and biochemical pathways. Focusing exemplarily on brain and breast cancer, recent advances spanning 2017 to 2023 in conjugated nanocarriers and small molecule drug conjugates were considered, evaluating the chemical and biological aspects in order to improve accessibility to the field and to bridge chemical and biomedical points of view ultimately guiding future research in FR-targeted cancer therapy and diagnosis.

The Role of Breast Cancer Cells in Bone Metastasis: Suitable Seeds for Nourishing Soil

PURPOSE OF REVIEW

The purpose of this review was to describe the characteristics of breast cancer cells prone to developing bone metastasis and determine how they are regulated by the bone microenvironment.

RECENT FINDINGS

The bone is a site of frequent breast cancer metastasis. Bone metastasis accounts for 70% of advanced breast cancer cases and remains incurable. It can lead to skeletal-related events, such as bone fracture and pain, and seriously affect the quality of life of patients. Breast cancer cells escape from the primary lesion and spread to the bone marrow in the early stages. They can then enter the dormant state and restore tumourigenicity after several years to develop overt metastasis. In the last few years, an increasing number of studies have reported on the factors promoting bone metastasis of breast cancer cells, both at the primary and metastatic sites. Identifying factors associated with bone metastasis aids in the early recognition of bone metastasis tendency. How to target these factors and minimize the side effects on the bone remains to be further explored.

Distinguished biomimetic dECM system facilitates early detection of metastatic breast cancer cells

Breast cancer is the most prevalent malignant tumor affecting women's health. Bone is the most common distant metastatic organ, worsening the quality of life and increasing the mortality of patients. Early detection of breast cancer bone metastasis is urgent for halting disease progression and improving tumor prognosis. Recently, extracellular matrix (ECM) with biomimetic tissue niches opened a new avenue for tumor models in vitro. Here, we developed a biomimetic decellularized ECM (dECM) system to recapitulate bone niches at different situations, bone mimetic dECM from osteoblasts (BM-ECM) and bone tumor mimetic dECM from osteosarcoma cells (OS-ECM). The two kinds of dECMs exhibited distinct morphology, protein composition, and distribution. Interestingly, highly metastatic breast cancer cells tended to adhere and migrate on BM-ECM, while lowly metastatic breast cancer cells preferred the OS-ECM niche. Epithelial-to-mesenchymal transition was a potential mechanism to initiate the breast cancer cell migration on different biomimetic dECMs. Importantly, in the nude mice model, the dECM system captured metastatic breast cancer cells as early as 10 days after orthotopic transplantation in mammary gland pads, with higher signal on BM-ECM than that on OS-ECM. Collectively, the biomimetic dECM system might be a promising tumor model to distinguish the metastatic ability of breast cancer cells in vitro and to facilitate early detection of metastatic breast cancer cells in vivo, contributing to the diagnosis of breast cancer bone metastasis.

Altered Phenotypes of Breast Epithelial × Breast Cancer Hybrids after ZEB1 Knock-Out

ZEB1 plays a pivotal role in epithelial-to-mesenchymal transition (EMT), (cancer) cell stemness and cancer therapy resistance. The M13HS tumor hybrids, which were derived from spontaneous fusion events between the M13SV1-EGFP-Neo breast epithelial cells and HS578T-Hyg breast cancer cells, express ZEB1 and exhibit prospective cancer stem cell properties. To explore a possible correlation between the ZEB1 and stemness/ EMT-related properties in M13HS tumor hybrids, ZEB1 was knocked-out by CRISPR/Cas9. Colony formation, mammosphere formation, cell migration, invasion assays, flow cytometry and Western blot analyses were performed for the characterization of ZEB1 knock-out cells. The ZEB1 knock-out in M13HS tumor cells was not correlated with the down-regulation of the EMT-related markers N-CADHERIN (CDH2) and VIMENTIN and up-regulation of miR-200c-3p. Nonetheless, both the colony formation and mammosphere formation capacities of the M13HS ZEB1 knock-out cells were markedly reduced. Interestingly, the M13HS-2 ZEB1-KO cells harbored a markedly higher fraction of ALDH1-positive cells. The Transwell/ Boyden chamber migration assay data indicated a reduced migratory activity of the M13HS ZEB1-knock-out tumor hybrids, whereas in scratch/ wound-healing assays only the M13SH-8 ZEB1-knock-out cells possessed a reduced locomotory activity. Similarly, only the M13HS-8 ZEB1-knock-out tumor hybrids showed a reduced invasion capacity. Although the ZEB1 knock-out resulted in only moderate phenotypic changes, our data support the role of ZEB1 in EMT and stemness.

