EpCAM-claudin-tetraspanin-modulated ovarian cancer progression and drug resistance

Frizzled 6 endows high-grade serous ovarian cancer with stem-like properties and chemoresistance

Stem-like properties contribute to tumor growth, metastasis, and chemoresistance. High-grade serous ovarian cancer (HGSOC) exhibits a very aggressive phenotype characterized by extensive metastasis, rapid progression, and therapy resistance. Frizzled 6 (FZD6) is overexpressed in HGSOC, and higher levels of FZD6 have been associated with shorter survival times in patients with HGSOC. Functionally, FZD6 promotes HGSOC growth and peritoneal metastasis. It endues HGSOC cells with stem-like properties by modulating POU5F1, ALDH1, and EPCAM. It can also desensitize HGSOC cells to certain chemical drugs. As a putative ligand for FZD6, WNT7B is also implicated in cell proliferation, stem-like properties, invasion and migration, and chemoresistance. SMAD7 is a downstream component of FZD6 signaling that is thought to mediate FZD6-associated phenotypes, at least in part. Therefore, FZD6/WNT7B-SMAD7 can be considered a tumor-promoting signaling pathway in HGSOC that may be responsible for tumor growth, peritoneal metastasis, and chemoresistance.

Regulation of the Function and Expression of EpCAM

The epithelial cell adhesion molecule (EpCAM) is a single transmembrane protein on the cell surface. Given its strong expression on epithelial cells and epithelial cell-derived tumors, EpCAM has been identified as a biomarker for circulating tumor cells (CTCs) and exosomes and a target for cancer therapy. As a cell adhesion molecule, EpCAM has a crystal structure that indicates that it forms a cis-dimer first and then probably a trans-tetramer to mediate intercellular adhesion. Through regulated intramembrane proteolysis (RIP), EpCAM and its proteolytic fragments are also able to regulate multiple signaling pathways, Wnt signaling in particular. Although great progress has been made, increasingly more findings have revealed the context-specific expression and function patterns of EpCAM and their regulation processes, which necessitates further studies to determine the structure, function, and expression of EpCAM under both physiological and pathological conditions, broadening its application in basic and translational cancer research.

High-expressed ACAT2 predicted the poor prognosis of platinum-resistant epithelial ovarian cancer

BACKGROUND

Acetyl-CoA acetyltransferase 2 (ACAT2) is a lipid metabolism enzyme and rarely was researched in epithelial ovarian cancer (EOC).

METHODS

ACAT2 expressions were confirmed in two pairs of cell lines (A2780 and A2780/DDP, OVCAR8 and OVCAR8/DDP) from Gene Expression Omnibus database by bioinformatics analysis, and in A2780 and A2780/DDP cell lines by quantitative real-time polymerase chain reaction and western blotting. Tissue samples were stained by immunohistochemistry and scored for ACAT2 expression. The relationships between ACAT2 expression and clinicopathological characteristics were analyzed by χ2 test. The prognosis of ACAT2 was analyzed by the log-rank tests and Cox regression models.

RESULTS

ACAT2 was remarkably upregulated in the above drug-resistant cell lines by mRNA (all P < 0.05) and protein expression (P = 0.026) than those in sensitive ones. Patients were classified as ACAT2-high (n = 51) and ACAT2-low (n = 26) according to immunohistochemical score. ACAT2 expression had a significantly inverse correlation with FIGO stage (P = 0.030) and chemo-response (P = 0.041). A marginal statistical significance existed in ACAT2 expression and ascites volume (P = 0.092). Univariate analysis suggested that high-expressed ACAT2 was associated with decreased platinum-free interval (PFI) (8.57 vs. 14.13 months, P = 0.044), progression-free survival (PFS) (14.12 vs. 19.79 months, P = 0.039) and overall survival (OS) (36.89 vs. 52.40 months, P = 0.044). Multivariate analysis demonstrated that ACAT2 expression (hazard ratio = 2.18, 95% confidence interval: 1.15-4.11, P = 0.017) affected OS independently, rather than PFI and PFS.

CONCLUSION

The expression of ACAT2 in A2780/DDP and OVCAR8/DDP was higher than the corresponding A2780 and OVCAR8. High-expressed ACAT2 was associated with advanced FIGO stage, chemo-resistance, and decreased PFI, PFS and OS. It was an independent prognostic factor of OS in EOC.

Efficacy of epi-1 modified epirubicin and curcumin encapsulated liposomes targeting-EpCAM in the inhibition of epithelial ovarian cancer cells

Treatment of epithelial ovarian cancer (EOC) is a challenge because it still leads to unsatisfactory clinical prognosis. This is due to the toxicity and poor targeting of chemotherapeutic agents, as well as metastasis of the tumor. In this study, we designed a targeted liposome with nanostructures to overcome these problems. In the liposomes, epirubicin and curcumin were encapsulated to achieve their synergistic antitumor efficacy, while Epi-1 was modified on the liposomal surface to target epithelial cell adhesion molecule (EpCAM). Epi-1, a macrocyclic peptide, exhibits active targeting for enhanced cellular uptake and potent cytotoxicity against tumor cells. The encapsulation of epirubicin and curcumin synergistically inhibited the formation of neovascularization and vasculogenic mimicry (VM) channels, thereby suppressing tumor metastasis on SKOV3 cells. The dual drug loaded Epi-1-liposomes also induced apoptosis and downregulated metastasis-related proteins for effective antitumor in vitro. In vivo studies showed that dual drug loaded Epi-1-liposomes prolonged circulation time in the blood and increased the selective accumulation of drug at the tumor site. H&E staining and immunohistochemistry with Ki-67 also showed that targeted liposomes elevated antitumor activity. Also, targeted liposomes downregulated angiogenesis-related proteins to inhibit angiogenesis and thus tumor metastasis. In conclusion, the production of dual drug loaded Epi-1-liposomes is an effective strategy for the treatment of EOC.

