Neoplastic phenotype of gap-junctional intercellular communication–deficient WB rat liver epithelial cells and its reversal by forced expression of connexin 32

Rae, Robert S.; Mehta, Parmender P.; Chang, Chia Cheng; Trosko, James E.; Ruch, Randall J.

doi:10.1002/(sici)1098-2744(199806)22:2<120::aid-mc7>3.0.co;2-q

Cited by 41 publications

(30 citation statements)

References 33 publications

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“…Furthermore, cells derived from the Cx gene knockout mice (Cx43 7/7 and Cx32 7/7 ) had a higher tendency for tumorigenesis compared with the wild type (Martyn et al, 1997;Temme et al, 1997). Moreover, transfection of various Cx genes into GJIC-de®cient tumor cells restored the normal cell growth (Mehta et al, 1991;Mesnil et al, 1995;Proulx et al, 1997;Statuto et al, 1997;Rae et al, 1998). However, the mechanisms, by which Cxs inhibit tumor cell proliferation, are still not well understood.…”

Section: Introductionmentioning

confidence: 99%

Connexin43 suppresses proliferation of osteosarcoma U2OS cells through post-transcriptional regulation of p27

et al. 2001

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Many lines of evidence indicate that connexin genes expressing gap junction (GJ) proteins inhibit tumor cell proliferation. However, the precise molecular mechanisms remain unclear. In this study, we show that overexpression of connexin43 (Cx43) suppressed proliferation of human osteosarcoma U2OS cells through inhibition of the cell cycle transition from G1 to S phase. This inhibition was attributed to a signi®cant accumulation of the hypophosphorylated retinoblastoma (Rb) protein, which was causally related to decreases in the kinase activities of cyclin-dependent kinases (CDKs) 2 and 4. Enforced Cx43 expression markedly increased the level of the CDK inhibitor p27. This increase resulted from an increased synthesis and a reduced degradation of the p27 proteins, but not in¯uence of the p27 mRNA. Moreover, we show that the Cx43-modulated GJ function was the main contributor to the elevation in p27 levels, in which cAMP was involved. These data suggest that Cx43 appears to inhibit proliferation of U2OS cells by increasing the levels of p27 proteins via post-transcriptional regulatory mechanisms. Oncogene (2001) 20, 4138 ± 4149.

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Section: Introductionmentioning

confidence: 99%

Connexin43 suppresses proliferation of osteosarcoma U2OS cells through post-transcriptional regulation of p27

et al. 2001

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“…Metastatic potential was also greater in mammary adenocarcinoma cells with low GJIC [Nicolson et al, 1988]. Growth in vitro and tumorigenicity were reduced when poorly communicating, neoplastic cells were transfected with connexin genes [Chen et al, 1995;Eghbali et al, 1991;Hirschi et al, 1996;Huang et al, 1998;Mehta et al, 1991;Mesnil et al, 1995;Rae et al, 1998;Zhu et al, 1991]. Conversely, reduction of GJIC by treating cells with connexin antisense DNA, transfection of dominant-negative connexin genes, or connexin gene deletion ("gene knockout") increased cell growth and neoplastic transformation [Goldberg et al, 1994;Omori and Yamasaki, 1998;Oyoyo et al, 1997;Ruch et al, 1995;Temme et al, 1997].…”

Section: Introductionmentioning

confidence: 99%

Growth inhibition in G1 and altered expression of cyclin D1 and p27kip-1after forced connexin expression in lung and liver carcinoma cells

et al. 2000

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Gap junctional intercellular communication (GJIC) and connexin expression are frequently decreased in neoplasia and may contribute to defective growth control and loss of differentiated functions. GJIC, in E9 mouse lung carcinoma cells and WB-aB1 neoplastic rat liver epithelial cells, was elevated by forced expression of the gap junction proteins, connexin43 (Cx43) and connexin32 (Cx32), respectively. Transfection of Cx43 into E9 cells increased fluorescent dye-coupling in the transfected clones, E9-2 and E9-3, to levels comparable to the nontransformed sibling cell line, E10, from which E9 cells originated. Transduction of Cx32 into WB-aB1 cells also increased dye-coupling in the clone, WB-a/32-10, to a level that was comparable to the nontransformed sibling cell line, WB-F344. The cell cycle distribution was also affected as a result of forced connexin expression. The percentage of cells in G(1)-phase increased and the percentage in S-phase decreased in E9-2 and WB-a/32-10 cells as compared to E9 and WB-aB1 cells. Concomitantly, these cells exhibited changes in G(1)-phase cell cycle regulators. E9-2 and WB-a/32-10 cells expressed significantly less cyclin D1 and more p27(kip-1) protein than E9 and WB-aB1 cells. Other growth-related properties (expression of platelet-derived growth factor receptor-beta, epidermal growth factor receptor, protein kinase C-alpha, protein kinase A regulatory subunit-Ialpha, and production of nitric oxide in response to a cocktail of pro-inflammatory cytokines) were minimally altered or unaffected. Thus, enhancement of connexin expression and GJIC in neoplastic mouse lung and rat liver epithelial cells restored G(1) growth control. This was associated with decreased expression of cyclin D1 and increased expression of p27(kip-1), but not with changes in other growth-related functions.

