Paclitaxel-resistant Triple-negative Breast Cancer Research Articles

A chemical screen identifies PRMT5 as a therapeutic vulnerability for paclitaxel-resistant triple-negative breast cancer.

Paclitaxel-resistant triple negative breast cancer (TNBC) remains one of the most challenging breast cancers to treat. Here, using an epigenetic chemical probe screen, we uncover an acquired vulnerability of paclitaxel-resistant TNBC cells to protein arginine methyltransferases (PRMTs) inhibition. Analysis of cell lines and in-house clinical samples demonstrates that resistant cells evade paclitaxel killing through stabilizing mitotic chromatin assembly. Genetic or pharmacologic inhibition of PRMT5 alters RNA splicing, particularly intron retention of aurora kinases B (AURKB), leading to a decrease in protein expression, and finally results in selective mitosis catastrophe in paclitaxel-resistant cells. In addition, type I PRMT inhibition synergies with PRMT5 inhibition in suppressing tumor growth of drug-resistant cells through augmenting perturbation of AURKB-mediated mitotic signaling pathway. These findings are fully recapitulated in a patient-derived xenograft (PDX) model generated from a paclitaxel-resistant TNBC patient, providing the rationale for targeting PRMTs in paclitaxel-resistant TNBC.

IRE1α inhibitor enhances paclitaxel sensitivity of triple-negative breast cancer cells.

Breast cancer is the most commonly diagnosed cancer in women, and triple-negative breast cancer (TNBC) accounts for approximately 15%-20% of all breast cancers. TNBC is highly invasive and malignant. Due to the lack of relevant receptor markers, the prognosis of TNBC is poor and the five-year survival rate is low. Paclitaxel is the first-line drug for the treatment of TNBC, which can inhibit cell mitosis. However, many patients develop drug resistance during treatment, leading to chemotherapy failure. Therefore, finding new therapeutic combinations to overcome TNBC drug resistance can provide new strategies for improving the survival rate of TNBC patients. Cell viability assay, RT-qPCR, Colony formation assay, Western blot, and Xenogeneic transplantation methods were used to investigate roles and mechanisms of IRE1α/XBP1s pathway in the paclitaxel-resistant TNBC cells, and combined paclitaxel and IRE1α inhibitor in the treatment of TNBC was examined in vitro and in vivo. We found activation of UPR in paclitaxel-resistant cells, confirming that IRE1α/XBP1 promotes paclitaxel resistance in TNBC. In addition, we demonstrated that the combination of paclitaxel and IRE1α inhibitors can synergistically inhibit the proliferation of TNBC tumors both in vitro and in vivo,suggesting that IRE1α inhibitors combined with paclitaxel may be a new treatment option for TNBC. In this study, we demonstrated the important role of IRE1α signaling in mediating paclitaxel resistance and identified that combination therapies targeting IRE1α signaling could overcome paclitaxel resistance and enhance chemotherapy efficacy.

CircRNA_0044556 affects the sensitivity of triple-negative breast cancer cells to paclitaxel by regulating miR-665

CircRNAs have been implicated in the development of resistance in triple-negative breast cancer (TNBC). However, the association between circRNA_0044556 and paclitaxel (PTX) resistance in TNBC is still limited. Therefore, the purpose of this study was to investigate the effect of circRNA_0044556 on biological function and PTX resistance in TNBC cells. PTX-resistant TNBC cells (MDA-MB-231/PTX) were obtained by continuously exposing MDA-MB-231 cells to increasing paclitaxel levels. The expression levels of circRNA_0044556 and miR-665 were measured by qRT–PCR. The regulatory relationship between miR-665 and circRNA_0044556 was verified by biological information website analysis and double-luciferase reporter gene detection experiments. MTT assay, clone assay, flow cytometry and Western blot analysis were used to evaluate the influence of cell biological function. Elevated circRNA_0044556 was observed in TNBC, and paclitaxel increased the expression of circRNA_0044556 in TNBC cells. In TNBC, circRNA_0044556 acted as a ceRNA for miR-665. In addition, low expression of circRNA_0044556 combined with miR-665 inhibited the proliferation of TNBC cells and paclitaxel-resistant TNBC cells while inducing cell death. Our study demonstrated that the downregulation of circRNA_0044556 inhibits the malignant progression of TNBC cells and paclitaxel resistance via miR-665. Thus, circRNA_0044556 may be a potential therapeutic target for PTX-resistance TNBC.

