BackgroundBreast cancer (BrCa) is a complex disease driven by aberrant gene alterations and environmental factors. Recent studies reveal that abnormal epigenetic gene regulation also plays an important role in its pathogenesis. Ubiquitin carboxyl- terminal esterase L1 (UCHL1) is a tumor suppressor silenced by promoter methylation in multiple cancers, but its role and alterations in breast tumorigenesis remain unclear.Methodology/Principal FindingsWe found that UCHL1 was frequently downregulated or silenced in breast cancer cell lines and tumor tissues, but readily expressed in normal breast tissues and mammary epithelial cells. Promoter methylation of UCHL1 was detected in 9 of 10 breast cancer cell lines (90%) and 53 of 66 (80%) primary tumors, but rarely in normal breast tissues, which was statistically correlated with advanced clinical stage and progesterone receptor status. Pharmacologic demethylation reactivated UCHL1 expression along with concomitant promoter demethylation. Ectopic expression of UCHL1 significantly suppressed the colony formation and proliferation of breast tumor cells, through inducing G0/G1 cell cycle arrest and apoptosis. Subcellular localization study showed that UCHL1 increased cytoplasmic abundance of p53. We further found that UCHL1 induced p53 accumulation and reduced MDM2 protein level, and subsequently upregulated the expression of p21, as well as cleavage of caspase3 and PARP, but not in catalytic mutant UCHL1 C90S-expressed cells.Conclusions/SignificanceUCHL1 exerts its tumor suppressive functions by inducing G0/G1cell cycle arrest and apoptosis in breast tumorigenesis, requiring its deubiquitinase activity. Its frequent silencing by promoter CpG methylation may serve as a potential tumor marker for breast cancer.

No abstract

IntroductionAberrant activation of Wnt/β-catenin signaling plays an important role in the pathogenesis of breast cancer. DACT1 (Dapper/Frodo) has been identified as involved in antagonizing Wnt/β-catenin signaling through interacting with Dishevelled (Dvl), a central mediator of Wnt signaling, whereas its role in breast tumorigenesis remains unclear.MethodsWe examined DACT1 expression in breast cancer cell lines and primary tumors with semiquantitative or quantitative RT-PCR and immunochemistry, and further evaluated the promoter methylation of DACT1 with methylation-specific PCR (MSP). We also explored the tumor-suppressive functions of DACT1 in vivo and in vitro, and its related mechanism in breast cancer.ResultsWe identified DACT1 as a methylated target in our breast cancer epigenome study. Here, we further investigated DACT1 expression in multiple breast cell lines and primary tumors, and further studied its function and molecular mechanisms. We found that DACT1 expression was silenced in eight (88.9%) of nine breast cancer cell lines, and its protein levels were obviously reduced in breast tumors compared with paired surgical-margin tissues. Promoter CpG methylation of DACT1 was detected in five (55.6%) of nine breast cancer cell lines and 40 (29.9%) of 134 primary tumors, but not in surgical-margin tissues and normal breast tissues. Demethylation treatment of breast cancer cell lines restored DACT1 expression along with promoter demethylation, suggesting that an epigenetic mechanism mediates DACT1 silencing in breast cancer. Functional assays showed that ectopic expression of DACT1 could inhibit breast tumor cell proliferation in vivo and in vitro through inducing apoptosis, and further suppress tumor cell migration through antagonizing the Wnt/β-catenin signaling pathway.ConclusionsOur study demonstrates that DACT1 could function as a tumor suppressor but was frequently downregulated in breast cancer.

No abstract

No abstract

Dickkopf-related protein 3 (DKK3) is an antagonist of Wnt ligand activity. Reduced DKK3 expression has been reported in various types of cancers, but its functions and related molecular mechanisms in breast tumorigenesis remain unclear. We examined the expression and promoter methylation of DKK3 in 10 breast cancer cell lines, 96 primary breast tumours, 43 paired surgical margin tissues and 16 normal breast tissues. DKK3 was frequently silenced in breast cell lines (5/10) by promoter methylation, compared with human normal mammary epithelial cells and tissues. DKK3 methylation was detected in 78% of breast tumour samples, whereas only rarely methylated in normal breast and surgical margin tissues, suggesting tumour-specific methylation of DKK3 in breast cancer. Ectopic expression of DKK3 suppressed cell colony formation through inducing G0/G1 cell cycle arrest and apoptosis of breast tumour cells. DKK3 also induced changes of cell morphology, and inhibited breast tumour cell migration through reversing epithelial-mesenchymal transition (EMT) and down-regulating stem cell markers. DKK3 inhibited canonical Wnt/β-catenin signalling through mediating β-catenin translocation from nucleus to cytoplasm and membrane, along with reduced active-β-catenin, further activating non-canonical JNK signalling. Thus, our findings demonstrate that DKK3 could function as a tumour suppressor through inducing apoptosis and regulating Wnt signalling during breast tumorigenesis.

