An excessive Shc level is associated with abnormal activation of theERK signaling pathway [55], which, inturn, significantly affects the development and progression of malignancies,including the sensitivity of malignant cells to chemotherapeutic drugs.Suppression of MCTS1 expression in immortalized cell lines ofbreast and lung cancer by RNA interference decreases the levels of p66, p52,and p46 isoforms of the Shc protein [35]. The gene discussed is SHC1; the disease is lung carcinoma.