Relapsed triple-negative breast cancer: challenges and treatment strategies

MerTK Drives Proliferation and Metastatic Potential in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is characterized by the absence of the estrogen receptor, progesterone receptor, and receptor tyrosine kinase HER2 expression. Due to the limited number of FDA-approved targeted therapies for TNBC, there is an ongoing need to understand the molecular underpinnings of TNBC for the development of novel combinatorial treatment strategies. This study evaluated the role of the MerTK receptor tyrosine kinase on proliferation and invasion/metastatic potential in TNBC. Immunohistochemical analysis demonstrated MerTK expression in 58% of patient-derived TNBC xenografts. The stable overexpression of MerTK in human TNBC cell lines induced an increase in proliferation rates, robust in vivo tumor growth, heightened migration/invasion potential, and enhanced lung metastases. NanoString nCounter analysis of MerTK-overexpressing SUM102 cells (SUM102-MerTK) revealed upregulation of several signaling pathways, which ultimately drive cell cycle progression, reduce apoptosis, and enhance cell survival. Proteomic profiling indicated increased endoglin (ENG) production in SUM102-MerTK clones, suggesting that MerTK creates a conducive environment for increased proliferative and metastatic activity via elevated ENG expression. To determine ENG's role in increasing proliferation and/or metastatic potential, we knocked out ENG in a SUM102-MerTK clone with CRISPR technology. Although this ENG knockout clone exhibited similar in vivo growth to the parental SUM102-MerTK clone, lung metastasis numbers were significantly decreased ~4-fold, indicating that MerTK enhances invasion and metastasis through ENG. Our data suggest that MerTK regulates a unique proliferative signature in TNBC, promoting robust tumor growth and increased metastatic potential through ENG upregulation. Targeting MerTK and ENG simultaneously may provide a novel therapeutic approach for TNBC patients.

Frequency of Programmed Death Receptor Ligand 1 Expression and Clinicopathological Factors Associated With Metastatic Triple-Negative Breast Cancer at a Tertiary Cancer Care Centre in South India

Purpose Triple-negative breast cancer (TNBC) has a poor outcome compared to other subtypes. Immune checkpoint inhibitors (ICIs) have changed the treatment paradigm in metastatic diseases as well as in neoadjuvant setting. The response to these agents is affected by programmed death ligand 1 (PDL1) receptor expression which are reported objectively as a score. PDL1 is a prognostic marker also. Here, we present clinicopathological characteristics of metastatic TNBCs, report the proportion of PDL1 expression and its association with clinicopathological factors as well as survival. Methods This is a prospective study carried out at a tertiary cancer care centre in South India. Case records of all breast cancer patients treated in two years between August 2021 and July 2023 were reviewed, patients with metastatic TNBC were selected. Patient's characteristics, histological features, molecular profile, and treatment were analyzed. PDL1 testing was carried out on pretreatment tumor tissue sections with immunohistochemistry (IHC) (Dako 22C3). PDL1 staining was interpreted as negative or positive based on combined positive score (CPS), with an expression less than 10 considered negative. Results A total of 118 patients were analyzed. With a median age of 46 years (36-65 years), 52.5% (62/118) were premenopausal. Family history of Ca Breast was seen in 22% (26/118) patients. A majority of patients had left-sided tumor 55.9% (66/118). Visceral metastasis was more common 96.6% (82/118) than skeletal. Radical intent of treatment was adopted in 10% as patients had oligometastatic disease at presentation. As front-line treatment, anthracycline-based chemotherapy was administered to the majority 54.2% (64/118). The PDL1 expression with CPS more or equal to 10 was seen in 32.2% (38/118) patients. Survival was associated with menopausal status (p value=0.000) and family history (p value=0.028) but not with PDL1 nor sidedness in our study. Estimated survival at 12 months in PDL1 negative case is 10 ± 0.29 months, while in PDL1 positive case it is slightly more at 10 ± 0.75 months, but difference was not found to be statistically significant (p value=0.15). Conclusion TNBCs are highly aggressive subtype with limited treatment options and poorer outcomes. Our study shows PDL1 expression in 31.66% of the cases similar to other literature from India. Survival is associated with menopausal status and family history. No association was found between survival and PDL1 as well sidedness in our study.

A review of biological targets and therapeutic approaches in the management of triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is a heterogeneous, aggressive phenotype of breast cancer with associated chemoresistance. The development of chemo- or radioresistance could be attributed to diverse tumor microenvironments, overexpression of membrane proteins (transporters), epigenetic changes, and alteration of the cell signaling pathways/genes associated with the development of cancer stem cells (CSCs).

AIM OF REVIEW

Due to the diverse and heterogeneous nature of TNBC, therapeutic response to the existing modalities offers limited scope and thus results in reccurance after therapy. To establish landmark therapeutic efficacy, a number of novel therapeutic modalities have been proposed. In addition, reversal of the resistance that developed during treatment may be altered by employing appropriate therapeutic modalities. This review aims to discuss the plethora of investigations carried out, which will help readers understand and make an appropriate choice of therapy directed toward complete elimination of TNBC.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This manuscript addresses the major contributory factors from the tumor microenvironment that are responsible for the development of chemoresistance and poor prognosis. The associated cellular events and molecular mechanism-based therapeutic interventions have been explained in detail. Inhibition of ABC transporters, cell signaling pathways associated with CSCs, and epigenetic modification offers promising results in this regard. TNBC progression, invasion, metastasis and recurrence can also be inhibited by blocking multiple cell signaling pathways, targeting specific receptors/epigenetic targets, disrupting bioenergetics and generating reactive oxygen species (ROS).

Oligometastatic breast cancer: Dissecting the clinical and biological uniqueness of this emerging entity. Can we pursue curability?

Metastatic breast cancer represents an incurable condition, however, the increasing interest towards the oligometastatic entity is now challenging this assumption. Up to 20% of patients with metastatic breast cancer present with oligometastatic disease, which refers to metastatic breast cancer presenting or recurring with limited metastatic burden. In the last years, progressive advancements in imaging techniques, the growing availability of minimally invasive locoregional treatments, alongside the increasing expectations from a patient perspective, have contributed to rising the awareness towards this emerging entity. In the present work we comprehensively reviewed available evidence regarding oligometastatic breast cancer, focusing on clinical and biological notions virtually supporting the adoption of a curative approach when treating this condition. We also discussed main areas of uncertainties, providing a research agenda that may guide and fine-tune the future investigation in this field.

Oncogenic and Stemness Signatures of the High-Risk HCMV Strains in Breast Cancer Progression

Simple Summary

Lately, human cytomegalovirus (HCMV) has been progressively implicated in carcinogenesis alongside its oncomodulatory impact. CMV-Transformed Human mammary epithelial cells (CTH) phenotype might be defined by giant cell cycling, whereby the generation of polyploid giant cancer cells (PGCCs) could expedite the acquisition of malignant phenotypes. Herein, the main study objectives were to assess the transformation potential in vitro and evaluate the obtained cellular phenotype, the genetic and molecular features, and the activation of cellular stemness programs of HCMV strains, B544 and B693, which were previously isolated from triple-negative breast cancer (TNBC) biopsies. The strains’ sensitivity to paclitaxel and ganciclovir combination therapy was evaluated. A unique molecular landscape was unveiled in the tumor microenvironment of TNBC harboring high-risk HCMV. Overall, the explicit oncogenic and stemness signatures highlight HCMV potential in breast cancer progression thus paving the way for targeted therapies and clinical interventions which prolong the overall survival of breast cancer patients.

