The amino acid transporter SLC7A11 expression in breast cancer

Breast cancer (BC), characterized by its diverse molecular profiles and clinical outcomes, presents a significant challenge in the development of effective therapeutic strategies. Metabolic reprogramming, a defining characteristic of cancer, has emerged as a promising target for novel therapies. SLC7A11, an amino acid transporter that facilitates cysteine uptake in exchange for glutamate, plays a crucial role in sustaining the altered metabolism of cancer cells. This study delves into the comprehensive analysis of SLC7A11 at the genomic, transcriptomic, and protein levels in extensive BC datasets to elucidate its potential role in different BC subtypes. SLC7A11 gene copy number and mRNA expression were evaluated using the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) cohort (n = 1,980) and Breast Cancer Gene Expression Miner (n = 4,712). SLC7A11 protein was assessed using immunohistochemistry in a large BC cohort (n = 1,981). Additionally, The Cancer Genome Atlas (TCGA) dataset was used to explore SLC7A11 DNA methylation patterns using MethSurv (n = 782) and association of SLC7A11 mRNA expression with immune infiltrates using TIMER (n = 1,100). High SLC7A11 mRNA and SLC7A11 protein expression were significantly associated with high tumor grade (p ≤ .02), indicating a potential role in cancer progression. Interestingly, SLC7A11 copy number gain was observed in HER2+ tumors (p = .01), suggesting a subtype-specific association. In contrast, SLC7A11 mRNA expression was higher in the basal-like/triple-negative (TN; p < .001) and luminal B tumors (p = .02), highlighting its differential expression across BC subtypes. Notably, high SLC7A11 protein expression was predominantly observed in Estrogen Receptor (ER)-negative and Triple Negative (TN) BC, suggesting a role in these aggressive subtypes. Further analysis revealed that SLC7A11 was positively correlated with other amino acid transporters and enzymes associated with glutamine metabolism, implying a coordinated role in metabolic regulation. Additionally, SLC7A11 gene expression was positively associated with neutrophil and macrophage infiltration, suggesting a potential link between SLC7A11 and tumor immunity. Our findings suggest that SLC7A11 plays a significant role in BC metabolism, demonstrating differential expression across subtypes and associations with poor patient outcomes. Further functional studies are warranted to elucidate the precise mechanisms by which SLC7A11 contributes to BC progression and to explore its potential as a therapeutic target.

Identification of biomimetic nanoplatform-mediated delivery of si-ISG15 for treatment of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is recognized as the most malicious form of breast cancer and exhibits an alarming tendency for recurrence, a heightened propensity for metastasis, and an overwhelmingly grim prognosis. Therefore, effective therapy approaches for TNBC are urgently required. In this study, the interferon-stimulated gene 15 (ISG15) expression level was analyzed by bioinformatics and verified by Western blot analysis. The effects of ISG15 on the proliferation and metastasis of TNBC cells were assessed using MTT, Colony formation, EdU, Transwell, and Flow cytometry assays. We also developed a cancer cell-biomimetic nanoparticle delivery system and evaluated its therapeutic efficacy in vivo. In this study, we reported that ISG15 was upregulated in TNBC, and its high expression level correlated with an increased risk of tumorigenesis. Through in vitro and in vivo studies, we discovered that ISG15 knockdown drastically suppressed cell proliferation, invasion, and migration and induced apoptosis in TNBC cells. Our findings revealed that ISG15 was a candidate therapeutic target in TNBC because of its key role in malignant growth and invasion. Moreover, co-immunoprecipitation showed that ISG15 exerted oncogenic functions through its interaction with ATP binding cassette subfamily E member 1 and activated the Janus kinase/signal transducers and activators of the transcription signaling pathway. Furthermore, we created a nanoparticle-based siRNA camouflaged using a cancer cell membrane vesicle delivery system (the CM@NP complex) and confirmed its therapeutic effects in vivo. Our findings confirmed that ISG15 may play a pivotal oncogenic role in the development of TNBC and that CM@siRNA-NP complexes are an effective delivery system and a novel biological strategy for treating TNBC.

LINC01572 promotes triple-negative breast cancer progression through EIF4A3-mediated β-catenin mRNA nuclear exportation

Long noncoding RNAs have been reported to be involved in the development of breast cancer. LINC01572 was previously reported to promote the development of various tumors. However, the potential biological function of LINC01572 in breast cancer remains largely unknown. R language was used to perform bioinformatic analysis of The Cancer Genome Atlas data. The expression level of RNAs was examined by RT-qPCR. The effect of knocking down or overexpression LINC01572 in triple-negative breast cancer (TNBC) cell lines was evaluated by detecting cell proliferation, migrant action. RNA immunoprecipitation assay and RNA pull-down assay were performed to explore the regulatory relationship between LINC01572, EIF4A3, and β-catenin. Bioinformatics analysis identifies LINC01572 as an oncogene of breast cancer. LINC01572 is over-expressed in TNBC tissues and cell lines, correlated with poor clinical prognosis in BC patients. Cell function studies confirmed that LINC01572 facilitated the proliferation and migration of TNBC cells in both vivo and vitro. Mechanistically, β-catenin mRNA and EIF4A3 combine spatially to form a complex, LINC01572 helps transport this complex from the nucleus to the cytoplasm, thereby facilitating the translation of β-catenin. Our findings confirm that LINC01572 acts as a tumor promoter and may act as a biomarker in TNBC. In addition, novel molecular regulatory relationships involving LINC01572/EIF4A3/β-catenin are critical to the development of TNBC, which led to a new understanding of the mechanisms of TNBC progression and shows a new target for precision treatment for TNBC.

Identification of Subtypes in Triple-negative Breast Cancer Based on Shared Genes Between Immunity and Cancer Stemness

The correlation between triple-negative breast cancer (TNBC) and genes related to immunity and cancer stemness, particularly shared genes, remains unclear. This study aimed to investigate the correlation of immunity and cancer stemness with the molecular subtyping and survival rates in TNBC using bioinformatics approaches. Differential gene analysis was conducted to identify TNBC-associated differentially expressed genes (DEGs). Cancer stem cell (CSC)-related genes were obtained using weighted gene coexpression network analysis. Immune-related gene sets were retrieved from the literature. Venn analysis was performed to identify the shared DEGs between immunity and cancer stemness in TNBC. Cluster analysis and survival analysis based on the expression of these genes were conducted to identify TNBC subtypes with significant survival differences. A total of 5259 TNBC-associated DEGs, 2214 CSC-related genes, 1793 immune-related genes, and 44 shared DEGs between immunity and cancer stemness were obtained. Among them, 3 shared DEGs were closely associated with TNBC survival rates ( P <0.05). Cluster and survival analyses revealed that among 3 subtypes, cluster2 exhibited the best survival rate, and cluster3 showed the worst survival rate ( P <0.05). Dendritic cells were highly infiltrated in cluster2, while plasma cells and resting mast cells were highly infiltrated in cluster3 ( P <0.05). Genes shared by immunity and cancer stemness were capable of classifying TNBC samples. TNBC patients of different subtypes exhibited significant differences in immune profiles, genetic mutations, and drug sensitivity. These findings could provide new insights into the pathogenesis of TNBC, the immune microenvironment, and the selection of therapeutic targets for drug treatment.

CDK inhibition results in pharmacologic BRCAness increasing sensitivity to olaparib in BRCA1-WT and olaparib resistant in Triple Negative Breast Cancer

One in three Triple Negative Breast Cancer (TNBC) is Homologous Recombination Deficient (HRD) and susceptible to respond to PARP inhibitor (PARPi), however, resistance resulting from functional HR restoration is frequent. Thus, pharmacologic approaches that induce HRD are of interest. We investigated the effectiveness of CDK-inhibition to induce HRD and increase PARPi sensitivity of TNBC cell lines and PDX models. Two CDK-inhibitors (CDKi), the broad range dinaciclib and the CDK12-specific SR-4835, strongly reduced the expression of key HR genes and impaired HR functionality, as illustrated by BRCA1 and RAD51 nuclear foci obliteration. Consequently, both CDKis showed synergism with olaparib, as well as with cisplatin and gemcitabine, in a range of TNBC cell lines and particularly in olaparib-resistant models. In vivo assays on PDX validated the efficacy of dinaciclib which increased the sensitivity to olaparib of 5/6 models, including two olaparib-resistant and one BRCA1-WT model. However, no olaparib response improvement was observed in vivo with SR-4835. These data support that the implementation of CDK-inhibitors could be effective to sensitize TNBC to olaparib as well as possibly to cisplatin or gemcitabine.

Survival outcomes of patients with HER2/neu-positive breast cancer with germline BRCA mutations

BACKGROUND

Breast cancer (BC) with germline BRCA1/2 mutations and their association with triple-negative BC has been thoroughly investigated. However, some carriers of BRCA1/2 mutations have human epidermal growth factor receptor 2 (HER2/neu)-positive BC, which has a different targeted therapy approach, and data are scarce for this patient population. The authors sought to characterize the clinical characteristics and outcomes of patients with HER2/neu-positive BC who had germline BRCA1/2 mutations.

METHODS

This was a retrospective analysis of data from 1099 patients diagnosed with HER2/neu-positive BC who were screened for germline BRCA mutations between 1996 and 2022. Clinicopathologic features and survival rates were analyzed by BRCA mutation status. Univariate and multivariable Cox proportional hazards regression models were used to analyze the association between clinical variables and outcomes.

RESULTS

Of 1099 patients with HER2/neu-positive BC, 73 (6.6%) tested positive for BRCA1/2 mutations. Age, race, and tumor characteristics did not differ between BRCA noncarriers and carriers. At a median follow-up of 78.6 months, the 5-year recurrence-free survival rate was 85% in BRCA carriers and 87% in noncarriers (p = .79), and the 5-year overall survival rate was 94% in BRCA carriers and 94% in noncarriers (p = .78). In a multivariable model, BRCA was not associated with recurrence-free survival (hazard ratio, 0.99; 95% confidence interval, 0.51-1.90; p = .96) or overall survival (hazard ratio, 0.83; 95% confidence interval, 0.33-2.07; p = .69).

CONCLUSIONS

BRCA1/2 mutations occurred in 6.6% of patients with HER2/neu-positive BC and did not affect survival outcomes. Assessing the potential benefits of new treatment strategies, such as combining anti-HER2/neu therapies with poly(ADP-ribose) polymerase inhibitors, may lead to enhanced outcomes for these patients.

Cyclin-dependent kinase 7 (CDK7) inhibitors as a novel therapeutic strategy for different molecular types of breast cancer

BACKGROUND

Cyclin-dependent kinase (CDK) 7 is aberrantly overexpressed in many types of cancer and is an attractive target for cancer therapy due to its dual role in transcription and cell cycle progression. Moreover, CDK7 can directly modulate the activities of estrogen receptor (ER), which is a major driver in breast cancer. Breast cancer cells have exhibited high sensitivity to CDK7 inhibition in pre-clinical studies.

