Trametinib plus 4-Methylumbelliferone Exhibits Antitumor Effects by ERK Blockade and CD44 Downregulation and Affects PD-1 and PD-L1 in Malignant Pleural Mesothelioma

Hiroyuki Cho, Seiji Matsumoto, Yoshiko Fujita, Ayumi Kuroda, Toshi Menju, Makoto Sonobe, Nobuyuki Kondo, Ikuko Torii, Takashi Nakano, Primo N Lara, David R Gandara, Hiroshi Date, Seiki Hasegawa

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10 Scopus citations


Introduction Malignant pleural mesothelioma (MPM) is a highly aggressive malignancy in which the mitogen-activated protein kinase pathway plays a critical role in the regulation of tumorigenesis. Hyaluronic acid (HA) is a major component of the extracellular matrix, and elevated HA levels with a concurrent increase in malignant properties are associated with MPM. Methods We evaluated the effects of trametinib, a mitogen-activated protein kinase (MEK) inhibitor, and 4-methylumbelliferone (4-MU), an HA synthesis inhibitor, alone and in combination on MPM cells in vitro and in vivo. We studied the effects of trametinib, 4-MU, and their combination on MPM cells by using cell viability assays, Western blot analysis, and a mouse xenograft model. Results Trametinib and 4-MU exhibited antiproliferative activity in MPM cells. Trametinib blocked MEK-dependent extracellular signal-regulated kinase (ERK) phosphorylation and decreased CD44 expression in a concentration-dependent manner. Trametinib inhibited the expression of Fra-1 (the activator protein 1 [AP1] component), inhibited ERK phosphorylation, and decreased CD44 expression. 4-MU inhibited ERK phosphorylation but not CD44 expression. In a mouse xenograft model, trametinib and 4-MU alone suppressed tumor growth compared with a control. The combination had a greater inhibitory effect than either monotherapy. Immunohistochemical analysis showed that trametinib treatment alone significantly reduced expression of programmed cell death 1 ligand 1. Furthermore, the combination of trametinib and 4-MU resulted in higher expression of programmed cell death 1 and programmed cell death 1 ligand 1 than did the 4-MU treatment alone. Conclusions Our results suggest that trametinib and 4-MU are promising therapeutic agents in MPM and that further study of the combination is warranted.

Original languageEnglish (US)
Pages (from-to)477-490
Number of pages14
JournalJournal of Thoracic Oncology
Issue number3
StatePublished - Mar 1 2017



  • 4-Methylumbelliferone
  • CD44
  • ERK
  • Malignant pleural mesothelioma
  • Trametinib

ASJC Scopus subject areas

  • Oncology
  • Pulmonary and Respiratory Medicine

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