Potential Role and Clinical Value of PPP2CA in Hepatocellular Carcinoma

Integrating single-cell and bulk RNA sequencing reveals CK19 + cancer stem cells and their specific SPP1 + tumor-associated macrophage niche in HBV-related hepatocellular carcinoma

PURPOSE

Cytokeratin 19-positive cancer stem cells (CK19 + CSCs) and their tumor-associated macrophages (TAMs) have not been fully explored yet in the hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC).

EXPERIMENTAL DESIGN

Single-cell RNA sequencing was performed on the viable cells obtained from 11 treatment-naïve HBV-associated HCC patients, including 8 CK19 + patients, to elucidate their transcriptomic landscape, CK19 + CSC heterogeneity, and immune microenvironment. Two in-house primary HCC cohorts (96 cases-related HBV and 89 cases with recurrence), TCGA external cohort, and in vitro and in vivo experiments were used to validate the results.

RESULTS

A total of 64,581 single cells derived from the human HCC and adjacent normal tissues were sequenced, and 11 cell types were identified. The result showed that CK19 + CSCs were phenotypically and transcriptionally heterogeneous, co-expressed multiple hepatics CSC markers, and were positively correlated with worse prognosis. Moreover, the SPP1 + TAMs (TAM_SPP1) with strong M2-like features and worse prognosis were specifically enriched in the CK19 + HCC and promoted tumor invasion and metastasis by activating angiogenesis. Importantly, matrix metalloproteinase 9 (MMP9) derived from TAM_SPP1, as the hub gene of CK19 + HCC, was activated by the VEGFA signal.

CONCLUSIONS

This study revealed the heterogeneity and stemness characteristics of CK19 + CSCs and specific immunosuppressive TAM_SPP1 in CK19 + HCC. The VEGFA signal can activate TAM_SPP1-derived MMP9 to promote the invasion and metastasis of CK19 + HCC tumors. This might provide novel insights into the clinical treatment of HCC patients.

Targeting Protein Phosphatases for the Treatment of Chronic Liver Disease

There exists a huge number of patients suffering from chronic liver disease worldwide. As a disease with high incidence and mortality worldwide, strengthening the research on the pathogenesis of chronic liver disease and the development of novel drugs is an important issue related to the health of all human beings. Phosphorylation modification of proteins plays a crucial role in cellular signal transduction, and phosphatases are involved in the development of liver diseases. Therefore, this article summarized the important role of protein phosphatases in chronic liver disease with the aim of facilitating the development of drugs targeting protein phosphatases for the treatment of chronic liver disease.

YTHDF2 exerts tumor-suppressor roles in gastric cancer via up-regulating PPP2CA independently of m6A modification

BACKGROUND

YTHDF2 is one of important readers of N6-methyladenosine (m⁶A) modification on RNA. Growing evidence implicates that YTHDF2 takes an indispensable part in the regulation of tumorigenesis and metastasis in different cancers, but its biological functions and underlying mechanisms remain elusive in gastric cancer (GC).

AIM

To investigate the clinical relevance and biological function of YTHDF2 in GC.

RESULTS

Compared with matched normal stomach tissues, YTHDF2 expression was markedly decreased in gastric cancer tissues. The expression level of YTHDF2 was inversely associated with gastric cancer patients' tumor size, AJCC classification and prognosis. Functionally, YTHDF2 reduction facilitated gastric cancer cell growth and migration in vitro and in vivo, whereas YTHDF2 overexpression exhibited opposite phenotypes. Mechanistically, YTHDF2 enhanced expression of PPP2CA, the catalytic subunit of PP2A (Protein phosphatase 2A), in an m⁶A-independent manner, and silencing of PPP2CA antagonized the anti-tumor effects caused by overexpression of YTHDF2 in GC cells.

CONCLUSION

These findings demonstrate that YTHDF2 is down-regulated in GC and its down-regulation promotes GC progression via a possible mechanism involving PPP2CA expression, suggesting that YTHDF2 may be a hopeful biomarker for diagnosis and an unrevealed treatment target for GC.

