Abstract LB-86: Analysis of cancer specific gene methylation to diagnose micrometastasis to the lymph nodes and peritoneal cavity in gastric cancer patients
Authors: Hiraki Masatsugu , Kitajima Yoshihiko , Nakamura Jun , Hashiguchi Kazuyoshi , Koga Yasuo , Noshiro Hirokazu , Miyazaki Kohji 
Published: February 2011

Abstract
Background and Aims: Aberrant DNA methylation occurs in various cancers and plays important roles in carcinogenesis, tumor progression and chemosensitivity. These epigenetic changes can be utilized to detect micrometastasis in cancer patients. The aim of this study was to confirm that gene methylation is a novel diagnostic marker for micrometastasis to the lymph nodes (LN) and peritoneal fluid (PF) in gastric cancer patients.
Methods and Results: 1) An analysis of micrometastasis in lymph nodes: DNA methylation of 7 candidate genes was investigated in 49 primary cancer tissue specimens and corresponding non-cancerous mucosa specimens. Four genes, CHFR, RUNX3, hMLH1, and MGMT, were revealed to express cancer specific methylation and were analyzed in further studies. An analysis of 29 LN that were histologically confirmed as cancer cell positive revealed that 86% of the samples were positive for methylation of at least one of the 4 genes. An analysis of 25 LN that were histologically confirmed to be cancer negative showed 30% of the samples were positive for methylation. In addition, 15% of LN exhibited positive for both methylation and mRNA of CEA, CK19 or CK20. Cancer specific methylation could be detected in the metastatic LN with 86% sensitivity. Micrometastasis was suspected in 30% of LN without histological metastasis.
2) An analysis of micrometastasis in peritoneal fluid: Peritoneal fluid was collected from 80 gastric cancer patients during surgery. DNA methylation of 7 candidate genes was analyzed using the 80 PF samples. The patients were divided into 3 groups; Group A (n = 35): Depth of cancer invasion was less than the muscularis propria (MP), Group B (n = 31): Cancer invasion was beyond the MP. Neither group A nor B showed cancer cells in the peritoneal cytology and histology. Group C (n = 14): Disseminated cancer cells were histocytologically confirmed in the PF. The methylation rate in 3 genes, CHFR, E-cadherin and BNIP3, were significantly different among the groups and increased in order of group A, B and C. Analysis using the multigene methylation in Group C revealed cancer cells in PF with 57% sensitivity and 91% specificity. On the other hand, micrometastasis in PF was suspected in 9% and 19% in Group A and B, respectively. In fact, 2 of the 5 patients with multigene methylation in the group B experienced peritoneal recurrence after the operation, while those without or with a single gene methylation did not experience recurrence.
Conclusions: The present study suggests that a methylation analysis in the LN and PF could potentially detect occult neoplastic cells. However, it is important to improve the diagnostic sensitivity by increasing the number of genes that are specifically methylated in cancer cells. Further methylation analyses, by adding several genes, will be discussed at this meeting.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-86.