METHODS

In this review, we provide a comprehensive summary of the latest insights into CDK7 biology and recent advancements in CDK7 inhibitor development for breast cancer treatment. We also discuss the current application of CDK7 inhibitors in different molecular types of breast cancer to provide potential strategies for the treatment of breast cancer.

RESULTS

Significant progress has been made in the development of selective CDK7 inhibitors, which show efficacy in both triple-negative breast cancer (TNBC) and hormone receptor-positive breast cancer (HR+). Moreover, combined with other agents, CDK7 inhibitors may provide synergistic effects for endocrine therapy and chemotherapy. Thus, high-quality studies for developing potent CDK7 inhibitors and investigating their applications in breast cancer therapy are rapidly emerging.

CONCLUSION

CDK7 inhibitors have emerged as a promising therapeutic strategy and have demonstrated significant anti-cancer activity in different subtypes of breast cancer, especially those that have been resistant to current therapies.

CCAAT enhancer binding protein delta activates vesicle associated membrane protein 3 transcription to enhance chemoresistance and extracellular PD-L1 expression in triple-negative breast cancer

BACKGROUND

Chemoresistance and immunosuppression are two major obstacles in the current anti-cancer treatments. This study investigates the involvements of a CCAAT enhancer binding protein delta (CEBPD)/vesicle associated membrane protein 3 (VAMP3) axis in paclitaxel (PTX) resistance and immune evasion in triple-negative breast cancer (TNBC).

METHODS

PTX resistance-related genes were screened by bioinformatics. CEBPD and VAMP3 expression in clinical TNBC samples was examined by immunohistochemistry. Three PTX-resistant TNBC cell lines (MDA-MB-231/PTX, MDA-MB-468/PTX and MDA-MB-453/PTX) were generated, and their drug resistance was analyzed. Autophagy of cells was analyzed by immunofluorescence staining. Interaction between CEBPD and VAMP3 promoter was identified by immunoprecipitation and luciferase assays. The extracellular expression of programmed cell death-ligand 1 (PD-L1) in TNBC cells was detected. Extracellular vesicles (EVs) from TNBC cells were isolated to examine their effects on CD8+ T cell exhaustion.

RESULTS

CEBPD and VAMP3 were upregulated in chemo-resistant tissue samples and in PTX-resistant TNBC cells. The CEBPD downregulation enhanced PTX sensitivity of cells. However, further upregulation of VAMP3 in cells restored PTX resistance, which was likely due to the activation of autophagy, as the autophagy antagonist chloroquine enhanced PTX sensitivity of cells. CEBPD was found to bind to the VAMP3 promoter to activate its transcription. The CEBPD/VAMP3 axis also increased the PD-L1 expression in the conditioned medium of TNBC cells. The TNBC cell-derived EVs increased the exhaustion of co-cultured CD8+ T cells.

CONCLUSION

This study provides novel evidence that CEBPD plays a key role in enhancing PTX resistance in TNBC cells across various subtypes through VAMP3-mediated autophagy activation. Additionally, the CEBPD/VAMP3 axis also increases extracellular PD-L1 level, delivered by cancer cell-derived EVs, to suppress CD8+ T cell-mediated anti-tumor immune response. These significant observations may provide new insights into the treatment of TNBC, suggesting CEBPD and VAMP3 as promising targets to overcome treatment resistance.

Type-I protein arginine methyltransferase inhibition primes anti-programmed cell death protein 1 immunotherapy in triple-negative breast cancer

BACKGROUND

Immune-checkpoint blockade (ICB) therapy shows promise for treating aggressive triple-negative breast cancer (TNBC). However, only some patients benefit from ICB, revealing an urgent need for identifying novel strategies for sensitizing patients to ICB. Previously, the authors demonstrated that type-I protein arginine methyltransferases (PRMTs) regulated antiviral innate-immune responses in TNBC by altering RNA splicing. This study aimed to explore the effects of targeting type-I PRMTs on the tumor microenvironment (TME) and the efficacy of ICB therapy against TNBC.

METHODS

Single-cell transcriptomic analysis was performed to investigate the effects of type-I PRMT inhibition on the TME, especially T-cell subsets. Single-cell T-cell receptor sequencing was performed to analyze the diversity and dynamics of the T-cell repertoire. A syngeneic murine model of TNBC was used to evaluate the therapeutic efficacy and immune memory effect of combining a type-I PRMT inhibitor (MS023) with an anti-programmed cell death protein 1 (PD-1) antibody.

RESULTS

Type-I PRMT inhibition combined with anti-PD-1 therapy reduced tumor growth. Mechanistically, type-I PRMT inhibition reshaped the TME. Increased CD8 T-cell infiltration was verified using flow cytometry. Increased clonotypes and clonal diversity were also observed after MS023 treatment, which contributed to immune memory following combination treatment.

CONCLUSIONS

Targeting type-I PRMT can potentially improve immunotherapeutic efficacies in patients with TNBC. By enhancing the tumor immunogenicity and promoting a more favorable immune microenvironment, this combined approach may enable more patients with TNBC to benefit from immunotherapies.

PDZK1 suppresses TNBC development and sensitizes TNBC cells to erlotinib via the EGFR pathway

Epidermal growth factor receptor (EGFR)-targeted drugs (erlotinib, etc.) are used to treat multiple types of tumours. EGFR is highly expressed in most triple-negative breast cancer (TNBC) patients. However, only a small proportion of TNBC patients benefit from EGFR-targeted drugs in clinical trials, and the resistance mechanism is unclear. Here, we found that PDZ domain containing 1 (PDZK1) is downregulated in erlotinib-resistant TNBC cells, suggesting that PDZK1 downregulation is related to erlotinib resistance in TNBC. PDZK1 binds to EGFR. Through this interaction, PDZK1 promotes EGFR degradation by enhancing the binding of EGFR to c-Cbl and inhibits EGFR phosphorylation by hindering EGFR dimerisation. We also found that PDZK1 is specifically downregulated in TNBC tissues and correlated with a poor prognosis in TNBC patients. In vitro and in vivo functional assays showed that PDZK1 suppressed TNBC development. Restoration of EGFR expression or kinase inhibitor treatment reversed the degree of cell malignancy induced by PDZK1 overexpression or knockdown, respectively. PDZK1 overexpression sensitised TNBC cells to erlotinib both in vitro and in vivo. In conclusion, PDZK1 is a significant prognostic factor for TNBC and a potential molecular therapeutic target for reversing erlotinib resistance in TNBC cells.

Single cell lineage tracing reveals clonal dynamics of anti-EGFR therapy resistance in triple negative breast cancer

BACKGROUND

Most primary Triple Negative Breast Cancers (TNBCs) show amplification of the Epidermal Growth Factor Receptor (EGFR) gene, leading to increased protein expression. However, unlike other EGFR-driven cancers, targeting this receptor in TNBC yields inconsistent therapeutic responses.

METHODS

To elucidate the underlying mechanisms of this variability, we employ cellular barcoding and single-cell transcriptomics to reconstruct the subclonal dynamics of EGFR-amplified TNBC cells in response to afatinib, a tyrosine kinase inhibitor (TKI) that irreversibly inhibits EGFR.

RESULTS

Integrated lineage tracing analysis revealed a rare pre-existing subpopulation of cells with distinct biological signature, including elevated expression levels of Insulin-Like Growth Factor Binding Protein 2 (IGFBP2). We show that IGFBP2 overexpression is sufficient to render TNBC cells tolerant to afatinib treatment by activating the compensatory insulin-like growth factor I receptor (IGF1-R) signalling pathway. Finally, based on reconstructed mechanisms of resistance, we employ deep learning techniques to predict the afatinib sensitivity of TNBC cells.

CONCLUSIONS

Our strategy proved effective in reconstructing the complex signalling network driving EGFR-targeted therapy resistance, offering new insights for the development of individualized treatment strategies in TNBC.

Unveiling the Mechanism of the ChaiShao Shugan Formula Against Triple-Negative Breast Cancer

Background

The ChaiShao Shugan Formula (CSSGF) is a traditional Chinese medicine formula with recently identified therapeutic value in triple-negative breast cancer (TNBC). This study aimed to elucidate the underlying mechanism of CSSGF in TNBC treatment.

Methods

TNBC targets were analyzed using R and data were from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. The major ingredients and related protein targets of CSSGF were explored via the Traditional Chinese Medicine Systems Pharmacology database, and an ingredient-target network was constructed via Cytoscape to identify hub genes. The STRING database was used to construct the PPI network. GO and KEGG enrichment analyses were performed via R to obtain the main targets. The online tool Kaplan‒Meier plotter was used to identify the prognostic genes. Molecular docking was applied to the core target genes and active ingredients. MDA-MB-231 and MCF-7 cell lines were used to verify the efficacy of the various drugs.

Results

A total of 4562 genes were screened as TNBC target genes. The PPI network consisted of 89 nodes and 845 edges. Our study indicated that quercetin, beta-sitosterol, luteolin and catechin might be the core ingredients of CSSGF, and EGFR and c-Myc might be the latent therapeutic targets of CSSGF in the treatment of TNBC. GO and KEGG analyses indicated that the anticancer effect of CSSGF on TNBC was mainly associated with DNA binding, transcription factor binding, and other biological processes. The related signaling pathways mainly involved the TNF-a, IL-17, and apoptosis pathways. The molecular docking data indicated that quercetin, beta-sitosterol, luteolin, and catechin had high affinity for EGFR, JUN, Caspase-3 and ESR1, respectively. In vitro, we found that CSSGF could suppress the expression of c-Myc or promote the expression of EGFR. In addition, we found that quercetin downregulates c-Myc expression in two BC cell lines.

Conclusion

This study revealed the effective ingredients and latent molecular mechanism of action of CSSGF against TNBC and confirmed that quercetin could target c-Myc to induce anti-BC effects.

U2AF2-SNORA68 promotes triple-negative breast cancer stemness through the translocation of RPL23 from nucleoplasm to nucleolus and c-Myc expression

BACKGROUND

Small nucleolar RNAs (snoRNAs) play key roles in ribosome biosynthesis. However, the mechanism by which snoRNAs regulate cancer stemness remains to be fully elucidated.

METHODS

SNORA68 expression was evaluated in breast cancer tissues by in situ hybridization and qRT‒PCR. Proliferation, migration, apoptosis and stemness analyses were used to determine the role of SNORA68 in carcinogenesis and stemness maintenance. Mechanistically, RNA pull-down, RNA immunoprecipitation (RIP), cell fractionation and coimmunoprecipitation assays were conducted.

