Effect of Aspirin on Cancer Chemoprevention in Japanese Patients With Type 2 Diabetes: 10-Year Observational Follow-up of a Randomized Controlled Trial

OBJECTIVE

This study analyzed the efficacy of low-dose aspirin in cancer chemoprevention in patients with diabetes.

RESEARCH DESIGN AND METHODS

This study was a posttrial follow-up of the Japanese Primary Prevention of Atherosclerosis with Aspirin for Diabetes (JPAD) trial. Participants in the JPAD trial (2,536 Japanese patients with type 2 diabetes and without preexisting cardiovascular disease) were randomly allocated to receive aspirin (81 or 100 mg daily) or no aspirin. After that trial ended in 2008, we followed up with the participants until 2015, with no attempt to change the previously assigned therapy. The primary end point was total cancer incidence. We investigated the effect of low-dose aspirin on cancer incidence.

RESULTS

During the median follow-up period of 10.7 years, a total of 318 cancers occurred. The cancer incidence was not significantly different between the aspirin and no-aspirin groups (log-rank, P = 0.4; hazard ratio [HR], 0.92; 95% CI, 0.73-1.14; P = 0.4). In subgroup analyses, aspirin did not affect cancer incidence in men, women, or participants aged ≥65 years. However, it decreased cancer incidence in participants aged <65 years (log-rank, P = 0.05; HR, 0.67; 95% CI, 0.44-0.99; P = 0.048). After adjusting for sex, hemoglobin A_1c, smoking status, and administration of metformin and statins, aspirin significantly reduced cancer incidence in participants aged <65 years (adjusted HR, 0.66; 95% CI, 0.43-0.99; P = 0.04).

CONCLUSIONS

Low-dose aspirin did not reduce cancer incidence in Japanese patients with type 2 diabetes.

Effects of hydroxyl radicals on KATP channels in guinea-pig ventricular myocytes

We studied the effects of oxygen free radicals on the ATP-sensitive potassium channel (KATP channel) of guinea-pig ventricular myocytes. Single KATP channel currents were recorded from inside-out patches in the presence of symmetrical K+ concentrations (140 mM in both bath and pipette solutions). Reaction of xanthine oxidase (0.1 U/ml) on hypoxanthine (0.5 mM) produced superoxide anions (.O2-) and hydrogen peroxide (H2O2). Exposure of the patch membrane to.O2- and H2O2 increased the opening of KATP channels, but this activation was prevented by adding 1 microM glibenclamide to the bath solution. In the presence of ferric iron (Fe3+: 0.1 mM), the same procedure produced hydroxyl radicals (.OH) via the iron-catalysed Haber-Weiss reaction.OH also activated KATP channels; however, this activation could not be prevented by, even very high concentrations of glibenclamide (10 microM). These different effects of glibenclamide suggest that the mode of action of these oxygen free radicals on KATP channels is different and that.OH is more potent than.O2-/H2O2 in activating KATP channels in the heart.

Openings of cardiac KATP channel by oxygen free radicals produced by xanthine oxidase reaction

We examined the effects of oxygen free radicals (OFRs) on action potentials and membrane currents of guinea pig ventricular myocytes. OFRs produced biphasic changes in the action potential duration, initial lengthening (30 s after exposure to OFRs) and subsequent shortening (within 5 min). In voltage-clamp experiments, OFRs suppressed the L-type calcium current, the delayed rectifier K+ current, and the inward rectifier K+ current. In addition, OFRs increased the time-independent outward current (I(term)) at potentials greater than -30 mV. The increases in I(term) reflected activation of the ATP-sensitive K+ (KATP) channels, as glibenclamide (1 microM) blocked this current. In inside-out patches, OFRs significantly increased the open probability of the channel at a relatively narrow range of ATP concentrations (0.2-2 mM), and this effect was enhanced in the presence of ADP (0.1 mM) and abolished in the presence of either free radical scavengers or gliben-clamide. These findings are compatible with the notion that OFRs activate KATP channels by modulating ATP binding sites of the KATP channels, without affecting ADP binding or glibenclamide binding sites.

[Clinical studies of 16 cases of carcinomatous pericarditis]

We studied the effects of local therapy on cardiac tamponade caused by carcinomatous pericarditis in 16 cases. Five out of 16 cases (drainage group) received treatment by only drainage of pericardial effusion, and the remaining 11 cases (infusion group) had local infusion of antineoplastic agents into the pericardium after drainage. The median survival time was 16 weeks in the infusion group and 19 weeks in the drainage group. There was no statistically significant difference. Reaccumulation of pericardial effusion was recognized in 3 patients in the drainage group (60%), and in 3 patients in the infusion group (18%). Our conclusion was that local infusion had no effect on prolongation of the survival time, but had a suppressive effect on reaccumulation of pericardial effusion.