Unlocking the effective alliance of β-lapachone and hydroxytyrosol against triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) is characterised by its aggressiveness and resistance to chemotherapy, demanding the development of effective strategies against its unique characteristics. Derived from lapacho tree bark, β-lapachone (β-LP) selectively targets cancer cells with elevated levels of the detoxifying enzyme NQO1. Hydroxytyrosol (HT) is a phenolic compound derived from olive trees with important anticancer properties that include the inhibition of cancer stem cells (CSCs) and metastatic features in TNBC, as well as relevant antioxidant activities by mechanisms such as the induction of NQO1. We aimed to study whether these compounds could have synergistic anticancer activity in TNBC cells and the possible role of NQO1. For this pourpose, we assessed the impact of β-LP (0.5 or 1.5 μM) and HT (50 and 100 μM) on five TNBC cell lines. We demonstrated that the combination of β-LP and HT exhibits anti-proliferative, pro-apoptotic, and cell cycle arrest effects in several TNBC cells, including docetaxel-resistant TNBC cells. Additionally, it effectively inhibits the self-renewal and clonogenicity of CSCs, modifying their aggressive phenotype. However, the notable impact of the β-LP-HT combination does not appear to be solely associated with the levels of the NQO1 protein and ROS. RNA-Seq analysis revealed that the combination's anticancer activity is linked to a strong induction of endoplasmic reticulum stress and apoptosis through the unfolded protein response. In conclusion, in this study, we demonstrated how the combination of β-LP and HT could offer an affordable, safe, and effective approach against TNBC.

TGFβ Governs the Pleiotropic Activity of NDRG1 in Triple-Negative Breast Cancer Progression

In triple-negative breast cancer (TNBC), the pleiotropic NDRG1 (N-Myc downstream regulated gene 1) promotes progression and worse survival, yet contradictory results were documented, and the mechanisms remain unknown. Phosphorylation and localization could drive NDRG1 pleiotropy, nonetheless, their role in TNBC progression and clinical outcome was not investigated. We found enhanced p-NDRG1 (Thr346) by TGFβ1 and explored whether it drives NDRG1 pleiotropy and TNBC progression. In tissue microarrays of 81 TNBC patients, we identified that staining and localization of NDRG1 and p-NDRG1 (Thr346) are biomarkers and risk factors associated with shorter overall survival. We found that TGFβ1 leads NDRG1, downstream of GSK3β, and upstream of NF-κB, to differentially regulate migration, invasion, epithelial-mesenchymal transition, tumor initiation, and maintenance of different populations of cancer stem cells (CSCs), depending on the progression stage of tumor cells, and the combination of TGFβ and GSK3β inhibitors impaired CSCs. The present study revealed the striking importance to assess both total NDRG1 and p-NDRG1 (Thr346) positiveness and subcellular localization to evaluate patient prognosis and their stratification. NDRG1 pleiotropy is driven by TGFβ to differentially promote metastasis and/or maintenance of CSCs at different stages of tumor progression, which could be abrogated by the inhibition of TGFβ and GSK3β.

Nanomedicine as a Promising Tool to Overcome Immune Escape in Breast Cancer

Breast cancer is the most common type of malignancy and leading cause of cancer death among women worldwide. Despite the current revolutionary advances in the field of cancer immunotherapy, clinical response in breast cancer is frequently below expectations, in part due to various mechanisms of cancer immune escape that produce tumor variants that are resistant to treatment. Thus, a further understanding of the molecular events underlying immune evasion in breast cancer may guarantee a significant improvement in the clinical success of immunotherapy. Furthermore, nanomedicine provides a promising opportunity to enhance the efficacy of cancer immunotherapy by improving the delivery, retention and release of immunostimulatory agents in targeted cells and tumor tissues. Hence, it can be used to overcome tumor immune escape and increase tumor rejection in numerous malignancies, including breast cancer. In this review, we summarize the current status and emerging trends in nanomedicine-based strategies targeting cancer immune evasion and modulating the immunosuppressive tumor microenvironment, including the inhibition of immunosuppressive cells in the tumor area, the activation of dendritic cells and the stimulation of the specific antitumor T-cell response.

Antioxidants for the Treatment of Breast Cancer: Are We There Yet?

