Clinico-Immunological Effects of a Single-Agent CDK4/6 Inhibitor in Advanced HR+/HER2− Breast Cancer Based on a Window of Opportunity Study

Background: Cyclin-dependent kinase 4/6 inhibitors (CDK4/6 i), abemaciclib, palbociclib, and ribociclib, have been FDA-approved for the treatment of hormone receptor-positive (HR+), HER2−negative (HER2−) advanced breast cancer (aBC). This targeted therapy has revived hope in those aBC patients who did not respond to standard therapies. Interestingly, when administered as a single agent, CDK4/6 modulated several peripheral blood cells after a short-course treatment of 28 days. However, the impact of these immune effects has yet to be thoroughly investigated. Methods: We administered abemaciclib, palbociclib, and ribociclib monotherapy to 23 patients with HR+/HER2− metastatic breast cancer. The aim is to investigate the impact of on-treatment modifications on peripheral blood cells and their composite scores in patients after a 28-day course of CDK4/6 i alone. Results: In the current study, we observed a significant decrease in neutrophils (p-value < 0.001) for patients treated with abemaciclib, palbociclib, and ribociclib. An overall decrease of T_regs was observed and potentially linked to palbociclib treatment. The neutrophile to lymphocyte (N/L) ratio was also decreased overall and potentially linked to abemaciclib and palbociclib treatment. Platelets were decreased in patients administered with abemaciclib. Notably, the radiometabolic response was available only for those patients treated with ribociclib and abemaciclib, and only those lesions treated with ribociclib reached statistical relevance. Conclusions: Our study strongly supports the notion that CDK4/6 inhibitors induce tumour immune modulation. N/L ratio and platelet levels decreased due to treatment. Future studies should test whether patients would benefit from immunomodulators in association with CDK4/6 agents in a larger clinical trial. Moreover, the CDK4/6-induced immune modulation could also be considered a potential predictive clinical factor in HR+/HER2− advanced breast cancer.     

Thermal proteome profiling of breast cancer cells reveals proteasomal activation by CDK4/6 inhibitor palbociclib

Palbociclib is a CDK4/6 inhibitor approved for metastatic estrogen receptor‐positive breast cancer. In addition to G1 cell cycle arrest, palbociclib treatment results in cell senescence, a phenotype that is not readily explained by CDK4/6 inhibition. In order to identify a molecular mechanism responsible for palbociclib‐induced senescence, we performed thermal proteome profiling of MCF7 breast cancer cells. In addition to affecting known CDK4/6 targets, palbociclib induces a thermal stabilization of the 20S proteasome, despite not directly binding to it. We further show that palbociclib treatment increases proteasome activity independently of the ubiquitin pathway. This leads to cellular senescence, which can be counteracted by proteasome inhibitors. Palbociclib‐induced proteasome activation and senescence is mediated by reduced proteasomal association of ECM29. Loss of ECM29 activates the proteasome, blocks cell proliferation, and induces a senescence‐like phenotype. Finally, we find that ECM29 mRNA levels are predictive of relapse‐free survival in breast cancer patients treated with endocrine therapy. In conclusion, thermal proteome profiling identifies the proteasome and ECM29 protein as mediators of palbociclib activity in breast cancer cells.     

Resistance to CDK4/6 inhibition: Mechanisms and strategies to overcome a therapeutic problem in the treatment of hormone receptor-positive metastatic breast cancer

Selective CDK4/6 inhibitors, such as palbociclib, ribociclib, and abemaciclib, have been approved in combination with hormone therapy for the treatment of patients with HR+, HER2-negative advanced or metastatic breast cancer (mBC). Despite their promising activity, approximately 10 % of patients have de novo resistance, while the rest of them will develop acquired resistance after 24–28 months when used as first-line therapy and after a shorter period when used as second-line therapy. Various mechanisms of resistance to CDK4/6 inhibitors have been described, including cell cycle-related mechanisms, such as RB loss, p16 amplification, CDK6 or CDK4 amplification, and cyclin E-CDK2 amplification. Other bypass mechanisms involve the activation of FGFR or PI3K/AKT/mTOR pathways. Identifying the different mechanisms by which resistance to CDK4/6 inhibitors occurs may help to design new treatment strategies to improve patient outcomes. This review presents the currently available knowledge on the mechanisms of resistance to CDK4/6 inhibitors, explores possible treatment strategies that could overcome this therapeutic problem, and summarizes relevant recent clinical trials.     

