After a course of treatment of mice with Imatinib, we found that treatment of tumors carrying secondary mutation of KIT with Imatinib can’t inhibit the growth of tumor xenograft, while the tumor growth was inhibited by Imatinib when PI3 kinase association was lost (Fig. 5b, c), meaning that loss of PI3 kinase association improves the sensitivity of tumors carrying the secondary mutations of KIT to Imatinib treatment. The gene discussed is KIT; the disease is neoplasm.