Chrysin, a naturally occurring flavone, has been shown to inhibit cell proliferation and induce cell apoptosis in various cancers. However, the effect and mechanisms of chrysin on cancer metastasis are still enigmatic. In this study, metastatic triple-negative breast cancer (TNBC) cell lines were used to evaluate the antimetastatic activity of chrysin. The results showed that chrysin (5, 10 and 20 μM) significantly suppressed TNBC cell migration and invasion in a dose-dependent manner. Human matrix metalloproteinase (MMP) antibody array demonstrated that MMP-10 was downregulated by chrysin, which was further verified by Western blotting and ELISA. Moreover, it was shown that chrysin induced increased E-cadherin expression and decreased expression of vimentin, snail and slug in TNBC cells, suggesting that chrysin had a reversal effect on epithelial-mesenchymal transition. More importantly, it was demonstrated that inhibiting the Akt signal pathway might play a central role in chrysin-induced antimetastatic activity by regulating MMP-10 and epithelial-mesenchymal transition. In conclusion, our study indicates that chrysin exerts antimetastatic activities in TNBC cells, which suggests that chrysin might be a potential therapeutic candidate for the treatment of advanced or metastatic breast cancer.

IMPORTANCE Steroid hormone receptors, including estrogen receptor (ER) and progesterone receptor (PR), are crucial biomarkers in breast cancer (BC). However, limited data are available regarding single hormone receptor-positive (ER-positive/PR-negative and ER-negative/PR-positive) subtypes, rendering treatment decision and survival forecast difficult in patients with these BC subtypes. OBJECTIVE To investigate the clinicopathological characteristics and BC-specific survival (BCSS) of patients with single hormone receptor-positive BC. DESIGN, SETTING, AND PARTICIPANTS In this cohort study, data on patients diagnosed with BC between 1990 and 2015 were retrieved from the Surveillance, Epidemiology, and End Results database (N = 1 158 032). Patients lacking information on ER status, PR status, or BCSS were excluded (n = 334 633). Comparisons were performed between single hormone receptor-positive BC and double hormone receptor-positive/double hormone receptor-negative BC. The dates of analysis were September 1, 2018, to June 31, 2019. MAIN OUTCOMES AND MEASURES The BCSS of patients with single hormone receptor-positive BC. RESULTS This cohort study included 823 399 patients with BC (818 002 women and 5397 men). The median (range) age at diagnosis was 60 (8-108) years, and the median (range) follow-up duration was 71 (0-311) months. The percentages of ER-positive/PR-positive, ER-positive/PRnegative, ER-negative/PR-positive, and ER-negative/PR-negative cases were 67.2%, 12.2%, 1.6%, and 19.0%, respectively. Single hormone receptor-positive subtypes showed distinct clinical characteristics compared with double hormone receptor-positive/double hormone receptornegative subtypes. Multivariable Cox proportional hazards regression analysis showed that patients with ER-positive/PR-negative (hazard ratio [HR], 1.36; 95% CI, 1.34-1.38) and ER-negative/PRpositive (HR, 1.61; 95% CI, 1.55-1.67) tumors had worse BCSS than patients with the ER-positive/PRpositive subtype. In contrast, patients with ER-positive/PR-negative (HR, 1.27; 95% CI, 1.24-1.29) and ER-negative/PR-positive (HR, 1.07; 95% CI, 1.03-1.11) tumors had better BCSS than patients with the ER-negative/PR-negative subtype. The BCSS was statistically significantly worse in patients with ER-negative/PR-positive tumors than in patients with ER-positive/PR-negative tumors (HR, 1.18; 95% CI, 1.14-1.23). CONCLUSIONS AND RELEVANCE In this cohort study, statistically significant distinctions between survival rates of patients with single hormone receptor-positive BC vs double hormone receptorpositive/double hormone receptor-negative BC were observed. Different strategies may be required (continued)