Impact of the 12-gene recurrence score assay on deciding adjuvant chemotherapy for stage II and IIIA/B colon cancer: the SUNRISE-DI study.

BACKGROUND: Recent advances in adjuvant chemotherapy for early colon cancer have widened physicians' recommendations on the regimen and duration (3 or 6 months) of the treatment. We conducted this prospective study to evaluate whether the 12-gene recurrence score (12-RS) assay affected physicians' recommendations on adjuvant treatment selection. PATIENTS AND METHODS: Patients with stage IIIA/IIIB or stage II colon cancer were enrolled. After the patients discussed adjuvant treatment with their treating physicians, the physicians filled in the questionnaire before assay indicating the treatment recommendation. When the 12-RS assay results were available, the physicians again filled in the questionnaire after assay. The primary endpoint was the rate of change in treatment recommendations from before to after the assay, with a threshold rate of change being 20%. Patients with stage IIIA/B to II were enrolled in a ratio of 2 : 1. RESULTS: Overall, the treatment recommendations changed in 40% of cases after obtaining 12-RS assay results. Recommendations were changed in 45% (80/178; 95% confidence interval, 37% to 53%; P < 0.001) and 30% (29/97; 95% confidence interval, 21% to 40%; P < 0.001) of patients with stage IIIA/B and II colon cancer, respectively. Patients with stage IIIA/B cancer had significantly more change than those with stage II cancer (P = 0.0148). From before to after the 12-RS assay, the percentage of patients whose physicians reported being confident in their treatment recommendations significantly increased from 54% to 81% in stage IIIA/B (P < 0.001) and from 65% to 83% in stage II (P < 0.001). CONCLUSION: Our study confirmed the usefulness of the 12-RS assay in aiding the physician-patient decision-making process for tailoring adjuvant chemotherapy for stage IIIA/B colon cancer.

S-1 and oxaliplatin versus tegafur-uracil and leucovorin as post-operative adjuvant chemotherapy in patients with high-risk stage III colon cancer: updated 5-year survival of the phase III ACTS-CC 02 trial.

BACKGROUND: The ACTS-CC 02 trial demonstrated that S-1 plus oxaliplatin (SOX) was not superior to tegafur-uracil and leucovorin (UFT/LV) in terms of disease-free survival (DFS) as adjuvant chemotherapy for high-risk stage III colon cancer (any T, N2, or positive nodes around the origin of the feeding arteries). We now report the final overall survival (OS) and subgroup analysis according to the pathological stage (TNM 7th edition) for treatment efficacy. PATIENTS AND METHODS: Patients who underwent curative resection for pathologically confirmed high-risk stage III colon cancer were randomly assigned to receive either UFT/LV (300 mg/m2 of UFT and 75 mg/day of LV on days 1-28, every 35 days, five cycles) or SOX (100 mg/m2 of oxaliplatin on day 1 and 80 mg/m2/day of S-1 on days 1-14, every 21 days, eight cycles). The primary endpoint was DFS and the patients' data were updated in February 2020. RESULTS: A total of 478 patients in the UFT/LV group and 477 patients in the SOX group were included in the final analysis. With a median follow-up time of 74.3 months, the 5-year DFS rate was 55.2% in the UFT/LV group and 58.1% in the SOX group [stratified hazard ratio (HR) 0.92; 95% confidence interval (CI) 0.76-1.11; P = 0.3973], and the 5-year OS rates were 78.3% and 79.1%, respectively (stratified HR 0.97; 95% CI 0.76-1.24; P = 0.8175). In the subgroup analysis, the 5-year OS rates in patients with T4N2b disease were 51.0% and 64.1% in the UFT/LV and SOX groups, respectively (HR 0.72; 95% CI 0.40-1.31). CONCLUSION: Our final analysis reconfirmed that SOX as adjuvant chemotherapy is not superior to UFT/LV in terms of DFS in patients with high-risk stage III colon cancer. The 5-year OS rate was similar in the UFT/LV and SOX groups.

CCAT1 and CCAT2 long noncoding RNAs, located within the 8q.24.21 'gene desert', serve as important prognostic biomarkers in colorectal cancer.

