Purification of anti‐colorectal cancer monoclonal antibody CO17 ‐ 1A from insect cell culture using a F rench press and sonication

Monoclonal antibody (m A b) CO17 ‐ 1A binds to GA733 , which is a tumor‐associated glycoprotein antigen highly expressed on the colorectal cancer cell surface. Thus, m A b CO17 ‐ 1A is considered a useful biomolecule for diagnosis and treatment against colorectal cancer. Previously, we established a baculovirus–insect cell expression system for the production of m A b CO17 ‐ 1A . In order to use m A b CO17 ‐ 1A as a diagnostic and therapeutic tool, however, the antibody must be properly purified from the insect cells. In this study, our aim was to investigate effective purification processes of m A b CO17 ‐ 1A expressed in S podoptera frugiperda ( S f 9 ) insect cells, using a F rench press and sonication for cell disruption. SDS‐PAGE confirmed that both m A b CO17 ‐ 1A and m A b CO17 ‐ 1A fused to the KDEL endoplasmic reticulum ( ER ) retention signal (m A b CO17 ‐ 1AK ) were expressed clearly in S f 9 insect cells. Western blot analysis showed that detection levels of m A b CO17 ‐ 1A and CO17 ‐ 1AK were higher when the insect cells were disrupted two times by the F rench press and then sonicated, compared to only one F rench press disruption plus sonication. Optical microscopy confirmed that insect cells treated with both the F rench press and sonication were properly disrupted. Analysis of gene sequence information on m A b CO17 ‐ 1A verified that a signal peptide is present but a transmembrane protein does not exist. These results suggest that cell disruption by the F rench press twice and sonication once is an effective method for improving purification efficiency.