Yoichiro Kakugawa

Up-regulation of plasma membrane-associated ganglioside sialidase (Neu3) in human colon cancer and its involvement in apoptosis suppression

Human plasma membrane-associated sialidase (Neu3) is unique in specifically hydrolyzing gangliosides, thought to participate in cell differentiation and transmembrane signaling, thereby playing crucial roles in the regulation of cell surface functions. We have discovered levels of mRNA for this sialidase to be increased in restricted cases of human colon cancer by 3- to 100-fold compared with adjacent nontumor mucosa (n = 32), associated with significant elevation in sialidase activity in tumors (n = 50). In situ hybridization showed the sialidase expression in epithelial elements of adenocarcinomas. In cultured human colon cancer cells, the sialidase level was down-regulated in the process of differentiation and apoptosis induced by sodium butyrate, whereas lysosomal sialidase (Neu1) was up-regulated. Transfection of the sialidase gene into colon cancer cells inhibited apoptosis and was accompanied by increased Bcl-2 and decreased caspase expression. Colon cancer exhibited a marked accumulation of lactosylceramide, a possible sialidase product, and addition of the glycolipid to the culture reduced apoptotic cells during sodium butyrate treatment. These results indicate that high expression of the sialidase in cancer cells leads to protection against programmed cell death, probably modulation of gangliosides. This finding provides a possible sialidase target for diagnosis and therapy of colon cancer.

Therapeutic significance of palliative operations for gastric cancer for survival and quality of life.

Background and Objectives: There have been few reports on the objective assessment of quality of life (QOL) in patients with gastric cancer following palliative operations. The benefit of a palliative operation for survival and QOL of patients with gastric cancer is not clear.

Human sialidase as a cancer marker

Altered sialylation of cell surface glycoproteins and glycolipids is closely related to the malignant phenotype of cancer cells, including the metastatic potential and invasiveness. Many cancer‐related antigens in clinical use contain sialic acids at the terminal position of sugar chains in the molecules. To elucidate the molecular mechanism, we focused our investigation on sialidase, which catalyzes the removal of sialic acid residues from the glycoconjugates. Four types of human sialidases identified to date behave in different manners during carcinogenesis. One of the sialidases, found in the lysosomes, showed downregulation in cancers, promoting anchorage‐independent growth, and metastatic ability, while another, found in the plasma membrane, showed marked upregulation, causing apoptosis suppression. It was found that estimation of the mRNA levels of sialidases by real‐time PCR allowed discrimination of cancerous from noncancerous tissues and even determination of the pathological stage in some cancers. Immunohistochemistry of cancer tissues using the antibody against the plasma membrane sialidase was useful for clinical diagnosis. This paper briefly summarizes our findings of the altered sialidase expression in cancers and the possibility of their clinical application as cancer markers. Human sialidases are indeed related to malignancy and may be potential targets for cancer diagnosis and therapy.

Down-regulation of sialidase NEU4 may contribute to invasive properties of human colon cancers

In mammalian cells, four types of sialidase have been described and found to behave in different ways during carcinogenesis. We previously demonstrated that a human sialidase associated with plasma membranes (NEU3) is up‐regulated in human colon cancer and is involved in suppression of apoptosis. Here we document altered expression of another human sialidase, the recently identified NEU4, and evidence of its influence on the malignant phenotype in colon cancers. Human colon mucosa was relatively rich in NEU4, which has been observed to possess short and long isoforms, but hardly contained the latter form. In clear contrast to the NEU3 case, the levels of mRNA for this sialidase were found by quantitative RT‐PCR to be markedly decreased in colon cancers. In cultured human colon cancer cells, the enzyme was up‐regulated in the early stage of apoptosis induced by either the death ligand TRAIL or serum‐depletion, and transfection of NEU4 resulted in acceleration of apoptosis and in decreased invasion and motility. The siRNA‐mediated NEU4 targeting, on the other hand, caused a significant inhibition of apoptosis and promotion of invasion and motility. Lectin blot analyses revealed that desialylated forms of nearly 100 kDa glycoproteins were prominently increased with PNA in NEU4 transfectants, whereas only slight changes in glycolipids were detected as assessed by thin layer chromatography. These results suggest that NEU4 plays important roles for maintenance of normal mucosa mostly through desialylation of glycoproteins and that down‐regulation may contribute to invasive properties of colon cancers. (Cancer Sci 2007; 98: 299–307)

Adiposity, adult weight change and breast cancer risk in postmenopausal Japanese women: the Miyagi Cohort Study.