Upregulation of p300 in paclitaxel-resistant TNBC: implications for cell proliferation via the PCK1/AMPK axis.

To explore the role of p300 in the context of paclitaxel (PTX) resistance in triple-negative breast cancer (TNBC) cells, focusing on its interaction with the phosphoenolpyruvate carboxykinase 1 (PCK1)/adenosine monophosphate-activated protein kinase (AMPK) pathway. The expression of p300 and PCK1 at the messenger ribonucleic acid (mRNA) level was detected using a quantitative polymerase chain reaction. The GeneCards and GEPIA databases were used to investigate the relationship between p300 and PCK1. The MDA-MB-231/PTX cell line, known for its PTX resistance, was chosen to understand the specific role of p300 in such cells. The Lipofectamine™ 3000 reagent was used to transfer the p300 small interfering RNA and the overexpression of PCK1 plasmid into MDA-MB-231/PTX. The expression levels of p300, PCK1, 5'AMPK and phosphorylated AMPK (p-AMPK) were determined using the western blot test. In TNBC cancer tissue, the expression of p300 was increased compared with TNBC paracancerous tissue (P < 0.05). In the MDA-MB-231 cell line of TNBC, the expression of p300 was lower than in the PTX-resistant TNBC cells (MDA-MB-231/PTX) (P < 0.05). The PCK1 expression was decreased in the TNBC cancer tissue compared with TNBC paracancerous tissue, and the PCK1 expression was reduced in MDA-MB-231/PTX than in MDA-MB-231 (P < 0.05) indicating that PCK1 was involved in the resistance function. Additionally, p-AMPK was decreased in MDA-MB-231/PTX compared with MDA-MB-231 (P < 0.05). The adenosine triphosphate (ATP) level was also detected and was significantly lower in MDA-MB-231/PTX than in MDA-MB-231 (P < 0.05). Additionally, cell proliferation increased significantly in MDA-MB-231/PTX at 48 and 72 h (P < 0.05) suggesting that MDA-MB-231/PTX cells obtained the resistance function which was associated with AMPK and ATP level. When p300 was inhibited, p-AMPK and ATP levels elevated in MDA-MB-231/PTX (P < 0.05). When PCK1 was suppressed, the ATP consumption rate decreased, and cell proliferation increased (P < 0.05). However, there were no changes in p300. In MDA-MB-231/PTX, p300 can inhibit p-AMPK and ATP levels by inhibiting PCK1 expression. Our findings suggest that targeting p300 could modulate the PCK1/AMPK axis, offering a potential therapeutic avenue for overcoming PTX resistance in TNBC.

Detection of metabolic adaptation in a triple-negative breast cancer animal model with [18F]choline-PET imaging as a surrogate for drug resistance.

Test the feasibility of an image-based method to identify taxane resistance in mouse bearing triple-negative breast cancer (TNBC) tumor xenografts. Xenograft tumor-bearing mice from paclitaxel-sensitive and paclitaxel-resistant TNBC cells (MDA-MD-346) were generated by orthotopic injection into female NOD-SCID mice. When tumors reached 100-150 mm3, mice were scanned using [18F]choline PET/CT. Tumors were collected and sliced for autoradiography and immunofluorescence analysis. Quantitative data was analyzed accordingly. From fifteen mice scanned, five had taxane-sensitive cell line tumors of which two underwent taxol-based treatment. From the remaining 10 mice with taxane-resistant cell line tumors, four underwent taxol-based treatment. Only 13 mice had the tumor sample analyzed histologically. When normalized to the blood pool, both cell lines showed differences in metabolic uptake before and after treatment. Treated and untreated taxane-sensitive and taxane-resistant cell lines have different metabolic properties that could be leveraged before the start of chemotherapy.

