Effect of gentamicin after 24 h from treatment. (a) Cell morphology by hematoxylin–eosin staining; (b) MIB-1 immunohistochemistry staining; (c,d) HercepTest immunostaining. 10× magnification (a,b), 20× magnification (c), and 40× magnification (d); (e) densitometric analysis; (f) GADD45A gene expression, data are referred to the GM-untreated sample (control) set at 1. GAPDH expression was used as a housekeeping gene. RT-PCR analysis was performed in control and experimental NCI-N87 cells collected 24 h after 1.5 mM GM treatment. The data represent the mean ± SD of three independent experiments performed in duplicate (significance, * p < 0.001 versus control sample).