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 pr imar ily 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 similar to 1.78). This association was more pronounced among women with a higher (OR = 5.82; 95% CI: 1.31 similar to 25.94) than a lower (OR = 0.73; 95% CI: 0.41 similar to 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 similar to 2.23). Conclusions: C. trachomatis infection may contribute to the development of hormone-responsive breast cancer in women with high levels of IL-12. Further studies are needed to uncover the underlying mechanisms.