Activity of the novel dual phosphatidylinositol 3-kinase/mammalian target of rapamycin inhibitor NVP-BEZ235 against osteosarcoma

Abstract

Keywords: MEK/Erk and chemo-resistance, NVP-BEZ235, osteosarcoma, PI3K-Akt-mTOR signaling Abbreviations: mammalian target of rapamycin (mTOR); mTOR complex 1 (mTORC1); mTOR complex 2 (mTORC2); phosphoinositide-dependent protein kinase-1 (PDK1); phosphatidylinositol 3-kinase (PI3K); receptor tyrosine kinases (RTKs).Recent studies have identified that constitutively active phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling is an important feature of osteosarcoma, where it promotes cell proliferation, survival, and chemo-resistance. Here, we studied the therapeutic potential of NVP-BEZ235, a novel dual PI3K/mTOR dual inhibitor, on osteosarcoma cells in vivo and in vitro. NVP-BEZ235 was cytotoxic and cytostatic to a panel of osteosarcoma lines (MG-63, U2OS and SaOs-2), where it induce apoptosis and cell-cycle arrest. At the molecular level, NVP-BEZ235 inhibited PI3K-AKT-mTORC1 activation and downregulated cyclin D1/cyclin B1 expressions, while increasing MEK/Erk phosphorylation in osteosarcoma cells. MEK/Erk inhibitors PD98059 and MEK-162 increased NVP-BEZ235 activity on osteosarcoma cells. In vivo, oral NVP-BEZ235 inhibited U2OS xenograft in SCID mice, and its antitumor efficiency was further enhanced by MEK-162 co-administration. Taken together, our findings indicate that dual inhibition of PI3K and mTOR with NVP-BEZ235, either alone or in combination with MEK/Erk inhibitors, may be an efficient treatment for osteosarcoma.

The anti-cancer activity of the mTORC1/2 dual inhibitor XL388 in preclinical osteosarcoma models

“…We studied the potential effect of XL388 on OS cell apoptosis. As described in our previous study [3], three independent apoptosis assays, including TUNEL staining assay, caspase-3 activity assay and histone DNA ELISA assay, were applied. Results from these assays demonstrated that XL388 induced significant apoptosis activation in MG-63 cells (Figure 2A–2C).…”

“…XL388 showed a dose-dependent effect in promoting MG-63 cell apoptosis (Figure 2A–2C). To study the effect of apoptosis in XL388-induced cytotoxicity, various caspase-dependent apoptosis inhibitors were utilized [3]. As demonstrated, the pan-caspase inhibitor (z-VAD-fmk, vad), the caspase-3 specific inhibitor (z-DVED-fmk, dved) and the caspase-8 specific inhibitor (z-ITED-fmk, ited) all remarkably inhibited XL388-induced MG-63 cell apoptosis (TUNEL assay, Figure 2D).…”

“…Therefore, our group [3, 4] and others have been focusing on exploring novel and more efficient anti-OS agents [1]. Molecularly-targeted agents are being tested [1, 2].…”

“…Molecularly-targeted agents are being tested [1, 2]. Overactivation of mammalian target of rapamycin (mTOR) is observed in many human OS tissues [3, 5–7], which is often associated with cancer progression and poor prognosis [3, 7]. Our group [3] and others have demonstrated that mTOR is vital for several key OS cell functions, such as cell growth, proliferation, and survival, as well as apoptosis-resistance and metastasis.…”

“…Preclinical studies have implied a therapeutic value of the mTOR inhibitors for OS [3, 8, 9]. It is known that mTOR forms at least two multi-protein complexes, including the traditional mTOR complex 1 (mTORC1) and later discovered mTORC2 [10–12].…”