BACKGROUND: 8q24.21 is a frequently amplified genomic region in colorectal cancer (CRC). This region is often referred to as a 'gene desert' due to lack of any important protein-coding genes, highlighting the potential role of noncoding RNAs, including long noncoding RNAs (lncRNAs) located around the proto-oncogene MYC. In this study, we have firstly evaluated the clinical significance of altered expression of lncRNAs mapped to this genomic locus in CRC. PATIENTS AND METHODS: A total of 300 tissues, including 280 CRC and 20 adjacent normal mucosa specimens were evaluated for the expression of 12 lncRNAs using qRT-PCR assays. We analyzed the associations between lncRNA expression and various clinicopathological features, as well as with recurrence free survival (RFS) and overall survival (OS) in two independent cohorts. RESULTS: The expression of CCAT1, CCAT1-L, CCAT2, PVT1, and CASC19 were elevated in cancer tissues (P = 0.039, <0.001, 0.018, <0.001, 0.002, respectively). Among these, high expression of CCAT1 and CCAT2 was significantly associated with poor RFS (P = 0.049 and 0.022, respectively) and OS (P = 0.028 and 0.015, respectively). These results were validated in an independent patient cohort, in which combined expression of CCAT1 and CCAT2 expression was significantly associated with a poor RFS (HR:2.60, 95% confidence interval [CI]: 1.04-6.06, P = 0.042) and a poor OS (HR:8.38, 95%CI: 2.68-37.0, P < 0.001). We established a RFS prediction model which revealed that combined expression of CCAT1, CCAT2, and carcinoembryonic antigen was a significant determinant for efficiently predicting RFS in stage II (P = 0.034) and stage III (P = 0.001) CRC patients. CONCLUSIONS: Several lncRNAs located in 8q24.21 locus are highly over-expressed in CRC. High expression of CCAT1 and CCAT2 significantly associates with poor RFS and OS. The expression of these two lncRNAs independently, or in combination, serves as important prognostic biomarkers in CRC.

A Comparison of the Regional Circulation in the Feet between Dialysis and Non-Dialysis Patients using Indocyanine Green Angiography.

BACKGROUND AND AIMS: Peripheral artery disease in dialysis cases is more prone to critical limb ischemia compared to non-dialysis cases, with a significantly high rate of major amputation of the lower limbs. Lesions are distributed on the more distal side in dialysis critical limb ischemia cases. The aim of this study was to investigate the usefulness of indocyanine green angiography to determine differences in the regional circulation in the foot between dialysis and non-dialysis patients. MATERIALS AND METHODS: The subjects included 62 cases, among which 20 were dialysis patients and 42 were non-dialysis patients. We compared the indocyanine green angiography parameters for regions of interest in the dialysis and non-dialysis groups, which included the magnitude of intensity from indocyanine green onset to maximum intensity (Imax), the time from indocyanine green onset to maximum intensity (Tmax), the time elapsed from the fluorescence onset to half the maximum intensity (T1/2), and the time from maximum intensity to declining to 90% of the maximum intensity (Td90%). These indocyanine green angiography parameters were measured at region of interest 1 (the Chopart joint), region of interest 2 (the Lisfranc joint), and region of interest 3 (the distal region of the first metatarsal bone). RESULTS: In the comparison between the dialysis and non-dialysis groups, a significant difference was observed regarding Tmax, T1/2, and Td90%, especially in region of interest 3. CONCLUSION: In this study, we show that regional tissue perfusion is more deteriorated in dialysis patients compared with non-dialysis patients using indocyanine green angiography. Tmax, T1/2, and Td90% could be useful clinical parameters to compare ischemic severity of the lower limb between dialysis and non-dialysis patients.

Prognostic value of tropomyosin-related kinases A, B, and C in gastric cancer

Purpose: Tropomyosin-related kinase (Trk) receptors play critical roles in tumor development and are considered attractive targets for cancer therapy. We investigated correlations of the expression of TrkA, TrkB, and TrkC with clinicopathological features and outcomes in gastric cancer. Methods: Tumor samples were obtained from 221 patients with gastric cancer who underwent gastrectomy between 2003 and 2007. The expression of TrkA, TrkB, and TrkC was analyzed using immunohistochemical staining. The relationship of their expression to clinicopathological factors and outcomes was assessed. Results: High expression of TrkA, TrkB, or TrkC was significantly associated with histopathology (p = 0.022, p < 0.001, and p < 0.001). High expression of TrkA was significantly correlated with variables related to tumor progression, including lymph node metastasis (p = 0.024) and distant metastasis or recurrence (p < 0.001). Distant metastasis or recurrence was found in a significantly higher proportion of patients with high expression of TrkC than in those with low expression (p = 0.036). High expression of TrkA was significantly associated with poorer relapse-free survival (RFS) in univariate analysis (p = 0.001). High expression of TrkA or TrkC was significantly associated with poorer disease-specific survival (DSS) in univariate analysis (p < 0.001 and p = 0.008). In multivariate analysis, TrkA was an independent predictor of RFS [hazard ratio (HR), 2.294; 95 % confidence interval (CI), 1.309-4.032; p = 0.004] and DSS (HR, 2.146; 95 % CI, 1.195-3.861; p = 0.011). Expression of TrkB was not associated with RFS or DSS in univariate analysis. Conclusions: Our results demonstrated that TrkA expression was associated with tumor progression and poor survival, and was an independent predictor of poor outcomes in gastric cancer patients

