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Inhibiting homologous recombination decreases extrachromosomal amplification but has no effect on intrachromosomal amplification in methotrexate‐resistant colon cancer cells
Author(s) -
Cai Mengdi,
Zhang Huishu,
Hou Liqing,
Gao Wei,
Song Ying,
Cui Xiaobo,
Li Chunxiang,
Guan Rongwei,
Ma Jinfa,
Wang Xu,
Han Yue,
Lv Yafan,
Chen Feng,
Wang Ping,
Meng Xiangning,
Fu Songbin
Publication year - 2018
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.31781
Subject(s) - extrachromosomal dna , homologous recombination , biology , microbiology and biotechnology , gene duplication , gene , dna repair , gene silencing , dna repair protein xrcc4 , cancer research , genetics , dna mismatch repair , plasmid
Gene amplification, which involves the two major topographical structures double minutes (DMs) and homegeneously stained region (HSR), is a common mechanism of treatment resistance in cancer and is initiated by DNA double‐strand breaks. NHEJ, one of DSB repair pathways, is involved in gene amplification as we demonstrated previously. However, the involvement of homologous recombination, another DSB repair pathway, in gene amplification remains to be explored. To better understand the association between HR and gene amplification, we detected HR activity in DM‐ and HSR‐containing MTX‐resistant HT‐29 colon cancer cells. In DM‐containing MTX‐resistant cells, we found increased homologous recombination activity compared with that in MTX‐sensitive cells. Therefore, we suppressed HR activity by silencing BRCA1, the key player in the HR pathway. The attenuation of HR activity decreased the numbers of DMs and DM‐form amplified gene copies and increased the exclusion of micronuclei and nuclear buds that contained DM‐form amplification; these changes were accompanied by cell cycle acceleration and increased MTX sensitivity. In contrast, BRCA1 silencing did not influence the number of amplified genes and MTX sensitivity in HSR‐containing MTX‐resistant cells. In conclusion, our results suggest that the HR pathway plays different roles in extrachromosomal and intrachromosomal gene amplification and may be a new target to improve chemotherapeutic outcome by decreasing extrachromosomal amplification in cancer.