C-Raf modulates the mitochondrial membrane potential during apoptosis. A. Overexpression of C-Raf kinase in 32Dcl.3 cell lines. 32Dcl.3 cells expressing Mas-BXB fusion protein were maintained in IL3-containing medium. Expression of constitutively active Mas-BXB and inactive Mas-BXB K375W proteins was detected in mitochondrial but not cytosolic fractions using an anti-C-Raf antibody. Cell viability of 32Dcl.3 cell lines. 32Dcl.3 transfected cells were cultured without IL-3 for 24 hours and % viable cells was determined by trypan dye-exclusion.