Antibodies toward Na+,HCO3--cotransporter NBCn1/SLC4A7 block net acid extrusion and cause pH-dependent growth inhibition and apoptosis in breast cancer.

BACKGROUND: Na+,HCO3--cotransporter NBCn1/Slc4a7 accelerates murine breast carcinogenesis. Lack of specific pharmacological tools previously restricted therapeutic targeting of NBCn1 and identification of NBCn1-dependent functions in human breast cancer. METHODS: We develop extracellularly-targeted anti-NBCn1 antibodies, screen for functional activity on cells, and evaluate (a) mechanisms of intracellular pH regulation in human primary breast carcinomas, (b) proliferation, cell death, and tumor growth consequences of NBCn1 in triple-negative breast cancer, and (c) association of NBCn1-mediated Na+,HCO3--cotransport with human breast cancer metastasis. RESULTS: We identify high-affinity (KD ≈ 0.14 nM) anti-NBCn1 antibodies that block human NBCn1-mediated Na+,HCO3--cotransport in cells, without cross-reactivity towards human NBCe1 or murine NBCn1. These anti-NBCn1 antibodies abolish Na+,HCO3--cotransport activity in freshly isolated primary organoids from human breast carcinomas and lower net acid extrusion effectively in primary breast cancer tissue from patients with macrometastases in axillary lymph nodes. Inhibitory anti-NBCn1 antibodies decelerate tumor growth in vivo by ~50% in a patient-derived xenograft model of triple-negative breast cancer and pH-dependently reduce colony formation, cause G2/M-phase cell cycle accumulation, and increase apoptosis of metastatic triple-negative breast cancer cells in vitro. CONCLUSIONS: Inhibitory anti-NBCn1 antibodies block net acid extrusion in human breast cancer tissue, particularly from patients with disseminated disease, and pH-dependently limit triple-negative breast cancer growth.

Amplified Ca2+ dynamics and accelerated cell proliferation in breast cancer tissue during purinergic stimulation.

Intracellular Ca2+ dynamics shape malignant behaviors of cancer cells. Whereas previous studies focused on cultured cancer cells, we here used breast organoids and colonic crypts freshly isolated from human and murine surgical biopsies. We performed fluorescence microscopy to evaluate intracellular Ca2+ concentrations in breast and colon cancer tissue with preferential focus on intracellular Ca2+ release in response to purinergic and cholinergic stimuli. Inhibition of the sarco-/endoplasmic reticulum Ca2+ ATPase with cyclopiazonic acid elicited larger Ca2+ responses in breast cancer tissue, but not in colon cancer tissue, relative to respective normal tissue. The resting intracellular Ca2+ concentration was elevated, and ATP, UTP and acetylcholine induced strongly augmented intracellular Ca2+ responses in breast cancer tissue compared with normal breast tissue. In contrast, resting intracellular Ca2+ levels and acetylcholine-induced increases in intracellular Ca2+ concentrations were unaffected and ATP- and UTP-induced Ca2+ responses were smaller in colon cancer tissue compared with normal colon tissue. In accordance with the amplified Ca2+ responses, ATP and UTP substantially increased proliferative activity-evaluated by bromodeoxyuridine incorporation-in breast cancer tissue, whereas the effect was minimal in normal breast tissue. ATP caused cell death-identified with ethidium homodimer-1 staining-in breast cancer tissue only at concentrations above the expected pathophysiological range. We conclude that intracellular Ca2+ responses are amplified in breast cancer tissue, but not in colon cancer tissue, and that nucleotide signaling stimulates breast cancer cell proliferation within the extracellular concentration range typical for solid cancer tissue.

Hypoxia-inducible factor-1α expression and breast cancer recurrence in a Danish population-based case control study.

