Inhibitory effect of pirfenidone on glioblastoma cell lines: Implications for treatment of neurofibromatosis

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder characterized by diverse cutaneous, neurological, skeletal, and neoplastic manifestations with no standard drug treatment options available. Pirfenidone is an oral agent undergoing clinical investigation in NF1, where its antifibrotic properties are used to target the fibrotic component of plexiform neurofibromas. The effect of pirfenidone on other cells in these complex tumors is unknown. We studied the effects of pirfenidone on malignant glioma cell lines to take advantage of easily cultured and rapidly growing cells with similar biologic properties to NF1-derived tumors. On a standardized MTS assay, pirfenidone showed dose-dependent inhibition of cell proliferation. Using a tritiated thymidine assay, dose-dependent DNA synthesis inhibition was seen as early as 2 hours after treatment. Gelatin and casein zymography showed inhibition of matrix metallopeptidase 2 (MMP-2) activity at a time point when no inhibition of proliferation was noted. Western blotting with an antibody to epidermal growth factor receptor (EGFR) phosphotyrosine residues documented dose-dependent inhibition of EGFR phosphorylation. An 8-hour measurement of apoptosis using propidium iodide flow cytometry revealed a large sub-G₀ population of cells upon treatment of cells with 10 mg/mL of pirfenidone. These results suggest that pirfenidone has antitumor effects on malignant gliomas, which is partly mediated through inhibition of EGFR phosphorylation.