Effects of Cancer Stem Cells in Triple-Negative Breast Cancer and Brain Metastasis: Challenges and Solutions

GLS and GOT2 as prognostic biomarkers associated with dendritic cell and immunotherapy response in breast cancer

Breast cancer is the females' most common cancer. Targeting the immune microenvironment is a new and promising treatment method for breast cancer. Nevertheless, only a small section of patients can profit by immunotherapy, and improving the ability to accurately predict the potential for immunotherapy response is still awaiting further exploration. In this study, we found that the key factors of glutamine metabolism, glutaminase 1 (GLS) and mitochondrial aspartate transaminase (GOT2), showed opposite expression patterns in breast cancer samples. Based on the expression level of GLS and GOT2, we divided the breast cancer samples into two clusters: Cluster 2 showed GLS expressed higher and GOT2 expressed lower, whereas Cluster 1 showed GOT2 expressed higher and GLS expressed lower. GSEA showed that the clusters were related to pathways of immunity. Further analysis showed that Cluster 2 was positively associated with immunity infiltration. Through WGCNA, we identified a module strongly correlated with glutamine metabolism and immunity and identified 11 dendritic cell-associated genes involved in dendritic cell development, maturation, activation and other functions. In addition, Cluster 2 also showed higher immune checkpoint gene expression, which suggest the Cluster 2 had even better response to immunotherapy. The validation dataset could also be clustered into two groups. Cluster 2 (GLS expressed higher and GOT2 expressed lower) of the validation dataset was also positively associated with dendritic cells and a better immunotherapy response. Thus, these data indicate that GLS and GOT2 are prognostic biomarkers which closely related to dendritic cells and better reacted to immunotherapy in breast cancer.

N-3, a novel synthetic derivative of bifendate, inhibits metastasis of triple-negative breast cancer via decreasing p38-regulated FOXC1 protein stability

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype with high invasiveness, metastatic potential, and poor prognosis. Epithelial-mesenchymal transition (EMT) is pivotal in TNBC progression, becoming a promising target for TNBC treatment. Our study evaluated N-3, a novel synthetic bifendate derivative, which inhibited the EMT-associated migration and invasion of MDA-MB-231 and 4T1 TNBC cells. The results were consistent with the suppression of FOXC1 expression and transcriptional activity. Additional studies indicated that N-3 reduced the protein stability of FOXC1 by enhancing ubiquitination and degradation. Moreover, N-3 downregulated p-p38 expression and FOXC1 interaction, decreasing the stability of p38-regulated FOXC1. Further, N-3 blocked TNBC metastasis with an artificial lung metastasis model in vivo, related to FOXC1 suppression and EMT. These results highlight the potential of N-3 as a TNBC metastasis treatment. Therefore, FOXC1 regulation could be a novel targeted therapeutic strategy for TNBC metastasis.

Artificial intelligence: opportunities and challenges in the clinical applications of triple-negative breast cancer

Triple-negative breast cancer (TNBC) accounts for 15-20% of all invasive breast cancer subtypes. Owing to its clinical characteristics, such as the lack of effective therapeutic targets, high invasiveness, and high recurrence rate, TNBC is difficult to treat and has a poor prognosis. Currently, with the accumulation of large amounts of medical data and the development of computing technology, artificial intelligence (AI), particularly machine learning, has been applied to various aspects of TNBC research, including early screening, diagnosis, identification of molecular subtypes, personalised treatment, and prediction of prognosis and treatment response. In this review, we discussed the general principles of artificial intelligence, summarised its main applications in the diagnosis and treatment of TNBC, and provided new ideas and theoretical basis for the clinical diagnosis and treatment of TNBC.