Background:The role of adult weight change in breast cancer (BC) risk is unclear in Japanese women.Methods:A total of 10 106 postmenopausal women aged 40–64 years (the Miyagi Cohort) were followed from 1990 to 2003, and 108 BC cases were identified. Hazard ratios (HRs) were estimated according to body mass index (BMI) at the current age and at the of age 20 years, and weight change since age 20 years.Results:Higher current BMI was associated with an increased risk of BC (P for trend=0.02), whereas higher BMI at the age 20 years was inversely associated with this risk (P for trend=0.002). There was a significant association between weight change since age 20 years and BC risk (P for trend=0.0086). Compared with stable weight, HR was 0.35 for weight loss of 5 kg or more (P for weight loss trend=0.04) and 1.55 for weight gain of 12 kg or more (P for weight gain trend=0.05).Conclusion:Adiposity at younger and current age has differential effects on BC risk among postmenopausal women; weight gain in adulthood being associated with an increased, and weight loss with a decreased risk.

Body mass index and survival after breast cancer diagnosis in Japanese women

BackgroundBody mass index (BMI) may be an important factor affecting breast cancer outcome. Studies conducted mainly in Western countries have reported a relationship between higher BMI and a higher risk of all-cause death or breast cancer-specific death among women with breast cancer, but only a few studies have been reported in Japan so far. In the present prospective study, we investigated the associations between BMI and the risk of all-cause and breast cancer-specific death among breast cancer patients overall and by menopausal status and hormone receptor status.MethodsThe study included 653 breast cancer patients admitted to a single hospital in Japan, between 1997 and 2005. BMI was assessed using a self-administered questionnaire. The patients were completely followed up until December, 2008. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated according to quartile points of BMI categories, respectively: <21.2, ≥21.2 to <23.3 (reference), ≥23.3 to <25.8 and ≥25.8 kg/m2.ResultsDuring the follow-up period, 136 all-cause and 108 breast cancer-specific deaths were observed. After adjustment for clinical and confounding factors, higher BMI was associated with an increased risk of all-cause death (HR = 2.61; 95% CI: 1.01–6.78 for BMI ≥25.8 vs. ≥21.2 to <23.3 kg/m2) among premenopausal patients. According to hormonal receptor status, BMI ≥25.8 kg/m2 was associated with breast cancer-specific death (HR = 4.95; 95% CI: 1.05–23.35) and BMI <21.2 kg/m2 was associated with all-cause (HR = 2.91; 95% CI: 1.09–7.77) and breast cancer-specific death (HR = 7.23; 95% CI: 1.57–33.34) among patients with ER + or PgR + tumors. Analysis by hormonal receptor status also showed a positive association between BMI and mortality risk among patients with ER + or PgR + tumors and with BMI ≥21.2 kg/m2 (p for trend: 0.020 and 0.031 for all-cause and breast cancer-specific death, respectively).ConclusionsOur results suggest that both higher BMI and lower BMI are associated with an increased risk of mortality, especially among premenopausal patients or among patients with hormonal receptor positive tumors. Breast cancer patients should be informed of the potential importance of maintaining an appropriate body weight after they have been diagnosed.

