Effect of the STAT3 inhibitor STX-0119 on the proliferation of a temozolomide-resistant glioblastoma cell line

Abstract

Abstract. Glioblastoma multiforme (GBM) is one of the most malignant and aggressive tumors and has a very poor prognosis, with a median survival time of less than 2 years. Once recurrence develops, there are few therapeutic approaches to control the growth of glioblastoma. In particular, temozolomide (TMZ)-resistant (TMZ-R) GBM is very difficult to treat, and a novel approach to overcome resistance is eagerly awaited. Previously, we reported a novel small molecule inhibitor of STAT3 dimerization, STX-0119, as a cancer therapeutic. In the current study, the efficacy of STX-0119 was evaluated against our established TMZ-resistant U87 cell line using quantitative PCR-based gene expression analysis, in vitro assay and animal experiments. The growth inhibitory effect of STX-0119 on U87 and TMZ-R U87 cells was moderate (IC 50 , 34 and 45 µM, respectively). In particular, STX-0119 did not show significant inhibition of U87 tumor growth; however, it suppressed the growth of the TMZ-R U87 tumor in nude mice by more than 50%, and prolonged the median survival time compared to the control group. Quantitative PCR revealed that YKL-40, MAGEC1, MGMT, several EMT genes, mesenchymal genes and STAT3 target genes were upregulated, but most of those genes were downregulated by STX-0119 treatment. Furthermore, the invasive activity of TMZ-R U87 cells was significantly inhibited by STX-0119. YKL-40 levels in TMZ-R U87 cells and their supernatants were significantly decreased by STX-0119 administration. These results suggest that STX-0119 is an efficient therapeutic to overcome TMZ resistance in recurrent GBM tumors, and could be the next promising compound leading to survival prolongation, and YKL-40 may be a possible surrogate marker for STAT3 targeting.

Combination of a STAT3 Inhibitor and an mTOR Inhibitor Against a Temozolomide-resistant Glioblastoma Cell Line

“…transplanted mice showed significant resistance to TMZ and a shorter survival time in vivo compared to the parental U87 cell line, as shown in our previous study (14). STX-0119 alone showed a moderate inhibitory effect on TMZR U87 tumor growth in nude mice.…”

“…Cell proliferation was examined using the WST-1 assay (Dojin Kagaku Corp., Kumamoto, Japan) described previously (14). Briefly, 1×10 4 parental U87 or TMZ-R U87 cells were seeded into each well of a 96-well micro-culture plate (Corning, NY, USA) and compounds ranging from 0-200 μM were added alone or combination.…”

“…TMZ-resistant (R) U87 cells were established using a TMZ-dose-escalation method up to 150 μM, were maintained at a dose of 100 μM TMZ and were used for in vitro and in vivo experiments (14). Antibodies against STAT3, phospho-STAT3 (Y705), cleaved caspase-3, EGFR, phospho-EGFR (Y845, Y1173), Ras, PI3 kinase p85, phospho-PI3 kinase p85 (Y458), Akt, phospho-Akt1 (S473), mTOR, phospho-mTOR (S2448), S6, phospho-S6 (S235, S236), 4E-BP1, phospho-4E-BP1 (T37, T46), B-Raf, phospho-B-Raf (S445), extracellular signalregulated kinase (ERK)1/2, mitogen-activated protein kinase (MAPK), phospho-ERK1/2 pMAPK (T202, Y204), p38 MAPK and phospho-p38 MAPK (T180, Y182) were purchased from Cell Signaling Technology, Inc. (Danvers, MA, USA) and BectonDickinson (BD) Biosciences (Franklin Lakes, NJ, USA) for Western blotting (WB).…”

“…Previously, we identified a novel inhibitor of STAT3 dimerization, STX-0119, that exhibited a potent anti-tumor effect on a TMZ-resistant U87 glioma cell line, and demonstrated that anti-tumor activity was partly mediated by a down-regulation of YKL-40 (13)(14)(15). In the present study, we focused on cancer signaling in the TMZ-resistant glioma cell line, in which the STAT3 and PI3K/Akt/mTOR pathways were highly activated, and investigated the effect of a combination therapy of the STAT3 inhibitor (STX-0119) and mTOR inhibitor (rapamycin) on a TMZ-resistant glioblastoma cell line in vitro and in vivo.…”

Alteration of DNA damage signaling pathway profile in radiation-treated glioblastoma stem-like cells

“…With the administration of the standard treatment of maximal safe surgical resection followed by radiotherapy combined with concomitant and adjuvant temozolomide (TMZ) chemotherapy, newly diagnosed patients with GBM demonstrate an average survival time of only 12-14 months (2). Almost one-half of patients with GBM do not survive the first year subsequent to diagnosis (3)(4)(5)(6).…”