Construction of phosphorylatable chimeric monoclonal antibody CC49

Area of Science:

• Biochemistry
• Molecular Biology
• Immunology

Background:

• Monoclonal antibodies (mAbs) are crucial in cancer diagnostics and therapeutics.
• Enhancing mAb properties like specific radioactivity can improve their clinical utility.
• Phosphorylation is a key post-translational modification regulating protein function.

Purpose of the Study:

• To engineer chimeric monoclonal antibody CC49 (MAb-chCC49) with multiple phosphorylation sites.
• To evaluate the impact of these modifications on antibody phosphorylation and antigen binding.
• To assess the potential of these modified antibodies for cancer diagnosis and treatment.

Main Methods:

• Synthetic DNA fragments encoding phosphorylation sites were inserted into the MAb-chCC49 expression vector.
• Modified antibodies (MAb-chCC49K1 and MAb-chCC49-6P) were expressed in NS0 cells and purified.
• Phosphorylation was performed using the catalytic subunit of cAMP-dependent protein kinase and [gamma-32P]ATP.
• Binding affinity to TAG-72 expressing cells was assessed.

Main Results:

• Successfully generated MAb-chCC49 variants with two (MAb-chCC49K1) and six (MAb-chCC49-6P) phosphorylation sites per heavy chain.
• Both variants were efficiently phosphorylated to high specific activity.
• Phosphorylated antibodies retained their ability to bind TAG-72 antigens on cells.
• Multiple phosphorylation sites led to very high specific radioactivity.

Conclusions:

• Introduction of phosphorylation sites into mAbs is a viable strategy for enhancing their properties.
• Modified mAbs with multiple phosphorylation sites offer potential for improved cancer diagnostics and therapeutics.
• Cassettes of phosphorylation sites can be introduced into proteins without compromising functional activity.