Diabetes mellitus and the risk of cancer: results from a large-scale population-based cohort study in Japan

Peroxisome proliferator-activated receptor gamma agonists inhibit the proliferation and invasion of human colon cancer cells

BACKGROUND AND AIMS

Data regarding the effect of peroxisome proliferator-activated receptor gamma (PPAR-gamma) ligands on the invasive ability of colon cancer cells are currently limited. This study was designed to examine the effects of PPAR-gamma agonists on the proliferation and invasion of two colon cancer cells to identify the role of PPAR-gamma in colon cancer growth and metastasis.

METHODS

SW480 and LS174T cells were treated with PPAR-gamma ligands, pioglitazone and 15-deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2), as well as their combinations with the PPAR-gamma antagonist GW9662. MTT assay was used to determine the antiproliferative effects. Cell cycle analysis was conducted by flow cytometry. The mRNA and protein expression were detected by reverse transcriptase polymerase chain reaction (RT-PCR) and western blot, respectively. The invasive ability of cells was determined by the BD BioCoat Matrige invasion chamber.

RESULTS

Pioglitazone and 15d-PGJ2 inhibited the proliferation of both colon cancer cell lines in a dose-dependent manner. This growth inhibitory effect was reversed by GW9662. Results from flow cytometry demonstrated G1 arrest following treatment with pioglitazone and 15d-PGJ2. The expression of matrix metalloproteinase-7 (MMP-7) was only detected in LS174T cells, while its tissue inhibitor-1 (TIMP-1) was expressed in both colon cancer cells. 15d-PGJ2 and pioglitazone downregulated MMP-7 expression and upregulated TIMP-1 expression. PPAR-gamma agonists can only inhibit invasive activity of LS174T cells.

CONCLUSIONS

PPAR-gamma agonists have inhibitory effects on the proliferation of colon cancer cell lines associated with G1 cell cycle arrest and invasive activity. The latter effect is demonstrated in certain cell lines through the down-regulation of MMP-7 synthesis.

Use of warfarin and risk of urogenital cancer: a population-based, nested case-control study

BACKGROUND

Indirect evidence suggests that prolonged treatment with warfarin might be associated with a decreased incidence of urogenital cancer. We aimed to assess this association in a large population-based study.

METHODS

Beneficiaries of Saskatchewan Health who were eligible for prescription drug benefits and aged 50 years or over with no history of cancer since 1967 were enrolled into a nested, matched case-control study. 19 412 new cases of urogenital cancer diagnosed between Jan 1, 1981, and Dec 31, 2002, were identified by use of information from the Saskatchewan Cancer Agency registry. For each case, six controls, totalling 116 470, who were matched for age, sex, and time of diagnosis were selected randomly. Conditional logistic regression analysis was used to calculate adjusted incidence rates of urogenital cancer in relation to warfarin use.

FINDINGS

Compared with men who never used warfarin, men with 4 years of warfarin use had an adjusted incidence rate of 0.80 (95% CI [0.65-0.99]). For warfarin use 76-100% of the time, the adjusted rate ratios were 0.80 (0.66-0.96) during year 2 preceding diagnosis of prostate cancer, 0.76 (0.62-0.94) during year 3, and 0.67 (0.53-0.86) during year 4. No significant association was found between warfarin and risk of other urogenital cancers.

INTERPRETATION

Our results suggest that warfarin has an antitumour effect that is specific to prostate cancer. Further investigation, with more complete assessment of confounders and that addresses the effect of warfarin on mortality of prostate cancer, is warranted.

Coffee consumption and risk of colorectal cancer in a population-based prospective cohort of Japanese men and women

We prospectively examined the association between coffee consumption and the risk of developing colorectal cancer in a large population-based cohort study (the JPHC Study) of Japanese men and women. Data were analyzed from a population-based cohort of 96,162 subjects (46,023 men and 50,139 women). A total of 1,163 incident colorectal cancers were identified during the follow-up period, including 763 cases of colon cancer and 400 of rectal cancer. We observed a significant inverse association between coffee consumption and the risk of developing invasive colon cancer among women. Compared with those who almost never consumed coffee, women who regularly consumed 3 or more cups of coffee per day had a RR of 0.44 (95% CI = 0.19-1.04; p for trend = 0.04) after adjustment for potential confounding factors. However, no significant association was found for rectal cancer in women. In men, no significant decrease was observed in any colorectal cancer site. Further, additional analyses on the association of green tea consumption with colorectal cancer risk found no significant association in men or women. These findings suggest that coffee consumption may lower the risk of colon cancer among Japanese women.

Diabetes mellitus and risk of breast cancer: A meta-analysis

Diabetes mellitus has been associated with an increased risk of several types of cancers, but its relationship with breast cancer remains unclear. We conducted a meta-analysis of case-control and cohort studies to assess the evidence regarding the association between diabetes and risk of breast cancer. Studies were identified by searching MEDLINE (1966-February 2007) and the references of retrieved articles. We identified 20 studies (5 case-control and 15 cohort studies) that reported relative risk (RR) estimates (odds ratio, rate ratio/hazard ratio, or standardized incidence ratio) with 95% confidence intervals (CIs) for the relation between diabetes (largely Type II diabetes) and breast cancer incidence. Summary RRs were calculated using a random-effects model. Analysis of all 20 studies showed that women with (versus without) diabetes had a statistically significant 20% increased risk of breast cancer (RR, 1.20; 95% CI, 1.12-1.28). The summary estimates were similar for case-control studies (RR, 1.18; 95% CI, 1.05-1.32) and cohort studies (RR, 1.20; 95% CI, 1.11-1.30). Meta-analysis of 5 cohort studies on diabetes and mortality from breast cancer yielded a summary RR of 1.24 (95% CI, 0.95-1.62) for women with (versus without) diabetes. Findings from this meta-analysis indicate that diabetes is associated with an increased risk of breast cancer.