Subtyping of triple-negative breast cancers: its prognostication and implications in diagnosis of breast origin

BACKGROUND

Triple-negative breast cancer (TNBC) subtyping by gene profiling has provided valuable clinical information. Here, we aimed to evaluate the relevance of TNBC subtyping using immunohistochemistry (IHC), which could be a more clinically practical approach, for prognostication and applications in patient management.

METHODS

A total of 123 TNBC cases were classified using androgen receptor (AR), CD8, Forkhead box C1 protein (FOXC1), and doublecortin-like kinase 1 (DCLK1) into luminal androgen receptor (LAR), basal-like immunosuppressive (BLIS), mesenchymal-like (MES), and immunomodulatory (IM) subtypes. The IM cases were further divided into the IM-excluded and IM-inflamed categories by CD8 spatial distribution. Their clinicopathological and biomarker profiles and prognoses were evaluated.

RESULTS

LAR (28.6%) and MES (11.2%) were the most and least frequent subtypes. The IHC-TNBC subtypes demonstrated distinct clinicopathological features and biomarker profiles, corresponding to the reported features in gene profiling studies. IM-inflamed subtype had the best outcome, while BLIS had a significantly poorer survival. Differential breast-specific marker expressions were found. Trichorhinophalangeal syndrome type 1 (TRPS1) was more sensitive for IM-inflamed and BLIS, GATA-binding protein 3 (GATA3) for IM-excluded and MES, and gross cystic disease fluid protein 15 (GCDFP15) for LAR subtypes.

CONCLUSIONS

Our findings demonstrated the feasibility of IHC surrogates to stratify TNBC subtypes with distinct features and prognoses. The IM subtype can be refined by its CD8 spatial pattern. Breast-specific marker expression varied among the subtypes. Marker selection should be tailored accordingly.

Vitamin D Levels in Newly Diagnosed Breast Cancer Patients according to Tumor Sub-Types

Vitamin D is an important regulator of bone health. In addition, as a ligand for a nuclear receptor expressed in breast cancer cells, vitamin D exerts neoplasia modulating effects in breast cancer. However, despite extensive investigations, associations of vitamin D levels with breast cancer patient characteristics and disease sub-types are conflicting. A retrospective review of medical records of consecutive breast cancer patients treated and followed in a single cancer center was undertaken. All patients with 25-hydroxyvitamin D (25-OHD, the circulating form of vitamin D) measurements available within 3 months of their diagnosis and before the start of any systemic treatment were included. Characteristics of patients and tumors with sufficient levels of 25-OHD were compared with those of patients with 25-OHD insufficiency. Two hundred ninety-two patients were included in the study. Almost two-thirds of the patients were 25-OHD insufficient, defined as having 25-OHD levels below 75 nmol/L. Compared with the group of patients who were 25-OHD sufficient, patients with 25-OHD insufficiency were younger and more often obese. Tumors of patients with 25-OHD insufficiency were more often ductal, of higher grade, and ER negative. 25-OHD insufficiency is prevalent in breast cancer patients and even more prevalent in younger and obese patients. 25-OHD insufficiency is associated with cancers that have aggressive characteristics, including higher grade and ER negativity.

Leveraging the Dynamic Immune Environment Triad in Patients with Breast Cancer: Tumour, Lymph Node, and Peripheral Blood

During the anti-tumour response to breast cancer, the primary tumour, the peripheral blood, and the lymph nodes each play unique roles. Immunological features at each site reveal evidence of continuous immune cross-talk between them before, during and after treatment. As such, immune responses to breast cancer are found to be highly dynamic and truly systemic, integrating three distinct immune sites, complex cell-migration highways, as well as the temporal dimension of disease progression and treatment. In this review, we provide a connective summary of the dynamic immune environment triad of breast cancer. It is critical that future studies seek to establish dynamic immune profiles, constituting multiple sites, that capture the systemic immune response to breast cancer and define patient-selection parameters resulting in more significant overall responses and survival rates for breast cancer patients.