Activity of Lysosomal ABCC3, ABCC5 and ABCC10 is Responsible for Lysosomal Sequestration of Doxorubicin and Paclitaxel-Oregongreen488 in Paclitaxel-Resistant Cancer Cell Lines.

Cancer cell multidrug resistance induced by paclitaxel contributes to the high failure rates of chemotherapy and relapse of the disease. Several mechanisms have been described that underlie the observed resistance, including the overexpression of ABCB1 (P-glycoprotein), which represents an ATP-binding cassette (ABC) transmembrane protein, and its functional occurrence in lysosomal membranes is linked to drug accumulation in these organelles. Using clinically-relevant models of paclitaxel-resistant triple-negative breast cancer and non-small cell lung cancer cell lines, we provide evidence for the role of ABCC subfamily members in the lysosomal sequestration of drugs in multidrug resistant phenotypes. Proteins expression level and its cellular localisation was measured using Western Blot and confocal microscopy. Drug accumulation was analysed by confocal microscopy and flow cytometry. Drug cytotoxicity was tested using resasurin assay and anexin V propidium iodide staining. Regardless of the alteration in gene expression, paclitaxel induced the intracellular redistribution of ABCC3, ABCC5 and ABCC10 and their enrichment in lysosomes. The use of ABCC inhibitors and transient silencing of these three genes limited the accumulation of doxorubicin and paclitaxel-OregonGreen488 in lysosomes, while having little impact on the total drug level inside cells. The cancer cells were also sensitized to various structurally unrelated chemotherapeutics of differing acidity. The results suggest that lysosome membranes anchored ABCC proteins which remained functionally active and were capable to load chemotherapeutics into lysosomes in paclitaxel-resistant cancer cells. Therefore, targeting of lysosomal ABCC transporters may help to overcome paclitaxel-induced resistance by reducing the accumulation of drugs in lysosomes.

Phloridzin Docosahexaenoate Inhibits Spheroid Formation by Breast Cancer Stem Cells and Exhibits Cytotoxic Effects against Paclitaxel-Resistant Triple Negative Breast Cancer Cells.

The eradication of cancer stem cells (CSCs) is vital to successful cancer treatment and overall disease-free survival. CSCs are a sub-population of cells within a tumor that are defined by their capacity for continuous self-renewal and recapitulation of new tumors, demonstrated in vitro through spheroid formation. Flavonoids are a group of phytochemicals with potent anti-oxidant and anti-cancer properties. This paper explores the impact of the flavonoid precursor phloridzin (PZ) linked to the ω-3 fatty acid docosahexaenoate (DHA) on the growth of MCF-7 and paclitaxel-resistant MDA-MB-231-TXL breast cancer cell lines. Spheroid formation assays, acid phosphatase assays, and Western blotting were performed using MCF-7 cells, and the cell viability assays, Annexin-V-488/propidium iodide (PI) staining, and 7-aminoactinomycin D (7-AAD) assays were performed using MDA-MB-231-TXL cells. PZ-DHA significantly reduced spheroid formation, as well as the metabolic activity of MCF-7 breast cancer cells in vitro. Treatment with PZ-DHA also suppressed the metabolic activity of MDA-MB-231-TXL cells and led to apoptosis. PZ-DHA did not have an observable effect on the expression of the drug efflux transporters ATP-binding cassette super-family G member 2 (ABCG2) and multidrug resistance-associated protein 1 (MRP1). PZ-DHA is a potential treatment avenue for chemo-resistant breast cancer and a possible novel CSC therapy. Future pre-clinical studies should explore PZ-DHA as a chemo-preventative agent.

Computational drug repositioning for the identification of new agents to sensitize drug-resistant breast tumors across treatments and receptor subtypes.

