Gap junctional intercellular communication and connexin 43 expression in ovarian carcinoma

doi:10.1016/S0002-9378(00)70135-9

American Journal of Obstetrics and Gynecology

Volume 182, Issue 5, May 2000, Pages 999-1000

https://doi.org/10.1016/S0002-9378(00)70135-9 Get rights and content

Abstract

Objectives: Gap junctions, which are composed of subunits termed connexins, are plasma membrane channels that link the interior of adjacent cells and permit cells to directly exchange small molecules and ions. Loss or dysfunction of gap junctions appears to be important in allowing cancer cells to escape growth regulation. In a previous study we showed that human ovarian surface epithelial cells exhibited extensive gap junctions and expression of connexin 43. These were nearly absent in human ovarian adenocarcinoma cell lines. To ensure that this variation was not artificially produced by culturing techniques, this study evaluated gap junctions and connexin 43 expressions in normal ovaries and in ovarian adenocarcinomas. Study Design: Specimens of normal ovaries and ovarian adenocarcinomas were obtained at the time of surgery and flash-frozen in liquid nitrogen. Connexin 43 immunostaining was performed on all specimens. Results: Among the 11 normal ovaries an average of 59% of the surface epithelium stained positively for connexin 43. In contrast, among the 10 ovarian adenocarcinomas only 19% of each specimen stained positively for connexin 43 (P = .01). Conclusion: Similar to our studies on human ovarian surface epithelial cells and ovarian adenocarcinoma cell lines, surgical specimens of normal ovary exhibited extensive connexin 43 expression, whereas connexin 43 expression was nearly absent in ovarian adenocarcinomas. It thus appears that the previously reported loss of gap junctions and connexin 43 was actually associated with a neoplastic process, rather than being artificially induced in the laboratory. (Am J Obstet Gynecol 2000;182:999-1000.)

Section snippets

Material and methods

Specimens of 11 normal ovaries and 5 serous adenocarcinomas were obtained at the time of laparotomy and flash frozen in liquid nitrogen. Five additional human ovarian serous cystadenocarcinomas were purchased from the Cooperative Human Tissue Network Gynecologic Division (Columbus, Ohio) through the Gynecologic Oncology Group. Ovarian tumors from the Cooperative Human Tissue Network were initially flash-frozen in liquid nitrogen and stored in liquid nitrogen; tissue blocks were sent on dry ice.

Results

In the 11 normal ovaries a mean of 59% of the surface epithelium stained positively for connexin 43. Many punctate fluorescent spots were present between the cells, and there was also diffuse cytoplasmic staining in the tissue. In contrast, ovarian adenocarcinomas showed little connexin 43 staining, with only a mean of 19% of each ovarian adenocarcinoma positively stained (P = .01). There was no difference in the mean percentage of staining between tumors obtained at the time of laparotomy and

Comment

We previously showed that human ovarian surface epithelial cells exhibited extensive gap junctional intercellular communications and expression of connexin 43, whereas gap junctional intercellular communications and connexin 43 expression were nearly absent in several human ovarian adenocarcinoma cell lines. To ensure that the losses of gap junctional intercellular communications and connexin 43 expression in human ovarian adenocarcinoma cell lines were not induced by the culture techniques