Molecular landscape and emerging therapeutic strategies in breast cancer brain metastasis

Breast cancer (BC) is the most commonly diagnosed cancer worldwide. Advanced BC with brain metastasis (BM) is a major cause of mortality with no specific or effective treatment. Therefore, better knowledge of the cellular and molecular mechanisms underlying breast cancer brain metastasis (BCBM) is crucial for developing novel therapeutic strategies and improving clinical outcomes. In this review, we focused on the latest advances and discuss the contribution of the molecular subtype of BC, the brain microenvironment, exosomes, miRNAs/lncRNAs, and genetic background in BCBM. The blood–brain barrier and blood–tumor barrier create challenges to brain drug delivery, and we specifically review novel approaches to bypass these barriers. Furthermore, we discuss the potential application of immunotherapies and genetic editing techniques based on CRISPR/Cas9 technology in treating BCBM. Emerging techniques and research findings continuously shape our views of BCBM and contribute to improvements in precision therapies and clinical outcomes.

High percentage of Cancer Stem cells in metastatic locations: Upregulation of cicBIRC6 in highly metastatic breast Cancer Subline

BACKGROUND

Metastasis is a devastating complication of breast cancer. Cancer relapse and metastasis are associated with cancer stem cells. CicBIRC6 is a circular RNA that is proposed to be involved in the stemness of stem cells. In breast cancer, metastatic tumor cells have higher stem cell properties. In the present study, we evaluate the expression of cicBIRC6 in these cells.

METHODS

After the development of a syngeneic animal model of TNBC, primary breast cancer cells named 4T1T were isolated from the tumor mass. Highly metastatic tumor cells named 4T1B and 4T1L were isolated and expanded from brain metastasis lesions and lungs of cancerous mice respectively. Sphere formation ability in metastatic and primary tumor cells was evaluated separately. The quantitative real-time polymerase chain reaction was performed to analyze the expression of cicBIRC6 in primary and metastatic tumor cells.

RESULTS

Our data revealed that, sphere formation ability among metastatic tumor cells was significantly higher. Surprisingly expression of cicBIRC6 was significantly upregulated in these metastatic tumor cells. In comparison with 4T1T, cicBIRC6 was upregulated 5.7 and 3.5 times in 4T1B and 4T1L respectively.

CONCLUSION

These findings provided important insights regarding the molecular properties of metastatic tumor cells and can be used for designing a targeted therapeutic strategy in combat with these cells.

Tumor Suppressive Role of MicroRNAs in Triple Negative Breast Cancer

Triple-negative breast cancers are highly aggressive, a heterogeneous form of breast cancer with a high re-occurrence rate that further lacks an efficient treatment strategy and prognostic marker. The tumor microenvironment of the disease comprises cancer-associated fibroblasts, cancer stem cells, immunological molecules, epithelial-mesenchymal transition, and a metastatic microenvironment that contributes to disease progression and metastasis to distant sites. Emerging evidence indicated that miRNA clusters would be of clinical utility as they exert an oncogenic or tumor suppressor role in TNBC. The present review article aims to highlight the therapeutic significance of miRNA in targeting the above-mentioned signaling cascades and modulating the intracellular crosstalk in the tumor microenvironment of TNBC. Prognostic implications of miRNAs to depict disease-free survival, distant metastasis-free survival, relapse-free survival, and overall survival outcome were also unveiled.

N-Heterocycle based Degraders (PROTACs) Manifesting Anticancer Efficacy: Recent Advances

Proteolysis Targeting Chimeras (PROTACs) technology has emerged as a promising strategy for the treatment of undruggable therapeutic targets. Researchers have invested a great effort in developing druggable PROTACs; however, the problems associated with PROTACs, including poor solubility, metabolic stability, cell permeability, and pharmacokinetic profile, restrict their clinical utility. Thus, there is a pressing need to expand the size of the armory of PROTACs which will escalate the chances of pinpointing new PROTACs with optimum pharmacokinetic and pharmacodynamics properties. N- heterocycle is a class of organic frameworks that have been widely explored to construct new and novel PROTACs. This review provides an overview of recent efforts of medicinal chemists to develop N-heterocycle-based PROTACs as effective cancer therapeutics. Specifically, the recent endeavors centred on the discovery of PROTACs have been delved into various classes based on the E3 ligase they target (MDM2, IAP, CRBN, and other E3 ligases). Mechanistic insights revealed during the biological assessment of recently furnished Nheterocyclic- based PROTACs constructed via the utilization of ligands for various E3 ligases have been discussed.

