The chemical composition and events related to the cytotoxic effects of propolis on osteosarcoma cells: A comparative assessment of Colombian samples

Abstract

Osteosarcoma (OSA) is a type of bone cancer showing an aggressive biological behavior with metastatic progression. Because propolis potential for the development of new antitumoral drugs has been indicated, we evaluated the chemical composition of Colombian propolis samples and the mechanisms involved in their cytotoxic effects on OSA cells. The chemical composition was analyzed by GC–MS and the DPPH free radical scavenging activity was measured. Cluster and principal components analysis were used to establish an association with their inhibitory concentration 50% (IC50). Cell viability was analyzed by MTT assay; apoptosis was determined by flow cytometry; mitochondrial membrane permeability and reactive oxygen species were evaluated by rhodamine 123 and DCFH‐DA. Transwell assay was used to evaluate the invasiveness of propolis‐treated cells. Samples were grouped: Cluster 1 contained diterpenes and benzophenones and showed the highest antiradical activity; Cluster 2 was characterized by triterpenes, fatty acid, and diterpenes. Usm contained diterpenes and triterpenes different of the other samples and Sil contained triterpenes and flavonoids. Apoptosis, mitochondrial membrane alteration, and suppression of cell invasion were the main mechanisms involved in the inhibition of OSA cells in vitro, suggesting the potential of Colombian propolis to discover new antitumor drugs.

Anticancer Activity of Propolis and Its Compounds

“…The Clusia type of propolis contains benzophenones derivatives and originates from the resin of flowers of Clusia sp. Other examples of tropical propolis is Pacific propolis characterized by content of C-prenylflavanones [ 3 , 18 , 19 ]. The chemical composition and biological activities of propolis extracts depend on the type of solvent used for the extraction.…”

Apoptosis-related gene expression induced by Colombian propolis samples in canine osteosarcoma cell line

“…Caj and Sil propolis samples had the highest amount of triterpenes (49.6% and 51.4%, respectively). In addition, Sil contained 7.9% of flavonoids [ 11 ].…”

“…From July to December of 2015, the samples were collected using plastic nets and by scraping the hives. Moreover, they were characterized chemically [ 11 ]. After grinding all the samples, we dissolved 4.5 g of propolis in 15 mL of 70% ethanol.…”

“…In Colombia, propolis samples collected in different regions have been chemically characterized, presenting similar components to those found in samples from the Clusia plant, which is native in other tropical countries, such as Cuba and Venezuela [ 10 ]. However, Colombian propolis contains diterpenes and triterpenes, which are still currently poorly known, and components such as eicosyl coumarate and garcinoic acid, which are not observed in other propolis types [ 11 , 12 ]. Propolis may affect both the intrinsic and extrinsic apoptosis pathways [ 13 , 14 ].…”

“…In human breast cell line MCF-7, propolis increases the activity of CASPASE 3 [ 15 , 16 ] and the immunoreactivity of CASPASES 6, 8, and 9 in cancer cells [ 13 ]; in human leukemic cell line U937, it decreases BCL-2 expression [ 14 , 15 ]. According to a previous study focusing on potential cytotoxicity, Colombian propolis samples can induce apoptosis in canine OSA cells [ 11 ].…”