Environmental exposure to cadmium in breast cancer - association with the Warburg effect and sensitivity to tamoxifen

Effect of tobacco use on cadmium accumulation in the oral keratinized mucosa

BACKGROUND

This cross-sectional study aimed to evaluate the effect of tobacco use on the accumulation of cadmium (Cd), a carcinogenic element, in the oral keratinized mucosa (OKM).

METHODS

OKM samples were obtained by standard punch biopsy from nonsmokers (n = 19) and smokers (n = 21). Cd analysis was performed using inductively coupled plasma optical emission spectroscopy (ICP-OES). The calibration curve R2 values for three wavelengths (214,439, 226,502, and 228,802 nm) were at the level of 0.9999. The frequency of consumption of foods that are Cd sources, such as seafood, rice, and vegetables, was assessed in all patients. The age, sex, and nutritional habits of all patients and the frequency of tobacco consumption by smokers were recorded. The independent t-test, Mann-Whitney U test, Fisher's exact test, and Spearman correlation test were used for the statistical analyses, and p < 0.05 was considered significant.

RESULTS

Although the Cd levels in nonsmokers were higher than those in smokers, no statistically significant difference was found (p > 0.05). In smokers, a positive correlation was found between age and Cd level (r = 0.574, p = 0.006). No significant relationship was found between the groups in terms of nutrition or between the frequency of tobacco consumption and Cd accumulation.

CONCLUSION

The OKM may not have the characteristic cumulative accumulation in terms of toxic elements. Changes in the turnover rate, keratinization, and apoptotic mechanisms in the OKM with the thermal/chemical effects of tobacco may be responsible for the difference in Cd accumulation.

TRIAL REGISTRATION NUMBER

TCTR20230206001/06 Feb 2023 (TCTR: Thai Clinical Trials Registry).

Differential effect of the duration of exposure on the carcinogenicity of cadmium in MCF10A mammary epithelial cells

The carcinogenic role of cadmium (Cd2+) in breast cancer is still debatable. Current data points to duration of exposure as the most important element. In our study, we designed an in vitro model to investigate the effects of 3 weeks versus 6 weeks of low-level CdCl2 exposure on MCF10A cells. Our results demonstrated that after 3 weeks of CdCl2 exposure the cells displayed significant changes in the DNA integrity, but there was no development of malignant features. Interestingly, after 6 weeks of exposure, the cells significantly increased their invasion, migration and colony formation capacities. Additionally, MCF10A cells exposed for 6 weeks to CdCl2 had many dysregulated genes (4905 up-regulated and 4262 down-regulated). As follows, Cd-induced phenotypical changes are accompanied by a profound modification of the transcriptomic landscape. Furthermore, the molecular alterations driving carcinogenesis in MCF10A cells exposed to CdCl2 were found to be influenced by the duration of exposure, as in the case of MEG8. This long non-coding RNA was down-regulated at 3 weeks, but up-regulated at 6 weeks of exposure. In conclusion, even very low levels of Cd (0.5 μM) can have significant carcinogenic effects on breast cells in the case of subchronic exposure.