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Open Access Research article

Identification of Makorin 1 as a novel SEREX antigen of esophageal squamous cell carcinoma

Hideaki Shimada1, Tooru Shiratori2, Mari Yasuraoka3, Akiko Kagaya23, Mari Kuboshima23, Fumio Nomura4, Masaki Takiguchi3, Takenori Ochiai25, Hisahiro Matsubara2 and Takaki Hiwasa3*

Author Affiliations

1 Department of Gastroenterological Surgery, Chiba Cancer Center, Chiba, Japan

2 Department of Frontier Surgery, Chiba University, Graduate School of Medicine, Chiba, Japan

3 Department of Biochemistry and Genetics, Chiba University, Graduate School of Medicine, Chiba, Japan

4 Department of Molecular Diagnosis, Chiba University, Graduate School of Medicine, Chiba, Japan

5 Gastroenterological Center, San-Ai Memorial Hospital, Chiba, Japan

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BMC Cancer 2009, 9:232  doi:10.1186/1471-2407-9-232

Published: 15 July 2009

Abstract

Background

Esophageal squamous cell carcinoma (SCC) represents one of the most malignant tumors. To improve the poor prognosis, it is necessary to diagnose esophageal SCC at early stages using new tumor markers. SEREX (serological identification of antigens by recombinant cDNA expression cloning) is suitable for large-scale screening of tumor antigens and has been applied for various types of human tumors.

Methods

Tumor markers of esophageal squamous cell carcinoma (SCC) were screened by SEREX method. The presence of serum anti-makorin 1 (MKRN1) antibodies (s-MKRN1-Abs) was examined by Western blotting using bacterially expressed MKRN1 protein. The expression levels of MKRN1 mRNA in tissues were examined by RT-PCR. The biological activity of MKRN1 was examined by transfection of ras-NIH3T3 mouse fibroblasts with MKRN1 cDNA. Major ubiquitinated proteins in MKRN1-transfected cells were identified by immunoprecipitation with anti-ubiquitin antibody followed by mass spectrometry.

Results

MKRN1 was identified as a novel SEREX antigen of esophageal SCC. Although a total of 18 (25%) of 73 patients with esophageal SCC had s-MKRN1-Abs, none of the 43 healthy donors had a detectable level of s-MKRN1-Abs. There was no correlation between the presence of s-MKRN1-Abs and clinicopathological variables other than histological grading. Well-differentiated tumors were associated significantly with the presence of s-MKRN1-Abs in the patients. The mRNA levels of MKRN1 were frequently higher in esophageal SCC tissues than in the peripheral normal esophageal mucosa. Stable transfection of ras-NIH3T3 cells with MKRN1 cDNA induced prominent morphological changes such as enlargement of the cell body and spreading. Ubiquitination of 80- and 82-kDa proteins were clearly observed in MKRN1-transfected cells but not in the parental cells, which were identified as L-FILIP (filamin A interacting protein 1).

Conclusion

MKRN1 is a novel SEREX antigen of esophageal SCC, and s-NKRN1-Abs can be a candidate of diagnostic markers of esophageal SCC with high specificity. It is plausible that MKRN1 is involved in carcinogenesis of the well-differentiated type of tumors possibly via ubiquitination of L-FILIP.