Expression profile­driven discovery of AURKA as a treatment target for liposarcoma.

Liposarcoma (LPS) is one of the most frequently reported type of soft­tissue sarcoma (STS). Well­differentiated (WD) LPS and dedifferentiated (DD) LPS are the two most common subtypes. Chemotherapy has been considered to be ineffective in LPS, and novel treatment agents are thus necessary. In this study, we reanalyzed two published microarray data sets of LPS. By comparing the top 50 upregulated genes in DD LPS in both sets of data, we identified 12 overlapping genes. Of note, the top five gene sets enriched in DD LPS in both sets of data were involved in cell cycle regulation. Among the 12 overlapping genes, aurora kinase A (AURKA) is a well­known gene involved in cell cycle regulation; we thus further investigated this gene. AURKA was significantly upregulated in DD LPS, compared with WD LPS. Among 40 cases of DD LPS in GSE30929, patients with high AURKA expression in tumors had significantly worse distant recurrence­free survival than those with low expression. In an in vitro model, MLN8237, an AURKA inhibitor, could inhibit AURKA in LPS cell lines with a resultant G2/M arrest. MLN8237 was also reported to exert a cytotoxic effect by inducing apoptosis in LPS cell lines. Furthermore, except for cisplatin, MLN8237 had a significantly synergistic effect with chemotherapy agents against LPS. MLN8237 induced cellular senescence in LPS cell lines with increased expression of DcR2, a senescence biomarker, and upregulated expression of cytokines associated with the senescence­associated secretory phenotype, including interleukin (IL)­1α, IL­6 and IL­8. Our study identified AURKA as a potential biomarker for predicting poor prognosis in LPS. The findings of the present study suggested the potential of AURKA as a therapeutic target in LPS cell line models, while the novel combination of AURKA inhibitors and chemotherapy requires further investigation.

Identification of phenothiazine as an ETV1­targeting agent in gastrointestinal stromal tumors using the Connectivity Map.

Gastrointestinal stromal tumors (GISTs) are gastrointestinal tract sarcomas that commonly contain a mutation in the tyrosine kinases, KIT and platelet­derived growth factor receptor A (PDGFRA). Imatinib, sunitinib and regorafenib are all effective tyrosine kinase inhibitors; 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 pattern­matching 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 phenothiazine­class drugs). Western blot analysis demonstrated that all four drugs had ETV1­downregulating 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 extracellular­signal­regulated 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.