Targeted Delivery of STAT-3 Modulator to Breast Cancer Stem-Like Cells Downregulates a Series of Stemness Genes

Targeting Lipid Metabolism in Cancer Stem Cells for Anticancer Treatment

Cancer stem cells (CSCs), or tumor-initiating cells (TICs), are small subpopulations (0.0001-0.1%) of cancer cells that are crucial for cancer relapse and therapy resistance. The elimination of each CSC is essential for achieving long-term remission. Metabolic reprogramming, particularly lipids, has a significant impact on drug efficacy by influencing drug diffusion, altering membrane permeability, modifying mitochondrial function, and adjusting the lipid composition within CSCs. These changes contribute to the development of chemoresistance in various cancers. The intricate relationship between lipid metabolism and drug resistance in CSCs is an emerging area of research, as different lipid species play essential roles in multiple stages of autophagy. However, the link between autophagy and lipid metabolism in the context of CSC regulation remains unclear. Understanding the interplay between autophagy and lipid reprogramming in CSCs could lead to the development of new approaches for enhancing therapies and reducing tumorigenicity in these cells. In this review, we explore the latest findings on lipid metabolism in CSCs, including the role of key regulatory enzymes, inhibitors, and the contribution of autophagy in maintaining lipid homeostasis. These recent findings may provide critical insights for identifying novel pharmacological targets for effective anticancer treatment.

Advanced Insights into Competitive Endogenous RNAs (ceRNAs) Regulated Pathogenic Mechanisms in Metastatic Triple-Negative Breast Cancer (mTNBC)

Triple-negative breast cancer is aggressive and challenging to treat because of a lack of targets and heterogeneity among tumors. A paramount factor in the mortality from breast cancer is metastasis, which is driven by genetic and phenotypic alterations that drive epithelial-mesenchymal transition, stemness, survival, migration and invasion. Many genetic and epigenetic mechanisms have been identified in triple-negative breast cancer that drive these metastatic phenotypes; however, this knowledge has not yet led to the development of effective drugs for metastatic triple-negative breast cancer (mTNBC). One that may not have received enough attention in the literature is post-translational regulation of broad sets of cancer-related genes through inhibitory microRNAs and the complex competitive endogenous RNA (ceRNA) regulatory networks they are influenced by. This field of study and the resulting knowledge regarding alterations in these networks is coming of age, enabling translation into clinical benefit for patients. Herein, we review metastatic triple-negative breast cancer (mTNBC), the role of ceRNA network regulation in metastasis (and therefore clinical outcomes), potential approaches for therapeutic exploitation of these alterations, knowledge gaps and future directions in the field.

Cancer stem cells: advances in knowledge and implications for cancer therapy

Cancer stem cells (CSCs), a small subset of cells in tumors that are characterized by self-renewal and continuous proliferation, lead to tumorigenesis, metastasis, and maintain tumor heterogeneity. Cancer continues to be a significant global disease burden. In the past, surgery, radiotherapy, and chemotherapy were the main cancer treatments. The technology of cancer treatments continues to develop and advance, and the emergence of targeted therapy, and immunotherapy provides more options for patients to a certain extent. However, the limitations of efficacy and treatment resistance are still inevitable. Our review begins with a brief introduction of the historical discoveries, original hypotheses, and pathways that regulate CSCs, such as WNT/β-Catenin, hedgehog, Notch, NF-κB, JAK/STAT, TGF-β, PI3K/AKT, PPAR pathway, and their crosstalk. We focus on the role of CSCs in various therapeutic outcomes and resistance, including how the treatments affect the content of CSCs and the alteration of related molecules, CSCs-mediated therapeutic resistance, and the clinical value of targeting CSCs in patients with refractory, progressed or advanced tumors. In summary, CSCs affect therapeutic efficacy, and the treatment method of targeting CSCs is still difficult to determine. Clarifying regulatory mechanisms and targeting biomarkers of CSCs is currently the mainstream idea.

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

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

Pan-cancer analysis reveals signal transducer and activator of transcription (STAT) gene family as biomarkers for prognostic prediction and therapeutic guidance

Background: The signal transducer and activator of transcription (STAT) gene family have been widely found to regulate cell proliferation, differentiation, apoptosis, and angiogenesis through complex signaling pathways, and thus impacting tumor formation and development in different types of tumor. However, the roles of STATs on prognostic prediction and therapeutic guidance in pan-cancer remain unexplored.

