The knockdown of COL3A1 markedly suppressed the proliferation of tranilast-resistant neurofibroma cells (Fig. 8d), suggesting that COL3A1 is a major ECM component affecting the proliferation of neurofibromin-deficient cells, however, the depletion of COL3A1 did not increase tranilast sensitivity. Here, NF1 is linked to plexiform neurofibroma.