Potencial antitumoral de Annona vepretorum Mart. (Annonaceae) em células de câncer colorretal

Abstract

Colorectal cancer (CRC) is the third most diagnosed cancer worldwide and the second most lethal. In addition, current therapy faces significant challenges, including low selectivity, toxicity, adverse effects, and drug resistance, justifying the search for new drugs. In this context, natural products provide a rich source of bioactive compounds with anticancer properties. The plant Annona vepretorum Mart., known as "pinha da Caatinga," is an endemic species of the Brazilian Northeast. Its plant derivatives have cytotoxic effects described in the literature but not yet elucidated. Given this, the objective of this study was to evaluate the in vitro antitumor activity of the petroleum ether extract obtained from the stem bark of Annona vepretorum (EEP-Av). Cytotoxicity was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay against human tumor cell lines (HCT 116, HT-29, SK-MEL-28, MCF-7, and LoVo) and a non-tumor human cell line from a healthy individual (HaCaT). After 72 h of treatment, the HCT 116 colorectal adenocarcinoma cell line was the most sensitive to EEP-Av (IC₅₀: 15.49 ± 2.28 μg/mL), with no significant difference compared to the IC₅₀ at 48 h (14.66 ± 3.49 μg/mL), and was selected for further experiments. Additionally, the extract was more selective for these tumor cells at 48 h (Selectivity Index – SI: 5.84) than at 72 h (SI: 5.0), relative to its activity in HaCaT cells (IC₅₀ 72 h: 77.55 ± 2.50 μg/mL / IC₅₀ 48 h: 85.62 ± 2.42 μg/mL). In comparison, after 48 h, the positive control doxorubicin (DXR) was more cytotoxic to HaCaT cells (IC₅₀: 0.64 ± 0.98 μM) than to HCT 116 cells (IC₅₀: 4.30 ± 0.99 μM), with an SI of 0.14. Therefore, EEP-Av was 41.71 times more selective than DXR. Cell death type analysis (apoptosis/necrosis) using acridine orange/propidium iodide (AO/PI) staining showed that EEP-Av induced apoptosis in HCT 116 cells, displaying characteristics such as membrane blebbing and nuclear alterations, confirmed by Hoechst 34580 staining. In the mitochondrial alteration investigation using JC-1, the extract caused a loss of mitochondrial membrane potential, suggesting the involvement of the intrinsic apoptosis pathway in its mechanism. Furthermore, in the redox state modulation study, EEP-Av increased ROS levels, which were partially reversed by pretreatment with N-acetylcysteine (NAC). Therefore, this study suggests that EEP-Av selectively induces cell death in human colorectal adenocarcinoma cells (HCT 116) through modulation of the intrinsic apoptosis pathway and oxidative stress induction.