Radiotherapeutic Strategies to Overcome Resistance of Breast Cancer Brain Metastases by Considering Immunogenic Aspects of Cancer Stem Cells

Breast cancer is the most diagnosed cancer in women, and symptomatic brain metastases (BCBMs) occur in 15-20% of metastatic breast cancer cases. Despite technological advances in radiation therapy (RT), the prognosis of patients is limited. This has been attributed to radioresistant breast cancer stem cells (BCSCs), among other factors. The aim of this review article is to summarize the evidence of cancer-stem-cell-mediated radioresistance in brain metastases of breast cancer from radiobiologic and radiation oncologic perspectives to allow for the better interpretability of preclinical and clinical evidence and to facilitate its translation into new therapeutic strategies. To this end, the etiology of brain metastasis in breast cancer, its radiotherapeutic treatment options, resistance mechanisms in BCSCs, and effects of molecularly targeted therapies in combination with radiotherapy involving immune checkpoint inhibitors are described and classified. This is considered in the context of the central nervous system (CNS) as a particular metastatic niche involving the blood-brain barrier and the CNS immune system. The compilation of this existing knowledge serves to identify possible synergistic effects between systemic molecularly targeted therapies and ionizing radiation (IR) by considering both BCSCs' relevant resistance mechanisms and effects on normal tissue of the CNS.

Investigating the mechanism of Xian-ling-lian-xia-fang for inhibiting vasculogenic mimicry in triple negative breast cancer via blocking VEGF/MMPs pathway

Background

Xian-ling-lian-xia-fang (XLLXF), a Chinese medicine decoction, is widely used in the treatment of triple negative breast cancer (TNBC). However, the underlying mechanism of XLLXF in TNBC treatment has not been totally elucidated.

Methods

Here, network pharmacology and molecular docking were used to explore the mechanism of Traditional Chinese medicine in the treatment of TNBC. Then, biological experiments were integrated to verify the results of network pharmacology.

Results

Network pharmacology showed that the candidate active ingredients mainly included quercetin, kaempferol, stigmasterol, and β-sitosterol through the “XLLXF–active ingredients–targets” network. Vascular endothelial growth factor A (VEGFA) and matrix metalloproteinase (MMP) 2 were the potential therapeutic targets obtained through the protein–protein interaction (PPI) network. Molecular docking confirmed that quercetin, kaempferol, stigmasterol, and β-sitosterol could stably combine with VEGFA and MMP2. Experimental verification showed that XLLXF could inhibit proliferation, colony ability, and vasculogenic mimicry (VM) formation and promote cell apoptosis in TNBC. Laser confocal microscopy found that XLLXF impaired F-actin cytoskeleton organization and inhibited epithelial mesenchymal transition. Animal experiments also found that XLLXF could inhibit tumor growth and VM formation in TNBC xenograft model. Western blot analysis and immunohistochemical staining showed that XLLXF inhibited the protein expression of VEGFA, MMP2, MMP9, Vimentin, VE-cadherin, and Twist1 and increased that of E-cadherin, tissue inhibitors of metalloproteinase (TIMP)-1, and TIMP-3 in vitro and in vivo.

Conclusions

Integrating the analysis of network pharmacology and experimental validation revealed that XLLXF could inhibit VM formation via downregulating the VEGF/MMPs signaling pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13020-022-00597-5.

