In situ levels of oestrogen producing enzymes and its prognostic significance in postmenopausal breast cancer patients

Background The risk of developing breast cancer is strongly correlated with the overall exposure to oestrogen and most tumours are more or less dependent on oestrogen for their growth. A great majority of breast cancers occur after menopause when the ovaries have ceased to be functional, yet breast tumours in postmenopausal women maintain high intratumoural oestrogen concentrations, primarily through enzymatic conversion of androgenic precursors. Patients with a hormone dependent tumour generally receive the anti-oestrogen tamoxifen that mediate its anti-tumour effect by competing with oestrogen for binding to the oestrogen-receptor (ER). We therefore propose that the levels of oestrogen producing enzymes may affect the prognosis in postmenopausal breast cancer patients treated with tamoxifen. Methods We measured the mRNA and protein levels of aromatase and sulfatase by real-time PCR (n = 161) and immunohistochemistry (n = 131) in postmenopausal women with breast cancer. Results A significant better recurrence-free survival was detected in patients with weak or high protein expression of stromal aromatase (P = 0.0008), as also demonstrated by a decreased relative risk (RR = 0.50, CI = 0.33–0.76, P = 0.003). When we combined patients with weak and high stromal aromatase and selected only ER-positive patients, the improved prognosis was even more evident (P = 0.0000) and was shown to be a significant prognostic factor in a multivariate Cox-model (HR = 0.15, CI = 0.06–0.39, P = 0.000). The mRNA expression of aromatase and sulfatase, as well as the protein expression of sulfatase revealed no prognostic significance. Conclusion Protein expression of stromal aromatase may serve as a significant prognostic marker in ER-positive patients.     

Silencing of estrogen receptor alpha (ERalpha) gene by promoter hypermethylation is a frequent event in Chinese women with sporadic breast cancer

Usually, the function of estrogen receptor alpha (ERα) could be silenced by ERα gene promoter hypermethylation. However, frequency of ERα promoter methylation and the clinicopathological characteristics of ERα methylation in Chinese women with sporadic breast cancer are unknown. The aim of this study was to determine the methylation status of ERα promoter and its possible correlation with clinicopathological features in a series of 138 sporadic breast cancers in Chinese women. ER1, ER3, ER4, and ER5 primers were used for methylation-specific polymerase chain reaction (MSP) to analyze the CpG methylation of promoter region of ERα gene. In general, we found that ERα was methylated in 60.1% (83/138) tumors, including 57 of 69 ERα negative tumors (82.6%, P < 0.00001). Specifically within each region the methylation percentage of ER1, ER3, ER4 and ER5 were 34.8%, 35.5%, 39.1%, and 36.9% respectively. The degree of methylation at four CpG sites was higher in breast cancer compared with benign breast hyperplasia (P < 0.00001). In addition, the levels of ERα protein expression diminished with the frequency of ERα methylation (P < 0.0001, r = −0.469), the probability of methylation was increased for cases with ERα and PgR negativity (P < 0.00001). Our preliminary findings demonstrate, for what we believe to be the first time, that ERα methylation occurs in high frequency and is one of the mechanisms of ERα expression silence in a subset of sporadic breast cancers from Chinese women. Epigenetic alteration of the ERα gene may play an important role in the pathogenesis of breast cancer. L. Zhao and L. Wang have contributed equally to this work.     

High estrogen receptor expression in early breast cancer: chemotherapy needed to improve RFS?

Although poly(ADP-ribose) polymerase-1 (PARP1) inhibition is a recent promising therapy in breast cancer, PARP1 expression in this disease is not known. Using DNA microarray and array-based comparative genomic hybridization (arrayCGH), we examined PARP1 mRNA expression and copy number alterations in 326 invasive breast cancer samples and normal breast (NB) samples. A meta-analysis was performed on a large public retrospective gene expression data set (n = 2,485) to analyze correlation between PARP1 mRNA expression and molecular subtypes and clinico-pathological parameters. PARP1 was overexpressed in 58% of cancers, and its expression was heterogeneous between tumors. ArrayCGH data revealed an association between mRNA overexpression and gain/amplification at the PARP1 locus (P < 1.0E-8). Meta-analysis showed that PARP1 expression was higher in basal breast cancers (P < 1.0E-72), but overexpression was also found in other subtypes. PARP1 expression correlated with high grade, medullary histological type, tumor size, and worse metastasis-free survival (MFS; HR = 1.12 [1.04–1.22], P = 0.004) and overall survival (OS; HR = 1.16 [1.04–1.29], P = 0.006). In multivariate analysis, PARP1 expression had an independent prognostic value for MFS, which was restricted to patients untreated with any adjuvant chemotherapy. These data demonstrate overexpression of PARP1 in a large number of breast cancers and support the development of PARP inhibitors in basal subtype, but also potentially in other breast cancer subtypes.     