BACKGROUND: Hypoxia-inducible factor-1α (HIF-1α) is a transcription factor that facilitates the adaptation of cancer cells to hypoxic conditions and may be prognostic of breast cancer recurrence. We evaluated the association of HIF-1α expression with breast cancer recurrence, and its association with timing of breast cancer recurrence. METHODS: In this population-based case-control study, we included women diagnosed with stage I-III breast cancer between 1985 and 2001, aged 35-69 years, registered in the Danish Breast Cancer Group. We identified 541 cases of breast cancer recurrence among women with estrogen receptor (ER)-positive disease who were treated with tamoxifen for at least 1 year (ER+ TAM+). We also enrolled 300 breast cancer recurrence cases among women with ER-negative disease, not treated with tamoxifen, who survived at least 1 year (ER-/TAM-). Controls were recurrence-free breast cancer patients at the time of case diagnosis, matched to recurrence cases on ER/TAM status, date of surgery, menopausal status, cancer stage, and county of residence. Expression of HIF-1α was measured by immunohistochemistry on tissue microarrays. We fitted logistic regression models to compute odds ratios (ORs) and 95% confidence intervals (CIs) associating HIF-1α expression with recurrence, and with timing of recurrence. RESULTS: HIF-1α expression was observed in 23% of cases and 20% of controls in the ER+/TAM+ stratum, and in 47% of cases and 48% of controls in the ER-/TAM- stratum. We observed a near-null association between HIF-1α expression in both ER/TAM groups (ER+/TAM+ OR = 1.21, 95%CI 0.88, 1.67 and ER-/TAM- OR = 0.97, 95%CI 0.68, 1.39). HIF-1α expression was not associated with time to recurrence among women in the ER+/TAM+ stratum, but was associated with early recurrence among women in the ER-/TAM- stratum. CONCLUSION: In this study, HIF-1α expression was not associated with breast cancer recurrence overall but may be associated with early recurrence among women diagnosed with ER- breast cancer.

Acid-base transporters and pH dynamics in human breast carcinomas predict proliferative activity, metastasis, and survival.

Breast cancer heterogeneity in histology and molecular subtype influences metabolic and proliferative activity and hence the acid load on cancer cells. We hypothesized that acid-base transporters and intracellular pH (pHi) dynamics contribute inter-individual variability in breast cancer aggressiveness and prognosis. We show that Na+,HCO3- cotransport and Na+/H+ exchange dominate cellular net acid extrusion in human breast carcinomas. Na+/H+ exchange elevates pHi preferentially in estrogen receptor-negative breast carcinomas, whereas Na+,HCO3- cotransport raises pHi more in invasive lobular than ductal breast carcinomas and in higher malignancy grade breast cancer. HER2-positive breast carcinomas have elevated protein expression of Na+/H+ exchanger NHE1/SLC9A1 and Na+,HCO3- cotransporter NBCn1/SLC4A7. Increased dependency on Na+,HCO3- cotransport associates with severe breast cancer: enlarged CO2/HCO3--dependent rises in pHi predict accelerated cell proliferation, whereas enhanced CO2/HCO3--dependent net acid extrusion, elevated NBCn1 protein expression, and reduced NHE1 protein expression predict lymph node metastasis. Accordingly, we observe reduced survival for patients suffering from luminal A or basal-like/triple-negative breast cancer with high SLC4A7 and/or low SLC9A1 mRNA expression. We conclude that the molecular mechanisms of acid-base regulation depend on clinicopathological characteristics of breast cancer patients. NBCn1 expression and dependency on Na+,HCO3- cotransport for pHi regulation, measured in biopsies of human primary breast carcinomas, independently predict proliferative activity, lymph node metastasis, and patient survival.

Early Discontinuation of Endocrine Therapy and Recurrence of Breast Cancer among Premenopausal Women.

