The role of EMT-related lncRNA in the process of triple-negative breast cancer metastasis

Triple-negative breast cancer (TNBC) is the most malignant and fatal subtype of breast cancer, which has characterized by negativity expression of ER, PR, and HER2. Metastasis is the main factor affecting the prognosis of TNBC, and the process of metastasis is related to abnormal activation of epithelial–mesenchymal transition (EMT). Recent studies have shown that long non-coding RNA (LncRNA) plays an important role in regulating the metastasis and invasion of TNBC. Therefore, based on the metastasis-related EMT signaling pathway, great efforts have confirmed that LncRNA is involved in the molecular mechanism of TNBC metastasis, which will provide new strategies to improve the treatment and prognosis of TNBC. In this review, we summarized many signal pathways related to EMT involved in the transfer process. The advances from the most recent studies of lncRNAs in the EMT-related signal pathways of TNBC metastasis. We also discussed the clinical research, application, and challenges of LncRNA in TNBC.     

SENP1 promotes triple-negative breast cancer invasion and metastasis via enhancing CSN5 transcription mediated by GATA1 deSUMOylation

TNBC is characterized by high incidence of visceral metastasis and lacks effective clinical targets. This study aims to delineate the molecular mechanisms of SENP1 in TNBC invasion and metastasis. By using IHC to test the SENP1 expression in TNBC tissues, we analyzed the relationship between SENP1 expression and TNBC prognosis. We showed that SENP1 expression was higher in TNBC tumor tissues and related to TNBC prognosis, supporting SENP1 as an independent risk factor. High expression of SENP1 was significantly associated with histologic grade and tumor lymph node invasion. Intriguingly, the expression levels of SENP1 in TNBC tumors were significantly correlated with that of CSN5, GATA1 and ZEB1. Importantly, SENP1 promoted TNBC cell migration and invasion by regulating ZEB1 deubiquitination and expression through CSN5. Further studies showed that deSUMOylation at lysine residue K137 of GATA1 enhanced the binding of GATA1 to the CSN5 promoter and transactivated CSN5 expression. In addition, we showed that ZEB1 is deubiquitinated at lysine residue K1108. Our in vivo studies also indicated that reduction in SENP1 expression upregulated GATA1 SUMOylation, and thus resulted in decreased expression of CSN5 and ZEB1 in the tumor microenvironment, which decelerated TNBC progression and metastasis. SENP1 promoted CSN5-mediated ZEB1 protein degradation via deSUMOylation of GATA1, and thus influenced TNBC progression. These findings suggest that SENP1 could be utilized as a potential target for blockade of TNBC development and thus provide a totally new approach for TNBC treatment.     

CHFR regulates chemoresistance in triple-negative breast cancer through destabilizing ZEB1

Failures to treat triple-negative breast cancer (TNBC) are mainly due to chemoresistance or radioresistance. We and others previously discovered that zinc finger E-box-binding homeobox 1 (ZEB1) is a massive driver causing these resistance. However, how to dynamically modulate the intrinsic expression of ZEB1 during cell cycle progression is elusive. Here integrated affinity purification combined with mass spectrometry and TCGA analysis identify a cell cycle-related E3 ubiquitin ligase, checkpoint with forkhead and ring finger domains (CHFR), as a key negative regulator of ZEB1 in TNBC. Functional studies reveal that CHFR associates with and decreases ZEB1 expression in a ubiquitinating-dependent manner and that CHFR represses fatty acid synthase (FASN) expression through ZEB1, leading to significant cell death of TNBC under chemotherapy. Intriguingly, a small-molecule inhibitor of HDAC under clinical trial, Trichostatin A (TSA), increases the expression of CHFR independent of histone acetylation, thereby destabilizes ZEB1 and sensitizes the resistant TNBC cells to conventional chemotherapy. In patients with basal-like breast cancers, CHFR levels significantly correlates with survival. These findings suggest the therapeutic potential for targeting CHFR-ZEB1 signaling in resistant malignant breast cancers.Subject terms: Cancer therapy, Cell death, Post-translational modifications     

Angiogenesis and Antiangiogenesis in Triple-Negative Breast cancer

Several data support a central role for angiogenesis in breast cancer growth and metastasis. Observational studies have demonstrated that microvascular density (MVD) is a prognostic factor in invasive breast cancer, whereas others reached the opposite conclusion. Vascular endothelial growth factor is the most important angiogenic factor with proven significance in breast cancer, as it has been assessed in both experimental and clinical studies. Triple-negative breast cancer (TNBC) is a type of breast cancer which lacks estrogen, progesterone, and HER-2/neu receptors. MVD in both basal-like and TNBC is significantly higher than in non–basal-like and non-TNBC. In breast cancer and other malignancies, the development of agents that inhibit tumor angiogenesis has been an active area of investigation. In TNBC, clinical trials combining targeted agents and chemotherapy have failed to show substantial survival improvement. There is evidence that patients with TNBC may have a greater probability of obtaining some kind of clinical efficacy benefit from bevacizumab-based therapy.     

