Melittin Induced G1 Cell Cycle Arrest and Apoptosis in Chago-K1 Human Bronchogenic Carcinoma Cells and Inhibited the Differentiation of THP-1 Cells into Tumour- Associated Macrophages

Document Type: Research Articles

Authors

1 Department of Biology, Faculty of Science, Chulalongkorn University, 254 Phayathai Road, Bangkok, Thailand.

2 Homerton College, University of Cambridge, Hills Road, Cambridge CB2 8PH, UK.

3 Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, Japan.

4 Program in Biotechnology, Faculty of Science, Chulalongkorn University, 254 Phayathai Road, Bangkok, Thailand.

5 Institute of Biotechnology and Genetic Engineering, Chulalongkorn University, 254, Phayathai Road, Bangkok, Thailand.

Abstract

Background: Bronchogenic carcinoma (lung cancer) is one of the leading causes of death. Although many
compounds isolated from natural products have been used to treat it, drug resistance is a serious problem, and alternative
anti-cancer drugs are required. Here, melittin from Apis mellifera venom was used, and its effects on bronchogenic
carcinoma cell proliferation and tumour-associated macrophage differentiation were evaluated. Methods: The half
maximal inhibitory concentration (IC50) of melittin was measured by MTT. Cell death was observed by annexin V
and propidium iodide (PI) co-staining followed by flow cytometry. Cell cycle arrest was revealed by PI staining and
flow cytometry. To investigate the tumour microenvironment, differentiation of circulating monocytes (THP-1) into
tumour-associated macrophages (TAMs) was assayed by sandwich-ELISA and interleukin (IL)-10 levels were determined.
Cell proliferation and migration was observed by flat plate colony formation. Secretion of vascular endothelial growth
factor (VEGF) was detected by ELISA. The change in expression levels of CatS, Bcl-2, and MADD was measured by
quantitative RT-PCR. Results: Melittin was significantly more cytotoxic (p < 0.01) to human bronchogenic carcinoma
cells (ChaGo-K1) than to the control human lung fibroblasts (Wi-38) cells. At 2.5 μM, melittin caused ChaGo-K1
cells to undergo apoptosis and cell cycle arrest at the G1 phase. The IL-10 levels showed that melittin significantly
inhibited the differentiation of THP-1 cells into TAMs (p < 0.05) and reduced the number of colonies formed in the
treated ChaGo-K1 cells compared to the untreated cells. However, melittin did not affect angiogenesis in ChaGo-K1
cells. Unlike MADD, Bcl-2 was up-regulated significantly (p < 0.05) in melittin-treated ChaGo-K1 cells. Conclusion:
Melittin can be used as an alternative agent for lung cancer treatment because of its cytotoxicity against ChaGo-K1
cells and the inhibition of differentiation of THP-1 cells into TAMs.

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