CISH Expression Is Associated with Metastasis-Free Interval in Triple-Negative Breast Cancer and Refines the Prognostic Value of PDL1 Expression

Simple Summary

CISH is a member of the suppressors of cytokine signaling (SOCS) family of proteins and an important negative regulator of T cells and NK cells signaling and function. In this study, analyzing 1936 triple-negative breast cancer (TNBC) clinical samples, we highlighted correlation between CISH expression and tumor features. We demonstrated that high CISH upregulation was associated with better metastasis-free interval, especially when PDL1 was also upregulated. Moreover, we showed that the two-gene model (CISH and PDL1) provided more prognostic information than each gene alone and maintained its prognostic value in multivariate analysis. Such prognostic synergy between CISH and PDL1 expressions might reinforce the therapeutic relevance of co-targeting TNBC by a combination of CISH inhibition with an immune checkpoint inhibitor blocking the PD1/PDL1 axis.

Abstract

Strategies are being explored to increase the efficiency of immune checkpoint inhibitors (ICIs) targeting PD1/PDL1 in triple-negative breast cancer (TNBC), including combination with therapies inhibiting intracellular immune checkpoints such as CISH (Cytokine-induced SH2 protein). Correlation between CISH expression and TNBC features is unknown. We retrospectively analyzed CISH expression in 1936 clinical TNBC samples and searched for correlations with clinical variables, including metastasis-free interval (MFI). Among TNBCs, 44% were identified as “CISH-up” and 56% “CISH-down”. High expression was associated with pathological axillary lymph node involvement, more adjuvant chemotherapy, and Lehmann’s immunomodulatory and luminal AR subtypes. The “CISH-up” class showed longer 5-year MFI (72%) than the “CISH-down” class (60%; p = 2.8 × 10⁻²). CISH upregulation was associated with activation of IFNα and IFNγ pathways, antitumor cytotoxic immune response, and signatures predictive for ICI response. When CISH and PDL1 were upregulated together, the 5-year MFI was 81% versus 52% when not upregulated (p = 6.21 × 10⁻⁶). The two-gene model provided more prognostic information than each gene alone and maintained its prognostic value in multivariate analysis. CISH expression is associated with longer MFI in TNBC and refines the prognostic value of PDL1 expression. Such observation might reinforce the therapeutic relevance of combining CISH inhibition with an anti-PD1/PDL1 ICI.

CmP Signaling Network Leads to Identification of Prognostic Biomarkers for Triple-Negative Breast Cancer in Caucasian Women

Objective: Triple-negative breast cancer (TNBC) constitutes ∼15% of all diagnosed invasive breast cancer cases with limited options for treatment since immunotherapies that target ER, PR, and HER2 receptors are ineffective. Progesterone (PRG) can induce its effects through either classic, nonclassic, or combined responses by binding to classic nuclear PRG receptors (nPRs) or nonclassic membrane PRG receptors (mPRs). Under PRG-induced actions, we previously demonstrated that the CCM signaling complex (CSC) can couple both nPRs and mPRs into a CmPn signaling network, which plays an important role during nPR(+) breast cancer tumorigenesis. We recently defined the novel CmP signaling network in African American women (AAW)-derived TNBC cells, which overlapped with our previously defined CmPn network in nPR(+) breast cancer cells. Methods: Under mPR-specific steroid actions, we measured alterations to key tumorigenic pathways in Caucasian American women (CAW)- derived TNBC cells, with RNAseq/proteomic and systems biology approaches. Exemption from ethics approval from IRB: This study only utilized cultured NBC cell lines with publicly available TNBC clinical data sets. Results: Our results demonstrated that TNBCs in CAW share similar altered signaling pathways, as TNBCs in AAW, under mPR-specific steroid actions, demonstrating the overall aggressive nature of TNBCs, regardless of racial differences. Furthermore, in this report, we have deconvoluted the CmP signalosome, using systems biology approaches and CAW-TNBC clinical data, to identify 21 new CAW-TNBC-specific prognostic biomarkers that reinforce the definitive role of CSC and mPR signaling during CAW-TNBC tumorigenesis. Conclusion: This new set of potential prognostic biomarkers may revolutionize molecular mechanisms and currently known concepts of tumorigenesis in CAW-TNBCs, leading to hopeful new therapeutic strategies.