RESULTS

SNORA68 exhibited high expression in triple-negative breast cancer (TNBC) and was significantly correlated with tumor size (P = 0.048), ki-67 level (P = 0.037), and TNM stage (P = 0.015). The plasma SNORA68 concentration was significantly lower in patients who achieved clinical benefit. The SNORA68-high patients had significantly shorter disease-free survival (DFS) (P = 0.036). Functionally, SNORA68 was found to promote the cell stemness and carcinogenesis of TNBC in vitro and in vivo. Furthermore, elevated SNORA68 expression led to increased nucleolar RPL23 expression and retained RPL23 in the nucleolus by binding U2AF2. RPL23 in the nucleolus subsequently upregulated c-Myc expression. This pathway was validated using a xenograft model.

CONCLUSION

U2AF2-SNORA68 promotes TNBC stemness by retaining RPL23 in the nucleolus and increasing c-Myc expression, which provides new insight into the regulatory mechanism of stemness.

Heat shock factor 1 inhibition enhances the effects of modulated electro hyperthermia in a triple negative breast cancer mouse model

Female breast cancer is the most diagnosed cancer worldwide. Triple negative breast cancer (TNBC) is the most aggressive type and there is no existing endocrine or targeted therapy. Modulated electro-hyperthermia (mEHT) is a non-invasive complementary cancer therapy using an electromagnetic field generated by amplitude modulated 13.56 MHz frequency that induces tumor cell destruction. However, we have demonstrated a strong induction of the heat shock response (HSR) by mEHT, which can result in thermotolerance. We hypothesized that inhibition of the heat shock factor 1 (HSF1) can synergize with mEHT and enhance tumor cell-killing. Thus, we either knocked down the HSF1 gene with a CRISPR/Cas9 lentiviral construct or inhibited HSF1 with a specific small molecule inhibitor: KRIBB11 in vivo. Wild type or HSF1-knockdown 4T1 TNBC cells were inoculated into the mammary gland's fat pad of BALB/c mice. Four mEHT treatments were performed every second day and the tumor growth was followed by ultrasound and caliper. KRIBB11 was administrated intraperitoneally at 50 mg/kg daily for 8 days. HSF1 and Hsp70 expression were assessed. HSF1 knockdown sensitized transduced cancer cells to mEHT and reduced tumor growth. HSF1 mRNA expression was significantly reduced in the KO group when compared to the empty vector group, and consequently mEHT-induced Hsp70 mRNA upregulation diminished in the KO group. Immunohistochemistry (IHC) confirmed the inhibition of Hsp70 upregulation in mEHT HSF1-KO group. Demonstrating the translational potential of HSF1 inhibition, combined therapy of mEHT with KRIBB11 significantly reduced tumor mass compared to either monotherapy. Inhibition of Hsp70 upregulation by mEHT was also supported by qPCR and IHC. In conclusion, we suggest that mEHT-therapy combined with HSF1 inhibition can be a possible new strategy of TNBC treatment with great translational potential.

Highly Efficient Photoswitchable Smart Polymeric Nanovehicle for Gene and Anticancer Drug Delivery in Triple-Negative Breast Cancer

Over the past few decades, there has been significant interest in smart drug delivery systems capable of carrying multiple drugs efficiently, particularly for treating genetic diseases such as cancer. Despite the development of various drug delivery systems, a safe and effective method for delivering both anticancer drugs and therapeutic genes for cancer therapy remains elusive. In this study, we describe the synthesis of a photoswitchable smart polymeric vehicle comprising a photoswitchable spiropyran moiety and an amino-acid-based cationic monomer-based block copolymer using reversible addition-fragmentation chain transfer (RAFT) polymerization. This system aims at diagnosing triple-negative breast cancer and subsequently delivering genes and anticancer agents. Triple-negative breast cancer patients have elevated concentrations of Cu2+ ions, making them excellent targets for diagnosis. The polymer can detect Cu2+ ions with a low limit of detection value of 9.06 nM. In vitro studies on doxorubicin drug release demonstrated sustained delivery at acidic pH level similar to the tumor environment. Furthermore, the polymer exhibited excellent blood compatibility even at the concentration as high as 500 μg/mL. Additionally, it displayed a high transfection efficiency of approximately 82 ± 5% in MDA-MB-231 triple-negative breast cancer cells at an N/P ratio of 50:1. It is observed that mitochondrial membrane depolarization and intracellular reactive oxygen species generation are responsible for apoptosis and the higher number of apoptotic cells, which occurred through the arrest of the G2/M phase of the cell cycle were observed. Therefore, the synthesized light-responsive cationic polymer may be an effective system for diagnosis, with an efficient anticancer drug and gene carrier for the treatment of triple-negative breast cancer in the future.

SF3A2 promotes progression and cisplatin resistance in triple-negative breast cancer via alternative splicing of MKRN1

Triple-negative breast cancer (TNBC) is the deadliest subtype of breast cancer owing to the lack of effective therapeutic targets. Splicing factor 3a subunit 2 (SF3A2), a poorly defined splicing factor, was notably elevated in TNBC tissues and promoted TNBC progression, as confirmed by cell proliferation, colony formation, transwell migration, and invasion assays. Mechanistic investigations revealed that E3 ubiquitin-protein ligase UBR5 promoted the ubiquitination-dependent degradation of SF3A2, which in turn regulated UBR5, thus forming a feedback loop to balance these two oncoproteins. Moreover, SF3A2 accelerated TNBC progression by, at least in part, specifically regulating the alternative splicing of makorin ring finger protein 1 (MKRN1) and promoting the expression of the dominant and oncogenic isoform, MKRN1-T1. Furthermore, SF3A2 participated in the regulation of both extrinsic and intrinsic apoptosis, leading to cisplatin resistance in TNBC cells. Collectively, these findings reveal a previously unknown role of SF3A2 in TNBC progression and cisplatin resistance, highlighting SF3A2 as a potential therapeutic target for patients with TNBC.

Optical imaging reveals chemotherapy-induced metabolic reprogramming of residual disease and recurrence

Fewer than 20% of triple-negative breast cancer patients experience long-term responses to mainstay chemotherapy. Resistant tumor subpopulations use alternative metabolic pathways to escape therapy, survive, and eventually recur. Here, we show in vivo, longitudinal metabolic reprogramming in residual disease and recurrence of triple-negative breast cancer xenografts with varying sensitivities to the chemotherapeutic drug paclitaxel. Optical imaging coupled with metabolomics reported an increase in non-glucose-driven mitochondrial metabolism and an increase in intratumoral metabolic heterogeneity during regression and residual disease in resistant MDA-MB-231 tumors. Conversely, sensitive HCC-1806 tumors were primarily reliant on glucose uptake and minimal changes in metabolism or heterogeneity were observed over the tumors' therapeutic life cycles. Further, day-matched resistant HCC-1806 tumors revealed a higher reliance on mitochondrial metabolism and elevated metabolic heterogeneity compared to sensitive HCC-1806 tumors. Together, metabolic flexibility, increased reliance on mitochondrial metabolism, and increased metabolic heterogeneity are defining characteristics of persistent residual disease, features that will inform the appropriate type and timing of therapies.

Exploring the effectiveness of molecular subtypes, biomarkers, and genetic variations as first-line treatment predictors in Asian breast cancer patients: a systematic review and meta-analysis

BACKGROUND

Breast cancer incidence has been on the rise significantly in the Asian population, occurring at an earlier age and a later stage. The potential predictive value of molecular subtypes, biomarkers, and genetic variations has not been deeply explored in the Asian population. This study evaluated the effect of molecular subtype classification and the presence or absence of biomarkers and genetic variations on pathological complete response (pCR) after neoadjuvant treatment in Asian breast cancer patients.

METHODS

A systematic search was conducted in MEDLINE (PubMed), Science Direct, Scopus, and Cochrane Library databases. Studies were selected if they included Asian breast cancer patients treated with neoadjuvant chemotherapy and contained data for qualitative or quantitative analyses. The quality of the included studies was assessed using the Newcastle Ottawa Scale. Following the random effects model, pooled odds ratios or hazard ratios with 95% confidence intervals for pCR were analysed using Review Manager Software. Heterogeneity between studies was assessed using Cochran's Q-test and I2 test statistics.

RESULTS

In total, 19,708 Asian breast cancer patients were pooled from 101 studies. In the neoadjuvant setting, taxane-anthracycline (TA) chemotherapy showed better pCR outcomes in triple-negative breast cancer (TNBC) (p<0.0001) and human epidermal growth factor receptor 2 enriched (HER2E) (p<0.0001) than luminal breast cancer patients. Similarly, taxane-platinum (TP) chemotherapy also showed better pCR outcomes in TNBC (p<0.0001) and HER2E (p<0.0001). Oestrogen receptor (ER)-negative, progesterone receptor (PR)-negative, HER2-positive and high Ki-67 were significantly associated with better pCR outcomes when treated with either TA or TP. Asian breast cancer patients harbouring wildtype PIK3CA were significantly associated with better pCR outcomes when treated with TA in the neoadjuvant setting (p=0.001).

CONCLUSIONS

In the neoadjuvant setting, molecular subtypes (HER2E and TNBC), biomarkers (ER, PR, HER2, HR, Ki-67, nm23-H1, CK5/6, and Tau), and gene (PIK3CA) are associated with increased pCR rates in Asian breast cancer patients. Hence, they could be further explored for their possible role in first-line treatment response, which can be utilised to treat breast cancer more efficiently in the Asian population. However, it needs to be further validated with additional powered studies.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42021246295.

Oncolytic adenovirus encoding apolipoprotein A1 suppresses metastasis of triple-negative breast cancer in mice

BACKGROUND

Dysregulation of cholesterol metabolism is associated with the metastasis of triple-negative breast cancer (TNBC). Apolipoprotein A1 (ApoA1) is widely recognized for its pivotal role in regulating cholesterol efflux and maintaining cellular cholesterol homeostasis. However, further exploration is needed to determine whether it inhibits TNBC metastasis by affecting cholesterol metabolism. Additionally, it is necessary to investigate whether ApoA1-based oncolytic virus therapy can be used to treat TNBC.

METHODS

In vitro experiments and mouse breast cancer models were utilized to evaluate the molecular mechanism of ApoA1 in regulating cholesterol efflux and inhibiting breast cancer progression and metastasis. The gene encoding ApoA1 was inserted into the adenovirus genome to construct a recombinant adenovirus (ADV-ApoA1). Subsequently, the efficacy of ADV-ApoA1 in inhibiting the growth and metastasis of TNBC was evaluated in several mouse models, including orthotopic breast cancer, spontaneous breast cancer, and human xenografts. In addition, a comprehensive safety assessment of Syrian hamsters and rhesus monkeys injected with oncolytic adenovirus was conducted.