Efficacy of a combination therapy targeting CDK4/6 and autophagy in a mouse xenograft model of t(8;21) acute myeloid leukemia

One of the most frequent cytogenetic abnormalities in acute myeloid leukemia (AML) is t(8;21). Although patients with t(8;21) AML have a more favorable prognosis than other cytogenetic subgroups, relapse is still common and novel therapeutic approaches are needed. A recent study showed that t(8;21) AML is characterized by CCND2 deregulation and that co-inhibition of CDK4/6 and autophagy induces apoptosis in t(8;21) AML cells. In this study, we examined the in vivo effects of co-inhibiting CDK4/6 and autophagy. We used a mouse model in which t(8;21)-positive Kasumi-1 cells were subcutaneously inoculated into NOD/Shi-scid IL2Rg^null mice. The mice were treated with the autophagy inhibitor chloroquine (CQ), a CDK4/6 inhibitor (either abemaciclib or palbociclib), or a CDK4/6 inhibitor plus CQ. After 20 days of treatment, tumor volume was measured, and immunostaining and transmission electron microscopy observations were performed. There was no change in tumor growth in CQ-treated mice. However, mice treated with a CDK4/6 inhibitor plus CQ had significantly less tumor growth than mice treated with a CDK4/6 inhibitor alone. CDK4/6 inhibitor treatment increased the formation of autophagosomes. The number of single-strand DNA-positive (apoptotic) cells was significantly higher in the tumors of mice treated with a CDK4/6 inhibitor plus CQ than in mice treated with either CQ or a CDK4/6 inhibitor. These results show that CDK4/6 inhibition induces autophagy, and that co-inhibition of CDK4/6 and autophagy induces apoptosis in t(8;21) AML cells in vivo. The results suggest that inhibiting CDK4/6 and autophagy could be a novel and promising therapeutic strategy in t(8;21) AML.     

Design of a brain-penetrant CDK4/6 inhibitor for glioblastoma

CDK4 and CDK6 are kinases with similar sequences that regulate cell cycle progression and are validated targets in the treatment of cancer. Glioblastoma is characterized by a high frequency of CDKN2A/CCND2/CDK4/CDK6 pathway dysregulation, making dual inhibition of CDK4 and CDK6 an attractive therapeutic approach for this disease. Abemaciclib, ribociclib, and palbociclib are approved CDK4/6 inhibitors for the treatment of HR+/HER2? breast cancer, but these drugs are not expected to show strong activity in brain tumors due to poor blood brain barrier penetration. Herein, we report the identification of a brain-penetrant CDK4/6 inhibitor derived from a literature molecule with low molecular weight and topological polar surface area (MW = 285 and TPSA = 66 Ų), but lacking the CDK2/1 selectivity profile due to the absence of a basic amine. Removal of a hydrogen bond donor via cyclization of the pyrazole allowed for the introduction of basic and semi-basic amines, while maintaining in many cases efflux ratios reasonable for a CNS program. Ultimately, a basic spiroazetidine (cpK_a = 8.8) was identified that afforded acceptable selectivity over anti-target CDK1 while maintaining brain-penetration in vivo (mouse K_p,uu = 0.20–0.59). To probe the potency and selectivity, our lead compound was evaluated in a panel of glioblastoma cell lines. Potency comparable to abemaciclib was observed in Rb-wild type lines U87MG, DBTRG-05MG, A172, and T98G, while Rb-deficient cell lines SF539 and M059J exhibited a lack of sensitivity.     

