This study is the first to adopt a two-sample MR analysis strategy, utilizing data from large-scale GWAS to explore the potential causal relationship between multiple circulating inflammatory proteins and the risk of non-melanoma skin cancer (NMSC) from a genetic perspective. We found that inflammatory mediators such as CCL23, CCL25, EN-RAGE, IL-15RA, and IL-8, IL-1α have a positive causal relationship with increased NMSC risk. These findings are not only consistently supported by different MR analysis methods and multiple sensitivity tests, but also highly consistent with previous experimental and clinical observation studies, providing genetic evidence for the role of inflammation in the development of NMSC.
For the several positive associations found in this study, we will discuss their potential biological mechanisms and clinical implications. CCL23, CCL25, and IL-8 belong to the chemokine family, playing a key role in the development and progression of tumors. IL-8 can attract immune cells to the tumor microenvironment and promote inflammatory reactions, which may contribute to the growth and spread of tumor cells 26. CCL23 is associated with a variety of tumors and may affect tumor development by regulating the migration and activity of immune cells 27. CCL25 is expressed at increased levels in some tumors, attracting specific T-cell subsets to the tumor microenvironment, which may contribute to tumor immune escape. These small molecules can recruit various inflammatory cells (such as dendritic cells, T-cells, and neutrophils) to infiltrate tumor sites, inducing the formation of a pro-inflammatory immune microenvironment 28. Chemokines can also promote angiogenesis and epithelial-mesenchymal transformation, enhancing the invasion and metastasis of tumor cells 29, 30. Previous studies have reported elevated expression of CCL23, CCL25, and IL-8 in various solid tumors and hematological tumors, which is associated with adverse clinical features and prognosis 28, 31, 32. Our MR analysis results support their potential carcinogenic role in the development of NMSC, suggesting that precise regulation of these chemokines and their downstream effects may be a potential therapeutic target for NMSC. Future research can focus on more accurately determining the role of these factors in non-melanoma skin cancer and how to more effectively use this knowledge to develop new treatment strategies. Additionally, combining immunotherapy with treatment targeting these chemokines may provide new strategies for treating this type of skin cancer.
EN-RAGE (Extracellular Newly identified RAGE-binding protein), a member of the S100 protein family, binds to RAGE (Receptor for Advanced Glycation End products), activating multiple signaling pathways and promoting inflammatory reactions, cell proliferation, angiogenesis, and other processes 33. Studies have found that EN-RAGE is upregulated in multiple tumors and is associated with tumor aggressiveness, metastasis, and prognosis. In NMSC, EN-RAGE expression is significantly elevated. It may promote the occurrence and development of NMSC through the following mechanisms: activating signaling pathways such as NF-κB and MAPK, inducing the expression of pro-inflammatory factors and maintaining a sustained low-grade inflammatory state; promoting angiogenesis to provide nutrition for tumor growth; stimulating cancer cell proliferation and migration; inhibiting cancer cell apoptosis 34. In vitro studies have also confirmed that knocking down EN-RAGE can weaken the proliferation, migration, and angiogenesis ability of NMSC cells 35. EN-RAGE is involved in the development and progression of multiple tumors. Studies have found that EN-RAGE can induce angiogenesis and tumor cell invasion and metastasis, as well as activate and recruit inflammatory cells such as macrophages and neutrophils to promote the formation of a tumor-associated inflammatory and immunosuppressive microenvironment 36, 37. Our findings reveal the potential role of EN-RAGE in the development of NMSC, providing a genetic basis for further exploring its potential as a therapeutic target in this field. Overall, EN-RAGE is an important inflammatory factor in the development and progression of NMSC. Further research on the relationship between EN-RAGE and NMSC may provide new ideas and targets for early diagnosis and targeted treatment of NMSC.
IL-15RA, as the receptor subunit of IL-15, is involved in regulating various immune cell functions. The IL-15/IL-15RA pathway has been found to be abnormally activated in multiple tumors, involving key biological processes such as inducing tumor immune escape, promoting tumor angiogenesis, and maintaining tumor stem cell survival 38–40. Our MR findings provide genetic evidence that IL-15RA may play a significant role in the development of NMSC. There may be abnormal IL-15 signaling in the skin microenvironment of NMSC patients, but the exact molecular mechanism needs further elucidation. IL-15/IL-15RA pathway regulators have become new immune therapeutic targets for multiple tumors, and it is promising to explore related research in the field of NMSC in the future.
A causal association between high levels of IL-1α and increased risk of NMSC has been observed. IL-1α, a member of the interleukin family, is mainly produced by activated macrophages, neutrophils, and epithelial cells, playing a crucial role in innate and inflammatory responses 41. However, previous studies have also found that IL-1α is downregulated or absent in multiple tumors, and exogenous supplementation of IL-1α can inhibit tumor cell proliferation and invasion, suggesting its potential anti-tumor activity 42. Our MR research results may reflect this anti-tumor effect of IL-1α and provide a genetic basis for its application potential in the prevention and treatment of NMSC. IL-1α may exert its effect by inducing inflammatory responses to eliminate tumor cells, directly promoting tumor cell apoptosis, or stimulating anti-tumor immune surveillance, but the specific molecular mechanisms need further exploration.
In summary, the aforementioned findings support the view that inflammation plays a complex and bidirectional regulatory role in the development and progression of non-melanoma skin cancer (NMSC). Certain pro-inflammatory and chemotactic factors (such as CCL23, CCL25, EN-RAGE, IL-8, IL-15RA) promote the occurrence of NMSC by remodeling the tumor microenvironment (including immune cell infiltration, angiogenesis, and induction of epithelial-mesenchymal transition), while some inflammatory mediators with potential anti-tumor effects (such as TRANCE) may exert anti-tumor effects by directly inducing tumor cell apoptosis and stimulating the body's immune surveillance, thereby reducing the risk of NMSC. These findings reveal the central role and key function of inflammatory pathways in the development of NMSC and provide a forward-looking biological perspective for developing new prevention and targeted treatment strategies for NMSC.
The main advantage of this study is that it is the first to use MR analysis to explore the potential causal association between inflammation and NMSC risk, providing genetic evidence and causal inference for observational studies in this field. Compared with traditional observational studies, MR analysis can effectively avoid the influence of confounding factors and reverse causality, thereby obtaining a more reliable estimation of the causal relationship. We strictly screened multiple independent and effective instrumental variables, comprehensively applied different MR analysis methods and comprehensive sensitivity analysis strategies to ensure the robustness of the results. In addition, our GWAS sample size is relatively large, and the power evaluation results also show that it has sufficient detection ability for medium-risk levels, thereby increasing the credibility of the research findings.
However, our research also has some shortcomings that need to be improved. Firstly, although we have tried our best to exclude potential confounding biases, it is still difficult to completely rule out other biases such as horizontal expansion. Secondly, the genetic variation explained by the current instrumental variables used is generally low (< 10%), which indeed limits the statistical power for detecting small effects of exposure. Thirdly, we only considered the relationship between inflammatory proteins at the population level and the risk of NMSC, and have not yet evaluated whether there is heterogeneity in this association in different age groups, genders, or tumor stages. Future research is needed to be validated in larger populations.Fourthly, this study only focused on a few inflammatory proteins and did not cover a wider range of inflammatory pathways and mediators. Last but not least, our MR analyses are based on European populations, and whether they remain consistent in Asian populations remains to be studied.