miR-4739 promotes epithelial-mesenchymal transition and angiogenesis in "driver gene-negative" non-small cell lung cancer via activating the Wnt/β-catenin signaling

PURPOSE

"Driver gene-negative" non-small cell lung cancer (NSCLC) currently has no approved targeted drug, due to the lack of common actionable driver molecules. Even though miRNAs play crucial roles in various malignancies, their roles in "driver gene-negative" NSCLC keep unclear.

METHODS

miRNA expression microarrays were utilized to screen miRNAs associated with "driver gene-negative" NSCLC malignant progression. Quantitative real-time PCR (RT-qPCR) and in situ hybridization (ISH) were employed to validate the expression of miR-4739, and its correlation with clinicopathological characteristics was analyzed in tumor specimens using univariate and multivariate analyses. The biological functions and underlying mechanisms of miR-4739 were investigated both in vitro and in vivo.

RESULTS

our research demonstrated, for the first time, that miR-4739 was substantially increased in "driver gene-negative" NSCLC tumor tissues and cell lines, and overexpression of miR-4739 was related to clinical staging, metastasis, and unfavorable outcomes. Functional experiments discovered that miR-4739 dramatically enhanced tumor cell proliferation, migration, and metastasis by promoting the epithelial-to-mesenchymal transition (EMT). Meanwhile, miR-4739 can be transported from cancer cells to the site of vascular epithelial cells through exosomes, consequently facilitating the proliferation and migration of vascular epithelial cells and inducing angiogenesis. Mechanistically, miR-4739 can activate Wnt/β-catenin signaling both in tumor cells and vascular epithelial cells by targeting Wnt/β-catenin signaling antagonists APC2 and DKK3, respectively.

CONCLUSION

Our work identifies a valuable oncogene, miR-4739, that accelerates malignant progression in "driver gene-negative" NSCLC and serves as a potential therapeutic target for this group of tumors.

Methylation of ESR1 promoter induced by SNAI2-DNMT3B complex promotes epithelial-mesenchymal transition and correlates with poor prognosis in ERα-positive breast cancers

Estrogen receptor α (ERα) serves as an essential therapeutic predictor for breast cancer (BC) patients and is regulated by epigenetic modification. Abnormal methylation of cytosine phosphoric acid guanine islands in the estrogen receptor 1 (ESR1) gene promoter could silence or decrease ERα expression. In ERα-negative BC, we previously found snail family transcriptional repressor 2 (SNAI2), a zinc-finger transcriptional factor, recruited lysine-specific demethylase 1 to the promoter to transcriptionally suppress ERα expression by demethylating histone H3 lysine 4 dimethylation (H3K4me2). However, the role of SNAI2 in ERα-positive BC remains elusive. In this study, we observed a positive correlation between SNAI2 and ESR1 methylation, and SNAI2 promoted ESR1 methylation by recruiting DNA methyltransferase 3 beta (DNMT3B) rather than DNA methyltransferase 1 (DNMT1) in ERα-positive BC cells. Subsequent enrichment analysis illustrated that ESR1 methylation is strongly correlated with cell adhesion and junction. Knocking down DNMT3B could partially reverse SNAI2 overexpression-induced cell proliferation, migration, and invasion. Moreover, high DNMT3B expression predicted poor relapse-free survival and overall survival in ERα-positive BC patients. In conclusion, this study demonstrated the novel mechanisms of the ESR1 methylation mediated with the SNAI2/DNMT3B complex and enhanced awareness of ESR1 methylation's role in promoting epithelial-mesenchymal transition in BC.

