Reduction of complement factor H binding to CLL cells improves the induction of rituximab-mediated...

Area of Science:

• Immunology
• Hematology
• Oncology

Background:

• Rituximab (RTX) induces complement-dependent cytotoxicity (CDC) against chronic lymphocytic leukemia (CLL) cells.
• CLL cells possess regulators of complement activation (RCAs) that limit RTX-induced CDC.
• Factor H (fH), a fluid-phase RCA, has not been studied for its role in RTX resistance in CLL.

Purpose of the Study:

• To investigate the role of factor H (fH) in CLL cell resistance to RTX-induced CDC.
• To evaluate the potential of targeting fH to enhance RTX efficacy in CLL.

Main Methods:

• Assessed fH binding to CLL cells.
• Utilized complement-based lysis assays with CLL cells from therapy-naive patients.
• Tested the effect of human recombinant fH-derived short-consensus repeat 18-20 (hSCR18-20) on RTX-induced CDC.
• Examined the role of membrane-anchored RCAs (CD55, CD59) in CDC resistance.

Main Results:

• fH binds to CLL cells.
• hSCR18-20 significantly boosted RTX-induced CDC in both CDC responder and non-responder CLL cells.
• Enhanced CDC was specific for CD20(+) cells.
• CDC resistance was independent of CD55 and CD59, but their blockade further enhanced CDC.

Conclusions:

• Inhibition of fH binding by hSCR18-20 sensitizes CLL cells to RTX-induced CDC.
• Targeting fH represents a novel strategy to improve RTX-based immunochemotherapy for CLL patients.