Tetsuro Kubota

5-Fluorouracil and dihydropyrimidine dehydrogenase

Dihydropyrimidine dehydrogenase (DPD) is a rate-limiting enzyme of (fluorinated) pyrimidine degradation that plays a significant role in the pharmacokinetics of 5-fluorouracil (5-FU). In addition, a catabolite of 5-FU induces a certain toxicity, and the sensitivity of 5-FU is determined by DPD activity in tumors. DPD is thus important clinically. Drugs have been developed that control variations of the pharmacokinetics of 5-FU by controlling or inhibiting DPD, thereby reducing toxicity and improving sensitivity. These fluorinated pyrimidines with DPD-inhibiting activity, called DPD-inhibitory fluoropyrimidines, contribute to oral therapy with 5-FU for cancer. This paper summarizes the important role of DPD in cancer chemotherapy with 5-FU.

Docetaxel enhances the cytotoxicity of cisplatin to gastric cancer cells by modification of intracellular platinum metabolism

We have examined the combined anticancer effects of docetaxel (DOC) and cisplatin (CDDP) in vitro using the gastric cancer cell lines MKN‐45, MKN‐74, and TMK‐1. Treatment of the cell lines with 30 μg/ml of DOC for 24 h followed by incubation with 3 or 10 μg/ml of CDDP for 24 h showed a clear synergistic effect. Sequence dependency of the agents was observed in these cell lines: DOC followed by CDDP (DC) showed a stronger antitumor effect than CDDP followed by DOC (CD) in all cell lines. To clarify the mechanism of action of the DC combination, total intracellular platinum (Pt) levels were evaluated after treatment with CDDP alone or combined with DC. For the MKN‐45 and ‐74 cell lines, cells treated with DOC (10 μg/ml for 12 h) and then CDDP showed significantly increased intracellular Pt accumulation compared to cells treated with CDDP alone. We also investigated alterations in intracellular glutathione (GSH) concentration in response to DOC and CDDP. MKN‐45 and ‐74 cells pretreated with DOC (10 μg/ml for 12 h) showed significantly increased intracellular GSH levels compared to cells administered CDDP only. To explain these findings, messenger RNA (mRNA) levels for multidrug resistance‐associated protein‐1 (MRP‐1), the ATP‐dependent pump for Pt‐GSH complexes, were quantified in CDDP‐treated MKN‐45 cells with and without DOC pretreatment. While CDDP administration increased MRP‐1 mRNA expression in MKN‐45 cells, MRP‐1 was not up‐regulated after CDDP administration in DOC pretreated MKN‐45 cells. Our results suggested that the enhanced CDDP toxicity due to DOC pretreatment may be related to the accumulation of intracellular Pt‐GSH complexes, because DOC appears to suppress the MRP‐1 up‐regulation induced by CDDP exposure in gastric cancer cells.

Gastrointestinal stromal tumor (GIST) and imatinib

Imatinib mesylate is the first and only effective drug for the treatment of gastrointestinal stromal tumor at present. Mutated exon 11 of the KIT receptor is essential for the pathogenesis and response to imatinib mesylate of gastrointestinal stromal tumor; the efficacy rate (complete response + partial response) of imatinib mesylate is 53.8%, and the disease-control rate (complete response + partial response + stable disease) is 84%. Almost 90% of patients experienced non-hematological and hematological adverse effects, which were tolerable, in particular at a daily dose of 400u2009mg imatinib mesylate, which warranted response induction for half of the patients, and is the dose approved by Japanese medical insurance. Clinical trials suggest that an increased dose of imatinib mesylate would be beneficial, and that the interruption of imatinib treatment might result in disease progression even after a partial response. Tentative Japanese guidelines for the diagnosis and therapy of gastrointestinal stromal tumors are being prepared by the Gastrointestinal Stromal Tumor Committee of the Japan Society of Clinical Oncology, and are presented here for critical comments by colleagues.

Differences between scirrhous and non-scirrhous human gastric carcinomas from the aspect of proMMP-2 activation regulated by TIMP-3