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Prognostic value of tropomyosin-related kinases A, B, and C in gastric cancer.

PURPOSE: Tropomyosin-related kinase (Trk) receptors play critical roles in tumor development and are considered attractive targets for cancer therapy. We investigated correlations of the expression of TrkA, TrkB, and TrkC with clinicopathological features and outcomes in gastric cancer. METHODS: Tumor samples were obtained from 221 patients with gastric cancer who underwent gastrectomy between 2003 and 2007. The expression of TrkA, TrkB, and TrkC was analyzed using immunohistochemical staining. The relationship of their expression to clinicopathological factors and outcomes was assessed. RESULTS: High expression of TrkA, TrkB, or TrkC was significantly associated with histopathology (p = 0.022, p < 0.001, and p < 0.001). High expression of TrkA was significantly correlated with variables related to tumor progression, including lymph node metastasis (p = 0.024) and distant metastasis or recurrence (p < 0.001). Distant metastasis or recurrence was found in a significantly higher proportion of patients with high expression of TrkC than in those with low expression (p = 0.036). High expression of TrkA was significantly associated with poorer relapse-free survival (RFS) in univariate analysis (p = 0.001). High expression of TrkA or TrkC was significantly associated with poorer disease-specific survival (DSS) in univariate analysis (p < 0.001 and p = 0.008). In multivariate analysis, TrkA was an independent predictor of RFS [hazard ratio (HR), 2.294; 95 % confidence interval (CI), 1.309-4.032; p = 0.004] and DSS (HR, 2.146; 95 % CI, 1.195-3.861; p = 0.011). Expression of TrkB was not associated with RFS or DSS in univariate analysis. CONCLUSIONS: Our results demonstrated that TrkA expression was associated with tumor progression and poor survival, and was an independent predictor of poor outcomes in gastric cancer patients.

Magnetically controlled convection in a diamagnetic fluid.

We present visualization and measurement of the convection of water under a high magnetic field applied vertically to the fluid. The convection was either suppressed or enhanced depending on the direction of the magnetic force. The magnetic field effect was evaluated quantitatively by measuring the onset of convection, and discussed in terms of the Rayleigh number which includes the magnetic term. The results clearly show that the convection in a diamagnetic fluid such as water can be controlled using a common 10 T class magnet.

Both gene expression for orotate phosphoribosyltransferase and its ratio to dihydropyrimidine dehydrogenase influence outcome following fluoropyrimidine-based chemotherapy for metastatic colorectal cancer.

Activation of 5-fluorouracil into its nucleotides requires phosphorylation by three pathways involving orotate phosphoribosyl-transferase (OPRT), uridine phosphorylase (UP), or thymidine phosphorylase (TP). In this study, we investigated the association between gene expressions of these three enzymes and antitumour effect. Gene expressions in primary colorectal tumours were analysed by a real-time reverse transcriptional-polymerase chain reaction method in 37 patients receiving oral treatment of tegafur-uracil and leucovorin for metastatic diseases. The median values of OPRT mRNA expressions were 1.39 and 0.85 for responding tumours and nonresponding tumours, respectively, showing a statistically significant difference (P=0.0008). Responding tumours had statistically lower expressions of TP mRNA than nonresponding tumours (P=0.006). However, there was no difference in UP mRNA expression between responding and nonresponding tumours. Patients with high OPRT (>/=1.0) gene expression survived longer than those with low OPRT (<1.0) expression. Dihydropyrimidine dehydrogenase (DPD) gene expressions were measured. Responding tumours had a statistically higher OPRT/DPD ratio than the nonresponding ones (P=0.003). When the median value of the OPRT/DPD ratio was selected as the cutoff value, patients with a high OPRT/DPD ratio survived statistically longer than those with a low ratio (P=0.0014). In conclusion, both the expression of OPRT gene and the OPRT/DPD ratio might be useful as predictive parameters for the efficacy of fluoropyrimidine-based chemotherapy for metastatic colorectal cancer.