Central Nervous System Metastases from Triple-Negative Breast Cancer: Current Treatments and Future Prospective

It is estimated that approximately one-third of patients with triple-negative breast cancer (TNBC) will develop brain metastases. The prognosis for patients with breast cancer brain metastasis has improved in the recent past, especially for hormone receptor and human epidermal growth factor receptor 2 (HER) positive subtypes. However, the overall survival rate for patients with triple-negative subtype remains poor. The development of newer treatment options, including antibody-drug conjugates such as Sacituzumab govitecan, is particularly encouraging. This article reviews the clinical outcomes, challenges, and current approach to the treatment of brain metastasis in TNBC. We have also briefly discussed newer treatment options and ongoing clinical trials. The development of brain metastasis significantly decreases the quality of life of patients with TNBC, and newer treatment strategies and therapeutics are the need of the hour for this disease subgroup.

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.

The Role of Breast Cancer Stem Cells in Chemoresistance and Metastasis in Triple-Negative Breast Cancer

Triple negative breast cancer (TNBC) remains an aggressive disease due to the lack of targeted therapies and low rate of response to chemotherapy that is currently the main treatment modality for TNBC. Breast cancer stem cells (BCSCs) are a small subpopulation of breast tumors and recognized as drivers of tumorigenesis. TNBC tumors are characterized as being enriched for BCSCs. Studies have demonstrated the role of BCSCs as the source of metastatic disease and chemoresistance in TNBC. Multiple targets against BCSCs are now under investigation, with the considerations of either selectively targeting BCSCs or co-targeting BCSCs and non-BCSCs (majority of tumor cells). This review article provides a comprehensive overview of recent advances in the role of BCSCs in TNBC and the identification of cancer stem cell biomarkers, paving the way for the development of new targeted therapies. The review also highlights the resultant discovery of cancer stem cell targets in TNBC and the ongoing clinical trials treating chemoresistant breast cancer. We aim to provide insights into better understanding the mutational landscape of BCSCs and exploring potential molecular signaling pathways targeting BCSCs to overcome chemoresistance and prevent metastasis in TNBC, ultimately to improve the overall survival of patients with this devastating disease.

Role of PARP in TNBC: Mechanism of Inhibition, Clinical Applications, and Resistance

Triple-negative breast cancer is a combative cancer type with a highly inflated histological grade that leads to poor theragnostic value. Gene, protein, and receptor-specific targets have shown effective clinical outcomes in patients with TNBC. Cells are frequently exposed to DNA-damaging agents. DNA damage is repaired by multiple pathways; accumulations of mutations occur due to damage to one or more pathways and lead to alterations in normal cellular mechanisms, which lead to development of tumors. Advances in target-specific cancer therapies have shown significant momentum; most treatment options cause off-target toxicity and side effects on healthy tissues. PARP (poly(ADP-ribose) polymerase) is a major protein and is involved in DNA repair pathways, base excision repair (BER) mechanisms, homologous recombination (HR), and nonhomologous end-joining (NEJ) deficiency-based repair mechanisms. DNA damage repair deficits cause an increased risk of tumor formation. Inhibitors of PARP favorably kill cancer cells in BRCA-mutations. For a few years, PARPi has shown promising activity as a chemotherapeutic agent in BRCA1- or BRCA2-associated breast cancers, and in combination with chemotherapy in triple-negative breast cancer. This review covers the current results of clinical trials testing and future directions for the field of PARP inhibitor development.

