Dados do Resumo

Título

Dual Role of Betulinic Acid in Autophagy: Unveiling its Impact on Lysosome Functionality and Cancer Cell Lines

Introdução

Autophagy, a multifaceted process critical to cancer progression, relies on the pivotal role of lysosome functionality to maintain cellular homeostasis. Betulinic Acid (BA), a natural compound bearing molecular similarity to cholesterol, has stimulated our interest due to its unique and profound impact on mitochondria and lysosome functionality in human nonmalignant cells. BA's distinctive properties enable it to serve a dual role in autophagy, functioning as an activator and inhibitor. This dual action positions BA as a promising candidate for developing targeted cancer therapies, especially those that evade chemotherapies due to the activation of cytoprotective autophagy, offering a ray of hope for the future of cancer therapy.

Objetivo

This study explores BA's dual role in autophagy as an activator and inhibitor in human cancer cells. It aims to uncover new insights that could potentially revolutionize cancer treatment strategies and inspire innovation in cancer research.

Métodos

This study employs cutting-edge biotechnological tools, such as ATG7 silencing and a lysosome-mimetic model containing Bis(monoacylglycerol)phosphate (BMP): Dipalmitoylphosphatidylcholine (DPPC): Cholesterol, to conduct molecular and cellular studies. BMP is a unique lipid predominantly found in late endosomes and lysosomes. This model was used to investigate the impact of BA on lysosome functionality. Other innovative methods, combined with a variety of cell lines and cell culture techniques, were conducted, including cytotoxicity studies, quantification of lysosome content, immunostaining, cell clonogenic assays, and flow cytometry, which hold the potential to unveil groundbreaking findings in the field of cancer research.

Resultados

Unlike OA, BA compromises the cell viability of A549, HeLa, HT29, MES-SA, PC3, SKMEL-25 and SKMEL-28. However, OA behaves as BA upon chemical lysosomal inhibition, leading to lysosomal accumulation associated with lower cell viability. BA, not OA, promotes a lysosomal-mitochondrial axis stress linked to autophagy impairment, which remarkably affects A549 – a chemo-multi-resistant lung carcinoma cell. Silencing ATG7 increases the A549´s sensitivity to OA treatment, decreasing cell proliferation by 70%. Conversely, regardless of the ATG7 expression, BA compromises autophagy, characterized by the simultaneous accumulation of lysosomes and mitochondria. The study also provides new insights into how BA affects the activity of lysosomal enzymes, affecting cholesterol metabolism. According to the biophysical membrane study, BA has a more pronounced effect on the lysosome-mimetic model than OA, potentially disrupting its structure and integrity.

Conclusões

Triterpenoids affect autophagy in a cell-specific way in different cancer cell lines. BA inhibits lysosomal function without altering acidic pH, indicating that its effects are linked to alterations in the lipid domains of the lysosomal membrane, unlike OA. The results show that BA affects the integrity and function of this membrane, and despite in vitro limitations, it suggests potential for future research in personalized cancer treatments.

Financiador do resumo

PNPD (Programa Nacional de Pós Doutorado)/CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior)/FINEP (Financiadora de Estudos e Projetos) grant number 02533/09-0
FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo) grants 2012/50680-5, 2013/07937-8 and 2016/07642-6.

Palavras Chave

Keywords: Membrane damage; lysosomes; Autophagy