In vitro sensitivity to ganciclovir (GCV) of different cell types expressing TK. A, ganciclovir sensitivity of A375N-derived cell clones expressing TK driven by hSPPr and hSPPr(Δ10). Inset, TK and actin (ACTB) bands after semiquantitative reverse transcription-PCR. B, bystander effect induced by melanoma cells expressing TK driven by the two versions of SPARC promoter. C, ganciclovir sensitivity of a cell culture mix composed of Mel-(Δ10)-TK and either BAEC or WI-38 VA cells (1:1 cell ratio). ***, P < 0.001.