Mitotic Checkpoint Kinase Mps1 Has a Role in Normal Physiology which Impacts Clinical Utility

Cell cycle checkpoint intervention is an effective therapeutic strategy for cancer when applied to patients predisposed to respond and the treatment is well-tolerated. A critical cell cycle process that could be targeted is the mitotic checkpoint (spindle assembly checkpoint) which governs the metaphase-to-anaphase transition and insures proper chromosomal segregation. The mitotic checkpoint kinase Mps1 was selected to explore whether enhancement in genomic instability is a viable therapeutic strategy. The basal-a subset of triple-negative breast cancer was chosen as a model system because it has a higher incidence of chromosomal instability and Mps1 expression is up-regulated. Depletion of Mps1 reduces tumor cell viability relative to normal cells. Highly selective, extremely potent Mps1 kinase inhibitors were created to investigate the roles of Mps1 catalytic activity in tumor cells and normal physiology (PF-7006, PF-3837; K _i<0.5 nM; cellular IC₅₀ 2–6 nM). Treatment of tumor cells in vitro with PF-7006 modulates expected Mps1-dependent biology as demonstrated by molecular and phenotypic measures (reduced pHH3-Ser₁₀ levels, shorter duration of mitosis, micro-nucleation, and apoptosis). Tumor-bearing mice treated with PF-7006 exhibit tumor growth inhibition concomitant with pharmacodynamic modulation of a downstream biomarker (pHH3-Ser₁₀). Unfortunately, efficacy only occurs at drug exposures that cause dose-limiting body weight loss, gastrointestinal toxicities, and neutropenia. Mps1 inhibitor toxicities may be mitigated by inducing G₁ cell cycle arrest in Rb1-competent cells with the cyclin-dependent kinase-4/6 inhibitor palbociclib. Using an isogenic cellular model system, PF-7006 is shown to be selectively cytotoxic to Rb1-deficient cells relative to Rb1-competent cells (also a measure of kinase selectivity). Human bone marrow cells pretreated with palbociclib have decreased PF-7006-dependent apoptosis relative to cells without palbociclib pretreatment. Collectively, this study raises a concern that single agent therapies inhibiting Mps1 will not be well-tolerated clinically but may be when combined with a selective CDK4/6 drug.     

CDK4/6 inhibitor protects chemerin‐induced human granulosa‐lutein cells from apoptosis by inhibiting the p53/p21 waf pathway

Dysregulation of the cell cycle is common in human tumorigenesis. Therefore, CDK4/6 inhibitors targeting the cell cycle have been developed, and their antiapoptotic effects have been highly correlated with potential clinical therapies. The aim of this study was to identify the regulatory effect of the CDK4/6 inhibitor palbociclib on chemerin‐induced apoptosis of immortalized human granulosa‐lutein (hGL) cells and to elucidate its fundamental mechanism of action. Palbociclib enhanced antioxidative enzyme generation and diminished ROS generation in hGL cells. Furthermore, we found that palbociclib suppressed chemerin‐induced apoptotic protein expression, reversing the Bcl‐2/Bax ratio and inhibiting the p53/p21 ^waf pathway. Eventually, palbociclib decreased the level of cleaved caspase‐3 and ‐9, hindering the apoptosis of hGL cells. In general, the antiapoptotic efficacy of palbociclib could be attributed in part to the modulation of the mitochondrial apoptotic pathway in hGL cells.     