Abstract

Background: Human cytomegalovirus (HCMV) oncomodulation, molecular mechanisms, and ability to support polyploid giant cancer cells (PGCCs) generation might underscore its contribution to oncogenesis, especially breast cancers. The heterogeneity of strains can be linked to distinct properties influencing the virus-transforming potential, cancer types induced, and patient’s clinical outcomes. Methods: We evaluated the transforming potential in vitro and assessed the acquired cellular phenotype, genetic and molecular features, and stimulation of stemness of HCMV strains, B544 and B693, isolated from EZH2^HighMyc^High triple-negative breast cancer (TNBC) biopsies. Therapeutic response assessment after paclitaxel (PTX) and ganciclovir (GCV) treatment was conducted in addition to the molecular characterization of the tumor microenvironment (TME). Findings: HCMV-B544 and B693 transformed human mammary epithelial cells (HMECs). We detected multinucleated and lipid droplet-filled PGCCs harboring HCMV. Colony formation was detected and Myc was overexpressed in CMV-Transformed-HMECs (CTH cells). CTH-B544 and B693 stimulated stemness and established an epithelial/mesenchymal hybrid state. HCMV-IE1 was detected in CTH long-term cultures indicating a sustained viral replication. Biopsy B693 unveiled a tumor signature predicting a poor prognosis. CTH-B544 cells were shown to be more sensitive to PTX/GCV therapy. Conclusion: The oncogenic and stemness signatures of HCMV strains accentuate the oncogenic potential of HCMV in breast cancer progression thereby leading the way for targeted therapies and innovative clinical interventions that will improve the overall survival of breast cancer patients.

Intelligent Biomimetic Nanoplatform for Systemic Treatment of Metastatic Triple-Negative Breast Cancer via Enhanced EGFR-Targeted Therapy and Immunotherapy

Triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancer, and it is associated with a high recurrence rate, metastatic potential, and poor prognosis. Thus, effective therapeutic strategies for TNBC are urgently required. The epidermal growth factor receptor (EGFR) is considered to be a potential therapeutic target for TNBC. However, there are limitations to the use of targeted therapies, such as afatinib (AFT), particularly drug resistance. Here, we investigated a poly(d,l-lactide-glycolide) (PLGA)-based intelligent bionic nanoplatform, termed AFT/2-BP@PLGA@MD, which combined targeted therapy with immunotherapy. In this platform, PLGA was used to encapsulate 2-bromo-palmitate (2-BP), a palmitoylation inhibitor, to enhance the efficacy of AFT against TNBC cells. PLGA was coated with a cancer cell membrane anchored with a cleavable peptide by matrix metalloproteinase-2 to block programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1). 2-BP significantly enhanced the capacity of AFT to inhibit the proliferation and migration of tumor cells in vitro. Moreover, the tumor cell membrane-coated AFT/2-BP@PLGA@MD nanoparticles exhibited enhanced tumor targeting ability in vivo. The AFT/2-BP@PLGA@MD nanoparticles significantly inhibited the growth and metastasis of 4T1 tumor and prolonged the survival of tumor-bearing mice. The nanoparticles also triggered antitumor immune response. Collectively, we report an effective therapeutic strategy for clinically refractory TNBC.

Piperlongumine loaded PLGA nanoparticles inhibit cancer stem-like cells through modulation of STAT3 in mammosphere model of triple negative breast cancer

TNBC exhibits higher rate of chemoresistance, metastasis, and relapse among all subtypes of breast cancer. This malignant statein TNBC is due to self-renewing sub-population of cells called cancer stem cells (CSCs). They are major caveats in TNBC treatment and need to be obliterated. In this regard, we explored piperlongumine (PL) that has remarkable anti-cancerous property but poor pharmacokinetics limits its application. So, to enhance its biological activity we developed PLGA based nanoformulation for PL (PL-NPs) and examined anti-CSCs effects of PL and PL-NPs in mammospheres. Results indicated that PL-NPs have higher cellular uptake than PL in mammospheres. Further, we demonstrated that PL-NPs remarkably inhibit various characteristics of CSCs like expression of ALDH, self-renewability, chemoresistance, and EMT in mammopsheres. We next investigated the possible mechanism underlying these multi-modal effects, and found that inhibition of STAT3 might be the driving force. In order to confirm this, we used colivelin a potent synthetic peptide activator of STAT3 in combination with treatments and found that anti-CSCs effects of PL and PL-NPs were reversed. Taken together, our data indicates that PL-NPs show enhanced inhibition of CSCs through downregulation of STAT3 and provides insight into development of PL based nanomedicine for targeting CSCs in TNBC.

ADRB3 induces mobilization and inhibits differentiation of both breast cancer cells and myeloid-derived suppressor cells

Metastatic tumors are mainly composed of neoplastic cells escaping from the primary tumor and inflammatory cells egressing from bone marrow. Cancer cell and inflammatory cell are remained in the state of immaturity during migration to distant organs. Here, we show that ADRB3 is crucial in cell mobilization and differentiation. Immunohistochemistry revealed ADRB3 expression is significantly more frequent in breast cancer tissues than in adjacent noncancerous tissues (92.1% vs. 31.5%). Expression of ADRB3 correlated with malignant degree, TNM stage and poor prognosis. Moreover, ADRB3 expression was markedly high in activated disseminated tumor cells, myeloid-derived suppressor cells (MDSCs), lymphocytes and neutrophil extracellular traps of patients. Importantly, ADRB3 promoted the expansion of MDSC through stimulation of bone marrow mobilization and inhibiting of the differentiation of immature myeloid cells. Furthermore, ADRB3 promoted MCF-7 cells proliferation and inhibited transdifferentiation into adipocyte-like cell by activating mTOR pathway. Ultimately, the MDSC-deficient phenotype of ADRB3 ^-/- PyMT mice was associated with impairment of mammary tumorigenesis and reduction in pulmonary metastasis. Collectively, ADRB3 promotes metastasis by inducing mobilization and inhibiting differentiation of both breast cancer cells and MDSCs.