Prospects of Immunotherapy for Triple-Negative Breast Cancer

In the classification and typing of breast cancer, triple-negative breast cancer (TNBC) is one type of refractory breast cancer, while chemotherapy stays in the traditional treatment methods. However, the impact of chemotherapy is short-lived and may lead to recurrence due to incomplete killing of tumor cells. The occurrence, development, and relapse of breast cancer are relevant to T cell dysfunction, multiplied expression of related immune checkpoint molecules (ICIs) such as programmed death receptor 1 (PD-1), programmed cell death 1 ligand 1 (PD-L1), and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) produce immunosuppressive effect. Immunotherapy (namely, immune checkpoint inhibitors, adoptive cellular immunotherapy, CAR-T immunotherapy and some potential treatments) provides new hope in TNBC. This review focuses on the new immune strategies of TNBC patients.

Targeted EV to Deliver Chemotherapy to Treat Triple-Negative Breast Cancers

Triple-negative breast cancers (TNBCs) are heterogeneous and metastatic, and targeted therapy is highly needed for TNBC treatment. Recent studies showed that extracellular vesicles (EV) have great potential to deliver therapies to treat cancers. This study aimed to develop and evaluate a natural compound, verrucarin A (Ver-A), delivered by targeted EV, to treat TNBC. First, the surface expression of epidermal growth factor receptor (EGFR) and CD47 were confirmed with immunohistochemistry (IHC) staining of patient tissue microarray, flow cytometry and Western blotting. EVs were isolated from HEK 293F culture and surface tagged with anti-EGFR/CD47 mAbs to construct mAb-EV. The flow cytometry, confocal imaging and live-animal In Vivo Imaging System (IVIS) demonstrated that mAb-EV could effectively target TNBC and deliver the drug. The drug Ver-A, with dosage-dependent high cytotoxicity to TNBC cells, was packed in mAb-EV. The anti-TNBC efficacy study showed that Ver-A blocked tumor growth in both 4T1 xenografted immunocompetent mouse models and TNBC patient-derived xenograft models with minimal side effects. This study demonstrated that the targeted mAb-EV-Ver-A had great potential to treat TNBCs.

Radiotherapy in the Management of Non-Metastatic Inflammatory Breast Cancers: A Retrospective Observational Study

(1) Background: Inflammatory breast cancers (IBC) are characterized by a poor prognosis. This retrospective study aims to describe the clinical outcomes of non-metastatic IBC patients treated with a multidisciplinary approach with neo-adjuvant chemotherapy, surgery, and radiotherapy. (2) Methods: This single-center retrospective study included all women patients diagnosed with non-metastatic IBC between January 2010 and January 2018 at the Institut Curie (Paris, France) and treated with neoadjuvant chemotherapy, surgery, and radiotherapy. Overall survival (OS), disease-free survival (DFS), and locoregional free survival (LRRFS) were calculated from the time of diagnosis. Prognostic factors for patient survival were analyzed based on univariate and multivariate regressions. (3) Results: We identified 113 patients with a median age of 51 years. 79.7% had node-positive tumors; triple-negative breast cancers (TNBC) represented 34.6% of the cases. A large majority of patients (91.2%) received adjuvant post-mastectomy while ten patients (8.8%) received preoperative radiotherapy. Non-pathological complete response (non-pCR) was observed in 67.3% of patients. Radiotherapy delivered a median dose of 50 Gy to the breast or the chest wall in 25 fractions. With a median follow-up of 54 months, 5-year OS, DFS and LRRFS were 78% (CI: 70.1-86.8%), 68.1% (59.6-77.7%), and 85.2% (78.4-92.7%), respectively. In multivariate analysis, non-pCR was an adverse prognosis factor for OS, DFS, and LRRFS; pre-operative radiotherapy was an adverse prognosis factor for OS and DFS. Radiation-related adverse events were limited to acute skin toxicity (22% of Grade 2 and 2% of grade 3 dermatitis); no late radiation-induced toxicity was reported. (4) Conclusions: High locoregional control could be achieved with multidisciplinary management of non-metastatic IBC, suggesting the anti-tumor efficacy of radiotherapy in this rare but pejorative clinicopathological presentation. While comparing favorably with historical cohorts, OS and DFS could be potentially improved in the future with the use of new systemic treatments, such as PARP-inhibitors or immunotherapy.

