2697

GJA1

gap junction protein, alpha 1, 43kDa;GJA1;gap junction protein, alpha 1, 43kDa

connexin 43|connexin-43|gap junction 43 kDa heart protein|gap junction alpha-1 protein

6q22.31

protein-coding

Emerging evidence suggests that gap junctional intercellular communication (GJIC) and expression of connexins (Cx) contribute to the metastatic potential of breast cancer cells. To more directly address this, an aggressive bone metastasis breast cancer cell line, MDA-MET (MET), was stably transfected with human Cx43 cDNA (MET/Cx43(+)). Focusing on clone 28 of MET/Cx43(+), we demonstrated that GJIC, Cx43 protein and Cx43 mRNA were significantly increased in MET/Cx43(+) cells relative to MET, the plasmid control for the Cx43 transfectants (MET/HY) and a metastatic breast cancer cell that is less metastatic to bone than MET, MDA-MB-231. Cx26 mRNA was also increased in MET/Cx43(+ )clone 28 cells while mRNA for Cx32, Cx37, Cx40 and Cx45 were not detected in any of the breast cancer cell lines examined. MET/Cx43(+ )clone 28 invasiveness was decreased by 33% relative to MET/HY, while their ability to migrate was unchanged. The ability of MET/Cx43(+ )clone 28 cells to adhere to hFOB and HUV-EC-C cells was decreased approximately 30% and 70%, respectively, relative to MET and MET/HY. E-cadherin and N-cadherin proteins were not detected in MET, MDA-MB-231, MET/Cx43(+ )clone 28 and MET/HY cells. However, OB-cadherin protein levels were decreased approximately 43% in MET/Cx43(+ )clone 28 relative to MET/HY cells. These findings suggest that GJIC and Cx43 expression contribute to breast cancer cell adhesion and migration, possibly through a mechanism involving OB-cadherin, and these changes in turn regulate the metastatic potential of breast cancer cells, especially to bone.

Recently the concept that gap junctions play a role in cancer cell metastasis has emerged. However, the mechanism by which this might occur is unknown. To examine this issue a metastatic breast cancer cell line, MDA-MB-435, was stably transfected with human Cx43 cDNA. Four clones of 435 transfectants (435/Cx43(+) c1, c6, c8, c14) and two clones of plasmid control (435/hy) were isolated and examined in this study. We found that expressing Cx43 in MDA-MB-435 cells decreased their expression of Cx32 but did not affect gap junctional intercellular communication, migration or invasion through Matrigel((R)). However, forced expression of Cx43 decreased the growth of MDA-MB-435 cells, decreased expression of N-cadherin, which is frequently associated with an aggressive phenotype, and increased MDA-MB-435 sensitivity to apoptosis. More importantly, there were fewer lung metastases in mice injected with 435/Cx43(+) cells relative to mice injected with 435/hy. These results suggest that expressing Cx43 in breast cancer cells decreases their metastatic potential through a mechanism independent of gap junctional communication but, rather, related to N-cadherin expression and apoptosis.

OBJECTIVE: The aim of this study was to investigate the expression of connexin (Cx) and the function of gap junction intercellular communication (GJIC) in the carcinogenesis, progression and metastasis of gastric cancers. METHODS: Immunohistochemistry was used to detect the expression of Cx32 and Cx43 proteins in tissue samples. Indirect immunofluorescence assay was used to investigate the expression of Cx32 and Cx43 proteins in several gastric cancer lines of various differentiation grades. The expression of Cx43 in samples of gastric cancer tissue, adjacent normal tissue and in the gastric cancer cell lines of various differentiation grades was detected by Western blot. Scrape-loading dye transfer (SLDT) technique was used to detect the function of gap junction intercellular communication (GJIC) in the various cell lines. RESULTS: In the normal gastric mucosa the expression rates of both Cx32 and Cx43 were 100%. In gastric cancers, the expression rates of Cx32 andCx43 were 49.5% (55/111) and 39.6% (44/111), respectively. There was a significant difference between their expression in normal and cancer tissues (P < 0.05). Age of the patients was not significantly correlated with the expression level of Cx32 and Cx43 (P > 0.05). Cx43 expression was significantly associated with the TMN stage, histological type, depth of infiltration and distant metastasis (P < 0.05), but Cx32 expression was not significantly correlated with depth of infiltration ( P > 0.05). In the cancer cell lines, a positive expression of Cx32 and Cx43 was detected in transfected human stomach mucosal cell line (CES-1) and human well differentiated stomach cancer cell line (N87), but negative in the poorly differentiated stomach cancer cell line (BGC-823) at all. Both Cx32 and Cx43 expression rates were 100% in the cell line GES-1. Cx32 expression rate was 49.0% and Cx43 expression rate was 55.0% in the cell line N87. But in the poorly differentiated cancer cell line BGC-823 both Cx32 and Cx43 expression was negative. GJIC function detection showed: GES-1 showed well GIJC function but no GIJC function in the cell lines N87 and BGC-823. The intensity of fluorescence was gradually decreasing from GES-1 cells to N87 cells and almost no fluorescence in BGC-823 cells. Western blotting showed that Cx43 expression in normal tissue was higher than that in gastric cancer tissue, and in the cell lines GES-1, N87 and BGC-823, the bands seemed decreasing progressively. There was very low expression in BGC-823 cells. CONCLUSION: The decreasing expression of connexin Cx32 and Cx43 is obviously correlated with the occurrence, development and metastatic potential of stomach cancers.