Materials and Methods: The dataset of 33 types of TCGA tumor, para-carcinoma and normal tissues, was obtained from the UCSC Xena database, including the gene expression profiles in the formats of FPKM value, demographic characteristics, clinical information, and survival data of STATs. Differential expression and co-expression analyses, WGCNA, clinical relevance analysis, immune subtype analysis, tumor stemness analysis, tumor purity analysis, immune infiltration analysis, immunotherapy related analysis, tumor mutation related analysis, and drug sensitivity analysis were performed by R software.

Results: Differential expression of STAT1 was found between normal and BRCA tissues (p < 0.001, log2FC = 0.895). Additionally, the strongest correlation among STATs lied between STAT1 and STAT2 (correlation coefficient = 0.6). Moreover, high expression levels of STAT1 (p = 0.031) were revealed to be notably correlated with poor prognosis in KIRP. In addition, STAT1 expressed the highest value in immune subtypes C1, C2, C3, and C6 in LUAD. What’s more, strong negative correlations were demonstrated between expression of STAT6 and mDNAss and mRNAss of TGCT. Additionally, STAT4 expression was characterized to be significantly negatively correlated with tumor purity of the majority of cancer types. Moreover, STAT1 and STAT3 were shown to be generally high-expressed in pan-cancer myeloid cells, and STATs all had positive correlation with the infiltration of the majority of immune cells. In addition, STATs were revealed to be closely linked with immunotherapy response. What’s more, STAT4 expression was identified to have a strong negative correlation with TMB value in DLBC. Last but not least, positive correlations were accessed between STAT5 and sensitivity of Nelarabine (cor = 0.600, p < 0.001).

Conclusion: In the present study, we identified STATs as biomarkers for prognostic prediction and therapeutic guidance in pan-cancer. Hopefully our findings could provide a valuable reference for future STATs research and clinical applications.

Use of acidic nanoparticles to rescue macrophage lysosomal dysfunction in atherosclerosis

Dysfunction in the macrophage lysosomal system including reduced acidity and diminished degradative capacity is a hallmark of atherosclerosis, leading to blunted clearance of excess cellular debris and lipids in plaques and contributing to lesion progression. Devising strategies to rescue this macrophage lysosomal dysfunction is a novel therapeutic measure. Nanoparticles have emerged as an effective platform to both target specific tissues and serve as drug delivery vehicles. In most cases, administered nanoparticles are taken up non-selectively by the mononuclear phagocyte system including monocytes/macrophages leading to the undesirable degradation of cargo in lysosomes. We took advantage of this default route to target macrophage lysosomes to rectify their acidity in disease states such as atherosclerosis. Herein, we develop and test two commonly used acidic nanoparticles, poly-lactide-co-glycolic acid (PLGA) and polylactic acid (PLA), both in vitro and in vivo. Our results in cultured macrophages indicate that the PLGA-based nanoparticles are the most effective at trafficking to and enhancing acidification of lysosomes. PLGA nanoparticles also provide functional benefits including enhanced lysosomal degradation, promotion of macroautophagy/autophagy and protein aggregate removal, and reduced apoptosis and inflammasome activation. We demonstrate the utility of this system in vivo, showing nanoparticle accumulation in, and lysosomal acidification of, macrophages in atherosclerotic plaques. Long-term administration of PLGA nanoparticles results in significant reductions in surrogates of plaque complexity with reduced apoptosis, necrotic core formation, and cytotoxic protein aggregates and increased fibrous cap formation. Taken together, our data support the use of acidic nanoparticles to rescue macrophage lysosomal dysfunction in the treatment of atherosclerosis.Abbreviations: BCA: brachiocephalic arteries; FACS: fluorescence activated cell sorting; FITC: fluorescein-5-isothiocyanatel; IL1B: interleukin 1 beta; LAMP: lysosomal associated membrane protein; LIPA/LAL: lipase A, lysosomal acid type; LSDs: lysosomal storage disorders; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MFI: mean fluorescence intensity; MPS: mononuclear phagocyte system; PEGHDE: polyethylene glycol hexadecyl ether; PLA: polylactic acid; PLGA: poly-lactide-co-glycolic acid; SQSTM1/p62: sequestosome 1.

