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Detection of Minimal Gastric Cancer Cells in Peritoneal Washings by Focused Microarray Analysis with Multiple Markers: Clinical Implications

¹ Department of Gastrointestinal Surgery, University of Tokyo Graduate School of Medicine, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8655, Japan
² Department of Pathology, University of Tokyo Graduate School of Medicine, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
³ Nanotechnology and Advanced System Research Laboratories, Canon Inc., Shimomaruko 3-30-2, Ohta-ku, Tokyo 146-8501, Japan
⁴ Laboratory of Pathology, Aichi Cancer Center Research Institute, Aichi Cancer Center Hospital, Kanokoden 1-1, Chikusa-ku, Nagoya, Aichi 464-8681, Japan
⁵ Department of Gastroenterological Surgery, Nagoya University Graduate School of Medicine, 65, Tsurumai-cho, Showa-ku, Nagoya, Aichi 466-8550, Japan
⁶ Genetics Division, National Cancer Center Research Institute, National Cancer Center, Tsukiji 5-1-1, Chuo-ku, Tokyo 104-0045, Japan
⁷ Clinical Laboratory, National Cancer Center Hospital, Tsukiji 5-1-1, Chuo-ku, Tokyo 104-0045, Japan
⁸ Surgical Oncology Department, National Cancer Center Hospital, Tsukiji 5-1-1, Chuo-ku, Tokyo 104-0045, Japan

Correspondence: Address correspondence and reprint requests to: Hiroki Sasaki, PhD; E-mail: hksasaki{at}gan2.res.ncc.go.jp

Background: Peritoneal cytology is an important prognostic factor of gastric cancer. However, peritoneal cytology requires great skill, which may explain its low prevalence. A reverse transcriptase–polymerase chain reaction–based assay with multiple marker genes or immunocytochemistry was assessed as an alternative method of gathering the same kind of data as cytology.

Methods: Peritoneal washings from 179 patients with gastric cancer were analyzed by multiplex reverse transcriptase–polymerase chain reaction with 10 marker genes and subsequent hybridization to a customized oligo-nucleotide array. Results with this assay were either validated as a prognostic factor or confirmed by demonstrating the presence of cancer cells by immunocytochemical cytology.

Results: Only 1 (2.2%) of 44 disease-free cases was shown to be positive by the microarray assay, whereas 13 (93%) of 14 conventional cytology–positive cases were found to be positive. This assay further detected approximately one-third of cytology-negative patients either with peritoneal recurrence (7 of 20, 35%) or with non-peritoneal recurrence (6 of 22, 27%). A high concordance between the microarray assay and immunocytochemical cytology with five antibodies against CK20, FABP1, MUC2, TFF1, and MASPIN was confirmed. The clinical outcome of the microarray assay–positive cases was poor, as was that of the cytology-positive cases.

Conclusions: Our assay, though time-consuming and requiring special equipment, demonstrated a specificity and sensitivity equal to or better than cytology in our institutes. The minimal free peritoneal cancer cells detected by the microarray assay may provide the same clinical information as larger amounts of cancer cells for patients with gastric cancer. An anti-MASPIN antibody may be helpful in peritoneal cytology of gastric cancer.

Key Words: Gastric cancer • Peritoneal cytology • RT-PCR • Microarray • MASPIN