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Voltage-gated potassium (K+) channels are overexpressed in breast cancer cell lines, suggesting that pharmacological blockade may reduce growth and viability. This study combines FDA-approved 4-aminopyridine (4-AP), a K+ channel blocker, with PTX in MCF-7 and MDA-MB-231 cells. Viability, clonogenic survival, cell cycle distribution, apoptosis, intracellular K+ and Ca2+ levels, and transmembrane potential were assessed. Combination therapy reduced viability and colony formation, increased apoptosis, induced G1/S and S/G2-M phase arrests depending on the line, elevated intracellular K+ across treatments, significantly raised Ca2+ after combination, and produced membrane depolarization, supporting a mechanistic basis for improved PTX activity.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":40,"@type":76,"position":81},"https://docshare.wps.com/document/research-report/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/investigation-of-the-effects-of-blocking-potassium-channels-with-4-aminopyridine-on-paclitaxel-activity-in-breast-cancer-cell-lines/331615/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/investigation-of-the-effects-of-blocking-potassium-channels-with-4-aminopyridine-on-paclitaxel-activity-in-breast-cancer-cell-lines/331615.png","ImageObject",300,407,{"name":92,"@type":93},"Clementine","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-11-03","2026-09-21",true,{"@type":102,"interactionType":103,"userInteractionCount":39},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"What is the goal of combining 4-aminopyridine with paclitaxel in breast cancer cell lines?","Question",{"text":112,"@type":113},"To improve the anticancer activity of paclitaxel by using 4-aminopyridine as a voltage-gated potassium channel blocker in MCF-7 and MDA-MB-231 cells.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"How was cell viability and long-term survival measured in the study?",{"text":117,"@type":113},"Viability was assessed using trypan blue, and long-term clonogenic survival was evaluated with a clonogenic assay to quantify colony formation.",{"name":119,"@type":110,"acceptedAnswer":120},"What effects did the combination treatment have on apoptosis and the cell cycle?",{"text":121,"@type":113},"Apoptotic cell numbers increased after combination treatment in both cell lines. Cell cycle analyses showed G1 arrest with 4-AP alone in both lines, while combination treatment produced S-phase arrest in MCF-7 and S-phase plus G2/M arrest in MDA-MB-231 cells.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},331615,1790639225,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":39,"category_name":40,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":39,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":52,"language":139,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":67,"update_tm":143,"read_time":144,"preview_page_count":4},1374391974564,"https://ap-avatar.wpscdn.com/avatar/14000253aa45c000a9e?x-image-process=image/resize,m_fixed,w_180,h_180&k=1779874745381141002","Cancer Reports  \nORIGINAL ARTICLE  OPEN ACCESS   \nInvestigation of the Effects of Blocking Potassium Channels With 4-Aminopyridine on Paclitaxel Activity in Breast Cancer Cell Lines  \nEsra M. Cüce-Aydoğmuş1  | G. Ayşe İnhan-Garip2   \n1School of Medicine, Biophysics Department, T.C. Maltepe University, Maltepe, İstanbul, Turkey | 2School of Medicine, Biophysics Department, T.C. Marmara University, Maltepe, İstanbul, Turkey  \nCorrespondence: Esra M. Cüce-Aydoğmuş ([esra.aydogmus@maltepe.edu.tr](esra.aydogmus@maltepe.edu.tr))  \nReceived: 6 February 2024 | Revised: 23 October 2024 | Accepted: 21 November 2024  \nFunding: This work was supported by T.C. Marmara University Scientific Research Project Department, SAG-C-DRP-080715-0327.  \nKeywords: apoptosis | breast cancer | cell cycle | drug mechanism | drug repurposing | transmembrane potential  \nABSTRACT  \nBackground: Paclitaxel (PTX) has been used as a chemotherapeutic agent for several malignancies, including breast cancer, and efforts to increase the efficiency of PTX are continuous. Previous studies have shown that the voltage-gated K+ channels are over-expressed in breast cancer cell lines; therefore, blocking this type of K+ channel reduces cell proliferation and viability. Aims: In this study, FDA-approved 4-aminopyridine (4-AP), a voltage-gated potassium channel blocker, was used in combination with PTX to improve the anticancer activity of PTX in MCF-7 and MDA-MB-231 cell lines.  \nMethods and Results: Viability was determined with trypan blue, a clonogenic assay was performed, and the cell cycle was determined with a flow cytometer and immunochemistry. To gain an insight into the mechanism, intracellular K+ concentration, intracellular Ca2+ (calcium) concentration, and transmembrane potential measurements were made with corresponding fluorescent dyes. The apoptotic cell number was determined using Annexin /PI method by flow cytometer. Viability decreased with combination therapy and the clonogenic assay proved decreased colony formation. The apoptotic cell number was increased after treatment with the combination in both cell lines. Cell cycle measurements showed G1 arrest for both MCF-7 and MDA-MB-231 cell lines upon 4-AP treatment. PTX caused G1 arrest in MCF-7 cells and S phase arrest in MDA-MB-231 cells. Combination treatment caused S phase arrest in MCF-7 cells and S phase and G2/M phase arrest in MDA-MB-231 cells. Intracellular K+ concentration was increased after all treatments in both cell lines. Ca2+ concentration was increased significantly after combination treatment. Depolarization in the transmembrane potential was observed after all treatments in both cell lines.  \nConclusion: Biophysical parameters like the transmembrane potential and ion fluxes have been defined in cancer progression which can provide new aspects for cancer treatments. This study shows that the combination of 4-AP with PTX is a promising alternative the mechanism of which needs further investigation considering the results obtained for Ca2+, K+, and membrane potential.  \n1 | Introduction  \nAccording to the data of the World Cancer Research Fund International, breast and lung cancers are the most common  \ntypes of cancer. The prevalence of breast cancer (BC) among women worldwide is 11.7% of total cancer cases, and 24.5% of the cancers in females and with this rate, breast cancer ranks first [1] . The molecular classification involves three major subtypes  \nThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.  \n© 2024 The Author(s). Cancer Reports published by Wiley Periodicals LLC.  \nCancer Reports, 2024; 7:e70072 1 of 10  \n[https://doi.org/10.1002/cnr2.70072](https://doi.org/10.1002/cnr2.70072)  \ndepending on estrogen or progesterone receptor expression and human epidermal growth factor 2 (ERBB2; formerly HER2): hormone receptor-positive/ERBB2","cbCail1n8hvzmwOr","https://ap.wps.com/l/cbCail1n8hvzmwOr","pdf",1807712,"English","# Abstract\n# Introduction","[{\"question\":\"What is the goal of combining 4-aminopyridine with paclitaxel in breast cancer cell lines?\",\"answer\":\"To improve the anticancer activity of paclitaxel by using 4-aminopyridine as a voltage-gated potassium channel blocker in MCF-7 and MDA-MB-231 cells.\"},{\"question\":\"How was cell viability and long-term survival measured in the study?\",\"answer\":\"Viability was assessed using trypan blue, and long-term clonogenic survival was evaluated with a clonogenic assay to quantify colony formation.\"},{\"question\":\"What effects did the combination treatment have on apoptosis and the cell cycle?\",\"answer\":\"Apoptotic cell numbers increased after combination treatment in both cell lines. Cell cycle analyses showed G1 arrest with 4-AP alone in both lines, while combination treatment produced S-phase arrest in MCF-7 and S-phase plus G2/M arrest in MDA-MB-231 cells.\"}]","Investigation of the Effects of Blocking Potassium Channels With 4-Aminopyridine on Paclitaxel Activity in Breast Cancer Cell Lines | PDF",1789994321,25]