Characterization of PROX1, a novel tumor suppressor gene.

2007 Fiscal Year Final Research Report Summary

• Project/Area Number: 18590730
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Gastroenterology
• Research Institution: Kyoto University
• Principal Investigator: TAKAHASHI Meiko Kyoto University, Center for Genomic Medicine, Assistant Professor (20372592)
• Project Period (FY): 2006 – 2007
• Keywords: PROX1 / Tumor suppressor gene / RNA editing

Research Abstract

Characterization of PROX1 in HCC
To address the possibility that Prox1 may be involved in the tumorigenesis of hepatocellular carcinoma (HCC), human clinical samples were analyzed. There was a significant correlation between Prox1 expression and the differentiation scores of the tumors, and low expression of Prox1 in tumors was closely associated with a poor prognosis. The specific knockdown of Prox1 by RNA interference strongly accelerated in vitro cell growth, whereas the overexpression of Prox1 greatly suppressed the growth. Our results suggest that Prox1 is involved in the differentiation and progression of HCC, and thus it may be a candidate for the development of novel diagnostic and therapeutic strategies for HCC.
Functional Analyses of PROX1
The importance of genetic mutations in carcinogenesis has been recognized, and it has been proposed that aberrant mutation of mRNA may represent a novel oncogenic principle. Expression of Prox1 was reduced in pancreatic cancers, and the extent of reduction correlated with progression of tumor differentiation. A-to-G base change was found in prox1 cDNA taken from human cancer cells, but not in corresponding genomic DNA. We mapped four common mutation sites in prox1 gene, and the same four sites were mutated in human clinical samples from several cancers. Tetracycline-induced wild-type (wt) Prox1 in tumor cells inhibited transforming activity and cellular proliferation. However, mutant Prox1 with the four common sites altered from A to G lost these inhibitory functions. In mice, xenografts of tumor cells with tetracycline-induced wt-Prox1 formed tumor masses significantly more slowly than control tumors, whereas mutated Prox1 had no effect. These findings may point to a pivotal role of the RNA mutation of prox1 gene in the pathogenesis of human cancer progression.
RNA mutation detection system
We applied the shifted termination assay (STA) for detection of an A-to-I RNA mutation (R334G) in prox1, and demonstrated that the STA method can be used to identify not only genomic mutations but also RNA mutations more effectively compared to sequencing. By means of STA, we found prox1 R334G RNA mutations but not genomic DNA mutations in 4 of 8 cases of esophageal cancers. This method can help us to detect RNA mutation effectively and progress research of a potential oncogenic principle.