Breast cancer is the most frequent cancer and the leading cause of cancer death in women. Oxidative stress and the generation of reactive oxygen species (ROS) have been related to cancer progression. Compared to their normal counterparts, tumor cells show higher ROS levels and tight regulation of REDOX homeostasis to maintain a low degree of oxidative stress. Traditionally antioxidants have been extensively investigated to counteract breast carcinogenesis and tumor progression as chemopreventive agents; however, there is growing evidence indicating their potential as adjuvants for the treatment of breast cancer. Aimed to elucidate whether antioxidants could be a reality in the management of breast cancer patients, this review focuses on the latest investigations regarding the ambivalent role of antioxidants in the development of breast cancer, with special attention to the results derived from clinical trials, as well as their potential use as plausible agents in combination therapy and their power to ameliorate the side effects attributed to standard therapeutics. Data retrieved herein suggest that antioxidants play an important role in breast cancer prevention and the improvement of therapeutic efficacy; nevertheless, appropriate patient stratification based on “redoxidomics” or tumor subtype is mandatory in order to define the dosage for future standardized and personalized treatments of patients.

GARP is a key molecule for mesenchymal stromal cell responses to TGF-β and fundamental to control mitochondrial ROS levels

Multipotent mesenchymal stromal cells (MSCs) have emerged as a promising cell therapy in regenerative medicine and for autoimmune/inflammatory diseases. However, a main hurdle for MSCs-based therapies is the loss of their proliferative potential in vitro. Here we report that glycoprotein A repetitions predominant (GARP) is required for the proliferation and survival of adipose-derived MSCs (ASCs) via its regulation of transforming growth factor-β (TGF-β) activation. Silencing of GARP in human ASCs increased their activation of TGF-β which augmented the levels of mitochondrial reactive oxygen species (mtROS), resulting in DNA damage, a block in proliferation and apoptosis. Inhibition of TGF-β signaling reduced the levels of mtROS and DNA damage and restored the ability of GARP-/low ASCs to proliferate. In contrast, overexpression of GARP in ASCs increased their proliferative capacity and rendered them more resistant to etoposide-induced DNA damage and apoptosis, in a TGF-β-dependent manner. In summary, our data show that the presence or absence of GARP on ASCs gives rise to distinct TGF-β responses with diametrically opposing effects on ASC proliferation and survival.

Activating Transcription Factor 4 Modulates TGFβ-Induced Aggressiveness in Triple-Negative Breast Cancer via SMAD2/3/4 and mTORC2 Signaling

Purpose: On the basis of the identified stress-independent cellular functions of activating transcription factor 4 (ATF4), we reported enhanced ATF4 levels in MCF10A cells treated with TGFβ1. ATF4 is overexpressed in patients with triple-negative breast cancer (TNBC), but its impact on patient survival and the underlying mechanisms remain unknown. We aimed to determine ATF4 effects on patients with breast cancer survival and TNBC aggressiveness, and the relationships between TGFβ and ATF4. Defining the signaling pathways may help us identify a cell signaling-tailored gene signature.Experimental Design: Patient survival data were determined by Kaplan-Meier analysis. Relationship between TGFβ and ATF4, their effects on aggressiveness (tumor proliferation, metastasis, and stemness), and the underlying pathways were analyzed in three TNBC cell lines and in vivo using patient-derived xenografts (PDX).Results: ATF4 overexpression correlated with TNBC patient survival decrease and a SMAD-dependent crosstalk between ATF4 and TGFβ was identified. ATF4 expression inhibition reduced migration, invasiveness, mammosphere-forming efficiency, proliferation, epithelial-mesenchymal transition, and antiapoptotic and stemness marker levels. In PDX models, ATF4 silencing decreased metastases, tumor growth, and relapse after chemotherapy. ATF4 was shown to be active downstream of SMAD2/3/4 and mTORC2, regulating TGFβ/SMAD and mTOR/RAC1-RHOA pathways independently of stress. We defined an eight-gene signature with prognostic potential, altered in 45% of 2,509 patients with breast cancer.Conclusions: ATF4 may represent a valuable prognostic biomarker and therapeutic target in patients with TNBC, and we identified a cell signaling pathway-based gene signature that may contribute to the development of combinatorial targeted therapies for breast cancer. Clin Cancer Res; 24(22); 5697-709. ©2018 AACR.

Abstract 2035: Knockdown of TGFβ-activated ATF4 inhibits triple negative breast cancer metastases independently of cellular stress

Background. Triple negative breast cancer (TNBC) is a very aggressive form of breast cancer which is characterized by a poor survival rate and high incidence of metastases. The integrated stress response (ISR) is activated under stress conditions (hypoxia, nutrient deprivation, or endoplasmic reticulum stress) and reduces the protein synthesis through phospho-eIF2α/ATF4 (activating transcription factor 4) to regulate cell fate. ATF4, which is overexpressed in breast cancer including TNBC, regulates tumor growth, autophagy, drug resistance, and metastasis during ISR through PERK and GCN2 pathways. We have reported enhanced ATF4 expression in unstressed MCF10A cells treated with TGFβ1. Here, we investigate the potential TGFβ-mediated stress-independent control of ATF4 activity and its impact on the TNBC-associated metastasis.

