Association of caveolin-1 protein expression with hepatocellular carcinoma: a meta-analysis and literature review

Caveolin-1 protein expression as a prognostic biomarker of gastrointestinal tumours: A systematic review and meta-analysis

BACKGROUND

Gastrointestinal (GI) cancers remain a major threat worldwide, accounting for over 30% of cancer deaths. The identification of novel prognostic biomarkers remains a challenge despite significant advances in the field. The CAV1 gene, encoding the caveolin-1 protein, remains enigmatic in cancer and carcinogenesis, as it has been proposed to act as both a tumour promoter and a tumour suppressor.

METHODS

To analyse the differential role of caveolin-1 expression in both tumour cells and stroma in relation to prognosis in GI tumours, we performed a systematic review and meta-analysis according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines; PROSPERO registration number: CRD42022299148.

RESULTS

Our analysis showed that high levels of caveolin-1 in tumour cells were associated with poor prognosis and inferior overall survival (OS) in oesophageal and pancreatic cancer and hepatocellular carcinoma (HCC), but not in gastric and colorectal cancer. Importantly, our study showed that higher stromal caveolin-1 expression was associated with significantly longer OS and disease-free survival in colorectal cancer. Analysis of stromal caveolin-1 expression in the remaining tumours showed a similar trend, although it did not reach statistical significance.

CONCLUSIONS

The data suggest that caveolin-1 expression in the tumour cells of oesophageal, pancreatic cancer and HCC and in the stroma of colorectal cancer may be an important novel predictive biomarker for the clinical management of these diseases in a curative setting. However, the main conclusion of our analysis is that caveolin-1 expression should always be assessed separately in stroma and tumour cells.

Caveolin-1 and lipids: Association and their dualism in oncogenic regulation

Caveolin-1 (Cav-1) is a structural protein of caveolae that functions as a molecular organizer for different cellular functions including endocytosis and cellular signaling. Cancer cells take advantage of the physical position of Cav-1, as it can communicate with extracellular matrix, help to organize growth factor receptors, redistribute cholesterol and glycosphingolipids, and finally transduce signals within the cells for oncogenesis. Recent studies emphasize the exceeding involvement of Cav-1 with different lipid bodies and in altering the metabolism, especially lipid metabolism. However, the association of Cav-1 with different lipid bodies like lipid rafts, lipid droplets, cholesterols, sphingolipids, and fatty acids is remarkably dynamic. The lipid-Cav-1 alliance plays a dual role in carcinogenesis. Both cancer progression and regression are modified and affected by the type of lipid molecule's association with Cav-1. Accordingly, this Cav-1-lipid cooperation exemplifies a cancer-type-specific treatment strategy for a better prognosis of the disease. In this review, we first present Cav-1 as an oncogenic molecule and its communication via lipid raft. We discussed the involvement of Cav-1 with lipid droplets, Cholesterol, sphingolipids, gangliosides, and ceramides. Further, we describe the Cav-1-mediated altered Fatty acid metabolism in cancer and the strategic therapeutic approaches toward Cav-1 targeting.

CXCR4 promotes gefitinib resistance of Huh7 cells by activating the c-Met signaling pathway

C‐X‐C chemokine receptor type 4 (CXCR4) expression is associated with poor prognosis of hepatocellular carcinoma (HCC). The aim of this study was to explore the biological role of CXCR4 in gefitinib resistance of HCC. Compared with a normal, non‐gefitinib‐resistant, human HCC cell line (Huh7), CXCR4 mRNA and protein were highly expressed in gefitinib‐resistant Huh7 cells (Huh7‐R). Cell proliferation was decreased, and apoptosis was enhanced in Huh7 cells in the presence of gefitinib. These influences conferred by gefitinib treatment on proliferation and apoptosis of Huh7 cells were abolished by CXCR4 overexpression. CXCR4 knockdown reduced the proliferation ability of HuH‐7R cells after gefitinib treatment. Importantly, CXCR4 overexpression had no influence on caveolin 1 (Cav‐1) expression; similarly, Cav‐1 silencing did not cause a substantive change in CXCR4 expression. However, CXCR4 activated Cav‐1, c‐Met, and Raf‐1 in Huh7 cells, whereas Cav‐1 silencing repressed the expression of Raf‐1 and phosphorylated c‐Met in Huh7 cells. CXCR4 overexpression promoted proliferation and repressed apoptosis in gefitinib‐treated Huh7 cells, which was partly rescued by PHA‐665752 (a c‐Met inhibitor) treatment or c‐Met deficiency. Finally, we constructed a tumor xenograft model to determine the influence of CXCR4 overexpression on tumor growth of HCC. CXCR4 overexpression accelerated tumor growth of HCC, which was abrogated by c‐Met deficiency. These findings demonstrate that CXCR4 overexpression activates c‐Met via the Cav‐1 signaling pathway, thereby promoting gefitinib resistance of Huh7 cells. Thus, this study highlights novel insights into the mechanism of gefitinib resistance of HCC and CXCR4 may become a potential target for HCC treatment.

