C3 and neoplasm: Of the 91 frequently-identified proteins in the perilymph, four proteins were shown by univariate linear regression to be significantly correlated to tumor-associated hearing loss: Ig gamma-4 chain C region (P01857; p = 0.005); Ig kappa chain C region (P01834; p = 0.015); Complement C3 (P01024; p = 0.016) and immunoglobulin heavy constant gamma 3 (P01860; p = 0.023) (Table 2).