RESULTS

This study found that dysregulation of cholesterol homeostasis is critical for the progression and metastasis of TNBC. In a mouse orthotopic model of TNBC, a high-cholesterol diet promoted lung and liver metastasis, which was associated with keratin 14 (KRT14), a protein responsible for TNBC metastasis. Furthermore, studies have shown that ApoA1, a cholesterol reverse transporter, inhibits TNBC metastasis by regulating the cholesterol/IKBKB/FOXO3a/KRT14 axis. Moreover, ADV-ApoA1 was found to promote cholesterol efflux, inhibit tumor growth, reduce lung metastasis, and prolonged the survival of mice with TNBC. Importantly, high doses of ADV-ApoA1 administered intravenously and subcutaneously were well tolerated in rhesus monkeys and Syrian hamsters.

CONCLUSIONS

This study provides a promising oncolytic virus treatment strategy for TNBC based on targeting dysregulated cholesterol metabolism. It also establishes a basis for subsequent clinical trials of ADV-ApoA1 in the treatment of TNBC.

AIbZIP/CREB3L4 Promotes Cell Proliferation via the SKP2-p27 Axis in Luminal Androgen Receptor Subtype Triple-Negative Breast Cancer

Breast cancer ranks first in incidence and fifth in cancer-related deaths among all types of cancer globally. Among breast cancer, triple-negative breast cancer (TNBC) has few known therapeutic targets and a poor prognosis. Therefore, new therapeutic targets and strategies against TNBC are required. We found that androgen-induced basic leucine zipper (AIbZIP), also known as cyclic AMP-responsive element-binding protein 3-like protein 4 (CREB3L4), which is encoded by Creb3l4, is highly upregulated in a particular subtype of TNBC, luminal androgen receptor (LAR) subtype. We analyzed the function of AIbZIP through depletion of AIbZIP by siRNA knockdown in LAR subtype TNBC cell lines, MFM223 and MDAMB453. In AIbZIP-depleted cells, the proliferation ratios of cells were greatly suppressed. Moreover, G1-S transition was inhibited in AIbZIP-depleted cells. We comprehensively analyzed the expression levels of proteins that regulate G1-S transition and found that p27 was specifically upregulated in AIbZIP-depleted cells. Furthermore, we identified that this p27 downregulation was caused by protein degradation modulated by the ubiquitin-proteasome system via F-box protein S-phase kinase-associated protein 2 (SKP2) upregulation. Our findings demonstrate that AIbZIP is a novel p27-SKP2 pathway-regulating factor and a potential molecule that contributes to LAR subtype TNBC progression.

IMPLICATIONS

This research shows a new mechanism for the proliferation of LAR subtype TNBC regulated by AIbZIP, that may provide novel insight into the LAR subtype TNBC progression and the molecular mechanisms involved in cell proliferation.

Tumor Cell-Associated IL-1α Affects Breast Cancer Progression and Metastasis in Mice through Manipulation of the Tumor Immune Microenvironment

IL-1α is a dual function cytokine that affects inflammatory and immune responses and plays a pivotal role in cancer. The effects of intracellular IL-1α on the development of triple negative breast cancer (TNBC) in mice were assessed using the CRISPR/Cas9 system to suppress IL-1α expression in 4T1 breast cancer cells. Knockout of IL-1α in 4T1 cells modified expression of multiple genes, including downregulation of cytokines and chemokines involved in the recruitment of tumor-associated pro-inflammatory cells. Orthotopical injection of IL-1α knockout (KO) 4T1 cells into BALB/c mice led to a significant decrease in local tumor growth and lung metastases, compared to injection of wild-type 4T1 (4T1/WT) cells. Neutrophils and myeloid-derived suppressor cells were abundant in tumors developing after injection of 4T1/WT cells, whereas more antigen-presenting cells were observed in the tumor microenvironment after injection of IL-1α KO 4T1 cells. This switch correlated with increased infiltration of CD3+CD8+ and NKp46+cells. Engraftment of IL-1α knockout 4T1 cells into immunodeficient NOD.SCID mice resulted in more rapid tumor growth, with increased lung metastasis in comparison to engraftment of 4T1/WT cells. Our results suggest that tumor-associated IL-1α is involved in TNBC progression in mice by modulating the interplay between immunosuppressive pro-inflammatory cells vs. antigen-presenting and cytotoxic cells.

SBFI26 induces triple-negative breast cancer cells ferroptosis via lipid peroxidation

SBFI26, an inhibitor of FABP5, has been shown to suppress the proliferation and metastasis of tumour cells. However, the underlying mechanism by which SBFI26 induces ferroptosis in breast cancer cells remains largely unknown. Three breast cancer cell lines were treated with SBFI26 and CCK-8 assessed cytotoxicity. Transcriptome was performed on the Illumina platform and verified by qPCR. Western blot evaluated protein levels. Malondialdehyde (MDA), total superoxide dismutase (T-SOD), Fe, glutathione (GSH) and oxidized glutathione (GSSG) were measured. SBFI26 induced cell death time- and dose-dependent, with a more significant inhibitory effect on MDA-MB-231 cells. Fer-1, GSH and Vitamin C attenuated the effects but not erastin. RNA-Seq analysis revealed that SBFI26 treatment significantly enriched differentially expressed genes related to ferroptosis. Furthermore, SBFI26 increased intracellular MDA, iron ion, and GSSG levels while decreasing T-SOD, total glutathione (T-GSH), and GSH levels.SBFI26 dose-dependently up-regulates the expression of HMOX1 and ALOX12 at both gene and protein levels, promoting ferroptosis. Similarly, it significantly increases the expression of SAT1, ALOX5, ALOX15, ALOXE3 and CHAC1 that, promoting ferroptosis while downregulating the NFE2L2 gene and protein that inhibit ferroptosis. SBFI26 leads to cellular accumulation of fatty acids, which triggers excess ferrous ions and subsequent lipid peroxidation for inducing ferroptosis.

PD-L1 (SP142) Expression in Primary and Recurrent/Metastatic Triple-Negative Breast Cancers and Its Clinicopathological Significance

PURPOSE

The programmed death-ligand 1 (PD-L1) SP142 assay identifies patients with triple-negative breast cancer (TNBC) who are most likely to respond to the anti-PD-L1 agent atezolizumab. We aimed to compare PD-L1 (SP142) expression between primary and recurrent/metastatic TNBCs and elucidate the clinicopathological features associated with its expression.

MATERIALS AND METHODS

Primary and recurrent/metastatic TNBCs tested with PD-L1 (SP142) were collected, and clinicopathological information of these cases was obtained through a review of slides and medical records.

RESULTS

PD-L1 (SP142) positivity was observed in 50.9% (144/283) of primary tumors and 37.8% (31/82) of recurrent/metastatic TNBCs with a significant difference. Recurrent or metastatic sites were associated with PD-L1 positivity, with high PD-L1 positivity in the lung, breast, and soft tissues, and low positivity in the bone, skin, liver, and brain. When comparing PD-L1 expression between primary and matched recurrent/metastatic TNBCs using 55 paired samples, 20 cases (36.4%) showed discordance; 10 cases revealed positive conversion, and another 10 cases revealed negative conversion during metastatic progression. In primary TNBCs, PD-L1 expression was associated with a higher histologic grade, lower T category, pushing border, and higher tumor-infiltrating lymphocyte infiltration. In survival analyses, PD-L1 positivity, especially high positivity, was found to be associated with favorable prognosis of patients.

CONCLUSION

PD-L1 (SP142) expression was lower in recurrent/metastatic TNBCs, and substantial cases showed discordance in its expression between primary and recurrent/metastatic sites, suggesting that multiple sites may need to be tested for PD-L1 (SP142) when considering atezolizumab therapy. PD-L1 (SP142)-positive TNBCs seems to be associated with favorable clinical outcomes.

GBP2 enhances paclitaxel sensitivity in triple‑negative breast cancer by promoting autophagy in combination with ATG2 and inhibiting the PI3K/AKT/mTOR pathway

Chemoresistance is a major challenge in treating triple‑negative breast cancer (TNBC); chemotherapy remains the primary approach. The present study aimed to elucidate the role of guanylate‑binding protein 2 (GBP2) in activating autophagy in TNBC and its impact on the sensitivity of TNBC cells to paclitaxel (PTX). Transfection with lentivirus was performed to establish TNBC cell lines with stable, high GBP2 expression. The mRNA and protein levels of GBP2 expression were evaluated utilizing reverse transcription‑quantitative PCR and western blotting, respectively. Autophagy in TNBC cells was evaluated using immunoblotting, transmission electron microscopy and fluorescence microscopy. The PI3K/AKT/mTOR pathway proteins and their phosphorylation were detected by immunoblotting, and fluorescence co‑localization analysis was performed to evaluate the association between GBP2 and autophagy‑related protein 2 (ATG2). BALB/c NUDE mice were subcutaneously injected with GBP2 wild‑type/overexpressing MDA‑MB‑231 cells. Low GBP2 expression was detected in TNBC, which was associated with a poor prognosis. Overexpression of GBP2 suppressed cell growth, and especially enhanced autophagy in TNBC. Forced expression of GBP2 significantly increased the PTX sensitivity of TNBC cells, and the addition of autophagy inhibitors reversed this effect. GBP2 serves as a prognostic marker and exerts a notable inhibitory impact on TNBC. It functions as a critical regulator of activated autophagy by co‑acting with ATG2 and inhibiting the PI3K/AKT/mTOR pathway, which contributes to increasing sensitivity of TNBC cells to PTX. Therefore, GBP2 is a promising therapeutic target for enhancing TNBC treatment.

Oncogenic miR-106b-5p promotes cisplatin resistance in triple-negative breast cancer by targeting GDF11

BACKGROUND

Cytoplatin (CDDP) is a standard treatment for triple-negative breast cancer (TNB), but patient resistance to CDDP limits its efficacy. A growing study confirms that microRNAs (miRNAs) are significantly important in breast cancer, especially TNBC. This research was carried out to examine the function of miR-106b-5p in CDDP resistance of TNBC as well as the downstream mechanism.

METHODS

The miR-106b-5p and growth-differentiation factor 11 (GDF11) expressions in the tissues from TNBC patients and CDDP-treated TNBC cell lines were measured by RT-qPCR. Thereafter, cell proliferation and migration in the presence of CDDP treatment were evaluated via CCK-8 and Transwell assays in the TNBC cells. A xenograft mice model was also established to verify the miR-106b-5p silencing effect on the growth of CDDP resistance TNBC cells in vivo. Luciferase reporter experiments were performed to predict the relationship between miR-106b-5p and GDF11 expression.