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.

NVP-BEZ235 or JAKi Treatment leads to decreased survival of examined GBM and BBC cells

Cancer cells almost universally harbor constitutively active Phosphatidylinositol-3 Kinase (PI3K) Pathway activity via mutation of key signaling components and/or epigenetic mechanisms. Scores of PI3K Pathway inhibitors are currently under investigation as putative chemotherapeutics. However, feedback and stem cell mechanisms induced by PI3K Pathway inhibition can lead to reduced treatment efficacy. To address therapeutic barriers, we examined whether JAKi would reduce stem gene expression in a setting of PI3K Pathway inhibition in order to improve treatment efficacy. We targeted the PI3K Pathway with NVP-BEZ235 (dual PI3K and mTOR inhibitor) in combination with the Janus Kinase inhibitor JAKi in glioblastoma (GBM) and basal-like breast cancer (BBC) cell lines. We examined growth, gene expression, and apoptosis in cells treated with NVP-BEZ235 and/or JAKi. Growth and recovery assays showed no significant impact of dual treatment with NVP-BEZ235/JAKi compared to NVP-BEZ235 treatment alone. Gene expression and flow cytometry revealed that single and dual treatments induced apoptosis. Stem gene expression was retained in dual NVP-BEZ235/JAKi treatment samples. Future in vivo studies may give further insight into the impact of combined NVP-BEZ235/JAKi treatment in GBM and BBC.

Suppression of Esophageal Cancer Stem-like Cells by SNX-2112 Is Enhanced by STAT3 Silencing

Many studies have demonstrated that cancer stem cells (CSCs) or tumor-initiating cells (TICs) are responsible for tumor cell proliferation, chemotherapy resistance, metastasis, and relapse in various cancers. We, and others, have previously shown that the signal transducer and activator of transcription 3 (STAT3) signaling pathway is responsible for CSCs and TICs growth. Recent reports have indicated that the heat shock protein 90 (Hsp90) is also essential for the survival of CSCs and TICs. SNX-2112 is an Hsp90 inhibitor. However, it remains unclear whether proliferation of esophageal cancer stem-like cells (ECSLCs) is suppressed by SNX-2112 with knockdown of STAT3 (shSTAT3). Here, we explored the association between SNX-2112 with shSTAT3 and the suppression of ECSLCs growth. We found that the expression level of both STAT3 and p-STAT3 was higher in clinical esophageal cancer tissue than in the adjacent normal tissue, using western blot and qPCR analysis. Furthermore, differential expression analysis demonstrated that STAT3 was overexpressed in clinical specimens. We demonstrated that SNX-2112 inhibited cancer cell proliferation, decreased ABCB1 and ABCG2 gene expression levels and reduced the colony formation capacity of ECSLCs, which was enhanced by STAT3 silencing. Flow cytometry analysis revealed that the combination of SNX-2112 and shSTAT3 significantly induced apoptosis and cell cycle arrest at G2/M phase in ECSLCs. Levels of proliferation pathway proteins, including p38, c-Jun N-terminal kinase (JNK), and extracellular signal–regulated kinase (ERK) which were also client proteins of Hsp90, were also reduced. In addition, SNX-2112 with shSTAT3 inhibited the proliferation of ECSLCs in vivo. Finally, STAT3 overexpression eliminated the apoptotic and antiproliferative effects of SNX-2112 on ECSLCs. Hence, these results provide a rationale for the therapeutic potential of the combination of SNX-2112 with shSTAT3 in esophageal cancer, and may indicate new targets for clinical intervention in human cancer.

