Purification and partial characterization of a malignancy-associated glycoprotein

Area of Science:

• Biochemistry
• Oncology
• Immunology

Background:

• A previously reported cancer-associated glycoprotein (Cc) showed potential malignancy markers.
• Preliminary studies suggested Cc was immunologically related to alpha 1-acid glycoprotein, necessitating further investigation.
• Some Cc preparations contained multiple components, prompting a re-evaluation of isolation and characterization.

Purpose of the Study:

• To re-examine and refine the isolation and characterization of the cancer-associated glycoprotein (Cc).
• To develop a purification protocol that distinguishes Cc from alpha 1-acid glycoprotein.
• To confirm the distinct biochemical and physical properties of the purified Cc.

Main Methods:

• Modified purification protocol using pleural fluid from cancer patients.
• Immunoaffinity chromatography employing an alpha 1-acid glycoprotein antibody column.
• Sodium dodecyl sulfate-polyacrylamide electrophoresis (SDS-PAGE) for molecular weight determination.
• Amino-terminal sequencing and carbohydrate analysis.

Main Results:

• A single component glycoprotein (Cc) with Mr 53,000 was isolated after removing alpha 1-acid glycoprotein.
• The purified Cc exhibited a blocked amino terminus and complex, asparagine-linked saccharide units.
• Cc was biochemically distinct from alpha 1-acid glycoprotein and other circulating glycoproteins based on molecular weight, isoelectric point, and composition.
• One preparation showed an increased Mr of 59,000 due to heightened glycosylation.

Conclusions:

• The refined isolation protocol successfully purified a distinct cancer-associated glycoprotein (Cc).
• The purified Cc is biochemically unique compared to alpha 1-acid glycoprotein and other known glycoproteins.
• Variations in glycosylation can account for molecular weight differences observed in Cc preparations.