[Background] Haptoglobin (Hpt) is an acute inflammatory glycoprotein which mainly produced in the liver. We have previously reported that fucosylated Hpt (Fuc-Hpt) is observed in the sera of patients with cancers of various organs, whereas there is a trace of that in the sera of healthy individuals on ground that fucosyltransferases hardly express in the liver. Therefore, Fuc-Hpt is currently under development as a novel cancer biomarker. However, it has not been clarified where and how Fuc-Hpt is produced in cancer patients. We elucidated the production mechanism using cancer cell lines.
[Methods] Human liver cancer cell line and two human colon cancer cell lines were used. Hpt was purified from the cell-culture supernatant using the antibody column of Hpt. Amount of Hpt from each cell line was measured by WB. The cell-culture supernatant of the colon cancer cell lines were added to the liver cancer cell line and were cultured. N-Glycans of Hpt were released with PNGase F, and the released N-glycans were analyzed by LC-ESI MS.
[Results] Hpt was produced by the liver cancer cell line, but not by the colon cancer cell lines. Hpt was also produced in the liver cancer cell line cultured with the cell-culture supernatant of the colon cancer cell lines. Interestingly, there was difference with fucosylation between these Hpts.
[Conclusion] We concluded that Fuc-Hpt would be not produced by cancer cells of patients with colon cancer because colon cancer cell lines did not produce Hpt. Fucosylation of Hpt produced by the liver cancer cell line co-cultured with conditioned medium of the colon cancer cell line was changed, compared to Hpt produced by the liver cancer cell line. Therefore, it is suggested that the inducing substance which changes the fucosylation of Hpt would be produced by colon cancer cells.
[Keywords] haptoglobin, fucosylation, cancer-biomarker