Basic Helix-Loop-Helix Transcription Factors/metabolism; Dexamethasone/pharmacology; Drug Resistance, Neoplasm/genetics; Homeodomain Proteins/metabolism; Precursor T-Cell Lymphoblastic Leukemia-Lymphoma/drug therapy; Receptor, Notch1/antagonists & inhibitors; Receptors, Glucocorticoid/metabolism; Anti-Inflammatory Agents/pharmacology; Basic Helix-Loop-Helix Transcription Factors/antagonists & inhibitors; Basic Helix-Loop-Helix Transcription Factors/genetics; Blotting, Western; Chromatin Immunoprecipitation; Homeodomain Proteins/antagonists & inhibitors; Homeodomain Proteins/genetics; Humans; Mutation/genetics; Precursor T-Cell Lymphoblastic Leukemia-Lymphoma/genetics; Precursor T-Cell Lymphoblastic Leukemia-Lymphoma/pathology; RNA, Messenger/genetics; RNA, Small Interfering/genetics; Real-Time Polymerase Chain Reaction; Receptor, Notch1/genetics; Receptor, Notch1/metabolism; Receptors, Glucocorticoid/genetics; Reverse Transcriptase Polymerase Chain Reaction; Transcription Factor HES-1; Tumor Cells, Cultured