Doxorubicin-Resistant TNBC Cells Exhibit Rapid Growth with Cancer Stem Cell-like Properties and EMT Phenotype, Which Can Be Transferred to Parental Cells through Autocrine Signaling

Emerging evidence suggests that breast cancer stem cells (BCSCs), and epithelial–mesenchymal transition (EMT) may be involved in resistance to doxorubicin. However, it is unlear whether the doxorubicin-induced EMT and expansion of BCSCs is related to cancer dormancy, or outgrowing cancer cells with maintaining resistance to doxorubicin, or whether the phenotypes can be transferred to other doxorubicin-sensitive cells. Here, we characterized the phenotype of doxorubicin-resistant TNBC cells while monitoring the EMT process and expansion of CSCs during the establishment of doxorubicin-resistant MDA-MB-231 human breast cancer cells (DRM cells). In addition, we assessed the potential signaling associated with the EMT process and expansion of CSCs in doxorubicin-resistance of DRM cells. DRM cells exhibited morphological changes from spindle-shaped MDA-MB-231 cells into round-shaped giant cells. They exhibited highly proliferative, EMT, adhesive, and invasive phenotypes. Molecularly, they showed up-regulation of Cyclin D1, mesenchymal markers (β-catenin, and N-cadherin), MMP-2, MMP-9, ICAM-1 and down-regulation of E-cadherin. As the molecular mechanisms responsible for the resistance to doxorubicin, up-regulation of EGFR and its downstream signaling, were suggested. AKT and ERK1/2 expression were also increased in DRM cells with the advancement of resistance to doxorubicin. Furthermore, doxorubicin resistance of DRM cells can be transferred by autocrine signaling. In conclusion, DRM cells harbored EMT features with CSC properties possessing increased proliferation, invasion, migration, and adhesion ability. The doxorubicin resistance, and doxorubicin-induced EMT and CSC properties of DRM cells, can be transferred to parental cells through autocrine signaling. Lastly, this feature of DRM cells might be associated with the up-regulation of EGFR.

TH1902, a new docetaxel-peptide conjugate for the treatment of sortilin-positive triple-negative breast cancer

Triple‐negative breast cancer (TNBC) is a heterogeneous subgroup of cancers which lacks the expression and/or amplification of targetable biomarkers (ie, estrogen receptor, progestrogen receptor, and human epidermal growth factor receptor 2), and is often associated with the worse disease‐specific outcomes than other breast cancer subtypes. Here, we report that high expression of the sortilin (SORT1) receptor correlates with the decreased survival in TNBC patients, and more importantly in those bearing lymph node metastases. By exploiting SORT1 function in ligand internalization, a new anticancer treatment strategy was designed to target SORT1‐positive TNBC‐derived cells both in vitro and in two in vivo tumor xenografts models. A peptide (TH19P01), which requires SORT1 for internalization and to which many anticancer drugs could be conjugated, was developed. In vitro, while the TH19P01 peptide itself did not exert any antiproliferative or apoptotic effects, the docetaxel‐TH19P01 conjugate (TH1902) exerted potent antiproliferative and antimigratory activities when tested on TNBC‐derived MDA‐MB‐231 cells. TH1902 triggered faster and more potent apoptotic cell death than did unconjugated docetaxel. The apoptotic and antimigratory effects of TH1902 were both reversed by two SORT1 ligands, neurotensin and progranulin, and on siRNA‐mediated silencing of SORT1. TH1902 also altered microtubule polymerization and triggered the downregulation of the anti‐apoptotic Bcl‐xL biomarker. In vivo, both i.p. and i.v. administrations of TH1902 led to greater tumor regression in two MDA‐MB‐231 and HCC‐70 murine xenograft models than did docetaxel, without inducing neutropenia. Altogether, the data demonstrates the high in vivo efficacy and safety of TH1902 against TNBC through a SORT1 receptor‐mediated mechanism. This property allows for selective treatment of SORT1‐positive TNBC and makes TH1902 a promising avenue for personalized therapy with the potential of improving the therapeutic window of cytotoxic anticancer drugs such as docetaxel.

Enhanced Paclitaxel Efficacy to Suppress Triple-Negative Breast Cancer Progression Using Metronomic Chemotherapy with a Controlled Release System of Electrospun Poly-d-l-Lactide-Co-Glycolide (PLGA) Nanofibers

Simple Summary

Treatment of metastatic triple-negative breast cancer (TNBC) relies on chemotherapy. To improve the efficacy of chemotherapy and avoid systemic toxicity, metronomic chemotherapy using continuous administration of low-dose chemotherapy could be a solution. The paclitaxel-loaded PLGA nanofibers allow for continuous and prolonged drug release, which is compatible with the concept of metronomic chemotherapy. The animal study revealed that the strategy successfully inhibited the growth of the primary tumor and distant metastasis without sarcopenia. These data offer new insights into the role of drug-loaded nanofibers in the treatment of metastatic TNBC.

Abstract

Triple-negative breast cancer (TNBC) is highly aggressive and responds poorly to conventional chemotherapy. The challenge of TNBC therapy is to maximize the efficacies of conventional chemotherapeutic agents and reduce their toxicities. Metronomic chemotherapy using continuous low-dose chemotherapy has been proposed as a new treatment option, but this approach is limited by the selection of drugs. To improve antitumor therapeutic effects, we developed electrospun paclitaxel-loaded poly-d-l-lactide-co-glycolide (PLGA) nanofibers as a topical implantable delivery device for controlled drug release and site-specific treatment. The subcutaneously implanted paclitaxel-loaded nanofibrous membrane in mice was compatible with the concept of metronomic chemotherapy; it significantly enhanced antitumor activity, inhibited local tumor growth, constrained distant metastasis, and prolonged survival compared with intraperitoneal paclitaxel injection. Furthermore, under paclitaxel-loaded nanofiber treatment, systemic toxicity was low with a persistent increase in lean body weight in mice; in contrast, body weight decreased in other groups. The paclitaxel-loaded nanofibrous membranes provided sustained drug release and site-specific treatment by directly targeting and changing the tumor microenvironment, resulting in low systemic toxicity and a significant improvement in the therapeutic effect and safety compared with conventional chemotherapy. Thus, metronomic chemotherapy with paclitaxel-loaded nanofibrous membranes offers a promising strategy for the treatment of TNBC.

PGMD/curcumin nanoparticles for the treatment of breast cancer

The present study aims at developing PGMD (poly-glycerol-malic acid-dodecanedioic acid)/curcumin nanoparticles based formulation for anticancer activity against breast cancer cells. The nanoparticles were prepared using both the variants of PGMD polymer (PGMD 7:3 and PGMD 6:4) with curcumin (i.e. CUR NP 7:3 and CUR NP 6:4). The size of CUR NP 7:3 and CUR NP 6:4 were found to be ~ 110 and 218 nm with a polydispersity index of 0.174 and 0.36, respectively. Further, the zeta potential of the particles was - 18.9 and - 17.5 mV for CUR NP 7:3 and CUR NP 6:4, respectively. The entrapment efficiency of both the nanoparticles was in the range of 75-81%. In vitro anticancer activity and the scratch assay were conducted on breast cancer cell lines, MCF-7 and MDA-MB-231. The IC50 of the nanoformulations was observed to be 40.2 and 33.6 μM at 48 h for CUR NP 7:3 and CUR NP 6:4, respectively, in MCF-7 cell line; for MDA-MB-231 it was 43.4 and 30.5 μM. Acridine orange/EtBr and DAPI staining assays showed apoptotic features and nuclear anomalies in the treated cells. This was further confirmed by western blot analysis that showed overexpression of caspase 9 indicating curcumin role in apoptosis.

