The mechanisms and origins for the Pd- and Ni-catalyzed regioselective hydrosilylation of allene have been investigated by means of density functional theory (DFT) calculations. The free-energy profiles of Pd- and Ni-catalyzed reactions with small and bulky N-heterocyclic carbene (NHC) ligands are calculated to determine the mechanism for regioselectivities. The calculation results show that different metals (Ni vs Pd) lead to regiochemical reversals for the hydrosilylation of allene. The allylsilane is the major product via palladium catalysis with small NHC ligand, while the vinylsilane is the major product via nickel catalysis with bulky NHC ligand. Both electronic and steric factors play a key role in the regioselectivities for the hydrosilylation of allene via Pd and Ni catalysts. The calculation results are in good agreement with observed regioselectivities and could provide insights into the design of new catalysts for the regioselectivity of hydrosilylation reactions.
Valid evidence has demonstrated that microRNAs have critical functions in cancer genesis and tumor progression. In the present study, aberrant expression of microRNA-149 (miR-149) was confirmed in non-small cell lung cancer (NSCLC) tissues. Low expression of miR-149 was associated with malignant clinical features and poor survival. Gain- and loss-of-function experiments demonstrated that miR-149 inhibited NSCLC tumor growth and metastasis in vitro and in vivo. Furthermore, oncogenic transcription factor FOXM1 was confirmed as a direct target of miR-149 in NSCLC. Cyclin D1 and MMP2 served as downstream targets of FOXM1 and were also inhibited by miR-149. In summary, the present study indicated that downregulation of miR-149 in NSCLC predicted poor clinical outcomes. miR-149 suppresses tumor growth and metastasis in NSCLC by inhibiting the FOXM1/cyclin D1/MMP2 signaling pathway.
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