Hitoshi Zembutsu

Although metastasis or relapse is a leading cause of death for patients with gastric cancer, the hematogenous spread of cancer cells remains undetected at the time of initial therapy. The development of novel diagnostic molecular marker(s) to detect circulating gastric cancer cells is an issue of great clinical importance. We obtained peripheral blood samples from 10 patients with gastric cancer who underwent laparotomy and 4 healthy volunteers. Microarray analysis consisting of 30,000 genes or ESTs was carried out using eight gastric cancer tissues and normal gastric mucosae. We selected 53 genes up-regulated in gastric cancer compared to normal gastric mucosae from our microarray data set, and, among these, identified five candidate marker genes (TSPAN8, EPCAM, MMP12, MMP7 and REG3A) which were not expressed in peripheral blood mononuclear cells (PBMCs) from 4 healthy volunteers. We further carried out semi-quantitative nested reverse transcription-polymerase chain reaction (RT-PCR) for HRH1, EGFR, CK20 and CEA in addition to the five newly identified genes using PBMCs of patients with gastric cancer, and found that expression of one or more genes out of the nine was detected in 80% of the patients with gastric cancer. Moreover, the numbers of genes expressed in PBMCs were ≤2 and ≥2 in all vascular invasion-negative cases and in 5 of 6 positive cases, respectively, showing significant differences between the two groups (P=0.041). Nested RT-PCR analysis for the set of nine marker genes using PBMCs may provide the potential for detection of circulating gastric cancer cells prior to metastasis formation in other organs.

One of the most critical issues to be solved in regard to cancer chemotherapy is the need to establish a method for predicting efficacy or toxicity of anticancer drugs for individual patients. To identify genes that might be associated with chemosensitivity, we used a cDNA microarray representing 23,040 genes to analyze expression profiles in a panel of 85 cancer xenografts derived from nine human organs. The xenografts, implanted into nude mice, were examined for sensitivity to nine anticancer drugs (5-fluorouracil, 3-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-1-(2-chloroethyl)-1-nitrosourea hydrochloride, adriamycin, cyclophosphamide, cisplatin, mitomycin C, methotrexate, vincristine, and vinblastine). Comparison of the gene expression profiles of the tumors with sensitivities to each drug identified 1,578 genes whose expression levels correlated significantly with chemosensitivity; 333 of those genes showed significant correlation with two or more drugs, and 32 correlated with six or seven drugs. These data should contribute useful information for identifying predictive markers for drug sensitivity that may eventually provide "personalized chemotherapy" for individual patients, as well as for development of novel drugs to overcome acquired resistance of tumor cells to chemical agents.

Neoadjuvant chemotherapy with docetaxel for advanced breast cancer can improve the radicality for a subset of patients, but some patients suffer from severe adverse drug reactions without any benefit. To establish a method for predicting responses to docetaxel, we analyzed gene expression profiles of biopsy materials from 29 advanced breast cancers using a cDNA microarray consisting of 36,864 genes or ESTs, after enrichment of cancer cell population by laser microbeam microdissection. Analyzing eight PR (partial response) patients and twelve patients with SD (stable disease) or PD (progressive disease) response, we identified dozens of genes that were expressed differently between the ‘responder (PR)’ and ‘non-responder (SD or PD)’ groups. We further selected the nine ‘predictive’ genes showing the most significant differences and established a numerical prediction scoring system that clearly separated the responder group from the non-responder group. This system accurately predicted the drug responses of all of nine additional test cases that were reserved from the original 29 cases. Moreover, we developed a quantitative PCR-based prediction system that could be feasible for routine clinical use. Our results suggest that the sensitivity of an advanced breast cancer to the neoadjuvant chemotherapy with docetaxel could be predicted by expression patterns in this set of genes.