Palbociclib (PD 0332991) Interaction with Kinases. Theoretical and Comparative Molecular Docking Study

The optimized geometry of palbociclib, (PD 0332991) (8-cyclopentyl-6-ethanoyl-5-methyl-2-(5-(piperazin-1-yl)pyridin-2-ylamino)pyrido[2,3-d]pyrimidin-7(8H)-one), electrostatic potential map, molecular orbitals were calculated using the density functional theory. The geometry was used in a molecular docking study of palbociclib-kinase complexes, results could be explained by the charge of the nitrogen and oxygen atoms within the palbociclib. Energy gap of HOMO-LUMO surfaces, could help to explain the reactivity of the ligand and the hydrogen bonding with three different kinases, two of CDK6 and one of CDK4 type. Docking results are similar and complementary with literature reports using molecular dynamics, were hydrogen bonding was obtained and analyzed. The promiscuity of three kinases with palbociclib was detected by the docking results, thus, palbociclib could be used in other types of cancer besides myeloid leukemia. Some similarities are found with CDK4/CDK6 kinases which allow us to determine that palbociclib could be used to control other resistant inhibitor types of cancer.     

Palbociclib can overcome mutations in cyclin dependent kinase 6 that break hydrogen bonds between the drug and the protein

Inhibition of cyclin dependent kinases (CDKs) 4 and 6 prevent cells from entering the synthesis phase of the cell cycle. CDK4 and 6 are therefore important drug targets in various cancers. The selective CDK4/6 inhibitor palbociclib is approved for the treatment of breast cancer and has shown activity in a cellular model of mixed lineage leukaemia (MLL)‐rearranged acute myeloid leukaemia (AML). We studied the interactions of palbociclib and CDK6 using molecular dynamics simulations. Analysis of the simulations suggested several interactions that stabilized the drug in its binding site and that were not observed in the crystal structure of the protein‐drug complex. These included a hydrogen bond to His 100 that was hitherto not reported and several hydrophobic contacts. Evolutionary‐based bioinformatic analysis was used to suggest two mutants, D163G and H100L that would potentially yield drug resistance, as they lead to loss of important protein–drug interactions without hindering the viability of the protein. One of the mutants involved a change in the glycine of the well‐conserved DFG motif of the kinase. Interestingly, CDK6‐dependent human AML cells stably expressing either mutant retained sensitivity to palbociclib, indicating that the protein‐drug interactions are not affected by these. Furthermore, the cells were proliferative in the absence of palbociclib, indicating that the Asp to Gly mutation in the DFG motif did not interfere with the catalytic activity of the protein.     

Increased radiation toxicity with germline ATM variant of uncertain clinical significance

BackgroundWhile patients with ataxia telangiectasia are known to have increased radiation sensitivity, patients with germline heterozygous ataxia telangiectasia mutated (ATM) mutations can have widely varying functional and clinical effects, which can make management decisions difficult. With an increased prevalence of gene panel-based testing for breast cancer patients, radiation oncologists are increasingly confronted with patients who carry germline ATM variants of uncertain clinical significance. This study describes the clinical courses and outcomes of 5 breast cancer patients with varying germline heterozygous ATM mutations undergoing radiation therapy at our institution in order to provide additional knowledge of the varying clinical effects to aid future decision making.Case SeriesWe identified 5 patients with breast cancer and varying germline heterozygous ATM mutations treated at the University of North Carolina Hospitals between 2015 and 2017. The median age at breast cancer diagnosis for the patient series was 46. Clinical effects of radiation treatment varied amongst the 5 patients. The one patient with a pathogenic ATM mutation had no increased radiation related toxicity. Of the 4 patients with ATM variants of uncertain significance, one patient had increased radiation sensitivity with Grade 3 dermatitis. All patients have remained recurrence free with a median duration of 18 months.ConclusionOur data illustrates that patients with germline heterozygous ATM mutations can have widely varying clinical effects with radiation therapy. Given the possibility of unpredictable deleterious effects, our study highlights the importance of caution and careful consideration when devising the multi-modality management strategy in these patients.     