RESULTS

The results showed that miR-106b-5p was upregulated in the TNBC tumor cells and TNBC cells treated with CDDP and knockdown of this caused inhibition of the TNBC cell lines' proliferation, migration and suppressed the growth of the TNBC xenografted tumors, in the presence of CDDP treatment. In addition, it was observed that miR-106b-5p can bind to GDF11; as a result in the TNBC tissues and CDDP-treated TNBC cell lines the down-regulation of GDF11 was observed. Moreover, GDF11 silencing promoted CDDP-treated TNBC cell lines' proliferation and migration and reversed the interference effect of miR-106b-5p.

CONCLUSIONS

MiR-106b-5p was upregulated in TNBC and this upregulation may promote CDDP resistance of the TNBC cells by targeting GDF11 and inhibiting its expression.

Identification of a Group of Therapeutic Targets and Prognostic Biomarker for Triple Negative Breast Cancer

INTRODUCTION

Triple-negative breast cancer (TNBC) is a highly heterogeneous disease. Mining differentially expressed genes of TNBC is helpful to explore new therapeutic targets. This study aimed to investigate diagnostic biomarker genes in TNBC compared to normal tissue. Additionally, we explored the functions and prognostic value of these key genes as well as potential targeted drugs that could affect these genes.

METHODS

Differential gene expression analysis was conducted using the R software with data from the Gene Expression Omnibus (GEO) database. Then, the identified differentially expressed genes (DEGs) were used to construct a protein-protein interaction (PPI) network using the Search Tool for the Retrieval of Interacting Genes (STRING) database and Cytoscape software. The mRNA expression levels of key genes were analyzed using the UALCAN database with data from The Cancer Genome Atlas (TCGA). Enrichment and survival analyses were performed using R software. In addition, potential compounds showing sensitivity to key genes were identified by gene set cancer analysis (GSCA).

RESULTS

Compared with normal tissues, a total of 203 DEGs were upregulated in TNBC. These DEGs participated in various biological processes including nuclear division, microtubule binding, cell cycle, and the p53 signaling pathway. Through the PPI network analysis, ten key genes were identified, among which four genes showed significant correlation with poor progression-free interval (PFI) in patients with TNBC. Moreover, the four survival-related genes were found to act as sensitive therapeutic targets.

CONCLUSION

The identified four key genes were considered new biomarkers for diagnosis and prognosis and also potential therapeutic targets for TNBC.

Antibodies toward Na+,HCO3--cotransporter NBCn1/SLC4A7 block net acid extrusion and cause pH-dependent growth inhibition and apoptosis in breast cancer

BACKGROUND

Na+,HCO3--cotransporter NBCn1/Slc4a7 accelerates murine breast carcinogenesis. Lack of specific pharmacological tools previously restricted therapeutic targeting of NBCn1 and identification of NBCn1-dependent functions in human breast cancer.

METHODS

We develop extracellularly-targeted anti-NBCn1 antibodies, screen for functional activity on cells, and evaluate (a) mechanisms of intracellular pH regulation in human primary breast carcinomas, (b) proliferation, cell death, and tumor growth consequences of NBCn1 in triple-negative breast cancer, and (c) association of NBCn1-mediated Na+,HCO3--cotransport with human breast cancer metastasis.

RESULTS

We identify high-affinity (KD ≈ 0.14 nM) anti-NBCn1 antibodies that block human NBCn1-mediated Na+,HCO3--cotransport in cells, without cross-reactivity towards human NBCe1 or murine NBCn1. These anti-NBCn1 antibodies abolish Na+,HCO3--cotransport activity in freshly isolated primary organoids from human breast carcinomas and lower net acid extrusion effectively in primary breast cancer tissue from patients with macrometastases in axillary lymph nodes. Inhibitory anti-NBCn1 antibodies decelerate tumor growth in vivo by ~50% in a patient-derived xenograft model of triple-negative breast cancer and pH-dependently reduce colony formation, cause G2/M-phase cell cycle accumulation, and increase apoptosis of metastatic triple-negative breast cancer cells in vitro.

CONCLUSIONS

Inhibitory anti-NBCn1 antibodies block net acid extrusion in human breast cancer tissue, particularly from patients with disseminated disease, and pH-dependently limit triple-negative breast cancer growth.

Phase II DORA Study of Olaparib with or without Durvalumab as a Chemotherapy-Free Maintenance Strategy in Platinum-Pretreated Advanced Triple-Negative Breast Cancer

PURPOSE

We explored the efficacy of PARP inhibition with or without programmed death ligand-1 (PD-L1) blockade as chemotherapy-free maintenance therapy for advanced triple-negative breast cancer (aTNBC) sensitive to platinum-based chemotherapy.

PATIENTS AND METHODS

In the phase II non-comparative DORA trial (NCT03167619), patients with ongoing stable disease (SD) or complete/partial response (CR/PR) to first- or second-line platinum-based chemotherapy for TNBC (≤10% estrogen/progesterone receptor expression) were randomized 1:1 to receive olaparib 300 mg twice daily with or without durvalumab 1,500 mg on day 1 every 4 weeks. The primary objective was to compare progression-free survival (PFS) versus a historical control of continued platinum-based therapy.

RESULTS

45 patients were randomized (23 to olaparib alone, 22 to the combination; 3 with estrogen/progesterone receptor expression 1%-10%). At 9.8 months' median follow-up, median PFS from randomization was 4.0 [95% confidence interval (CI), 2.6-6.1] months with olaparib and 6.1 (95% CI, 3.7-10.1) months with the combination, both significantly longer than the historical control (P = 0.0023 and P < 0.0001, respectively). Clinical benefit rates (SD ≥24 weeks or CR/PR) were 44% (95% CI, 23%-66%) and 36% (95% CI, 17%-59%) in the monotherapy and combination arms, respectively. Sustained clinical benefit was seen irrespective of germline BRCA mutation or PD-L1 status, but tended to be associated with CR/PR to prior platinum, particularly in the olaparib-alone arm. No new safety signals were reported.

CONCLUSIONS

PFS was longer than expected with both regimens. A patient subset with wild-type BRCA platinum-sensitive aTNBC had durable disease control with chemotherapy-free maintenance.

PRMT1 Sustains De Novo Fatty Acid Synthesis by Methylating PHGDH to Drive Chemoresistance in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) chemoresistance hampers the ability to effectively treat patients. Identification of mechanisms driving chemoresistance can lead to strategies to improve treatment. Here, we revealed that protein arginine methyltransferase-1 (PRMT1) simultaneously methylates D-3-phosphoglycerate dehydrogenase (PHGDH), a critical enzyme in serine synthesis, and the glycolytic enzymes PFKFB3 and PKM2 in TNBC cells. 13C metabolic flux analyses showed that PRMT1-dependent methylation of these three enzymes diverts glucose toward intermediates in the serine-synthesizing and serine/glycine cleavage pathways, thereby accelerating the production of methyl donors in TNBC cells. Mechanistically, PRMT1-dependent methylation of PHGDH at R54 or R20 activated its enzymatic activity by stabilizing 3-phosphoglycerate binding and suppressing polyubiquitination. PRMT1-mediated PHGDH methylation drove chemoresistance independently of glutathione synthesis. Rather, activation of the serine synthesis pathway supplied α-ketoglutarate and citrate to increase palmitate levels through activation of fatty acid synthase (FASN). Increased palmitate induced protein S-palmitoylation of PHGDH and FASN to further enhance fatty acid synthesis in a PRMT1-dependent manner. Loss of PRMT1 or pharmacologic inhibition of FASN or protein S-palmitoyltransferase reversed chemoresistance in TNBC. Furthermore, IHC coupled with imaging MS in clinical TNBC specimens substantiated that PRMT1-mediated methylation of PHGDH, PFKFB3, and PKM2 correlates with chemoresistance and that metabolites required for methylation and fatty acid synthesis are enriched in TNBC. Together, these results suggest that enhanced de novo fatty acid synthesis mediated by coordinated protein arginine methylation and protein S-palmitoylation is a therapeutic target for overcoming chemoresistance in TNBC.

SIGNIFICANCE

PRMT1 promotes chemoresistance in TNBC by methylating metabolic enzymes PFKFB3, PKM2, and PHGDH to augment de novo fatty acid synthesis, indicating that targeting this axis is a potential treatment strategy.

Inhibition of ATM promotes PD-L1 expression by activating JNK/c-Jun/TNF-α signaling axis in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a heterogeneous subtype of breast cancer. Anti-PD-1/PD-L1 treatment for advanced TNBC is still limited to PD-L1-positive patients. Ataxia telangiectasia mutated (ATM) is a switch molecule for homologous recombination and repair. In this study, we found a significant negative correlation between ATM and PD-L1 in 4 TNBC clinical specimens by single-cell RNA sequencing (scRNA-seq), which was confirmed by immunochemical staining in 86 TNBC specimens. We then established ATM knockdown TNBC stable cell lines to perform in vitro studies and animal experiments, proving the negative regulation of PD-L1 by ATM via suppression of tumor necrosis factor-alpha (TNF-α), which was confirmed by cytokine array analysis of TNBC cell line and analysis of clinical specimens. We further found that ATM inhibits TNF-α via inactivating JNK/c-Jun by scRNA-seq, Western blot and luciferase reporter assays. Finally, we identified a negative correlation between changes in phospho-ATMS1981 and PD-L1 levels in TNBC post- and pre-neoadjuvant therapy. This study reveals a novel mechanism by which ATM negatively regulates PD-L1 by downregulating JNK/c-Jun/TNF-α in TNBC, shedding light on the wide application of immune checkpoint blockade therapy for treating multi-line-resistant TNBC.

IRE1 RNase controls CD95-mediated cell death

Signalling by the Unfolded Protein Response (UPR) or by the Death Receptors (DR) are frequently activated towards pro-tumoral outputs in cancer. Herein, we demonstrate that the UPR sensor IRE1 controls the expression of the DR CD95/Fas, and its cell death-inducing ability. Both genetic and pharmacologic blunting of IRE1 activity increased CD95 expression and exacerbated CD95L-induced cell death in glioblastoma (GB) and Triple-Negative Breast Cancer (TNBC) cell lines. In accordance, CD95 mRNA was identified as a target of Regulated IRE1-Dependent Decay of RNA (RIDD). Whilst CD95 expression is elevated in TNBC and GB human tumours exhibiting low RIDD activity, it is surprisingly lower in XBP1s-low human tumour samples. We show that IRE1 RNase inhibition limited CD95 expression and reduced CD95-mediated hepatic toxicity in mice. In addition, overexpression of XBP1s increased CD95 expression and sensitized GB and TNBC cells to CD95L-induced cell death. Overall, these results demonstrate the tight IRE1-mediated control of CD95-dependent cell death in a dual manner through both RIDD and XBP1s, and they identify a novel link between IRE1 and CD95 signalling.

