Perez, Y. | bioRxiv Science

bioRxiv2018

Characterisation of palytoxin from an undescribed Palythoa (Anthozoa: Zoantharia: Sphenopidae) with significant in vitro cytotoxic effects on cancer cells at picomolar doses

Palytoxin (PlTX), a large polyhydroxylated compound, is among the most potent non-peptide toxin in marine organisms known so far. The literature emphasizes the sodium/potassium pump (NaK) as the privileged target for PlTX when exerting its toxic effects. In this study, we focused on an undescribed species (Palythoa sp. Pc001), a coral species belonging to the genus Palythoa routinely cultivated in aquariums. We demonstrated that this species contains one of the highest yields of pure PlTX production ever found, 2.22 {+/-} 0.41 mg PlTX per gram of wet Palythoa. Using molecular data combined with external morphology, we identified Palythoa sp. Pc001 as the sister species to Palythoa aff. clavata. Further, the clade of a symbiotic Symbiodinium sp. was characterised by DNA barcoding and pigment content. Molecular data showed that Palythoa sp. Pc001 contains generalist Symbiodinium belonging to clade C. This paper also describes for the first time the localisation of PlTX and Symbiodinium cells in tissues of a highly toxic Palythoa species. PlTX toxicity was assayed on 72 h-cultured murine and human cancer cells versus the normal human dermal fibroblast (NHDF; PC C12300) cell line. Using MTT colorimetric assay and quantitative videomicroscopy, our results showed much higher in vitro cytotoxic activity on cancer cells (IC50 0.54 {+/-} 0.05 x 10-12 M) than on non-cancerous ones (IC50 > 1 x 10-6 M). Such a strong differential effect has never been reported with respect to the most potent NaK ligands (cardiac glycosides) described so far. Moreover, PlTX displayed similar in vitro growth inhibitory activity in rodent and human cancer cells, although the NaK in rodents displays a double mutation in the 1-subunit that usually decreases the sensitivity to others cardiac glycosides like ouabain, when compared to human cells. This work demonstrates, first, that picomolar concentrations of PlTX have significant higher cytotoxic effects on cancer cells than on non-cancerous ones, and secondly, that this in vitro antitumor effect would not be entirely relied onto its canonical targeting to the NaK -subunit. Thus, PlTX ranks amongst highly potent anti-cancer drugs as it targets cancers while potentially minimizing the drugs side effects on healthy cells.

cancer biology↗

bioRxiv2017

A Complete Logical Approach to Resolve the Evolution and Dynamics of Mitochondrial Genome in Bilaterians

A new method of genomic maps analysis based on formal logic is described. The purpose of the method is to 1) use mitochondrial genomic organisation of current taxa as datasets 2) calculate mutational steps between all mitochondrial gene arrangements and 3) reconstruct phylogenetic relationships according to these calculated mutational steps within a dendrogram under the assumption of maximum parsimony. Unlike existing methods mainly based on the probabilistic approach, the main strength of this new approach is that it calculates all the exact tree solutions with completeness and provides logical consequences as very robust results. Moreover, the method infers all possible hypothetical ancestors and reconstructs character states for all internal nodes (ancestors) of the trees. We started by testing the method using the deuterostomes as a study case. Then, with sponges as an outgroup, we investigated the mutational network of mitochondrial genomes of 47 bilaterian phyla and emphasised the peculiar case of chaetognaths. This pilot work showed that the use of formal logic in a hypothetico-deductive background such as phylogeny (where experimental testing of hypotheses is impossible) is very promising to explore mitochondrial gene rearrangements in deuterostomes and should be applied to many other bilaterian clades.\n\nAuthor SummaryInvestigating how recombination might modify gene arrangements during the evolution of metazoans has become a routine part of mitochondrial genome analysis. In this paper, we present a new approach based on formal logic that provides optimal solutions in the genome rearrangement field. In particular, we improve the sorting by including all rearrangement events, e.g., transposition, inversion and reverse transposition. The problem we face with is to find the most parsimonious tree(s) explaining all the rearrangement events from a common ancestor to all the descendants of a given clade (hereinafter PHYLO problem). So far, a complete approach to find all the correct solutions of PHYLO is not available. Formal logic provides an elegant way to represent and solve such an NP-hard problem. It has the benefit of correctness, completeness and allows the understanding of the logical consequences (results true for all solutions found). First, one must define PHYLO (axiomatisation) with a set of logic formulas or constraints. Second, a model generator calculates all the models, each model being a solution of PHYLO. Several complete model generators are available but a recurring difficulty is the computation time when the data set increases. When the search of a solution takes exponential time, two computing strategies are conceivable: an incomplete but fast algorithm that does not provide the optimal solution (for example, use local improvements from an initial random solution) or a complete - and thus not efficient - algorithm on a smaller tractable dataset. While the large amount of genes found in the nuclear genome strongly limits our possibility to use of formal logic with any conventional computer, we show in our paper that, for bilaterian mtDNAs, all the correct solutions can be found in a reasonable time due to the small number of genes.

bioinformatics↗