Molecular Diagnostics

BJC Open article

British Journal of Cancer (2009) 101, 691–698. doi:10.1038/sj.bjc.6605202 www.bjcancer.com
Published online 11 August 2009

Identification of retinoic acid-regulated nuclear matrix-associated protein as a novel regulator of gastric cancer

J Li1, E K O Ng1, Y P Ng2, C Y P Wong1, J Yu1, H Jin1, V Y Y Cheng1, M Y Y Go1, P K F Cheung1, M P A Ebert3, J Tong4, K F To4, F K L Chan1, J J Y Sung1, N Y Ip2 and W K Leung1

  1. 1Institute of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, China
  2. 2Department of Biochemistry, Hong Kong University of Science and Technology, Hong Kong, China
  3. 3Department of Medicine II, Technical University of Munich, Munich, Germany
  4. 4Department of Anatomical and Cellular Pathology, State Key Laboratory in Oncology in South China, The Chinese University of Hong Kong, Hong Kong, China

Correspondence: Dr WK Leung, Department of Medicine and Therapeutics, Prince of Wales Hospital, Shatin, Hong Kong, China. E-mail: dr_wkleung@alumni.cuhk.net

Received 18 February 2009; Revised 18 June 2009; Accepted 30 June 2009

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Abstract

Background: Retinoic acid-regulated nuclear matrix-associated protein (RAMP) is a WD40 repeat-containing protein that is involved in various biological functions, but little is known about its role in human cancer. This study aims to delineate the oncogenic role of RAMP in gastric carcinogenesis.

Methods: RAMP expression was examined by real-time quantitative RT-PCR, immunohistochemistry and western blotting. Inhibition of RAMP expression was performed by siRNA-mediated knockdown. The functional effects of RAMP on cell kinetics were measured by cell viability assay, colony formation assay and flow cytometry. Cell lines stably expressing RAMP were established to investigate the oncogenic effects of RAMP in vitro.

Results: Ramp was readily expressed in all seven gastric cancer cell lines and was significantly increased in human gastric cancer tissues when compared with their adjacent non-cancerous tissues (P<0.001). In keeping with this, expression of RAMP protein was higher in gastric cancer tissues compared with their adjacent non-cancerous tissues, whereas moderate protein expression were noted in intestinal metaplasia. Knockdown of RAMP in gastric cancer cells significantly reduced cell proliferation (P<0.01) and soft agar colony formation (P<0.001), but induced apoptosis and G2/M arrest. In additional, knockdown RAMP induced cell apoptosis is dependent on functional accumulation of p53 and p21 and induction of cleaved caspases-9, caspases-3 and PARP. Strikingly, overexpression of RAMP promoted anchorage-independent cell growth in soft agar.

Conclusion: Our findings demonstrate that RAMP plays an oncogenic role in gastric carcinogenesis. Inhibition of RAMP may be a promising approach for gastric cancer therapy.

Keywords:

p53; p21; L2DTL; oncogene; tumourigenesis; DTL/RAMP

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