In Vitro and In Vivo Anti-tumoral Effects of the Flavonoid Apigenin in Malignant Mesothelioma

Our plain-English summary of In Vitro and In Vivo Anti-tumoral Effects of the Flavonoid Apigenin in Malignant Mesothelioma, by L. Masuelli, M. Benvenuto, R. Mattera, et al (Frontiers in Pharmacology, 2017).

The study

• Authors: L. Masuelli, M. Benvenuto, R. Mattera, E. Di Stefano, E. Zago, G. Taffera, I. Tresoldi, M.G. Giganti, G.V. Frajese, G. Berardi, A. Modesti, R. Bei
• Journal: Frontiers in Pharmacology
• Published: 2017;8:373
• Cited by: 57 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant mesothelioma (MM) is a tumor arising from mesothelium. MM patients' survival is poor. The polyphenol 4',5,7,-trihydroxyflavone Apigenin (API) is a "multifunctional drug". Several studies have demonstrated API anti-tumoral effects. However, little is known on the in vitro and in vivo anti-tumoral effects of API in MM. Thus, we analyzed the in vitro effects of API on cell proliferation, cell cycle regulation, pro-survival signaling pathways, apoptosis, and autophagy of human and mouse MM cells. We evaluated the in vivo anti-tumor activities of API in mice transplanted with MM #40a cells forming ascites. API inhibited in vitro MM cells survival, increased reactive oxygen species intracellular production and induced DNA damage. API activated apoptosis but not autophagy. API-induced apoptosis was sustained by the increase of Bax/Bcl-2 ratio, increase of p53 expression, activation of both caspase 9 and caspase 8, cleavage of PARP-1, and increase of the percentage of cells in subG1 phase. API treatment affected the phosphorylation of ERK1/2, JNK and p38 MAPKs in a cell-type specific manner, inhibited AKT phosphorylation, decreased c-Jun expression and phosphorylation, and inhibited NF-κB nuclear translocation. Intraperitoneal administration of API increased the median survival of C57BL/6 mice intraperitoneally transplanted with #40a cells and reduced the risk of tumor growth. Our findings may have important implications for the design of MM treatment using API.

In plain English

This laboratory study tested apigenin, a flavonoid found in fruits and vegetables, on malignant mesothelioma (MM) cells. The authors treated three human MM cell lines and one mouse line with apigenin at 6.25 to 100 µM. The human lines were MM-B1 (biphasic), MM-F1 (fibromatous) and H-Meso-1 (epithelioid); the mouse line was #40a. Apigenin reduced cell growth. The concentration needed to halve growth after 72 hours ranged from 34.31 µM (H-Meso-1) to 56.82 µM (#40a). In the cells, apigenin increased reactive oxygen species, raised a DNA-damage marker, and triggered apoptosis (programmed cell death) but not autophagy. In mice, groups of six received abdominal injections of #40a cells, plus weekly abdominal injections of apigenin (20 mg/kg) or solvent alone. These treatments started at the same time as the cells were injected. Median survival was 12 weeks with apigenin versus 5.5 weeks with solvent (p = 0.0009). In this survival analysis, the hazard ratio for solvent-treated relative to apigenin-treated mice was 23.17 (95% confidence limits 3.617 to 148.4). The authors called this the risk of tumor growth. They concluded that apigenin inhibited mesothelioma cell growth in the laboratory and in mice. No people were treated.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory study: experiments on cultured mesothelioma cell lines (in vitro) plus an animal experiment in mice (in vivo)
• Who was studied: Three human MM cell lines (MM-F1 fibromatous/sarcomatous, MM-B1 biphasic, H-Meso-1 epithelioid) and the mouse MM cell line #40a. For the animal experiment, 6-to-8-week-old C57BL/6 mice, 6 per group, were each injected in the abdomen with 1 million #40a cells
• Exposure: The exposure studied was apigenin, not asbestos. Cells received apigenin at 6.25 to 100 µM or the solvent DMSO. Mice received weekly abdominal (intraperitoneal) injections of 20 mg/kg apigenin or the solvent, starting at the same time as the tumor cells were injected
• Main results:
  • Concentrations of apigenin needed to reduce cell growth by 50% after 72 hours: 49.16 plus or minus 2.52 µM (MM-B1), 46.95 plus or minus 1.69 (MM-F1), 34.31 plus or minus 1.55 µM (H-Meso-1), and 56.82 plus or minus 4.69 (mouse #40a)
  • In all MM cell lines, apigenin increased reactive oxygen species production compared with solvent, and the increase rose with dose
  • Apigenin at 50 µM for 24 hours significantly increased gamma-H2AX, a marker of DNA damage, in all MM cell lines
  • Apigenin did not induce autophagy in the MM cell lines
  • In all MM cell lines, apigenin increased the share of cells in the sub-G1 phase (a sign of apoptosis), and the increase rose with dose
  • Apigenin caused the signaling protein NF-kB to accumulate outside the nucleus in the three human lines, but not in the mouse #40a cells
  • In mice, after 2 weeks, mean abdominal circumference (a measure of tumor fluid) was 6.9 cm in apigenin-treated mice versus 7.8 cm in control mice
  • All six control mice were euthanized at 5 weeks (three mice) or 6 weeks (three mice) because of tumor size
  • Median survival was 12 weeks in apigenin-treated mice versus 5.5 weeks in solvent-treated mice
  • Table 2 reports the survival analysis of the mice: a hazard ratio of 23.17 for control versus apigenin, with 95% confidence limits of 3.617 to 148.4
  • The authors' text describes this hazard ratio as the risk of tumor growth in solvent-treated mice relative to apigenin-treated mice
• The authors' conclusion: The authors concluded that apigenin inhibited mesothelioma cell growth in the laboratory and in mice by targeting different signaling pathways and inducing apoptosis. They said their findings may bear on designing MM treatment that uses apigenin together with other drugs

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Mesothelium, Apoptosis, Ascites, Reactive Oxygen Species (ROS), Translocation, Median Overall Survival.

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