Bisphenol A (BPA), chemically known as 4,4’-methanediyldiphenol, is a colorless solid widely used in the production of polycarbonates and epoxy resins found in numerous consumer products. As a prevalent endocrine-disrupting chemical, BPA exposure has been associated with an increased risk of various cancers1. Bladder cancer (BCa) is a common malignancy, with an estimated 613 791 new cases and 220,349 deaths worldwide in 20222. While environmental factors, including exposure to plastic derivatives like vinyl, are known contributors to BCa, the role of BPA as a bladder carcinogen remains uncertain3. To investigate this potential link, we utilized network toxicology and molecular docking techniques to identify key molecular targets and underlying mechanisms connecting BPA exposure to BCa. Initially, we assessed BPA’s toxicity using ADMETlab 2.0 and ProTox-II, which confirmed its carcinogenic properties. We then identified 94 genes that are common targets of both BPA and BCa (Fig. 1A). The protein–protein interaction (PPI) network of these genes is illustrated in Figure 1B, C. Through network analysis, we identified 25 core targets involved in BPA-induced BCa (Table 1, Fig. 1D; see Appendix A for methodological details). Among these, AKT1, BCL2, ESR2, MMP9, and PTGS2 emerged as the top five targets based on their significance in the PPI network, underscoring their critical roles in cancer development and cellular functions. Table 1 - Core targets screened from PPI network. Gene Degree Betweenness centrality Closeness centrality Eigenvector LAC Network AKT1 39 1060.997162 0.591836735 0.26525104 11.2307692 28.7885823 ESR1 36 880.170772 0.583892617 0.26434049 12.4444444 27.8872688 PTGS2 33 876.4837861 0.557692308 0.230445459 11.030303 24.2509261 HSP90AA1 33 546.3167651 0.533742331 0.245007366 11.7575758 26.1319652 BCL2 31 317.5996243 0.540372671 0.252055407 13.5483871 25.4981528 HSP90AB1 30 303.0279969 0.520958084 0.239703 12.6666667 24.7351115 PRKACA 27 676.0356055 0.533742331 0.192884043 8.44444444 13.4590872 MMP9 26 359.9084607 0.517857143 0.223275453 12.8461539 19.6690356 AR 22 171.1279091 0.5 0.198840737 12.3636364 17.1674614 BCL2L1 22 92.70471744 0.494318182 0.210421786 13.5454546 17.4777179 JAK2 21 45.68191741 0.478021978 0.201992869 13.2380952 17.2408039 BRAF 21 206.1615265 0.48603352 0.191004798 11.5238095 15.4324859 MMP2 20 49.16676913 0.48603352 0.193332523 12.4 15.0187761 ESR2 20 618.1129331 0.524096386 0.154238954 7.8 11.071182 DRD2 15 351.4768097 0.453125 0.05227172 4.93333333 8.31651682 PTGS1 15 305.0205023 0.467741935 0.090451367 5.06666667 8.17420635 SLC6A3 14 261.7310756 0.455497382 0.043532852 4.85714286 7.3992674 HDAC1 14 184.3304286 0.450777202 0.141600087 9.14285714 10.1794872 CYP19A1 14 211.8777463 0.47027027 0.113724843 6.71428571 9.12004662 FGFR1 13 92.68396041 0.457894737 0.127989799 8 8.97619048 MAPT 12 300.5772365 0.48603352 0.095532082 5 6.36493507 FASN 12 132.7585613 0.439393939 0.099564411 5.5 7.59848485 ALOX5 11 44.51446227 0.430693069 0.072972208 5.45454546 7.53928571 CTSK 10 241.7943608 0.446153846 0.084626049 5 5.8031746 EPHX2 9 47.7208429 0.432835821 0.062587686 4.22222222 5.05952381 LAC, local average connectivity. Subsequently, gene ontology (GO) analysis revealed that these target genes are primarily involved in processes such as protein phosphorylation, plasma membrane functions, and protein binding (Fig. 1E). Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis identified key signaling pathways associated with these genes, including cancer pathways, neuroactive ligand–receptor interactions, endocrine resistance, and chemical oncogenic receptor activation (Fig. 1F). These findings confirm the involvement of these genes in cancer-related processes and highlight their importance in disease development and progressionFigure 1.: The network analysis between BPA and bladder cancer targets. (A) Venn diagram for 94 genes intersects between BPA and bladder cancer targets. (B, C) Protein–protein interaction network of potential targets. (D) Protein–protein interaction of core targets. (E) GO enrichment analysis of potential targets. (F) KEGG enrichment analysis of potential targets. Histogram in (E) showing the gene counts for each enriched pathway. The