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Transforming growth factor-β stimulates human ovarian cancer cell migration by up-regulating connexin43 expression via Smad2/3 signaling
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Citation Excerpt :
Most patients are diagnosed at advanced stages (FIGO stages ΙΙΙ and ΙV) with a very low survival rate, whereas the 5-year survival rate is significantly increased when the disease remains localized within the ovary [14]. Compared with human ovarian surface epithelium, Cx43 expression levels are significantly down-regulated in human ovarian cancer cells [15,16]. Overexpression of Cx43 in the SKOV3 human ovarian cancer cell line has been shown to decrease cell proliferation and tumor formation in nude mice [17].
Reduced connexin43 (Cx43) expression is frequently detected in different types of human cancer. Cx43 has been shown to regulate cancer cell migration in a cell-type dependent manner. In both primary and recurrent human ovarian cancer, overexpression of TGF-β ligand and its receptors have been detected. TGF-β can regulate Cx43 expression in other cell types and stimulate human ovarian cancer cell migration. However, whether Cx43 can be regulated by TGF-β and is involved in TGF-β-stimulated cell migration in human ovarian cancer cells remain unknown. In this study, we demonstrate that TGF-β up-regulates Cx43 in two human ovarian cancer cell lines, SKOV3 and OVCAR4. The stimulatory effect of TGF-β on Cx43 expression is blocked by inhibition of TGF-β receptor. Treatment with TGF-β activates Smad2 and Smad3 signaling pathways in both ovarian cancer cell lines. In addition, siRNA-mediated knockdown of Smad2 or Smd3 abolishes TGF-β-induced up-regulation of Cx43 expression. Moreover, knockdown of Cx43 attenuates TGF-β-stimulated cell migration. This study demonstrates an important role for Cx43 in mediating the effects of TGF-β on human ovarian cancer cell migration.
Melanoma's connections to the tumour microenvironment
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Melanoma cells interact with and depend on seemingly normal cells in their tumour microenvironment to allow the acquisition of the hallmarks of solid cancer. In general, there are three types of interaction of melanoma cells with their microenvironment. First, there is bilateral communication between melanoma cells and the stroma, which includes fibroblasts, endothelial cells, immune cells, soluble molecules, and the extracellular matrix. Second, while under normal conditions keratinocytes control localisation and proliferative behaviour of melanocytes in the epidermis, once this balance is disturbed and a melanoma has developed, melanoma cells may take over the control of their epidermal tumour microenvironment. Finally, there are subcompartments within tumours with different microenvironmental milieu defined by their access to oxygen and nutrients. Therefore, different melanoma cells within a tumour face different microenvironments. Interactions between melanoma cells among each other and with the cell types in their microenvironment happen through endocrine and paracrine communication and/or through direct contact via cell-cell and cell-matrix adhesion, and gap junctional intercellular communication (GJIC). Connexins have been identified as key molecules for direct cell-cell communication and are also thought to be important for the release of signalling molecules from cells to the microenvironment. In this review we provide an update of the alterations in cell-cell communication in melanoma and the tumour microenvironment associated with melanoma development and progression.
High levels of connexin 43 mRNA in high grade astrocytomas. Study of 32 cases with in situ hybridization
2010, Acta Histochemica
Gap junctions are composed of a family of evolutionarily conserved integral plasma membrane proteins termed connexins. The aims of the research reported here were (1) to evaluate the Cx43 protein and mRNA of both low histological grade and high histological grade astrocyte tumors; (2) to evaluate if the immunohistochemistry of the Cx43 protein in astrocytomas could be correlated to histological grade, to proliferative activity (Ki67/Mib1-index) and to immunolabelling of the epidermal growth factor receptor (EGFR); (3) to evaluate if the reduction in levels of the Cx43 protein correlates with reduction in levels of the Cx43 mRNA. This study showed that the immunohistochemical labelling of Cx43 is reduced in grade III and grade IV. Decreased gap junction-mediated intercellular communication corresponds to decreased Cx43 and increased cellular proliferation rates, as measured by immunolabelling of the Ki67 nuclear antigen. This study demonstrated also the persistence in high grade astrocytomas of elevated levels of Cx43 mRNA. The reduced levels of Cx43 protein should not to be ascribed to a reduced genetic transcription, but to an alteration of the post-transcriptional mechanisms such as the regulation of its synthesis and/or the intracellular transport to membrane sites.
