ATM Paradoxically Promotes Oncogenic Transformation via Transcriptional Reprogramming.

The role of the ataxia-telangiectasia-mutated (ATM) gene in human malignancies, especially in solid tumors, remains poorly understood. In the present study, we explored the involvement of ATM in transforming primary human cells into cancer stem cells. We show that ATM plays an unexpected role in facilitating oncogene-induced malignant transformation through transcriptional reprogramming. Exogenous expression of an oncogene cocktail induced a significant amount of DNA double-strand breaks in human fibroblasts that caused persistent activation of ATM, which in turn enabled global transcriptional reprogramming through chromatin relaxation, allowing oncogenic transcription factors to access chromatin. Consistently, deficiencies in ATM significantly attenuated oncogene-induced transformation of human cells. In addition, ATM inhibition significantly reduced tumorigenesis in a mouse model of mammary cancer. ATM and cellular DNA damage response therefore play a previously unknown role in facilitating rather than suppressing oncogene-induced malignant transformation of mammalian cells. SIGNIFICANCE: These findings uncover a novel pro-oncogenic role for ATM and show that contrary to established theory, ATM does not always function as a tumor suppressor; its function is however dependent on cell type.