Association of CYP1B1 Polymorphisms with Breast Cancer: A Case-Control Study in the Han Population in Ningxia Hui Autonomous Region, P. R. China

Interleukin-6 selectively induces drug metabolism to potentiate the genotoxicity of dietary carcinogens in mammary cells

Breast cancer is the most commonly diagnosed malignancy in females, the etiology being multifactorial and includes the role of lifestyle exposure to DNA-damaging chemicals such as dietary carcinogens benzo (a) pyrene (BaP) and 2-amino-1-methyl-6-phenylimidazo [4, 5-b] pyridine (PhIP). Both compounds require cytochrome P450 (CYP)-mediated metabolic activation to DNA-damaging species, and both induce transcriptional responses through the nuclear receptors Aryl hydrocarbon receptor (AhR) and estrogen receptor α (ERα). BaP and PhIP are mammary carcinogens in rodents. Clinically, circulating IL-6 expression is linked with poor prognosis of cancer and 35% of the deaths in breast cancer are linked with inflammation. The objective of this work was to investigate the molecular toxicology and local activation of BaP and PhIP in the presence of IL-6. Our laboratory has previously reported that miR27b can regulate CYP1B1 expression in colorectal cells, here we have investigated if this mechanism is working in mammary cell models, MCF-7 and MDA-MB-231 cells. Treatment (24 h) of cells with BaP (10 nM-10 µM) and PhIP (100 nM-100 µM) significantly induced genetic damage (micronuclei formation) in a dose-dependent manner in both cell lines. This effect was potentiated in the presence of human IL-6 at concentrations reported to be expressed in clinical breast cancer. On its own, IL-6 treatment failed to induce micronuclei frequency above the control levels in these cells. Compared to BaP or PhIP treatment alone, IL-6 plus BaP or PhIP selectively induced CYP1B1 significantly in both cell lines. Additionally, miR27b expression was downregulated by IL-6 treatments and transfection with miR27b inhibitor confirmed that miR27b is a regulator of CYP1B1 in both cell lines. These data show that BaP- and PhIP-induced DNA damage in mammary cells is potentiated by the inflammatory cytokine IL-6 and that inflammation-induced CYP expression, specifically CYP1B1 via miR27b, is responsible for this effect.

Unifying mechanism in the initiation of breast cancer by metabolism of estrogen (Review)

Excessive exposure to estrogen is associated with increased risk of breast cancer. The mechanisms of carcinogenesis in the breast caused by estrogen metabolism include formation of depurinating adducts which are released from DNA to generate apurinic sites, and production of reactive oxygen species (ROS). Excess ROS not only exerts genotoxicity by indirectly increasing genomic instability, but also stimulates progression of mammary carcinogenicity by inducing a redox‑associated signaling pathway. Estrogen metabolism enzymes serve an important role in estrogen metabolism. Alterations in the expression and activity of estrogen metabolism enzymes may influence estrogen metabolism homeostasis. The present review discusses the process of estrogen metabolism, the role of estrogen metabolites and ROS in breast carcinogenesis, and the effect of metabolism enzyme polymorphisms on generation of pro‑carcinogens and breast cancer susceptibility.

Cytochrome P-450 1B1 Leu432Val Polymorphism Does Not Show Association With Breast Cancer in Northern Iranian Women With a History of Infertility

The Cytochrome P-4501B1 (CYP1B1) Leu432Val polymorphism has been previously shown to be associated with some types of cancer and affects CYP1B1-mediated metabolism of various infertility drugs. To establish the frequency of CYP1B1 Leu432Val polymorphism among women with a history of infertility drug use, we studied the genotypes of 147 patients with breast cancer with a history of infertility and 150 cancer-free, infertile women (control group) in Northern Iran. A polymerase chain reaction-based restriction fragment length polymorphism assay was used to detect GG (Val/Val), CG (Leu/Val), and CC (Leu/Leu) genotype frequencies, which did not vary significantly between the 2 patient groups (P = .847). We established for the first time that the incidence of CYP1B1 Leu432Val polymorphism is 46.6% among women with infertility history and breast cancer in Northern Iran. Finally, our results do not show any significant association between CYP1B1 Leu432Val polymorphism and breast cancer in infertile women in this region, who have also received infertility treatment.

Metformin Reverses Development of Pulmonary Hypertension via Aromatase Inhibition

Females are more susceptible to pulmonary arterial hypertension than males, although the reasons remain unclear. The hypoglycemic drug, metformin, is reported to have multiple actions, including the inhibition of aromatase and stimulation of AMP-activated protein kinase. Inhibition of aromatase using anastrazole is protective in experimental pulmonary hypertension but whether metformin attenuates pulmonary hypertension through this mechanism remains unknown. We investigated whether metformin affected aromatase activity and if it could reduce the development of pulmonary hypertension in the sugen 5416/hypoxic rat model. We also investigated its influence on proliferation in human pulmonary arterial smooth muscle cells. Metformin reversed right ventricular systolic pressure, right ventricular hypertrophy, and decreased pulmonary vascular remodeling in the rat. Furthermore, metformin increased rat lung AMP-activated protein kinase signaling, decreased lung and circulating estrogen levels, levels of aromatase, the estrogen metabolizing enzyme; cytochrome P450 1B1 and its transcription factor; the aryl hydrocarbon receptor. In human pulmonary arterial smooth muscle cells, metformin decreased proliferation and decreased estrogen synthesis by decreasing aromatase activity through the PII promoter site of Cyp19a1 . Thus, we report for the first time that metformin can reverse pulmonary hypertension through inhibition of aromatase and estrogen synthesis in a manner likely to be mediated by AMP-activated protein kinase.

Whole-exome sequencing reveals potential molecular predictors of relapse after discontinuation of the targeted therapy in chronic myeloid leukemia patients

Chronic myeloid leukemia (CML) is a myeloproliferative disease well treated by tyrosine kinase inhibitors (TKIs). The aim was to identify genes with a predictive value for relapse-free survival after TKI cessation in CML patients. We performed whole-exome sequencing of DNA from six CML patients in long-lasting deep molecular remission. Patients were divided into two groups with relapse (n = 3) and without relapse (n = 3) after TKI discontinuation. We found variants in genes CYP1B1, ALPK2, and IRF1 in group of patients with relapse and one variant in gene PARP9 in group of patients without relapse. We verified prognostic value of the found markers in a small group of patients with TKI discontinuation and demonstrated their high sensitivity (77%), specificity (86%), positive (85%), and negative (79%) predictive values. Thus we revealed genetic variants, which are potential markers of outcome prediction in CML patients after TKI discontinuation.

Polymorphisms of catechol estrogens metabolism pathway genes and breast cancer risk in Mexican women

Breast cancer is associated to estrogen exposure. Allelic variants involved in estrogen metabolism might change the risk of developing this neoplasia. We examined the potential association of breast cancer risk in Mexican women with the polymorphisms CYP1A1 rs1048943, CYP1B1 rs1056836, COMT rs4680, GSTP1 rs1695, GSTT1 null and GSTM1 null which are involved in estrogen metabolism pathway. This study included 150 cases and 150 controls. A significant association was observed between, CYP1A1 rs1048943 (OR = 1.95, C.I. 1.13-3.36) and GSTP1 rs1695 (OR = 2.39, C.I. 1.24-4.24) polymorphisms with the risk of breast cancer. This risk was increased when the women were stratified according to their menopausal status. The results show that breast cancer risk significantly increases in women with 3-6 risk polymorphisms (OR = 3.75, C.I. 1.44-9.74).