title: DNA-PKcs interference sensitizes colorectal cancer cells to a mTOR kinase inhibitor WAY-600.
abstract: Colorectal cancer (CRC) is one leading contributor of cancer-related mortalities. Mammalian target of rapamycin (mTOR), existing in two complexes (mTORC1/2), is a valuable target for possible CRC interference. In the current study, we showed that WAY-600, a potent mTOR inhibitor, only exerted moderate activity against primary and HT-29 CRC cells. We proposed that DNA-dependent protein kinase catalytic subunit (DNA-PKcs) could be the major resistance factor of WAY-600 in CRC cells. DNA-PKcs inhibitors, including NU7026 and NU7441, dramatically enhanced WAY-600-induced cytotoxic and pro-apoptotic effect against the CRC cells. Further, WAY-600-exerted cytotoxicity was significantly increased in DNA-PKcs-silenced (by targeted siRNA/shRNA) CRC cells, but was attenuated with DNA-PKcs overexpression. Our evidence suggested that DNA-PKcs Thr-2609 phosphorylation might be critical for WAY-600's resistance. Mutation of this site through introducing a dominant negative DNA-PKcs (T2609A) dramatically potentiated WAY-600's sensitivity in HT-29 cells. Meanwhile, overexpression of protein phosphatase 5 (PP5) dephosphorylated DNA-PKcs at Thr-2609, and significantly increased WAY-600's sensitivity in HT-29 cells. In vivo, WAY-600-induced anti-HT-29 xenograft growth activity was significantly potentiated with NU7026 co-administration. These results suggest that DNA-PKcs could be the major resistance factor of WAY-600 in CRC cells.
authors.affiliation: Gastrointestinal Surgery, Tianjin Baodi Hospital, Tianjin, 301800, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Wu
authors.affiliation: Gastrointestinal Surgery, Tianjin Baodi Hospital, Tianjin, 301800, China.
authors.forename: Jiansheng
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Gastrointestinal Surgery, Tianjin Baodi Hospital, Tianjin, 301800, China.
authors.forename: Huiguo
authors.initials: H
authors.lastname: Wu
authors.affiliation: Gastrointestinal Surgery, Tianjin Baodi Hospital, Tianjin, 301800, China. Electronic address: drhanenjun8@sina.com.
authors.forename: Enkun
authors.initials: E
authors.lastname: Han
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002867:Chromones / Q000008:administration & dosage / Q000494:pharmacology; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism*; D051747:DNA-Activated Protein Kinase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004357:Drug Synergism; D055785:Gene Knockdown Techniques; D019073:HT29 Cells; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009025:Morpholines / Q000008:administration & dosage / Q000494:pharmacology; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: C479235:2-(morpholin-4-yl)benzo(h)chromen-4-one; C499693:8-dibenzothiophen-4-yl-2-morpholin-4-yl-chromen-4-one; D002867:Chromones; D009025:Morpholines; D009687:Nuclear Proteins; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; C546842:MTOR protein, human; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D058570:TOR Serine-Threonine Kinases
keywords: Chemo-sensitization; Colorectal cancer; DNA-PKcs; WAY-600; mTOR