Methods. SUM159PT and BT549 TNBC cell lines were treated with human recombinant TGFβ1 (10 ng/ml) and the TGFBRI kinase inhibitor LY2157299 (5µM) for 72h. Effects of TGFβ on ATF4 expression were assessed by silencing SMAD2/3 and SMAD4 with TGFβ1 for 24h in SUM159PT and BT549 cells. Changes in ATF4 expression by IRS were assessed after PERK, GCN2, PKR, HRI, and eIF2α inhibition with TGFβ1 for 72h in SUM159PT, BT549 and MDA-MB-231 cell lines. ATF4 expression levels were determined by RT-PCR and/or western blot. Effects on TGFβ-induced metastasis were analyzed by ATF4 knockdown for 48h by using two different siRNA sequences (#1 and #2) following treatment with TGFβ1 for 24h. Migration and invasion were performed by wound healing and transwell assays, respectively. Results were compared to a scrambled siRNA as negative control (SCR).

Results. Our results show that ATF4 expression (at RNA and protein levels) was abrogated by LY2157299 upon TGFβ activation, suggesting that ATF4 is active downstream of TGFBRI. This result was supported by further SMAD2/3 and SMAD4 knockdown following treatment with TGFβ1, which was correlated with decreased ATF4 expression. Additionally, we assessed whether ATF4 inhibition can reduce the TGFβ-induced metastatic properties of TNCB cell lines. We found that ATF4 depletion inhibited migration and invasiveness in the three cell lines tested. ATF4 is known to exert a pro-metastatic role downstream of ISR through PERK and GCN2 pathways. Our results demonstrate that, upon treatment with TGFβ1, knockdown of the IRS mediators PERK, PKR, GCN2, HRI, and eIF2α did not correlate with a consistent decrease of ATF4 levels in the three cell lines.

Conclusion. In conclusion, our results show for the first time that ATF4 is a downstream target of the canonical TGFβ/SMAD pathway in a ISR-independent fashion, and its depletion correlates with an inhibition of the TGFβ1-mediated migration and invasion of TNBC cell lines. Therefore, ATF4 may represent a therapeutic target in TNBC patients with active TGFβ signaling pathway.

Citation Format: Jenny C. Chang, Alberto Ramirez, Maria P. Molina, Francisca E. Cara, Wei Qian, Wen Chen, Anthony J. Kozielski, Roberto R. Rosato, Juan A. Marchal, Jose A. Lorente, Pedro Sanchez-Rovira, Sergio Granados-Principal. Knockdown of TGFβ-activated ATF4 inhibits triple negative breast cancer metastases independently of cellular stress [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2035.

Nanoparticles administered intrapericardially enhance payload myocardial distribution and retention

Pharmacological therapies for cardiovascular diseases are limited by short-term pharmacokinetics and extra-cardiac adverse effects. Improving delivery selectivity specifically to the heart, wherein therapeutic drug levels can be maintained over time, is highly desirable. Nanoparticle (NP)-based pericardial drug delivery could provide a strategy to concentrate therapeutics within a unique, cardiac-restricted compartment to allow sustained drug penetration into the myocardium. Our objective was to explore the kinetics of myocardial penetration and retention after pericardial NP drug delivery. Fluorescently-tagged poly(lactic-co-glycolic acid) (PLGA) NPs were loaded with BODIPY, a fluorophore, and percutaneously administered into the pericardium via subxiphoid puncture in rabbits. At distinct timepoints hearts were examined for presence of NPs and BODIPY. PLGA NPs were found non-uniformly distributed on the epicardium following pericardial administration, displaying a half-life of ~2.5days in the heart. While NPs were mostly confined to epicardial layers, BODIPY was capable of penetrating into the myocardium, resulting in a transmural gradient. The distinct architecture and physiology of the different regions of the heart influenced BODIPY distribution, with fluorophore penetrating more readily into atria than ventricles. BODIPY proved to have a long-term presence within the heart, with a half-life of ~7days. Our findings demonstrate the potential of utilizing the pericardial space as a sustained drug-eluting reservoir through the application of nanoparticle-based drug delivery, opening several exciting avenues for selective and prolonged cardiac therapeutics.