PURPOSE: Premenopausal women diagnosed with estrogen receptor (ER)-positive breast cancer are prescribed 5-10 years of endocrine therapy to prevent or delay recurrence. In this study, we evaluated the association between early discontinuation of endocrine therapy and breast cancer recurrence in a cohort of premenopausal women. EXPERIMENTAL DESIGN: We identified 4,503 patients with premenopausal ER-positive breast cancer who initiated adjuvant endocrine therapy and were registered in the Danish Breast Cancer Group clinical database (2002-2011). Women were excluded if they had a recurrence or were lost to follow-up less than 1.5 years after breast cancer surgery. Endocrine therapy was considered complete if the patient received at least 4.5 years of treatment or discontinued medication less than 6 months before recurrence. Exposure status was updated annually and modeled as a time-dependent variable. We accounted for baseline and time-varying confounders via time-varying weights, which we calculated from multivariable logistic regression models, and included in regression models to estimate HRs and 95% confidence intervals (CIs) associating early discontinuation with recurrence. RESULTS: Over the study follow-up, 1,001 (22%) women discontinued endocrine therapy. We observed 202 (20%) recurrences among those who discontinued endocrine therapy, and 388 (11%) among those who completed the recommended treatment. The multivariable-adjusted estimated rate of recurrence was higher in women who discontinued endocrine therapy relative to those who completed their treatment (hazard ratio, 1.67; 95% CI, 1.25-2.14). CONCLUSIONS: These results highlight the importance of clinical follow-up and behavioral interventions that support persistence of adjuvant endocrine therapy to prevent breast cancer recurrence.

Predictive pharmacogenetic biomarkers for breast cancer recurrence prevention by simvastatin.

Background: Statins treat hyperlipidemia and prevent cardiovascular morbidity and mortality. Evidence suggests that they also have anti-neoplastic activity. Several studies show a reduced rate of breast cancer recurrence among lipophilic statin users (e.g., simvastatin), motivating calls for clinical trials of statins in breast cancer patients. We measured the impact of genetic variation in statin-metabolizing enzymes and drug transporters on the recurrence rate in simvastatin-treated breast cancer patients.Methods: We conducted a nested case-control study among Danish women diagnosed with non-metastatic, invasive breast cancer between 2004-2010 who had filled ≥1 prescription for simvastatin after diagnosis. Cases were all breast cancer recurrences from the source population; one control was matched to each case on cancer stage, estrogen receptor and hormone therapy status, calendar period of diagnosis, and duration of simvastatin exposure. We genotyped variants in simvastatin-metabolizing enzymes (CYP3A4/rs35599367 and CYP3A5/rs776746) and drug transporters (ABCB1/rs2032582 and SLCO1B1/rs4149056), and estimated their association with recurrence with logistic regression models.Results: We observed protective (though imprecisely-measured) associations between variants in genes encoding drug transporters (ABCB1 and SLCO1B1) and simvastatin-metabolizing enzymes (CYP3A4 and CYP3A5) and breast cancer recurrence in simvastatin-treated women. For example, carrying two variant alleles in ABCB1 was associated with a 31% lower rate of recurrence (multivariable OR = 0.69, 95% CI: 0.31, 1.5).Conclusion: Our study provides weak evidence to support the use of genetic variation in ABCB1, SLCO1B1, CYP3A4, and CYP3A5 as biomarkers of breast tumor response to simvastatin. Validation of these findings within adjuvant clinical trials is encouraged.

Metabolic Pathway Analysis and Effectiveness of Tamoxifen in Danish Breast Cancer Patients.

BACKGROUND: Tamoxifen and its metabolites compete with estrogen to occupy the estrogen receptor. The conventional dose of adjuvant tamoxifen overwhelms estrogen in this competition, reducing breast cancer recurrence risk by nearly half. Phase I metabolism generates active tamoxifen metabolites, and phase II metabolism deactivates them. No earlier pharmacogenetic study has comprehensively evaluated the metabolism and transport pathways, and no earlier study has included a large population of premenopausal women. METHODS: We completed a cohort study of 5,959 Danish nonmetastatic premenopausal breast cancer patients, in whom 938 recurrences occurred, and a case-control study of 541 recurrent cases in a cohort of Danish predominantly postmenopausal breast cancer patients, all followed for 10 years. We collected formalin-fixed paraffin-embedded tumor blocks and genotyped 32 variants in 15 genes involved in tamoxifen metabolism or transport. We estimated conventional associations for each variant and used prior information about the tamoxifen metabolic path to evaluate the importance of metabolic and transporter pathways. RESULTS: No individual variant was notably associated with risk of recurrence in either study population. Both studies showed weak evidence of the importance of phase I metabolism in the clinical response to adjuvant tamoxifen therapy. CONCLUSIONS: Consistent with prior knowledge, our results support the role of phase I metabolic capacity in clinical response to tamoxifen. Nonetheless, no individual variant substantially explained the modest phase I effect on tamoxifen response. IMPACT: These results are consistent with guidelines recommending against genotype-guided prescribing of tamoxifen, and for the first time provide evidence supporting these guidelines in premenopausal women.