ERCC1 and thymidylate synthase mRNA levels predict survival for colorectal cancer patients receiving combination oxaliplatin and fluorouracil chemotherapy.

PURPOSE: To test the hypotheses of whether the relative mRNA expression of the thymidylate synthase (TS) gene and the excision cross-complementing (ERCC1) gene are associated with response to and survival of fluorouracil (5-FU)/oxaliplatin chemotherapy in metastatic colorectal cancer. PATIENTS AND METHODS: Patients had progressive stage IV disease after unsuccessful 5-FU and irinotecan chemotherapy. All patients were evaluated for eligibility for a compassionate 5-FU/oxaliplatin protocol. cDNA was derived from paraffin-embedded tumor specimens to determine TS and ERCC1 mRNA expression relative to the internal reference gene beta-actin using fluorescence-based, real-time reverse transcriptase polymerase chain reaction. RESULTS: The median TS gene expression level from 50 metastasized tumors was 3.4 x 10(-3) (minimum expression, 0.18 x 10(-3);maximum expression, 11.5 x 10(-3)), and the median ERCC1 gene expression level was 2.53 x 10(-3) (minimum, 0.0; maximum, 14.61 x 10(-3)). The gene expression cutoff values for chemotherapy nonresponse were 7.5 x 10(-3) for TS and 4.9 x 10(-3) for ERCC1. The median survival time for patients with TS

Different lengths of a polymorphic repeat sequence in the thymidylate synthase gene affect translational efficiency but not its gene expression.

PURPOSE: Thymidylate synthase (TS) is a target enzyme of 5-fluorouracil. Recently, the TS gene has been shown to contain a polymorphic tandem repeat sequence. The aim of this study was to determine whether differences in the number of tandem repeats could affect gene expression or mRNA translation. EXPERIMENTAL DESIGN: We quantified TS mRNA isolated from 130 colorectal cancer tissues by real-time reverse transcription-PCR and TS protein in 92 available samples by the fluoro-dUMP binding assay. These values were compared with TS genotypes of the samples determined by a PCR assay. RESULTS: There was no relation between TS genotype and mRNA expression level. On the other hand, cancer tissues with the 3R/3R genotype had a significantly higher TS protein expression level than did those with the 2R/3R genotype. These results suggest that the efficiency of TS mRNA translation is responsible for the genotype-dependent difference in TS protein expression. Further analysis using TS 5'-untranslated region-luciferase reporter constructs showed that the RNA with the three-repeat sequence was translated three to four times more efficiently than that with two-repeat sequence. CONCLUSIONS: From the results of both in vitro and in vivo study, we conclude that TS mRNA with a three-repeat sequence has greater translation efficiency than that with the two-repeat sequence. The results provide the rationale for comprehensive usage of TS genotyping with quantitation of TS mRNA or TS protein to predict the patient's response to 5-fluorouracil-based chemotherapy.

Expression of pyrimidine nucleoside phosphorylase (PyNPase) in colorectal cancer.

BACKGROUND: We investigated the expression of PyNPase both in cancer cells and in stroma cells to clarify the correlation between PyNPase expression and the prognosis of patients with colorectal cancer. METHODS: Using immunohistochemical staining with an anti-PyNPase antibody, the PyNPase expression in tissues from 114 patients with stage II or III colorectal cancer was examined. From the correlation between PyNPase expression and the clinicopathological findings, the prognosis for survival was analyzed. RESULTS: The expression of PyNPase was classified as negative or positive on the basis of staining. No relationship between PyNPase expression and any of the clinicopathological findings was identified. However, a relationship was observed regarding positive staining between cancer cells and stroma cells. The prognosis of patients with positive staining in both cancer cells and stroma was worse than that of other patients. In multivariate analyses, expression in cancer cells was the strongest predictor of prognosis. CONCLUSIONS: PyNPase expression appears to be a relevant factor for predicting the prognosis of colorectal cancer.

Upregulation of ornithine decarboxylase mRNA expression in Barrett's esophagus and Barrett's-associated adenocarcinoma.