Anti-CD47 Monoclonal Antibody-Drug Conjugate: A Targeted Therapy to Treat Triple-Negative Breast Cancers

Triple-negative breast cancers (TNBCs) are frequently recurrent due to the development of drug resistance post chemotherapy. Both the existing literature and our study found that surface receptor CD47 (cluster of differentiation 47) was upregulated in chemotherapy-treated TNBC cells. The goal of this study was to develop a monoclonal antibody (mAb)-based targeting strategy to treat TNBC after standard treatment. Specifically, a new mAb that targets the extracellular domain of receptor CD47 was developed using hybridoma technology and produced in fed-batch culture. Flow cytometry, confocal microscopy, and in vivo imaging system (IVIS) showed that the anti-CD47 mAb effectively targeted human and mouse TNBC cells and xenograft models with high specificity. The antibody-drug conjugate (ADC) carrying mertansine was constructed and demonstrated higher potency with reduced IC₅₀ in TNBC cells than did the free drug and significantly inhibited tumor growth post gemcitabine treatment in MDA-MB-231 xenograft NSG model. Finally, whole blood analysis indicated that the anti-CD47 mAb had no general immune toxicity, flow cytometry analysis of lymph nodes revealed an increase of CD69⁺ NK, CD11c⁺ DC, and CD4⁺ T cells, and IHC staining showed tumoral infiltration of macrophage in the 4T1 xenograft BALB/cJ model. This study demonstrated that targeting CD47 with ADC has great potential to treat TNBCs as a targeted therapy.

Triple-Negative Breast Cancer Comparison With Canine Mammary Tumors From Light Microscopy to Molecular Pathology

Many similar characteristics in human and dog cancers including, spontaneous development, clinical presentation, tumor heterogeneity, disease progression, and response to standard therapies have promoted the approval of this comparative model as an alternative to mice. Breast cancer represents the second most frequent neoplasm in humans after lung cancer. Triple-negative breast cancers (TNBC) constitute around 15% of all cases of breast cancer and do not express estrogen receptor (ER), progesterone receptor (PR), and do not overexpress human epidermal growth factor receptor 2 (HER2). As a result, they do not benefit from hormonal or trastuzumab-based therapy. Patients with TNBC have worse overall survival than patients with non-TNBC. Lehmann and collaborators described six different molecular subtypes of TNBC which further demonstrated its transcriptional heterogeneity. This six TNBC subtype classification has therapeutic implications. Breast cancer is the second most frequent neoplasm in sexually intact female dogs after skin cancer. Canine mammary tumors are a naturally occurring heterogeneous group of cancers that have several features in common with human breast cancer (HBC). These similarities include etiology, signaling pathway activation, and histological classification. Molecularly CMTs are more like TNBCs, and therefore dogs are powerful spontaneous models of cancer to test new therapeutic approaches, particularly for human TNBCs. More malignant tumors of the breast are more often ER and PR negative in both humans and dogs. Promising breast cancer biomarkers in both humans and canines are cancer-associated stroma (CAS), circulating tumor cells and tumor DNA (ctDNA), exosomes and miRNAs, and metabolites.

