bisabolol and Neoplasms

The oxidative pentose phosphate pathway (PPP) contributes to tumour growth, but the precise contribution of 6-phosphogluconate dehydrogenase (6PGD), the third enzyme in this pathway, to tumorigenesis remains unclear. We found that suppression of 6PGD decreased lipogenesis and RNA biosynthesis and elevated ROS levels in cancer cells, attenuating cell proliferation and tumour growth. 6PGD-mediated production of ribulose-5-phosphate (Ru-5-P) inhibits AMPK activation by disrupting the active LKB1 complex, thereby activating acetyl-CoA carboxylase 1 and lipogenesis. Ru-5-P and NADPH are thought to be precursors in RNA biosynthesis and lipogenesis, respectively; thus, our findings provide an additional link between the oxidative PPP and lipogenesis through Ru-5-P-dependent inhibition of LKB1-AMPK signalling. Moreover, we identified and developed 6PGD inhibitors, physcion and its derivative S3, that effectively inhibited 6PGD, cancer cell proliferation and tumour growth in nude mice xenografts without obvious toxicity, suggesting that 6PGD could be an anticancer target.

Topics: AMP-Activated Protein Kinase Kinases; AMP-Activated Protein Kinases; Humans; Lipogenesis; Neoplasms; Oxidative Stress; Pentose Phosphate Pathway; Phosphogluconate Dehydrogenase; Protein Serine-Threonine Kinases; Ribulosephosphates; Signal Transduction

Despite enormous scientific and economic effort tumour still is one of the most terrible pathologies among human population all over the world. Products derived from the plant kingdom have often offered an opportunity to counteract or alleviate this illness. Here, we summarize the short story of the study of an extraordinary effect of one plant compound towards transformed cells derived from highly malignant tumours. Alpha-bisabolol, a sesquiterpene widely present in plants, selectively kills transformed cells by apoptosis without affecting the viability of normal cells. One of its intracellular targets seems to be situated on mitochondria and is possibly identified as the permeability transition pore, as judged from rapid mitochondrial membrane potential dissipation induced by alpha-bisabolol and the failure to kill cells in the presence of cyclosporine A. Preferential adsorption of alpha-bisabolol into lipid rafts, rich in tumour cells, may explain the selective action of this compounds towards tumour cells. Furthermore, Surface Plasmon Resonance analysis indicates that alpha-bisabolol directly interacts with Bid protein, a member of the Bcl2 family deeply involved in apoptosis, suggesting a possibility that Bid, or similar protein(s), may be involved in a putative intracellular transport system of alpha-bisabolol from plasma membrane to mitochondria. Experiments with animals indicate that alpha-bisabolol is not toxic and is accumulated, through blood flow, in every tissues examined. Further animal studies to test its effect are currently under way.

Topics: Animals; Apoptosis; Cell Line, Tumor; Humans; Models, Biological; Monocyclic Sesquiterpenes; Neoplasms; Plant Extracts; Sesquiterpenes; Signal Transduction