3549

IHH

indian hedgehog;IHH;indian hedgehog

HHG-2|Indian hedgehog homolog|indian hedgehog protein

2q33-q35

protein-coding

Runx2, required for bone formation, is ectopically expressed in breast cancer cells. To address the mechanism by which Runx2 contributes to the osteolytic disease induced by MDA-MB-231 cells, we investigated the effect of Runx2 on key components of the "vicious cycle" of transforming growth factor beta (TGFbeta)-mediated tumor growth and osteolysis. We find that Runx2 directly up-regulates Indian Hedgehog (IHH) and colocalizes with Gli2, a Hedgehog signaling molecule. These events further activate parathyroid hormone-related protein (PTHrP). Furthermore, Runx2 directly regulates the TGFbeta-induced PTHrP levels. A subnuclear targeting deficient mutant Runx2, which disrupts TGFbeta-induced Runx2-Smad interactions, failed to induce IHH and downstream events. In addition, Runx2 knockdown in MDA-MB-231 inhibited IHH and PTHrP expression in the presence of TGFbeta. In vivo blockade of the Runx2-IHH pathway in MDA-MB-231 cells by Runx2 short hairpin RNA inhibition prevented the osteolytic disease. Thus, our studies define a novel role of Runx2 in up-regulating the vicious cycle of metastatic bone disease, in addition to Runx2 regulation of genes related to progression of tumor metastasis.

Pancreatic cancer often presents in advanced stages and is unresponsive to conventional treatments. Thus, the need to develop novel treatment strategies for pancreatic cancer has never been greater. Here, we report that combination of focal irradiation with hedgehog (Hh) signaling inhibition exerts better than additive effects on reducing metastases. In an orthotopic model, we found that focal irradiation alone effectively reduced primary tumor growth but did not significantly affect metastasis. We hypothesized that cancer stem cells (CSC) of pancreatic cancer are responsible for the residual tumors following irradiation, which may be regulated by Hh signaling. To test our hypothesis, we showed that tumor metastasis in our model was accompanied by increased expression of CSC cell surface markers as well as Hh target genes. We generated tumor spheres from orthotopic pancreatic and metastatic tumors, which have elevated levels of CSC markers relative to the parental cells and elevated expression of Hh target genes. Irradiation of tumor spheres further elevated CSC cell surface markers and increased Hh target gene expression. Combination of Hh signaling inhibition with radiation had more than additive effects on tumor sphere regeneration in vitro. This phenotype was observed in two independent cell lines. In our orthotopic animal model, focal radiation plus Hh inhibition had more than additive effects on reducing lymph node metastasis. We identified several potential molecules in mediating Hh signaling effects. Taken together, our data provide a rationale for combined use of Hh inhibition with irradiation for clinical treatment of patients with pancreatic cancer.