TNBC: Potential Targeting of Multiple Receptors for a Therapeutic Breakthrough, Nanomedicine, and Immunotherapy

Triple-negative breast cancer (TNBC) is a heterogeneous, recurring cancer associated with a high rate of metastasis, poor prognosis, and lack of therapeutic targets. Although target-based therapeutic options are approved for other cancers, only limited therapeutic options are available for TNBC. Cell signaling and receptor-specific targets are reportedly effective in patients with TNBC under specific clinical conditions. However, most of these cancers are unresponsive, and there is a requirement for more effective treatment modalities. Further, there is a lack of effective biomarkers that can distinguish TNBC from other BC subtypes. ER, PR, and HER2 help identify TNBC and are widely used to identify patients who are most likely to respond to diverse therapeutic strategies. In this review, we discuss the possible treatment options for TNBC based on its inherent subtype receptors and pathways, such as p53 signaling, AKT signaling, cell cycle regulation, DNA damage, and programmed cell death, which play essential roles at multiple stages of TNBC development. We focus on poly-ADP ribose polymerase 1, androgen receptor, vascular endothelial growth factor receptor, and epidermal growth factor receptor as well as the application of nanomedicine and immunotherapy in TNBC and discuss their potential applications in drug development for TNBC.

GBP5 Repression Suppresses the Metastatic Potential and PD-L1 Expression in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype because of its high metastatic potential. Immune evasion due to aberrant expression of programmed cell death ligand 1 (PD-L1) has also been reported recently in metastatic TNBC. However, the mechanism underlying metastatic progression and PD-L1 upregulation in TNBC is still largely unknown. Here, we found that guanylate binding protein 5 (GBP5) is expressed in higher levels in TNBC tissues than in non-TNBC and normal mammary tissues and serves as a poorer prognostic marker in breast cancer patients. Transwell cultivation indicated that GBP5 expression is causally related to cellular migration ability in the detected TNBC cell lines. Moreover, the computational simulation of the gene set enrichment analysis (GSEA) program against the GBP5 signature generated from its coexpression with other somatic genes in TNBC revealed that GBP5 upregulation may be associated with the activation of interferon gamma (IFN-γ)-responsive and NF-κB-related signaling cascades. In addition, we found that the coexpression of GBP5 with PD-L1 was significantly positive correlation in TNBC tissues. Robustly, our data showed that GBP5 knockdown in TNBC cells harboring a higher GBP5 level dramatically suppresses the number of migrated cells, the activity of IFN-γ/STAT1 and TNF-α/NF-κB signaling axes, and the expression of PD-L1. Importantly, the signature combining a higher GBP5 and PD-L1 level predicted the shortest time interval of brain metastasis in breast cancer patients. These findings not only uncover the oncogenic function of GBP5 but also provide a new strategy to combat metastatic/immunosuppressive TNBC by targeting GBP5 activity.

GBP5 Serves as a Potential Marker to Predict a Favorable Response in Triple-Negative Breast Cancer Patients Receiving a Taxane-Based Chemotherapy

Pre-operative (neoadjuvant) or post-operative (adjuvant) taxane-based chemotherapy is still commonly used to treat patients with triple-negative breast cancer (TNBC). However, there are still no effective biomarkers used to predict the responsiveness and efficacy of taxane-based chemotherapy in TNBC patients. Here we find that guanylate-binding protein 5 (GBP5), compared to other GBPs, exhibits the strongest prognostic significance in predicting TNBC recurrence and progression. Whereas GBP5 upregulation showed no prognostic significance in non-TNBC patients, a higher GBP5 level predicted a favorable recurrence and progression-free condition in the TNBC cohort. Moreover, we found that GBP5 expression negatively correlated with the 50% inhibitory concentration (IC₅₀) of paclitaxel in a panel of TNBC cell lines. The gene knockdown of GBP5 increased the IC₅₀ of paclitaxel in the tested TNBC cells. In TNBC patients receiving neoadjuvant or adjuvant chemotherapy, a higher GBP5 level strongly predicted a good responsiveness. Computational simulation by the Gene Set Enrichment Analysis program and cell-based assays demonstrated that GBP5 probably enhances the cytotoxic effectiveness of paclitaxel via activating the Akt/mTOR signaling axis and suppressing autophagy formation in TNBC cells. These findings suggest that GBP5 could be a good biomarker to predict a favorable outcome in TNBC patients who decide to receive a taxane-based neoadjuvant or adjuvant therapy.