bar length represents the gene count, and the color denotes the pathway category. Bubble plot (F) of the top 20 enriched KEGG pathways, ranked by FDR. Bubble size reflects gene count, whereas color saturation represents enrichment significance (−log10(FDR)). BPA, bisphenol A; FDR, false discovery rate; GO, gene ontology; KEGG, Kyoto Encyclopedia of Genes and Genomes.. To further elucidate the interaction between BPA and the identified core targets, we performed molecular docking using CB-DOCK. We examined the binding interactions between BPA and the five core target proteins (AKT1, BCL2, ESR2, MMP9, and PTGS2) (Fig. 2). All five proteins exhibited strong binding affinities for BPA, with Vina scores below −5.0, indicating a high likelihood of binding. This suggests that BPA binding to these core proteins may be pivotal in the molecular mechanisms by which BPA induces BCaFigure 2.: Molecular docking results of the lowest binding energy in each target protein with the BPA. (A) Structure of BPA, (B) BPA and AKT1, (C) BPA and BCL2, (D) BPA and ESR2, (E) BPA and MMP9, (F) BPA and PTSG2. BPA, bisphenol A.. Pathway enrichment analysis revealed several significant pathways, including chemical carcinogenesis–receptor activation and pathways in cancer. BCa is associated with exposure to chemical toxins, and BPA can accumulate in the urine within the bladder. Ève Pellerin et al demonstrated that BPA in urine damages normal urinary tract cells and promotes the growth of BCa cells. They also found that BPA affects surrounding tissues, such as bladder fibroblasts and cancer-associated fibroblasts, which may further support cancer progression4. Combined with the regulatory effects of KEGG pathways and key targets like BCL2 and AKT1 on bladder tumor cells, we infer that urinary BPA may possess tumorigenic properties that promote BCa development. Additionally, our analysis suggests a link between BPA-induced BCa toxicity and pathways related to endocrine resistance and neuroactive ligand–receptor interactions. Godoy G et al found that androgen and estrogen receptors (AR, ER) are involved in the initiation and progression of BCa5. Their work supports our findings that BPA may cause BCa through endocrine pathways and ESR2 expression. However, our study has certain limitations that should be acknowledged. We did not provide clinical samples and translational experiments demonstrating that BPA toxicity is specific to BCa. Moreover, due to potential biases in databases and the inherent constraints of predictive algorithms, the computational predictions may be uncertain, including the risk of false positives. Acknowledging these uncertainties and the lack of empirical validation helps readers understand the constraints of our study. Besides, long-term observation of exposure models simulating BPA levels is essential for a more accurate assessment of its chronic effects. Enhancing bioinformatics analysis through the integration of multiple databases and cross-validation techniques can help reduce biases and improve the reliability of predictions. Such comprehensive investigation is warranted, as controlling exposure to environmental pollutants like BPA may influence cancer incidence, thereby informing more effective prevention and management strategies for BCa. In conclusion, our study comprehensively evaluated the carcinogenic potential of BPA in BCa using network toxicology and molecular docking analyses. We identified 94 candidate genes associated with BPA-induced BCa and further refined these to 25 key targets, including AKT1, BCL2, and ESR2, which are likely pivotal in the development of BCa. Analysis of key enrichment pathways, such as cancer pathways, endocrine resistance, and chemical oncogenic receptor activation, suggests that BPA exposure may elevate cancer risk. These findings could inform the development of preventive and therapeutic strategies aimed at mitigating the harmful effects of BPA on the bladder. Future research should involve collaborative efforts among urologists, oncologists, environmental biologists, and industry experts to fully elucidate how plastic byproducts influence the risk and progression of bladder and other urological cancers.
Zhang et al. (Tue,) studied this question.