The prognostic role of circulating tumor cells (CTCs) detected by RT-PCR in breast cancer: a meta-analysis of published literature

The prognostic significance of circulating tumor cells (CTCs) in patients with breast cancer is controversial. We performed a meta-analysis of published literature to assess whether the detection of CTCs in patients diagnosed with primary breast cancer can be used as a prognostic factor. We searched Medline, Science Citation Index, and Embase databases as well as reference lists of relevant articles (including review articles) for studies that assessed the prognostic relevance of tumor cell detection in the peripheral blood (PB). A total of 24 eligible studies with 4,013 cases and 1,333 controls were included. Meta-analyses were performed using a random-effects model, using the hazard ratio (HR) and 95% confidence intervals (95% CIs) as effect measures. The positive detection of CTCs in patients was significantly associated with poor overall survival (OS) (HR = 3.00 [95% CI 2.29–3.94], n = 17, P < 0.0001) and recurrence-free survival (RFS) (HR = 2.67 [95% CI 2.09–3.42], n = 22, P < 0.0001). CTC-positive breast cancers were significantly associated with high histological grade (HR = 1.21 [95% CI 1.09–1.35], n = 34, P < 0.0001), tumor size (>2 cm) (HR = 1.12 [95% CI 1.02–1.22], n = 31, P = 0.01). and nodal status (≥1) (HR = 1.10 [95% CI 1.00–1.21], n = 32, P = 0.037), but cytokeratin-19 (CK-19) mRNA-positive CTCs were not associated with these clinicopathological parameters of breast cancer. Furthermore, the presence of CTCs was not associated with estrogen receptor (ER) negativity, progesterone receptor (PR) negativity, or human epidermal growth factor receptor type 2 (HER2) positivity. Detection of CTCs in the PB indicates poor prognosis in patients with primary breast cancer. Larger clinical studies are required to further evaluate the role of these markers in clinical practice.     

Immune infiltration in renal cell carcinoma

Immune infiltration of tumors is closely associated with clinical outcome in renal cell carcinoma (RCC). Tumor‐infiltrating immune cells (TIICs) regulate cancer progression and are appealing therapeutic targets. The purpose of this study was to determine the composition of TIICs in RCC and further reveal the independent prognostic values of TIICs. CIBERSORT, an established algorithm, was applied to estimate the proportions of 22 immune cell types based on gene expression profiles of 891 tumors. Cox regression was used to evaluate the association of TIICs and immune checkpoint modulators with overall survival (OS). We found that CD8+ T cells were associated with prolonged OS (hazard ratio [HR] = 0.09, 95% confidence interval [CI].01‐.53; P = 0.03) in chromophobe carcinoma (KICH). A higher proportion of regulatory T cells was associated with a worse outcome (HR = 1.59, 95% CI 1.23‐.06; P < 0.01) in renal clear cell carcinoma (KIRC). In renal papillary cell carcinoma (KIRP), M1 macrophages were associated with a favorable outcome (HR = .43, 95% CI .25‐.72; P < 0.01), while M2 macrophages indicated a worse outcome (HR = 2.55, 95% CI 1.45‐4.47; P < 0.01). Moreover, the immunomodulator molecules CTLA4 and LAG3 were associated with a poor prognosis in KIRC, and IDO1 and PD‐L2 were associated with a poor prognosis in KIRP. This study indicates TIICs are important determinants of prognosis in RCC meanwhile reveals potential targets and biomarkers for immunotherapy development.     