Membrane mesothelin expression positivity is associated with poor clinical outcome of luminal-type breast cancer

Mesothelin is expressed in various types of malignant tumors. The present study immunohistochemically investigated mesothelin expression and its clinicopathological significance in each subtype of breast cancer, with special reference to its cellular localization, in particular, membrane mesothelin expression. Using tissue specimens from 482 patients with breast cancer, immunohistochemistry was used to study mesothelin expression and help classify its localization as membrane or cytoplasmic expression. Mesothelin expression was detected in 77 (16.0%) cases and was the highest in triple-negative breast cancer (31/75; 41.3%), followed by human epithelial growth factor receptor type 2 type (6/33, 18.2%) and luminal type (36/374; 9.6%). Among the 482 cases, membrane mesothelin expression was detected in 73 cases and was significantly associated with a negative hormone receptor status, higher Ki-67 labeling index, nuclear grade 3 and a lower relapse-free survival rate. Cytoplasmic mesothelin expression was not significantly associated with a lower relapse-free survival rate (P=0.058). In the 343 cases of luminal type, the membrane mesothelin expression-positive group had significantly worse prognosis than the membrane mesothelin-expression-negative group (P=0.042). There was no significant difference in the relapse-free survival rate according to the membrane mesothelin expression status in the triple-negative type and other types. It was suggested that membrane mesothelin expression in luminal type breast cancer is associated with a lower rate of relapse-free survival.

Therapeutic Potential of Chemically Modified miR-489 in Triple-Negative Breast Cancers

Triple-negative breast cancers (TNBCs) lack ER, PR and her2 receptors that are targets of common breast cancer therapies with poor prognosis due to their high rates of metastasis and chemoresistance. Based on our previous studies that epigenetic silencing of a potential metastasis suppressor, arrestin domain-containing 3 (ARRDC3), is linked to the aggressive nature of TNBCs, we identified a sub-group of tumor suppressing miRNAs whose expressions were significantly up-regulated by ARRDC3 over-expression in TNBC cells. Among these tumor suppressing miRs, we found that miR-489 is most anti-proliferative in TNBC cells. miR-489 also blocked DNA damaging responses (DDRs) in TNBC cells. To define the mechanism by which miR-489 inhibits TNBC cell functions, we screened the potential target genes of miR-489 and identified MDC-1 and SUZ-12 as novel target genes of miR-489 in TNBC cells. To further exploit the therapeutic potentials of miR-489 in TNBC models, we chemically modified the guide strand of miR-489 (CMM489) by replacing Uracil with 5-fluorouracil (5-FU) so that tumor suppressor (miR-489) and DNA damaging (5-FU) components are combined into a single agent as a novel drug candidate for TNBCs. Our studies demonstrated that CMM489 shows superior effects over miR-489 or 5-FU in inhibition of TNBC cell proliferation and tumor progression, suggesting its therapeutic efficacy in TNBC models.

Correlation between the Expression of PD-L1 and Clinicopathological Parameters in Triple Negative Breast Cancer Patients

Objective

Triple-negative breast cancer (TNBC) is a heterogenous group of tumors with no estrogen receptor (ER), progesterone receptor (PR) and Cerb-B2/HER2 expression. Programmed death ligand-1 (PD-L1) is a transmembrane protein located on both non-tumor and tumor cells and it has been shown to be associated with the escape of tumor cells from the immune system. PD-L1-targeted therapy alone or in combination is now an alternative strategy in several aggressive tumor types. In this respect, TNBC is a potential candidate having limited treatment options and poor outcome.

Material and Methods

Sixty-one breast cancers with no expression of ER, PR and Cerb-B2/HER2 were chosen to study PD-L1 immunohistochemistry. PD-L1 staining and its correlation with main clinicopathological parameters were evaluated.

Results

The percentage of PD-L1 positivity was 37.7% and 47.5% in tumor and tumor microenvironment, respectively. The positivity rate was higher in breast carcinomas with medullary features (83.3%) and metaplastic carcinoma (66.6%) subgroups. PD-L1 expression of tumors was positively correlated with their Ki-67 score and PD-L1 positivity of the tumor microenvironment. No significant relationship was found between the other variables.