RB-E2F信号通路与乳腺癌及其治疗

视网膜母细胞瘤基因（retinoblastoma gene, RB1）突变或调节CDK-RB-E2F通路其他成分的突变存在于几乎所有人类恶性肿瘤中。因此,通过抑制细胞周期蛋白激酶（CDK）来实现对细胞周期的调控,在肿瘤治疗中越来越显示出其优势。目前,CDK4/6抑制剂帕博西尼（palbociclib）联合芳香酶抑制剂,治疗ER 阳性乳腺癌是很有效的临床应用。研究显示,CDK-RB-E2F信号通路,对控制乳腺细胞增殖发挥关键作用。近期的研究结果,揭示了该通路在肿瘤发展、血管生成及转移中的作用。并且,E2Fs是不依赖于其他临床参数的乳腺癌预后指标。本综述总结了乳腺癌中RB E2F通路的最新研究进展,并且讨论应用高通量基因组学研究,筛选获得乳腺癌中CDK4/6抑制剂重要的作用靶点,旨在发展更有效的联合治疗手段。     

Genome wide CRISPR/Cas9 screen identifies the coagulation factor IX (F9) as a regulator of senescence

During this last decade, the development of prosenescence therapies has become an attractive strategy as cellular senescence acts as a barrier against tumour progression. In this context, CDK4/6 inhibitors induce senescence and reduce tumour growth in breast cancer patients. However, even though cancer cells are arrested after CDK4/6 inhibitor treatment, genes regulating senescence in this context are still unknown limiting their antitumour activity. Here, using a functional genome-wide CRISPR/Cas9 genetic screen we found several genes that participate in the proliferation arrest induced by CDK4/6 inhibitors. We find that downregulation of the coagulation factor IX (F9) using sgRNA and shRNA prevents the cell cycle arrest and senescent-like phenotype induced in MCF7 breast tumour cells upon Palbociclib treatment. These results were confirmed using another breast cancer cell line, T47D, and with an alternative CDK4/6 inhibitor, Abemaciclib, and further tested in a panel of 22 cancer cells. While F9 knockout prevents the induction of senescence, treatment with a recombinant F9 protein was sufficient to induce a cell cycle arrest and senescence-like state in MCF7 tumour cells. Besides, endogenous F9 is upregulated in different human primary cells cultures undergoing senescence. Importantly, bioinformatics analysis of cancer datasets suggest a role for F9 in human tumours. Altogether, these data collectively propose key genes involved in CDK4/6 inhibitor response that will be useful to design new therapeutic strategies in personalised medicine in order to increase their efficiency, stratify patients and avoid drug resistance.Subject terms: Senescence, Tumour biomarkers     

Aiduqing formula suppresses breast cancer metastasis via inhibiting CXCL1-mediated autophagy

BackgroundMetastasis is the most common lethal cause of breast cancer-related death. Recent studies have implied that autophagy is closely implicated in cancer metastasis. Therefore, it is of great significance to explore autophagy-related molecular targets involved in breast cancer metastasis and to develop therapeutic drugs.PurposeThis study was designed to investigate the anti-metastatic effects and autophagy regulatory mechanisms of Aiduqing (ADQ) formula on breast cancer.Study Design/MethodsMultiple cellular and molecular experiments were conducted to investigate the inhibitory effects of ADQ formula on autophagy and metastasis of breast cancer cells in vitro. Meanwhile, autophagic activator/inhibitor as well as CXCL1 overexpression or interference plasmids were used to investigate the underlying mechanisms of ADQ formula in modulating autophagy-mediated metastasis. Furthermore, the zebrafish xenotransplantation model and mouse xenografts were applied to validate the inhibitory effect of ADQ formula on autophagy-mediated metastasis in breast cancer in vivo.ResultsADQ formula significantly inhibited the proliferation, migration, invasion and autophagy but induced apoptosis of high-metastatic breast cancer cells in vitro. Similar results were also observed in starvation-induced breast cancer cells which exhibited elevated metastatic ability and autophagy activity. Mechanism investigations further approved that either CXCL1 overexpression or autophagic activator rapamycin can significantly abrogated the anti-metastatic effects of ADQ formula, suggesting that CXCL1-mediated autophagy may be the crucial pathway of ADQ formula in suppressing breast cancer metastasis. More importantly, ADQ formula suppressed breast cancer growth, autophagy, and metastasis in both the zebrafish xenotransplantation model and the mouse xenografts.ConclusionOur study not only revealed the novel function of CXCL1 in mediating autophagy-mediated metastasis but also suggested ADQ formula as a candidate drug for the treatment of metastatic breast cancer.     

