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Published on: November 3, 2013
Differential expression of E-prostanoid receptors in human hepatocellular carcinoma
Marco Breinig1, Ralf Rieker, Eva Eiteneuer
1Department of General Pathology, University Hospital, 69120 Heidelberg, Germany.
Abstract:
Recent studies have shown that inhibition of cyclooxygenases (e.g. COX-2) exerts antitumorigenic effects on hepatocellular carcinomas (HCCs), which are to a significant extent due to the abrogation of PGE(2) synthesis. PGE(2) acts via differentially regulated prostaglandin receptors (EP(1-4)). Our study was designed to investigate the expression pattern of EP-receptors in HCCs and to evaluate the therapeutic potential of selective EP-receptor antagonists. Using tissue microarrays including a total of 14 control livers, 17 liver cirrhoses, 22 premalignant dysplastic nodules (DNs) and 162 HCCs with different histological grades, the expression of COX-2, mPGES-1 and -2 and EP(1-4)-receptors was analyzed. Western immunoblot analyses were performed to confirm the expression in HCC cell lines. The effects of EP(1-4)-receptor antagonism on cell viability and apoptosis were investigated using MTT-assays and FACS-analyses, respectively. COX-2, mPGES-1 and -2 and EP(1-4)-receptors were expressed in all HCC tissues. COX-2 expression was highest in DNs and declined with loss of HCC-differentiation. With respect to COX-2 expression, a converse expression of EP(1-3) -receptors and mPGES-1 and -2 was found in DNs compared to HCCs. Selectively antagonizing EP(1)- and EP(3)-receptors reduced the viability of HCC cells in a dose-dependent manner, which was associated with apoptosis induction. Our results suggest a differential regulation of EP-receptor subtype expression with dedifferentiation of HCCs in which a converse expression pattern for COX-2 in comparison to EP(1-3)-receptors occurs. Of clinical interest, selectively antagonizing EP(1)- and EP(3)-receptors may provide a novel systemic therapeutic approach to the treatment of HCCs.
Insights
Inhibiting cyclooxygenase-2 (COX-2) and targeting prostaglandin E2 (PGE2) receptors EP1 and EP3 show promise for treating hepatocellular carcinoma (HCC). Selective EP1 and EP3 receptor antagonism reduced HCC cell viability and induced apoptosis.
Area of Science:
- Hepatocellular Carcinoma Research
- Cancer Therapeutics
- Molecular Biology
Background:
- Cyclooxygenase-2 (COX-2) inhibition shows antitumor effects in hepatocellular carcinoma (HCC) by reducing prostaglandin E2 (PGE2) synthesis.
- PGE2 exerts its effects through differentially regulated prostaglandin receptors (EP1-4).
- Understanding EP receptor expression patterns in HCC is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the expression patterns of EP receptors in HCC tissues.
- To evaluate the therapeutic potential of selective EP receptor antagonists in HCC.
- To analyze the correlation between COX-2, mPGES-1/2, and EP receptor expression in HCC progression.
Main Methods:
- Analysis of COX-2, mPGES-1/2, and EP1-4 receptor expression in tissue microarrays (14 control livers, 17 liver cirrhoses, 22 dysplastic nodules, 162 HCCs).
- Western immunoblotting to confirm expression in HCC cell lines.
- MTT assays and FACS analyses to assess the effects of EP receptor antagonism on HCC cell viability and apoptosis.
Main Results:
- COX-2, mPGES-1/2, and EP1-4 receptors were expressed in all HCC tissues.
- COX-2 expression was highest in dysplastic nodules and decreased with HCC dedifferentiation.
- A converse expression pattern was observed for COX-2 versus EP1-3 receptors and mPGES-1/2 in dysplastic nodules compared to HCCs.
- Selective antagonism of EP1 and EP3 receptors dose-dependently reduced HCC cell viability and induced apoptosis.
Conclusions:
- HCC dedifferentiation is associated with differential regulation of EP receptor subtype expression.
- A converse expression pattern exists between COX-2 and EP1-3 receptors during HCC dedifferentiation.
- Selective EP1 and EP3 receptor antagonism represents a potential novel systemic therapeutic strategy for HCC treatment.
