Integrative multi-omics analysis implicates the RNF40-LIMA1 axis in hepatocellular carcinoma progression and immune...

Ring Finger Protein 40 (RNF40), an E3 ubiquitin ligase, plays context-dependent roles in various cancers, serving as either a tumor suppressor or an oncogene. Critically, RNF40 targets LIM domain and actin-binding protein 1 (LIMA1) for degradation via the ubiquitin-proteasome pathway. LIMA1, which is involved in actin cytoskeleton organization, exerts opposing effects in different cancer types. However, the precise functional relationship between RNF40 and LIMA1 in Hepatocellular Carcinoma (HCC) remains poorly understood. Despite the efficacy of immune checkpoint inhibitors, intrinsic resistance affects 40-60% of patients, necessitating novel epigenetic and ubiquitin-related therapeutic targets.

This study investigated the molecular mechanisms through which RNF40-mediated ubiquitination of LIMA1 influences Hepatocellular Carcinoma (HCC) progression. We utilized an integrative approach combining multi-omics analysis including bulk transcriptomics, single-cell RNA sequencing (scRNA-seq), and spatial transcriptomics with experimental validation using in vitro assays and in vivo mouse models. Differential expression analysis, survival outcome correlation, immune infiltration assessment, and cell-cell communication analyses were performed to characterize the roles of RNF40 and LIMA1 in HCC.

LIMA1 was significantly overexpressed in HCC across multiple transcriptomic and proteomic datasets (log2FC>1.5, P < 0.001), and its upregulation correlated with accelerated tumor proliferation, migration, invasion as well as an immunosuppressive checkpoint-enriched TME featured by M2 macrophage infiltration (R = 0.498, P < 0.001) and CD8+ T cell exclusion. Single-cell and spatial transcriptomic analyses indicated predominant LIMA1 enrichment in malignant cells and tumor lesions. LIMA1 overexpression facilitated HCC clonogenicity, migration, invasion and xenograft tumor growth. Conversely, ectopic RNF40 expression suppressed these malignant phenotypes, and such inhibitory effects were fully abolished upon concurrent LIMA1 overexpression both in vitro and in vivo. Re-analysis of TCGA-LIHC revealed that LIMA1 failed to serve as an independent prognostic marker after adjusting for clinicopathological covariates, warranting cautious interpretation of its prognostic implication.

Our findings support the biological relevance of a functional RNF40-LIMA1 axis in HCC progression. Together with previously established biochemical evidence of RNF40-mediated LIMA1 ubiquitination and proteasome-dependent degradation, this study provides a rationale for further investigation of the RNF40-LIMA1 axis in HCC. The prognostic and immunotherapy-predictive value of LIMA1 requires validation in independent clinical cohorts and larger ICI-treated HCC datasets.