Connexin 43(Cx43) and E-cadherin are concurrently expressed in many tumors and were ever classified as tumor suppressors in primary tumors (PT), whereas recent studies showed that these two proteins played specific roles in tumor metastasis. The aim of our study is to determine the expression of Cx43 and E-cadherin in primary gastric tumors (PTs) and matched metastatic lymph nodes (MLNs) and to explore the clinical and pathological implications of expression of these proteins. Immunohistochemical assay was conducted to detect the expression of Cx43 and E-cadherin in PTs and MLNs, and the clinical and pathological implications were analyzed by statistical methods. In PTs, the expression of Cx43 and E-cadherin was significantly reduced, compared to adjacent normal tissues (P < 0.01). The expression of Cx43 and E-cadherin was significantly increased in MLNs compared with PTs (P < 0.01 and P < 0.01, for Cx43 and E-cadherin, respectively), and some Cx43 and E-cadherin-negative PTs developed Cx43 and E-cadherin-positive MLNs. Furthermore, reduced expression of both Cx43 and E-cadherin significantly correlated with poor differentiation, advanced TNM stage, and lymph note metastasis of gastric cancers. Cx43 and E-cadherin expression significantly correlated with each other. We concluded that concurrent reduction in Cx43 and E-cadherin may contribute to the occurrence of gastric cancer. However, concurrent increased expression of Cx43 and E-cadherin may contribute to the efficient metastasis of gastric cancer to the lymph nodes.

OBJECTIVE: To examine the association of connexin 43 (Cx43) in the intraperitoneal free gastric cancer cells and clinicopathological characteristics. METHODS: Immunohistochemistry and immunofluorescence staining were used to detect connexin 43 in 75 paraffin-embedded gastric cancer tissues, matched paracancerous tissue, and intraperitoneal free gastric cancer cells. RESULTS: The positive rates of Cx43 expression were 33.3% (25/75) in gastric cancer tissue specimens and 100% (75/75) in matched paracancerous tissue (P<0.01). The positive detection rate of free cancer cells in peritoneal lavage was 38.6% (29/75) and the positive rate of Cx43 in peritoneal free gastric cancer cells was 72.4% (21/29), which was significantly higher than that in gastric cancer tissue specimens (P<0.01). Significant association was observed of Cx43 expression of free gastric cancer cells with tumor infiltration and histological type (P<0.05). CONCLUSION: Cx43 gene may be involved in the mechanism of peritoneal metastasis of gastric cancer.

The process of peritoneal metastasis involves the diapedesis of intra-abdominal exfoliated gastric cancer cells through the mesothelial cell monolayers; however, the related molecular mechanisms for this process are still unclear. Heterocellular gap-junctional intercellular communication (GJIC) between gastric cancer cells and mesothelial cells may play an active role during diapedesis. In this study we detected the expression of connexin 43 (Cx43) in primary gastric cancer tissues, intra-abdominal exfoliated cancer cells, and matched metastatic peritoneal tissues. We found that the expression of Cx43 in primary gastric cancer tissues was significantly decreased; the intra-abdominal exfoliated cancer cells and matched metastatic peritoneal tissues exhibited increasing expression compared with primary gastric cancer tissues. BGC-823 and SGC-7901 human gastric cancer cells were engineered to express Cx43 or Cx43T154A (a mutant protein that only couples gap junctions but provides no intercellular communication) and were co-cultured with human peritoneal mesothelial cells (HPMCs). Heterocellular GJIC and diapedesis through HPMC monolayers on matrigel-coated coverslips were investigated. We found that BGC-823 and SGC-7901 gastric cancer cells expressing Cx43 formed functional heterocellular gap junctions with HPMC monolayers within one hour. A significant increase in diapedesis was observed in engineered Cx43-expressing cells compared with Cx43T154A and control group cells, which suggested that the observed upregulation of diapedesis in Cx43-expressing cells required heterocellular GJIC. Further study revealed that the gastric cancer cells transmigrated through the intercellular space between the mesothelial cells via a paracellular route. Our results suggest that the abnormal expression of Cx43 plays an essential role in peritoneal metastasis and that Cx43-mediated heterocellular GJIC between gastric cancer cells and mesothelial cells may be an important regulatory step during metastasis. Finally, we observed that the diapedesis of exfoliated gastric cancer cells through mesothelial barriers is a viable route of paracellular migration.