Drug Delivery Systems Using Surface Markers for Targeting Cancer Stem Cells

The innate abilities of cancer stem cells (CSCs), such as multi-drug resistance, drug efflux, quiescence and ionizing radiation tolerance, protect them from most traditional chemotherapeutics. As a result, this small subpopulation of persistent cells leads to more aggressive and chemoresistant cancers, causing tumour relapse and metastasis. This subpopulation is differentiated from the bulk tumour population through a wide variety of surface markers expressed on the cell surface. Recent developments in nanomedicine and targeting delivery methods have given rise to new possibilities for specifically targeting these markers and preferentially eliminating CSCs. Herein, we first summarize the range of surface markers identifying CSC populations in a variety of cancers; then, we discuss recent attempts to actively target CSCs and their niches using liposomal, nanoparticle, carbon nanotube and viral formulations.

Niclosamide-loaded polymeric micelles ameliorate hepatocellular carcinoma in vivo through targeting Wnt and Notch pathways

AIM

Niclosamide (NIC) is an anthelmintic agent repurposed as a potent anticancer agent. However, its use is hindered by its poor solubility. We investigated the underlying mechanisms of NIC anticancer activity employing a novel oral NIC pluronic-based nanoformulation and tested its effect in thioacetamide-induced hepatocellular carcinoma (HCC) in rats. We evaluated its antitumor effect through regulating Wnt/β-catenin and Notch signaling pathways and apoptosis.

MAIN METHODS

Niclosamide-loaded pluronic nanoparticles (NIC-NPs) were optimally developed and characterized with sustained release properties up to 7 days. Sixteen weeks after HCC induction, NIC (70 mg/kg) and an equivalent dose of NIC-NPs were administered orally for 3 consecutive weeks. Hepatocyte integrity was assessed by measuring serum levels of aminotransferases, ALP, GGT, bilirubin, albumin and total protein. HCC development was detected by measuring AFP expression. Necroinflammation and fibrosis were scored by histopathological examination. Wnt/β-catenin and Notch signaling were evaluated by measuring hepatic mRNA levels of Wnt3A, Lrp5 and Lrp6 Co-receptors, Dvl-2, Notch1 and Hes1 and β-catenin protein levels. Apoptosis was assessed by measuring mRNA and protein levels of cyclin D1 and caspase-3.

KEY FINDING

The novel NIC-NPs restored liver integrity, reduced AFP levels and showed improved anticancer and proapoptotic activities compared to drug alone. The inhibitory effect of NIC on Wnt/β-catenin and Notch signaling pathways was potentiated by the NIC-NPs formulation.

SIGNIFICANCE

We conclude that NIC acts by inhibiting Wnt/β-catenin and Notch signaling and inducing apoptosis in HCC. Developing pluronic-based nanoformulations may be a promising approach to improve NIC solubility and offer the possibility of controlled release.

Nanoliposomal Encapsulation Enhances In Vivo Anti-Tumor Activity of Niclosamide against Melanoma

BACKGROUND

Niclosamide is an FDA-approved and old anti-helminthic drug used to treat parasitic infections. Recent studies have shown that niclosamide has broad anti-tumor effects relevant to the treatment of cancer. However, this drug has a low aqueous solubility hindering its systemic use. Herein, we report the preparation and characterization of niclosamide nanoliposomes and their in vivo anti-tumor effects.

METHODS

Nanoliposomes were prepared using thin-film method and the drug was encapsulated with a remote loading method. The nanoliposomes were investigated by the observation of morphology, analysis of particle size and zeta potential. Additionally, qualitative and quantitative analyses were performed using HPLC. We assessed the in vitro cytotoxicity of the nanoliposomal niclosamide on B16F10 melanoma cells. Inhibition of tumor growth was investigated in C57BL/6 mice bearing B16F0 melanoma cancer.

RESULTS

Analytical results indicated that the nanoliposomal system is a homogeneous and stable colloidal dispersion of niclosamide particles. Atomic force microscopy images and particle size analysis revealed that all niclosamide particles had a spherical shape with a diameter of approximately 108nm. According to in vitro and in vivo studies, nanoliposomal niclosamide exhibited a better anti-tumor activity against B16F10 melanoma tumor compared with free niclosamide.

CONCLUSION

Nanoliposomal encapsulation enhanced the aqueous solubility of niclosamide and improved its anti-tumor properties.

