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This study aimed to investigate the association between daily sedentary time and the risk of breast cancer (BC) in a large Japanese population. The participants were 36,023 women aged 35–69 years from the Japan Multi‐Institutional Collaborative Cohort Study. Cox proportional hazards analysis was used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for BC incidence in relation to time spent sedentarily (categorical variables: <7 and ≥7 hours/day [h/d]). Additionally, the associations of BC incidence to the joint effect of sedentary time with each component of physical activity, such as leisure‐time metabolic equivalents (METs), frequency of leisure‐time physical activity, and daily walking time, were examined. During 315,189 person‐years of follow‐up, 554 incident cases of BC were identified. When compared to participants who spent <7 h/d sedentary, those who spent ≥7 h/d sedentary have a significantly higher risk of BC (HR, 1.36; 95% CI, 1.07–1.71). The corresponding HRs among participants who spent ≥7 h/d sedentary with more physical activity, such as ≥1 h/d for leisure‐time METs, ≥3 days/week of leisure‐time physical activity, and ≥1 h/d of daily walking were 1.58 (95% CI, 1.11–2.25), 1.77 (95% CI, 1.20–2.61), and 1.42 (95% CI, 1.10–1.83), respectively, compared with those who spent <7 h/d sedentary. This study found that spending ≥7 h/d of sedentary time is associated with the risk of BC. Neither leisure‐time physical activity nor walking had a BC‐preventive effect in those with ≥7 h/d of sedentary time. [ABSTRACT FROM AUTHOR]

Protoporphyrin IX‐fluorescence measurement is a powerful in situ approach for cancer detection after oral/topical administration of 5‐aminolevulinic acid. However, this approach has not been clinically established for breast cancer, probably due to insufficient delivery of 5‐aminolevulinic acid to the mammary glands. In the present study, we directly exposed breast cancer cells to 5‐aminolevulinic acid to assess their discrimination via protoporphyrin IX‐fluorescence. Fluorescence intensity (FI) was measured in the human breast cancer cell lines MCF7 and MDA‐MB‐231 and breast epithelial cell line MCF10A by confocal microscopy and flow cytometry. After 5‐aminolevulinic acid exposure for 2 hours, protoporphyrin IX‐FI in MCF7 and MDA‐MB‐231 cells significantly increased with marked cell‐to‐cell variability, whereas that in MCF10A cells increased moderately. Combined exposure of the cancer cells to 5‐aminolevulinic acid and Ko143, a specific inhibitor of ATP‐binding cassette transporter G2, further increased protoporphyrin IX‐FI and alleviated the cell‐to‐cell variability in MCF7 and MDA‐MB‐231 cells, indicating improvement in the reproducibility and accuracy for fluorescence‐based cancer detection. The increased FI by combined administration of these two drugs was also demonstrated in cells obtained via fine needle aspiration from mouse xenograft models inoculated with MDA‐MB‐231 cells. Furthermore, a cutoff value for increased protoporphyrin IX‐FI ratio, before and after exposure to these drugs, clearly discriminated between cancer and noncancer cells. Taken together, direct exposure to 5‐aminolevulinic acid and Ko143 may be a promising strategy for efficient fluorescence‐based detection of breast cancer cells ex vivo using fine needle aspiration. [ABSTRACT FROM AUTHOR]