Antiproliferative and cytotoxic effect of abietane diterpenes in urothelial carcinoma cell line

Abstract

Introdução: No âmbito da oncologia urológica, o cancro da bexiga (BC) destaca-se como a forma mais comum de cancro urotelial e está entre as neoplasias urológicas mais agressivas. Caracteristicamente, 75-80% dos casos de BC são não-músculo-invasivos (NMIBC), com alta taxa de recorrência e risco significativo de evoluir para cancro da bexiga músculo-invasivo (MIBC). O tratamento adjuvante predominante, a administração intravesical de Bacillus Calmette-Guerin (BCG), visa prevenir esta progressão. No entanto, a sua eficácia de tratamento é limitada, com 30 a 50% dos doentes a apresentarem resistência e um risco elevado de progressão para MIBC. Esta insuficiência terapêutica sublinha a necessidade urgente de novas intervenções farmacológicas. Os diterpenos, particularmente os derivados do género Plectranthus L'Hér., emergiram como uma classe promissora de metabolitos secundários biologicamente ativos. Este estudo explora as capacidades citotóxicas dos diterpenos de núcleo abietano naturais Roy, DiRoy e ParvD, contra células tumorais uroteliais. Material e métodos: Os compostos (Roy, DiRoy e ParvD) foram isolados de plantas sul-africanas pertencentes à família Lamiaceae: os compostos Roy e DiRoy foram isolados do extrato acetónico de folhas e caules de Plectranthus hadiensis Schweinf, e o composto ParvD foi isolado do extrato acetónico de Plectranthus ecklonii Benth. O perfil citotóxico/antiproliferativo desses diterpenos foi estudado na linha celular 639-V. Resultados e discussão: Os diterpenos Roy e ParvD induziram um efeito citotóxico/antiproliferativo significativo, ao contrário do DiRoy. O diterpeno Roy evidenciou um aumento da apoptose celular precoce, interferindo também na proliferação celular, ao induzir paragem do ciclo celular na fase S/G2/M. Conclusão: Os diterpenos Roy e ParvD exercem uma ação citotóxica/antiproliferativa robusta contra as células tumorais avaliadas e, devido à paragem do ciclo celular em S/G2/M, o composto Roy parece promissor para ser submetido a uma avaliação futura, com o intuito de se entender melhor o seu efeito a nível celular.

Introduction: In the realm of urological oncology, Bladder Cancer (BC) stands out as the most common form of urothelial cancer and ranks among the most aggressive urological malignancies. Characteristically, 75%-80% of BC cases are non-muscle-invasive (NMIBC), marked by high recurrence rates and significant risk of developing into muscle invasive bladder cancer (MIBC). The prevailing adjuvant treatment, intravesical Bacillus Calmette–Guerin (BCG) administration, aims to prevent this progression. However, the efficacy of BCG therapy is limited, with 30 to 50% of patients exhibiting resistance and an elevated risk of progression to MIBC. This therapeutic shortfall underscores the urgent need for novel pharmacological interventions. Diterpenes, particularly those derived from the genus Plectranthus L´Hér., have emerged as a promising class of biologically active secondary metabolites. This study is dedicated to exploring the cytotoxic capabilities of the naturally occurring abietane diterpenoids: 7α-Acetoxy-6β-hydroxyroyleanone (Roy), 7β,6β-dihydroxyroyleanone (DiRoy), and Parvifloron D (ParvD) against urothelial cancer cells. Material and methods: The compounds (Roy, DiRoy and ParvD) were isolated from South African plants belonging to the Lamiaceae family: Roy and DiRoy were isolated from the acetonic extract of leaves and stems of Plectranthus hadiensis Schweinf, and ParvD was isolated from the acetonic extract of Plectranthus ecklonii Benth. The cytotoxic/antiproliferative profile of these diterpenes in 639-V cell line was investigated. Cell viability was evaluated by Alamar blue® assay, while cell death and cell cycle’s impact were assessed by flow cytometry. The half-inhibitory concentration (IC50) was determined using GraphPad Prism. Results and discussion: The diterpenes Roy and ParvD induced a significant cytotoxic/antiproliferative effect, contrarily to DiRoy. Roy also showed an increase in early cell apoptosis and also interfered with cell proliferation, inducing cell cycle arrest in the S/G2/M phase. Conclusion: Roy and ParvD exert a robust cytotoxic and antiproliferative action against the cancer cells evaluated. As Roy induced cell cycle arrest in the S/G2/M phase, it is worth of future evaluation in order to understand its mechanist effect in the cells.