DNA-methylation of the homeodomain transcription factor PITX2 reliably predicts risk of distant disease recurrence in tamoxifen-treated, node-negative breast cancer patients--Technical and clinical validation in a multi-centre setting in collaboration with the European Organisation for Research and Treatment of Cancer (EORTC) PathoBiology group

Our aim was to identify and validate DNA-methylation markers associated with very good outcome in node negative, hormone receptor positive breast cancer patients after adjuvant endocrine therapy which might allow identifying patients who could be spared the burden of adjuvant chemotherapy. Using a methylation microarray, we analysed 117 candidate genes in hormone receptor-positive tumours from 109 breast cancer patients treated by adjuvant tamoxifen. Results were validated in an independent cohort (n=236, 5 centres). Independent methodological validation was achieved by a real-time polymerase chain reaction (PCR)-based technique. DNA methylation of PITX2 showed the strongest correlation with distant recurrence. Its impact on patient outcome was validated in the independent cohort: 86% of patients with low PITX2 methylation were metastasis-free after 10 years, compared to 69% with elevated PITX2 methylation. Moreover, PITX2 methylation added significant independent information to established clinical factors. All clinical and technical findings were confirmed by quantitative DNA-methylation PCR. These results provide strong evidence that DNA-methylation analysis allows clinically relevant risk assessment in tamoxifen-treated primary breast cancer. Based on PITX2 methylation, about half of hormone receptor-positive, node-negative breast cancer patients receiving adjuvant tamoxifen monotherapy can be considered low-risk regarding development of distant recurrences and may thus be spared adjuvant chemotherapy. In addition, these low-risk postmenopausal patients seem to respond sufficiently well to tamoxifen so that they may not require up-front aromatase inhibitor therapy.     

Risk-reducing salpingo-oophorectomy and breast cancer risk in BRCA1 or BRCA2 mutation carriers: A systematic review and meta-analysis

AimBRCA mutation carriers have a high lifetime risk of developing breast cancer (BC) and ovarian cancer (OC). Risk-reducing salpingo-oophorectomy (RRSO) has been shown to reduce OC risk. This meta-analysis was aim to analyze the effect of RRSO on the BC risk among BRCA1/2 mutation carriers.MethodsEmbase, PubMed, Web of Science, and Cochrane databases were searched for all studies investigating the effect of RRSO on BC risk. The pooled results were used to evaluate the association between RRSO and BC risk.ResultsThis meta-analysis included 13,965 BRCA1 and 7,057 BRCA2 mutation carriers from 14 observational studies. The pooled results showed that RRSO lowered BC risk among BRCA1 mutation carriers [hazard ratio (HR) = 0.63, 95% confidence interval (CI): 0.49–0.81, P < 0.01] and BRCA2 mutation carriers (HR = 0.51, 95% CI: 0.34–0.75, P < 0.01). RRSO reduced BC risk in younger women with BRCA1 mutation (HR = 0.48, 95% CI: 0.30–0.77, P < 0.01) and BRCA2 mutation (HR = 0.22, 95% CI: 0.08–0.65, P < 0.01). Analysis of the efficacy of RRSO at different time intervals after surgery showed a reduction of BC risk at <5 years after surgery in BRCA1 mutation carriers (HR = 0.60, 95% CI: 0.40–0.89, P = 0.01) and BRCA2 mutation carriers (HR = 0.42, 95% CI: 0.20–0.86, P = 0.02).ConclusionsRRSO is an effective way to reduce BC risk among women with BRCA1/2 mutation, especially in younger women. BRCA1/2 mutation carriers could benefit from RRSO in the immediate 5 years after surgery.     

CMTM3 inhibits cell migration and invasion and correlates with favorable prognosis in gastric cancer

The CKLF‐like MARVEL transmembrane domain containing 3 (CMTM3) gene is a novel tumor suppressor with frequent epigenetic inactivation. In this study, we showed the role played by CMTM3 in gastric cancer cells as a tumor suppressor gene, and examined the correlation between CMTM3 expression and clinicopathological parameters using immunohistochemistry in gastric cancer patients with different pathological stages (n = 350). We found that CMTM3 expression was reduced or silenced by epigenetic regulation in gastric cell lines, and dramatically downregulated in primary gastric cancer tissues. Restoration of CMTM3 significantly affected migration and invasion of AGS and SGC‐7901 cells (P < 0.001). In vivo experiments showed that peritoneal disseminated metastases were significantly suppressed by CMTM3 (P < 0.001). We further showed that the expression of MMP2 and the phosphorylation of Erk1/2 were decreased when CMTM3 was restored. In addition, by immunohistochemical staining, we found that the expression of CMTM3 was remarkably weaker in gastric cancer tissues than in normal mucosae (P = 0.008), and was significantly correlated with gender (P = 0.033), tumor depth (P = 0.049), stage (P = 0.021), and histological grade (P = 0.022). More importantly, CMTM3 expression was associated with prognosis in gastric cancer patients (P = 0.041), and was a significant independent prognostic indicator (hazard ratio = 0.704, 95% confidence interval, 0.498–0.994; P = 0.046). Our findings indicate that CMTM3 regulates migration and invasion of gastric cancer cells. Moreover, CMTM3 is a candidate marker for prognosis of gastric cancer in the clinic.     