Silencing CDK4 radiosensitizes breast cancer cells by promoting apoptosis

Background

The discovery of molecular markers associated with various breast cancer subtypes has greatly improved the treatment and outcome of breast cancer patients. Unfortunately, breast cancer cells acquire resistance to various therapies. Mounting evidence suggests that resistance is rooted in the deregulation of the G1 phase regulatory machinery.

Methods

To address whether deregulation of the G1 phase regulatory machinery contributes to radiotherapy resistance, the MCF10A immortalized human mammary epithelial cell line, ER-PR-Her2+ and ER-PR-Her2- breast cancer cell lines were irradiated. Colony formation assays measured radioresistance, while immunocytochemistry, Western blots, and flow cytometry measured the cell cycle, DNA replication, mitosis, apoptosis, and DNA breaks.

Results

Molecular markers common to all cell lines were overexpressed, including cyclin A1 and cyclin D1, which impinge on CDK2 and CDK4 activities, respectively. We addressed their potential role in radioresistance by generating cell lines stably expressing small hairpin RNAs (shRNA) against CDK2 and CDK4. None of the cell lines knocked down for CDK2 displayed radiosensitization. In contrast, all cell lines knocked down for CDK4 were significantly radiosensitized, and a CDK4/CDK6 inhibitor sensitized MDA-MB-468 to radiation induced apoptosis. Our data showed that silencing CDK4 significantly increases radiation induced cell apoptosis in cell lines without significantly altering cell cycle progression, or DNA repair after irradiation. Our results indicate lower levels of phospho-Bad at ser136 upon CDK4 silencing and ionizing radiation, which has been shown to signal apoptosis.

Conclusion

Based on our data we conclude that knockdown of CDK4 activity sensitizes breast cancer cells to radiation by activating apoptosis pathways.

     

Mechanisms of abemaciclib,a CDK4/6 inhibitor,induced apoptotic cell death in prostate cancer cells in vitro

The therapeutic effects of abemaciclib (ABE), an inhibitor of cyclin- dependent kinases (CDK) 4/6, on the proliferation of two types of prostate cancer (PC) cells were revealed. In this study, in vitro cytotoxic and apoptotic effects of ABE on metastatic castration-resistant prostate cancer (mCRPC) androgen receptor (AR) negative PC-3 and AR mutant LNCaP PC cells were analyzed with WST-1, Annexin V, cell cycle, reactive oxygen species (ROS), mitochondrial membrane potential, RT-PCR, western blot, and apoptosis protein array. ABE considerably inhibited the growth of PC cells in a dose-dependent manner (p<0.01) and caused significant apoptotic cell death through the suppression of CDK4/6-Cyclin D complex, ROS generation and depolarization of mitochondria membrane potential. However, PC-3 cells were more sensitive to ABE than LNCaP cells. Furthermore, the expression levels of several pro-apoptotic and cell cycle regulatory proteins were upregulated by ABE in especially PC-3 cells with the downregulation of apoptotic inhibitor proteins. Our results suggest that ABE inhibits PC cell growth and promotes apoptosis and thus ABE treatment may be a promising treatment strategy in especially mCRPC. Further preclinical and clinical studies should be performed to clarify the clinical use of ABE for the treatment of PC.     

