HeLa cells came from the American Type Culture Collection (ATCC, Manassas, USA). Cell line was cultured as a standard monolayer in the complete growth medium, supplemented with fetal bovine serum 10 % v/v (FBS, Gibco), L-glutamine 1% v/v (Sigma-Aldrich), and the antibiotics, namely: streptomycin [10 000 U ml -1 ] and penicillin [10 mg ml -1 ] 1% v/v (Sigma-Aldrich). Cells were cultured in 5% CO2 atmosphere at 37 °C. HeLa cell line was cultured in Dulbecco's Modified Eagle's Medium (DMEM) with low glucose content (Institute of Immunology and Experimental Technology, Wrocław, Poland).