Altered JS-2 expression in colorectal cancers and its clinical pathological relevance

JS-2 is a novel gene located at 5p15.2 and originally detected in primary oesophageal cancer. There is no study on the role of JS-2 in colorectal cancer. The aim of this study is to determine the gene copy number and expression of JS-2 in a large cohort of patients with colorectal tumours and correlate these to the clinicopathological features of the cancer patients. We evaluated the DNA copy number and mRNA expression of JS-2 in 176 colorectal tissues (116 adenocarcinomas, 30 adenomas and 30 non-neoplastic tissues) using real-time polymerase chain reaction. JS-2 expression was also evaluated in two colorectal cancer cell lines and a benign colorectal cell line. JS-2 amplification was noted in 35% of the colorectal adenocarcinomas. Significant differences in relative expression levels for JS-2 mRNA between different colorectal tissues were noted (p = 0.05). Distal colorectal adenocarcinoma had significantly higher copy number than proximal adenocarcinoma (p = 0.005). The relative expression level of JS-2 was different between colonic and rectal adenocarcinoma (p = 0.007). Mucinous adenocarcinoma showed higher JS-2 expression than non-mucinous adenocarcinoma (p = 0.02). Early T-stage cancers appear to have higher JS-2 copy number and lower expression of JS-2 mRNA than later stage cancers (p = 0.001 and 0.03 respectively). Colorectal cancer cell lines showed lower expression of JS-2 than the benign colorectal cell line. JS-2 copy number change and expression were shown for the first time to be altered in the carcinogenesis of colorectal cancer. In addition, genetic alteration of JS-2 was found to be related to location, pathological subtypes and staging of colorectal cancer.     

BRCA1 promoter methylation is associated with increased mortality among women with breast cancer

Promoter-CpG island hypermethylation has been proposed as an alternative mechanism to inactivate BRCA1 in the breast where somatic mutations of BRCA1 are rare. To better understand breast cancer etiology and progression, we explored the association between BRCA1 promoter methylation status and prognostic factors as well as survival among women with breast cancer. Promoter methylation of BRCA1 was assessed in 851 archived tumor tissues collected from a population-based study of women diagnosed with invasive or in situ breast cancer in 1996–1997, and who were followed for vital status through the end of 2002. About 59% of the tumors were methylated at the promoter of BRCA1. The BRCA1 promoter methylation was more frequent in invasive cancers (P = 0.02) and among premenopausal cases (P = 0.05). BRCA1 promoter methylation was associated with increased risk of breast cancer-specific mortality (age-adjusted HR 1.71; 95% CI: 1.05–2.78) and all-cause mortality (age-adjusted HR 1.49; 95% CI: 1.02–2.18). Neither dietary methyl intakes in the year prior to the baseline interview nor the functional polymorphisms in one-carbon metabolism were associated with BRCA1 methylation status. Our study is the first epidemiological investigation on the prognostic value of BRCA1 promoter methylation in a large population-based cohort of breast cancer patients. Our results indicate that BRCA1 promoter methylation is an important factor to consider in predicting breast cancer survival. This work was supported by grants from the National Institutes of Health (CA109753 to JC; DK55865 to SZ) and in part by grants from Department of Defense (BC031746), National Cancer Institute and the National Institutes of Environmental Health and Sciences (UO1CA/ES66572, UO1CA66572, P30CA013696, P30ES09089 and P30ES10126); and by the University of North Carolina Clinical Nutrition Research Unit (DK56350) and Center for Environmental Health and Susceptibility (ES10126). Xu, X. is a recipient of the Predoctoral Traineeship Award (W81XWH-06-1-0298) of Department of Defense Breast Cancer Research Program.     

