Impairments in Rho GTPase Signaling Mediate the Inhibitory Effects of Metformin on the Survival and Migration of Neuroblastoma Cells

The aberrant activation of Rho GTPases are known to be associated with the progression of various cancers. In the present study we tested if metformin, an anti‐diabetic drug, targets Rho GTPases to exhibit antitumor activity against human neuroblastoma. Using xenograft mice model of human neuroblastoma, we demonstrate that metformin significantly inhibits the growth of tumors. In these tumors, metformin significantly activates Rac1 and Cdc42, and inhibits RhoA in a GST‐pull down assay. The inhibitors of Rac1 or Cdc42 as well as dominant negative forms of Rac1, Cdc42, and constitutively active form of RhoA protect cells from metformin‐induced apoptosis. Similarly, inhibitors of JNK, Rac1, and Cdc42, alone or in combination, attenuate cytotoxic effects of metformin. These gain‐in and loss‐off function studies further confirm that metformin impairs Rho‐GTPase signaling to initiate apoptosis via JNK pathway. In addition, wound‐healing and migration/invasion assays show that metformin at lower concentrations inhibits the migration/invasion of neuroblastoma cells. The activity assays, both in vitro and in vivo, further demonstrate that metformin targets Rho GTPase signaling to inhibit neuroblastoma cell migration. Since metformin is a safe drug our studies suggest that it is also a novel therapeutic agent for the treatment of neuroblastoma.