title: An optical labeling-based proliferation assay system reveals the paracrine effect of interleukin-6 in breast cancer.
abstract: Proliferation analysis is one of the basic approaches to characterize various cell types. In conventional cell proliferation assays, the same sample cannot be observed over time, nor can a specific group within a heterogeneous population of cells, for example, cancerous cells, be analyzed separately. To overcome these limitations, we established an optical labeling-based proliferation assay system with the Kaede protein, whose fluorescence can be irreversibly photo converted from green to red by irradiation. After a single non-toxic photoconversion event, the intensity of red fluorescence in each cell is reduced by cell division. From this, we developed a simple method to quantify cell proliferation by monitoring reduction of red fluorescence over time. This study shows that the optical labeling-based proliferation assay is a viable novel method to analyze cell proliferation, and could enhance our understanding of mechanisms regulating cell proliferation machinery. We used this newly established system to analyze the functions of secreted interleukin-6 (IL-6) in cancer cell proliferation, which had not been fully characterized. Reduction in proliferation was observed following IL-6 knockdown. However, after co-culturing with IL-6-expressing cells, the proliferation of Kaede-labeled IL-6-knockdown cells was restored. These data indicate that in basal-like breast cancer cells, IL-6 exhibits a paracrine effect to positively regulate cell proliferation. Our results thus demonstrate that cancer cells can secrete signaling molecules, such as IL-6, to support the proliferation of other cancer cells.
authors.affiliation: Department of Breast Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan. Electronic address: junji-itou@umin.ac.jp.
authors.forename: Junji
authors.initials: J
authors.lastname: Itou
authors.affiliation: Department of Breast Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.
authors.forename: Sunao
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: Department of Breast Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Sato
authors.affiliation: Department of Genetics, Cell Biology and Development, University of MN, 321 Church Street SE, Minneapolis, MN 55455, USA; Stem Cell Institute, University of MN, 321 Church Street SE, Minneapolis, MN 55455, USA.
authors.forename: Ryutaro
authors.initials: R
authors.lastname: Akiyama
authors.affiliation: Department of Genetics, Cell Biology and Development, University of MN, 321 Church Street SE, Minneapolis, MN 55455, USA; Stem Cell Institute, University of MN, 321 Church Street SE, Minneapolis, MN 55455, USA; Developmental Biology Center, University of MN, 321 Church Street SE, Minneapolis, MN 55455, USA; Lillehei Heart Institute, University of MN, 321 Church Street SE, Minneapolis, MN 55455, USA.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Kawakami
authors.affiliation: Department of Breast Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Toi
mesh_terms: D001943:Breast Neoplasms / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000502:physiology*; D008164:Luminescent Proteins; D019899:Paracrine Communication / Q000502:physiology
chemical_list: C508600:IL6 protein, human; D015850:Interleukin-6; C513582:Kaede protein, Trachyphyllia geoffroyi; D008164:Luminescent Proteins
keywords: Breast cancer; Interleukin-6; Optical labeling; Paracrine effect; Proliferation; The OPA system