LCMT1 indicates poor prognosis and is essential for cell proliferation in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most malignant type of cancers. Leuci carboxyl methyltransferase 1 (LCMT1) is a protein methyltransferase that plays an improtant regulatory role in both normal and cancer cells. The aim of this study is to evaluate the expression pattern and clinical significance of LCMT1 in HCC.

METHODS

The expression pattern and clinical relevance of LCMT1 were determined using the Gene Expression Omnibus (GEO) database, the Cancer Genome Atlas (TCGA) program, and our datasets. Gain-of-function and loss-of-function studies were employed to investigate the cellular functions of LCMT1 in vitro and in vivo. Quantitative real-time polymerase chain reaction (RT-PCR) analysis, western blotting, enzymatic assay, and high-performance liquid chromatography were applied to reveal the underlying molecular functions of LCMT1.

RESULTS

LCMT1 was upregulated in human HCC tissues, which correlated with a "poor" prognosis. The siRNA-mediated knockdown of LCMT1 inhibited glycolysis, promoted mitochondrial dysfunction, and increased intracellular pyruvate levels by upregulating the expression of alani-neglyoxylate and serine-pyruvate aminotransferase (AGXT). The overexpression of LCMT1 showed the opposite results. Silencing LCMT1 inhibited the proliferation of HCC cells in vitro and reduced the growth of tumor xenografts in mice. Mechanistically, the effect of LCMT1 on the proliferation of HCC cells was partially dependent on PP2A.

CONCLUSIONS

Our data revealed a novel role of LCMT1 in the proliferation of HCC cells. In addition, we provided novel insights into the effects of glycolysis-related pathways on the LCMT1regulated progression of HCC, suggesting LCMT1 as a novel therapeutic target for HCC therapy.

The effect of PPP2CA expression on the prognosis of patients with hepatocellular carcinoma and its molecular biological characteristics

BACKGROUND

To investigate the role of the PPP2CA gene in the prognosis of patients with hepatocellular carcinoma (HCC) and its molecular biological characteristics.

METHODS

We performed comparison of the expression of PPP2CA in HCC and non-HCC tissues of HCC patients who underwent surgery for the first time in the Tumor Hospital of Guangxi Medical University from July 2017 to July 2019, and retrospectively analyzed the relevant clinical data and prognosis. The GSE76427 data set and bioinformatics and public databases were used to compare the expression of PPP2CA between HCC and non-cancer tissues. Gene Ontology (GO) analysis was performed of PPP2CA and its differential genes and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway. A protein-protein interaction (PPI) network of PPP2CA and its differentially expressed genes (DEGs) was constructed from the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database and visualized by Cytoscape software.

RESULTS

The immunohistochemistry (IHC) of tissue sections confirmed that PPP2CA was highly expressed in most HCC tissues; the high expression of PPP2CA was significantly correlated with microvascular invasion (MVI) and portal vein tumor thrombi (P<0.05). Participants in the PPP2CA high expression group had worse overall survival (OS; P=0.04) and recurrence-free survival (RFS; P=0.019). The PPP2CA gene and 71 DEGs were mainly enriched in the nuclear division, organelle fission, nuclear chromosome separation, and chromatid separation process, and KEGG analysis revealed enrichment in drug metabolism-cytochrome metabolism of xenobiotics by P450 and cytochrome P450. Finally, through the PPI network, CCNA2, AURKB, TOP2A, NCAPG, MCM2, CDC20, CCMB2, AURKA, and MGST1 were identified as the top 9 highly connected hub genes.

CONCLUSIONS

The PPP2CA gene is highly expressed in HCC tissues. The high expression of PPP2CA is significantly associated with poor prognosis. Through the analysis of DEGs, GO and KEGG pathway analysis, it was found that PPP2CA may act on liver cancer through multiple targets and multiple pathways, and PPP2CA plays a promoting role in HCC.