{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,9]],"date-time":"2026-10-09T21:38:15Z","timestamp":1791581895777,"version":"4.3.4"},"reference-count":47,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2026,4,23]],"date-time":"2026-04-23T00:00:00Z","timestamp":1776902400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["81572915"],"award-info":[{"award-number":["81572915"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["82403584"],"award-info":[{"award-number":["82403584"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"award":["81572915"],"award-info":[{"award-number":["81572915"]}],"id":[{"id":"https:\/\/ror.org\/01h0zpd94","id-type":"ROR","asserted-by":"publisher"}]},{"award":["82403584"],"award-info":[{"award-number":["82403584"]}],"id":[{"id":"https:\/\/ror.org\/01h0zpd94","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100005046","name":"Natural Science Foundation of Heilongjiang Province","doi-asserted-by":"publisher","award":["LH2020H015"],"award-info":[{"award-number":["LH2020H015"]}],"id":[{"id":"10.13039\/501100005046","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Gene amplification resulting from double strand breaks (DSBs) is a typical genetic alteration in tumorigenesis and drug-resistant progression. Amplified oncogenes and drug-resistant genes are present on extrachromosomal DNAs (ecDNAs), or chromosomal homogeneously staining regions (HSRs). Considering the role of mismatch repair (MMR) as a sensor of DSBs, we hypothesized that MMR may be involved in gene amplification. We used two MTX-resistant HT-29 colorectal cancer cell lines, which served as models with amplified genes mainly in HSRs or ecDNAs. Expression of MSH2, a key protein in MMR, was increased following the acquisition of MTX-resistant. MMR inhibition was achieved by depleting MSH2. Suppression of MMR led to decreased copy numbers of amplified genes as well as the quantity of ecDNAs and HSR. This was caused by the decreased efficiency of DSBs repair, which resulted from the reduced ability of MMR to recruit DSBs repair proteins. Additionally, it accelerated the formation of micronuclei (MN)\/nuclear buds (NBUDs), which functioned to eliminate the amplified genes. Furthermore, the suppression of MMR was capable of inhibiting cell proliferation and enhancing MTX-sensitivity in ecDNA-containing cells. Conversely, suppression of MMR had no effect on gene amplification in HSR-containing cells. Our findings demonstrate that MMR plays a pivotal role in gene amplification through mediating DSBs repair pathways and facilitating the formation of MN\/NBUDs in ecDNA-containing cells. MMR is likely to emerge as a prime therapeutic target worthy of in-depth exploration in future clinical investigations.<\/jats:p>","DOI":"10.3390\/ijms27093774","type":"journal-article","created":{"date-parts":[[2026,4,24]],"date-time":"2026-04-24T08:08:02Z","timestamp":1777018082000},"page":"3774","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Dysfunctional DNA Mismatch Repair Drives the Evolution of Gene Amplification in MTX-Resistant Human Colorectal Cancer Cells"],"prefix":"10.3390","volume":"27","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8186-0947","authenticated-orcid":false,"given":"Xu","family":"Wang","sequence":"first","affiliation":[{"name":"Department of Medical Genetics, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China"},{"name":"Key Laboratory of Preservation of Human Genetic Resources and Disease Control in China (Harbin Medical University), Ministry of Education, Harbin 150081, China"},{"name":"Department of Microbiology, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Siqing","family":"Li","sequence":"additional","affiliation":[{"name":"Department of Medical Genetics, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China"},{"name":"Key Laboratory of Preservation of Human Genetic Resources and Disease Control in China (Harbin Medical University), Ministry of Education, Harbin 150081, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yanghe","family":"Liu","sequence":"additional","affiliation":[{"name":"Department of Medical Genetics, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China"},{"name":"Key Laboratory of Preservation of Human Genetic Resources and Disease Control in China (Harbin Medical University), Ministry of Education, Harbin 150081, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yihan","family":"Gao","sequence":"additional","affiliation":[{"name":"Department of Medical Genetics, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China"},{"name":"Key Laboratory of Preservation of Human Genetic Resources and Disease Control in China (Harbin Medical University), Ministry of Education, Harbin 150081, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xinyu","family":"Shi","sequence":"additional","affiliation":[{"name":"Department of Medical Genetics, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China"},{"name":"Key Laboratory of Preservation of Human Genetic Resources and Disease Control in China (Harbin Medical University), Ministry of Education, Harbin 150081, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xuejian","family":"Han","sequence":"additional","affiliation":[{"name":"Department of Medical Genetics, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China"},{"name":"Key Laboratory of Preservation of Human Genetic Resources and Disease Control in China (Harbin Medical University), Ministry of Education, Harbin 150081, China"},{"name":"Biotechnology Experimental Teaching Center, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Huishu","family":"Zhang","sequence":"additional","affiliation":[{"name":"Department of Medical Genetics, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China"},{"name":"Key Laboratory of Preservation of Human Genetic Resources and Disease Control in China (Harbin Medical University), Ministry of Education, Harbin 150081, China"},{"name":"Biotechnology Experimental Teaching Center, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3219-591X","authenticated-orcid":false,"given":"Xiangning","family":"Meng","sequence":"additional","affiliation":[{"name":"Department of Medical Genetics, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China"},{"name":"Key Laboratory of Preservation of Human Genetic Resources and Disease Control in China (Harbin Medical University), Ministry of Education, Harbin 150081, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"906","DOI":"10.1016\/j.cell.2025.12.009","article-title":"EcDNA-borne structural variants drive oncogenic fusion transcript 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