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• Chondrosarcoma stem cells (ChSCs) are radioresistant and are suppressed by miR-34. • mTOR inhibition by Rapamycin targets ChSCs via FOXO3 and miR-34. • Combination of carbon-ion therapy with mTOR inhibitors effectively controls ChSCs. High-grade chondrosarcomas are chemo- and radio-resistant cartilage-forming tumors of bone that often relapse and metastase. Thus, new therapeutic strategies are urgently needed. Chondrosarcoma cells (CH-2879) were exposed to carbon-ion irradiation, combined with miR-34 mimic and/or rapamycin administration. The effects of treatment on cancer stem cells, stemness-associated phenotype, radioresistance and tumor-initiating properties were evaluated. We show that high-grade chondrosarcoma cells contain a population of radioresistant cancer stem cells that can be targeted by a combination of carbon-ion therapy, miR-34 mimic administration and/or rapamycin treatment that triggers FOXO3 and miR-34 over-expression. mTOR inhibition by rapamycin triggered FOXO3 and miR-34, leading to KLF4 repression. Our results show that particle therapy combined with molecular treatments effectively controls cancer stem cells and may overcome treatment resistance of high-grade chondrosarcoma. [ABSTRACT FROM AUTHOR]

Plants are a rich source for bioactive compounds. However, plant extracts can harbor a mixture of bioactive molecules that promote divergent phenotypes and potentially have confounding effects in bioassays. Even with further purification and identification, target deconvolution can be challenging. Corynoline and acetylcorynoline, are phytochemicals that were previously isolated through a screen for compounds able to induce mitotic arrest and polyploidy in oncogene expressing retinal pigment epithelial (RPE) cells. Here, we shed light on the mechanism by which these phytochemicals can attack human cancer cells. Mitotic arrest was coincident to the induction of centrosome amplification and declustering, causing multi-polar spindle formation. Corynoline was demonstrated to have true centrosome declustering activity in a model where A549 cells were chemically induced to have more than a regular complement of centrosomes. Corynoline could inhibit the centrosome clustering required for pseudo-bipolar spindle formation in these cells. The activity of AURKB, but not AURKA or polo-like kinase 4, was diminished by corynoline. It only partially inhibited AURKB, so it may be a partial antagonist or corynoline may work upstream on an unknown regulator of AURKB activity or localization. Nonetheless, corynoline and acetylcorynoline inhibited the viability of a variety of human cancer derived cell lines. These phytochemicals could serve as prototypes for a next-generation analog with improved potency, selectivity or in vivo bioavailability. Such an analog could be useful as a non-toxic component of combination therapies where inhibiting the chromosomal passenger protein complex is desired. [Display omitted] • Corynoline, a benzophenanthridine alkaloid phytochemical, disrupts cell division. • Mitotic arrest, apoptosis and polyploidy are coincident with centrosome defects. • Corynoline definitively induces centrosome declustering in cancer cells. • AURKB activity, but not AURKA, is diminished by corynoline treatment. [ABSTRACT FROM AUTHOR]