BACKGROUND: We studied the relationships among Cx43, CD105, and VEGF in specimens of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) with different serum AFP levels with respect to recurrence and metastasis. METHODS: expressions of Cx43, CD105, and VEGF in 234 HCC tissue specimens were examined using tissue microarray and immunohistochemistry. Cx43 mRNA expression was examined in 38 frozen HCC specimens using RT-PCR. Correlations between these expressions and tumor recurrence, metastasis, and prognosis were analyzed using Kaplan-Meier and Cox regression analyses. RESULTS: Cx43 expression correlated with early tumor recurrence (P = 0.001), disease-free survival (P = 0.026), and overall survival (P = 0.000) in patients with serum AFP < 400 ng/ml, but not in those with serum AFP >/= 400 mug/L. Cx43 expression is an independent predictor of later recurrence and longer overall survival and is inversely correlated with expression of CD105 and VEGF (P = 0.018 and 0.023, respectively), histological differentiation (P = 0.002), vessel tumor embolism (P = 0.029), and focal number (P = 0.017). Immunohistochemistry showed that Cx43 expression in patients with low AFP was lower in patients with distant metastases than in those with no metastasis or those with liver metastasis. Patients with early recurrence expressed less Cx43 mRNA than did those with no recurrence (chi2 = 9.827, P = 0.002). CONCLUSIONS: Cx43 expression can delay early HCC recurrence, metastasis, and poor prognosis after radical hepatectomy in patients with HBV-related HCC and low AFP.

Although connexin has been recognized as a tumor suppressor in many types of cancer, the underlying mechanisms are poorly understood. We have previously shown that transfection of connexin43 (Cx43) cDNA retarded the growth of a highly metastatic human pulmonary giant cell carcinoma cell line, PG, both in vitro and in vivo. Here, we further demonstrate that the metastasis and invasion, but not the migration, of PG cells are also inhibited following Cx43 transfection. The diminishment of metastasis and invasion is associated with down-regulation of genes including MMP-2, S100A, LAMA4, and HDAC10, as well as up-regulation of genes such as MTSS1 and FSTL1 as revealed by gene chip analysis. Interestingly, the suppression effects of Cx43 are related to secreted factor(s), which are blocked by FSTL1 antibody treatment in a dose-dependent manner. Furthermore, the FSTL1 promoter was shown to be associated with acetylated histones H3 and H4 upon Cx43 transfection. These data suggest that Cx43 inhibits the invasion and metastasis of PG cells by modulating the secretion of FSTL1, which is regulated by histone acetylation. Cx43 may act as a "histone deacetylase inhibitor" to modulate gene expression and subsequent cellular functions in PG cells.

Protease-activated receptor-1 (PAR-1) is a key player in melanoma metastasis with higher expression seen in metastatic melanoma cell lines and tissue specimens. cDNA microarray and Western blot analyses reveal that the gap junctional intracellular communication molecule connexin 43 (Cx-43), known to be involved in tumor cell diapedesis and attachment to endothelial cells, is significantly decreased after PAR-1 silencing in metastatic melanoma cell lines. Furthermore, Cx-43 promoter activity was significantly inhibited in PAR-1-silenced cells, suggesting that PAR-1 regulates Cx-43 at the transcriptional level. Chromatin immunoprecipitation studies showed a reduction in the binding of SP-1 and AP-1 transcription factors to the promoter of Cx-43. Both transcription factors have been shown previously to be required for maximal Cx-43 promoter activity. These results were corroborated by mutating the AP-1 and SP-1 binding sites resulting in decreased Cx-43 promoter activity in PAR-1-positive cells. Moreover, as Cx-43 has been shown to facilitate arrest of circulating tumor cells at the vascular endothelium, melanoma cell attachment to endothelial cells was significantly decreased in PAR-1-silenced cells, with this effect being abrogated after PAR-1 rescue. Herein, we report that up-regulation of PAR-1 expression, seen in melanoma progression, mediates high levels of Cx-43 expression. As both SP-1 and AP-1 transcription factors act as positive regulators of Cx-43, our data provide a novel mechanism for the regulation of Cx-43 expression by PAR-1. Indeed, Cx-43 expression was restored following PAR-1 rescue in PAR-1-silenced cells. Taken together, our data support the tumor promoting function of Cx-43 in melanoma.

AIM: Connexin 43 (Cx43) and E-cadherin are important biomarkers related with cancer. Their expression at protein and mRNA levels was here investigated in 50 primary lung carcinoma tissues and 20 samples of adjacent normal tissue of Chinese patients with non-small cell lung cancer (NSCLC). METHODS: Protein and mRNA expression were evaluated by ABC immunohistochemistry and RT-PCR. RESULTS: (1) The positive expression rates of Cx43 and E-cadherin protein were higher in the adjacent normal tissues than those in the primary lung carcinoma tissues; (2) the positive expression rates of Cx43 and E-cadherin protein decreased with NSCLC progression; (3) the expression of E-cadherin protein was not related with the pathological type of NSCLC; and (4) the relative quantity of the Cx43 or E-cadherin mRNA expression was correlated with the the histological type, clinical stage, cancer cell differentiation and the lymph node metastasis. CONCLUSION: The data suggested that the Cx43 and E-cadherin are reduced with NSCLC progression, and might be important biomarkers for judging the metastasis and prognosis.