Inflammatory breast cancer: A review from our experience.

INTRODUCTION: Inflammatory Breast Cancer (IBC) is a distinct and rare type of breast cancer accounting for up to 6% of all breast cancer cases in Europe. The aim of this study was to investigate diagnostic methods, treatments, and outcome after IBC in patients treated at a single institution in Denmark. METHOD: All patients treated for IBC at Aarhus University Hospital between 2000 and 2014 were identified and included in the cohort. Survival was assessed using Kaplan-Meier curves and log-rank statistics. RESULTS: A total of 89 patients were identified with a median follow up of 3.6 years. The overall survival at 5 and 10 years were 41% and 18%, respectively. The disease free survival at 5 and 10 years were 47% and 27%, respectively. Thirty-four percent had distant metastasis at time of diagnosis. Patients with ER positive tumors had a significantly better overall survival than patients with ER negative tumors (p = 0.01). CONCLUSION: Despite a more aggressive systemic and loco-regional treatment today, IBC is still a very serious disease with a high mortality.

Phthalate Exposure and Breast Cancer Incidence: A Danish Nationwide Cohort Study.

PURPOSE: Phthalate exposure is ubiquitous and especially high among users of drug products formulated with phthalates. Some phthalates mimic estradiol and may promote breast cancer. Existing epidemiologic studies on this topic are small, mostly not prospective, and have given inconsistent results. We estimated associations between longitudinal phthalate exposures and breast cancer risk in a Danish nationwide cohort, using redeemed prescriptions for phthalate-containing drug products to measure exposure. METHODS: We ascertained the phthalate content of drugs marketed in Denmark using an internal Danish Medicines Agency ingredient database. We enrolled a Danish nationwide cohort of 1.12 million women at risk for a first cancer diagnosis on January 1, 2005. By combining drug ingredient data with the Danish National Prescription registry, we characterized annual, cumulative phthalate exposure through redeemed prescriptions. We then fit multivariable Cox regression models to estimate associations between phthalate exposures and incident invasive breast carcinoma according to tumor estrogen receptor status. RESULTS: Over 9.99 million woman-years of follow-up, most phthalate exposures were not associated with breast cancer incidence. High-level dibutyl phthalate exposure (≥ 10,000 cumulative mg) was associated with an approximately two-fold increase in the rate of estrogen receptor-positive breast cancer (hazard ratio, 1.9; 95% CI, 1.1 to 3.5), consistent with in vitro evidence for an estrogenic effect of this compound. Lower levels of dibutyl phthalate exposure were not associated with breast cancer incidence. CONCLUSION: Our results suggest that women should avoid high-level exposure to dibutyl phthalate, such as through long-term treatment with pharmaceuticals formulated with dibutyl phthalate.

Cohort Profile: the Predictors of Breast Cancer Recurrence (ProBe CaRE) Premenopausal Breast Cancer Cohort Study in Denmark.

