CCL20 mediates the effect of cathepsin S on hepatocellular carcinoma development insights from Mendelian randomization and bioinformatics analysis

Dysregulation of cathepsins is associated with cancer development and progression. However, their specific role in hepatocellular carcinoma (HCC) remains unclear. We employed two-sample Mendelian randomization (MR) analyses to investigate potential causal relationships between cathepsins, 91 circulating inflammatory cytokines (CICs), and HCC. Subsequently, we explored causal associations between identified cathepsins and carcinogenic CICs. Finally, using the GSE14520 dataset, we conducted comprehensive bioinformatics analyses on the encoding genes of the screened cathepsins and CICs. Inverse-variance weighted (IVW) MR revealed that the genetically predicted Cathepsin S (CTSS) and seven CICs, including C-C motif chemokine 20 (CCL20), Fibroblast growth factor 19, Interleukin-1-alpha, Interleukin-20 receptor subunit alpha, Interleukin-24, Monocyte chemoattractant protein-3 and Stem cell factor levels, were intrinsically associated with increased HCC risk. Additionally, a casual estimate from Cathepsin S to CCL20 was identified. Sensitivity analysis found little evidence of heterogeneity and horizontal pleiotropy. CTSS and CCL20 gene expression was significantly dysregulated between HCC and adjacent normal liver tissue, exhibiting a positive correlation. Based on CTSS and CCL20 expression levels, we stratified the GSE14520 set into four clusters. Notably, the CTSShiCCL20low subgroup carried the most dismal overall survival, which was further validated in the GSE76427 and International Cancer Genome Consortium (ICGC) datasets. This subgroup also exhibited relatively lower predicted half-maximal inhibitory concentrations (IC50s) of multiple chemo- and targeted-therapies. Moreover, significant differences among the four clusters were observed in the stromal and immune score, immunocyte infiltration levels, especially Macrophages M1, Monocytes, Mast cell resting and Dendritic cells activated. Our exploratory analyses suggest that CCL20 may mediate the effect of CTSS on HCC development. Patients with CTSShighCCL20low HCC tumors may have a poorer prognosis but could be more susceptible to certain chemotherapeutic and targeted drugs. However, further in vivo and in vitro are required to elucidate the underlying mechanisms.