Bone marrow vasculature advanced in vitro models for cancer and cardiovascular research

Cardiometabolic diseases and cancer are among the most common diseases worldwide and are a serious concern to the healthcare system. These conditions, apparently distant, share common molecular and cellular determinants, that can represent targets for preventive and therapeutic approaches. The bone marrow plays an important role in this context as it is the main source of cells involved in cardiovascular regeneration, and one of the main sites of liquid and solid tumor metastasis, both characterized by the cellular trafficking across the bone marrow vasculature. The bone marrow vasculature has been widely studied in animal models, however, it is clear the need for human-specific in vitro models, that resemble the bone vasculature lined by endothelial cells to study the molecular mechanisms governing cell trafficking. In this review, we summarized the current knowledge on in vitro models of bone marrow vasculature developed for cardiovascular and cancer research.

BCAT2 promotes melanoma progression by activating lipogenesis via the epigenetic regulation of FASN and ACLY expressions

Melanoma is the most lethal skin cancer originating from the malignant transformation of epidermal melanocyte. The dysregulation of cellular metabolism is a hallmark of cancer, including in melanoma. Aberrant branched-chain amino acids (BCAA) metabolism and related enzymes has been greatly implicated in the progression of multiple types of cancer, whereas remains far from understood in melanoma. Herein, we reported that the critical BCAA metabolism enzyme branched-chain amino acid transaminase 2 (BCAT2) is an oncogenic factor in melanoma by activating lipogenesis via the epigenetic regulation of fatty acid synthase (FASN) and ATP-citrate lyase (ACLY) expressions. Firstly, we found that BCAT2 expression was prominently increased in melanoma, and highly associated with clinical stage. Then, it was proved that the deficiency of BCAT2 led to impaired tumor cell proliferation, invasion and migration in vitro, and tumor growth and metastasis in vivo. Further, RNA sequencing technology and a panel of biochemical assays demonstrated that BCAT2 regulated de novo lipogenesis via the regulation of the expressions of both FASN and ACLY. Mechanistically, the inhibition of BCAT2 suppressed the generation of intracellular acetyl-CoA, mitigating P300-dependent histone acetylation at the promoter of FASN and ACLY, and thereby their transcription. Ultimately, zinc finger E-box binding homeobox 1 (ZEB1) was identified as the upstream transcriptional factor responsible for BCAT2 up-regulation in melanoma. Our results demonstrate that BCAT2 promotes melanoma progression by epigenetically regulating FASN and ACLY expressions via P300-dependent histone acetylation. Targeting BCAT2 could be exploited as a promising strategy to restrain tumor progression in melanoma.

Targeting drug-tolerant cells: A promising strategy for overcoming acquired drug resistance in cancer cells

Drug resistance remains the greatest challenge in improving outcomes for cancer patients who receive chemotherapy and targeted therapy. Surmounting evidence suggests that a subpopulation of cancer cells could escape intense selective drug treatment by entering a drug-tolerant state without genetic variations. These drug-tolerant cells (DTCs) are characterized with a slow proliferation rate and a reversible phenotype. They reside in the tumor region and may serve as a reservoir for resistant phenotypes. The survival of DTCs is regulated by epigenetic modifications, transcriptional regulation, mRNA translation remodeling, metabolic changes, antiapoptosis, interactions with the tumor microenvironment, and activation of signaling pathways. Thus, targeting the regulators of DTCs opens a new avenue for the treatment of therapy-resistant tumors. In this review, we first provide an overview of common characteristics of DTCs and the regulating networks in DTCs development. We also discuss the potential therapeutic opportunities to target DTCs. Last, we discuss the current challenges and prospects of the DTC-targeting approach to overcome acquired drug resistance. Reviewing the latest developments in DTC research could be essential in discovering of methods to eliminate DTCs, which may represent a novel therapeutic strategy for preventing drug resistance in the future.