Nanoparticles Targeting STATs in Cancer Therapy

Over the past decades, an increase in the incidence rate of cancer has been witnessed. Although many efforts have been made to manage and treat this life threatening condition, it is still one of the leading causes of death worldwide. Therefore, scientists have attempted to target molecular signaling pathways involved in cancer initiation and metastasis. It has been shown that signal transducers and activator of transcription (STAT) contributes to the progression of cancer cells. This important signaling pathway is associated with a number of biological processes including cell cycle, differentiation, proliferation and apoptosis. It appears that dysregulation of the STAT signaling pathway promotes the migration, viability and malignancy of various tumor cells. Hence, there have been many attempts to target the STAT signaling pathway. However, it seems that currently applied therapeutics may not be able to effectively modulate the STAT signaling pathway and suffer from a variety of drawbacks such as low bioavailability and lack of specific tumor targeting. In the present review, we demonstrate how nanocarriers can be successfully applied for encapsulation of STAT modulators in cancer therapy.

Evaluation of the Anti-Tumor Activity of Niclosamide Nanoliposomes Against Colon Carcinoma

BACKGROUND AND AIMS

Niclosamide is an established anti-helminthic drug, which has recently been shown to inhibit the growth of various cancer cells. To exploit the potential anti-tumor activity of this drug for systemic use, the problem of low aqueous solubility should be addressed. The present study tested the in vivo anti-tumor effects of a recently developed nanoliposomal preparation of niclosamide in an experimental model of colon carcinoma.

METHODS

The cytotoxicity of nanoliposomal niclosamide on CT26 colon carcinoma cells was evaluated using the MTT test. Inhibition of tumor growth was investigated in BALB/c mice bearing CT26 colon carcinoma cells. The animals were randomly divided into 4 groups including: 1) untreated control, 2) liposomal doxorubicin (15 mg/kg; single intravenous dose), 3) liposomal niclosamide (1 mg/kg/twice a week; intravenously for 4 weeks), and 4) free niclosamide (1 mg/kg/twice a week; intravenously for 4 weeks). To study therapeutic efficacy, tumor size and survival were monitored in 2-day intervals for 40 days.

RESULTS

In vitro results indicated that nanoliposomal and free niclosamide could exert cytotoxic effects with IC50 values of 4.5 and 2.5 μM, respectively. According to in vivo studies, nanoliposomal niclosamide showed a higher growth inhibitory activity against CT26 colon carcinoma cells compared with free niclosamide as revealed by delayed tumor growth and prolongation of survival.

CONCLUSION

Nnaoliposomal encapsulation enhanced anti-tumor properties of niclosamide in an experimental model of colon carcinoma.

Niclosamide repositioning for treating cancer: Challenges and nano-based drug delivery opportunities

Drug repositioning may be defined as a process when new biological effects for known drugs are identified, leading to recommendations for new therapeutic applications. Niclosamide, present in the Model List of Essential Medicines, from the World Health Organization, has been used since the 1960s for tapeworm infection. Several preclinical studies have been shown its impressive anticancer effects, which led to clinical trials for colon and prostate cancer. Despite high expectations, proof of efficacy and safety are still required, which are associated with diverse biopharmaceutical challenges, such as the physicochemical properties of the drug and its oral absorption, and their relationship with clinical outcomes. Nanostructured systems are innovative drug delivery strategies, which may provide interesting pharmaceutical advantages for this candidate. The aim of this review is to discuss challenges involving niclosamide repositioning for cancer diseases, and the opportunities of therapeutic benefits from nanosctrutured system formulations containing this compound.

Niclosamide Induces Cell Cycle Arrest in G1 Phase in Head and Neck Squamous Cell Carcinoma Through Let-7d/CDC34 Axis