Rapamycin nanoparticles localize in diseased lung vasculature and prevent pulmonary arterial hypertension

Vascular remodeling resulting from pulmonary arterial hypertension (PAH) leads to endothelial fenestrations. This feature can be exploited by nanoparticles (NP), allowing them to extravasate from circulation and accumulate in remodeled pulmonary vessels. Hyperactivation of the mTOR pathway in PAH drives pulmonary arterial smooth muscle cell proliferation. We hypothesized that rapamycin (RAP)-loaded NPs, an mTOR inhibitor, would accumulate in diseased lungs, selectively targeting vascular mTOR and preventing PAH progression. RAP poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-PCL) NPs were fabricated. NP accumulation and efficacy were examined in a rat monocrotaline model of PAH. Following intravenous (IV) administration, NP accumulation in diseased lungs was verified via LC/MS analysis and confocal imaging. Pulmonary arteriole thickness, right ventricular systolic pressures, and ventricular remodeling were determined to assess the therapeutic potential of RAP NPs. Monocrotaline-exposed rats showed increased NP accumulation within lungs compared to healthy controls, with NPs present to a high extent within pulmonary perivascular regions. RAP, in both free and NP form, attenuated PAH development, with histological analysis revealing minimal changes in pulmonary arteriole thickness and no ventricular remodeling. Importantly, NP-treated rats showed reduced systemic side effects compared to free RAP. This study demonstrates the potential for nanoparticles to significantly impact PAH through site-specific delivery of therapeutics.

A specifically designed nanoconstruct associates, internalizes, traffics in cardiovascular cells, and accumulates in failing myocardium: a new strategy for heart failure diagnostics and therapeutics

AIMS

Ongoing inflammation and endothelial dysfunction occurs within the local microenvironment of heart failure, creating an appropriate scenario for successful use and delivery of nanovectors. This study sought to investigate whether cardiovascular cells associate, internalize, and traffic a nanoplatform called mesoporous silicon vector (MSV), and determine its intravenous accumulation in cardiac tissue in a murine model of heart failure.

METHODS AND RESULTS

In vitro cellular uptake and intracellular trafficking of MSVs was examined by scanning electron microscopy, confocal microscopy, time-lapse microscopy, and flow cytometry in cardiac myocytes, fibroblasts, smooth muscle cells, and endothelial cells. The MSVs were internalized within the first hours, and trafficked to perinuclear regions in all the cell lines. Cytotoxicity was investigated by annexin V and cell cycle assays. No significant evidence of toxicity was found. In vivo intravenous cardiac accumulation of MSVs was examined by high content fluorescence and confocal microscopy, with results showing increased accumulation of particles in failing hearts compared with normal hearts. Similar to observations in vitro, MSVs were able to associate, internalize, and traffic to the perinuclear region of cardiomyocytes in vivo.

CONCLUSIONS

Results show that MSVs associate, internalize, and traffic in cardiovascular cells without any significant toxicity. Furthermore, MSVs accumulate in failing myocardium after intravenous administration, reaching intracellular regions of the cardiomyocytes. These findings represent a novel avenue to develop nanotechnology-based therapeutics and diagnostics in heart failure.

Colocalized delivery of rapamycin and paclitaxel to tumors enhances synergistic targeting of the PI3K/Akt/mTOR pathway

Ongoing clinical trials target the aberrant PI3K/Akt/mammalian target of rapamycin (mTOR) pathway in breast cancer through administration of rapamycin, an allosteric mTOR inhibitor, in combination with paclitaxel. However, synergy may not be fully exploited clinically because of distinct pharmacokinetic parameters of drugs. This study explores the synergistic potential of site-specific, colocalized delivery of rapamycin and paclitaxel through nanoparticle incorporation. Nanoparticle drug loading was accurately controlled, and synergistic drug ratios established in vitro. Precise drug ratios were maintained in tumors 48 hours after nanoparticle administration to mice, at levels twofold greater than liver and spleen, yielding superior antitumor activity compared to controls. Simultaneous and preferential in vivo delivery of rapamycin and paclitaxel to tumors yielded mechanistic insights into synergy involving suppression of feedback loop Akt phosphorylation and its downstream targets. Findings demonstrate that a same time, same place, and specific amount approach to combination chemotherapy by means of nanoparticle delivery has the potential to successfully translate in vitro synergistic findings in vivo. Predictive in vitro models can be used to determine optimum drug ratios for antitumor efficacy, while nanoparticle delivery of combination chemotherapies in preclinical animal models may lead to enhanced understanding of mechanisms of synergy, ultimately opening several avenues for personalized therapy.