The role of lncRNAs and exosomal lncRNAs in cancer metastasis

Tumor metastasis is the main reason for cancer-related death, but there is still a lack of effective therapeutic to inhibit tumor metastasis. Therefore, the discovery and study of new tumor metastasis regulators is a prominent measure for cancer diagnosis and treatment. Long non-coding RNA (lncRNA) is a type of non-coding RNAs over 200 bp in length. It has been shown that the abnormally expressed lncRNAs promote tumor metastasis by participating in the epithelial-to-mesenchymal transition (EMT) process, altering the metastatic tumor microenvironment, or changing the extracellular matrix. It is,thus, critical to explore the regulation of lncRNAs expression in cells and the molecular mechanism of lncRNA-mediated cancer metastasis. Simultaneously, it has been shown that lncRNA is one kind of the main components of exosomes, which protects lncRNAs from being rapidly degraded. Meanwhile, the components of exosomes are parent-specific, making exosomal lncRNAs to be potential tumor metastasis markers and therapeutic targets. In view of this, we also summarized the aberrant enrichment of lncRNAs in exosomes and their role in metastatic cancer. The aberrant lncRNAs and exosomal lncRNAs gradually become biomarkers and therapeutic targets for tumor metastatic, and the potential of lncRNAs in therapeutics are studied here. Besides, the lncRNA-related databases, which could greatly facilitate in the study of lncRNAs and exosomal lncRNAs in metastatic of cancer are included in this review.

Circular RNA hsa_circ_0098181 inhibits metastasis in hepatocellular carcinoma by activating the Hippo signaling pathway via interaction with eEF2

INTRODUCTION AND OBJECTIVES

The development of hepatocellular carcinoma (HCC) is a multi-step process that accumulates genetic and epigenetic alterations, including changes in circular RNA (circRNA). This study aimed to understand the alterations in circRNA expression in HCC development and metastasis and to explore the biological functions of circRNA.

MATERIALS AND METHODS

Ten pairs of adjacent chronic hepatitis tissues and HCC tissues from patients without venous metastases, and ten HCC tissues from patients with venous metastases were analyzed using human circRNA microarrays. Differentially expressed circRNAs were then validated by quantitative real-time PCR. In vitro and in vivo assays were performed to assess the roles of the circRNA in HCC progression. RNA pull-down assay, mass spectrometry analysis, and RNA-binding protein immunoprecipitation were conducted to explore the protein partners of the circRNA.

RESULTS

CircRNA microarrays revealed that the expression patterns of circRNAs across the three groups were significantly different. Among these, hsa_circ_0098181 was validated to be lowly expressed and associated with poor prognosis in HCC patients. Ectopic expression of hsa_circ_0098181 delayed HCC metastasis in vitro and in vivo. Mechanistically, hsa_circ_0098181 sequestered eukaryotic translation elongation factor 2 (eEF2) and dissociated eEF2 from filamentous actin (F-actin) to prevent F-actin formation, which blocked activation of the Hippo signaling pathway. In addition, the RNA binding protein Quaking-5 bound directly to hsa_circ_0098181 and induced its biogenesis.

CONCLUSIONS

Our study reveals changes in circRNA expression from chronic hepatitis, primary HCC, to metastatic HCC. Further, the QKI5-hsa_circ_0098181-eEF2-Hippo signaling pathway exerts a regulatory role in HCC.