Triple-negative breast cancer cells rely on kinase-independent functions of CDK8 to evade NK-cell-mediated tumor surveillance

Triple-negative breast cancer (TNBC) is an aggressive malignant disease that is responsible for approximately 15% of breast cancers. The standard of care relies on surgery and chemotherapy but the prognosis is poor and there is an urgent need for new therapeutic strategies. Recent in silico studies have revealed an inverse correlation between recurrence-free survival and the level of cyclin-dependent kinase 8 (CDK8) in breast cancer patients. CDK8 is known to have a role in natural killer (NK) cell cytotoxicity, but its function in TNBC progression and immune cell recognition or escape has not been investigated. We have used a murine model of orthotopic breast cancer to study the tumor-intrinsic role of CDK8 in TNBC. Knockdown of CDK8 in TNBC cells impairs tumor regrowth upon surgical removal and prevents metastasis. In the absence of CDK8, the epithelial-to-mesenchymal transition (EMT) is impaired and immune-mediated tumor-cell clearance is facilitated. CDK8 drives EMT in TNBC cells in a kinase-independent manner. In vivo experiments have confirmed that CDK8 is a crucial regulator of NK-cell-mediated immune evasion in TNBC. The studies also show that CDK8 is involved in regulating the checkpoint inhibitor programmed death-ligand 1 (PD-L1). The CDK8–PD-L1 axis is found in mouse and human TNBC cells, underlining the importance of CDK8-driven immune cell evasion in these highly aggressive breast cancer cells. Our data link CDK8 to PD-L1 expression and provide a rationale for investigating the possibility of CDK8-directed therapy for TNBC.Subject terms: Breast cancer, Immune evasion     

Steroid Receptor Coactivator-3 (SRC-3/AIB1) as a Novel Therapeutic Target in Triple Negative Breast Cancer and Its Inhibition with a Phospho-Bufalin Prodrug

Triple negative breast cancer (TNBC) has the poorest prognosis of all types of breast cancer and currently lacks efficient targeted therapy. Chemotherapy is the traditional standard-of-care for TNBC, but is frequently accompanied by severe side effects. Despite the fact that high expression of steroid receptor coactivator 3 (SRC–3) is correlated with poor survival in estrogen receptor positive breast cancer patients, its role in TNBC has not been extensively investigated. Here, we show that high expression of SRC–3 correlates with both poor overall survival and post progression survival in TNBC patients, suggesting that SRC–3 can serve as a prognostic marker for TNBC. Furthermore, we demonstrated that bufalin, a SRC–3 small molecule inhibitor, when introduced even at nM concentrations, can significantly reduce TNBC cell viability and motility. However, because bufalin has minimal water solubility, its in vivo application is limited. Therefore, we developed a water soluble prodrug, 3-phospho-bufalin, to facilitate its in vivo administration. In addition, we demonstrated that 3-phospho-bufalin can effectively inhibit tumor growth in an orthotopic TNBC mouse model, suggesting its potential application as a targeted therapy for TNBC treatment.     

Histone deacetylase 2 knockout suppresses immune escape of triple-negative breast cancer cells via downregulating PD-L1 expression

The PD-L1 overexpression is an important event of immune escape and metastasis in triple-negative breast cancer (TNBC), but the molecular mechanism remains to be determined. Interferon gamma (IFNγ) represents a major driving force behind PD-L1 expression in tumor microenvironment, and histone deacetylase 2 (HDAC2) is required for IFN signaling. Here, we investigated the regulation of HDAC2 on the IFNγ-induced PD-L1 expression in TNBC cells. We found the HDAC2 and PD-L1 expression in TNBC was significantly higher than that in non-TNBC, and HDAC2 was positively correlated with PD-L1 expression. HDAC2 promoted PD-L1 induction by upregulating the phosphorylation of JAK1, JAK2, and STAT1, as well as the translocation of STAT1 to the nucleus and the recruitment of STAT1 to the PD-L1 promoter. Meanwhile, HDAC2 was recruited to the PD-L1 promoter by STAT1, and HDAC2 knockout compromised IFNγ-induced upregulation of H3K27, H3K9 acetylation, and the BRD4 recruitment in PD-L1 promoter. In addition, significant inhibition of proliferation, colony formation, migration, and cell cycle of TNBC cells were observed following knockout of HDAC2 in vitro. Furthermore, HDAC2 knockout reduced IFNγ-induced PD-L1 expression, lymphocyte infiltration, and retarded tumor growth and metastasis in the breast cancer mouse models. This study may provide evidence that HDAC2 promotes IFNγ-induced PD-L1 expression, suggesting a way for enhanced antitumor immunity when targeting the HDAC2 in TNBC.Subject terms: Breast cancer, Immune evasion     

