The invention encompasses methods for treating or preventing diseases and disorders associated abnormal cell growth, for example, treating or preventing cancer or tumor growth, by administering to a subject in need thereof a composition comprising a therapeutically or prophylactically effective amount of a compound that downregulates DDX3, for example a fused diimidazodiazepine ring compound or a pharmaceutically acceptable salt thereof. The invention also encompasses the use of DDX3 as a biomarker for diagnostic and treatment purposes, for example, to identify a hyperproliferative disorder susceptible to treatment by down regulation of DDX3.