C3 and neoplasm: However, conspicuous is the fact that the role of the axis in oncogenesis is rather ambiguous, since a number of studies have demonstrated that tumor grows under C3/C5 activation conditions through recruitment and activation of myeloid suppressor cells in tumors (Reis et al., 2018; Pio et al., 2013; Macor et al., 2018; Berraondo et al., 2016).