{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T04:24:34Z","timestamp":1787027074533,"version":"build-2736575974"},"reference-count":43,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,3,4]],"date-time":"2026-03-04T00:00:00Z","timestamp":1772582400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Pharmacol."],"abstract":"\n Introduction<\/jats:title>\n \n The development of novel anticancer agents targeting DNA replication and repair mechanisms remains a priority in leukemia therapy. In this study, newly synthesized derivatives incorporating bis-indole and pyrazolo[3,4-\n b<\/jats:italic>\n ]pyridine scaffolds were evaluated for their antiproliferative potential against leukemia cell lines.\n <\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n \n The antiproliferative activity of the synthesized compounds was assessed in four cancer cell lines, including acute myeloid leukemia (MV4-11) and chronic myeloid leukemia (K562). Growth inhibition (GI\n 50<\/jats:sub>\n ) values were determined. DNA relaxation assays were performed to evaluate inhibition of topoisomerase I and II\u03b1 activities. Cell cycle distribution, apoptosis induction, and DNA damage response markers were analyzed using cellular and molecular assays. Combination studies were conducted using CHK1, ATR, and PARP-1 inhibitors.\n <\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n Compounds\n 7b<\/jats:bold>\n ,\n 7d<\/jats:bold>\n , and\n 7e<\/jats:bold>\n demonstrated the most potent antiproliferative activity, with GI\n 50<\/jats:sub>\n values below 2.5 \u03bcM in leukemic cell lines. Compound\n 7e<\/jats:bold>\n exhibited notable cytotoxicity, with GI\n 50<\/jats:sub>\n values of 1.1 \u03bcM (MV4-11) and 2.7 \u03bcM (K562). Compounds\n 7b<\/jats:bold>\n and\n 7e<\/jats:bold>\n significantly inhibited topoisomerase I activity and effectively suppressed topoisomerase II\u03b1-mediated DNA relaxation. Cellular studies revealed S-phase cell cycle arrest, activation of apoptotic pathways (caspase cleavage and PARP-1 degradation), and induction of DNA damage response markers (\u03b3H2AX, p-CHK1, p53). In MV4-11 cells, combination treatment with CHK1 or ATR inhibitors resulted in pronounced synergistic cytotoxicity, whereas co-treatment with a PARP-1 inhibitor produced minimal synergy.\n <\/jats:p>\n <\/jats:sec>\n \n Discussion<\/jats:title>\n \n These findings identify bis-indole and pyrazolo[3,4-\n b<\/jats:italic>\n ]pyridine derivatives, particularly compound\n 7e<\/jats:bold>\n , as potent dual topoisomerase inhibitors with significant antileukemic activity. Their ability to induce DNA damage and enhance cytotoxicity in combination with DNA damage response inhibitors highlights their potential therapeutic value, especially in combination strategies targeting replication stress pathways in leukemia.\n <\/jats:p>\n <\/jats:sec>","DOI":"10.3389\/fphar.2026.1745220","type":"journal-article","created":{"date-parts":[[2026,3,4]],"date-time":"2026-03-04T07:01:25Z","timestamp":1772607685000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":2,"title":["Discovery of potent bisindole-based pyrazolopyridine derivatives as topoisomerase inhibitors: DNA damage induction and synergistic antileukemic activity"],"prefix":"10.3389","volume":"17","author":[{"given":"Wagdy M.","family":"Eldehna","sequence":"first","affiliation":[{"name":"Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Kafrelsheikh University","place":["Kafrelsheikh, Egypt"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Haytham O.","family":"Tawfik","sequence":"additional","affiliation":[{"name":"Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Tanta University","place":["Tanta, Egypt"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Denisa","family":"Vesel\u00e1","sequence":"additional","affiliation":[{"name":"Department of Experimental Biology, Faculty of Science, Palack\u00fd University Olomouc","place":["Olomouc, Czechia"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Miroslav","family":"Pe\u0159ina","sequence":"additional","affiliation":[{"name":"Department of Experimental Biology, Faculty of Science, Palack\u00fd University Olomouc","place":["Olomouc, Czechia"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ahmed T.","family":"Negmeldin","sequence":"additional","affiliation":[{"name":"Department of Pharmaceutical Sciences, College of Pharmacy and Thumbay Research Institute for Precision Medicine, Gulf Medical University","place":["Ajman, United Arab Emirates"]},{"name":"Department of Pharmaceutical Organic Chemistry, Faculty of Pharmacy, Cairo University","place":["Cairo, Egypt"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zainab M.","family":"Elsayed","sequence":"additional","affiliation":[{"name":"Scientific Research and Innovation Support Unit, Faculty of Pharmacy, Kafrelsheikh University","place":["Kafr El-Shaikh, Egypt"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Taghreed A.","family":"Majrashi","sequence":"additional","affiliation":[{"name":"Department of Pharmacognosy, College of Pharmacy, King Khalid University","place":["Abha, Saudi Arabia"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Veronika","family":"Voj\u00e1\u010dkov\u00e1","sequence":"additional","affiliation":[{"name":"Department of Experimental Biology, Faculty of Science, Palack\u00fd University Olomouc","place":["Olomouc, Czechia"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mostafa M.","family":"Elbadawi","sequence":"additional","affiliation":[{"name":"Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Kafrelsheikh University","place":["Kafrelsheikh, Egypt"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Moataz A.","family":"Shaldam","sequence":"additional","affiliation":[{"name":"Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Kafrelsheikh University","place":["Kafrelsheikh, Egypt"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Vladim\u00edr","family":"Kry\u0161tof","sequence":"additional","affiliation":[{"name":"Department of Experimental Biology, Faculty of Science, Palack\u00fd University Olomouc","place":["Olomouc, Czechia"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hatem A.","family":"Abdel-Aziz","sequence":"additional","affiliation":[{"name":"Applied Organic Chemistry Department, National Research Center","place":["Cairo, Egypt"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,3,4]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"2195","DOI":"10.2174\/0929867327999200817102154","article-title":"Drug repositioning for the treatment of hematologic disease: limits, challenges and future perspectives","volume":"28","author":"Allegra","year":"2021","journal-title":"Curr. 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