STOML2 Drives Liver Cancer Cell Growth Through PI3K/AKT Pathway Activation

According to a study published in the Egyptian Liver Journal, the protein STOML2 is markedly overexpressed in liver tumour tissue, and when the researchers silenced it in a highly metastatic liver cancer cell line, the cells lost much of their ability to proliferate, invade and migrate, while far more of them underwent programmed cell death. The mechanistic explanation, the authors report, lies in the PI3K/AKT signalling pathway, a central growth-promoting circuit inside cells: knocking down STOML2 reduced the phosphorylated, activated forms of PI3K and AKT without changing the total amounts of either protein, indicating that STOML2 acts on the pathway’s activation state rather than on its abundance.

The study, led by Mengyan Li, Jianli Chen, Kanxin Jin and Shiyi Chen, combined large-scale public database mining with laboratory experiments on cultured cells. From the Cancer Genome Atlas liver cancer cohort, which included 374 hepatocellular carcinoma cases and 50 normal liver tissue samples, the team found that STOML2 messenger RNA was significantly higher in tumours than in normal tissue, with a median expression of roughly 7.0 in tumours against 6.3 in normal samples on a log-transformed scale. Proteomics data from the CPTAC database independently confirmed that STOML2 protein was also elevated in tumour tissue. In an analysis of 50 paired samples, tumour tissue showed significantly higher STOML2 expression than the adjacent non-cancerous tissue taken from the same patients, a design that controls for individual variation between donors.

Immunohistochemical data from the Human Protein Atlas added a spatial dimension to the finding. In normal hepatocytes, STOML2 showed moderate staining in the cytoplasm and on the cell membrane, whereas hepatocellular carcinoma tissue displayed strong positive staining in the same compartments. The consistency across three independent data sources, at both the transcript and protein levels, strengthens the conclusion that STOML2 upregulation is a genuine feature of liver tumours rather than an artefact of any single dataset or measurement platform.

The prognostic signal was equally consistent. When patients in the TCGA cohort were divided into high and low STOML2 expression groups using the median expression value as the cutoff, those in the high-expression group had significantly shorter overall survival, with a hazard ratio of 1.67 reported in the study’s abstract. Time-dependent receiver operating characteristic analysis gave an area under the curve of 0.690 for predicting one-year survival, with a 95 percent confidence interval of 0.626 to 0.754, indicating moderate prognostic discrimination. The authors acknowledge in their discussion that the findings come from a single, highly metastatic cell line and have not yet been validated in in vivo experiments, so the conclusions may not fully represent all hepatocellular carcinoma subtypes and require further study in additional cell lines and animal models.

To understand what STOML2 might be doing inside tumour cells, the researchers turned to gene set enrichment analysis of the TCGA data. Samples with high STOML2 expression were significantly enriched in several cancer-related signalling pathways, including Wnt, MAPK and PI3K-Akt. The PI3K-Akt pathway showed the strongest association, with a normalized enrichment score of 1.733 and an adjusted P value below 0.001, compared with 1.621 for MAPK and 1.532 for Wnt. This bioinformatic prediction set the direction for the laboratory work that followed, providing a specific pathway to test rather than an open-ended search.

For the functional experiments, the team screened six hepatocellular carcinoma cell lines using integrated data from the CCLE database and GEO datasets. The highly metastatic line HCCLM3 showed the highest STOML2 messenger RNA expression, significantly exceeding other common lines such as HLF and JHH1, and was therefore selected for loss-of-function studies. Two independent siRNAs targeting STOML2 were transfected into HCCLM3 cells alongside a negative control, and the knockdown was verified at both the RNA and protein levels: messenger RNA fell by approximately 83 percent, and Western blotting confirmed a corresponding drop in STOML2 protein. The authors note that key experiments were validated with both siRNAs to guard against off-target effects, with the second siRNA’s results presented in supplementary material.