The Barrett's multistage process is characterized histopathologically by progression from Barrett's intestinal metaplasia to Barrett's esophagus with dysplasia and ultimately adenocarcinoma. Understanding the cellular and molecular events in this multistage process may contribute to improved diagnosis and treatment. Ornithine decarboxylase (ODC) is the first enzyme in the biosynthesis of polyamines. Elevated ODC activity has been found to be associated with progression during Barrett's esophagus, but the regulation of ODC gene expression in the development of Barrett's-associated adenocarcinoma has not been reported. The aim of this study was to assess the prevalence and timing of ODC mRNA expression in the Barrett's metaplasia-dysplasia-adenocarcinoma sequence. ODC mRNA expression levels, relative to the stably expressed internal reference gene beta-actin, were measured using a quantitative reverse transcription-polymerase chain reaction (RT-PCR) method (ABI 7700 Sequence Detector System) in 104 specimens from 19 patients with Barrett's esophagus without carcinoma and 22 patients with Barrett's-associated adenocarcinoma. The median ODC mRNA expression levels were significantly increased in Barrett's esophagus tissues compared to matched normal tissues in patients without adenocarcinoma of the esophagus (P = 0.002; Wilcoxon test). A significant progressive increase in ODC mRNA expression was detectable through the stages of the metaplasia-dysplasia-carcinoma sequence in patients with Barrett's-associated adenocarcinoma (r = 0.719; P < or = 0.001; Spearman's rho test). These findings show that upregulation of ODC mRNA expression is an early event in the development and progression of Barrett's-associated adenocarcinoma of the esophagus, and they suggest that high ODC mRNA expression levels may be a clinically useful biomarker for the detection of occult adenocarcinoma

Thymidylate synthase gene expression in primary colorectal cancer and metastatic sites.

Thymidylate synthase (TS) expression has been identified as an important predictor of response to 5-fluorouracil (5-FU). However, there is relatively little information on the heterogeneity of TS mRNA expression between primary and metastatic tumors, as well as differential expression of TS mRNA in metastatic sites. In this study, TS mRNA expression was measured in primary colorectal cancer tumors and various metastatic tumors. The median TS/glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA ratio was 0.98 in primary tumors, 0.70 in liver metastases, 1.92 in lymph node metastases, and 3.42 in pulmonary metastases. A significantly higher expression of TS mRNA was observed in pulmonary and lymph node metastases compared with their respective primary tumors. In contrast, TS mRNA expression in hepatic metastases was significantly lower than in primary tumors. Similar results were observed in tumors obtained from the same patient. These results may explain the difference in the clinical response to 5-FU-based chemotherapy between various metastatic sites. The discordant TS expression between primary and metastatic tumors is a critical factor that must be taken into account when TS is being used as a predictive biomarker for the antitumor effect of 5-FU-based chemotherapy.

UFT plus leucovorin for metastatic colorectal cancer: Japanese experience.

In the United States and Europe, the combination of oral UFT plus leucovorin has been reported to produce objective responses and survival rates similar to those achieved with standard intravenous 5-fluorouracil plus leucovorin in patients with metastatic colorectal cancer, with reduced toxicity. However, because knowledge and experience with UFT plus leucovorin are relatively limited in Japan, we conducted a phase II study to evaluate the safety and efficacy of this combination in Japanese patients with metastatic colorectal cancer. For the purposes of this study, 20 patients received oral UFT 400 mg/m2/day in two divided doses (q 12 h) and a 5-mg tablet of leucovorin (q 8 h). Treatment was administered for 5 days, followed by a 2-day rest period, for a 28-day cycle. There were six partial responses (30%) and one complete response (5%) (overall response rate, 35%; 95% confidence interval, 14.1% to 55.9%). Greater efficacy of UFT plus leucovorin was demonstrated in patients with lung metastases, with a response rate of 63% (five of eight patients). Patients received a median of 4.5 courses (range, 2 to 12) of therapy. The median duration of survival was 228+ days (range, 81 to 540; six patients remain alive). Grade 3 or 4 toxicities occurred in three patients: diarrhea in two and mucositis in one. No toxicity-related hospitalization was reported. In summary, this combination showed promising activity and an acceptable toxicity profile in the treatment of Japanese patients with metastatic colorectal cancer.

[Dihydropyrimidine dehydrogenase gene expression in patients with hepatic metastases from colorectal cancer].

