PURPOSE: We adopted a combinatorial approach with the joint application of γ-tocotrienol and jerantinine A at lower concentrations in order to minimize toxicity towards non-cancerous cells while improving the potency on brain cancer cells.
METHODS: The antiproliferative potency of individual γ-tocotrienol and jerantinine A as well as combined in low-concentration was firstly evaluated on U87MG cancer and MRC5 normal cells. Morphological changes, DNA damage patterns, cell cycle arrests and the effects of individual and combined low-concentration compounds on microtubules were then investigated. Finally, the potential roles of caspase enzymes and apoptosis-related proteins in mediating the apoptotic mechanisms were investigated using apoptosis antibody array, ELISA and Western blotting analysis.
RESULTS: Combinatorial study between γ-tocotrienol at a concentration range (0-24µg/ml) and fixed IC20 concentration of jerantinine A (0.16µg/ml) induced a potent antiproliferative effect on U87MG cells and led to a reduction on the new half maximal inhibitory concentration of γ-tocotrienol (i.e.tIC50=1.29µg/ml) as compared to that of individual γ-tocotrienol (i.e. IC50=3.17µg/ml). A reduction on undesirable toxicity to MRC5 normal cells was also observed. G0/G1 cell cycle arrest was evident on U87MG cells receiving IC50 of individual γ-tocotrienol and combined low-concentration compounds (1.29µg/ml γ-tocotrienol + 0.16µg/ml jerantinine A), whereas, a profound G2/M arrest was evident on cells treated with IC50 of individual jerantinine A. Additionally, individual jerantinine A and combined compounds (except individual γ-tocotrienol) caused a disruption of microtubule networks triggering Fas- and p53-induced apoptosis mediated via the death receptor and mitochondrial pathways.
CONCLUSIONS: These findings demonstrated that the combined use of lower concentrations of γ-tocotrienol and jerantinine A induced potent cytotoxic effects on U87MG cancer cells resulting in a reduction on the required individual concentrations and thereby minimizing toxicity of jerantinine A towards non-cancerous MRC5 cells as well as probably overcoming the high-dose limiting application of γ-tocotrienol. The multi-targeted mechanisms of action of the combination approach have shown a therapeutic potential against brain cancer in vitro and therefore, further in vivo investigations using a suitable animal model should be the way forward.
MATERIALS AND METHODS: Corneal epithelial cells were isolated from the corneas of rabbits (n = 6). The optimal dose of GH for CEC proliferation in both basal medium (BM) and cornea medium (CM) was determined via MTT (3-[4, 5-dimethyl thiazolyl-2]-2, 5-diphenyl tetrazolium bro- mide) assay. Morphology, gene and protein expressions, and cell cycle analysis of CECs were evaluated via phase contrast microscopy, real- time polymerase chain reaction, immunocytochemistry, and ow cytom- etry, respectively.
RESULTS: Corneal epithelial cells cultured in 0.0015% GH-supplemented media (BM + 0.0015% GH; CM + 0.0015% GH) demonstrated optimal proliferative capacity with normal polygonal- shaped morphology. Gelam honey potentiates cytokeratin 3 (CK3) gene expression in accordance with the cytoplasmic CK3 protein expression while retaining normal cell cycle of CECs.
CONCLUSION: Culture media treated with 0.0015% GH increased CEC proliferation while preserving its phenotypical features. This study demonstrated the potential devel- opment of GH-based topical treatment for super cial corneal injury.