• Korean Journal of Pharmacognosy
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• v.41 no.1
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• pp.43-47
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• 2010

In order to screen new receptor tyrosine kinase inhibitor which is expected to be anticancer drug lead, we have investigated receptor tyrosine kinase inhibitory activity on the marine alga-derived symbiotic microorganisms (500 strains). The significant activities (over 70% inhibition at $10\;{\mu}g/ml$) were observed in the extracts of ten strains (Strain No.: MFA018, 019, 206, 242, 325, 335, 343, 344, 354, 356), isolated from marine red algae, five strains (Strain No.: MFA030, 126, 213, 324, 339), isolated from the brown algae, and one strain (Strain No.: MFA272), isolated from the marine green algae, respectively. Among the active strains, MFA019 and 356 showed strong receptor tyrosine kinase inhibitory activity with $IC_{50}$ values of 0.6 and $0.9\;{\mu}g/ml$, respectively.

• Journal of Veterinary Clinics
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• v.36 no.6
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• pp.319-324
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• 2019

Receptor tyrosine kinases (RTK) are major promising targets in anticancer therapy in human and veterinary medicine. Using immunohistochemistry method, we evaluated the expressionof five types RTK (PDGFR-α, PDGFR-β, VEGFR 2, c-Kit and Abl) in the six canine brain tumor samples (2 meningioma, 2 astrocytoma, 1 ependymoma and 1 choroid plexus papilloma). A total of five samples expressed PDGFR-β (5/6), one sample, the choroid plexus papilloma, expressed c-Kit (1/6), and a total of two samples expressed Abl (2/6). None of the samples showed expression of PDGFR-α and VEGFR 2. We demonstrate that a significant portion of canine brain tumors express tyrosine receptors for growth factors and show that these receptors generally localize to tumor cell membranes and the cytoplasm. Evaluation of immunohistochemical expression for the RTKs PDGFR-β, c-Kit, and Alb in canine brain samples reveals an interesting potential for molecular targeting by TKIs in therapeutic studies of canine brain tumors, and more studies will be needed to assess the interactions and efficacy of these RTKs and TKIs. Based on these results, we have some evidence for novel chemotherapeutic trials using TKIs for canine nervous tumors.

• Journal of Photoscience
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• v.9 no.2
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• pp.229-232
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• 2002

There are two distinct UV-responsive signaling pathways in UV-irradiated mammalian cells, i.e., the DNA damage-dependent and -independent pathways. The former occurs in nucleus and results in growth arrest and apoptosis via post-translational modification of p53. The latter is initiated by oxidative stress and/or by damages in cell membrane or cytoplasm, which activate signaling cascade through intracellular molecules including mitogen activated protein kinases (MAPK). In normal human fibroblastic cells, all of MAPK family members, extracellular signal-related kinases (ERK), c-Jun N-terminal kinases (JNK) and p38, were rapidly phosphorylated following UV-irradiation. ERK phosphorylation was suppressed by an inhibitor of receptor tyrosine kinases (RTK). As ERK usually responds to mitogenic stimuli from RTK ligands, UV-induced ERK phosphorylation may be linked to the proliferation of survived cells. In contrast, phosphorylation of JNK and p38, as well as apoptosis, were modulated by the level of UV-generated oxidative stress Therefore, JNK and p38 may take part in oxidative stress-mediated apoptosis. Phosphorylation of p53 at Ser and Thr residues are essential for stabilization and activation of p53. Among several sites reported, we confirmed phosphorylation at Ser-15 and Ser-392 after UV-irradiation. Both of these were inhibited by a phosphoinositide 3-kinase inhibitor, presumably due to the shutdown of signals from DNA damage to p53. Phosphorylation at Ser-392 was also sensitive to an antioxidant and a p38 inhibitor, suggesting that Ser-392 of p53 is one of the possible points where DNA damage-dependent and -independent apoptic signals merge. Thus, MAPK pathway links UV-induced intracellular signals to the nuclear responses and modifies DNA damage-dependent cellular outcome, resulting in the determination of cell death.