The research at the Genetics Division is aimed at elucidating the molecular basis of carcinogenesis, mainly through the analysis of clinical materials in order to contribute to cancer diagnosis, treatment and prevention.

Peritoneal cytology is an important prognostic factor in cases of gastric cancer after surgery. However, peritoneal cytology has a learning curve, which may be an explanation for the low prevalence of its use. To improve the sensitivity of peritoneal cytology and to ensure that the procedure has uniform accuracy, regardless of the site at which the procedure is performed, an RT-PCR-based mini-chip assay with multiple marker genes was established ⁽⁷⁷⁾. Transcripts of 10 previously identified marker genes were amplified and labeled from 179 peritoneal washings by multiplex-RT-PCR followed subsequently by hybridization to a customized oligo-nucleotide array (mini-chip). The results of this mini-chip assay were either validated as a prognostic factor or confirmed by demonstrating the presence of cancer cells by immunocytochemical cytology. Only one case (2.2%) in 44 disease-free cases was shown to be positive by the mini-chip assay, while 13 (93%) of 14 conventional cytology-positive cases were found to be positive. This assay further detected approximately one-third of cytology-negative patients with either peritoneal recurrence (7/20, 35%) or non-peritoneal recurrence (6/22, 27%). A high concordance (86%) between the results of the mini-chip assay and immunocytochemical cytology performed using 5 antibodies against CK20, FABP1, MUC2, TFF1, and MASPIN was confirmed. The clinical outcome of the mini-chip assay-positive cases was poor, as also was that of the cytology-positive cases.

Early detection of colorectal cancer originating from any part of the intestine is desirable because this cancer can be cured surgically if diagnosed early. To establish a mini-chip assay for a fecal RNA-based colorectal cancer screening, useful marker genes were searched by genome-wide expression profiling ⁽⁷⁸⁾. Of the 14,564 genes analyzed, only 3 (PAP, REG1A, and DPEP1) could be selected as final candidates that were expressed frequently at any stage of the cancer and suppressed in non- cancerous tissues and also in the peripheral blood cells and colonocytes of healthy volunteers. Direct comparison of fecal RNA-expression profiles between colorectal cancer patients and healthy volunteers revealed that most of the genes (92%) expressed in the colonocytes of the cancer patients were not expressed in those of the healthy volunteers. Six genes (SEPP1, RPL27A, ATP1B1, EEF1A1, SFN, and RPS11) selected randomly from 85 cancer patient-derived colonocyte-specific genes were evaluated. In total, RT-PCR or mini-chip assay of all of the 9 genes in total detected 18 (78%) of 23 curable colorectal cancers (Dukes' stages A-C), 9 or 10 (64% or 71%) of 14 early cancers with no lymph node metastasis (Dukes' stage A or B), and 4 (80%) of 5 right-sided cancers. The extensive gene list may provide other markers for fecal RNA-based colorectal cancer screening.

Defining regulatory cascades of apoptosis of the epithelium is important for understanding carcinogenesis, since cancer cells are considered to arise as a result of the collapse of the cascades. GASDERMIN (GSDM) was identified at the Division and has been reported to be expressed in the stomach, but suppressed in gastric cancer cell lines. This year, GSDM was found to be expressed in the mucus-secreting pit cells of the gastric epithelium and to be frequently silenced in primary gastric cancers. GSDM exerted strong apoptotic-inducing activity and its expression was regulated by the transcription factor LIM domain only 1 (LMO1) through a sequence to which the transcription factor RUNX3 binds, in the GSDM promoter region. It was further demonstrated that GSDM is co-expressed with LMO1, RUNX3 and type II Transforming Growth Factor-b receptor (TGF-bRII) in the pit cells, and that TGF-b upregulates LMO1 and GSDM expressions in gastric epithelial cell lines and induces apoptosis, which was confirmed by the finding that the apoptosis induction was inhibited by suppression of each of LMO1, RUNX3, and GSDM expression. The present data suggest that TGF-b, LMO1, possibly RUNX3, and GSDM form a regulatory pathway for directing the pit cells to apoptosis, and that GSDM downregulation could be involved in gastric carcinogenesis ⁽⁷⁹⁾.

The t(X;18)(p11.2;q11.2) translocation found in synovial sarcomas results in a fusion between the SYT gene on chromosome 18 and an SSX gene on the X chromosome. Although SYT-SSX fusion proteins appear to trigger synovial sarcoma development, little is known about the downstream targets of SYT-SSX. The COM1 gene was identified as a target of the SYT-SSX1 fusion protein using gene expression profiles and its downregulation played an important role in synovial sarcoma growth ⁽⁸⁰⁾.

This Division has been collaborating with several other investigators inside and outside the National Cancer Center to identify germline polymorphisms and mutations implicated in cancer susceptibilities or drug responses ^(81-85). This research includes the development of the genomic data analysis method, and the SNP and expression profile data have been published in part in a database (http://gemdbj.nibio.go.jp). Clinical genetic testing service for major familial cancer syndromes has been continued at the outpatient clinic in the National Cancer Center Hospital since 1998.

WNT signals are transduced to the canonical pathway for cell fate determination, and to non-canonical pathways for regulation of planar cell polarity, cell adhesion, and motility. The target genes for WNT signaling cascades are determined in a context-dependent manner due to the epigenetic status and expression profile of transcriptional regulators.

MYC, CCND1, AXIN2, FGF20, WISP1, JAG1, DKK1 and Glucagon are representative target genes of the canonical WNT signaling cascade, while CD44, Vimentin and STX5 are those of non-canonical WNT signaling cascades ⁽⁸⁶⁾. After completion of the WNTome and Post-WNTome Projects, the Section has been working on the stem cell signaling network, consisting of WNT, FGF, Notch, BMP and Hedgehog signaling cascades ⁽⁸⁷⁾. Integrative genomic analyses were carried out on genes encoding components of the stem cell signaling network ^(88-92), and those encoding histone demethylases ^{(93, 94)}. Meta analyses of the genome-wide association study (GWAS) was also carried out to identify that SNPs of genes encoding the stem cell signaling molecules were associated with the risk of gastric cancer ⁽⁹⁵⁾. Therefore, it was concluded that dysregulation of the stem cell signaling network due to the accumulation of germline mutations, SNP, Helicobacter pylori infection, epigenetic change and genetic alteration gives rise to gastric cancer ⁽⁹⁵⁾.

The researchers at this Division collaborate with research groups inside and outside the Institution in various fields of genetic and genomic research on cancer ^(96-99).