WTAP Mediates NUPR1 Regulation of LCN2 Through m6A Modification to Influence Ferroptosis, Thereby Promoting Breast Cancer Proliferation, Migration and Invasion

Ferroptosis is involved in various pathophysiological diseases, including triple-negative breast cancer (TNBC). Targeting ferroptosis is considered as a novel anti-TNBC strategy. Nevertheless, the regulatory mechanism of ferroptosis during TNBC progression is unclear. Here, the role of WTAP in ferroptosis during TNBC progression  was investigated. The clinicopathological significance of WTAP, NUPR1 and LCN2 was analyzed by Kaplan-Meier method. Cell viability was assessed using MTT assay. Transwell assay was employed to analyze cell migration and invasion. GSH/GSSG and Fe2+ levels in TNBC cells were analyzed using kits. m6A level was examined using m6A dot blot assay. NUPR1 mRNA stability was analyzed using RNA degradation assay. RIP was performed to analyze the interaction between eIF3a and NURP1. Herein, our results revealed that WTAP, NUPR1 and LCN2 expressions were significantly elevated in TNBC. NUPR1 silencing inhibited TNBC cell proliferation, migration and invasion by inducing ferroptosis. NUPR1 positively regulated LCN2 expression in TNBC cells, and LCN2 knockdown induced ferroptosis to suppress TNBC cell malignant behaviors. Our molecular study further revealed that WTAP promoted NUPR1 expression in an m6A-EIF3A mediated manner. And, as expected, WTAP knockdown promoted ferroptosis to suppress TNBC cell malignant behaviors, which were abrogated by NUPR1 overexpression. WTAP upregulated LCN2 by regulation of NUPR1 m6A modification, thereby suppressing ferroptosis to contribute to accelerate TNBC progression. Our study revealed the cancer-promoting effect of WTAP, NUPR1 and LCN2 in TNBC and clarified the relevant mechanism, providing a theoretical basis for developing novel diagnostic and therapeutic strategies for TNBC.

Expression of cell surface zinc transporter LIV1 in triple negative breast cancer is an indicator of poor prognosis and therapy failure

Triple negative breast cancers (TNBC) are an aggressive molecular subtype of breast carcinoma (BC) identified by the lack of receptor expression for estrogen, progesterone, & human epidermal growth factor receptor-2. Lack of tangible drug targets warrants further research in TNBC. LIV1, is a zinc (Zn) transporter known to be overexpressed in few cancer types including BCs. Recently, in the United States of America, FDA approved the use of a new drug targeting LIV1, antibody drug conjugate SGN-LIV1A for treatment of TNBC patients. Though LIV1 also has a role in modulating immune cells by its differential transport of Zn, a correlation between the tumor cell expression of LIV1 and immune cell infiltrations were scantily reported. Further adequate baseline data on LIV1 expression in other populations have not been documented. Our objective was to screen a large Indian cohort of TNBC patient samples for LIV1, categorize the immune cell infiltration using CD4/CD8 expression and correlate the findings with therapy outcomes. Further, we also investigated for LIV1 expression in matched samples of primary & secondary tumors; pre & postchemotherapy in TNBC patients. Results showed an elevated expression of LIV1 in TNBC samples as compared to adjacent normal, the mean Q scores being 183.06 ± 6.39 and 120.78 ± 7.37 (p < 0.0001), respectively. Similarly, LIV1 levels were elevated in secondary tumors than primary & in patient samples postchemotherapy as compared to naïve. In the TNBC cohort, using automated method, cell morphology parameters were computed and analysis showed LIV1 levels were elevated in grade 3 TNBC samples presenting with altered cell morphology parameters namely cell size, cell perimeter, & nucleus size. Thus indicating LIV1 expressing TNBC samples portrayed an aggressive phenotype. Finally, TNBC patients with 3+ staining intensity showed poor survival (4.44 year) as compared to patients with 2+ LIV1 expression (5.47 year), emphasizing that LIV1 expression is a poor prognostic factor in TNBC. In conclusion, the study reports elevated expression of LIV1 in a large Indian TNBC cohort; high expression is a poor prognostic factor and correlated with aggressive disease and indicating the need for LIV1 targeted therapies.

Addressing Residual Disease in HER2-Positive and Triple-Negative Breast Cancer: What Is Next?

PURPOSE OF REVIEW

To summarize the treatment strategies for patients with human epidermal growth factor receptor 2 (HER2)-positive disease and triple-negative breast cancer (TNBC) who have residual disease after preoperative systemic therapy.

RECENT FINDINGS

There has been a shift towards neoadjuvant systemic therapy for selected patients with HER2-positive and TNBC. Assessing the tumor's response to therapy provides prognostic information and allows individualization of the postoperative treatment for these patients based on the tumor response to neoadjuvant therapy. Patients with TNBC with residual disease after neoadjuvant therapy can be treated with pembrolizumab, capecitabine, or olaparib. Those with HER2-positive disease are treated with adjuvant trastuzumab emtansine. The treatment of early breast cancer has evolved significantly, and patient outcomes continue to improve. As better treatments are developed, we will need biomarkers to determine which patients may benefit from certain therapies to continue to improve outcomes by right-sizing treatments and limiting toxicities.

A 14-gene B-cell immune signature in early-stage triple-negative breast cancer (TNBC): a pooled analysis of seven studies

BACKGROUND

Early-stage triple-negative breast cancer (TNBC) displays clinical and biological diversity. From a biological standpoint, immune infiltration plays a crucial role in TNBC prognosis. Currently, there is a lack of genomic tools aiding in treatment decisions for TNBC. This study aims to assess the effectiveness of a B-cell/immunoglobulin signature (IGG) alone, or in combination with tumor burden, in predicting prognosis and treatment response in patients with TNBC.

METHODS

Genomic and clinical data were retrieved from 7 cohorts: SCAN-B (N = 874), BrighTNess (n = 482), CALGB-40603 (n = 389), METABRIC (n = 267), TCGA (n = 118), GSE58812 (n = 107), GSE21653 (n = 67). IGG and a risk score integrating IGG with tumor/nodal staging (IGG-Clin) were assessed for event-free survival (EFS) and overall survival (OS) in each cohort. Random effects model was used to derive pooled effect sizes. Association of IGG with pathological complete response (pCR) was assessed in CALGB-40603 and BrighTNess. Immune significance of IGG was estimated through CIBERSORTx and EcoTyper.

FINDINGS

IGG was associated with improved EFS (pooled HR = 0.77, [95% CI = 0.70-0.85], I2 = 18%) and OS (pooled HR = 0.79, [0.73-0.85], I2 = 0%) across cohorts, and was predictive of pCR in CALGB-40603 (OR 1.25, [1.10-1.50]) and BrighTNess (OR 1.57 [1.25-1.98]). IGG-Clin was predictive of recurrence (pooled HR = 2.11, [1.75-2.55], I2 = 0%) and death (pooled HR = 1.99, 95% [0.84-4.73], I2 = 79%) across cohorts. IGG was associated with adaptive immune response at CIBERSORTx and EcoTyper analysis.

INTERPRETATION

IGG is linked to improved prognosis and pCR in early-stage TNBC. The integration of IGG alongside tumor and nodal staging holds promise as an approach to identify patients benefitting from intensified or de-intensified treatments.

FUNDING

This study received funding from: Associació Beca Marta Santamaria, European Union's Horizon 2020 research and innovation and Marie Skłodowska-Curie Actions programs, Fundación FERO, Fundación CRIS contra el cáncer, Agència de Gestó d'Ajuts Universitaris i de Recerca, Instituto de Salud Carlos III, Fundación Contigo, Asociación Cáncer de Mama Metastásico IV, Breast Cancer Research Foundation, RESCUER, Fundación científica AECC and FSEOM.

Implication of Pre- and Post-radiotherapy ctDNA Dynamics in Patients with Residual Triple-Negative Breast Cancer at Surgery after Neoadjuvant Chemotherapy: Findings from a Prospective Observational Study

PURPOSE

This study aims to determine the association between pre- and postoperative radiotherapy (PORT) circulating tumor DNA (ctDNA) dynamics and oncological outcomes in patients with residual triple-negative breast cancer who underwent surgery after neoadjuvant chemotherapy (NAC).

MATERIALS AND METHODS

Between March 2019 and July 2020, 11 nonmetastatic patients with residual disease who underwent surgery after NAC were prospectively enrolled. In each patient, tumor specimens obtained during surgery and blood samples collected at three time points during PORT (T0: pre-PORT, T1: 3 weeks after PORT, T2: 1 month after PORT) were sequenced, targeting 38 cancer-related genes. Disease-free survival (DFS) was evaluated and the association between DFS and ctDNA dynamics was analyzed.

RESULTS

At T0, ctDNA was detected in three (27.2%) patients. The ctDNA dynamics were as follows: two showed a decreasing ctDNA variant allele frequency (VAF) and reached zero VAF at T2, while one patient exhibited an increasing VAF during PORT and maintained an elevated VAF at T2. After a median follow-up of 48 months, two patients experienced distant metastasis without any locoregional failures. All failures occurred in patients with ctDNA positivity at T0 and a decreased VAF after PORT. The 4-year DFS rates according to the T0 ctDNA status were 67% (positive ctDNA) and 100% (negative ctDNA) (p=0.032).

CONCLUSION

More than a quarter of the patients with residual disease after post-NAC surgery exhibited pre-PORT ctDNA positivity, and ctDNA positivity was associated with poor DFS. For patients with pre-PORT ctDNA positivity, the administration of a more effective systemic treatment should be considered.

Endogenous pAKT activity is associated with response to AKT inhibition alone and in combination with immune checkpoint inhibition in murine models of TNBC

Triple-negative breast cancer (TNBC) is a heterogeneous and challenging-to-treat breast cancer subtype. The clinical introduction of immune checkpoint inhibitors (ICI) for TNBC has had mixed results, and very few patients achieved a durable response. The PI3K/AKT pathway is frequently mutated in breast cancer. Given the important roles of the PI3K pathway in immune and tumor cell signaling, there is an interest in using inhibitors of this pathway to increase the response to ICI. This study sought to determine if AKT inhibition could enhance the response to ICI in murine TNBC models. We further sought to understand underlying mechanisms of response or non-response to AKT inhibition in combination with ICI. Using four murine TNBC-like cell lines and corresponding orthotopic mouse tumor models, we found that hyperactivity of the PI3K pathway, as evidenced by levels of phospho-AKT rather than PI3K pathway mutational status, was associated with response to AKT inhibition alone and in combination with ICI. Additional mutations in other growth regulatory pathways could override the response of PI3K pathway mutant tumors to AKT inhibition. Furthermore, we observed that AKT inhibition enhanced the response to ICI in an already sensitive model. However, AKT inhibition failed to convert ICI-resistant tumors, to responsive tumors. These findings suggest that analysis of both the mutational status and phospho-AKT protein levels may be beneficial in predicting which TNBC tumors will respond to AKT inhibition in combination with ICI.

