While the association between fruit consumption and bladder cancer risk has been extensively reported, studies have had inadequate statistical power to investigate associations between types of fruit and bladder cancer risk satisfactorily. Fruit consumption in relation to bladder cancer risk was investigated by pooling individual data from 13 cohort studies. Cox regression models with attained age as time scale were used to estimate hazard ratios (HRs) for intakes of total fruit and citrus fruits, soft fruits, stone fruits, tropical fruits, pome fruits and fruit products. Analyses were stratified by sex, smoking status and bladder cancer subtype. During on average 11.2 years of follow-up, 2836 individuals developed incident bladder cancer. Increasing fruit consumption (by 100 g/day) was inversely associated with the risk of bladder cancer in women (HR = 0.92; 95% CI 0.85-0.99). Although in women the association with fruit consumption was most evident for higher-risk nonmuscle invasive bladder cancer (NMIBC; HR = 0.72; 95% CI 0.56-0.92), the test for heterogeneity by bladder cancer subtype was nonsignificant (P-heterogeneity = .14). Increasing fruit consumption (by 100 g/day) was not associated with bladder cancer risk in men (HR = 0.99; 95% CI 0.94-1.03), never smokers (HR = 0.96; 95% CI 0.88-1.05), former smokers (HR = 0.98; 95% CI 0.92-1.05) or current smokers (HR = 0.95; 95% CI 0.89-1.01). The consumption of any type of fruit was not found to be associated with bladder cancer risk (P values > .05). Our study supports no evidence that the consumption of specific types of fruit reduces the risk of bladder cancer. However, increasing total fruit consumption may reduce bladder cancer risk in women.
Genome instability is a prerequisite for the development of cancer. It occurs when genome maintenance systems fail to safeguard the genome's integrity, whether as a consequence of inherited defects or induced via exposure to environmental agents (chemicals, biological agents and radiation). Thus, genome instability can be defined as an enhanced tendency for the genome to acquire mutations; ranging from changes to the nucleotide sequence to chromosomal gain, rearrangements or loss. This review raises the hypothesis that in addition to known human carcinogens, exposure to low dose of other chemicals present in our modern society could contribute to carcinogenesis by indirectly affecting genome stability. The selected chemicals with their mechanisms of action proposed to indirectly contribute to genome instability are: heavy metals (DNA repair, epigenetic modification, DNA damage signaling, telomere length), acrylamide (DNA repair, chromosome segregation), bisphenol A (epigenetic modification, DNA damage signaling, mitochondrial function, chromosome segregation), benomyl (chromosome segregation), quinones (epigenetic modification) and nano-sized particles (epigenetic pathways, mitochondrial function, chromosome segregation, telomere length). The purpose of this review is to describe the crucial aspects of genome instability, to outline the ways in which environmental chemicals can affect this cancer hallmark and to identify candidate chemicals for further study. The overall aim is to make scientists aware of the increasing need to unravel the underlying mechanisms via which chemicals at low doses can induce genome instability and thus promote carcinogenesis.
Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical disruptors for all targets, this included dose-response characterizations, evidence of low-dose effects and cross-hallmark effects for all targets and chemicals. In total, 85 examples of chemicals were reviewed for actions on key pathways/mechanisms related to carcinogenesis. Only 15% (13/85) were found to have evidence of a dose-response threshold, whereas 59% (50/85) exerted low-dose effects. No dose-response information was found for the remaining 26% (22/85). Our analysis suggests that the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies. Additional basic research on carcinogenesis and research focused on low-dose effects of chemical mixtures needs to be rigorously pursued before the merits of this hypothesis can be further advanced. However, the structure of the World Health Organization International Programme on Chemical Safety 'Mode of Action' framework should be revisited as it has inherent weaknesses that are not fully aligned with our current understanding of cancer biology.