Effects of Rapamycin on Breast Cancer Cell Migration through the Cross-Talk of MAPK Pathway.

Abstract

Phase I/II clinical studies with rapamycin analogs in breast and other cancers have demonstrated favorable responses. However, little is known on the effects of the mTOR inhibitor on breast cancer cell metastasis, which is a major cause of morbidity and death. We developed a highly sensitive 3-dimensional (3D) proliferation/invasion assay using quantitative bioluminescence (BL) imaging and applied this assay to evaluate the effects of rapamycin on the triple negative breast cancer cell line MDA-MB231. Without cytotoxicity of rapamycin on this cell line, rapamycin at 10nM inhibited the cell migration/invasion, but not at 1nM and 100nM, which was confirmed by the time-lapse single cell tracking analysis. The quantification of cytoskeleton changes showed most potent effects of 10nM rapamycin on the MDA-MB231 cells, with the formation and rearrangement of specialized cell membrane structures and actin fiber implicated in cell motility. Then, the Panorama Cell Signaling Antibody Microarray, enabling the global comparative analysis of cell signal proteins simultaneously, was exploited to analyze the effects of rapamycin on the cellular signaling network of the MDA-MB231 breast cancer cell line. 100nM rapamycin activated the MAPK pathway obviously, through the attenuated negative feedback of activated S6K1 to PI3K-Raf, which increased the expressions of activated Jun N-terminus kinase (JNK), Erk1/2, MEK-1, Raf-pS621, and MAPK-activated protein kinase 2 (MAPKAPK2) in the cells exposed to 100nM rapamycin. MEK inhibitor U0126 or PD98059 could restore the anti-migration effects of 100nM rapamycin on the MDA-MB231 cells. Furthermore, the combination of MEK inhibitors and rapamycin performed synergism on inhibiting the cell proliferation and migration/invasion. Accordingly, rapamycin at a certain dose suppresses MDA-MB231 cell migration/invasion, and the co-targeting of mTOR and MAPK pathways enhances the inhibition on cell proliferation and migration/invasion, underscoring the potential therapeutic utility of rapamycin, and rapamycin combining with MAPK inhibitors in triple negative breast cancer progression, and the results highlight the cross-talk homeostasis of mTOR and MAPK pathways in cancer treatment. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5080.

Simulated microgravity increases polyploid giant cancer cells and nuclear localization of YAP

“…Autophagy inhibition did not affect migration; previous experiments have shown reduction of migration in gastric cancer cells with bafilomycin treatment compared to autophagy induction 52 . Inhibition of migration is observed through longer rapamycin treatment, whereas acute treatment did not affect HUVEC migration 53 Longer treatment of rapamycin inhibits migration through negative feed-back of Pi3K-Raf signaling in breast cancer cells MDA-MB 231 54 . Short time exposure to rapamycin in our experiments did not inhibit migration, but instead increased to a small extent.…”

A Novel Rapamycin-Polymer Conjugate Based on a New Poly(Ethylene Glycol) Multiblock Copolymer

“…Rapamycin has been examined alone or in combination with other drugs for treatment of various cancers in clinical studies [3-5]. Although it has shown promising therapeutic effects, its clinical development was interrupted by poor aqueous solubility and preferential distribution in RBCs.…”

“…Rapamycin was approved as an immunosuppressive agent by the US Food and Drug Administration (FDA) in 1999. Due to its unique cytostatic effect, rapamycin has also entered into clinical trials to treat various cancers, including breast cancer, prostate cancer and glioblastoma [3-5]. The molecular mechanism of rapamycin is to inhibit the mammalian target of rapamycin (mTOR) signaling pathway by directly binding to FK-binding protein 12 (FKBP12) and mTOR1.…”

PML Surfs into HIPPO Tumor Suppressor Pathway

“…None of the signaling pathways known is as rich in WW domain-containing proteins as the Hpo pathway (Sudol and Harvey, 2010). The intact WW domains of YAP are required for their co-transcriptional activator function and promoting cell proliferation (Zhao et al, 2009). …”