Role of intracellular water in the normal-to-cancer transition in human cells-insights from quasi-elastic neutron scattering

The transition from normal to malignant state in human cells is still a poorly understood process. Changes in the dynamical activity of intracellular water between healthy and cancerous human cells were probed as an innovative approach for unveiling particular features of malignancy and identifying specific reporters of cancer. Androgen-unresponsive prostate and triple-negative breast carcinomas were studied as well as osteosarcoma, using the technique of quasi-elastic neutron scattering. The cancerous cells showed a considerably higher plasticity relative to their healthy counterparts, this being more significant for the mammary adenocarcinoma. Also, the data evidence that the prostate cancer cells display the highest plasticity when compared to triple-negative mammary cancer and osteosarcoma, the latter being remarkably less flexible. Furthermore, the results suggest differences between the flexibility of different types of intracellular water molecules in normal and cancerous cells, as well as the number of molecules involved in the different modes of motion. The dynamics of hydration water molecules remain virtually unaffected when going from healthy to cancer cells, while cytoplasmic water (particularly the rotational motions) undergoes significant changes upon normal-to-cancer transition. The results obtained along this study can potentially help to understand the variations in cellular dynamics underlying carcinogenesis and tumor metastasis, with an emphasis on intracellular water.

OSW-1 inhibits tumor growth and metastasis by NFATc2 on triple-negative breast cancer

OSW‐1 is a natural compound extracted from the bulbs of Ornithogalum saundersiae in 1992. It has been shown strong antitumor activities in various cancer cells. However, the effects of OSW‐1 on tumor growth and metastasis in breast cancer are still poorly understood. In our research, we showed that OSW‐1 had a strong anticancer effect on breast cancer cells, but lower toxicity to normal cells. Accordingly, it also revealed significant inhibition of tumor growth by OSW‐1 in xenograft model. In addition, we performed Annexin V/PI‐labeled flow cytometric assay and TUNEL assay and showed that OSW‐1 inhibited tumor growth by inducing apoptosis. Furthermore, we carried out transwell assays and found that OSW‐1 significantly repressed the migratory and invasive capabilities of triple‐negative breast cancer (TNBC) cells via mediating epithelial‐mesenchymal transition. Besides, OSW‐1 also could inhibit metastasis in an orthotopic model and resulted in a longer survival compared with control group. Finally, we performed RNA‐sequencing and cellular functions to investigate the molecular mechanism of how OSW‐1 inhibits TNBC, and identified NFATc2 may as a pivotal factor for OSW‐1‐mediated effects on cell death, tumor growth, invasion, and migration.

Decreased nonspecific adhesivity, receptor-targeted therapeutic nanoparticles for primary and metastatic breast cancer

Development of effective tumor cell-targeted nanodrug formulations has been quite challenging, as many nanocarriers and targeting moieties exhibit nonspecific binding to cellular, extracellular, and intravascular components. We have developed a therapeutic nanoparticle formulation approach that balances cell surface receptor-specific binding affinity while maintaining minimal interactions with blood and tumor tissue components (termed "DART" nanoparticles), thereby improving blood circulation time, biodistribution, and tumor cell-specific uptake. Here, we report that paclitaxel (PTX)-DART nanoparticles directed to the cell surface receptor fibroblast growth factor-inducible 14 (Fn14) outperformed both the corresponding PTX-loaded, nontargeted nanoparticles and Abraxane, an FDA-approved PTX nanoformulation, in both a primary triple-negative breast cancer (TNBC) model and an intracranial model reflecting TNBC growth following metastatic dissemination to the brain. These results provide new insights into methods for effective development of therapeutic nanoparticles as well as support the continued development of the DART platform for primary and metastatic tumors.

Epigenetic Activation of BRCA1 by Genistein In Vivo and Triple Negative Breast Cancer Cells Linked to Antagonism toward Aryl Hydrocarbon Receptor

Triple negative breast cancers (TNBC) are the most aggressive and lethal breast cancers (BC). The aryl hydrocarbon receptor (AHR) is often overexpressed in TNBC, and its activation results in the epigenetic silencing of BRCA1, which is a necessary factor for the transcriptional activation of estrogen receptor (ER)α. The dietary isoflavone genistein (GEN) modulates BRCA1 CpG methylation in BC cells. The purpose of this study was to investigate the effect of GEN on BRCA1 epigenetic regulation and AHR activity in vivo and TNBC cells. Mice were administered a control or GEN-enriched (4 and 10 ppm) diet from gestation through post-natal day 50. Mammary tissue was analyzed for changes in BRCA1 regulation and AhR activity. TNBC cells with constitutively hypermethylated BRCA1 (HCC38) and MCF7 cells were used. Protein levels and mRNA expression were measured by Western blot and real-time PCR, respectively. BRCA1 promoter occupancy and CpG methylation were analyzed by chromatin immunoprecipitation and methylation-specific PCR, respectively. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. GEN administered in the diet dose-dependently decreased basal Brca1 methylation and AHR activity in the mammary gland of adult mice. HCC38 cells were found to overexpress constitutively active AHR in parallel with BRCA1 hypermethylation. The treatment of HCC38 cells with GEN upregulated BRCA1 protein levels, which was attributable to decreased CpG methylation and AHR binding at BRCA1 exon 1a. In MCF7 cells, GEN prevented the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-dependent localization of AHR at the BRCA1 gene. These effects were consistent with those elicited by control AHR antagonists galangin (GAL), CH-223191, and α-naphthoflavone. The pre-treatment with GEN sensitized HCC38 cells to the antiproliferative effects of 4-hydroxytamoxifen. We conclude that the dietary compound GEN may be effective for the prevention and reversal of AHR-dependent BRCA1 hypermethylation, and the restoration of ERα-mediated response, thus imparting the sensitivity of TNBC to antiestrogen therapy.

RAD6B is a major mediator of triple negative breast cancer cisplatin resistance: Regulation of translesion synthesis/Fanconi anemia crosstalk and BRCA1 independence

Triple negative breast cancer (TNBC) is an aggressive breast cancer subtype with few therapy options besides chemotherapy. Although platinum-based drugs have shown initial activity in BRCA1-mutated TNBCs, chemoresistance remains a challenge. Here we show that RAD6B (UBE2B), a principal mediator of translesion synthesis (TLS), is overexpressed in BRCA1 wild-type and mutant TNBCs, and RAD6B overexpression correlates with poor survival. Pretreatment with a RAD6-selective inhibitor, SMI#9, enhanced cisplatin chemosensitivity of BRCA1 wild-type and mutant TNBCs. SMI#9 attenuated cisplatin-induced PCNA monoubiquitination (TLS marker), FANCD2 (Fanconi anemia (FA) activation marker), and TLS polymerase POL η. SMI#9-induced decreases in γH2AX levels were associated with concomitant inhibition of H2AX monoubiquitination, suggesting a key role for RAD6 in modulating cisplatin-induced γH2AX via H2AX monoubiquitination. Concordantly, SMI#9 inhibited γH2AX, POL η and FANCD2 foci formation. RAD51 foci formation was unaffected by SMI#9, however, its recruitment to double-strand breaks was inhibited. Using the DR-GFP-based assay, we showed that RAD6B silencing or SMI#9 treatment impairs homologous recombination (HR) in HR-proficient cells. DNA fiber assays confirmed that restart of cisplatin-stalled replicating forks is inhibited by SMI#9 in both BRCA1 wild-type and mutant TNBC cells. Consistent with the in vitro data, SMI#9 and cisplatin combination treatment inhibited BRCA1 wild-type and mutant TNBC growth as compared to controls. These RAD6B activities are unaffected by BRCA1 status of TNBCs suggesting that the RAD6B function in TLS/FA crosstalk could occur in HR-dependent and independent modes. Collectively, these data implicate RAD6 as an important therapeutic target for TNBCs irrespective of their BRCA1 status.