Decreased expression of EZH2 is associated with upregulation of ER and favorable outcome to tamoxifen in advanced breast cancer

The purpose of this study is to investigate EZH2 in a large series of breast cancer patients for its prognostic and predictive value, and to evaluate its functional role in treatment response in vitro. EZH2 levels were measured using quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) in primary breast cancer specimens and related to clinicopathologic factors and disease outcome. EZH2 expression was downregulated with siRNAs in MCF7, to assess expression alterations of putative EZH2 downstream genes and to determine cell numbers after treatment with the anti-estrogen ICI 164384. In 688 lymph node-negative patients who did not receive adjuvant systemic therapy, EZH2 was not significantly correlated with metastasis-free survival (MFS). In 278 patients with advanced disease treated with first-line tamoxifen monotherapy, the tertile with highest EZH2 levels was associated with the lowest clinical benefit (OR = 0.48; P = 0.02) and with a shorter progression-free survival (PFS) in both univariate (HR = 1.80; P < 0.001) and multivariate analysis, including traditional factors (HR = 1.61; P = 0.004). In vitro, EZH2 silencing in MCF7 caused a 38% decrease in cell numbers (P < 0.001) whereas ICI 164384 treatment resulted in a 25% decrease (P < 0.001) compared to controls. Combining EZH2 silencing with ICI treatment reduced cell numbers with 67% (P < 0.001) compared to control conditions. EZH2 downregulation was associated with an almost two-fold upregulation of the estrogen receptor alpha (ER) (P = 0.001). In conclusion, EZH2 has no prognostic value in breast cancer. High levels of EZH2 are associated with poor outcome to tamoxifen therapy in advanced breast cancer. Downregulated EZH2 leads to upregulation of the ER and better response to anti-estrogens.     

Physical activity and survival after breast cancer diagnosis: meta-analysis of published studies

Published data have shown that physical activity (PA) has a positive role on the primary prevention of breast cancer risk. However, the role of PA on breast cancer outcome has been controversial with inconsistent data. The lack of a meta-analysis that addresses that issue prompted the current report. A comprehensive literature search identified eight studies, of which two studies were excluded. The remaining six studies (12,108 patients with breast cancer) were included in this meta-analysis. Pre-diagnosis PA reduced all causes mortality by 18% but had no effect on breast cancer deaths. Post-diagnosis PA reduced breast cancer deaths by 34% (HR = 0.66, 95% CI, 0.57–0.77, P < 0.00001), all causes mortality by 41% (HR = 0.59, 95% CI, 0.53–0.65, P < 0.00001), and disease recurrence by 24% (HR = 0.76, 95% CI, 0.66–0.87, P = 0.00001). Breast cancer mortality was reduced by pre-diagnosis PA in women with body mass index (BMI) < 25 kg/m2, while post-diagnosis PA reduced that risk among those with BMI ≥ 25 kg/m2. On the other hand, post-diagnosis PA reduced all causes mortality regardless of the BMI. The analysis showed that post-diagnosis PA reduced breast cancer deaths (HR = 0.50, 95% CI, 0.34–0.74, P = 0.0005), and all causes mortality (HR = 0.36, 95% CI, 0.12–1.03, P = 0.06) among patients with estrogen receptor (ER)-positive tumor, while women with ER-negative disease showed no gain. The current meta-analysis provides evidence for an inverse relationship between PA and mortality in patients with breast cancer and supports the notion that appropriate PA should be embraced by breast cancer survivors.     

Downregulation of TSLC1 and DAL-1 expression occurs frequently in breast cancer

TSLC1 and DAL-1 are tumor suppressor genes involved in cell adhesion. In this study, we examined the expression and methylation pattern of these genes in breast cancer cell lines and primary breast carcinomas. TSLC1 expression was lost in 5 of 8 (63%) and DAL-1 expression was lost in 6 of 8 (75%) breast cancer cell lines, respectively. Downregulation of TSLC1 expression was observed in 43 of 50 (86%) and of DAL-1 expression in 26 of 55 (47%) primary breast carcinomas. TSLC1 methylation was found in 4 of 8 (50%) and DAL-1 methylation was observed in 6 of 8 (75%) breast cancer cell lines, respectively. Of 95 primary breast carcinomas 46 (48%) were TSLC1 methylated and 26 (27%) were DAL-1 methylated. Twenty of 43 (47%) and 10 of 26 (38%) primary breast cancer samples which showed downregulation of TSLC1 and DAL-1 expression were unmethylated for these genes. Re-expression of TSLC1 and DAL-1 was observed after treatment of BT-20 cells with 5-aza-2′-deoxycytidine and TSA. Samples from patients with grade 3 tumors were more frequently TSLC1 and TSLC1 and/or DAL-1 methylated than samples from patients with grade 1 and 2 tumors (P = 0.032, P = 0.023). Moreover, TSLC1 methylation correlated with loss of both ER and PgR staining (P = 0.011, P = 0.02). Our findings suggest that TSLC1 and DAL-1 are involved in the pathogenesis of breast cancer and are frequently inactivated by methylation.     