Increased androgen receptor activity and cell proliferation in aromatase inhibitor-resistant breast carcinoma

Aromatase inhibitors (AI) are commonly used to treat postmenopausal estrogen-receptor (ER)-positive breast carcinoma. However, resistance to AI is sometimes acquired, and the molecular mechanisms underlying such resistance are largely unclear. Recent studies suggest that AI treatment increases androgen activity during estrogen deprivation in breast carcinoma, but the role of the androgen receptor (AR) in breast carcinoma is still a matter of controversy. The purpose of this study is to examine the potential correlation between the AR- and AI-resistant breast carcinoma. To this end, we performed immunohistochemical analysis of 21 pairs of primary breast carcinoma and corresponding AI-resistant recurrent tissue samples and established two stable variant cell lines from ER-positive T-47D breast carcinoma cell line as AI-resistance models and used them in in vitro experiments. Immunohistochemical analysis demonstrated that the expression of prostate-specific antigen (PSA) and Ki-67 were significantly higher and ER and progesterone receptor (PR) were lower in recurrent lesions compared to the corresponding primary lesions. Variant cell lines overexpressed AR and PSA and exhibited neither growth response to estrogen nor expression of ER. Androgen markedly induced the proliferation of these cell lines. In addition, the expression profile of androgen-induced genes was markedly different between variant and parental cell lines as determined by microarray analysis. These results suggest that in some cases of ER-positive breast carcinoma, tumor cells possibly change from ER-dependent to AR-dependent, rendering them resistant to AI. AR inhibitors may thus be effective in a selected group of patients.

Mitotic Index Is the Best Predictive Factor for Survival of Patients with Resected Hepatocellular Carcinoma

Background: In patients with hepatocellular carcinoma (HCC), tumor recurrence is not infrequent after resection. It is presumed that characteristics of the tumor such as cellular malignancy might influence the prognosis of the patients in association with tumor stage and radicality of the procedure. Methods: Univariate and multivariate analyses were used to retrospectively determine the clinicopathologic factors potentially related to survival in 40 patients who underwent hepatectomy for HCC. Results: In univariate analysis, tumor stage I or II, mitotic index of 4 or less/10 random high-power fields, solitary tumor, and curative resection were significantly correlated with better survival. In multivariate analysis, the mitotic index and surgical curability were independently significant variables influencing survival of patients, and the mitotic index was the best predictive factor. A highly significant correlation was found between the mitotic index and Ki-67 labeling index. Compared to tumors with a mitotic index of 4 or less, those with a mitotic index of 5 or more had a higher association with multiple tumors and advanced tumor stage, which preclude curative resection. Conclusion: Analysis of the mitotic index is quite simple, and the mitotic index could be a useful factor for predicting the long-term survival of patients with HCC following hepatic resection.

Prediction of recurrence and extratumor spread of hepatocellular carcinoma following resection

The prognosis of patients with hepatocellular carcinoma (HCC) undergoing hepatectomy depends mostly on tumor recurrence. Portal vein invasion (Vp) and intrahepatic metastasis (IM) might strongly reflect the invasiveness of HCC, but the number of patients in the present series in whom either of these factors were detected was small. In this study, we defined Vp and IM as the extratumor spread, and we focused on the relationship between recurrence in patients after hepatectomy and the extratumor spread and the mitotic activities of cancer cells, in the hope that careful monitoring of recurrence might be possible by simply analyzing histology of the resected specimens.

Abrogation of protein phosphatase 6 promotes skin carcinogenesis induced by DMBA

Somatic mutations in the gene encoding the catalytic subunit of protein phosphatase 6 (Ppp6c) have been identified in malignant melanoma and are thought to function as a driver in B-raf- or N-ras-driven tumorigenesis. To assess the role of Ppp6c in carcinogenesis, we generated skin keratinocyte-specific Ppp6c conditional knockout mice and performed two-stage skin carcinogenesis analysis. Ppp6c deficiency induced papilloma formation with 7,12-dimethylbenz (a) anthracene (DMBA) only, and development of those papillomas was significantly accelerated compared with that seen following DMBA/TPA (12-O-tetradecanoylphorbol 13-acetate) treatment of wild-type mice. NF-κB activation either by tumor necrosis factor (TNF)-α or interleukin (IL)-1β was enhanced in Ppp6c-deficient keratinocytes. Overall, we conclude that Ppp6c deficiency predisposes mice to skin carcinogenesis initiated by DMBA. This is the first report showing that such deficiency promotes tumor formation in mice.