Low Dose of Paclitaxel Combined with XAV939 Attenuates Metastasis, Angiogenesis and Growth in Breast Cancer by Suppressing Wnt Signaling

Triple-negative breast cancer (TNBC) accounts for 15% of overall breast cancer. A lack of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2 receptor) makes TNBC more aggressive and metastatic. Wnt signaling is one of the important pathways in the cellular process; in TNBC it is aberrantly regulated, which leads to the progression and metastasis. In this study, we designed a therapeutic strategy using a combination of a low dose of paclitaxel and a Wnt signaling inhibitor (XAV939), and examined the effect of the paclitaxel-combined XAV939 treatment on diverse breast cancer lines including TNBC cell lines (MDA-MB-231, MDA-MB-468, and BT549) and ER+ve cell lines (MCF-7 and T-47D). The combination treatment of paclitaxel (20 nM) and XAV939 (10 µM) exerted a comparable therapeutic effect on MDA-MB-231, MDA-MB-468, BT549, MCF-7, and T-47D cell lines, relative to paclitaxel with a high dose (200 nM). The paclitaxel-combined XAV939 treatment induced apoptosis by suppressing Bcl-2 and by increasing the cleavage of caspases-3 and PARP. In addition, the in vivo results of the paclitaxel-combined XAV939 treatment in a mice model with the MDA-MB-231 xenograft further confirmed its therapeutic effect. Furthermore, the paclitaxel-combined XAV939 treatment reduced the expression of β-catenin, a key molecule in the Wnt pathway, which led to suppression of the expression of epithelial-mesenchymal transition (EMT) markers and angiogenic proteins both at mRNA and protein levels. The expression level of E-cadherin was raised, which potentially indicates the inhibition of EMT. Importantly, the breast tumor induced by pristane was significantly reduced by the paclitaxel-combined XAV939 treatment. Overall, the paclitaxel-combined XAV939 regimen was found to induce apoptosis and to inhibit Wnt signaling, resulting in the suppression of EMT and angiogenesis. For the first time, we report that our combination approach using a low dose of paclitaxel and XAV939 could be conducive to treating TNBC and an external carcinogen-induced breast cancer.

EGCG-Derivative G28 Shows High Efficacy Inhibiting the Mammosphere-Forming Capacity of Sensitive and Resistant TNBC Models

Recent studies showed that Fatty Acid Synthase (FASN), a lipogenic enzyme overexpressed in several carcinomas, plays an important role in drug resistance. Furthermore, the enrichment of Breast Cancer Stem Cell (BCSC) features has been found in breast tumors that progressed after chemotherapy. Hence, we used the triple negative breast cancer (TNBC) cell line MDA-MB-231 (231) to evaluate the FASN and BCSC population role in resistance acquisition to chemotherapy. For this reason, parental cell line (231) and its derivatives resistant to doxorubicin (231DXR) and paclitaxel (231PTR) were used. The Mammosphere-Forming Assay and aldehyde dehydrogenase (ALDH) enzyme activity assay showed an increase in BCSCs in the doxorubicin-resistant model. Moreover, the expression of some transcription factors involved in epithelial-mesenchymal transition (EMT), a process that confers BCSC characteristics, was upregulated after chemotherapy treatment. FASN inhibitors C75, (−)-Epigallocatechin 3-gallate (EGCG), and its synthetic derivatives G28, G56 and G37 were used to evaluate the effect of FASN inhibition on the BCSC-enriched population in our cell lines. G28 showed a noticeable antiproliferative effect in adherent conditions and, interestingly, a high mammosphere-forming inhibition capacity in all cell models. Our preliminary results highlight the importance of studying FASN inhibitors for the treatment of TNBC patients, especially those who progress after chemotherapy.

Overall survival, costs and healthcare resource use by number of regimens received in elderly patients with newly diagnosed metastatic triple-negative breast cancer

Aim: This analysis estimated the overall survival, treatment patterns and economic burden of elderly metastatic triple-negative breast cancer patients. Materials & methods: Patients (≥66 years) with metastatic triple-negative breast cancer were identified from the SEER-Medicare database. Treatment patterns were defined in terms of first, second and third or more regimens. Healthcare resource use and costs were reported over the follow-up period and over the treatment duration of each regimen. Results: A total of 51% of patients did not receive chemotherapy. Taxanes were most commonly used. Median survival was 7 months. The mean cumulative (per patient per month) cost per patient was US$73,586 (US$10,084). Mean cost in first and second regimen were US$26,950 and US$33,347. Conclusion: About half of patients did not receive chemotherapy. Receipt of increasing regimens led to higher mean costs and healthcare resource use.

Triple-negative breast cancer: Pattern of recurrence and survival outcomes

Introduction: Triple-negative breast cancer (TNBC) is a subtype of breast cancer which is defined as the absence of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 overexpression by immunohistochemistry. As the survival data on TNBC in the Indian population are scant, this study was done to analyze the clinicopathological features and clinical outcomes of TNBC patients. Materials and Methods: Data from medical records of patients with breast cancer between 2009 and 2014 were retrieved, and patients with TNBC were identified and analyzed for demographic and clinicopathological features. Survival analyses were performed using the Kaplan–Meier method for disease-free survival (DFS) and overall survival (OS). Results: A total of 1024 breast cancer patients were registered at our institute during the study period, of which 198 were TNBCs accounting for 19.3% of all breast cancers. Median age at the diagnosis was 50 years (range, 22–78 years). Lymph nodal positivity in TNBC was associated with larger tumor size (P = 0.003) and higher tumor grade (P = 0.01). At a median follow-up of 48 months (range, 12–88), 36 (19.1%) patients had recurrence of the disease, whereas 28 (14%) patients were lost to follow-up. Lung (52.7%) was the most common site of recurrence followed by bone (25%) and brain (11.1%). Three-year DFS and OS were 63.2% and 65.6%, respectively. On univariate analysis, nodal status, size of tumor, and lymphovascular invasion were found to have a significant impact on OS and DFS. On multivariate analysis, only nodal status was significant for DFS and OS (P < 0.001 and P = 0.001, respectively). Conclusions: TNBCs have a rapid clinical course, and early recurrences are common inspite of timely medical intervention which reflects the aggressive tumor biology. This warrants further studies on intensification of chemotherapy and identification and development of targeted therapy aimed at decreasing recurrences and improving survival in this patient population.