Basal-epithelial subpopulations underlie and predict chemotherapy resistance in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype, characterized by extensive intratumoral heterogeneity, high metastasis, and chemoresistance, leading to poor clinical outcomes. Despite progress, the mechanistic basis of these aggressive behaviors remains poorly understood. Using single-cell and spatial transcriptome analysis, here we discovered basal epithelial subpopulations located within the stroma that exhibit chemoresistance characteristics. The subpopulations are defined by distinct signature genes that show a frequent gain in copy number and exhibit an activated epithelial-to-mesenchymal transition program. A subset of these genes can accurately predict chemotherapy response and are associated with poor prognosis. Interestingly, among these genes, elevated ITGB1 participates in enhancing intercellular signaling while ACTN1 confers a survival advantage to foster chemoresistance. Furthermore, by subjecting the transcriptional signatures to drug repurposing analysis, we find that chemoresistant tumors may benefit from distinct inhibitors in treatment-naive versus post-NAC patients. These findings shed light on the mechanistic basis of chemoresistance while providing the best-in-class biomarker to predict chemotherapy response and alternate therapeutic avenues for improved management of TNBC patients resistant to chemotherapy.

PFDN4 as a Prognostic Marker Was Associated with Chemotherapy Resistance through CREBP1/AURKA Pathway in Triple-Negative Breast Cancer

Breast cancer is the most common malignancy and its incidence is increasing. It is currently mainly treated by clinical chemotherapy, but chemoresistance remains poorly understood. Prefolded proteins 4 (PFDN4) are molecular chaperone complexes that bind to newly synthesized polypeptides and allow them to fold correctly to stabilize protein formation. This study aimed to investigate the role of PFDN4 in chemotherapy resistance in breast cancer. Our study found that PFDN4 was highly expressed in breast cancer compared to normal tissues and was statistically significantly associated with stage, nodal status, subclasses (luminal, HER2 positive and triple negative), triple-negative subtype and disease-specific survival by TCGA database analysis. CRISPR knockout of PFDN4 inhibited the growth of 89% of breast cancer cell lines, and the triple-negative cell line exhibited a stronger inhibitory effect than the non-triple-negative cell line. High PFDN4 expression was associated with poor overall survival in chemotherapy and resistance to doxorubicin and paclitaxel through the CREBP1/AURKA pathway in the triple-negative MDAMB231 cell line. This study provides insightful evidence for the value of PFDN4 in poor prognosis and chemotherapy resistance in breast cancer patients.

MARCH2, a Novel Oncogene-regulated SNAIL E3 Ligase, Suppresses Triple-negative Breast Cancer Metastases

Epithelial-mesenchymal transition (EMT) in cancer promotes metastasis and chemotherapy resistance. A subset of triple-negative breast cancer (TNBC) exhibits a mesenchymal gene signature that is associated with poor patient outcomes. We previously identified PTK6 tyrosine kinase as an oncogenic driver of EMT in a subset of TNBC. PTK6 induces EMT by stabilizing SNAIL, a key EMT-initiating transcriptional factor. Inhibition of PTK6 activity reverses mesenchymal features of TNBC cells and suppresses their metastases by promoting SNAIL degradation via a novel mechanism. In the current study, we identify membrane-associated RING-CH2 (MARCH2) as a novel PTK6-regulated E3 ligase that promotes the ubiquitination and degradation of SNAIL protein. The MARCH2 RING domain is critical for SNAIL ubiquitination and subsequent degradation. PTK6 inhibition promotes the interaction of MARCH2 with SNAIL. Overexpression of MARCH2 exhibits tumor suppressive properties and phenocopies the effects of SNAIL downregulation and PTK6 inhibition in TNBC cells, such as inhibition of migration, anoikis resistance, and metastasis. Consistent with this, higher levels of MARCH2 expression in breast and other cancers are associated with better prognosis. We have identified MARCH2 as a novel SNAIL E3 ligase that regulates EMT and metastases of mesenchymal TNBC.

SIGNIFICANCE

EMT is a process directly linked to drug resistance and metastasis of cancer cells. We identified MARCH2 as a novel regulator of SNAIL, a key EMT driver, that promotes SNAIL ubiquitination and degradation in TNBC cells. MARCH2 is oncogene regulated and inhibits growth and metastasis of TNBC. These insights could contribute to novel strategies to therapeutically target TNBC.

Community cohesion looseness in gene networks reveals individualized drug targets and resistance

Community cohesion plays a critical role in the determination of an individual's health in social science. Intriguingly, a community structure of gene networks indicates that the concept of community cohesion could be applied between the genes as well to overcome the limitations of single gene-based biomarkers for precision oncology. Here, we develop community cohesion scores which precisely quantify the community ability to retain the interactions between the genes and their cellular functions in each individualized gene network. Using breast cancer as a proof-of-concept study, we measure the community cohesion score profiles of 950 case samples and predict the individualized therapeutic targets in 2-fold. First, we prioritize them by finding druggable genes present in the community with the most and relatively decreased scores in each individual. Then, we pinpoint more individualized therapeutic targets by discovering the genes which greatly contribute to the community cohesion looseness in each individualized gene network. Compared with the previous approaches, the community cohesion scores show at least four times higher performance in predicting effective individualized chemotherapy targets based on drug sensitivity data. Furthermore, the community cohesion scores successfully discover the known breast cancer subtypes and we suggest new targeted therapy targets for triple negative breast cancer (e.g. KIT and GABRP). Lastly, we demonstrate that the community cohesion scores can predict tamoxifen responses in ER+ breast cancer and suggest potential combination therapies (e.g. NAMPT and RXRA inhibitors) to reduce endocrine therapy resistance based on individualized characteristics. Our method opens new perspectives for the biomarker development in precision oncology.

Context-Responsive Nanoparticle Derived from Synthetic Zwitterionic Ionizable Phospholipids in Targeted CRISPR/Cas9 Therapy for Basal-like Breast Cancer

The majority of triple negative breast cancers (TNBCs) are basal-like breast cancers (BLBCs), which tend to be more aggressive, proliferate rapidly, and have poor clinical outcomes. A key prognostic biomarker and regulator of BLBC is the Forkhead box C1 (FOXC1) transcription factor. However, because of its functional placement inside the cell nucleus and its structural similarity with other related proteins, targeting FOXC1 for therapeutic benefit, particularly for BLBC, continues to be difficult. We envision targeted nonviral delivery of CRISPR/Cas9 plasmid toward the efficacious knockdown of FOXC1. Keeping in mind the challenges associated with the use of CRISPR/Cas9 in vivo, including off-targeting modifications, and effective release of the cargo, a nanoparticle with context responsive properties can be designed for efficient targeted delivery of CRISPR/Cas9 plasmid. Consequently, we have designed, synthesized, and characterized a zwitterionic amino phospholipid-derived transfecting nanoparticle for delivery of CRISPR/Cas9. The construct becomes positively charged only at low pH, which encourages membrane instability and makes it easier for nanoparticles to exit endosomes. This has enabled effective in vitro and in vivo downregulation of protein expression and genome editing. Following this, we have used EpCAM aptamer to make the system targeted toward BLBC cell lines and to reduce its off-target toxicity. The in vivo efficacy, biodistribution, preliminary pharmacokinetics, and biosafety of the optimized targeted CRISPR nanoplatform is then validated in a rodent xenograft model. Overall, we have attempted to knockout the proto-oncogenic FOXC1 expression in BLBC cases by efficient delivery of CRISPR effectors via a context-responsive nanoparticle delivery system derived from a designer lipid derivative. We believe that the nonviral approach for in vitro and in vivo delivery of CRISPR/Cas9 targeted toward FOXC1, studied herein, will greatly emphasize the therapeutic regimen for BLBC.

Activation of ERβ hijacks the splicing machinery to trigger R-loop formation in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a subtype of breast cancer with aggressive behavior and poor prognosis. Current therapeutic options available for TNBC patients are primarily chemotherapy. With our evolving understanding of this disease, novel targeted therapies, including poly ADP-ribose polymerase (PARP) inhibitors, antibody-drug conjugates, and immune-checkpoint inhibitors, have been developed for clinical use. Previous reports have demonstrated the essential role of estrogen receptor β (ERβ) in TNBC, but the detailed molecular mechanisms downstream ERβ activation in TNBC are still far from elucidated. In this study, we demonstrated that a specific ERβ agonist, LY500307, potently induces R-loop formation and DNA damage in TNBC cells. Subsequent interactome experiments indicated that the residues 151 to 165 of U2 small nuclear RNA auxiliary factor 1 (U2AF1) and the Trp439 and Lys443 of ERβ were critical for the binding between U2AF1 and ERβ. Combined RNA sequencing and ribosome sequencing analysis demonstrated that U2AF1-regulated downstream RNA splicing of 5-oxoprolinase (OPLAH) could affect its enzymatic activity and is essential for ERβ-induced R-loop formation and DNA damage. In clinical samples including 115 patients from The Cancer Genome Atlas (TCGA) and 32 patients from an in-house cohort, we found a close correlation in the expression of ESR2 and U2AF1 in TNBC patients. Collectively, our study has unraveled the molecular mechanisms that explain the therapeutic effects of ERβ activation in TNBC, which provides rationale for ERβ activation-based single or combined therapy for patients with TNBC.

LINC00115 promotes chemoresistant breast cancer stem-like cell stemness and metastasis through SETDB1/PLK3/HIF1α signaling

BACKGROUND

Cancer stem-like cell is a key barrier for therapeutic resistance and metastasis in various cancers, including breast cancer, yet the underlying mechanisms are still elusive. Through a genome-wide lncRNA expression profiling, we identified that LINC00115 is robustly upregulated in chemoresistant breast cancer stem-like cells (BCSCs).

METHODS

LncRNA microarray assay was performed to document abundance changes of lncRNAs in paclitaxel (PTX)-resistant MDA-MB-231 BCSC (ALDH+) and non-BCSC (ALDH-). RNA pull-down and RNA immunoprecipitation (RIP) assays were performed to determine the binding proteins of LINC00115. The clinical significance of the LINC00115 pathway was examined in TNBC metastatic lymph node tissues. The biological function of LINC00115 was investigated through gain- and loss-of-function studies. The molecular mechanism was explored through RNA sequencing, mass spectrometry, and the CRISPR/Cas9-knockout system. The therapeutic potential of LINC00115 was examined through xenograft animal models.

