Perilla frutescens is an Asian dietary herb consumed as an essential seasoning in Japanese cuisine as well as used for a Chinese medicine. Here, we report that a newly found methoxyflavanone derivative from P. frutescens (Perilla-derived methoxyflavanone, PDMF; 8-hydroxy-5,7-dimethoxyflavanone) shows carcinostatic activity on human lung adenocarcinoma, A549. We found that treatment with PDMF significantly inhibited cell proliferation and decreased viability through induction of G/M cell cycle arrest and apoptosis. The PDMF stimulation induces phosphorylation of tumor suppressor p53 on Ser15, and increases its protein amount in conjunction with up-regulation of downstream cyclin-dependent kinase inhibitor p21 and proapoptotic caspases, caspase-9 and caspase-3. We also found that small interfering RNA knockdown of p53 completely abolished the PDMF-induced G/M cell cycle arrest, and substantially abrogated its proapoptotic potency. These results suggest that PDMF represents a useful tumor-preventive phytochemical that triggers p53-driven G/M cell cycle arrest and apoptosis.
Nuclear antigens are known to trigger off innate and adaptive immune responses. Recent studies have found that the complex of nucleic acids and core histones that are derived from damaged cells may regulate allergic responses. However, no fundamental study has been performed concerning the role of linker histone H1 in mast cell-mediated type I hyperreactivity. In this study, we explored the impact of histone H1 on mast cell-mediated allergic responses both in vitro and in vivo. In the course of a bona-fide experimental allergen sensitization model upon co-injection with alum adjuvant, ovalbumin (OVA), but not PBS, induced elevated levels of circulating histone H1. Intranasal challenge with histone H1 to OVA/alum- (but not PBS/alum)-sensitized mice induced significantly severer symptoms of allergic rhinitis than those in mice sensitized and challenged with OVA. A monoclonal antibody against histone H1 not only suppressed mast cell degranulation, but also ameliorated OVA-induced nasal hyperreactivity and IgE-mediated passive cutaneous anaphylaxis. Our present data suggest that nuclear histone H1 represents an alarmin-like endogenous mediator acting on mast cells, and that its blockage has a therapeutic potential for mast cell-mediated type I hyperreactivity.
Anti-cancer tyrosine kinase inhibitors (TKIs) are effective in many types of cancers including non-small cell lung cancer, while appearance of TKI-resistant tumors suggests a need for the development of their potentiation strategies. We have previously shown that a methoxyflavanone derivative from the Asian medicinal herb Perilla frutescens (Perilla-derived methoxyflavanone; PDMF) shows a prominent anti-tumor activity against A549 human lung adenocarcinoma. Here we show that PDMF and anti-cancer TKIs (nilotinib, bosutinib, dasatinib, and ponatinib) synergistically suppress proliferation of A549 cells. Flow cytometric analysis indicated that co-stimulation with nilotinib (4 μM) and PDMF induced G/M cell cycle arrest in low PDMF doses (10-50 μM), whereas this combination triggered de novo G arrest in higher PDMF dosages (50-125 μM). We also found that co-administration with nilotinib and PDMF significantly suppressed in vivo tumorigenicity of A549 cells in athymic nude mice.
Background: Perilla frutescens is a common traditional Chinese medicinal herb used for a variety of diseases, e.g. allergic asthma, cough and intestinal disorders. Flavonoids isolated from P. frutescens such as rosmarinic acid, caffeic acid and apigenin have been reported to inhibit proliferation of a variety of cancer cell lines. We recently identified a novel methoxyflavanone named PDMF (Perilla-derived methoxyflavanone) from P. frutescens as a candidate for anti-allergic drug. The objective of the study is to investigate antitumor potency of PDMF on A549 human lung adenocarcinoma and to elucidate its carcinostatic mechanisms.
Methods: Effect of PDMF on cell proliferation and viability of A549 cells were assessed by BrdU incorporation assay and trypan blue dye exclusion test. Cell cycle and apoptosis analyses were carried out by flow cytometry. To elucidate antitumor mechanisms of PDMF, expression and activation status of cell cycle/apoptosis regulators (p53/p21/BAX/caspases) were thoroughly analyzed by immunoblotting.
Results: Stimulation with PDMF not only triggered G2/M cell cycle arrest but also induced apoptosis of A549 cells in a dose-dependent manner. Mechanistically, PDMF stimulation significantly induced protein levels of p53 and its phosphorylated active forms (pSer15) accompanied by induction of p21 and BAX. We also found that proapoptotic caspase molecules (caspase 3, 8, and 9) were all activated upon stimulation with PDMF.
Conclusion: These results suggest that this Perilla-derived methoxyflavanone represents a useful cancer-preventive phytochemical that triggers G2/M arrest, apoptosis, and activation of p53 pathway.
Citation Format: Amer Ali Abd El Hafeez Mohamed, Takashi Fujimura, Rikiya Kamei, Noriko Hirakawa, Kenji Baba, Miyako Nakano, Kazuhisa Ono, Seiji Kawamoto. A novel methoxyflavanone from a Chinese medicinal herb (Perilla frutescens) induces G2/M cell cycle arrest and apoptosis in A549 human lung adenocarcinoma cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3040.
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