Raihana Maqbool1, Rabiya Rashid1, Rehana Ismail1, Saif Niaz1, Nisar Ahmad Chowdri2, Mahboob Ul Hussain3. 1. Department of Biotechnology, University of Kashmir, Srinagar, 190006, India. 2. Department of General and Minimal Invasive Surgery, SKIMS, Srinagar, Soura, India. 3. Department of Biotechnology, University of Kashmir, Srinagar, 190006, India. mahboob@kashmiruniversity.ac.in.
Abstract
PURPOSE: Connexin 43 (Cx43) is a widely expressed gap junction protein. It can also regulate various gap-junction independent processes, including cellular proliferation. The latter regulatory functions have been attributed to its carboxy-terminal domain, CT-Cx43. CT-Cx43 has been found to be expressed independent of full-length Cx43 in various cell types. Its nuclear localization has additionally raised the possibility that it may regulate the expression of particular genes, including miRNAs, known play a role in the regulation of cellular proliferation. Here, we set out to uncover the molecular mechanism(s) underlying CT-Cx43 mediated gene (de-)regulation in human breast cancer. METHODS: Western blotting and quantitative real time PCR were carried to assess the expression of CT-Cx43 and miR-125b in a panel of 60 primary human breast cancer tissues and its paired normal adjacent tissues. In addition, CT-Cx43 was exogenously expressed in the breast cancer-derived cell line MCF-7 and its effect on the expression of miR-125b and its downstream target p53 were evaluated, as well as its effect on cellular proliferation and death using MTT and LDH assays, respectively. RESULTS: We found that CT-Cx43, but not full-length Cx43, was down-regulated in low grade human breast cancers. In addition, we found that the tumor suppressor protein p53 exhibited a decreased expression in the CT-Cx43 down-regulated samples. Interestingly, we found that miR-125b, a negative regulator of p53, exhibited an inverse expression relationship with CT-Cx43 in the breast cancer samples tested. This inverse relationship was confirmed by exogenous expression of CT-Cx43 in MCF-7 cells. In addition, we found that CT-Cx43 up-regulation and subsequent miR-125b down-regulation resulted in a decreased proliferation of MCF-7 cells. CONCLUSIONS: Our data suggest a mechanism by which CT-Cx43 may regulate cell proliferation. Targeting of CT-Cx43 and/or miR-125b may be instrumental for therapeutic intervention in human breast cancer.
PURPOSE:Connexin 43 (Cx43) is a widely expressed gap junction protein. It can also regulate various gap-junction independent processes, including cellular proliferation. The latter regulatory functions have been attributed to its carboxy-terminal domain, CT-Cx43. CT-Cx43 has been found to be expressed independent of full-length Cx43 in various cell types. Its nuclear localization has additionally raised the possibility that it may regulate the expression of particular genes, including miRNAs, known play a role in the regulation of cellular proliferation. Here, we set out to uncover the molecular mechanism(s) underlying CT-Cx43 mediated gene (de-)regulation in humanbreast cancer. METHODS: Western blotting and quantitative real time PCR were carried to assess the expression of CT-Cx43 and miR-125b in a panel of 60 primary humanbreast cancer tissues and its paired normal adjacent tissues. In addition, CT-Cx43 was exogenously expressed in the breast cancer-derived cell line MCF-7 and its effect on the expression of miR-125b and its downstream target p53 were evaluated, as well as its effect on cellular proliferation and death using MTT and LDH assays, respectively. RESULTS: We found that CT-Cx43, but not full-length Cx43, was down-regulated in low grade humanbreast cancers. In addition, we found that the tumor suppressor protein p53 exhibited a decreased expression in the CT-Cx43 down-regulated samples. Interestingly, we found that miR-125b, a negative regulator of p53, exhibited an inverse expression relationship with CT-Cx43 in the breast cancer samples tested. This inverse relationship was confirmed by exogenous expression of CT-Cx43 in MCF-7 cells. In addition, we found that CT-Cx43 up-regulation and subsequent miR-125b down-regulation resulted in a decreased proliferation of MCF-7 cells. CONCLUSIONS: Our data suggest a mechanism by which CT-Cx43 may regulate cell proliferation. Targeting of CT-Cx43 and/or miR-125b may be instrumental for therapeutic intervention in humanbreast cancer.
Entities:
Keywords:
Breast cancer; Connexin43; miR-125b; p53
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