Niclosamide is a traditional anti-tapeworm drug that exhibits potent anti-cancer activity. Our previous study showed that niclosamide induces cell cycle arrest in G1 phase. Nevertheless, the underlying mechanism remains unknown. The following study investigated the molecular mechanism through which niclosamide induced G1 arrest in head and neck squamous cell carcinoma (HNSCC) cell lines. The effect of niclosamide on human HNSCC cell line WSU-HN6 and CNE-2Z were analyzed using IncuCyte ZOOM^TM assay, flow cytometry (FCM), real-time PCR and western blot. Luciferase assay was conducted to demonstrate the interaction between let-7d (a let-7 family member which functions as a tumor suppressor by regulating cell cycle) and 3′UTR of CDC34 mRNA. Xenografts tumor model was established to evaluate the niclosamide treatment efficacy in vivo. Briefly, an exposure to niclosamide treatment led to an increased let-7d expression and a decreased expression of cell cycle regulator CDC34, finally leading to G1 phase arrest. Moreover, an overexpression of let-7d induced G1 phase arrest and downregulated CDC34, while the knockdown of let-7d partially rescued the niclosamide-induced G1 phase arrest. Luciferase assay confirmed the direct inhibition of CDC34 through the targeting of let-7d. Furthermore, niclosamide markedly inhibited the xenografts growth through up-regulation of let-7d and down-regulation of CDC34. To sum up, our findings suggest that niclosamide induces cell cycle arrest in G1 phase in HNSCC through let-7d/CDC34 axis, which enriches the anti-cancer mechanism of niclosamide.

RON Receptor Tyrosine Kinase as a Therapeutic Target for Eradication of Triple-Negative Breast Cancer: Efficacy of Anti-RON ADC Zt/g4-MMAE

Triple-negative breast cancer (TNBC) is a highly diverse group of malignant neoplasia with poor outcome. Currently, the lack of effective therapy has fostered a major effort to discover new targets to treat this malignant cancer. Here we identified the RON receptor tyrosine kinase as a therapeutic target for potential TNBC treatment. We analyzed RON expression in 168 primary TNBC samples via tissue microarray using anti-RON IHC staining and demonstrated that RON was widely expressed in 76.8% TNBC samples with overexpression in 76 cases (45.2%). These results provide the molecular basis to target RON for TNBC therapy. To this end, anti-RON monoclonal antibody Zt/g4-drug monomethyl auristatin E conjugate (Zt/g4-MMAE) was developed with a drug to antibody ratio of 3.29 and tested in a panel of TNBC cell lines with different phenotypes. In vitro, Zt/g4-MMAE rapidly induced RON internalization, resulted in cell-cycle arrest followed by massive cell death. The calculated IC₅₀ values ranged from 0.06 to 3.46 μg/mL dependent on individual TNBC cell lines tested. Zt/g4-MMAE also effectively killed TNBC stem-like cells with RON⁺/CD44⁺/CD24^- phenotypes and RON-negative TNBC cells through the bystander effect. In vivo, Zt/g4-MMAE at 10 mg/kg in a Q12 × 2 regimen completely eradicated TNBC xenografts without the regrowth of xenograft tumors. In conclusion, increased RON expression is a pathogenic feature in primary TNBC samples. Zt/g4-MMAE is highly effective in eradicating TNBC xenografts in preclinical models. These findings lay the foundation for using anti-RON Zt/g4-MMAE in clinical trials as a novel strategy for TNBC treatment.

Silibinin is a direct inhibitor of STAT3

We herein combined experimental and computational efforts to delineate the mechanism of action through which the flavonolignan silibinin targets STAT3. Silibinin reduced IL-6 inducible, constitutive, and acquired feedback activation of STAT3 at tyrosine 705 (Y705). Silibinin attenuated the inducible phospho-activation of Y705 in GFP-STAT3 genetic fusions without drastically altering the kinase activity of the STAT3 upstream kinases JAK1 and JAK2. A comparative computational study based on docking and molecular dynamics simulation over 14 different STAT3 inhibitors (STAT3i) predicted that silibinin could directly bind with high affinity to both the Src homology-2 (SH2) domain and the DNA-binding domain (DBD) of STAT3. Silibinin partially overlapped with the cavity occupied by other STAT3i in the SH2 domain to indirectly prevent Y705 phosphorylation, yet showing a unique binding mode. Moreover, silibinin was the only STAT3i predicted to establish direct interactions with DNA in its targeting to the STAT3 DBD. The prevention of STAT3 nuclear translocation, the blockade of the binding of activated STAT3 to its consensus DNA sequence, and the suppression of STAT3-directed transcriptional activity confirmed silibinin as a direct STAT3i. The unique characteristics of silibinin as a bimodal SH2- and DBD-targeting STAT3i make silibinin a promising lead for designing new, more effective STAT3i.