Drug resistance is a major obstacle in cancer treatment and can involve a variety of different factors. Identifying effective therapies for drug resistant tumors is integral for improving patient outcomes. In this study, we applied a computational drug repositioning approach to identify potential agents to sensitize primary drug resistant breast cancers. We extracted drug resistance profiles from the I-SPY 2 TRIAL, a neoadjuvant trial for early stage breast cancer, by comparing gene expression profiles of responder and non-responder patients stratified into treatments within HR/HER2 receptor subtypes, yielding 17 treatment-subtype pairs. We then used a rank-based pattern-matching strategy to identify compounds in the Connectivity Map, a database of cell line derived drug perturbation profiles, that can reverse these signatures in a breast cancer cell line. We hypothesize that reversing these drug resistance signatures will sensitize tumors to treatment and prolong survival. We found that few individual genes are shared among the drug resistance profiles of different agents. At the pathway level, however, we found enrichment of immune pathways in the responders in 8 treatments within the HR+HER2+, HR+HER2-, and HR-HER2- receptor subtypes. We also found enrichment of estrogen response pathways in the non-responders in 10 treatments primarily within the hormone receptor positive subtypes. Although most of our drug predictions are unique to treatment arms and receptor subtypes, our drug repositioning pipeline identified the estrogen receptor antagonist fulvestrant as a compound that can potentially reverse resistance across 13/17 of the treatments and receptor subtypes including HR+ and triple negative. While fulvestrant showed limited efficacy when tested in a panel of 5 paclitaxel resistant breast cancer cell lines, it did increase drug response in combination with paclitaxel in HCC-1937, a triple negative breast cancer cell line. We applied a computational drug repurposing approach to identify potential agents to sensitize drug resistant breast cancers in the I-SPY 2 TRIAL. We identified fulvestrant as a potential drug hit and showed that it increased response in a paclitaxel-resistant triple negative breast cancer cell line, HCC-1937, when treated in combination with paclitaxel.

Abstract 1670: Sabizabulin shows anti-cancer efficacy in HER2+ breast cancer and novel sabizabulin derivatives overcome paclitaxel-resistance in triple negative breast cancer

Abstract Of the four breast cancer molecular subtypes, the HER2 overexpressing subtype (HER2+) accounts for 15% of all breast cancer cases. Preferred frontline treatment relies on anti-HER2 therapies, such as trastuzumab and pertuzumab, combined with microtubule inhibitors, such as taxanes. However, the clinical efficacy of taxanes is limited by development of chemoresistance and hematological and neurotoxicities. Other agents that target tubulin, such as colchicine-binding site inhibitors (CBSIs) are a class of promising alternatives to taxane therapy due to their ability to overcome P-gp-mediated taxane resistance. Sabizabulin (formerly known as VERU-111) is a potent CBSI that is orally bioavailable, overcomes paclitaxel resistance, and inhibits tumor growth and distant metastases in triple negative breast cancer (TNBC). Here, we demonstrate sabizabulin’s anti-cancer efficacy in HER2+ breast cancer. We report that sabizabulin inhibits proliferation of HER2+ breast cancer, maintains a low nanomolar IC50 value, inhibits colony formation, and causes apoptosis in HER2+ breast cancer cell lines. Sabizabulin inhibits the primary tumor growth in an orthotopic HER2+ in vivo model, BT474, and in a patient-derived xenograft model, HCI-12. While sabizabulin shows promising results for treatment in HER2+ breast cancer, we further optimized the structure of sabizabulin to create a new class of anti-cancer molecules: 40a, CH-2-77, and 60c. Based on in vitro data, 60c showed higher potency in HER2+ breast cancer cell lines and was chosen as the lead compound to further study in a paclitaxel-resistant triple negative breast cancer in vivo study where it was able to effectively inhibit primary tumor growth compared to the vehicle group. Citation Format: Kelli L. Hartman, Raisa I. Krutilina, Damilola Oluwalana, Deanna N. Parke, Hao Chen, Duane D. Miller, Wei Li, Tiffany N. Seagroves. Sabizabulin shows anti-cancer efficacy in HER2+ breast cancer and novel sabizabulin derivatives overcome paclitaxel-resistance in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1670.

