tranilast and Neurofibromatosis-1

Neurofibromatosis type 1 (NF1) is caused by germline mutations in the NF1 gene and is characterized by café au lait spots and benign tumours known as neurofibromas. NF1 encodes the tumour suppressor protein neurofibromin, which negatively regulates the small GTPase Ras, with the constitutive activation of Ras signalling resulting from NF1 mutations being thought to underlie neurofibroma development. We previously showed that knockdown of neurofibromin triggers epithelial-mesenchymal transition (EMT) signalling and that such signalling is activated in NF1-associated neurofibromas. With the use of a cell-based drug screening assay, we have now identified the antiallergy drug tranilast (N-(3,4-dimethoxycinnamoyl) anthranilic acid) as an inhibitor of EMT and found that it attenuated the expression of mesenchymal markers and angiogenesis-related genes in NF1-mutated sNF96.2 cells and in neurofibroma cells from NF1 patients. Tranilast also suppressed the proliferation of neurofibromin-deficient cells in vitro more effectively than it did that of intact cells. In addition, tranilast inhibited sNF96.2 cell migration and proliferation in vivo. Knockdown of type III collagen (COL3A1) also suppressed the proliferation of neurofibroma cells, whereas expression of COL3A1 and SOX2 was increased in tranilast-resistant cells, suggesting that COL3A1 and the transcription factor SOX2 might contribute to the development of tranilast resistance.

Topics: Animals; Anti-Allergic Agents; Cell Line; Cell Proliferation; Down-Regulation; Epithelial-Mesenchymal Transition; Female; Gene Deletion; Genes, Neurofibromatosis 1; Germ-Line Mutation; HeLa Cells; Humans; Mice, SCID; Neoplasm Invasiveness; Neoplasms; Neovascularization, Physiologic; Neurofibromatosis 1; Neurofibromin 1; ortho-Aminobenzoates

Neurofibromas are benign tumors that comprise primarily of Schwann cells and fibroblasts. Mast cells have been found scattered in the tumor tissue, and their role in promoting the proliferation of neurofibroma has been suggested. Tranilast (N-[3,4-dimethoxycinnamolyl]anthranilic acid) is an anti-allergic drug that inhibits release of the chemical mediators from mast cells and it used for the treatment of keloids and hypertrophic scars by its inhibition of growth-promoting transforming growth factor (TGF)-beta(1) from fibroblasts. We assumed that tranilast would suppress neurofibroma cell growth. In order to prove this hypothesis, we investigated the effectiveness of tranilast in inhibiting the tumor growth using a new cell culture system obtained from patients with neurofibromas. We called this culture system with the mixture of Schwann cells and fibroblasts "NF1 cells culture". Mast cells were differentiated from CD34(+) peripheral blood mononuclear cells of normal healthy subjects, and were co-cultured with NF1 cells. Three days after tranilast (10 approximately 100 microM) added to the culture dishes, we counted viable cell numbers and measured the concentrations of TGF-beta(1), stem cell factor (SCF) and tryptase, which exists in the histamine granule, in the culture medium. Tranilast significantly suppressed proliferation of the NF1 cells and lowered the levels of TGF-beta(1), SCF and tryptase. These results suggest that tranilast retards tumor proliferation through not only suppression of cell growth factor, but also the inhibition of a chemical mediator released from mast cells. Thus, tranilast can be a potent therapeutic agent to inhibit the growth of neurofibromas.

Topics: Anti-Allergic Agents; Cell Proliferation; Cells, Cultured; Down-Regulation; Humans; Mast Cells; Neurofibromatosis 1; ortho-Aminobenzoates; Stem Cell Factor; Transforming Growth Factor beta; Tryptases

Topics: Antineoplastic Agents; Humans; Neurofibroma; Neurofibromatosis 1; ortho-Aminobenzoates; Treatment Outcome