Letrozole inhibits ER-α36-mediated ERK and Akt phosphorylation. Hec1A cells were pre-treated with 10 nM aromatase inhibitor letrozole (Lanes 3 and 4) for 1 h and then the cells were treated with vehicle (DMSO) (Lanes 1) and 10 nM testosterone (Lanes 2 and 4) for 5 min. Phospho-ERK1/2 (A) or phospho-Akt (B) were examined with specific antibodies. The same blot was stripped and probed with anti-total ERK or Akt antibodies. Hec1A cells were treated with 10 nM testosterone (Lanes 2) or together with 10 nM aromatase inhibitor letrozole (Lanes 3) overnight, and then aromatase expression was detected by Western blot using specific antibody against aromatase (C).