## 4 Discussion
However, when NPs generated sufficient intracellular ROS, cells stopped carrying out their typical functions, ultimately leading to cell death [35]. The findings of this study revealed significant inductions of oxidative stress markers, such as ROS, 8-OHDG, LPO, and NO, accompanied by a drop in the antioxidant markers (CAT, SOD, and GPx activities and GSH levels) in MCF-7 cells exposed to SeNPs-CV in contrast to the control cells. These observations indicated that SeNPs-CV increasedoxidative stress in MCF-7 cells. However, at a dose of 16 \(\mathrm{\SIUnitSymbolMicro m}\)/mL (half the IC50), CV alone had little effect on the oxidant/antioxidant system and only affected LPO levels, whereas conjugation with SeNPs boosted its oxidative effect. GSH contents might indicate a cell's antioxidant capability, as GSH protects enzyme thiol groups and interacts with free radicals. Here, the depletion of GSH contents after SeNPs-CV administration reflects the cytotoxicity of synthesized SeNPs-CV. These findings were in line with [PERSON] et al. [36], who concluded that CV induced notable ROS production, as indicated by an increase in LPO and 8-OHdG in tumor cells. Similarly, it was found that CV acts as a prooxidant and promotes cytotoxicity in human epithelial colorectal cancer [37]. On the other hand, the therapeutic use of SeNPs has drawn the most attention in cancer therapy because tumor cells are more susceptible to oxidative stress triggered by elevated Se levels than normal cells. Moreover, SeNPs may cause ROS-mediated cell death when they aggregate in cancerous cells, while providing anti-oxidation and cancer prevention in healthy tissues at low quantities [38]. Oxidative stress and inflammation can initiate the apoptotic signaling pathway as a result of mitochondrial dysfunction. When the integrity of the mitochondrial membrane is disrupted, cytochrome c moves from the mitochondria to the cytosol. This starts the caspase signaling cascade, which damages the DNA [15]. In addition, ROS controls the translocation, phosphorylation, and cleavage of the pro-apoptotic Bcl-2 protein, which induces apoptosis [1]. In the current study, increases in apoptotic markers (caspase-3, Bax, and cytochrome c) and reductions in the anti-apoptotic protein Bcl-2 were seen in MCF-7 cells treated with SeNPs-CV. These changes in apoptotic markers were in line with a rise in the number of cells that started early or late apoptosis after being exposed to SeNPs-CV, as shown in Figure 3. These results were in harmony with former studies [36,39], which stated that CV's anti-proliferative effects on metastatic BC cells were based on the typical apoptotic response, which includes a drop in mitochondrial membrane potential and a rise in cytochrome c discharge from mitochondria, a decline in the Bcl-2/Bax ratio, an elevation in caspase activity, PARP cleavage, and DNA fragmentation. In the same context, CV has also been observed to cause mitochondrial apoptosis in human oral squamous cell cancer [40], leukemia and lymphoma cells [13], and colon cancer cells [28] by disrupting matrix metalloproteinases (MMPs) and altering the expression rates of Bax/Bcl2 proteins. Our findings demonstrated that SeNPs-CV were more efficient in inducing apoptotic markers compared with CV alone, indicating the synergistic effect of SeNPs. Formerly, Se has been shown to stimulate apoptosis in cancerous cells through ROS production, activation of several caspases, and the formation of apoptotic bodies [41]. Furthermore, [PERSON] et al. [42] stated that SeNPs increase the expression of Bax and cytochrome c in MCF-7 cells. IL-1\(\beta\) has been shown in several studies to have a substantial pro-apoptotic impact in human cells by boosting the expression ratio of Bax/Bcl-2, releasing cytochrome c from the mitochondria, and stimulating caspase-9 and caspase-3 to accomplish the apoptotic process. Subsequently, mitochondrial damage was detected following IL-1\(\beta\) stimulation [43].