Potential protein markers for breast cancer recurrence: a retrospective cohort study

BACKGROUND

We evaluated five key proteins involved in various cancer-related pathways and assessed their relation to breast cancer recurrence.

METHODS

We used the Kentucky Cancer Registry to retrospectively identify primary invasive breast cancer cases (n = 475) that were diagnosed and treated at University of Kentucky Medical Center between 2000 and 2007. Breast cancer recurrence was observed in 62 cases during the 5-year follow-up after diagnosis. Protein expression or activity level was analyzed from surgery tissue using immuno-histochemical assays.

RESULTS

Compared to ER+/PR+/HER2- patients without recurrence, those with recurrence had higher TWIST expression (p = 0.049) but lower ABL1/ABL2 activity (p = 0.003) in primary tumors. We also found that triple-negative breast cancer patients with recurrence had higher SNAI1 expression compared to those without recurrence (p = 0.03). After adjusting for potential confounders, the higher ABL1/ABL2 activity in primary tumors was associated with a decreased risk of recurrence (OR 0.72, 95% CI 0.85-0.90) among ER+/PR+/HER2- patients. In addition, among patients with recurrence we observed that the activity level of ABL1/ABL2 was significantly increased in recurrent tumors compared to the matched primary tumors regardless of the subtype (p = 0.013).

CONCLUSIONS

These findings provide evidence that the expression/activity level of various proteins may be differentially associated with risk of recurrence of breast tumor subtypes.

A Phenotypic Cell-Binding Screen Identifies a Novel Compound Targeting Triple-Negative Breast Cancer

We describe a "phenotypic cell-binding screen" by which therapeutic candidate targeting cancer cells of a particular phenotype can be isolated without knowledge of drug targets. Chemical library beads are incubated with cancer cells of the phenotype of interest in the presence of cancer cells lacking the phenotype of interest, and then the beads bound to only cancer cells of the phenotype of interest are selected as hits. We have applied this screening strategy in discovering a novel compound (LC129-8) targeting triple-negative breast cancer (TNBC). LC129-8 displayed highly specific binding to TNBC in cancer cell lines and patient-derived tumor tissues. LC129-8 exerted anti-TNBC activity by inducing apoptosis, inhibiting proliferation, reversing epithelial-mesenchymal transition, downregulating cancer stem cell activity and blocking in vivo tumor growth.

How shall we treat early triple-negative breast cancer (TNBC): from the current standard to upcoming immuno-molecular strategies

Triple-negative breast cancer (TNBC) is a long-lasting orphan disease in terms of little therapeutic progress during the past several decades and still the standard of care remains chemotherapy. Experimental discovery of molecular signatures including the ‘BRCAness’ highlighted the innate heterogeneity of TNBC, generating the diversity of TNBC phenotypes. As it contributes to enhancing genomic instability, it has widened the therapeutic spectrum of TNBC. In particular, unusual sensitivity to DNA damaging agents was denoted in patients with BRCA deficiency, suggesting therapeutic benefit from platinum and poly(ADP-ribose) polymerase inhibitors. However, regardless of enriched chemosensitivity and immunogenicity, majority of patients with TNBC still suffer from dismal clinical outcomes including early relapse and metastatic spread. Therefore, efforts into more precise and personalised treatment are critical at this point. Accordingly, the advance of multiomics has revealed novel actionable targets including PI3K-Akt-mTOR and epidermal growth factor receptor signalling pathways, which might actively participate in modulating the chemosensitivity and immune system. Also, TNBC has long been considered a potential protagonist of immunotherapy in breast cancer, supported by abundant tumour-infiltrating lymphocytes and heterogeneous tumour microenvironment. Despite that, earlier studies showed somewhat unsatisfactory results of monotherapy with immune-checkpoint inhibitors, consistently durable responses in responders were noteworthy. Based on these results, further combinatorial trials either with other chemotherapy or targeted agents are underway. Incorporating immune-molecular targets into combination as well as refining the standard chemotherapy might be the key to unlock the future of TNBC. In this review, we share the current and upcoming treatment options of TNBC in the framework of scientific and clinical data, especially focusing on early stage of TNBC.

Engineering Remotely Triggered Liposomes to Target Triple Negative Breast Cancer

Triple Negative Breast Cancer (TNBC) continues to present a challenge in the clinic, as there is still no approved targeted therapy. TNBC is the worst sub-type of breast cancer in terms of prognosis and exhibits a deficiency in estrogen, progesterone, and human epidermal growth factor 2 (HER2) receptors. One possible option for the treatment of TNBC is chemotherapy. The issue with many chemotherapy drugs is that their effectiveness is diminished due to poor water solubility, and the method of administration directly or with a co-solvent intravenously can lead to an increase in toxicity. The issues of drug solubility can be avoided by using liposomes as a drug delivery carrier. Liposomes are engineered, biological nanoconstructs that possess the ability to encapsulate both hydrophobic and hydrophilic drugs and have been clinically approved to treat cancer. Specific targeting of cancer cell receptors through the use of ligands conjugated to the surface of drug-loaded liposomes could lessen damage to normal, healthy tissue. This study focuses on polyethylene glycol (PEG)-coated, folate conjugated, benzoporphyrin derivative (BPD)-loaded liposomes for treatment via photodynamic therapy (PDT). The folate receptor is over expressed on TNBC cells so these liposomes are targeted for greater uptake into cancer cells. PDT involves remotely irradiating light at 690 nm to trigger BPD, a hydrophobic photosensitive drug, to form reactive oxygen species that cause tumor cell death. BPD also displays a fluorescence signal when excited by light making it possible to image the fluorescence prior to PDT and for theranostics. In this study, free BPD, non-targeted and folate-targeted PEGylated BPD-loaded liposomes were introduced to a metastatic breast cancer cell line (MDA-MB-231) in vitro. The liposomes were reproducibly synthesized and characterized for size, polydispersity index (PDI), zeta potential, stability, and BPD release kinetics. Folate competition tests, fluorescence confocal imaging, and MTT assay were used to observe and quantify targeting effectiveness. The toxicity of BPD before and after PDT in monolayer and 3D in vitro cultures with TNBC cells was observed. This study may contribute to a novel nanoparticle-mediated approach to target TNBC using PDT.

