[Novel Tyrosine Phosphorylation Signals in the Nucleus and on Mitotic Spindle Fibers and Lysosomes Revealed by Strong Inhibition of Tyrosine Dephosphorylation]

Protein-tyrosine phosphorylation is one of the posttranslational modifications and plays critical roles in regulating a wide variety of cellular processes, such as cell proliferation, differentiation, adhesion, migration, survival, and apoptosis. Protein-tyrosine phosphorylation is reversibly regulated by protein-tyrosine kinases and protein-tyrosine phosphatases. Strong inhibition of protein-tyrosine phosphatase activities is required to undoubtedly detect tyrosine phosphorylation. Our extremely careful usage of Na₃VO₄, a potent protein-tyrosine phosphatase inhibitor, has revealed not only the different intracellular trafficking pathways of Src-family tyrosine kinase members but also novel tyrosine phosphorylation signals in the nucleus and on mitotic spindle fibers and lysosomes. Furthermore, despite that the first identified oncogene product v-Src is generally believed to induce transformation through continuous stimulation of proliferation signaling by its strong tyrosine kinase activity, v-Src-driven transformation was found to be caused not by continuous proliferation signaling but by v-Src tyrosine kinase activity-dependent stochastic genome alterations. Here, I summarize our findings regarding novel tyrosine phosphorylation signaling in a spatiotemporal sense and highlight the significance of the roles of tyrosine phosphorylation in transcriptional regulation inside the nucleus and chromosome dynamics.

Dichloromethane fraction of Moringa oleifera leaf methanolic extract selectively inhibits breast cancer cells (MCF7) by induction of apoptosis via upregulation of Bax, p53 and caspase 8 expressions

Moringa oleifera is a well-known medicinal plant which has anti-cancer and other biological activities. This research aims to determine the cytotoxic and apoptotic effect of M. oleifera leave extract on the breast cancer (MCF7) cells. The extracts were prepared using hexane, dichloromethane, chloroform and n-butanol by fractionating the crude 80% methanol extract of the plant leaves. The cytotoxic effect of the extracts on MCF7 cells were determined using CellTiter 96® AQueous One Solution Cell Proliferation (MTS) assay. The apoptosis study was conducted using Annexin V-FITC analysis and confirmed by Western blotting using selected proteins, which are p53, Bax, cytochrome c and caspase 8. Our results showed that the dichloromethane (DF-CME-MOL) extract was selectively cytotoxic to MCF7 cells (5 μg/mL) without significantly inhibiting the non-cancerous breast (MCF 10A) cells. It had the highest selectivity index (SI) value of 9.5 among the tested extracts. It also induced early apoptosis and increased the expressions of pro-apoptotic proteins Bax, caspase 8 and p53 in MCF7 cells. Gas chromatography-mass spectrometry analysis (GC-MS) analysis showed that the major compounds found in DF-CME-MOL were benzeneacetonitrile, 4-hydroxy- and benzeneacetic acid, 4-hydroxy-, methyl ester among others that were detected. Thus, DF-CME-MOL extract was found to inhibit the proliferation of MCF7 cells by apoptosis induction, which is likely due to the activities of the detected phytochemical compounds of the extract.

Mitochondria-mediated Caspase-dependent and Caspase-independent apoptosis induced by aqueous extract from Moringa oleifera leaves in human melanoma cells

Malignant melanoma is a very aggressive and serious type of cutaneous cancer. Previous studies indicated the anti-cancer activity of aqueous extract of Moringa oleifera Lam. leaves (MOE) against a variety of cell lines. However, there has not been much research about the effect of MOE on melanoma. Therefore, this study was about to investigate the anti-proliferation mediated by apoptosis of MOE on human melanoma cell lines. Furthermore, the related molecular mechanisms of the apoptosis were also examined. An aqueous extract of Moringa oleifera leaves was prepared and the anti-proliferative activity on melanoma cells and normal cells was tested using WST-1 assay. The apoptotic hallmarks including DNA condensation and phosphatidylserine (PS) externalization were assessed. The expression of apoptosis-related genes and the depolarization of mitochondrial membrane potential were then examined to clarify the underlying molecular mechanisms. MOE inhibited cell growth of A375 cells and A2058 cells in a dose-dependent manner but had little effect on human normal fibroblasts. The cell growth inhibition was induced by apoptosis which was expressed via chromatin condensation and PS externalization. MOE decreased mitochondrial membrane potential. Additionally, MOE increased Bax/Bcl-2 ratio, activated Caspase-3/7, Caspase-9, PARP and AIF translocation, leading to apoptotic cell death. Our study indicated that MOE exerted significant anti-cancer effects on melanoma cells in vitro which involved mitochondria-mediated Caspase-dependent and Caspase-independent apoptosis pathways. These results provided a scientific approach for using Moringa oleifera leaves as an alternative therapy to treat skin cancer.