Synthesis and characterization of magnetic nanoparticles coated with polystyrene sulfonic acid for biomedical applications

The development of novel magnetic nanoparticles (MNPs) with satisfactory biocompatibility for biomedical applications has been the subject of extensive exploration over the past two decades. In this work, we synthesized superparamagnetic iron oxide MNPs coated with polystyrene sulfonic acid (PSS-MNPs) and with a conventional co-precipitation method. The core size and hydrodynamic diameter of the PSS-MNPs were determined as 8-18 nm and 50-200 nm with a transmission electron microscopy and dynamic light scattering, respectively. The saturation magnetization of the particles was measured as 60 emu g-1 with a superconducting quantum-interference-device magnetometer. The PSS content in the PSS-MNPs was 17% of the entire PSS-MNPs according to thermogravimetric analysis. Fourier-transform infrared spectra were recorded to detect the presence of SO3 - groups, which confirmed a successful PSS coating. The structural properties of the PSS-MNPs, including the crystalline lattice, composition and phases, were characterized with an X-ray powder diffractometer and 3D nanometer-scale Raman microspectrometer. MTT assay and Prussian-blue staining showed that, although PSS-MNPs caused no cytotoxicity in both NIH-3T3 mouse fibroblasts and SK-HEP1 human liver-cancer cells up to 1000 μg mL-1, SK-HEP1 cells exhibited significantly greater uptake of PSS-MNPs than NIH-3T3 cells. The low cytotoxicity and high biocompatibility of PSS-MNPs in human cancer cells demonstrated in the present work might have prospective applications for drug delivery.

New relationship of E2F1 and BNIP3 with caveolin-1 in lung cancer-associated fibroblasts

In recent years, studies have found that E2F1, a downstream effector of caveolin‐1 (Cav‐1), participates in tumor cell metabolic reprogramming. E2F1 modulates mitochondrial fusion and mitophagy. Bioinformatic analysis has identified the E2F1‐MFN2 axis as a regulator of mitophagy. Our data establish a new novel paradigm for regulation of the tumor cell metabolic reprogramming pathway by Cav‐1 that is operationally linked and mutually dependent on the transcriptional activation of E2F1 and induces mitophagy with BNIP3 in cancer‐associated fibroblasts (CAFs).

Lithium effects on vesicular trafficking in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is one of the most commonly malignant tumors worldwide, characterized by the presence of many heterogeneous molecular cell events that contribute to tumor growth and progression. Endocytic processes are intimately involved in various pathological conditions, including cancer, since they interface with various cellular signaling programs. The ability of lithium to induce cell death and autophagy and affect cell proliferation and intracellular signaling has been shown in various experimental tumor models. The aim of this study was to evaluate the effects of lithium on vesicular transport in hepatocellular carcinoma cells. Using transmission electron microscopy we have characterized the endocytic apparatus in hepatocellular carcinoma-29 (HCC-29) cells in vivo and detailed changes in endocytotic vesicles after 20 mM lithium carbonate administration. Immunofluorescent analysis was used to quantify cells positive for EEA1-positive early endosomes, Rab11-positive recycling endosomes and Rab7-positive late endosomes. Lithium treatment caused an increase in EEA1- and Rab11-positive structures and a decrease in Rab7-positive vesicles. Thus, lithium affects diverse endocytic pathways in HCC-29 cells which may modulate growth and development of hepatocellular carcinoma.