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Integrins are plasma membrane proteins, whose dysfunction frequently results in cancer pathology, and therefore they represent important targets of anti-tumour therapy. Snake venoms are a rich source of disintegrins (Dis), proteins that specifically bind integrins and thus interfere with their functions. In an attempt to discover new molecules for treatment of breast cancer, the major type of cancer in women, we isolated a dimeric Dis (Vaa-Dis) from the venom of the nosehorned viper. By cell viability testing we demonstrated that 50 nM and higher concentrations of Vaa-Dis were toxic to highly invasive human breast adenocarcinoma cell line MDA-MB-231. Wound-healing assay revealed that already at one order of magnitude lower concentrations Vaa-Dis efficiently inhibited MDA-MB-231 cell migration. This exposed a promising anti-metastatic potential of Vaa-Dis and a good perspective of these natural snake venom proteins for further research and development towards the application in breast cancer treatment.

Cytosolic lipid droplets (LDs) store excess fatty acids (FAs) in the form of neutral lipids and prevent starvation-induced cancer cell death. Here we studied the ability of mono- and polyunsaturated FAs to affect LD formation and survival in HeLa cervical cancer cells. We found that the LD content in HeLa cells increases with cell density, but it decreases in MDA-MB-231 breast cancer cells. Exogenously-added unsaturated FAs, including oleic (OA), linoleic (LA), arachidonic (AA), eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) displayed a similar ability to alter LD formation in HeLa cells. There was a dual, concentration-dependent effect on neutral lipid accumulation: low micromolar concentrations of LA, AA and DHA reduced, while all FAs induced LD formation at higher concentrations. In serum starved He-La cells, OA stimulated LD formation, but, contrary to expectations, it promoted cell death. Our results reveal a link between cell population density and LD formation in HeLa cells and show that unsaturated FAs may both suppress or stimulate LD formation. This dynamic regulation of LD content must be accounted for when studying the effects of lipids and lipid metabolism-targeting drugs on LD metabolism in HeLa cells.

Ammodytoxins (Atxs) and ammodytins (Atns) are group IIA phospholipases A2 (sPLA2s) and their homologues, secreted by venom glands of the nose-horned viper (Vipera a. ammodytes). The molecular mechanisms underlying their various pharmacological effects, including neurotoxicity, myotoxicity and anticoagulant activity, are still not completely understood. The structure-function relationships of Atxs and Atns have been studied by site-directed and cassette mutagenesis. We cloned their complementary DNA reversely transcribed from the mRNA isolated from the venom glands, and expressed the mature protein regions in Escherichia coli. The recombinant proteins were isolated in their inactive forms and renatured in vitro to the properly folded and biologically active forms. More than fifty site-directed mutants and chimeric sPLA2 proteins of Atxs and Atns were produced and their properties analysed. In the course of these studies, the three-dimensional crystal structure was determined of the most neurotoxic venom sPLA2, AtxA, that induces complete failure of vertebrate neuromuscular transmission, using the recombinant protein. The results have contributed significantly to a better understanding of the molecular mechanism of presynaptic toxicity of sPLA2 neurotoxins. In addition, the activity of enzymatically inactive sPLA2 homologues and their evolution are now better understood.