Treatment of eyelid epithelial neoplasm by targeting Sonic hedgehog signaling: An experimental study

Purpose: To evaluate the effect of cyclopamine, an inhibitor of the Sonic hedgehog (Shh) signal, on the growth of an epithelial neoplasm. Methods: Chemically induced eyelid tumors in XPC-null mice (n = 40) were treated daily with a subcutaneous injection of cyclopamine (1mg/animal) for 7 days. The animals were killed after bromodeoxyuridine (BrdU) labeling, and the tumors were histologically examined. An in vitro study was conducted by using a squamous cell carcinoma (SCC) cell line. The SCC cells were treated with 0, 12.5, or 25.0 mu g/ml recombinant Shh (rShh) and either 0 or 100 mu M cyclopamine, and cell proliferation was evaluated by using an MTT assay. Cells from this cell line were also implanted subcutaneously in nude mice (n = 8) to develop tumors, and the effect of cyclopamine administration was examined in the developed tumors. Results: Histology showed that cyclopamine treatment suppressed BrdU incorporation and induced apoptosis in the majority of cells in tumors chemically induced in the eyelid of the XPC-null mice. Cell proliferation of the SCC cell line was enhanced by adding rShh, and this effect was abolished by adding cyclopamine. Proliferation of the SCC cell line was not affected by adding cyclopamine in the absence of rShh. On the other hand, the SCC cells expressed Shh in vivo in tumors developed in nude mice, but cycloparnine suppressed cell proliferation in the tumors, and the Shh-signaling pathway was inhibited by cyclopamine-induced apoptosis. Conclusions: Cyclopamine inhibits proliferation and induces apoptosis in epithelial tumor cells in vivo. The Shh-signaling pathway may be a potential therapeutic target for patients with eyelid tumors.