Identification of phenothiazine as an ETV1-targeting agent in gastrointestinal stromal tumors using the Connectivity Map

Chueh Chuan Yen*, Li Tzong Chen, Chien Feng Li, San Chi Chen, Wei Yang Chua, Yung Chan Lin, Chiao Han Yen, Yen Chun Chen, Muh Hwa Yang, Yee Chao, Jonathan A. Fletcher

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Gastrointestinal stromal tumors (GISTs) are gastrointestinal tract sarcomas that commonly contain a mutation in the tyrosine kinases, KIT and platelet-derived growth factor receptor A (PDGFRA). Imatinib, sunitinib and regorafenibarealleffectivetyrosinekinaseinhibitors;however, acquired resistance is inevitable. The E26 variant 1 (ETV1) pathway has been found to be a key downstream effector of KIT and is therefore a reasonable therapeutic target for this disease. In this study, we explored the potential agents targeting ETV1 in GISTs by uploading an ETV1 knockout gene signature of GIST cell lines to the pattern-matching software ‘Connectivity Map’. The activity and mechanisms of identified agents were examined using an in vitro model. Four drugs were identified: Suberanilohydroxamic acid and trichostatin [two histone deacetylase inhibitors (HDACIs)] and trifluoperazine and thioridazine (two phenothiazine-class drugs). Western blot analysis demonstrated that all four drugs had ETV1-downregulating effects. As HDACIs have been previously studied in GISTs, we focused on phenothiazine. Phenothiazine was found to exert cytotoxicity and to induce apoptosis and autophagy in GISTs. Treatment with phenothiazine had little effect on the KIT/AKT/mammalian target of rapamycin (mTOR) pathway, but instead upregulated extracellular-signal-regulated kinase (ERK) activity. A combination of phenothiazine and a MEK inhibitor had a synergistic cytotoxic effect on GISTs. Western blot analysis indicated that ELK1 and early growth response 1 (EGR1) were activated/upregulated following phenothiazine treatment, and the MEK inhibitor/phenothiazine combination downregulated the ERK/ELK1/EGR1 pathway, resulting in diminished autophagy, as well as enhanced apoptosis. On the whole, the findings of this study established phenothiazine as a novel class of therapeutic agents in GIST treatment and demonstrate that a combination of phenothiazine and MEK inhibitor has great potential for use in the treatment of GISTs.

Original languageEnglish
Pages (from-to)536-546
Number of pages11
JournalInternational journal of oncology
Issue number2
StatePublished - 2019


  • Connectivity Map
  • E26 variant 1
  • Gastrointestinal stromal tumors
  • Phenothiazine


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