Biological function and research progress of N6-methyladenosine binding protein heterogeneous nuclear ribonucleoprotein A2B1 in human cancers

N6-methyladenosine (m6A) is the most prevalent internal modification found in both mRNA and lncRNA. It exerts reversible regulation over RNA function and affects RNA processing and metabolism in various diseases, especially tumors. The m6A binding protein, hnRNPA2B1, is extensively studied as a member of the heterogeneous nuclear ribonucleoprotein (hnRNP) protein family. It is frequently dysregulated and holds significant importance in multiple types of tumors. By recognizing m6A sites for variable splicing, maintaining RNA stability, and regulating translation and transport, hnRNPA2B1 plays a vital role in various aspects of tumor development, metabolism, and regulation of the immune microenvironment. In this review, we summarized the latest research on the functional roles and underlying molecular mechanisms of hnRNPA2B1. Moreover, we discussed its potential as a target for tumor therapy.

The ubiquitin-proteasome system in breast cancer

Ubiquitin-proteasome system (UPS) is a selective proteolytic system that is associated with the expression or function of target proteins and participates in various physiological and pathological processes of breast cancer. Inhibitors targeting the 26S proteasome in combination with other drugs have shown promising therapeutic effects in the clinical treatment of breast cancer. Moreover, several inhibitors/stimulators targeting other UPS components are also effective in preclinical studies, but have not yet been applied in the clinical treatment of breast cancer. Therefore, it is vital to comprehensively understand the functions of ubiquitination in breast cancer and to identify potential tumor promoters or tumor suppressors among UPS family members, with the aim of developing more effective and specific inhibitors/stimulators targeting specific components of this system.

CRISPR-Cas9 screen reveals a role of purine synthesis for estrogen receptor α activity and tamoxifen resistance of breast cancer cells

In breast cancer, resistance to endocrine therapies that target estrogen receptor α (ERα), such as tamoxifen and fulvestrant, remains a major clinical problem. Whether and how ERα⁺ breast cancers switch from being estrogen-dependent to estrogen-independent remains unclear. With a genome-wide CRISPR-Cas9 knockout screen, we identified previously unknown biomarkers and potential therapeutic targets of endocrine resistance. We demonstrate that high levels of PAICS, an enzyme involved in the de novo biosynthesis of purines, can shift the balance of ERα activity to be more estrogen-independent and tamoxifen-resistant. We find that this may be due to elevated activities of cAMP-activated protein kinase A and mTOR, kinases known to phosphorylate ERα specifically and to stimulate its activity. Genetic or pharmacological targeting of PAICS sensitizes tamoxifen-resistant cells to tamoxifen. Addition of purines renders them more resistant. On the basis of these findings, we propose the combined targeting of PAICS and ERα as a new, effective, and potentially safe therapeutic regimen.

Network-informed discovery of multidrug combinations for ERα+/HER2-/PI3Kα-mutant breast cancer

Breast cancer is a persistent threat to women worldwide. A large proportion of breast cancers are dependent on the estrogen receptor α (ERα) for tumor progression. Therefore, targeting ERα with antagonists, such as tamoxifen, or estrogen deprivation by aromatase inhibitors remain standard therapies for ERα + breast cancer. The clinical benefits of monotherapy are often counterbalanced by off-target toxicity and development of resistance. Combinations of more than two drugs might be of great therapeutic value to prevent resistance, and to reduce doses, and hence, decrease toxicity. We mined data from the literature and public repositories to construct a network of potential drug targets for synergistic multidrug combinations. With 9 drugs, we performed a phenotypic combinatorial screen with ERα + breast cancer cell lines. We identified two optimized low-dose combinations of 3 and 4 drugs of high therapeutic relevance to the frequent ERα + /HER2-/PI3Kα-mutant subtype of breast cancer. The 3-drug combination targets ERα in combination with PI3Kα and cyclin-dependent kinase inhibitor 1 (p21). In addition, the 4-drug combination contains an inhibitor for poly (ADP-ribose) polymerase 1 (PARP1), which showed benefits in long-term treatments. Moreover, we validated the efficacy of the combinations in tamoxifen-resistant cell lines, patient-derived organoids, and xenograft experiments. Thus, we propose multidrug combinations that have the potential to overcome the standard issues of current monotherapies.