Engineered Breast Cancer Cell Spheroids Reproduce Biologic Properties of Solid Tumors

Solid tumors develop as 3D tissue constructs. As tumors grow larger, spatial gradients of nutrients and oxygen and inadequate diffusive supply to cells distant from vasculature develops. Hypoxia initiates signaling and transcriptional alterations to promote survival of cancer cells and generation of cancer stem cells (CSCs) that have self-renewal and tumor-initiation capabilities. Both hypoxia and CSCs are associated with resistance to therapies and tumor relapse. This study demonstrates that 3D cancer cell models, known as tumor spheroids, generated with a polymeric aqueous two-phase system (ATPS) technology capture these important biological processes. Similar to solid tumors, spheroids of triple negative breast cancer cells deposit major extracellular matrix proteins. The molecular analysis establishes presence of hypoxic cells in the core region and expression of CSC gene and protein markers including CD24, CD133, and Nanog. Importantly, these spheroids resist treatment with chemotherapy drugs. A combination treatment approach using a hypoxia-activated prodrug, TH-302, and a chemotherapy drug, doxorubicin, successfully targets drug resistant spheroids. This study demonstrates that ATPS spheroids recapitulate important biological and functional properties of solid tumors and provide a unique model for studies in cancer research.

Mechanisms underlying effect of the mycotoxin cytochalasin B on induction of cytotoxicity, modulation of cell cycle, Ca2+ homeostasis and ROS production in human breast cells

Cytochalasin B, a cell-permeable mycotoxin isolated from the fungus Phoma spp., shows a wide range of biological effects, among which its potent antitumor activity has raised great interests in different models. However, the cytotoxic activity of cytochalasin B and its underlying mechanisms have not been elucidated in breast cells. This study examined the effect of cytochalasin B on MCF 10A human breast epithelial cells and ZR-75-1 human breast cancer cells. Cytochalasin B (10-20μM) concentration-dependently induced cytotoxicity, cell cycle arrest, and [Ca²⁺]_i rises in ZR-75-1 cells but not in MCF 10A cells. In ZR-75-1 cells, cytochalasin B triggered G2/M phase arrest through the modulation of CDK1, cyclin B1, p53, p27 and p21 expressions. The Ca²⁺ signal response induced by cytochalasin B was reduced by removing extracellular Ca²⁺ and was inhibited by the store-operated Ca²⁺ channel blocker 2-APB and SKF96365. In Ca²⁺-free medium, cytochalasin B induced Ca²⁺ release through thapsigargin-sensitive endoplasmic reticulum stores. Moreover, cytochalasin B increased H₂O₂ levels but reduced GSH levels. The apoptotic effects evoked by cytochalasin B were partially inhibited by prechelating cytosolic Ca²⁺ with BAPTA-AM and the antioxidant NAC. Together, in ZR-75-1 cells but not in MCF 10A cells, cytochalasin B activated Ca²⁺-associated mitochondrial apoptotic pathways that involved G2/M phase arrest and ROS signaling. Furthermore, cytochalasin B induced [Ca²⁺]_i rises by releasing Ca²⁺ from the endoplasmic reticulum and causing Ca²⁺ influx through 2-APB or SKF96365-sensitive store-operated Ca²⁺ entry. Our findings provide new insights into the possible application of cytochalasin B in human breast cancer therapy.

Triple negative breast cancer: shedding light onto the role of pi3k/akt/mtor pathway

Breast cancer is one of the most widespread carcinoma and one of the main causes of cancer-related death worldwide, especially in women aged between 35 and 75 years. Among the different subtypes, triple negative breast cancer (TNBC) is characterized by the total absence of the estrogen-receptor (ER) and progesteron-receptor (PR) expression as well as the lack of human epidermal growth factor receptor 2 (HER2) overexpression or gene amplification. These biological characteristics confer to TNBC a higher aggressiveness and relapse risk along with poorer prognosis compared to other subtypes. Indeed, 5-years survival rate is still low and almost all patients die, despite any adjuvant treatment which at moment represents the heading pharmacological approach. To date, several clinical trials have been designed to investigate the potential role of some molecular markers, such as VEGF, EGFR, Src and mTOR, for targeted treatments in TNBC. In fact, many inhibitors of the PI3K/AKT/mTOR pathway, frequently de-regulated in TNBC, are acquiring a growing interest and several inhibitors are in preclinical development or already in early phase clinical trials. In this Review, we investigated the role of the PI3K/AKT/mTOR pathway in TNBC patients, by summarizing the molecular features that led to the distinction of different histotypes of TNBC. Furthermore, we provided an overview of the inhibition mechanisms of the mTOR and PI3K/AKT signaling pathways, highlighting the importance of integrating biological and clinical data for the development of mTOR inhibitors in order to implement targeted therapies for TNBC patients.

Elevated MARCKS phosphorylation contributes to unresponsiveness of breast cancer to paclitaxel treatment

Accumulating evidence has suggested that myristoylated alanine-rich C-kinase substrate (MARCKS) is critical for regulating multiple pathophysiological processes. However, the molecular mechanism underlying increased phosphorylation of MARCKS at Ser159/163 (phospho-MARCKS) and its functional consequence in neoplastic disease remain to be established. Herein, we investigated how phospho-MARCKS is regulated in breast carcinoma, and its role in the context of chemotherapy. In a screen of patients with breast tumors, we find that the abundance of phospho-MARCKS, not MARCKS protein per se, increased in breast cancers and positively correlated with tumor grade and metastatic status. Among chemotherapeutic agents, mitotic inhibitors, including paclitaxel, vincristine or eribulin, notably promoted phospho-MARCKS accumulation in multiple breast cancer cells. We further show that phospho-MARCKS acted upstream of Src activation upon paclitaxel exposure. Reduction of phospho-MARCKS by knockdown of MARCKS or pharmacological agents increased paclitaxel sensitivity. Particularly, a known phospho-MARCKS inhibitor, MANS peptide, was demonstrated to increase paclitaxel efficacy and attenuate angiogenesis/metastasis of xenografted breast cancer cells by decreasing abundance of phospho-MARCKS and messages of inflammatory mediators. Our data suggest that unresponsiveness of breast cancer to paclitaxel treatment is, at least in part, mediated by phospho-MARCKS and also provide an alternative therapeutic strategy against breast cancer by improving taxanes sensitivity.

Expression of receptor protein tyrosine phosphatase ζ is a risk factor for triple negative breast cancer relapse

Patients with triple negative breast cancer (TNBC) have a higher rate of distant recurrence and a poorer prognosis than those with other breast cancer subtypes. Therefore, it is important to study the mechanism of TNBC relapse. A retrospective immunohistochemical analysis of the expression of receptor protein tyrosine phosphatase ζ (PTPRZ1) and pleiotrophin (PTN) was performed for 325 cases of breast cancer. These samples included 66 cases of luminal A breast cancer, 67 cases of luminal B breast cancer, 78 cases of Her-2-enriched breast cancer, 78 cases of TNBC and 36 cases of relapsed TNBC (RTNBC). In addition, 30 control specimens and 30 cases of metastasized lymph nodes were examined. PTPRZ1 and PTN were highly expressed in the RTNBC group. Compared with the RTNBC group, significant differences in the expression of PTPRZ1 were observed between the TNBC, BC and control groups. A significant difference was observed in the expression of PTN in the BC group (P<0.05) compared to RTNBC, and there were no significant differences in the expression of PTPRZ1 and PTN among the molecular subtypes. No significant correlation was observed between the expression of PTPRZ1, PTN, ER, PR, Her-2 and ALN and the tumor size or menopause status. No significant correlation was identified between the expression of PTPRZ1 and PTN and the expression of CD24 and CD44. In summary, high expression of PTPRZ1 may be an independent risk indicator for TNBC recurrence and metastasis.