Establishment of A Novel Paclitaxel-Resistant Triple-Negative Breast Cancer Cell Line

Objective: Triple-negative breast cancer (TNBC) is one of the most aggressive subtypes of breast cancer, and is associated with poor prognosis. Paclitaxel, a microtubule-binding agent, and chemotherapeutic agent, has been widely used in the management of TNBC. However, acquired chemoresistance is one of the main obstacles leading to ineffective TNBC treatment. Therefore, this study aimed to establish and characterize paclitaxel-resistant triple-negative breast cancer cell lines for investigating the molecular mechanisms of drug resistance. Material and Methods: Hs578T cancer cell lines were used to develop paclitaxel-resistant (Hs578T-PR) cells, via repeated exposure to increasing concentrations of paclitaxel in a stepwise manner. Drug response and growth curves were then measured by Sulforhodamine B assay. Changes in cell morphology were examined by microscopy. Furthermore, expression of mRNA, related to molecular mechanisms in drug-resistant cells, was identified by using real-time polymerase chain reaction (qPCR). Results: The Hs578T-PR cell lines were successfully established in just 4 months. They were highly resistant to paclitaxel, with their IC50 and resistance index at 72.8±3.08 nM and 7.4-folds, respectively, compared to the parental cells. For identifying molecular mechanisms underlining paclitaxel resistance, using the RT-qPCR analysis, it was found that Hs578T-PR cells exhibited kinesin family member 3C overexpression. Furthermore, the pro-apoptotic protein BAX was down-regulated; whereas the anti-apoptotic Bcl-2 was up-regulated in Hs578T-PR cells. Conclusion: Novel, highly paclitaxel-resistant (Hs578T-PR) cell lines established in this study could represent a useful model for identifying the molecular mechanisms of chemoresistance, and for evaluating the efficacy of novel anti-cancer drugs to overcome chemoresistance in TNBC.­­

Growth differentiation factor 15 is required for triple-negative breast cancer cell growth and chemoresistance.

Growth differentiation factor 15 (GDF15) is a pleiotropic cytokine, which is involved in the cellular stress response following acute damage. However, the functional role of GDF15 in triple-negative breast cancer (TNBC) has not been fully elucidated. ELISA, Western blot, and PCR assays as well as bioinformatics analyses were conducted to observe the expression of GDF15. Cell Counting Kit-8, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and crystal violet staining assays were conducted to evaluate paclitaxel resistance and cell viability. Cell apoptosis was analyzed by Western blotting. Murine xenograft model assay was employed to evaluate tumor growth in vivo . Our data indicate that GDF15 is markedly elevated in paclitaxel-resistant TNBC cells, which is significantly associated with unfavorable prognosis. Silencing of GDF15 robustly inhibits the proliferation of tumor cells and increases their sensitivity to paclitaxel in vitro and in vivo , whereas the treatment of purified GDF15 protein confers breast cancer cells with chemoresistance ability. Moreover, GDF15 activates protein kinase B (AKT) /mammalian target of rapamycin (mTOR) signaling, inhibition of AKT or mTOR reverses the prosurvival effect of GDF15 and enhances the antitumor efficacy of paclitaxel in TNBC cells. Altogether, our study uncovers the role of GDF15 in tumor growth and paclitaxel resistance, implicating a potential therapeutic target for TNBC.

Insight into drug sensitizing effect of diallyl disulfide and diallyl trisulfide from Allium sativum L. on paclitaxel-resistant triple-negative breast cancer cells

Ethnopharmacological relevanceAyurvedic practitioners and herbal healers in India and China have extensively used garlic (Allium sativum L.) to treat cancers. Diallyl disulfide (DADS) and diallyl trisulfide (DATS) are major volatile organosulfur phytochemical constituents found in garlic. Aim of the studyTo find new insight into the drug sensitizing effect of DADS and DATS on paclitaxel (PTX)-resistant triple-negative breast cancer cells (TNBC/PR). Materials and methodsThis study estimates the non-toxic concentration of DADS and DATS against normal healthy breast epithelial cell line (MCF-12A) by using a trypan blue viability assay. Also, it evaluates the effect of DADS and DATS on the sensitization of established stable TNBC/PR cell clones (MDA-MB 231 PR and MDA-MB 468 PR) by MTT, BrdU incorporation, intracellular ROS, cell cycle, and apoptosis assays. ResultsThe results show that DADS and DATS are non-cytotoxicity against MCF-12A cells. Nevertheless, DADS and DATS have shown significantly high cytotoxicity against MDA-MB 231 PR and MDA-MB 468 PR cells. They also inhibited PTX-resistant cell proliferation by blocking the cell cycle. Further, they induced apoptosis by activation of caspase 3 and 9. N-acetyl cysteine pre-treatment inhibited DADS and DATS-induced intracellular ROS release. In silico study shows that DADS and DATS interact with a large extracellular loop (LEL) of CD151 with a binding energy of −4.0 kcal/mol and transmembrane domain (TM) with a binding affinity of 11.7 and 13.6 kcal/mol, respectively. They also inhibited the surface expression of CD151 in TNBC/PR cells. ConclusionThis study implies that DADS and DATS could be considered for sensitizing drug-resistant breast cancers.

