Background and Aims: HCC is a highly heterogeneous disease that is caused largely by genomic copy number variations. Herein, the mechanistic and therapeutically targeted role of vacuolar protein sorting 72 homologue (VPS72), a novel copy number variation cis-driven gained gene identified by genome-wide copy number variation and transcriptome analyses in HCC, is not well understood. Approach and Results: First, overexpression of VPS72 enhanced the initiation and progression of HCC in vitro and in vivo. Mechanistically, VPS72 interacted with the oncoproteins MYC and actin-like 6A (ACTL6A) and promoted the formation of the ACTL6A/MYC complex. Furthermore, ACTL6A regulated VPS72 protein stability by weakening the interaction between tripartite motif containing 21 (TRIM21) and VPS72. Thus, the interaction between VPS72 and ACTL6A enhanced the affinity of MYC for its target gene promoters and promoted their transcription, thereby contributing to HCC progression, which was inhibited by adeno-associated virus serotype 8 (AAV8)-mediated short hairpin RNA (shRNA) against VPS72. Conclusions: This study reveals the molecular mechanism of ACTL6A/VPS72/MYC in HCC, providing a theoretical basis and therapeutic target for this malignancy.

TurboID, a proximity labeling method based on mutant biotin ligase, is an efficient new technique for recognizing protein–protein interactions and has been successfully applied to living cells. Sialic acid is typically the terminal monosaccharide attached to many glycoproteins and plays many important roles in many biological processes. However, the lack of enrichment methods for the terminal sialic acid glycosylation in vivo hinders the identification and analysis of this glycosylation. Here, we introduced TurboID to identify the terminal sialic acid glycosylation in living cells. SpCBM, the carbohydrate-binding domain of sialidase from Streptococcus pneumoniae, was fused with TurboID and overexpressed in HeLa cells. After streptavidin-based purification and detection by mass spectrometry (MS), we identified 31 terminal sialic acid N-glycosylated sites and 1359 putative terminal sialic acid glycosylated proteins, many of which were located in the cytoplasm and nucleus.

Intrahepatic cholangiocarcinoma (iCCA), the second most common subtype of primary liver cancer around the world, is an aggressive neoplasm with high metastastic potential, which leads to a low rate of curative resections and dismal prognosis. In previous studies, Sulfatase 2 (SULF2) has been reported to regulate various important oncogenic signaling pathways and promote iCCA progression. Further research is needed to explore the role of SULF2 in iCCA metastasis. In this study, we verified the overexpression of SULF2 in iCCA tissues and its positive correlation with advanced stage and poor prognosis. Trans-well migration and invasion assay and mouse models explored the impact of SULF2 on iCCA metastasis in vitro and in vivo. We also demonstrated that SULF2 facilitated iCCA metastasis through upregulating CXCR4 transcription mediated by the transcription factor YBX1. Moreover, SULF2 could recruit USP7 to interact with YBX1 and inhibit Lys48-polyubiquitination of YBX1, stabilizing YBX1 and promoting a functional YBX1/CXCR4 axis. Combining SULF2 monoclonal antibody with SU056 had a synergistic effect in suppressing iCCA progression and metastasis of mouse models. In conclusion, SULF2 promotes iCCA progression and metastasis through an intracellular SULF2-YBX1-CXCR4 axis, and SULF2 monoclonal antibody combined with YBX1 inhibitor SU056 may be a potentially promising treatment strategy for iCCA.