Non-histone nuclear factor HMGB1 is phosphorylated and secreted in colon cancers.
The high mobility group box 1 (HMGB1) protein, a non-histone nuclear factor, is overexpressed and localizes to the cytoplasm in some cancer cells. However, the mechanism of cytoplasmic HMGB1 transport, extracellular secretion, and its role in cancer progression is not clear. To simulate the activated state of HMGB1, we mutated serine residues of nuclear localization signals (NLSs) to glutamic acid and performed transfection assays. We carried out a kinase inhibitor study and evaluated the cell migration by invasion assay. We showed that phosphorylated HMGB1 localizes in the cytoplasm of colon cancer cells and also showed the interaction of PKC and HMGB1 by immunoprecipitation analysis. Concurrent mutations at six serine residues (35, 39, 42, 46, 53, and 181) to glutamic acid induced the nuclear to cytoplasmic transport of HMGB1, which was detected in the culture medium. We also observed that the secretion of HMGB1 correlated with increased cancer cell invasiveness. Our results suggest that phosphorylated HMGB1 is transported to the cytoplasm, is subsequently secreted from the cell, and has a role in tumor progression through the activation of genes related to cell migration.
Kang
Hyun Ju
HJ
Department of Pathology, Yonsei University College of Medicine, Seoul, Korea. hkyonsei@yuhs.ac
Lee
Hanna
H
Choi
Hee-Jung
HJ
Youn
Ju Ho
JH
Shin
Jeon-Soo
JS
Ahn
Yeong Hee
YH
Yoo
Jong Shin
JS
Paik
Young-Ki
YK
Kim
Hoguen
H
D000230:Adenocarcinoma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D014408:Biomarkers, Tumor / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D018450:Disease Progression; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D018698:Glutamic Acid / Q000378:metabolism; D024243:HMGB1 Protein / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism; D009154:Mutation; D009361:Neoplasm Invasiveness; D009363:Neoplasm Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D012694:Serine / Q000235:genetics; D015398:Signal Transduction; D014162:Transfection
D014408:Biomarkers, Tumor; D004791:Enzyme Inhibitors; D024243:HMGB1 Protein; D009363:Neoplasm Proteins; D018698:Glutamic Acid; D012694:Serine; D011493:Protein Kinase C