Retroviral delivery of connexin genes to human breast tumor cells inhibits in vivo tumor growth by a mechanism that is independent of significant gap junctional intercellular communication.
The mechanism by which gap junction proteins, connexins, act as potent tumor suppressors remains poorly understood. In this study human breast tumor cells were found to exhibit diverse gap junction phenotypes including (a) undetectable Cx43 and no intercellular communication (HBL100); (b) low levels of Cx43 and sparse intercellular communication (MDA-MB-231); and (c) significant levels of Cx43 and moderate intercellular communication (Hs578T). Although retroviral delivery of Cx43 and Cx26 cDNAs to MDA-MB-231 cells did not achieve an expected substantial rescue of intercellular communication, overexpression of connexin genes did result in a dramatic suppression of tumor growth when connexin-expressing MDA-MB-231 cells were implanted into the mammary fat pad of nude mice. Subsequent immunolocalization studies on xenograph sections revealed only cytoplasmic stores of Cx43 and no detectable gap junctions. Moreover, DNA array and Western blot analysis demonstrated that overexpression of Cx43 or Cx26 in MDA-MB-231 cells down-regulated fibroblast growth factor receptor-3. Surprisingly, these results suggest that Cx43 and Cx26 induce their tumor-suppressing properties by a mechanism that is independent of significant gap junctional intercellular communication and possibly through the down-regulation of key genes involved in tumor growth. Moreover, our studies show that retroviruses are effective vehicles for delivering connexins to human breast tumor cells, facilitating potential gene therapy applications.
Qin
Hong
H
Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario N6A 5C1, Canada.
Shao
Qing
Q
Curtis
Heather
H
Galipeau
Jacques
J
Belliveau
Daniel J
DJ
Wang
Taiqi
T
Alaoui-Jamali
Moulay A
MA
Laird
Dale W
DW
D000818:Animals; D015153:Blotting, Western; D001943:Breast Neoplasms; D002450:Cell Communication; D000072259:Connexin 26; D018031:Connexin 43 / Q000235:genetics; D017630:Connexins / Q000235:genetics*; D018076:DNA, Complementary / Q000378:metabolism; D015536:Down-Regulation; D005346:Fibroblast Growth Factors / Q000378:metabolism; D017629:Gap Junctions / Q000502:physiology*; D015316:Genetic Therapy / Q000379:methods; D005822:Genetic Vectors; D006801:Humans; D007150:Immunohistochemistry; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D011485:Protein Binding; D012190:Retroviridae / Q000235:genetics*; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured
D018031:Connexin 43; D017630:Connexins; D018076:DNA, Complementary; C000607042:GJB2 protein, human; D000072259:Connexin 26; D005346:Fibroblast Growth Factors