The CDK4/6 inhibitor palbociclib synergizes with irinotecan to promote colorectal cancer cell death under hypoxia

Hypoxia is an inherent impediment to cancer therapy. Palbociclib, a highly selective inhibitor for CDK4/6, has been tested in numerous clinical trials and has been approved by the FDA. We previously reported that CDK inhibitors can destabilize HIF1α regardless of the presence of hypoxia and can sensitize tumor cells to TRAIL through dual blockade of CDK1 and GSK-3β. To translate this knowledge into a cancer therapeutic strategy, we investigated the therapeutic effects and molecular mechanisms of CDK inhibition against colon cancer cells under normoxia and hypoxia. We found that palbociclib sensitizes colon cancer cells to hypoxia-induced apoptotic resistance via deregulation of HIF-1α accumulation. In addition to inhibition of cell proliferation, we observed that palbociclib promotes colon cancer cell death regardless of the presence of hypoxia at a comparatively high concentration via regulating ERK/GSK-3β signaling and GSK-3β expression. Furthermore, palbociclib synergized with irinotecan in a variety of colon cancer cell lines with various molecular subtypes via deregulating irinotecan-induced Rb phosphorylation and reducing HIF-1α accumulation under normoxia or hypoxia. Collectively, our findings provide a novel combination therapy strategy against hypoxic colon cancer cells that may be further translated in the clinic.     

Sanguinarine impedes metastasis and causes inversion of epithelial to mesenchymal transition in breast cancer

BackgroundA large number of breast cancer patients perishes due to metastasis instead of primary tumor, but molecular mechanisms contributing towards cancer metastasis remain poorly understood. Therefore, prompting development of novel treatment is inevitable. A vast variety of plant derived natural substance possesses several therapeutically active constituents, e.g. alkaloids, flavonoids, tannins, resins, terpenoids etc. that exhibit various pharmacological properties e.g. anti-inflammatory, anti-microbial and anti-cancer properties. Sanguinarine (SAN) alkaloid found its place among such naturally occurring substances that exerts several pharmacological activities, including anti-cancer effects.PurposeUntil now, role of SAN not only against epithelial-mesenchymal transition (EMT) but also against metastasis progression in breast cancer remains indistinct. Thus, aim of the present study was to investigate effects of SAN on EMT process and cancer metastasis in animal model.MethodsMTT assay was performed to assess SAN effects on proliferation in breast cancer. Scratch assay was performed to evaluate effects of SAN on migration in breast cancer. Colony formation assay was performed to determine effects of SAN on colonization characteristics of breast cancer. Western blotting was performed to measure EMT regulating protein expression as well as major pathway protein expression induced against TGF-β treatment in breast cancer. Tail vein method of injecting breast cancer cells in bulb/c mice was conducted to study metastasis progression and thereafter assessing effects of SAN against metastasis in mice.ResultsIn vivo results: MTT assay performed, demonstrated dose dependent inhibition of cell proliferation in breast cancer. Scratch assay results showed, SAN played a major role as migration inhibitor in estrogen receptor positive (ER+) breast cancer. Colony forming assay results demonstrated that SAN constrains ability of breast cancer to develop into well-defined colonies. Western blotting results for EMT regulating protein expression, after TGF-β treatment showed, SAN inhibited cadherin switch in ER+ breast cancer. Moreover, expression of pathway proteins involved in EMT process after TGF-β treatment i.e. Smad, PI3K/Akt and MAP kinase were significantly masked against SAN treatment.In vivo resultsThe appearance of metastatic nodules in lung tissues of mice model, helps to study the effects of SAN against metastasis in bulb/c mice. The obtained results have confirmed that SAN impeded lung metastasis. The macroscopic examination has confirmed metastasis inhibitory role of SAN in breast cancer. The Hematoxylin and eosin (H&E) staining results further advocate anti-metastatic characteristics of SAN, presented by fewer metastatic nodule and lesions appearance in SAN treated mice compared to untreated metastasis mice.ConclusionIn summary, SAN displayed prominent anti-metastatic effects in animal model and anti-proliferation effects together with significant inhibitory potential on EMT regulating protein expression against TGF-β treatment in ER+ breast cancer. So, overall findings of our study highlighted the pre-clinical significance of SAN in animal model therefore, further studies in humans as a part of clinical trial will be needed to establish pharmacokinetics and other effects of SAN, so that it can be a potential candidate for future treatment of metastatic breast cancer (MBC).