Targeting epidermal growth factor receptor in paclitaxel-resistant human breast and lung cancer cells with upregulated glucose-6-phosphate dehydrogenase.

Chemoresistance is a major obstacle to the successful treatment of triple-negative breast cancer (TNBC) and non-small-cell lung cancer (NSCLC). Therapeutic strategies to overcome chemoresistance are necessary to improve the prognosis of patients with these cancers. Paclitaxel-resistant TNBC and NSCLC sublines were generated through continuous paclitaxel treatment over 6 months. The mechanistic investigation was conducted using MTT assay, LC/MS-based metabolite analysis, flow cytometry, western blot analysis, real-time PCR and tumour xenograft experiments. Glucose-6-phosphate dehydrogenase (G6PD) expression along with an increase in 3-phosphoglycerates and ribulose-5-phosphate production was upregulated in paclitaxel-resistant cells. Blockade of G6PD decreased viability of paclitaxel-resistant cells in vitro and the growth of paclitaxel-resistant MDA/R xenograft tumours in vivo. Mechanistically, activation of the epidermal growth factor receptor (EGFR)/Akt pathway mediates G6PD expression and G6PD-induced cell survival. Blockade of the EGFR pathway inhibited G6PD expression and sensitised those paclitaxel-resistant cells to paclitaxel treatment in vitro and in vivo. Analysis of publicly available datasets revealed an association between G6PD and unfavourable clinical outcomes in patients with breast or lung cancer. EGFR signaling-mediated G6PD expression plays a pivotal role in paclitaxel resistance, highlighting the potential of targeting EGFR to overcome paclitaxel resistance in TNBC and NSCLC cells overexpressing G6PD.

Paclitaxel Resistance Modulated by the Interaction between TRPS1 and AF178030.2 in Triple-Negative Breast Cancer.

Paclitaxel is a chemotherapeutic agent that acts as an inhibitor of cellular mitosis and has been widely used in the treatment of triple-negative breast cancer (TNBC). However, paclitaxel resistance is one of the major reasons that contribute to the high failure rates of chemotherapy and the relapse of TNBC. Accumulating studies have demonstrated that long noncoding RNA (lncRNA) plays a role in the paclitaxel resistance and positively correlated with progression and metastasis of breast cancers. In the present study, microarray expression profile analysis of lncRNA was performed between paclitaxel-resistant TNBC cell line MDA-MB-231 and their parental cells. After verification with quantitative PCR, we identified that AF178030.2, an orphan lncRNA, was significantly upregulated in paclitaxel-resistant TNBC cells. Overexpression of AF178030.2 greatly attenuated the sensitivity of TNBC to paclitaxel, whereas knockdown of AF178030.2 enhanced the sensitivity of TNBC cells to paclitaxel. Furthermore, bioinformatic analysis and RNA binding protein immunoprecipitation assay reveal that AF178030.2 can directly bind with trichorhinophalangeal syndrome-1 (TRPS1), an oncogene in breast cancer, and downregulate its expression in paclitaxel-resistant TNBC cells. TRPS1 overexpression effectively increased the sensitivity of paclitaxel-resistant TNBC cells to paclitaxel. Taking together, high AF178030.2 expression contributed to paclitaxel resistance in TNBC through TRPS1 and poor clinical outcomes, which may provide a new treatment strategy for paclitaxel-resistant TNBC patients.