The potential role of cofilin-1 in promoting triple negative breast cancer (TNBC) metastasis via the extracellular vesicles (EVs)

Triple negative breast cancer (TNBC) is an aggressive cancer, particularly prone to metastasis and is associated with poor survival outcomes. The key to unravelling the aggressiveness of TNBC lies in decoding the mechanism by which it metastasises. Cofilin-1 is a well-studied member of the cofilin family, involved in actin depolymerisation. Studies have described the diverse roles of cofilin-1 including cell motility, apoptosis and lipid metabolism. Levels of cofilin-1 have been shown to be increased in many different types of malignant cells, with increased cofilin-1 protein levels associated with poor prognosis in patients with TNBC. Extracellular vesicles (EVs) are microvesicles typically around 100 nm in size, found in all biological fluids examined to date (Lötvall et al., 2014). Proteomic studies on extracellular vesicles (EVs) have shown that cofilin-1 is amongst the most frequently detected. Moreover, decreased levels of cofilin-1 potentially inhibit the release of EVs from cells. Additionally, Cofilin-1 is essential for the maturation of EVs and may also play a key role in the establishment of the pre-metastatic niche, thus promoting tumour cell migration. Further work into the exact mechanism by which cofilin-1 advances TNBC metastasis, may potentially prevent disease progression and improve outcomes for patients with TNBC.     

Inhibiting β-catenin disables nucleolar functions in triple-negative breast cancer

Triple-negative breast cancer (TNBC) patients with upregulated Wnt/β-catenin signaling often have poor clinical prognoses. During pathological examinations of breast cancer sections stained for β-catenin, we made the serendipitous observation that relative to non-TNBC, specimens from TNBC patients have a greater abundance of nucleoli. There was a remarkable direct relationship between nuclear β-catenin and greater numbers of nucleoli in TNBC tissues. These surprising observations spurred our investigations to decipher the differential functional relevance of the nucleolus in TNBC versus non-TNBC cells. Comparative nucleolar proteomics revealed that the majority of the nucleolar proteins in TNBC cells were potential targets of β-catenin signaling. Next, we undertook an analysis of the nucleolar proteome in TNBC cells in response to β-catenin inhibition. This effort revealed that a vital component of pre-rRNA processing, LAS1 like ribosome biogenesis factor (LAS1L) was significantly decreased in the nucleoli of β-catenin inhibited TNBC cells. Here we demonstrate that LAS1L protein expression is significantly elevated in TNBC patients, and it functionally is important for mammary tumor growth in xenograft models and enables invasive attributes. Our observations highlight a novel function for β-catenin in orchestrating nucleolar activity in TNBCs.Subject terms: Breast cancer, Organelles, Breast cancer, Metastasis     

Mitochondrial Protein UCP1 Inhibits the Malignant Behaviors of Triple-negative Breast Cancer through Activation of Mitophagy and Pyroptosis

Triple-negative breast cancer (TNBC) is a massive threat to women''s health due to its high morbidity, malignancy, and the refractory, effective therapeutic option of TNBC is still deficient. The mitochondrial protein showed therapeutic potential on breast cancer, whereas the mechanism and downstream pathway of mitochondrial uncoupling protein 1 (UCP1) was not fully elucidated. We found that UCP1 was negatively regulated to the process of TNBC. Overexpressing UCP1 could inhibit the proliferation and metastasis of TNBC, meanwhile inducing the mitochondrial swelling and activation of mitophagy in vitro. Mitophagy activation was then assessed to elucidate whether it was downstream of UCP1 in TNBC metastasis. GSDME is the core of pyroptosis. We found that GSDME was activated in the TNBC cells when UCP1 levels were high. It regulates TNBC cell proliferation potential instead of the apoptosis process in vitro and in vivo. Our results suggested that UCP1 could inhibit the process of TNBC by activating mitophagy and pyroptosis. Impaired activation of mitophagy weakens the regulation effect of UCP1 on metastasis of TNBC, similar to the impairment of GSDME activation on the proliferation regulation of UCP1 on TNBC. UCP1 might be a novel therapeutic target of TNBC.     

High Levels of Nucleolar Spindle-Associated Protein and Reduced Levels of BRCA1 Expression Predict Poor Prognosis in Triple-Negative Breast Cancer

Purpose

Nucleolar spindle-associated protein (NuSAP1) is an important mitosis-related protein, and aberrant NuSAP1 expression is associated with abnormal spindles and mitosis. This study investigated the prognostic value of NuSAP1 in breast cancer.

