Planta Med 2009; 75 - SL70
DOI: 10.1055/s-0029-1234325

Dry olive leaf extract promotes avant-garde apoptosis in melanoma cells; switch from caspase- dependent to caspase- independent pathway

S Mijatovic 1, J Radovic 1, G Timotijevic 2, M Mojic 1, D Miljkovic 1, D Dekanski 3, S Stosic-Grujicic 1
  • 1Institute for Biological Research „Sinisa Stankovic“
  • 2Institute of Molecular Genetics and Genetic Engineering, Belgrade, Serbia
  • 3Galenika a.d. – R&D Institute, Despota Stefana 142. Belgrade. Serbia

Aim of work: It is well known that malignant melanomas respond poorly to chemotherapy. Having in mind efficacy of some traditional approaches in treatment of apoptotic unresponsive cancers, it was of interests to evaluated sensitivity of melanomas to compounds present in total dry olive leaf extract (DOLE) with known antimicrobial, anti-inflammatory and antioxidative properties.

Applied methods: Crystal violet and MTT viability assays, analysis of cell cycle distribution of PI stained cells, Anex/PI double staining for detection of apoptotic/necrotic cell death, Western blot analysis of relevant protein and Real time PCR analysis of gene expression; solid melanoma were induced by subcutaneous inoculation of B16 cells in singeneic C57BL/6 strain.

Main results: DOLE strongly abrogated growth of B16 cells in vitro as well as in vivo. Its intraperitoneal application resulted in significant reduction of tumor size. Decreased B16 cell viability was associated with its morphological transformation, Go/G1 arrest and delayed apoptosis with recognizable signs of early and late phases. Surprisingly, key executioner molecules – caspases were continuously inhibited at both- protein and gene levels while the expression of caspase-independent endonuclease – Endo G was exaggerated, thus indicating its involvement in finalization of apoptotic process. Time limited upregulation of cell protective Bcl-2 within first two hours of incubation with DOLE, followed with its rapid and permanent decrease, possibly contributed to switch from caspase-dependent to caspase-independent pathway.

Conclusions: Compounds present in DOLE are capable to overcome insensitivity of melanoma cells to classical apoptosis by unconventional mechanisms, indicating that data presented are worthy of further investigation.

Acknowledgements: This work was supported by Serbian Ministry of Science and Technological Development (Grant No 143029)