Effect of Cellular Location of Human Carboxylesterase 2 on CPT-11 Hydrolysis and Anticancer Activity.
CPT-11 is an anticancer prodrug that is clinically used for the treatment of metastatic colorectal cancer. Hydrolysis of CPT-11 by human carboxylesterase 2 (CE2) generates SN-38, a topoisomerase I inhibitor that is the active anti-tumor agent. Expression of CE2 in cancer cells is under investigation for the tumor-localized activation of CPT-11. CE2 is normally expressed in the endoplasmic reticulum of cells but can be engineered to direct expression of active enzyme on the plasma membrane or as a secreted form. Although previous studies have investigated different locations of CE2 expression in cancer cells, it remains unclear if CE2 cellular location affects CPT-11 anticancer activity. In the present study, we directly compared the influence of CE2 cellular location on substrate hydrolysis and CPT-11 cytotoxicity. We linked expression of CE2 and enhanced green fluorescence protein (eGFP) via a foot-and-mouth disease virus 2A (F2A) peptide to facilitate fluorescence-activated cell sorting to achieve similar expression levels of ER-located, secreted or membrane-anchored CE2. Soluble CE2 was detected in the medium of cells that expressed secreted and membrane-anchored CE2, but not in cells that expressed ER-retained CE2. Cancer cells that expressed all three forms of CE2 were more sensitive to CPT-11 as compared to unmodified cancer cells, but the membrane-anchored and ER-retained forms of CE2 were consistently more effective than secreted CE2. We conclude that expression of CE2 in the ER or on the membrane of cancer cells is suitable for enhancing CPT-11 anticancer activity.
Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan; Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
Yuan-Ting
YT
Hsieh
Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
Hsuan-Pei
HP
Lin
Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
Bing-Mae
BM
Chen
Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
Ping-Ting
PT
Huang
Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
Steve R
SR
Roffler
D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000494:pharmacology; D043182:Carboxylesterase / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects / Q000235:genetics; D054885:Cumulus Cells; D049452:Green Fluorescent Proteins; D045325:HCT116 Cells; D006801:Humans; D006868:Hydrolysis; D000077146:Irinotecan; D051379:Mice
D000972:Antineoplastic Agents, Phytogenic; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D000077146:Irinotecan; C517204:CES2 protein, human; D043182:Carboxylesterase; D002166:Camptothecin