Molecular aspects of brain metastases in breast cancer

Brain metastases (BM) are a common and devastating manifestation of breast cancer (BC). BM are particularly frequent in the HER2-positive and triple-negative breast cancer phenotypes and usually occur following the metastatic spread to extracranial sites. Several genes mediating BM and biomarkers predicting their risk in BC have been reported in the past decade. These findings have advanced the understanding of BM pathobiology and paved the way for developing new therapeutic strategies but they still warrant a thorough clinical validation. Hence, a better understanding of the mechanistic aspects of BM and delineating the interactions of tumor cells with the brain microenvironment are of utmost importance. This review discusses the molecular basis of the metastatic cascade: the epithelial-mesenchymal transition, cancer, and tumor microenvironment interaction and intravasation, priming of the metastatic niche in the brain, and survival in the new site. We also outline the postulated mechanisms of BC cells' brain tropism. Finally, we discuss advances in the field of biomarkers (both tissue-based and liquid-based) that predict BM from BC.

Quiescent Cancer Cells-A Potential Therapeutic Target to Overcome Tumor Resistance and Relapse

Quiescent cancer cells (QCCs) are nonproliferating cells arrested in the G0 phase, characterized by ki67^low and p27^high. QCCs avoid most chemotherapies, and some treatments could further lead to a higher proportion of QCCs in tumors. QCCs are also associated with cancer recurrence since they can re-enter a proliferative state when conditions are favorable. As QCCs lead to drug resistance and tumor recurrence, there is a great need to understand the characteristics of QCCs, decipher the mechanisms that regulate the proliferative-quiescent transition in cancer cells, and develop new strategies to eliminate QCCs residing in solid tumors. In this review, we discussed the mechanisms of QCC-induced drug resistance and tumor recurrence. We also discussed therapeutic strategies to overcome resistance and relapse by targeting QCCs, including (i) identifying reactive quiescent cancer cells and removing them via cell-cycle-dependent anticancer reagents; (ii) modulating the quiescence-to-proliferation switch; and (iii) eliminating QCCs by targeting their unique features. It is believed that the simultaneous co-targeting of proliferating and quiescent cancer cells may ultimately lead to the development of more effective therapeutic strategies for the treatment of solid tumors.

Biology, vulnerabilities and clinical applications of circulating tumour cells

In recent years, exceptional technological advances have enabled the identification and interrogation of rare circulating tumour cells (CTCs) from blood samples of patients, leading to new fields of research and fostering the promise for paradigm-changing, liquid biopsy-based clinical applications. Analysis of CTCs has revealed distinct biological phenotypes, including the presence of CTC clusters and the interaction between CTCs and immune or stromal cells, impacting metastasis formation and providing new insights into cancer vulnerabilities. Here we review the progress made in understanding biological features of CTCs and provide insight into exploiting these developments to design future clinical tools for improving the diagnosis and treatment of cancer.

LOXL1 and LOXL4 are novel target genes of the Zn2+-bound form of ZEB1 and play a crucial role in the acceleration of invasive events in triple-negative breast cancer cells

Background

EMT has been proposed to be a crucial early event in cancer metastasis. EMT is rigidly regulated by the action of several EMT-core transcription factors, particularly ZEB1. We previously revealed an unusual role of ZEB1 in the S100A8/A9-mediated metastasis in breast cancer cells that expressed ZEB1 at a significant level and showed that the ZEB1 was activated on the MCAM-downstream pathway upon S100A8/A9 binding. ZEB1 is well known to require Zn²⁺ for its activation based on the presence of several Zn-finger motifs in the transcription factor. However, how Zn²⁺-binding works on the pleiotropic role of ZEB1 through cancer progression has not been fully elucidated.

