The carboxy-terminal domain of connexin 43 (CT-Cx43) modulates the expression of p53 by altering miR-125b expression in low-grade human breast cancers

Raihana Maqbool; Rabiya Rashid; Rehana Ismail; Saif Niaz; Nisar Ahmad Chowdri; Mahboob Ul Hussain

doi:10.1007/s13402-015-0240-x

The carboxy-terminal domain of connexin 43 (CT-Cx43) modulates the expression of p53 by altering miR-125b expression in low-grade human breast cancers

Cell Oncol (Dordr). 2015 Dec;38(6):443-51. doi: 10.1007/s13402-015-0240-x. Epub 2015 Sep 3.

Authors

Raihana Maqbool¹, Rabiya Rashid¹, Rehana Ismail¹, Saif Niaz¹, Nisar Ahmad Chowdri², Mahboob Ul Hussain³

Affiliations

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.

PMID: 26335100
DOI: 10.1007/s13402-015-0240-x

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.

Keywords: Breast cancer; Connexin43; miR-125b; p53.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Blotting, Western
Breast Neoplasms / genetics
Breast Neoplasms / metabolism*
Breast Neoplasms / pathology
Connexin 43 / metabolism*
Female
Gene Expression Regulation, Neoplastic / physiology*
Humans
MCF-7 Cells
MicroRNAs / metabolism*
Neoplasm Grading
Real-Time Polymerase Chain Reaction
Transfection
Tumor Suppressor Protein p53 / biosynthesis*

Substances

Connexin 43
GJA1 protein, human
MIRN125 microRNA, human
MicroRNAs
TP53 protein, human
Tumor Suppressor Protein p53