Antiviral Drug 2-thio-6-azauridine Sensitizes Paclitaxel-Resistant Triple Negative Breast Cancer Cells by Targeting Mammosphere Formation and ABC Transporters

Background: 2-thio-6-azauridine (TAU) is a nucleoside analog and potential antiviral drug. The antiproliferative activity of TAU has been evaluated in limited cancer cell lines. The present study is aimed to evaluate the effect of TAU on drug sensitization mechanism in paclitaxel (PTX) resistant triple-negative breast cancer (TNBC) cells.Methods: The cell death mechanism was determined using MTT, BrdU incorporation, apoptosis, and DNA damage Western blot and RT-PCR assays. A specific ELISA method was used to determine the caspase-3 activity and expression levels of MRP1, MDR1, BCRP, and MRP8. Western blot analysis was used to assess the expression of CD151, MRP1, MDR1, and BCRP in CD151 overexpressing PTX-resistant TNBC cells.Results: The combination of TAU and PTX (10:20nM) synergistically inhibited the 50% viability of 12-fold PTX-resistant TNBC cells. Mechanistically, the combination inhibited the proliferation by arresting the cell cycle at the G2M phase and induced apoptosis by altering cell integrity and nuclear morphology as well as damaging DNA. The combination sensitized the PTX-resistant TNBC cells by increasing BAX and decreasing Bcl-2 expression, activating caspase-3, and reducing the expression of ABC transporters MRP1 and MDR1. The combination reduced the expression of MRP1 and MDR1 in CD151 overexpressing PTX-resistant TNBC cells, indicating the role of CD151in TAU mediated sensitization of PTX-resistant TNBC cells. The combination also reduced the mammosphere formation efficiency of PTX-resistant TNBC cells. Conclusion: Overall, the present study illustrated the promising ability of TAU in sensitizing drug-resistant TNBC cells to PTX.

EEF2 kinase mediated autophagy as a potential therapeutic target for paclitaxel-resistant triple-negative breast cancer.

Triple-negative breast cancers (TNBCs) are initially responsive to chemotherapy, but most recurrent TNBCs develop resistance. Autophagy is believed to play dual roles in cancer and might contribute to chemoresistance. In this study, we aimed to investigate the role of autophagy and its regulator, eukaryotic elongation factor 2 kinase (eEF2K), in determining the biological nature of TNBC. We used in vitro models of TNBC, namely, paclitaxel-resistant cell lines derived from sensitive cell lines. Various approaches to measuring autophagy flux were applied. We assessed the effects of inhibiting autophagy and silencing eEF2K on cell viability, tumor formation and invasion. We also collected residual tumor samples from 222 breast cancer patients who underwent neoadjuvant chemotherapy and measured eEF2K and LC3 expression levels by immunohistochemistry (IHC). Multivariate survival analysis was used to determine prognostic variables. Compared to the parental lines, the chemoresistant lines exhibited enhanced starvation-stimulated autophagy and showed significant decreases in cell viability, growth and invasion upon treatment with autophagy inhibitors. eEF2K silencing also resulted in the suppression of autophagic activity and in aggressive biological behavior. In the survival analysis, residual tumor LC3 (P=0.001) and eEF2K (P=0.027) expression levels were independent prognostic factors for patients who underwent neoadjuvant chemotherapy, especially in those with TNBC. Our study indicated that eEF2K and autophagy play key roles in the maintenance of aggressive tumor behavior and chemoresistance in resistant TNBC. eEF2K silencing may be a novel strategy for the treatment of TNBC.

Aurora kinase A stabilizes FOXM1 to enhance paclitaxel resistance in triple-negative breast cancer.

Triple‐negative breast cancer (TNBC) has a relatively poor outcome. Acquired chemoresistance is a major clinical challenge for TNBC patients. Previously, we reported that kinase‐dead Aurora kinase A (Aurora‐A) could effectively transactivate the FOXM1 promoter. Here, we demonstrate an additional pathway through which Aurora‐A stabilizes FOXM1 by attenuating its ubiquitin in TNBC. Specifically, Aurora‐A stabilizes FOXM1 in late M phase and early G1 phase of the cell cycle, which promotes proliferation of TNBC cells. Knock‐down of Aurora‐A significantly suppresses cell proliferation in TNBC cell lines and can be rescued by FOXM1 overexpression. We observe that paclitaxel‐resistant TNBC cells exhibit high expression of Aurora‐A and FOXM1. Overexpression of Aurora‐A offers TNBC cells an additional growth advantage and protection against paclitaxel. Moreover, Aurora‐A and FOXM1 could be simultaneously targeted by thiostrepton. Combination of thiostrepton and paclitaxel treatment reverses paclitaxel resistance and significantly inhibits cell proliferation. In conclusion, our study reveals additional mechanism through which Aurora‐A regulates FOXM1 and provides a new therapeutic strategy to treat paclitaxel‐resistant triple‐negative breast cancer.