Methods

We established the engineered cells, MDA-MB-231 MutZEB1 (MDA-MutZEB1), that stably express MutZEB1 (ΔZn). The cells were then evaluated in vitro for their invasion activities. Finally, an RNA-Seq analysis was performed to compare the gene alteration profiles of the established cells comprehensively.

Results

MDA-MutZEB1 showed a significant loss of the EMT, ultimately stalling the invasion. Inclusive analysis of the transcription changes after the expression of MutZEB1 (ΔZn) in MDA-MB-231 cells revealed the significant downregulation of LOX family genes, which are known to play a critical role in cancer metastasis. We found that LOXL1 and LOXL4 remarkably enhanced cancer invasiveness among the LOX family genes with altered expression.

Conclusions

These findings indicate that ZEB1 potentiates Zn²⁺-mediated transcription of plural EMT-relevant factors, including LOXL1 and LOXL4, whose upregulation plays a critical role in the invasive dissemination of breast cancer cells.

Lysyl oxidase-like 4 exerts an atypical role in breast cancer progression that is dependent on the enzymatic activity that targets the cell-surface annexin A2

Background

LOX family members are reported to play pivotal roles in cancer. Unlike their enzymatic activities in collagen cross-linking, their precise cancer functions are unclear. We revealed that LOXL4 is highly upregulated in breast cancer cells, and we thus sought to define an unidentified role of LOXL4 in breast cancer.

Methods

We established the MDA-MB-231 sublines MDA-MB-231-LOXL4 mutCA and -LOXL4 KO, which stably overexpress mutant LOXL4 that loses its catalytic activity and genetically ablates the intrinsic LOXL4 gene, respectively. In vitro and in vivo evaluations of these cells' activities of cancer outgrowth were conducted by cell-based assays in cultures and an orthotopic xenograft model, respectively. The new target (s) of LOXL4 were explored by the MS/MS analytic approach.

Results

Our in vitro results revealed that both the overexpression of mutCA and the KO of LOXL4 in cells resulted in a marked reduction of cell growth and invasion. Interestingly, the lowered cellular activities observed in the engineered cells were also reflected in the mouse model. We identified a novel binding partner of LOXL4, i.e., annexin A2. LOXL4 catalyzes cell surface annexin A2 to achieve a cross-linked multimerization of annexin A2, which in turn prevents the internalization of integrin β-1, resulting in the locking of integrin β-1 on the cell surface. These events enhance the promotion of cancer cell outgrowth.

Conclusions

LOXL4 has a new role in breast cancer progression that occurs via an interaction with annexin A2 and integrin β-1 on the cell surface.

Embryonic Programs in Cancer and Metastasis—Insights From the Mammary Gland

Cancer is characterized as a reversion of a differentiated cell to a primitive cell state that recapitulates, in many aspects, features of embryonic cells. This review explores the current knowledge of developmental mechanisms that are essential for embryonic mouse mammary gland development, with a particular focus on genes and signaling pathway components that are essential for the induction, morphogenesis, and lineage specification of the mammary gland. The roles of these same genes and signaling pathways in mammary gland or breast tumorigenesis and metastasis are then summarized. Strikingly, key embryonic developmental pathways are often reactivated or dysregulated during tumorigenesis and metastasis in processes such as aberrant proliferation, epithelial-to-mesenchymal transition (EMT), and stem cell potency which affects cellular lineage hierarchy. These observations are in line with findings from recent studies using lineage tracing as well as bulk- and single-cell transcriptomics that have uncovered features of embryonic cells in cancer and metastasis through the identification of cell types, cell states and characterisation of their dynamic changes. Given the many overlapping features and similarities of the molecular signatures of normal development and cancer, embryonic molecular signatures could be useful prognostic markers for cancer. In this way, the study of embryonic development will continue to complement the understanding of the mechanisms of cancer and aid in the discovery of novel therapeutic targets and strategies.