AbstractGastric carcinomas can be classified into scirrhous carcinomas (SC), i.e. `linitis plastica or Borrmann 4 gastric cancer, and non-scirrhous carcinomas (NSC). SC are characterized by diffuse invasive growth patterns with marked fibrosis, frequent peritoneal dissemination and lymph-node metastases and poor prognosis, while NSC show medullary growth patterns and common hematogenous metastases. To study the differences in local expression levels of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) between SC and NSC, we examined the expression of MMPs and TIMPs in human gastric carcinoma tissues by several methods including sandwich-enzyme immunoassay systems, gelatin zymography, reverse transcriptase-polymerase chain reaction (RT-PCR), real-time quantitative PCR, immunoblotting, immunohistochemistry and in situ zymography. Of the seven MMPs and two TIMPs tested, only proMMP-2 levels were remarkably higher in SC than in NSC (P<0.01), and proMMP-2 activation ratio was significantly lower in SC than in NSC (P<0.05). TIMP-3 mRNA levels were remarkably about 2-fold higher in SC than in NSC tissues (P<0.01). TIMP-3 production in SC was confirmed by immunoblotting and TIMP-3 was immunolocalized to stromal fibroblasts in SC. TIMP-3 mRNA levels inversely correlated with proMMP-2 activation ratios, although the expression levels of MT1-MMP and MT2-MMP were not different in SC and NSC. By in situ zymography, gelatinolytic activity appeared to be weaker in SC than in NSC. All these data suggest that proMMP-2 activation is down-regulated by TIMP-3 expressed in scirrhous gastric carcinomas. Our findings may explain the differences in clinical behaviors of SC and NSC.n Abbreviations: EIA – sandwich enzyme immunoassay; GAPDH – glyceraldehyde-3-phosphate dehydrogenase. MMP – matrix metalloproteinase; MT-MMP – membrane-type MMP; N – non-carcinoma; NSC – non-scirrhous carcinomas; RT-PCR – reverse transcriptase-polymerase chain reaction; SC – scirrhous carcinomas; SDS-PAGE – sodium dodecyl sulfate-polyacrylamide gel electrophoresis; TIMP – tissue inhibitor of metalloproteinases

Phase I/II study of irinotecan (CPT-11) and S-1 in the treatment of advanced gastric cancer.

A phase I/II study to determine the recommended dose for combination therapy with CPT-11 (irinotecan hydrochloride) and S-1 (tegafur, gimestat and otastat potassium) for advanced or recurrent gastric cancer, and to assess the safety and efficacy of this therapy. In the phase I portion of the study, S-1 was administered from day 1 to 14 at a fixed dose approved in Japan (80u2009mg/m2/day), and CPT-11 was administered on days 1 and 8, with its dose being escalated to 100 from 80u2009mg/m2. This regimen was repeated at 3-week intervals. The phase II portion of the study assessed the efficacy and safety of this regimen at the recommended dose determined in the phase I portion of the study. Seven patients were enrolled in the phase I portion of the study. The dose-limiting toxicity was the delay of administration owing to adverse reactions (leucopenia and diarrhea). The maximum tolerated dose of CPT-11 was 100u2009mg/m2 and the recommended dose was determined to be 80u2009mg/m2. In the phase II portion of the study, 10 patients with no prior chemotherapy regimen were enrolled. The median number of treatment cycles given was 4.5, the response rate was 20.0% (2/10) in all patients, the tumor control rate stable disease or better response was 60% (6/10) and the mean survival time was 311 days. Major adverse reactions included a decreased hemoglobin level, diarrhea, nausea and anorexia of grade 3 or worse (each occurred in 10% of the patients). Other adverse reactions were slight and well tolerated. The present combination therapy with CPT-11 and S-1 produced a low response rate but a high tumor control rate (stable disease or better response) and slight prolongation of survival time. This is a well-tolerated ambulatory regimen for advanced gastric cancer.

Clinical and pathological disappearance of peritoneal dissemination in a patient with advanced gastric cancer receiving chemotherapy with S-1 and low-dose cisplatin

A 54-year-old woman with severe abdominal distention suffered from massive ascites. Cytological examination revealed adenocarcinoma cells, leading to a diagnosis of peritonitis carcinomatosa. Gastrointestinal fiberscopy (GIF) resulted in a histological diagnosis of type 4 advanced gastric cancer with signet-ring cell carcinoma. The clinical diagnosis was confirmed to be cT3(SE)cN1cM0cH0cP1, cStage IV gastric cancer, type 4, according to the Japanese classification of gastric carcinoma. The patient was treated with S-1 and low-dose cisplatin (CDDP) in order to alleviate the critical state of the disease. After the third cycle of the regimen, the clinical response of P1 was classified as a partial response (PR) according to the World Health Organization (WHO) criteria. The patient’s appetite loss and abdominal discomfort were markedly alleviated. The patient experienced grade 2 leukocytopenia throughout the regimen. Surgery was performed. Ascites and peritoneal disseminated lesions were not observed, and cytological examination of the peritoneal washes was negative. Total gastrectomy with D1 lymph node dissection was performed, and the surgical diagnosis was sT3(SE)sN0sM0sH0sP0; sStage II. Microscopically, viable cancer cells were found to be scattered throughout the subserosal-serosal layers in the resected stomach. All of the samples from lesions that were potentially cancers involving peritoneal dissemination were diagnosed as fibrous scar tissues without any viable cancer cells. The patient is alive without recurrence at 10 months after surgery and 14 months after the initial chemotherapy. Thus, systemic chemotherapy with S-1/low-dose CDDP achieved desirable control of peritoneal disseminated cells, as assessed microscopically, suggesting that the regimen may be an effective strategy for the treatment of advanced gastric cancer with peritonitis carcinomatosa.