Protein palmitoylation in cancer: molecular functions and therapeutic potential

Protein S-palmitoylation (hereinafter referred to as protein palmitoylation) is a reversible lipid posttranslational modification catalyzed by the zinc finger DHHC-type containing (ZDHHC) protein family. The reverse reaction, depalmitoylation, is catalyzed by palmitoyl-protein thioesterases (PPTs), including acyl-protein thioesterases (APT1/2), palmitoyl protein thioesterases (PPT1/2), or alpha/beta hydrolase domain-containing protein 17A/B/C (ABHD17A/B/C). Proteins encoded by several oncogenes and tumor suppressors are modified by palmitoylation, which enhances the hydrophobicity of specific protein subdomains, and can confer changes in protein stability, membrane localization, protein-protein interaction, and signal transduction. The importance for protein palmitoylation in tumorigenesis has just started to be elucidated in the past decade; palmitoylation appears to affect key aspects of cancer, including cancer cell proliferation and survival, cell invasion and metastasis, and antitumor immunity. Here we review the current literature on protein palmitoylation in the various cancer types, and discuss the potential of targeting of palmitoylation enzymes or palmitoylated proteins for tumor treatment.

Assessment of TSPAN Expression Profile and Their Role in the VSCC Prognosis

The role and prognostic value of tetraspanins (TSPANs) in vulvar squamous cell carcinoma (VSCC) remain poorly understood. We sought to primarily determine, at both the molecular and tissue level, the expression profile of the TSPANs CD9, CD63, CD81, and CD82 in archived VSCC samples (n = 117) and further investigate their clinical relevance as prognostic markers. Our studies led us to identify CD63 as the most highly expressed TSPAN, at the gene and protein levels. Multicomparison studies also revealed that the expression of CD9 was associated with tumor size, whereas CD63 upregulation was associated with histological diagnosis and vascular invasion. Moreover, low expression of CD81 and CD82 was associated with worse prognosis. To determine the role of TSPANs in VSCC at the cellular level, we assessed the mRNA levels of CD63 and CD82 in established metastatic (SW962) and non-metastatic (SW954) VSCC human cell lines. CD82 was found to be downregulated in SW962 cells, thus supporting its metastasis suppressor role. However, CD63 was significantly upregulated in both cell lines. Silencing of CD63 by siRNA led to a significant decrease in proliferation of both SW954 and SW962. Furthermore, in SW962 particularly, CD63-siRNA also remarkably inhibited cell migration. Altogether, our data suggest that the differential expression of TSPANs represents an important feature for prognosis of VSCC patients and indicates that CD63 and CD82 are likely potential therapeutic targets in VSCC.

Meta-analysis based gene expression profiling reveals functional genes in ovarian cancer

Background: Ovarian cancer causes high mortality rate worldwide, and despite numerous attempts, the outcome for patients with ovarian cancer are still not well improved. Microarray-based gene expressional analysis provides with valuable information for discriminating functional genes in ovarian cancer development and progression. However, due to the differences in experimental design, the results varied significantly across individual datasets.

Methods: In the present study, the data of gene expression in ovarian cancer were downloaded from Gene Expression Omnibus (GEO) and 16 studies were included. A meta-analysis based gene expression analysis was performed to identify differentially expressed genes (DEGs). The most differentially expressed genes in our meta-analysis were selected for gene expression and gene function validation.

Results: A total of 972 DEGs with P-value < 0.001 were identified in ovarian cancer, including 541 up-regulated genes and 431 down-regulated genes, among which 92 additional DEGs were found as gained DEGs. Top five up- and down-regulated genes were selected for the validation of gene expression profiling. Among these genes, up-regulated CD24 molecule (CD24), SRY (sex determining region Y)-box transcription factor 17 (SOX17), WFDC2, epithelial cell adhesion molecule (EPCAM), innate immunity activator (INAVA), and down-regulated aldehyde oxidase 1 (AOX1) were revealed to be with consistent expressional patterns in clinical patient samples of ovarian cancer. Gene functional analysis demonstrated that up-regulated WFDC2 and INAVA promoted ovarian cancer cell migration, WFDC2 enhanced cell proliferation, while down-regulated AOX1 was functional in inducing cell apoptosis of ovarian cancer.

Conclusion: Our study shed light on the molecular mechanisms underlying the development of ovarian cancer, and facilitated the understanding of novel diagnostic and therapeutic targets in ovarian cancer.