The phenotypic consequences of silencing STOML2 were substantial. In CCK-8 proliferation assays measured at 24, 48 and 72 hours after transfection, the knockdown group showed significantly reduced proliferative activity at every time point, with the inhibitory effect growing over time and peaking at 72 hours. Transwell invasion assays, in which cells must digest through a Matrigel matrix to reach a chemoattractant, showed a marked reduction in the number of cells that penetrated the membrane after STOML2 knockdown. Scratch wound healing assays told the same story: 24 hours after a uniform scratch was made across a confluent monolayer, the knockdown group’s wound closure rate was significantly lower than that of the two control groups, indicating slower migration. Flow cytometry using Annexin V-FITC and propidium iodide staining revealed that the knockdown group had significantly increased early and late apoptosis and a reduced proportion of live cells, while the blank and negative control groups did not differ from each other.

The mechanistic link came from Western blot analysis of pathway proteins. After STOML2 knockdown, the levels of phosphorylated PI3K and phosphorylated AKT dropped significantly, while total PI3K and total AKT remained unchanged. This dissociation between total and phosphorylated protein is the key observation: it suggests that STOML2 influences the activation state of the PI3K/AKT cascade rather than the expression of its components. In their discussion, the authors state that this pattern of findings suggests STOML2 may influence hepatocellular carcinoma cell behaviour by regulating the phosphorylation-activated state of the pathway, and they describe their work as the first systematic demonstration of this mechanism in hepatocellular carcinoma, while acknowledging that how STOML2 precisely regulates upstream or downstream molecules of the pathway remains unresolved.

Beyond the cell-autonomous effects, the database analyses pointed to a possible role in the tumour immune microenvironment and in drug resistance. STOML2 expression was positively correlated with the infiltration of myeloid dendritic cells, B cells, MAIT cells and macrophages, and with the expression of the immune checkpoint molecules PD-L1, CTLA-4 and LAG3, all at P values below 0.05. Single-cell analysis based on the TISCH database showed that STOML2 was predominantly expressed in malignant hepatocytes, with relatively low expression in immune and stromal cells, suggesting that its influence on the microenvironment may be indirect. The authors also found positive correlations between STOML2 and the drug-resistance-related genes HIF1A, SLC7A11 and AKT1 at P values below 0.001, and they note that the AKT-SLC7A11 axis is known to inhibit sorafenib-induced ferroptosis. They are explicit, however, that this resistance link is a hypothesis derived from bioinformatics alone and requires further experimental validation.

The study’s limitations are stated plainly in the discussion. All functional experiments were performed in a single, highly metastatic cell line chosen precisely because it expressed the most STOML2, and the authors acknowledge that the findings may not fully represent all hepatocellular carcinoma subtypes. No in vivo experiments were conducted; the team states that future work will use nude mouse xenograft models to evaluate the effects of STOML2 knockdown in living tumours, and that interactions with the MAPK and Wnt pathways, which were also enriched in the high-expression phenotype, remain to be investigated. Within those boundaries, the authors conclude that STOML2 may serve as a novel prognostic biomarker and potential therapeutic target for hepatocellular carcinoma, and that targeting the STOML2-PI3K/AKT axis could offer a new therapeutic strategy, particularly given that small-molecule inhibitors against the PI3K/AKT pathway have already shown potential in clinical trials. For now, the contribution is a carefully documented correlation between a protein’s abundance, a signalling pathway’s activation state and the malignant behaviour of liver cancer cells in culture, with the clinical implications awaiting the animal and multi-cell-line studies the authors have planned.

Subject of Research: The role of STOML2 in regulating hepatocellular carcinoma cell proliferation, invasion, migration and apoptosis via the PI3K/AKT signalling pathway

Article Title: Mechanism study of STOML2 regulating hepatocellular carcinoma cell proliferation, invasion, and migration by activating the PI3K/AKT signaling pathway

Article References: Li, M., Chen, J., Jin, K., & Chen, S. (2026). Mechanism study of STOML2 regulating hepatocellular carcinoma cell proliferation, invasion, and migration by activating the PI3K/AKT signaling pathway. Egyptian Liver Journal, 16(1), Article 72. https://doi.org/10.1186/s43066-026-00556-x

Image Credits: AI Generated

DOI: 10.1186/s43066-026-00556-x

Keywords: STOML2, hepatocellular carcinoma, PI3K/AKT pathway, liver cancer, prognosis, biomarker, apoptosis, cell migration, immune microenvironment, sorafenib resistance, gene expression, siRNA knockdown