Research Products

• [Journal Article] RNA mutations of prox1 detected in human esophageal cancer cells by the shifted termination assay. (2007)
  • Author(s): Yoshimoto T, Takahashi M, Nagayama S, Watanabe G, Shimada Y, Sakasi Y, Kubo H.
  • Journal Title: Biochem Biophys Res Commun 359(2) Pages: 258-262
  • Description: 「研究成果報告書概要(和文)」より
  • Peer Reviewed
• [Journal Article] Immunohistochemical detection of the lymphatic marker podoplanin in diverse types of human cancer cells using a novel antibody. (2007)
  • Author(s): Kono T, Shimoda M, Takahashi M, Matsumoto K, Yoshimoto T, Mizutani M, Tabata C, Okoshi K, Wada H, Kubo H.
  • Journal Title: Int J Oncol 31(3) Pages: 501-508
  • Description: 「研究成果報告書概要(和文)」より
  • Peer Reviewed
• [Journal Article] Thalidomide prevents bleomycin-induced pulmonary fibrosis in mice. (2007)
  • Author(s): Tabata C, Tabata R, Kadokawa Y, Hisamori S, Takahashi M, Mishima M, Nakano T, Kubo H.
  • Journal Title: J Immunol. 179(1) Pages: 708-714
  • Description: 「研究成果報告書概要(和文)」より
  • Peer Reviewed
• [Journal Article] RNA mutations of prox1 detected in human esophageal cancer cells by the shifted termination assay (2007)
  • Author(s): Yoshimoto, T., Takahashi, M., Nagayama, S., Watanabe, G., Shimada, Y., Sakasi, Y., Kubo, H
  • Journal Title: Biochem Biophys Res Commun 359(2) Pages: 258-262
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Immunohistochemical detection of the lymphatic marker podoplanin in diverse types of human cancer cells using a novel antibody (2007)
  • Author(s): Kono, T., Shimoda, M., Takahashi, M., Matsumoto, K., Yoshimoto, T., Mizutani, M., Tabata, C., Okoshi, K., Wada, H., Kubo, H
  • Journal Title: Int J Oncol 31(3) Pages: 501-508
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Thalidomide prevents bleomycin-induced pulmonary fibrosis in mice (2007)
  • Author(s): Tabata, C., Tabata, R., Kadokawa, Y., Hisamori, S., Takahashi, M., Mishima, M., Nakano, T., Kubo, H
  • Journal Title: J Immunol 179(1) Pages: 708-714
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] A homeobox protein proxl is involved in the differentiation, proliferation and prognosis in hepatocellular carcinoma. (2006)
  • Author(s): Shimoda M, Takahashi M, Yoshimoto T, Kono T, Ikai I, Kubo H.
  • Journal Title: Clin Can Res 12(20) Pages: 6005-6011
  • Description: 「研究成果報告書概要(和文)」より
  • Peer Reviewed
• [Journal Article] Loss of function of the candidate tumor suppressor proxl by RNA mutation in human cancer cells. (2006)
  • Author(s): Takahashi M, Yoshimoto T, Shimoda M, Kono T, Koisumi M, Yazumi S, Shimada Y, Doi R, Chiba T, Kubo H.
  • Journal Title: Neoplasia 8(12) Pages: 1003-1010
  • Description: 「研究成果報告書概要(和文)」より
  • Peer Reviewed
• [Journal Article] Differentiation of lymphatic endothelial cells from Embryonic Stem cells on OP9 stromal cells. (2006)
  • Author(s): Kono T, Kubo H, Shimazu C, Ueda Y, Takahashi M, Yanagi K, Fujita N, Tsuruo T, Wada H, Yamashita JK.
  • Journal Title: Arterioscler Thromb Vasc Biol Sep;26(9) Pages: 2070-2076
  • Description: 「研究成果報告書概要(和文)」より
  • Peer Reviewed
• [Journal Article] A homeobox protein prox1 is involved in the differentiation, proliferation and prognosis in hepatocellular carcinoma (2006)
  • Author(s): Shimoda, M., Takahashi, M., Yoshimoto, T., Kono, T., Ikai, I., Kubo, H
  • Journal Title: Clin Can Res 12(20) Pages: 6005-6011
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Loss of function of the candidate tumor suppressor prox1 by RNA mutation in human cancer cells (2006)
  • Author(s): Takahashi, M., Yoshimoto, T., Shimoda, M., Kono, T., Koisumi, M., Yazumi, S., Shimada, Y., Doi, R., Chiba, T., Kubo, H
  • Journal Title: Neoplasia 8(12) Pages: 1003-1010
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Differentiation of lymphatic endothelial cells from Embryonic Stem cells on OP9 stromal cells (2006)
  • Author(s): Kono, T., Kubo, H., Shimazu, C., Ueda, Y., Takahashi, M., Yanagi, K., Fujita, N., Tsuruo, T., Wada, H., Yamashita, JK
  • Journal Title: Arterioscler Thromb Vase Biol 26(9) Pages: 2070-2076
  • Description: 「研究成果報告書概要(欧文)」より
• [Presentation] A-to-I RNA editing of a homeobox gene in a subset of human cancer cells (2006)
  • Author(s): Takahashi M, Yoshimoto T, Kubo H.
  • Organizer: 11th International Congress f Metastasis Research Society jointed with 15th Annual Meeting of Japanese Association for Metastasis Research
  • Place of Presentation: Tokushima, Japan
  • Year and Date: 2006-09-05
  • Description: 「研究成果報告書概要(和文)」より
• [Presentation] A-to-I editing of a homeobox gene in a subset of human cancer cells (2006)
  • Author(s): Takahashi, M., Yoshimoto, T., Kubo, H
  • Organizer: 11th International Congress of Metastasis Research Society jointed with 16th Annual Meeting of Japanese Association for Metastasis Research
  • Place of Presentation: Tokushima, Japan
  • Year and Date: 2006-09-05
  • Description: 「研究成果報告書概要(欧文)」より