Dihydropyrimidine dehydrogenase (DPD) is the rate-limiting enzyme for 5-FU catabolism. Recently, much interest has been taken in the relation between the antitumor effect of 5-FU and DPD expression in gastrointestinal cancers. In this study, we compared DPD mRNA of 11 hepatic metastatic foci with that of 50 primary foci in colorectal cancer patients. DPD mRNA levels in hepatic metastatic foci were significantly higher than those in primary foci (median DPD/GAPDH ratio 0.79 vs 0.44, p = 0.035). Even in 6 cases available to compare DPD mRNA expression in matched primary and metastatic foci, the same significant difference was obtained (median DPD/GAPDH ratio 0.80 vs 0.36, p = 0.028). Our results suggested that the efficacy of intra-arterial infusion for metastatic liver tumor is mainly due to the fact that the high concentration of 5-FU is enough to overcome the high clearance of 5-FU, which is caused by DPD.

Relationship between intratumoral dihydropyrimidine dehydrogenase activity and gene expression in human colorectal cancer.

Dihydropyrimidine dehydrogenase (DPD) is the rate-limiting enzyme for 5-fluorouracil catabolism. In this study, both the enzymatic activity and mRNA level of DPD were estimated in the tumor tissue and adjacent normal mucosa of 51 patients with colorectal cancer. Although no significant difference in enzymatic activity was observed between tumor tissue and normal mucosa (70.4 and 70.7 pmol/min/mg protein, respectively), the mRNA level in normal mucosa was significantly higher than that in tumor tissue (1.37 and 0.39, respectively; P<0.01). A linear relationship was noted between DPD activity and the DPD mRNA level in cancerous tissue (r(s) = 0.714, P<0.001). Thus, the DPD mRNA level as determined by reverse transcription-PCR can be used to indicate the DPD activity of colorectal cancers.

Size- and invasion-dependent increase in cyclooxygenase 2 levels in human colorectal carcinomas.

Nonsteroidal anti-inflammatory drugs reduce the incidence and mortality of colorectal carcinoma. Their chemopreventive effects appear to be due to inhibition of cyclooxygenase (COX)-2. Here, we have studied the relationship between the COX-2 mRNA levels and pathological characteristics in 43 primary colorectal carcinomas. COX-2 levels were significantly higher in tumors with larger sizes and in those with deeper invasions but were not correlated with whether the patients had metastasis or not. These results suggest that larger carcinomas produce more COX-2 to support their own growth and that COX-2 inhibitors may be effective agents of carcinoma growth suppression.

[Intra-arterial injection therapy of mitoxantrone for locally advanced breast cancer].

Mitoxantrone (MIT) is a new anthraquinone anticancer agent. We treated 14 patients with locally advanced breast cancer, 3 of which were inflammatory breast cancers, by pre-operative arterial injection of MIT. The treatment protocol was MIT 12 mg/m2 injected into both the internal mammary and the subclavian arteries with oral administration of 5'-DFUR 1,200 mg/day for 20 days. After 2 courses, all tumors were decreased over 50% in size. Down-staging was obtained in all of 8 cases. Mastectomy could be carried out on all patients, without microscopically residual tumor cells. Preoperative arterial injection of MIT might be the treatment of choice for locally advanced breast cancer to perform down-staging, however the survival benefit has remained equivocal. These preliminary results are encouraging to further studies.

Ecological studies on reovirus pollution of rivers in Toyama Prefecture. II. Molecular epidemiological study of reoviruses isolated from river water.

In order to clarify the source of reovirus pollution in river water, comparative surveys have been carried out between reovirus isolates from river water and those from sewage, human or animal, by making use of the analysis of genomic RNA-migration pattern of reovirus in polyacrylamide gel electrophoresis (electropherotype). The strains of reovirus serotype 1 and 2 isolated from river water were classified into 3 and 9 electropherotypes, respectively, and 8 out of these 12 types were also found among strains isolated from sewage or human. When the monthly distribution of the river isolates classified by electropherotypes was compared with that of the sewage isolates, there were cases in which strains of the same electropherotype were simultaneously isolated from both sources. The electropherotypes of 3 isolates from pig and field rodents were different from those of the other isolates. The electropherotype of an oyster isolate coincided with that of some of the isolates from humans and river water. These results indicate that the major source of reoviruses polluting river water may be the human excretion.