Conclusion

PD-L1 expression rate was remarkable both in the tumor and the tumor microenvironment of TNBCs. Larger cohorts of TNBC are required to further describe their PD-L1 expression characteristics and help standardize PD-L1 immunohistochemistry assays in these tumors.

MAT2B expression correlates with poor prognosis in triple-negative breast cancer

Background: In conjunction with the methionine adenosyltransferase 2A (MAT2A), MAT2B protein catalyses the formation of methyl donor S-adenosylmethionine to mediate cell metabolism, including proliferation and apoptosis. In this study, we investigated the functional and molecular mechanisms by which MAT2B influences triple-negative breast cancer (TNBC). Methods: The mRNA level of MAT2B in three human TNBC cell lines and 40 TNBC tissue samples was analysed using quantitative reverse transcription polymerase chain reaction. The relationship between MAT2B expression and the clinicopathological characteristics of TNBC patients was also analysed. Further, MAT2B function was investigated using a series of in vitro and in vivo assays with cells in which MAT2B was inhibited using RNAi. Results: We found that the mRNA levels of MAT2B were upregulated in all human TNBC cell lines tested. Moreover, positive expression of MAT2B was significantly correlated with higher T classification and M-stage. We also found that a higher level of MAT2B was correlated with worse relapse-free survival (RFS) according to a log-rank test. Next, we showed that the direct inhibition, using RNAi, of MAT2B in MDA-MB-231 and MDA-MB-468 cells inhibited cell growth and migration and induced apoptosis. Knockdown of MAT2B in MDA-MB-231 cells also repressed the expression of phosphorylated AKT and phosphorylated extracellular regulated protein kinases 1/2 (ERK1/2). Both phosphorylated AKT and ERK1/2 inhibitors reduced cell growth and migration, and induced apoptosis in MDA-MB-231 cells. As expected, knockdown of MAT2B in MDA-MB-231 cells significantly decreased the rate of tumour growth in vivo. Conclusion: Our results demonstrated that targeting MAT2B could suppress cell growth and migration and induce apoptosis by inhibiting the AKT and ERK pathways in TNBC. Thus, targeting MAT2B requires further investigation as a therapeutic intervention for TNBC.

The "Yin and Yang" of Natural Compounds in Anticancer Therapy of Triple-Negative Breast Cancers

Among the different types of breast cancers, triple-negative breast cancers (TNBCs) are highly aggressive, do not respond to conventional hormonal/human epidermal growth factor receptor 2 (HER2)-targeted interventions due to the lack of the respective receptor targets, have chances of early recurrence, metastasize, tend to be more invasive in nature, and develop drug resistance. The global burden of TNBCs is increasing regardless of the number of cytotoxic drugs being introduced into the market each year as they have only moderate efficacy and/or unforeseen side effects. Therefore, the demand for more efficient therapeutic interventions, with reduced side effects, for the treatment of TNBCs is rising. While some plant metabolites/derivatives actually induce the risk of cancers, many plant-derived active principles have gained attention as efficient anticancer agents against TNBCs, with fewer adverse side effects. Here we discuss the possible oncogenic molecular pathways in TNBCs and how the purified plant-derived natural compounds specifically target and modulate the genes and/or proteins involved in these aberrant pathways to exhibit their anticancer potential. We have linked the anticancer potential of plant-derived natural compounds (luteolin, chalcones, piperine, deguelin, quercetin, rutin, fisetin, curcumin, resveratrol, and others) to their ability to target multiple dysregulated signaling pathways (such as the Wnt/β-catenin, Notch, NF-κB, PI3K/Akt/mammalian target of rapamycin (mTOR), mitogen-activated protein kinase (MAPK) and Hedgehog) leading to suppression of cell growth, proliferation, migration, inflammation, angiogenesis, epithelial-mesenchymal transition (EMT) and metastasis, and activation of apoptosis in TNBCs. Plant-derived compounds in combination with classical chemotherapeutic agents were more efficient in the treatment of TNBCs, possibly with lesser side effects.

