Bioactive Materials | Selenium nanoparticles induce apoptosis in triple-negative breast cancer cells via the MAPKs/Bcl2 pathway

This study developed selenium nanoparticles modified with mushroom polysaccharide-protein complexes and revealed that they trigger mitochondrial-dependent apoptosis through the MAPKs/Bcl2 pathway, while targeting MUC1 significantly enhances antitumor efficacy, demonstrating excellent in vivo therapeutic effects and safety.

 

Literature Overview

The article “Translational selenium nanoparticles trigger apoptosis in triple-negative breast cancer cells through the MAPKs/Bcl2 pathway”, published in the journal Bioactive Materials, reviews and summarizes the antitumor mechanisms, metabolic behavior, and in vivo efficacy of novel polysaccharide-protein complex-modified selenium nanoparticles (PTR-SeNPs) and their MUC1-targeted forms in triple-negative breast cancer. The study systematically evaluates their ability to inhibit proliferation across multiple TNBC cell lines, elucidates the molecular mechanism involving ROS induction and MAPKs/Bcl2 signaling in regulating the mitochondrial apoptosis pathway, and combines MUC1 antibodies to achieve enhanced targeting effects, ultimately validating significant tumor suppression with no obvious toxicity in animal models. The entire paragraph is coherent and logical, ending with a Chinese period.

Background Knowledge

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer that lacks expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), accounting for approximately 12%–20% of all breast cancer cases. Due to the absence of clear therapeutic targets, TNBC patients typically rely on chemotherapy, but are prone to recurrence, metastasis, and drug resistance, resulting in poor prognosis. Therefore, developing novel targeted strategies has become a current research hotspot. MUC1 is a transmembrane glycoprotein expressed on the surface of various epithelial cells, serving protective and lubricative functions in normal cells, but is abnormally overexpressed with disrupted glycosylation modifications in various tumors including TNBC, exposing tumor-specific antigenic epitopes, making it an ideal therapeutic target. Nanodrug delivery systems have attracted widespread attention due to their ability to improve drug solubility, prolong circulation time, enhance tumor accumulation, and enable targeted delivery. Selenium, an essential trace element in the human body, participates in various physiological processes, and its derivatives exhibit potential anticancer activity. Selenium nanoparticles (SeNPs) demonstrate stronger antitumor activity and lower toxicity compared to traditional selenium compounds. However, most SeNPs lack targeting ability, and their in vivo metabolic pathways, mechanisms of action, and long-term toxicity remain unclear. This study constructs stable, low-toxicity SeNPs based on a natural mushroom-derived polysaccharide-protein complex (PSP) and further conjugates them with anti-MUC1 antibodies to enhance targeting, aiming to overcome the limitations of existing SeNPs in TNBC therapy and provide theoretical and experimental support for developing novel targeted nanomedicines.

 

 

Research Methods and Experiments

Researchers first synthesized PTR-SeNPs using a polysaccharide-protein complex (PSP) derived from Pleurotus tuber-regium via a reduction reaction, and characterized their morphology, particle size, surface charge, and chemical structure using TEM, DLS, HRTEM-EDX, and FT-IR. Subsequently, PTR-SeNPs were conjugated with the Fab fragment of an anti-MUC1-C antibody (7B8) to construct the targeted nanoparticle MUC1@PTR-SeNPs, and their binding efficiency and physical properties were validated. In vitro, the MTS assay was used to evaluate the proliferative inhibition of both nanoparticles on 17 TNBC cell lines, determining IC50 values and analyzing the correlation between MUC1 expression levels and sensitivity. Flow cytometry was used to analyze cell cycle distribution (sub-G1 peak), Annexin V-FITC/PI staining to detect phosphatidylserine externalization, TUNEL assay to detect DNA fragmentation, and DAPI staining to observe nuclear condensation, confirming apoptosis. Furthermore, Western blotting was used to analyze expression changes in apoptosis-related proteins such as Bcl-2 family members (Bcl-2, Bcl-xL, Bax, Bad), caspase-9, and PARP, as well as the phosphorylation status of the AKT and MAPKs (p38, JNK, ERK) pathways, with specific inhibitors (SB203580 and U0126) used to validate pathway functionality. JC-1 staining was used to detect changes in mitochondrial membrane potential (ΔΨm) to assess mitochondrial dysfunction. Confocal microscopy was used to track the colocalization of Coumarin-6-labeled nanoparticles with lysosomes to study cellular uptake mechanisms. In the in vivo metabolism study, a ⁷⁸Se isotope-labeled rat model was used, combined with HPLC-ICP-MS to analyze the types and distribution of selenium metabolites in serum, urine, and major organs. In animal experiments, an MDA-MB-468 xenograft nude mouse model was established, and different doses of PTR-SeNPs and MUC1@PTR-SeNPs were administered orally for 30 consecutive days to monitor tumor volume and body weight changes. After the experiment, tumor tissues were collected for H&E staining, IHC detection of Ki-67 expression, TUNEL staining to assess apoptosis, and Western blot analysis of caspase-9 and PARP cleavage. Serum biochemical indicators were also measured to evaluate systemic toxicity.

