Measurement of mRNA expression levels of key genes in response to different biguanides in human PitNET cell cultures and cell lines. (A, B, E) Effect of MF (10 mM), BF (5 mM), and PF (5 mM) on the expression levels of different genes in primary ACTHoma cell cultures (MF: n = 3; BF and PF: n = 2) and in the corticotropinoma AtT-20 cell line (n = 4). (C, D, F) Effect of MF, BF, and PF on expression levels in primary GHoma cell cultures (n = 4) and in the somatotropinoma GH3 cell line (n = 4). Expression levels were measured by quantitative RT-PCR and adjusted by normalization factor (NF). Data are expressed as percentage of vehicle-treated controls (set at 100%) within experiments. Values represent the mean ± SEM. Asterisks (*P < 0.05; **P < 0.01; ***P < 0.001) indicate statistically significant differences. In cases where fewer than three experiments were performed, no significance tests were performed.