BthTX-I from Bothrops jararacussu induces apoptosis in human breast cancer cell lines and decreases cancer stem cell subpopulation

 

Patrícia Heloise Alves Bezerra¹, Isadora Marques Ferreira¹, Beatriz Tinoco Franceschi¹, Francine Bianchini¹, Luciana Ambrósio², Adélia Cristina O. Cintra³, Suely Vilela Sampaio³, Fabíola Attié de Castro², Maria Regina Torqueti¹

 

1 Laboratory of Clinical Cytology, Department of Clinical Analyses, Toxicology and Food Science, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo (USP), Ribeirão Preto, SP, Brazil.

2 Laboratory of Hematology, Department of Clinical Analyses, Toxicology and Food Science, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo (USP), Ribeirão Preto, SP, Brazil.

3 Laboratory of Toxinology, Department of Clinical Analyses, Toxicology and Food Science, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo (USP), Ribeirão Preto, SP, Brazil.

 

ABSTRACT

Background:

Breast cancer is the neoplasm with both the highest incidence and mortality rate among women worldwide. Given the known snake venom cytotoxicity towards several tumor types, we evaluated the effects of BthTX-I from Bothrops jararacussu on MCF7, SKBR3, and MDAMB231 breast cancer cell lines.

 

Methods:

BthTX-I cytotoxicity was determined via MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide assay. Cell death was measured by a hypotonic fluorescent solution method, annexin-V-FITC/propidium iodide staining and by apoptotic/autophagic protein expression. Cancer stem cells (CSCs) were quantified by flow cytometry using anti-CD24-FITC and anti-CD44-APC antibodies and propidium iodide.

 

Results:

BthTX-I at 102 µg/mL induced cell death in all cell lines. The toxin induced apoptosis in MCF7, SKBR3, and MDAMB231 in a dose-dependent manner, as confirmed by the increasing number of hypodiploid nuclei. Expression of pro-caspase 3, pro-caspase 8 and Beclin-1 proteins were increased, while the level of the antiapoptotic protein Bcl-2 was diminished in MCF7 cells. BthTX-I changed the staining pattern of CSCs in MDAMB231 cells by increasing expression of CD24 receptors, which mediated cell death.

 

Conclusions:

BthTX-I induces apoptosis and autophagy in all breast cancer cell lines tested and also reduces CSCs subpopulation, which makes it a promising therapeutic alternative for breast cancer.

 

Keywords apoptosis; bothropstoxin; breast cancer; cancer stem cells

 

Received: February 22, 2019.

Accepted: June 04, 2019.

 

Correspondence to: torqueti@fcfrp.usp.br.

 

^{Competing interests}

The authors declare that they have no competing interests.

 

^{Authors’ contributions}

PHAB, FB, and MRT conceived and designed the experiments. SVS provided the toxin that was purified in the Laboratory of Toxinology. PHAB, IMF, BTF, and FB carried out the experiments. PHAB, LA, and FAC analyzed and interpreted data and statistics. SVS and ACOC analyzed purification data and drafted the manuscript. PHAB, FAC and MRT interpreted the results and drafted the manuscript. All authors read and approved the final manuscript.