EFFECT OF A BOTULINUM NEUROTOXIN FROM A NATIVE STRAIN OF C. botulinum ON BREAST CANCER CELLS

CHAPANA A; GUARNIOLO D; SOSA ESTEBAN; RA FERNANDEZ; SOSA MA; CARVELLI L; PATRICIA CABALLERO

Congreso; XXXIX Reunión Anual de la Sociedad de Biología de Cuyo; 2021

Botulism is a neuroparalytic disease caused by botulinum neurotoxins (BoNT, serotypes A-G) produced by Clostridiumbotulinum. BoNT A is currently widely used in the treatment of neuromuscular transmission disorders. Genomic andphenotypic studies showed that native strains from Cuyo region (Argentina) and their BoNTs correspond to subtype A2, andwould have higher activity than A1 (Botox®), being a potential therapeutic agent. The native BoNTSu 1935 obtained fromsoil is known to degrade actin from rat brain homogenates, suggesting that this protein would be a target for this toxin. Inthis study, the action of BoNTSu 1935 on the actin and tubulin cytoskeleton was evaluated in mammary tumor cells. Both,the BoNTSu 1935 and the BoNT from the A Hall strain (subtype A1) were purified by 60% saline precipitation. MCF7 andMDA-MB-231 cells were treated with 250 LD50 of the BoNTs for 5, 10, 25, 45 and 90 min. The cells were then processedfor immunoblot or immunofluorescence in order to evaluate the expression and distribution of actin and tubulin. In addition,the integrity of the Golgi complex was evaluated. In MCF-7 cells, BoNTSu 1935 induced actin degradation at higher extentthan BoNT A Hall. In turn, this protein was redistributed to plasma membrane location, in a time-dependent manner.Although tubulin was affected in a similar way, this protein was redistributed to perinuclear patches. Meanwhile, the Golgicomplex appears disorganized after treatment with the toxin. Interestingly, no changes were observed in either thedistribution, or in the expression of actin and tubulin in MDA-MB-231 cells. Regarding the cytotoxicity of BoNTSu 1935,we observed ~90% mortality of MCF-7 cells at 90 min of incubation with the toxin, while that index was reached in theMDA-MB-231 cells, as early as 25 min incubation. In contrast, BoNT A Hall only induced 50% cytotoxicity in MDA-MB-231 cells at 90 min incubation. These results would indicate a higher cytotoxicity of BoNTSu 1935, whose action mechanismswould be selective for tumor cell types. This could be related to levels of malignancy of the tumor cells.