Involvement of ST6Gal I in the biosynthesis of a unique human colon cancer biomarker candidate, alpha2,6-sialylated blood group type 2H (ST2H) antigen.
The alpha2,6-sialylated blood group type 2H (ST2H) antigen (Fucalpha1-2(NeuAcalpha2-6)Galbeta1-4GlcNAcbeta1-3Galbeta1-4Glc-Cer) is a fucoganglioside found in human colon cancer tissues. To elucidate an enzyme responsible for the ST2H antigen formation, we screened some partially purified candidate enzymes, alpha2,6-sialyltransferases, ST6Gal I and ST6Gal II, and alpha1,2-fucosyltransferases, FUT1 and FUT2 for their activities towards pyridylaminated type 2H (Fucalpha1-2Galbeta1-4GlcNAcbeta1-3Galbeta1-4Glc-PA) or LS-tetrasaccharide c (LST-c: NeuAcalpha2-6Galbeta1-4GlcNAcbeta1-3Galbeta1-4Glc-PA) as acceptor substrates. Here we show the ST6Gal I transfers NeuAc from the donor CMP-NeuAc to the terminal Gal of PA-type 2H, which formed the ST2H antigen, but the others could not synthesize it. Using a recombinant ST6Gal I, enzymatic reactions with two types of acceptors, PA-type 2H and PA-lacto-N-neotetraose (LNnT), were kinetically analysed. On the basis of catalytic efficiency (V(max)/K(m)), the specificity of ST6Gal I towards the PA-type 2H was estimated to be 42 times lower than that for PA-LNnT. The overexpression of ST6Gal I in human colon cancer DLD-1 cells effectively resulted in the ST2H antigen formation, as judged by LC-ESI-IT-MS. Many lines of evidence suggest the up-regulation of ST6Gal I in human colon cancer specimens. Collectively, these findings indicate that ST6Gal I is responsible for ST2H antigen biosynthesis in human colon cancer cells.
Korekane
Hiroaki
H
Department of Disease Glycomics (Seikagaku Corporation), The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.
Matsumoto
Akio
A
Ota
Fumi
F
Hasegawa
Tomoko
T
Misonou
Yoshiko
Y
Shida
Kyoko
K
Miyamoto
Yasuhide
Y
Taniguchi
Naoyuki
N
D015703:Antigens, CD / Q000378:metabolism*; D000951:Antigens, Neoplasm / Q000096:biosynthesis*; D014408:Biomarkers, Tumor / Q000096:biosynthesis; D001789:Blood Group Antigens / Q000096:biosynthesis*; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000175:diagnosis*; D005647:Fucosyltransferases / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D012799:Sialyltransferases / Q000378:metabolism*; D013379:Substrate Specificity; D000097631:Galactoside 2-alpha-L-fucosyltransferase; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase
D015703:Antigens, CD; D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D001789:Blood Group Antigens; D005647:Fucosyltransferases; D012799:Sialyltransferases; D000097631:Galactoside 2-alpha-L-fucosyltransferase; C093493:ST6GAL1 protein, human; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase; C549032:ST6GAL2 protein, human