Biological age = 13.3 + 0.122 × BMI + 0.107 × SBP + 21.0 × age group + (-0.014) × Apolipoprotein A-I fragment (m/z 2883.99) + 0.004 × Fibrinogen alpha chain fragment (m/z 3060.13) + 0.011 × Complement C3 fragment (m/z 2190.59) + (-0.005) × Complement C4-A fragment (m/z 1898.21) + 0.019 × Breast cancer type 2 susceptibility protein fragment (m/z 1607.84)(1). The gene discussed is C4A; the disease is cancer.