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Background: IFN-λ has been shown to have a dual function in cancer, with its tumor-suppressive roles being well-established. However, the potential existence of a negative "tumor-promoting" effect of endogenous IFN-λ is still not fully understood. Methods: We conducted a comprehensive review and analysis of the perturbation of IFN-λ genes across various cancer types. Correlation coefficients were utilized to examine the relationship between endogenous IFN-λ expression and clinical factors, immune cell infiltration, tumor microenvironment, and response to immunotherapy. Genes working together with IFN-λ were obtained by constructing the correlation-based network related to IFN-λ and the gene interaction network in the KEGG pathway and IFN-λ-related genes obtained from the networks were integrated as candidate markers for the prognosis model. We then applied univariate and multivariate COX regression models to select cancer-specific independent prognostic markers associated with IFN-λ and to investigate risk factors for these genes by survival analysis. Additionally, computational methods were used to analyze the transcriptome, copy number variations, genetic mutations, and methylation of IFN-λ-related patient groups. Result: Endogenous expression of IFN-λ has been linked to poor prognosis in cancer patients, with the genes IFN-λ2 and IFN-λ3 serving as independent prognostic markers. IFN-λ acts in conjunction with related genes such as STAT1, STAT2, and STAT3 to affect the JAK-STAT signaling pathway, which promotes tumor progression. Abnormalities in IFN-λ genes are associated with changes in immune checkpoints and immune cell infiltration, which in turn affects cancer- and immune-related pathways. While there is increased immune cell infiltration in patients with IFN-λ expression, this does not improve survival prognosis, as T-cell dysfunction and an inflammatory environment are also present. The amplification of IFNL2 and IFNL3 copy number variants drives specific endogenous expression of IFN-λ in patients, and those with this specific expression have been found to have more mutations in the TP53 gene and lower levels of DNA methylation. Conclusion: Our study integrated multi-omics data to provide a comprehensive insight into the dark side of endogenous IFN-λ, providing a fundamental resource for further discovery and therapeutic exploration in cancer. [ABSTRACT FROM AUTHOR]

Breast cancer is known as the most prevalent cancer in women worldwide, and has an undeniable negative impact on public health, both physically, and mentally. This study aims to investigate the effects of toll‐like receptor 4 (TLR4) gene silencing on proliferation and apoptosis of human breast cancer cells to explore for a new theoretical basis for its treatment. TLR4 small interference RNA (siRNA) fragment recombinant plasmids were constructed, including TLR4 siRNA‐1, TLR4 siRNA‐2, and TLR4 siRNA‐3. Human breast cancer MCF‐7 and MDA‐MB‐231 cells were assigned into blank, negative control (NC), TLR4 siRNA‐1, TLR4 siRNA‐2, and TLR4 siRNA‐3 groups. MCF‐7 and MDA‐MB‐231 cell growth was detected by MTT assay. Apoptosis and cell cycle were determined by flow cytometry. Reverse transcription quantitative polymerase chain reaction (RT‐qPCR) and Western blot analysis were conducted to determine the expression of TLR4, CDK4, cyclin D1, Livin, Bcl‐2, p53, c‐FLIP, and caspase‐3. In comparison with the NC and blank groups, the TLR4 siRNA‐1, TLR4 siRNA‐2, and TLR4 siRNA‐3 groups showed decreased the expression of TLR4, inhibited proliferation of MCF‐7 and MDA‐MB‐231 cells and promoted MCF‐7 and MDA‐MB‐231 cell apoptosis, and the cells were blocked in G1 phase. In comparison with the NC and blank groups, in the TLR4 siRNA‐1, TLR4 siRNA‐2, and TLR4 siRNA‐3 groups, siRNA‐TLR4 significantly increased expression of p53 and caspase‐3 in MCF‐7 and MDA‐MB‐231 cells, while it decreased the expressions of CDK4, cyclinD1, Livin, Bal‐2, and c‐FLIP. The study demonstrates that TLR4 gene silencing inhibits proliferation and induces apoptosis of MCF‐7 and MDA‐MB‐231 cells. TLR4 gene silencing inhibits proliferation and induces apoptosis of MCF‐7 and MDA‐MB‐231 cells. [ABSTRACT FROM AUTHOR]