title: Cytoplasmic accumulation of connexin32 expands cancer stem cell population in human HuH7 hepatoma cells by enhancing its self-renewal.
abstract: Although the connexin32 (Cx32)-mediated gap junction is abolished in hepatocellular carcinoma (HCC), the expression of cytoplasmic Cx32 tends to increase in correspondence with the grade of malignancy. Establishing a Tet-off expression system in human nonmetastatic HuH7 HCC cells where cytoplasmic Cx32 was overexpressed by doxycycline (Dox) withdrawal, we previously demonstrated that overexpression of cytoplasmic Cx32 made HuH7 cells metastatic in mice. In our study, hypothesizing that the cytoplasmic Cx32-induced metastasis may involve expansion of the cancer stem cell (CSC) population, we examined whether cytoplasmic Cx32 controlled the size of the side population (SP) in HuH7 Tet-off Cx32 cells. Fluorescence-activated cell sorting revealed that SP was expanded in a Dox-free medium compared with a Dox-supplemented one. Although cytoplasmic Cx32 did not block maturation from SP to non-SP, purified SP reconstituted a larger SP fraction in the Dox-free medium than in the Dox-supplemented one. Furthermore, although SP from HuH7 Tet-off mock cells formed a similar number of CSC spheres of a similar size whether with or without Dox, SP from HuH7 Tet-off Cx32 cells developed a greater number of larger CSC spheres in the Dox-free medium than in the Dox-supplemented one. Taken together, these results suggest that accumulation of cytoplasmic Cx32 should enhance self-renewal of CSC to expand the CSC population in HCC.
authors.affiliation: Department of Molecular and Tumour Pathology, Akita University Graduate School of Medicine, Akita, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Kawasaki
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Omori
authors.forename: Qingchang
authors.initials: Q
authors.lastname: Li
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nishikawa
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Yoshioka
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yoshida
authors.forename: Kazuo
authors.initials: K
authors.lastname: Ishikawa
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Enomoto
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D004318:Doxycycline / Q000494:pharmacology; D005434:Flow Cytometry; D019084:Fluorescent Antibody Technique, Indirect; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D015151:Immunoblotting; D008114:Liver Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D016513:Mice, SCID; D009362:Neoplasm Metastasis; D014411:Neoplastic Stem Cells / Q000378:metabolism* / Q000473:pathology; D013752:Tetracycline / Q000494:pharmacology; D014183:Transplantation, Heterologous; D000097002:Gap Junction beta-1 Protein
chemical_list: D000900:Anti-Bacterial Agents; D017630:Connexins; D004318:Doxycycline; D013752:Tetracycline; D000097002:Gap Junction beta-1 Protein