This study aims to investigate the effect of transmembrane protein angiotensin converting enzyme 2 (ACE2) on the prognosis of breast cancer and its potential mechanism.Public databases were used to analyze ACE2 expression and its relationship with clinicopathological features and prognosis of breast cancer patients, combined with in vitro experiments to analyze the mechanism of action and immune relevance of ACE2 in breast cancer.Results showed that the expression of ACE2 in breast cancer tissues was significantly lower than that in normal breast tissues, and that its expression was negatively correlated with age, M stage and N1mi stage of breast cancer patients (P < 0.05).Patients with Luminal type breast cancer with high ACE2 expression had poor prognosis, while in the triple-negative breast cancer (TNBC) subtype, ACE2 showed different prognostic significance.In addition, ACE2 is closely associated with the metabolic and immune microenvironment of tumor tissue.In vitro experiments have shown that ACE2 is lowly expressed in MDA-MB-231 cells and may inhibit cell progress by downregulating matrix metalloproteinase 2（MMP2）.The results suggest that the low expression of ACE2 in breast cancer is closely associated with patient prognosis as well as metabolic and immune microenvironment, and that ACE2 may inhibit TNBC cell progress through the MMP2 pathway.

Objective:To evaluate the treatment persistence and long-time safety of infliximab (IFX) in the real-world in Chinese patients with Crohn′s disease (CD).Methods:From January 2009 to December 2021, at Sir Run Run Shaw Hospital, School of medicine, Zhejiang University, the clinical data of 1 309 patients with CD and treated with IFX were retrospectively analyzed, which included baseline data (gender, age at diagnosis, follow-up time, etc.), usage of IFX (the duration of treatment and situation of discontinuation) and adverse effects of IFX. Kaplan-Meier method was used to calculate the rate of consistent use of IFX and Cox regression was performed to analyze the influencing factors of treatment persistence. The chi-square test was used to analyze the associations between different factors and safety outcomes.Results:Among 1 309 patients, 936 (71.5%) were male, age at diagnosis was 28.7 years (28.1 years, 29.3 years). The follow-up time was 3.9 years (3.7 years, 4.0 years). The longest time of IFX treatment was 9.4 years. During the follow-up period, a total of 421 (32.2%) patients discontinued use of IFX and the sustained use of IFX at year 1, 3, 5 and 10 were 84.0%, 65.8%, 56.7% and 30.9% respectively. The results of Cox regression analysis revealed that patients with perianal lesions had an increased rate of sustained use of IFX ( HR(95% confidence interval) 0.75 (0.61, 0.92), P=0.006), while patients with adverse reactions had a decreased rate of sustained use of IFX ( HR(95% confidence interval) 1.23(1.01, 1.50), P=0.038). A total of 445 patients experienced adverse events, with an incidence rate of 34.0% (445/1 309). The acute infusion reaction was the most common side with an incidence rate of 13.7% (179/1 309), of which the rate of severe acute infusion reaction was 2.8% (5/1 309). The rate of infection was 10.5% (138/1 309), among which the rate of severe infection was 2.6% (34/1 309), and the rate of special pathogens infection was 5.5% (72/1 309). The rate of tuberculosis infection was 1.0% (13/1 309), and the most common affected site was the lungs (10 cases). The incidence of skin lesions (non-allergic, non-infectious and non-tumor skin) was 6.9% (90/1 309). The incidence of tumor was 1.1% (14/1 309). Patients who discontinued IFX due to adverse reactions accounted for 20.7% (92/445) of the patients with adverse reactions, among them patients who discontinued IFX due to acute infusion reaction, infections, neoplasms, delayed infusion reaction, skin lesions, abnormal liver function, hematological disorder, acute pancreatitis, joint pain and seizure accounted for 47.8% (44/92), 18.5% (17/92), 8.7% (8/92), 6.5% (6/92), 5.4% (5/92), 5.4% (5/92), 3.3% (3/92), 2.2% (2/92), 1.1% (1/92) and 1.1% (1/92), respectively. Among 14 patients with tumor, 11 were malignant tumors, 1 case of chronic leukemia was related with IFX. Multi-round of IFX treatment increased the risk of acute infusion reaction and severe acute infusion reaction, combination of immunosuppressants decreased the risk of liver injury, and IFX treatment for more than 1 year increased the risk of skin lesions ( χ2=6.16, 11.30, 18.20 and 9.47; P=0.013, =0.001, <0.001, =0.002). Conclusions:The rate of constant use of IFX is relatively high in Chinese Crohn′s disease patients. The long-term safety is good. Clinicians should pay more attention on the safety of patients receiving multiple rounds and long courses of IFX treatment.