Platinum-based chemotherapy in triple-negative breast cancer: a systematic review and meta-analysis of randomized-controlled trials

The aim of this study was to evaluate the benefits of the addition of platinum agents for the treatment of patients with triple-negative breast cancer on the basis of randomized-controlled trials (RCTs). A fully recursive literature search was performed in the Cochrane Controlled Trials Register Databases, Medline, EMBASE, and Chinese Biomedical Literature Database in any language. RCTs were considered for inclusion. Eight randomized-controlled trials totaling 1142 patients were included. The objective response rate was reported in six RCTs, which were divided into two subgroups: palliative chemotherapy for a metastatic setting and neoadjuvant chemotherapy. Using the fixed-effects model, the difference between the platinum-based group and the non-platinum-based group was found to be statistically significant in the overall study [relative risk (RR)=1.36, P<0.00001], the subgroup of palliative chemotherapy (RR=2.42, P<0.00001), and the subgroup of neoadjuvant (RR=1.15, P=0.01). Pathological complete response rates were based on five studies, and the results between the platinum-based group and the non-platinum-based group also reached statistical significance both in the fixed-effects model (RR=1.43, P<0.0001) and in the random-effects model (RR=1.47, P=0.01). The results seemed to yield a better response rate and pathological complete response rate for platinum-based therapy in triple-negative breast cancer. However, because of the heterogeneous nature of primary trial outcomes, caution should be exercised in coming to this conclusion and further research is necessary to support these findings.

β-Catenin is required for the tumorigenic behavior of triple-negative breast cancer cells

Our previous data illustrated that activation of the canonical Wnt signaling pathway was enriched in triple-negative breast cancer and associated with reduced overall survival in all patients. To determine whether Wnt signaling may be a promising therapeutic target for triple-negative breast cancer, we investigated whether β-catenin was necessary for tumorigenic behaviors in vivo and in vitro. β-catenin expression level was significantly reduced in two human triple-negative breast cancer cell lines, MDA-MB-231 and HCC38, using lentiviral delivery of β-catenin-specific small hairpin RNAs (shRNAs). Upon implantation of the cells in the mammary fat pad of immunocompromised mice, we found that β-catenin shRNA HCC38 cells formed markedly smaller tumors than control cells and grew much more slowly. In in vitro assays, β-catenin silencing significantly reduced the percentage of Aldefluor-positive cells, a read-out of the stem-like cell population, as well as the expression of stem cell-related target genes including Bmi-1 and c-Myc. β-catenin-knockdown cells were also significantly impaired in their ability to migrate in wound-filling assays and form anchorage-independent colonies in soft agar. β-catenin-knockdown cells were more sensitive to chemotherapeutic agents doxorubicin and cisplatin. Collectively, these data suggest that β-catenin is required for triple-negative breast cancer development by controlling numerous tumor-associated properties, such as migration, stemness, anchorage-independent growth and chemosensitivity.

Preoperative carboplatin-paclitaxel-bevacizumab in triple-negative breast cancer: final results of the phase II Ca.Pa.Be study

PURPOSE

The phase II Ca.Pa.Be trial evaluated preoperative carboplatin-paclitaxel in combination with bevacizumab in triple-negative breast cancer patients with previously untreated stage II-III disease. The primary aim was the assessment of the rate of pathologic complete response (pCR). Secondary aims included safety, breast-conserving surgery rate, and early response assessment with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI).

METHODS

Patients with hormone receptor-negative, HER-2-negative stage II-III breast cancer were eligible. Treatment included paclitaxel 80 mg/mq + carboplatin area under the curve (AUC) 2 on days 1, 8, and 15, combined with bevacizumab 10 mg/kg on days 1 and 15 each 28 days, for 5 courses. At baseline, patients underwent breast DCE-MRI, followed by a single dose of bevacizumab 5 mg/kg (day -6). DCE-MRI was repeated before the initiation of chemotherapy.

RESULTS

Forty-four patients were enrolled. Forty-three patients underwent surgery, and 22 (50 %) received breast-conserving surgery (conversion rate from mastectomy indication at baseline, 34.4 %). A pCR in breast and axillary lymph nodes occurred in 22 patients (50 %). Bevacizumab-associated adverse events (AEs) were mild: G1-2 hypertension and bleeding occurred in 6 (13.6 %) and 12 (27 %) patients, respectively. No G4 nonhematologic AEs were recorded. More frequent G3 AEs were liver function test abnormalities (6.8 %), and diarrhea and fatigue (4.5 % each). The only G3-4 hematologic toxicity was neutropenia (G3, 25 %; G4, 9 %). Early assessed DCE-MRI response parameters failed to predict pCR.

CONCLUSIONS

The neoadjuvant anthracycline-free combination of weekly paclitaxel and carboplatin plus bevacizumab is active and safe in triple-negative breast cancer, and the rate of pCR is comparable to that observed with more intensive carboplatin- and bevacizumab-containing regimens. Further investigation is warranted.

Novel treatment strategies in triple-negative breast cancer: specific role of poly(adenosine diphosphate-ribose) polymerase inhibition

Inhibitors of the poly(adenosine triphosphate-ribose) polymerase (PARP)-1 enzyme induce synthetic lethality in cancers with ineffective DNA (DNA) repair or homologous repair deficiency, and have shown promising clinical activity in cancers deficient in DNA repair due to germ-line mutation in BRCA1 and BRCA2. The majority of breast cancers arising in carriers of BRCA1 germ-line mutations, as well as half of those in BRCA2 carriers, are classified as triple-negative breast cancer (TNBC). TNBC is a biologically heterogeneous group of breast cancers characterized by the lack of immunohistochemical expression of the ER, PR, or HER2 proteins, and for which the current standard of care in systemic therapy is cytotoxic chemotherapy. Many "sporadic" cases of TNBC appear to have indicators of DNA repair dysfunction similar to those in BRCA-mutation carriers, suggesting the possible utility of PARP inhibitors in a subset of TNBC. Significant genetic heterogeneity has been observed within the TNBC cohort, creating challenges for interpretation of prior clinical trial data, and for the design of future clinical trials. Several PARP inhibitors are currently in clinical development in BRCA-mutated breast cancer. The use of PARP inhibitors in TNBC without BRCA mutation will require biomarkers that identify cancers with homologous repair deficiency in order to select patients likely to respond. Beyond mutations in the BRCA genes, dysfunction in other genes that interact with the homologous repair pathway may offer opportunities to induce synthetic lethality when combined with PARP inhibition.

Par-4 prevents breast cancer recurrence

Therapy resistance and disease recurrence are two of the most challenging aspects in breast cancer treatment. A recent article in Cancer Cell makes a significant contribution toward a better understanding of this therapeutic problem by establishing downregulation of the tumor suppressor Par-4 as the primary determinant of breast cancer recurrence. This viewpoint brings forth the importance of their findings and its implications on future research and therapy.