Identification of transforming activity of free fatty acid receptor 2 by retroviral expression screening.
Gallbladder cancer (GBC) is a highly fatal malignancy in humans. Genetic alterations in KRAS or TP53 as well as overexpression of ERBB2 have been shown to contribute to the development of certain types of GBC. However, many cases of GBC do not harbor such genetic changes, with other transforming events awaiting discovery. We here tried to identify novel cancer-promoting genes in GBC, with the use of a retroviral cDNA expression library. A retroviral cDNA expression library was constructed from a surgically resected clinical specimen of GBC, and was used to infect 3T3 fibroblasts in a focus formation assay. cDNA incorporated into the transformed foci was rescued by PCR. One such cDNA was found to encode free fatty acid receptor 2 (FFAR2), a G protein-coupled receptor for short-chain fatty acids. The oncogenic potential of FFAR2 was confirmed both in vitro with the focus formation assay and by evaluation of cell growth in soft agar as well as in vivo with a tumorigenicity assay in nude mice. The isolated FFAR2 cDNA had no sequence alterations, suggesting that upregulation of FFAR2 expression may contribute to malignant transformation. Indeed, all of quantitative RT-PCR, in situ hybridization, and immunohistochemical analyses showed that the amount of FFAR2 mRNA and its protein product was increased in digestive tract cancer specimens. Furthermore, short-chain fatty acids potentiated the mitogenic action of FFAR2 in 3T3 cells. Our data thus, for the first time, implicate FFAR2 in carcinogenesis of the digestive tract.
Division of Functional Genomics, Jichi Medical University, Tochigi, Japan.
Hisashi
H
Hatanaka
Mamiko
M
Tsukui
Shuji
S
Takada
Kentaro
K
Kurashina
Young Lim
YL
Choi
Manabu
M
Soda
Yoshihiro
Y
Yamashita
Hidenori
H
Haruta
Toru
T
Hamada
Toshihide
T
Ueno
Kiichi
K
Tamada
Yoshinori
Y
Hosoya
Naohiro
N
Sata
Yoshikazu
Y
Yasuda
Hideo
H
Nagai
Kentaro
K
Sugano
Hiroyuki
H
Mano
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002471:Cell Transformation, Neoplastic; D005706:Gallbladder Neoplasms / Q000209:etiology*; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008875:Middle Aged; D008969:Molecular Sequence Data; D011956:Receptors, Cell Surface / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D012190:Retroviridae / Q000235:genetics*
D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C473103:FFAR2 protein, human; C506481:Ffar2 protein, mouse