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“…Our results suggest, however, that the enhancement of HU toxicity in GJIC-proficient WB cells was not due to differences in Cx43 expression per se, its localization, or a non-GJIC mechanism. First, Cx43 protein content and plasma membrane localization are comparable in the cell lines we have used (Figure 1) [16] [17]. Second, oleamide which blocks GJIC, but does not affect expression or localization [8], reduced HU toxicity only in GJIC-proficient cells.…”

Section: Discussionmentioning

confidence: 99%

“…These cells do not exhibit GJIC by SL/DT assay, but express Cx43 in amounts comparable to WB-F344 cells; this protein is also localized to the plasma membrane (Figures 1(a)-(c)). In addition, GJIC-deficient WB-aB1 cells that were stably transduced with Gjb1 which encodes connexin 32 (Cx32) [17] were used. Two of the clones, WB-a/32-9 and WB-a/32-10, exhibit levels of dye-coupling similar to WB-F344 cells and express Cx32 (Figures 1(a)-(c)).…”

Section: Gjic and Connexin Expression In Wb Cell Linesmentioning

confidence: 99%

Gap Junctional Intercellular Communication Increases Cytotoxicity and Reduces Resistance to Hydroxyurea

Ruch¹,

Boucher²,

Gentry³

et al. 2014

JCT

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Background: Gap junctions enable small molecules to diffuse between adjacent cells and have been associated with greater cytotoxicity of radiation and anti-cancer drugs. We investigated whether this gap junctional intercellular communication (GJIC) affected the cytotoxicity of the classic ribonucleotide reductase (RR) inhibitor and anti-cancer agent, hydroxyurea (HU). Materials and Methods: We used GJIC-proficient and deficient, connexin 43-expressing WB rat liver epithelial cell lines. We compared HU toxicity by crystal violet assay, effects of the drug on deoxynucleotide pools by HPLC, and ability of GJIC to increase toxicity of HU-resistant cells through a bystander effect in co-culture experiments. Results: GJIC-proficient cells were three-to five-fold more sensitive (IC50 0.1 mM) to HU than GJIC-deficient derivatives (IC 50 0.3 -0.5 mM). This sensitivity depended upon GJIC because treatment of GJIC-proficient cells with the GJIC blocker oleamide decreased HU toxicity by approximately 60% -80% and restoration of GJIC in GJIC-deficient cells by stable transduction of connexin 32-encoding Gjb1 increased HU toxicity (IC 50 0.1 mM). The effects were not due to connexin expression per se or its localization since all cell lines expressed comparable quantities of connexin 43 that was localized to the plasma membrane. Also HU sensitivity was not related to differential effects on nucleotide metabolism in the cells. Thymidine triphosphate levels increased and deoxyadenosine triphosphate levels decreased similarly (15% -20%) in GJIC-proficient and deficient cells over 24 h of HU treatment. More importantly, when HU-resistant cells were co-cultured with sensitive cells, the resistant cells were killed only when GJIC was present. Conclusion: The data suggest that GJIC enhances cytotoxicity and decreases resistance to HU. These results may be important clinically if GJIC can be enhanced in drug-resistant cells.

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Neoplastic phenotype of gap-junctional intercellular communication–deficient WB rat liver epithelial cells and its reversal by forced expression of connexin 32

Cited by 41 publications

References 33 publications

Connexin43 suppresses proliferation of osteosarcoma U2OS cells through post-transcriptional regulation of p27

Connexin43 suppresses proliferation of osteosarcoma U2OS cells through post-transcriptional regulation of p27

Growth inhibition in G1 and altered expression of cyclin D1 and p27kip-1after forced connexin expression in lung and liver carcinoma cells

Gap Junctional Intercellular Communication Increases Cytotoxicity and Reduces Resistance to Hydroxyurea

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