Gap junctions in the ovary: Expression, localization and function
2008, Molecular and Cellular Endocrinology
Gap junctions that allow the direct communication between cytoplasmic compartments of neighboring cells are present in a variety of tissues and organs and play pivotal roles in a wide range of physiological processes. In the ovary, gap junctions consist mainly of connexin (Cx) 43 and Cx37, and their indispensable role in regulating folliculogenesis and oogenesis is well established. The ovarian Cx43 is regulated by gonadotropins at the transcriptional, translational and post-translational levels whereas the regulation of the ovarian Cx37 is yet unknown. In addition to their involvement in normal ovarian functions, gap junction proteins, particularly Cx43, seem to act as cancer suppressors. A summary of our present knowledge regarding gap junctional communication (GJC) and the ovarian gap junction proteins in normally developing ovaries and under pathological conditions is presented in this review.
Loss of communication in ovarian cancer
2006, American Journal of Obstetrics and Gynecology
Citation Excerpt :
In addition, some of the cell lines were manipulated in vitro to demonstrate the effect of chemotherapy on characteristics relating to connexin expression. Although other investigators have shown decreased expression of Cx43 in some ovarian cancer cells and tumor tissue, the study of the expression of a variety of cells with a variety of connexins has not been performed previously.9-12 With respect to RT-PCR profiling, we demonstrate 11 of the connexins in all cell lines.
This study was undertaken to investigate the expression of connexins in ovarian cancer cell lines and assess correlation with chemosensitivity.
Eight cell lines were used in this study. Cytotoxicity assays with carboplatin and paclitaxel were performed. Reverse transcription-polymerase chain reaction (RT-PCR) was used to analyze the expression of gap junction proteins. Western blotting and immunohistochemical staining of selective gap junction proteins (connexin 26 and 43) were performed.
All 11 connexins were detected with RT-PCR profiling in ovarian cancer cells. Further experiments were performed to analyze protein expression with connexins 26 and 43. Levels of connexin proteins did not correlate with gene expression obtained with RT-PCR. Results obtained with immunoblotting were confirmed by immunohistochemistry. Carboplatin and paclitaxel sensitivities were determined and connexin 43 expression was associated with sensitivity to paclitaxel.
Expression of connexins is regulated at the translational level in ovarian cancer. Sensitivity to paclitaxel maybe associated with connexin 43.
Phosphorylation of the gap junction protein Connexin43 in CIN III lesions and cervical carcinomas
2006, Cancer Letters
Connexins are proteins that form the connexons, gap junction structures, which allow cells to communicate. Phosphorylation of connexins has been found to impair this communication. Using an antibody specifically recognizing the S279/S282-phosphorylated form of connexin43 (Cx43) for immunohistochemistry, we have analysed Cx43 phosphorylation in normal epithelium, CIN III lesions, and carcinomas of the cervix. We found that in normal epithelium the basal layer was devoid of staining and most of the protein was localized in stratum spinosum and stratum granulosum. In pre-malignant CIN-III lesions Cx43 was strongly phosphorylated, but the basal layer was still negative. In squamous carcinomas, the cells were intensely stained. In these tumours, sites of strong staining were adjacent to less stained regions, suggesting that the tumours are intrinsically heterogeneous. Immunoblotting of proteins extracted from carcinomas with the specific antibody showed the classical pattern of multiple reacting bands, with the appearance of low migrating forms of the protein. Our results suggest that increased S279/S282 phosphorylation of Cx43 is the result of altered tissue structure rather than of cell malignization.

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^☆: Reprint requests: James Fanning, DO, Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, Richard D. Ruppert Health Center, Toledo, OH 43614-5809.

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Residents’ Papers GynecologyGap junctional intercellular communication and connexin 43 expression in ovarian carcinoma☆

Abstract

Section snippets

Material and methods

Results

Comment

Adv Cancer Res

Cancer statistics, 1998 [published erratum appears in CA Cancer J Clin 1998;48:192]

CA Cancer J Clin

A simplified method to culture human ovarian surface epithelium

Lab Invest

The role of gap junctional intercellular communication in neoplasia

Ann Clin Lab Sci

Gap junctional intercellular communication and connexin 43 expression in human ovarian surface epithelial cells and ovarian carcinomas in vivo and in vitro

Carcinogenesis

Residents’ Papers Gynecology
Gap junctional intercellular communication and connexin 43 expression in ovarian carcinoma☆