Association of Chlamydia trachomatis infection with breast cancer risk and the modification effect of IL-12

This study explored the link between Chlamydia trachomatis infection and breast cancer risk, focusing on modification effect of IL-12. Serum C. trachomatis IgG levels were analyzed in 1,121 breast cancer patients and 400 controls. The results suggest a potential association between C. trachomatis infection, high IL-12 levels, and hormone-responsive breast cancer risk. Background Chlamydia trachomatis (C. trachomatis) infection has been implicated in various cancers, yet its association with breast cancer remains unexplored. This infection triggers a cascade of immune responses primarily regulated by Interleukins-12 (IL-12). Thus, the objective of this case-control study was to investigate the link between C. trachomatis infection and breast cancer risk, as well as the modification effect of IL-12. Methods We assessed IgG levels against C. trachomatis in serum of 1,121 women with breast cancer (861 with estrogen receptor-positive (ER+) and 260 with estrogen receptor-negative (ER-) tumors) and 400 controls in Guangzhou, China. Logistic regression models were applied to estimate the odds ratios (ORs) and 95% confidence intervals (95% CIs) for breast cancer risk in association with C. trachomatis infection. The interaction between C. trachomatis infection and IL-12 on breast cancer risk was estimated by the product terms in the logistic regression models. Results Seropositivity of C. trachomatis IgG showed a slight association with an increased risk of breast cancer (OR=1.20; 95%CI: 0.86∼1.78). This association was more pronounced among women with a higher (OR=5.82; 95%CI: 1.31∼25.94) than a lower (OR=0.73; 95%CI: 0.41∼1.30) level of IL-12, with a statistically significant interaction observed (P interaction =0.013). In addition, C. trachomatis IgG seropositivity was related to an increased risk of breast cancer among PR+ patients (OR=1.53; 95%CI: 1.04∼2.23). Conclusions C. trachomatis infection may contribute to the development of hormone-responsive breast cancer, particularly for women with high levels of IL-12. Further exploration is needed to uncover the underlying mechanisms. Micro abstract This study explored the link between Chlamydia trachomatis infection and breast cancer risk, focusing on modification effect of IL-12. Serum C. trachomatis IgG levels were analyzed in 1,121 breast cancer patients and 400 controls. The results suggest a potential association between C. trachomatis infection, high IL-12 levels, and hormone-responsive breast cancer risk.