Harmine Induces Adipocyte Thermogenesis through RAC1-MEK-ERK-CHD4 Axis.
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ABSTRACT:
SUBMITTER: Nie T
PROVIDER: S-EPMC5090989 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Cancer cells are able to survive under conditions that cause endoplasmic reticulum stress (ER-stress), and can adapt to this stress by upregulating cell-survival signalling pathways and down-regulating apoptotic pathways. The cellular response to ER-stress is controlled by the unfolded protein response (UPR). Small Rho family GTPases are linked to many cell responses including cell growth and apoptosis. In this study, we investigate the function of small GTPases in cell survival under ER-stress. Using siRNA screening we identify that RAC1 promotes cell survival under ER-stress in cells with an oncogenic N92I RAC1 mutation. We uncover a novel connection between the UPR and N92I RAC1, whereby RAC1 attenuates phosphorylation of EIF2S1 under ER-stress and drives over-expression of ATF4 in basal conditions. Interestingly, the UPR connection does not drive resistance to ER-stress, as knockdown of ATF4 did not affect this. We further investigate cancer-associated kinase signalling pathways and show that RAC1 knockdown reduces the activity of AKT and ERK, and using a panel of clinically important kinase inhibitors, we uncover a role for MEK/ERK, but not AKT, in cell viability under ER-stress. A known major activator of ERK phosphorylation in cancer is oncogenic NRAS and we show that knockdown of NRAS in cells, which bear a Q61 NRAS mutation, sensitises to ER-stress. These findings highlight a novel mechanism for resistance to ER-stress through oncogenic activation of MEK/ERK signalling by small GTPases.
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Project description:Background Hepatocellular carcinoma (HCC) is a common lethal malignant tumor worldwide. Circular RNAs (circRNAs) have been reported to affect the development of human cancers, including HCC. In this project, we aim to clarify the functional effect of circular CDR1as (circ_CDR1as) on HCC progression. Methods Quantitative real-time polymerase chain reaction (qRT-PCR) or Western blot is implemented to detect the expression of circ_CDR1as, microRNA (miR)-1287 and Raf-1 proto-oncogene, serine/threonine kinase (Raf1). Cell proliferation is assessed via colony formation and 3-(4, 5)-dimethylthiazole-2-y1)-2, 5-biphenyl tetrazolium bromide (MTT) assays. Cell migration and invasion are measured by Transwell assay. The target relationship between miR-1287 and circ_CDR1as or Raf1 is validated through dual-luciferase reporter assay. The levels of epithelia–mesenchymal transition (EMT) markers and the MEK/ERK signal pathway-related proteins are examined by Western blot. Model in nude mice is constructed to determine the role of circ_CDR1as in vivo. Results Expression of circ_CDR1as and Raf1 is elevated, while miR-1287 expression is decreased in HCC. Depletion of circ_CDR1as or Raf1 could inhibit proliferation and metastasis of HCC cells. Besides, circ_CDR1as regulates Raf1 expression by targeting miR-1287. MiR-1287 upregulation or Raf1 depletion could partially counterbalance circ_CDR1as depletion-mediated inhibitory effects on HCC cell behaviors. Moreover, circ_CDR1as depletion represses HCC progression through inactivating MEK/ERK pathway. In addition, circ_CDR1as depletion suppresses tumor growth in vivo via regulating miR-1287/Raf1 pathway. Conclusion Circ_CDR1as depletion inhibits HCC cell proliferation and metastasis by miR-1287/Raf1 and MEK/ERK pathways, highlighting a promising molecular target for HCC treatment.
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Project description:Background Colon cancer is a common malignancy of the digestive tract. The search for effective drugs to treat colon cancer has become the focus of current researches. Tanshinone IIA (Tan IIA) is a fat-soluble component extracted from tanshinone, a traditional Chinese medicine. Tan IIA can modulate the occurrence and development of tumors, but its effect on autophagy in colon cancer cells has not been reported. Methods Two types of colon cancer cell lines were selected and different concentrations of Tan IIA were used to treat cells at different time points. Cell Counting Kit-8 assay (CCK-8) was used to detect the effect of Tan IIA on cell proliferation; transmission electron microscopy was used to observe the formation of autophagosomes; reverse transcription-polymerase chain reaction (RT-qPCR) and western blot were used to detect the expression of autophagy related genes and proteins. Cell transfection was used to interfere with MEK (mitogen-activated extracellular signal-regulated kinase) expression, and RT-qPCR and western blot were used to detect the expression of MEK/ERK/mTOR pathway-related proteins. Results Tan IIA resulted in a significant reduction in the viability of the two kinds of colon cancer cells. The number of autophagosomes increased significantly after the treatment of Tan IIA into these cells. Addition of autophagy inhibitor 3-MA (3-Methyladenine) improved the increase of autophagosomes in cells induced by Tan IIA. At the same time, Tan IIA induced the expression of autophagy-related proteins in the two colon cancer cell lines. When Tan IIA induced autophagy in colon cancer cells, the expression of MEK/ERK/mTOR pathway-related proteins increased significantly. After interfering with the expression of MEK, the expression of autophagy decreased significantly, indicating that Tan IIA promoted autophagy of colon cancer cells through MEK/ERK/mTOR pathway. Conclusions Tan IIA stimulates autophagy in colon cancer cells through MEK/ERK/mTOR pathway, hence inhibiting the growth of colon cancer cells.
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