The role of ABL kinases in medulloblastoma

Medulloblastoma is the most common malignant pediatric brain tumor, and leptomeningeal dissemination (LMD) of medulloblastoma portends a poorer prognosis at diagnosis and is incurable at recurrence. The biological mechanisms underlying LMD in medulloblastoma are largely unclear. The Abelson (ABL) family of non-receptor tyrosine kinases has been implicated in cancer cell migration, invasion, adhesion, and chemotherapy resistance, and these kinases are upstream mediators of the oncogene c-MYC in fibroblasts. However, their role in medulloblastoma has not yet been explored. Therefore, the purpose of this work is to elucidate the role of the ABL kinases, ABL1 and ABL2, in medulloblastoma LMD. We show here that ABL1/2 mRNA is highly expressed in human medulloblastoma tumor samples and cell lines and that pharmacologic inhibition of ABL kinases results in medulloblastoma cell death. Knockdown of the ABL kinase genes ABL1 and ABL2 results in decreased adhesion to the extracellular matrix protein, vitronectin, and decreased medulloblastoma proliferation in a mouse model of medulloblastoma LMD (resulting in decreased tumor burden with subsequent increased overall survival. Further, both pharmacologic inhibition of ABL1/2 and ABL1/2 knockdown resulted in decreased c-myc expression, revealing a putative signaling pathway. In summary, this work highlights the potential role of ABL kinases in medulloblastoma LMD via c-myc expression. Overall design: Genetic inactivation of ABL1 and ABL2 vs. scrambled controls in D283 medulloblastoma cells.