Avaliação da atividade antitumoral in vitro de Solanum jabrense Agra & M. Nee

Abstract

Cancer is characterized by genetic alterations that lead to uncontrolled cell growth, immune system evasion, and tissue invasion, making it the second leading cause of global mortality. Among cancer types, breast cancer stands out as the most prevalent, accounting for approximately 11.7% of new cases diagnosed annually. Solanum jabrense, an endemic plant of Brazil, is rich in bioactive metabolites, particularly alkaloids with antitumor activity. This study aimed to evaluate the in vitro antitumor activity of Solanum jabrense. For the analysis, two extracts derived from this plant were used: the hydroalcoholic extract (ESJ) and its alkaloid fraction (FSJ). Initially, the ESJ was tested for cytotoxicity using the MTT assay in tumor cell lines (MCF-7, MDA-MB-231, PC-3, SK-MEL-28), showing higher cytotoxicity in breast adenocarcinoma cell lines. Consequently, these cell lines were selected for subsequent evaluations and determination of IC50 and selectivity index over 24, 48, and 72-hour treatment periods. It was observed that the MCF-7 cell line exhibited the highest selectivity for ESJ at 48 hours, with a mean inhibitory concentration (IC50) of 27.72 ± 0.02 μg/mL, compared to 78.56 ± 0.08 μg/mL in HEK293 cells. Thus, the MCF-7 cell line and the 48-hour treatment period were selected to investigate the antitumor effects of the alkaloid fraction of the extract (FSJ). FSJ was found to be more selective for MCF-7 compared to other non-tumoral cell lines. Regarding HEK-293, it was approximately 15 times more selective and about five times more selective compared to MCF-10A. Moreover, it exhibited greater selectivity than the standard drug doxorubicin.Subsequently, the antitumor mechanisms of action were evaluated in the MCF-7 cell line. Cell cycle analysis revealed a significant increase in the sub-G1 fraction after 48 hours of treatment with FSJ. Annexin V FITC/PI staining indicated an increase in the percentage of apoptotic cells, which was corroborated by observations of apoptotic morphological characteristics under laser confocal microscopy. Mitochondrial alterations studied using the JC-1 marker revealed a reduction in mitochondrial membrane potential, indicating the activation of the intrinsic apoptosis pathway. Furthermore, the evaluation of cytotoxicity in a 3D spheroid culture model revealed that FSJ was effective in reducing spheroid size and exhibited antimigratory effects. The cytotoxicity of the extract's major compound, solamargine, was evaluated at 48 hours, with an IC50 of 8.65 ± 0.04 μM. Additionally, FSJ cytotoxicity was prevented by pre-treatment with N-acetyl-L-cysteine (NAC), suggesting the involvement of oxidative stress. Molecular docking analysis showed that solamargine interacted with the active sites of ERK2, JNK1, p38α MAPK, and IKKβ proteins. In summary, FSJ demonstrates in vitro antitumor effects by inducing apoptosis, oxidative stress, and inhibiting p38 MAPK, ERK2, JNK1, and IKKβ proteins.