The Role of the Sonic Hedgehog Pathway for Prostate Cancer Progression

The hedgehog pathway plays a critical role in the development of prostate. In the previous funding period, we reported activation of hedgehog signaling in advanced and metastatic tumors. Here we report molecular mechanisms by which activated hedgehog signaling alter cell functions. In one cancer cell line, NCI-H209, we detected promoter methylation of SuFu. Ectopic expression of SuFu in NCI-H209 cells down-regulates hedgehog target gene expression and leads to inhibition of BrdU incorporation, a marker for cell proliferation. Thus, inactivation of SuFu is a mechanism by which hedgehog signaling is activated in human cancer. We also investigated the molecular basis by which PKA affects Gli1 activity. We find that activation of PKA retains Gli1 in the cytoplasm. Conversely, inhibition of PKA activity promotes nuclear accumulation of Gli1. Mutation analysis identifies T374 as a major PKA site determining Gli1 protein localization. In the three dimension structure, T374 resides adjacent to the basic-residue cluster of the nuclear localization signal NLS. Mutation of this residue to Asp Gli1T374D results in more cytoplasmic Gli1 whereas a mutation to Lys Gli1T374K leads to more nuclear Gli1. These data provide evidence to support a model that PKA regulates Gli1 localization, in part, through modulating the NLS function.