Calcium Intake Increases Risk of Prostate Cancer among Singapore Chinese
ABSTRACT Consumption of dairy products, the primary source of calcium in Western diets, has been found to be positively associated with prostate cancer. In an Asian diet, nondairy foods are the major contributors of calcium. Thus, a study of dietary calcium and prostate cancer in Asians can better inform on whether calcium, as opposed to other dairy components, is responsible for the dairy foods-prostate cancer association. We examined calcium intake and prostate cancer risk among 27,293 men in the Singapore Chinese Health Study that was established between 1993 and 1998. As of December 31, 2007, 298 incident prostate cancer cases had been diagnosed among the cohort members. Diet was assessed at baseline with a validated 165-item food-frequency questionnaire. It is hypothesized that there is greater net absorption of calcium in smaller individuals. Therefore, the calcium-prostate cancer association was also assessed in stratified analyses by median body mass index. Vegetables were the largest contributor of daily calcium intake in the study population. Overall, we observed a modest, statistically nonsignificant 25% increase in prostate cancer risk for the 4th (median = 659 mg/d) versus 1st (median = 211 mg/d) quartiles of calcium intake after adjustment for potential confounders. The association became considerably stronger and achieved statistical significance (hazard ratio, 2.03; 95% confidence interval, 1.23-3.34; P for trend = 0.01) for men with a below median body mass index (22.9 kg/m(2)). Dietary calcium might be a risk factor for prostate cancer even at relatively low intake.
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ABSTRACT: While patients with advanced prostate cancer initially respond favorably to androgen ablation therapy, most experience a relapse of the disease within 1-2 years. Although hormone-refractory disease is unresponsive to androgen-deprivation, androgen receptor (AR)-regulated signaling pathways remain active and are necessary for cancer progression. Thus, both AR itself and the processes downstream of the receptor remain viable targets for therapeutic intervention. Microarray analysis of multiple clinical cohorts showed that the serine/threonine kinase Ca2+/calmodulin-dependent protein kinase kinase β (CaMKKβ) is both highly expressed in the prostate and further elevated in prostate cancers. Using cellular models of prostate cancer, we have determined that androgens (a) directly increase the expression of a CaMKKβ splice variant and (b) increase functional CaMKKβ protein levels as determined by the phosphorylation of both CaMKI and AMP-activated protein kinase (AMPK), two of CaMKKβ's primary substrates. Importantly, inhibition of the CaMKKβ-AMPK, but not CaMKI, signaling axis in prostate cancer cells by pharmacological inhibitors or siRNA-mediated knockdown blocks androgen-mediated migration and invasion. Conversely, overexpression of CaMKKβ alone leads to both increased AMPK phosphorylation and cell migration. Given the key roles of CaMKKβ and AMPK in the biology of prostate cancer cells, we propose that these enzymes are potential therapeutic targets in prostate cancer.Cancer Research 01/2011; 71(2):528-37. DOI:10.1158/0008-5472.CAN-10-2581 · 9.28 Impact Factor
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ABSTRACT: To prospectively evaluate the associations of dietary calcium and magnesium intake with cancer incidence and mortality, data of 24,323 participants of the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Heidelberg), who were aged 35-64 years and cancer-free at recruitment (1994-1998), were analyzed using multivariate Cox regression models. After an average follow-up time of 11 years, 2,050 incident cancers were diagnosed and 513 cancer deaths occurred. Dietary calcium intake was inversely but not statistically significantly associated with colorectal cancer risk (hazard ratio [HR] for per 100 mg increase in intake: 0.95; 95% confidence interval [CI]: 0.88, 1.02) and lung cancer risk (HR for per 100 mg increase in intake: 0.94; 95% CI: 0.87, 1.02). No statistically significant associations were observed between dietary calcium intake and site-specific or overall cancer incidence or mortality. Dietary magnesium intake was not statistically significantly associated with any of the investigated outcomes. This prospective cohort study provides no strong evidence to support that high dietary calcium and magnesium intake in the intake range observed in a German population may reduce cancer incidence or mortality.Cancer Causes and Control 07/2011; 22(10):1375-82. DOI:10.1007/s10552-011-9810-z · 2.96 Impact Factor