High-throughput screening (HTS) of natural products with triple-negative breast cancer (TNBC) organoids.

e12558 Background: Breast cancer is one of the most malignant diseases threatening the health of our society. Triple negative breast cancer (TNBC) is an aggressive histological subtype representing 15–20% of all breast cancers. Comparing with other breast cancer subtypes, TNBC is characterized with limited treatment options and a worse clinical outcome. Resistance to chemotherapies is common for TNBC. Therefore, continuously developing new anti-cancer drugs is of great importance for TNBC. Nature products a source of medicinal leads, but lacking suitable pre-clinical models, which could faithfully reflect in vivo tumor property, prevents these compounds from further characterizing. Now cancer organoids, as a new in vitro 3-D culture technique, were demonstrated to largely retain the biological characteristics of tumors from patients, and potentially served as an ideal platform for drug sensitivity test. Methods: Here we set up system to efficiently establish breast cancer organoids from clinical patients and further test the sensitivity of these organoids to various nature products. Results: A total of 29 TNBC organoid models were established with fresh biopsy or surgery tumor tissues from TNBC patients. Estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) in TNBC PDOs were evaluated with qPCR, western blot, Immunohistochemistry (IHC). A high-throughput cell viability assay was established for identifying lead compounds from a unique collection of 969 natural products. Primary hits were serial diluted and further evaluated for IC50 and percentage of inhibition. Preliminary mechanism of action (MOA) studies was performed with gene reporter assays, western blot and qPCR. Interestingly, organoids derived from paclitaxel resistant TNBC patients also show less sensitivity to paclitaxel in vitro, which indicated a high clinical relevance. Conclusions: Triple negative breast cancer organoid, as a good pre-clinical model largely containing tumor in vivo property, provides an ideal platform for new drug discovery and inhibitor screening. Moreover, serving as in vitro replacements for breast cancer, organoid models make it possible to test drug sensitivity for individual patient to achieve precise and personalize medication.

P029 - Eukaryotic elongation factor-2 kinase mediated autophagy as potential therapeutic target for paclitaxel-resistant triple-negative breast cancer

P029 - Eukaryotic elongation factor-2 kinase mediated autophagy as potential therapeutic target for paclitaxel-resistant triple-negative breast cancer

Knockdown of lncRNA H19 restores chemo-sensitivity in paclitaxel-resistant triple-negative breast cancer through triggering apoptosis and regulating Akt signaling pathway

Triple negative breast cancer (TNBC) is associated with poor prognosis and systemic chemotherapy is the only treatment for TNBC. However, development of chemo-resistance remains a major obstacle for TNBC treatment. Paclitaxel-resistance is mainly related to the activation of the Akt signaling pathway and deregulation of apoptotic regulatory proteins. LncRNAs are frequently dysregulated in various malignancies, including breast cancer, facilitating cell proliferation, metastasis and drug resistance. LncRNA H19 is overexpressed in approximately 70% of breast cancer patients, and has been reported to confer chemo-resistance in breast cancer. In the present study, we investigated the expression level of lncRNA H19 in paclitaxel-resistant and paclitaxel-sensitive cell lines. The results showed that the level of lncRNA H19 expression in paclitaxel-resistant cells was significantly higher than that in paclitaxel-sensitive cells, and knockdown of lncRNA H19 might restore chemo-sensitivity in paclitaxel-resistant TNBC by mediating the AKT signaling pathway. Thus, lncRNA H19 might be an efficient therapeutic target in paclitaxel-resistant TNBC treatment.