RESULTS

LINC00115 functions as a scaffold lncRNA to link SETDB1 and PLK3, leading to enhanced SETDB1 methylation of PLK3 at both K106 and K200 in drug-resistant BCSC. PLK3 methylation decreases PLK3 phosphorylation of HIF1α and thereby increases HIF1α stability. HIF1α, in turn, upregulates ALKBH5 to reduce m6A modification of LINC00115, resulting in attenuated degradation of YTHDF2-dependent m6A-modified RNA and enhanced LINC00115 stability. Thus, this positive feedback loop provokes BCSC phenotypes and enhances chemoresistance and metastasis in triple-negative breast cancer. SETDB1 inhibitor TTD-IN with LINC00115 ASO sensitizes PTX-resistant cell response to chemotherapy in a xenograft animal model. Correlative expression of LINC00115, methylation PLK3, SETDB1, and HIF1α are prognostic for clinical triple-negative breast cancers.

CONCLUSIONS

Our findings uncover LINC00115 as a critical regulator of BCSC and highlight targeting LINC00115 and SETDB1 as a potential therapeutic strategy for chemotherapeutic resistant breast cancer.

Germline testing of BRCA1, BRCA2, PALB2 and CHEK2 c.1100delC in 1514 triple negative familial and isolated breast cancers from a single centre, with extended testing of ATM, RAD51C and RAD51D in over 400

BACKGROUND

The identification of germline pathogenic gene variants (PGVs) in triple negative breast cancer (TNBC) is important to inform further primary cancer risk reduction and TNBC treatment strategies. We therefore investigated the contribution of breast cancer associated PGVs to familial and isolated invasive TNBC.

METHODS

Outcomes of germline BRCA1, BRCA2 and CHEK2_c.1100delC testing were recorded in 1514 women (743-isolated, 771-familial), and for PALB2 in 846 women (541-isolated, 305-familial), with TNBC and smaller numbers for additional genes. Breast cancer free controls were identified from Predicting Risk Of Cancer At Screening and BRIDGES (Breast cancer RIsk after Diagnostic GEne Sequencing) studies.

RESULTS

BRCA1_PGVs were detected in 52 isolated (7.0%) and 195 (25.3%) familial cases (isolated-OR=58.9, 95% CI: 16.6 to 247.0), BRCA2_PGVs in 21 (2.8%) isolated and 67 (8.7%) familial cases (isolated-OR=5.0, 95% CI: 2.3 to 11.2), PALB2_PGVs in 9 (1.7%) isolated and 12 (3.9%) familial cases (isolated-OR=8.8, 95% CI: 2.5 to 30.4) and CHEK2_c.1100delC in 0 isolated and 3 (0.45%) familial cases (isolated-OR=0.0, 95% CI: 0.00 to 2.11). BRCA1_PGV detection rate was >10% for all familial TNBC age groups and significantly higher for younger diagnoses (familial: <50 years, n=165/538 (30.7%); ≥50 years, n=30/233 (12.9%); p<0.0001). Women with a G3_TNBC were more likely to have a BRCA1_PGV as compared with a BRCA2 or PALB2_PGV (p<0.0001). 0/743 isolated TNBC had the CHEK2_c.1100delC PGV and 0/305 any ATM_PGV, but 2/240 (0.83%) had a RAD51D_PGV.

CONCLUSION

PGVs in BRCA1 are associated with G3_TNBCs. Familial TNBCs and isolated TNBCs <30 years have a >10% likelihood of a PGV in BRCA1. BRCA1_PGVs are associated with younger age of familial TNBC. There was no evidence for any increased risk of TNBC with CHEK2 or ATM PGVs.

Comparison of neoadjuvant chemotherapy response and prognosis between HR-low/HER2-negative BC and TNBC: an exploratory real-world multicentre cohort study

Objective

Hormone receptor (HR)-low/HER2-negative breast cancers (BCs) are more likely to be basal-like BCs, with similar molecular features and gene expression profiles to HR-negative (estrogen receptor <1% or negative and progesterone receptor <1% or negative) BCs. Recently, with the clinical application of adjuvant intensive therapy for triple-negative breast cancer (TNBC), the prognosis of TNBC patients without pathological complete response (pCR) has significantly improved. Therefore, it is necessary to reanalyse the prognostic characteristics of clinically high-risk HR-low/HER2-negative BC.

Methods

According to the inclusion and exclusion standards, 288 patients with HR-low/HER2-negative BC and TNBC who received NAC and were followed up between 2015 and 2022 at three breast centres in Hunan Province, China, were enrolled. Inverse probability of treatment weighting (IPTW) was utilized to mitigate imbalances in baseline characteristics between the HR-low/HER2-negative BC group and TNBC group regarding event-free survival (EFS) and overall survival (OS). The primary clinical endpoints were pCR and EFS, while the secondary endpoints included OS, objective response rate (ORR), and clinical benefit rate (CBR).

Results

The pCR rate (27.1% vs. 28.0%, P = 1.000), ORR rate (76.9% vs. 78.3%, P = 0.827) and CBR rate (89.7% vs. 96.5%, P = 0.113) after NAC were similar between the HR-low/HER2-negative BC and the TNBC group. EFS in patients with non-pCR from the 2 groups was significantly inferior in comparison to patients with pCR (P = 0.001), and the 3-year EFS was 94.74% (95% CI = 85.21% to 100.00%) and 57.39% (95% CI =43.81% to 75.19%) in patients with pCR and non-pCR from the HR-low/HER2-negative BC group, respectively, and 89.70% (95% CI = 82.20% to 97.90%) and 69.73% (95% CI = 62.51% to 77.77%) in the TNBC patients with pCR and non-pCR, respectively.

Conclusions

In the real world, the therapeutic effects of NAC for HR-low/HER2-negative BCs and TNBCs were similar. EFS of patients with non-pCR in the HR-low/HER2-negative BC group was inferior to that of the TNBC group with non-pCR, suggesting that it is necessary to explore new adjuvant intensive therapy strategies for these patients.

Dysregulated Ribosome Biogenesis Is a Targetable Vulnerability in Triple-Negative Breast Cancer: MRPS27 as a Key Mediator of the Stemness-inhibitory Effect of Lovastatin

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with limited effective therapeutic options readily available. We have previously demonstrated that lovastatin, an FDA-approved lipid-lowering drug, selectively inhibits the stemness properties of TNBC. However, the intracellular targets of lovastatin in TNBC remain largely unknown. Here, we unexpectedly uncovered ribosome biogenesis as the predominant pathway targeted by lovastatin in TNBC. Lovastatin induced the translocation of ribosome biogenesis-related proteins including nucleophosmin (NPM), nucleolar and coiled-body phosphoprotein 1 (NOLC1), and the ribosomal protein RPL3. Lovastatin also suppressed the transcript levels of rRNAs and increased the nuclear protein level and transcriptional activity of p53, a master mediator of nucleolar stress. A prognostic model generated from 10 ribosome biogenesis-related genes showed outstanding performance in predicting the survival of TNBC patients. Mitochondrial ribosomal protein S27 (MRPS27), the top-ranked risky model gene, was highly expressed and correlated with tumor stage and lymph node involvement in TNBC. Mechanistically, MRPS27 knockdown inhibited the stemness properties and the malignant phenotypes of TNBC. Overexpression of MRPS27 attenuated the stemness-inhibitory effect of lovastatin in TNBC cells. Our findings reveal that dysregulated ribosome biogenesis is a targetable vulnerability and targeting MRPS27 could be a novel therapeutic strategy for TNBC patients.

The Molecular Mechanisms behind Advanced Breast Cancer Metabolism: Warburg Effect, OXPHOS, and Calcium

Altered metabolism represents a fundamental difference between cancer cells and normal cells. Cancer cells have a unique ability to reprogram their metabolism by deviating their reliance from primarily oxidative phosphorylation (OXPHOS) to glycolysis, in order to support their survival. This metabolic phenotype is referred to as the "Warburg effect" and is associated with an increase in glucose uptake, and a diversion of glycolytic intermediates to alternative pathways that support anabolic processes. These processes include synthesis of nucleic acids, lipids, and proteins, necessary for the rapidly dividing cancer cells, sustaining their growth, proliferation, and capacity for successful metastasis. Triple-negative breast cancer (TNBC) is one of the most aggressive subtypes of breast cancer, with the poorest patient outcome due to its high rate of metastasis. TNBC is characterized by elevated glycolysis and in certain instances, low OXPHOS. This metabolic dysregulation is linked to chemotherapeutic resistance in TNBC research models and patient samples. There is more than a single mechanism by which this metabolic switch occurs and here, we review the current knowledge of relevant molecular mechanisms involved in advanced breast cancer metabolism, focusing on TNBC. These mechanisms include the Warburg effect, glycolytic adaptations, microRNA regulation, mitochondrial involvement, mitochondrial calcium signaling, and a more recent player in metabolic regulation, JAK/STAT signaling. In addition, we explore some of the drugs and compounds targeting cancer metabolic reprogramming. Research on these mechanisms is highly promising and could ultimately offer new opportunities for the development of innovative therapies to treat advanced breast cancer characterized by dysregulated metabolism.

UCHL1 contributes to insensitivity to endocrine therapy in triple-negative breast cancer by deubiquitinating and stabilizing KLF5

BACKGROUND

Ubiquitin carboxyl-terminal hydrolase L1 (UCHL1) is a deubiquitinating enzyme that regulates ERα expression in triple-negative cancer (TNBC). This study aimed to explore the deubiquitination substrates of UCHL1 related to endocrine therapeutic responses and the mechanisms of UCHL1 dysregulation in TNBC.

METHODS

Bioinformatics analysis was conducted using online open databases. TNBC representative MDA-MB-468 and SUM149 cells were used for in vitro and in-vivo studies. Co-immunoprecipitation was used to explore the interaction between UCHL1 and KLF5 and UCHL1-mediated KIF5 deubiquitination. CCK-8, colony formation and animal studies were performed to assess endocrine therapy responses. The regulatory effect of TET1/3 on UCHL1 promoter methylation and transcription was performed by Bisulfite sequencing PCR and ChIP-qPCR.

RESULTS

UCHL1 interacts with KLF5 and stabilizes KLF5 by reducing its polyubiquitination and proteasomal degradation. The UCHL1-KLF5 axis collaboratively upregulates EGFR expression while downregulating ESR1 expression at both mRNA and protein levels in TNBC. UCHL1 knockdown slows the proliferation of TNBC cells and sensitizes the tumor cells to Tamoxifen and Fulvestrant. KLF5 overexpression partially reverses these trends. Both TET1 and TET3 can bind to the UCHL1 promoter region, reducing methylation of associated CpG sites and enhancing UCHL1 transcription in TNBC cell lines. Additionally, TET1 and TET3 elevates KLF5 protein level in a UCHL1-dependent manner.

CONCLUSION

UCHL1 plays a pivotal role in TNBC by deubiquitinating and stabilizing KLF5, contributing to endocrine therapy resistance. TET1 and TET3 promote UCHL1 transcription through promoter demethylation and maintain KLF5 protein level in a UCHL1-dependent manner, implying their potential as therapeutic targets in TNBC.