Key Conclusions and Perspectives

• PTR-SeNPs are spherical, with an average diameter of approximately 80 nm, negatively charged, and exhibit good aqueous stability and biocompatibility
• PTR-SeNPs show significant antiproliferative activity in 17 TNBC cell lines, especially with IC50 values below 5 μM in HCC1937 and MDA-MB-436 cells, and low cytotoxicity toward normal cells
• MUC1@PTR-SeNPs significantly enhance antitumor activity in TNBC cell lines with high or moderate MUC1 expression, reducing IC50 values and increasing maximum growth inhibition rates
• PTR-SeNPs induce ROS accumulation, leading to mitochondrial membrane potential loss and activation of the mitochondrial-dependent apoptosis pathway
• Mechanistically, PTR-SeNPs inhibit ERK phosphorylation while promoting p38 phosphorylation, thereby regulating Bcl-2 family protein expression, reducing the Bcl-2/Bax and Bcl-xL/Bad ratios, and ultimately activating caspase-9 and PARP cleavage
• Cellular uptake experiments show that PTR-SeNPs primarily enter cells via endocytosis and localize in lysosomes
• In the ⁷⁸Se-labeled rat model, PTR-SeNPs are effectively absorbed, converted into selenoproteins such as SelP and GPx, and excreted primarily as SeGalNAc metabolites
• In the MDA-MB-468 xenograft model, MUC1@PTR-SeNPs significantly suppress tumor growth, outperforming unmodified particles, without causing obvious systemic toxicity
• In vivo experiments confirm that MUC1@PTR-SeNPs exert antitumor effects by activating the mitochondrial apoptosis pathway, evidenced by reduced Ki-67 expression, increased TUNEL-positive cells, and elevated caspase-9/PARP cleavage
• Serum biochemical analysis shows decreased LDH, ALT, and AST levels in the treatment group, indicating the drug not only effectively inhibits tumor progression but may also reduce tissue damage, without adverse effects on liver or kidney function

Research Significance and Prospects

This study successfully developed a targeted selenium nanoparticle based on a natural polysaccharide-protein complex, combining high antitumor efficacy with excellent biosafety. By conjugating an MUC1 antibody, selective killing of TNBC cells was achieved, improving the therapeutic index. The mechanistic study deeply revealed the signaling network through which PTR-SeNPs regulate mitochondrial apoptosis via the MAPKs/Bcl2 pathway, providing a new molecular explanation for the anticancer effects of selenium nanoparticles. Additionally, this work systematically elucidated the in vivo metabolic pathway of PTR-SeNPs, confirming their participation in selenoprotein synthesis and enhancing their potential as functional nutritional intervention agents. Moreover, the successful application of oral administration suggests good bioavailability and patient compliance, indicating strong clinical translational potential.

Future research could further expand the application of this platform, such as exploring its efficacy in other MUC1-overexpressing tumors (e.g., pancreatic cancer, lung cancer); conducting long-term toxicity and reproductive toxicity assessments to support clinical applications; optimizing formulations to improve drug loading and targeting efficiency; and exploring combination therapies with immune checkpoint inhibitors to investigate synergistic effects. Additionally, gene knockout animal models could be used to further validate the function of key signaling nodes, promoting the development of precision treatment strategies.

 

 

Conclusion

This study systematically evaluated the therapeutic potential of polysaccharide-protein complex-modified selenium nanoparticles (PTR-SeNPs) and their MUC1-targeted form (MUC1@PTR-SeNPs) in triple-negative breast cancer. It was found that PTR-SeNPs effectively inhibit the proliferation of various TNBC cells, a mechanism involving ROS-mediated mitochondrial membrane potential loss, followed by regulation of the MAPKs (ERK/p38) signaling pathway to affect the balance of Bcl-2 family proteins, ultimately activating caspase-dependent apoptosis. By conjugating an anti-MUC1 antibody, the targeting and cytotoxic efficacy of the nanoparticles toward MUC1-overexpressing TNBC cells were significantly enhanced. In vivo experiments confirmed that oral administration of MUC1@PTR-SeNPs significantly suppressed the growth of MDA-MB-468 xenograft tumors without causing significant hepatorenal toxicity or weight loss, demonstrating good safety. Metabolic tracking showed that the nanoparticles were absorbed by the body and participated in selenoprotein synthesis, with SeGalNAc as the primary metabolite. In summary, this work not only elucidates the molecular mechanisms of selenium nanoparticles’ antitumor effects but also demonstrates their translational potential as targeted therapeutic agents, providing a safe and effective new strategy for clinical intervention in triple-negative breast cancer.

 

Binhua Zou, Shuoshan Li, Kar-Him Luk, Ka-Hing Wong, and Tianfeng Chen. Translational selenium nanoparticles trigger apoptosis in triple-negative breast cancer cells through the MAPKs/Bcl2 pathway. Bioactive Materials.