Cell Culture and Transfection Protocol

HeLa cells (kind gift from Prof. Dr. C. Azzalin, ETH Zurich, Switzerland) and human dermal fibroblasts (106–05N, Sigma-Aldrich, St. Louis, MI) were cultured in DMEM medium supplemented with 10% fetal bovine serum and 1% (v/v) penicillin/streptomycin in a 5% CO₂ atmosphere. THP1 monocytes (kind gift from Dr. H.-D. Beer, University of Zurich, Switzerland) and SW480 cells engineered for overproduction or down-regulation of HtrA1^{17 (link),18 (link)} (kind gift from Prof. Dr. M. Ehrmann, University Duisburg-Essen, Germany) were cultured in RPMI medium supplemented with 10% fetal bovine serum, 1% (v/v) penicillin/streptomycin plus G418 or puromycin, respectively, in a 5% CO₂ atmosphere. Transfection was performed using Lipofectamine 2000 according to the manufacturer’s instructions.