Downregulation of Choline Kinase-Alpha Enhances Autophagy in Tamoxifen-Resistant Breast Cancer Cells.
Choline kinase-α (Chk-α) and autophagy have gained much attention, as they relate to the drug-resistance of breast cancer. Here, we explored the potential connection between Chk-α and autophagy in the mechanisms driving to tamoxifen (TAM) resistance, in estrogen receptor positive (ER+) breast cancer cells (BCCs). Human BCC lines (MCF-7 and TAM-resistant MCF-7 (MCF-7/TAM) cells) were used. Chk-α expression and activity was suppressed by the transduction of shRNA (shChk-α) with lentivirus and treatment with CK37, a Chk-α inhibitor. MCF-7/TAM cells had higher Chk-α expression and phosphocholine levels than MCF-7 cells. A specific downregulation of Chk-α by the transduction of shChk-α exhibited a significant decrease in phosphocholine levels in MCF-7 and MCF-7/TAM cells. The autophagy-related protein, cleaved microtubule-associated protein light chain 3 (LC3) and autophagosome-like structures were significantly increased in shChk-α-transduced or CK37-treated MCF-7 and MCF-7/TAM cells. The downregulation of Chk-α attenuated the phosphorylation of AKT, ERK1/2, and mTOR in both MCF-7 and MCF-7/TAM cells. In MCF-7 cells, the downregulation of Chk-α resulted in an induction of autophagy, a decreased proliferation ability and an activation of caspase-3. In MCF-7/TAM cells, despite a significant decrease in proliferation ability and an increase in the percentage of cells in the G0/G1 phase of the cell cycle, the downregulation of Chk-α did not induced caspase-dependent cell death and further enhanced autophagy and G0/G1 phase arrest. An autophagy inhibitor, methyladenine (3-MA) induced death and attenuated the level of elevated LC3 in MCF-7/TAM cells. Elucidating the interplay between choline metabolism and autophagy will provide unique opportunities to identify new therapeutic targets and develop novel treatment strategies that preferentially target TAM-resistance.
Department of Radiology, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul 110-744, Korea.
Hoe Suk
HS
Kim
Department of Biomedical Science, College of Medicine, Seoul National University, 103 Daehak-ro, Jongno-gu, Seoul 110-799, Korea.
Lianji
L
Tian
Department of Biomedical Science, College of Medicine, Seoul National University, 103 Daehak-ro, Jongno-gu, Seoul 110-799, Korea.
Minji
M
Jung
Department of Biomedical Science, College of Medicine, Seoul National University, 103 Daehak-ro, Jongno-gu, Seoul 110-799, Korea.
Sul Ki
SK
Choi
Department of Radiology, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul 110-744, Korea.
Yujin
Y
Sun
Department of Biomedical Science, College of Medicine, Seoul National University, 103 Daehak-ro, Jongno-gu, Seoul 110-799, Korea.
Hyeonjin
H
Kim
Department of Biomedical Science, College of Medicine, Seoul National University, 103 Daehak-ro, Jongno-gu, Seoul 110-799, Korea; Department of Radiology, Seoul National University Hospital, 101 Daehak-ro, Jongno-gu, Seoul 110-744, Korea.
Woo Kyung
WK
Moon
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology*; D001343:Autophagy / Q000187:drug effects / Q000235:genetics*; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002797:Choline Kinase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D061986:MCF-7 Cells; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D013629:Tamoxifen / Q000494:pharmacology*
D018931:Antineoplastic Agents, Hormonal; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D034741:RNA, Small Interfering; D013629:Tamoxifen; C025946:3-methyladenine; C546842:MTOR protein, human; C517212:CHKA protein, human; D002797:Choline Kinase; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D053148:Caspase 3; D000225:Adenine