Endocrine therapy in obese patients with primary breast cancer: another piece of evidence in an unfinished puzzle

Obesity, defined as a body mass index (BMI) ≥30 is an independent risk factor in breast cancer and is correlated with shorter survival and enhanced recurrence rates. The present subgroup analysis of the German BRENDA-cohort aimed to investigate the correlation between BMI, recurrence-free survival (RFS) and adjuvant endocrine therapy. In this subgroup analysis, 4,636 patients were retrospectively examined using multivariate analyses. Overall 3,759 (81.1%) patients had a BMI <30 (non-obese) and 877 (18.9%) a BMI ≥30 (obese). In the group of all 3,896 (84.0%) patients with hormone-receptor-positive (HR+) breast carcinomas a significant reduction in RFS was demonstrated for those who were obese (P = 0.002; HR = 1.45 (95% CI: 1.15–1.83)), also after adjustment for Nottingham Prognostic Index (NPI) (P = 0.028; HR = 1.30 (95% CI: 1.03–1.65)). In hormone-receptor-negative (HR−) patients BMI had no influence on RFS (P = 0.380; HR = 1.20 (95% CI: 0.80–1.81)). Considering menopausal status, a significantly shorter RFS was seen in postmenopausal obese than in non-obese patients (P < 0.001; HR = 1.61 (95% CI: 1.24–2.09)), whereas the premenopausal patient group only showed a trend towards a shorter RFS (P = 0.202; HR = 1.44 (95% CI: 0.82–2.53)). The group of HR+ postmenopausal patients with normal or intermediate weight showed a non-significant statistical trend towards a survival benefit for aromatase inhibitors (AI) compared to tamoxifen (RFS: P = 0.486; HR = 1.29 (95% CI: 0.63–2.62), while obese patients tended to benefit more from tamoxifen (RFS: P = 0.289; HR = 0.65 (95% CI: 0.29–1.45)). In accordance with recently published results we demonstrated a negative effect of a high BMI on outcome in primary breast cancer. Furthermore the efficacy of AI seems dependent on BMI in contrast to tamoxifen. Prospective studies to optimise the therapy of obese breast cancer patients are urgently needed.     

Aberrant DNA methylation but not mutation of CITED4 is associated with alteration of HIF-regulated genes in breast cancer

CBP/p300-interacting transactivator with ED-rich carboxy-terminal domain 4 (CITED4) inhibits HIF-1α transactivation by binding to CBP/p300. We hypothesised that either somatic mutation or hypermethylation of the CITED4 gene underlies CITED4 down-regulation and thus enhanced HIF-1α expression in some breast tumours. DNA sequencing was used to screen for somatic mutations. Methylation-sensitive high resolution melting was performed to identify CITED4 methylation. RT-qPCR was carried out to measure the expression of CITED4 and selected HIF downstream targets. HIF-1α and downstream gene expression was assessed with immunohistochemistry. No somatic mutations of CITED4 were identified in 10 tumour cell lines and 100 breast carcinomas. However, CITED4 promoter methylation was identified in 5/168 breast carcinomas (four infiltrating ductal carcinomas and one infiltrating lobular carcinoma) and in 3/10 breast cancer cell lines (MDA-MB-453, MDA-MB-231 and Hs578T). CITED4 mRNA expression in cell lines was inversely correlated with DNA methylation. CITED4 mRNA expression was significantly increased in all three cell lines after 5-aza-2-deoxycytidine (DAC) treatment. Treatment of the MDA-MB-231 cell line with DAC followed by hypoxia (0.1% O₂) resulted in down-regulation of expression of the HIF-1α downstream genes VEGFA and SLC2A1 (P = 0.0029). HIF-1α downstream SLC2A1 was decreased (P = 0.021) after CITED4 was re-expressed under hypoxia. Loss of expression of CITED4 in breast cancer may be due to DNA methylation but is unlikely to be due to mutation. Demethylation and histone modification can potentially reactivate CITED4 gene expression in some breast cancers and lead to changes in tumour behaviour. Strategies such as HDAC inhibitors may overcome this effect.