DRR drives brain cancer invasion by regulating cytoskeletal-focal adhesion dynamics.

Malignant glioma invasion is a primary cause of brain cancer treatment failure, yet the molecular mechanisms underlying its regulation remain elusive. We developed a novel functional-screening strategy and identified downregulated in renal cell carcinoma (DRR) as a regulator of invasion. We show that DRR drives invasion in vitro and in vivo. We found that while DRR is not expressed in normal glial cells, it is highly expressed in the invasive component of gliomas. Exploring underlying mechanisms, we show that DRR associates with and organizes the actin and microtubular cytoskeletons and that these associations are essential for focal adhesion (FA) disassembly and cell invasion. These findings identify DRR as a new cytoskeletal crosslinker that regulates FA dynamics and cell movement.

Inhibition of medulloblastoma cell invasion by Slit.

Invasion of brain tumor cells has made primary malignant brain neoplasms among the most recalcitrant to therapeutic strategies. We tested whether the secreted protein Slit2, which guides the projection of axons and developing neurons, could modulate brain tumor cell invasion. Slit2 inhibited the invasion of medulloblastoma cells in a variety of in vitro models. The effect of Slit2 was inhibited by the Robo ectodomain. Time-lapse videomicroscopy indicated that Slit2 reduced medulloblastoma invasion rate without affecting cell direction or proliferation. Both medulloblastoma and glioma tumors express Robo1 and Slit2, but only medulloblastoma invasion is inhibited by recombinant Slit2 protein. Downregulation of activated Cdc42 may contribute to this differential response. Our findings reinforce the concept that neurodevelopmental cues such as Slit2 may provide insights into brain tumor invasion.