Methods

Two sets of tissue microarrays (TMAs) that included samples from 450 breast cancer patients were constructed, of which 250 patients were training set and the other 200 patients were validation set. Immunohistochemical staining was performed to determine the NuSAP1 levels. A Kaplan-Meier analysis was used to estimate the prognostic value of NuSAP1 in breast cancer. A stepwise Cox analysis was performed to construct a risk-prediction model for triple-negative breast cancer (TNBC). All statistical analysis was performed with SPSS software.

Results

There were 108 (43.5%) and 88 (44.0%) patients expressed NuSAP1 in the training set and validation set respectively. High levels of NuSAP1 expression were related to poor disease-free survival (DFS) in both training (P = 0.028) and validation (P = 0.006) cohorts, particularly in TNBC. With combination of two cohorts, both NuSAP1 (HR = 4.136, 95% CI: 1.956–8.747, P < 0.001) and BRCA1 (HR = 0.383, 95% CI: 0.160–0.915, P = 0.031) were independent prognostic indicators of DFS in TNBC. A receiver operating characteristic (ROC) analysis revealed that the combination of NuSAP1 and BRCA1 significantly improved the prognostic power compared with the traditional model (0.778 versus 0.612, P < 0.001).

Conclusions

Our study confirms the prognostic value of NuSAP1 in breast cancer. The combination of NuSAP1 and BRCA1 could improve the DFS prediction accuracy in TNBC.     

Tumor-derived exosomal circPSMA1 facilitates the tumorigenesis,metastasis, and migration in triple-negative breast cancer (TNBC) through miR-637/Akt1/β-catenin (cyclin D1) axis

Circular RNAs (circRNAs) are increasingly gaining importance and attention due to their diverse potential functions and their value as diagnostic biomarkers (disease specific). This study aims to explore the novel mechanisms by which exosome-contained circRNAs promote tumor development and metastasis in TNBC. We identified increased circRNA circPSMA1 in TNBC cells, their exosomes, and serum exosomes samples from TNBC patients. The overexpression of circPSMA1 promoted TNBC cell proliferation, migration, and metastasis both in vitro and in vivo. Moreover, we investigated the tumor-infiltrating immune cells (TICs) or stromal components in immune microenvironment (IME), and identified the significant differences in the immune cells between TNBC and non-TNBC samples. Mechanistically, circPSMA1 acted as a “miRNAs sponge” to absorb miR-637; miR-637 inhibited TNBC cell migration and metastasis by directly targeted Akt1, which recognized as a key immune-related gene and affected downstream genes β-catenin and cyclin D1. Subsequent co-culture experiments also demonstrated that exosomes from TNBC carrying large amounts of circPSMA1 could transmit migration and proliferation capacity to recipient cells. Kaplan–Meier plots showed that high expression of Akt1 and low expression of mir-637 are highly correlated with poor prognosis in patients with lymph node metastasis of TNBC. Collectively, all these results reveal that circPSMA1 functions as a tumor promoter through the circPSMA1/miR-637/Akt1-β-catenin (cyclin D1) regulatory axis, which can facilitate the tumorigenesis, metastasis, and immunosuppression of TNBC. Our research proposes a fresh perspective on novel potential biomarkers and immune treatment strategies for TNBC.Subject terms: Breast cancer, Cancer microenvironment     

HIF-1α Promotes Epithelial-Mesenchymal Transition and Metastasis through Direct Regulation of ZEB1 in Colorectal Cancer

It is well recognized that hypoxia-inducible factor 1 alpha (HIF-1α) is involved in cancer metastasis, chemotherapy and poor prognosis. We previously found that deferoxamine, a hypoxia-mimetic agent, induces epithelial-mesenchymal transition (EMT) in colorectal cancer. Therefore, here we explored a new molecular mechanism for HIF-1α contributing to EMT and cancer metastasis through binding to ZEB1. In this study, we showed that overexpression of HIF-1α with adenovirus infection promoted EMT, cell invasion and migration in vitro and in vivo. On a molecular level, HIF-1α directly binding to the proximal promoter of ZEB1 via hypoxia response element (HRE) sites thus increasing the transactivity and expression of ZEB1. In addition, inhibition of ZEB1 was able to abrogate the HIF-1α-induced EMT and cell invasion. HIF-1α expression was highly correlated with the expression of ZEB1 in normal colorectal epithelium, primary and metastatic CRC tissues. Interestingly, both HIF-1α and ZEB1 were positively associated with Vimentin, an important mesenchymal marker of EMT, whereas negatively associated with E-cadherin expression. These findings suggest that HIF-1α enhances EMT and cancer metastasis by binding to ZEB1 promoter in CRC. HIF-1α and ZEB1 are both widely considered as tumor-initiating factors, but our results demonstrate that ZEB1 is a direct downstream of HIF-1α, suggesting a novel molecular mechanism for HIF-1α-inducing EMT and cancer metastasis.