Purpose Women with type 2 diabetes mellitus (T2DM) have an increased risk of breast cancer. We aimed to determine the contribution of lipids, glucose and blood pressure to this risk based on the multifactorial nature of T2DM. Patients and Methods This population-based cohort study used data from a Dutch database (the Groningen Initiative to Analyse Type 2 Diabetes Treatment) for the period 2004–2013. The cohort included women diagnosed with T2DM, aged 30–80 years, with no history of breast cancer and with follow-up data for at least 1 year. We used Cox proportional hazards models to estimate the associations of exposures with breast cancer occurrence, reporting adjusted hazard ratios (aHR) with 95% confidence intervals (CI). Exposures of interest included total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides, glycated hemoglobin A (HbA1c) and systolic blood pressure (SBP). Results During a median of 4.45 years’ follow-up, 183 of 10,183 included women received a breast cancer diagnosis. We observed U-shaped associations with breast cancer incidence for total cholesterol and HDL-C at baseline. Compared with moderate elevations, women had significantly higher breast cancer risks associated with high total cholesterol (aHR, 95% CI: 1.72, 1.15–2.55) and HDL-C (aHR, 95% CI: 1.74, 1.18–2.58) levels, while low total cholesterol (aHR, 95% CI: 1.43, 0.94–2.19) and HDL-C (aHR, 95% CI: 1.44, 0.95–2.17) levels produced marginal effects without significance. Women with high LDL-C levels more often received a breast cancer diagnosis than those with medium levels (aHR, 95% CI: 1.56, 1.03–2.35). Conclusion This real-world dataset highlights the importance of balancing lipid profiles, particularly total cholesterol and HDL-C. Dysregulation of the lipid profile, not the glucose or blood pressure profiles, may increase the risk of breast cancer in women with T2DM.

Purpose: Forkhead box C1 (FOXC1) may act as a therapeutic target for triple-negative breast cancer (TNBC) but without a comprehensive understanding of its regulations, especially at the upstream. L1 cell adhesion molecule (L1CAM) is a transmembrane glycoprotein that may involve in brain metastasis. Indicated by a positive correlation between FOXC1 and L1CAM transcripts, this study aims to further examine their relation in the process of TNBC. Methods: FOXC1 and L1CAM transcripts were downloaded fromtwo public datasets, and their proteins were examined in four TNBC cell lines. FOXC1 and L1CAM were separately knocked down in BT549 cells; L1CAM was overexpressed in BT549-shFOXC1, MDA-MB-231, and HCC1937 cells. CCK-8, transwell and wound healing assays were conducted in these cells, so was immunohistochemical staining in tumors. Results: L1CAM and FOXC1 transcripts were positively correlated in public datasets. BT549-shFOXC1 cells showed a decreased L1CAM expression both at the transcriptional and protein levels. Intriguingly, BT549-siL1CAM cells displayed decreased FOXC1 proteins, but exerted little effect on FOXC1 transcripts. Conversely, overexpression of L1CAM resulted in upregulation of FOXC1 protein without substantial change in FOXC1 mRNA, that consistently observedin BT549-shFOXC1, MDA-MB-231-L1CAM and HCC1937-L1CAM cells. Additionally, decreased or increased capacities of cell proliferation, migration, and invasion were seen along with down- or up-regulation of FOXC1 or L1CAM. Finally, a positive correlation between L1CAM and FOXC1 proteins was observed in human TNBC tumors. Conclusion:FOXC1 and L1CAM display coregulation at the protein level but not mRNA level to positively affect cell proliferation, migration and invasion in TNBC.