Cytoskeletal dynamics and mitochondrial rearrangements drive cell fate upon antibody-induced complement activation in DLBCL

Complement-dependent cytotoxicity (CDC) is an important effector function of various therapeutic antibodies. Cancer resistance to CDC is primarily attributed to extracellular factors. Using diffuse large B-cell lymphoma (DLBCL) models, we elucidated intracellular evasion mechanisms. By CRISPR-Cas9 library screening, we identified mitochondrial damage and reactive oxygen species as the key intracellular drivers of CDC. CDC resistance was linked to augmented mitochondrial mass, elongated mitochondria and reduced mitophagy, and decreased expression of actin-related genes. Actin downregulation in CDC-resistant cells occurred specifically within the mitochondria, connecting mitochondrial rearrangements and cytoskeletal dynamics with resistance. Stimulating actin polymerization could partially overcome CDC resistance. Of clinical significance, we observed a positive association between the cytoskeleton and antibody responses in DLBCL patient samples. In conclusion, our study unveils novel intracellular resistance mechanisms to antibody-induced CDC, highlighting the critical roles of mitochondrial rearrangements and cytoskeletal dynamics in CDC. We propose that decreased mitochondrial actin prevents overload of the mitophagy pathway, thereby reducing CDC. (Figure presented.)