Reversibility and adjustability of macrolide-responsive SEAP expression in HT-1080 and MCF-7 transduced by transgenic AAV type 2-derived particles. (A) HT-1080 and (B) MCF-7 were transduced with pDF143-derived AAV particles (2000 genomic particles/cell) and six equal populations (1–6) were cultivated in media containing different antibiotic concentrations. Cells were (i) cultivated in the presence (+++) or absence (---) of EM over 9 days, (ii) cultivated in the presence (++-) or absence (--+) of EM over 6 days and then incubated in reversed EM conditions for the remaining three days or (iii) cells were cultivated in medium whose EM status was alternated every three days +EM to --EM to +EM (+-+) or from --EM to +EM to --EM (-+-) and SEAP expression was quantified. Adjustability of SEAP expression of pDF143 (1000 genomic particles/cell) (C) and pDF51/77 (500 genomic particles/cell) (D) in HT-1080 and MCF-7 cultivated for 48 h in the presence of increasing EM concentrations. SEAP expression is shown in units/liter (U/l) as defined by Schlatter et al. . Abbreviations: EM, erythromycin; SEAP, human placental secreted alkaline phosphatase. Abbreviations: EM, erythromycin; SEAP, human placental secreted alkaline phosphatase.