Synergistically Enhancing the Therapeutic Effect of Radiation Therapy with Radiation Activatable and Reactive Oxygen Species-Releasing Nanostructures

Nanoparticle-based radio-sensitizers can amplify the effects of radiation therapy on tumor tissue even at relatively low concentrations while reducing the potential side effects to healthy surrounding tissues. In this study, we investigated a hybrid anisotropic nanostructure, composed of gold (Au) and titanium dioxide (TiO₂), as a radio-sensitizer for radiation therapy of triple-negative breast cancer (TNBC). In contrast to other gold-based radio sensitizers, dumbbell-like Au-TiO₂ nanoparticles (DATs) show a synergistic therapeutic effect on radiation therapy, mainly because of strong asymmetric electric coupling between the high atomic number metals and dielectric oxides at their interfaces. The generation of secondary electrons and reactive oxygen species (ROS) from DATs triggered by X-ray irradiation can significantly enhance the radiation effect. After endocytosed by cancer cells, DATs can generate a large amount of ROS under X-ray irradiation, eventually inducing cancer cell apoptosis. Significant tumor growth suppression and overall improvement in survival rate in a TNBC tumor model have been successfully demonstrated under DAT uptake for a radio-sensitized radiation therapy.

Arctigenin inhibits STAT3 and exhibits anticancer potential in human triple-negative breast cancer therapy

Triple-negative breast cancers (TNBCs) are the most aggressive and hard-to-treat breast tumors with poor prognosis, and exploration for novel therapeutic drugs is impending. Arctigenin (Atn), a bioactive lignan isolated from seeds of Arctium lappa L, has been reported to inhibit many cancer types; however, the effect of Atn on TNBC remains unclear. In this study, we demonstrated that Atn decreased proliferation, and induced apoptosis in TNBC cells. Furthermore, we explored the underlying mechanism of Atn inhibition on TNBC cells. Computational docking and affinity assay showed that Atn bound to the SH2 domain of STAT3. Atn inhibited STAT3 binding to genomic DNA by disrupting hydrogen bond linking between DNA and STAT3. In addition, Atn augmented Taxotere^®-induced TNBC cell cytotoxicity. TNBC xenograft tests also confirmed the antitumor effect of Atn in vivo. These characteristics render Atn as a promising candidate drug for further development and for designing new effective STAT3 inhibitors.

Cellular uptake mechanism and comparative evaluation of antineoplastic effects of paclitaxel-cholesterol lipid emulsion on triple-negative and non-triple-negative breast cancer cell lines

There is no effective clinical therapy for triple-negative breast cancers (TNBCs), which have high low-density lipoprotein (LDL) requirements and express relatively high levels of LDL receptors (LDLRs) on their membranes. In our previous study, a novel lipid emulsion based on a paclitaxel-cholesterol complex (PTX-CH Emul) was developed, which exhibited improved safety and efficacy for the treatment of TNBC. To date, however, the cellular uptake mechanism and intracellular trafficking of PTX-CH Emul have not been investigated. In order to offer powerful proof for the therapeutic effects of PTX-CH Emul, we systematically studied the cellular uptake mechanism and intracellular trafficking of PTX-CH Emul and made a comparative evaluation of antineoplastic effects on TNBC (MDA-MB-231) and non-TNBC (MCF7) cell lines through in vitro and in vivo experiments. The in vitro antineoplastic effects and in vivo tumor-targeting efficiency of PTX-CH Emul were significantly more enhanced in MDA-MB-231-based models than those in MCF7-based models, which was associated with the more abundant expression profile of LDLR in MDA-MB-231 cells. The results of the cellular uptake mechanism indicated that PTX-CH Emul was internalized into breast cancer cells through the LDLR-mediated internalization pathway via clathrin-coated pits, localized in lysosomes, and then released into the cytoplasm, which was consistent with the internalization pathway and intracellular trafficking of native LDL. The findings of this paper further confirm the therapeutic potential of PTX-CH Emul in clinical applications involving TNBC therapy.