PURPOSE: The Predictors of Breast Cancer Recurrence (ProBe CaRe) study was established to evaluate modification of tamoxifen (TAM) effectiveness in premenopausal women through reduced activity of TAM-metabolising enzymes. It comprehensively evaluates the effects of pharmacogenetic variants, use of concomitant medications and biomarkers involved in oestrogen metabolism on breast cancer recurrence risk. PARTICIPANTS: The ProBe CaRe study was established using resources from the Danish Breast Cancer Group (DBCG), including 5959 premenopausal women diagnosed with stage I-III primary breast cancer between 2002 and 2010 in Denmark. Eligible participants were divided into two groups based on oestrogen receptor alpha (ERα) expression and receipt of TAM therapy, 4600 are classified as ERα+/TAM+ and 1359 are classified as ERα-/TAM-. The ProBe CaRe study is a population-based cohort study nested in a nearly complete source population, clinical, tumour and demographic data were abstracted from DBCG registry data. Linkage to Danish registries allows for abstraction of information regarding comorbid conditions, comedication use and mortality. Formalin-fixed paraffin-embedded tissue samples have been prepared for DNA extraction and immunohistochemical assay. FINDINGS TO DATE: To mitigate incorrect classification of patients into specific categories, we conducted a validation substudy. We compared data acquired from registry and from medical record review to calculate positive predictive values (PPVs) and negative predictive values. We observed PPVs near 100% for tumour size, lymph node involvement, receptor status, surgery type, receipt of radiotherapy, receipt of chemotherapy and TAM treatment. We found that the PPVs were 96% (95% CI 83% to 100%) for change in endocrine therapy and 61% (95% CI 42% to 77%) for menopausal transition. FUTURE PLANS: The ProBeCaRe cohort study is well positioned to comprehensively examine pharmacogenetic variants. We will use a Bayesian pathway analysis to evaluate the complete TAM metabolic path to allow for gene-gene interactions, incorporating information of other important patient characteristics.

Use of prescription drugs and risk of postoperative red blood cell transfusion in breast cancer patients: a Danish population-based cohort study.

BACKGROUND: Several frequently used prescription drugs may affect bleeding risk. We investigated use of aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), selective serotonin reuptake inhibitors (SSRIs), and statins and risk of postoperative red blood cell transfusion in breast cancer patients. METHODS: Using Danish population-based registries, we identified a cohort of women who underwent surgery for primary breast cancer (n = 22,238) during 2005-2012 and ascertained their use of aspirin, NSAIDs, SSRIs, and statins. For each drug, patients were categorized as users if they filled ≥1 prescription in the 60 days prior to surgery. We calculated the 14-day risk of red blood cell transfusion and relative risks (RRs) with 95% confidence intervals (CIs), comparing users with nonusers for each drug and adjusting for age, cancer stage, and Charlson Comorbidity Index score. RESULTS: In our cohort, 1385 (6.2%) women were aspirin users, 1794 (8.0%) were NSAID users, 1110 (4.9%) were SSRI users, and 2053 (9.1%) were statin users. The overall risk of red blood cell transfusion was 1.3%. The 14-day risk of RBC transfusion was 3.5% among aspirin users versus 1.1% among aspirin nonusers (adjusted RR = 1.9, 95% CI: 1.4-2.7), and 1.8% among SSRI users versus 1.2% among SSRI nonusers (adjusted RR = 1.2, 95% CI: 0.7-1.9). Red blood cell transfusion risk was increased among NSAID users, but not in a sensitivity analysis with a 30-day exposure window. Red blood cell transfusion risk was not increased among SSRI and statin users. CONCLUSIONS: Primary breast cancer surgery confers a low risk of RBC transfusion. Still, use of aspirin and possibly NSAIDs, but not SSRIs and statins, is associated with increased red blood cell transfusion. This increased risk is not explained by differences in age, stage, or comorbidity level.

Validity of Danish Breast Cancer Group (DBCG) registry data used in the predictors of breast cancer recurrence (ProBeCaRe) premenopausal breast cancer cohort study.

BACKGROUND: Validation studies of the Danish Breast Cancer Group (DBCG) registry show good agreement with medical records for adjuvant treatment data, but inconsistent recurrence information. No studies have validated changes in menopausal status or endocrine therapy during follow-up. In a longitudinal study, we validated DBCG data using medical records as the gold standard. MATERIAL AND METHODS: From a cohort of 5959 premenopausal women diagnosed during 2002-2010 with stage I-III breast cancer, we selected 151 patients - 77 estrogen-receptor-positive and 74 estrogen-receptor-negative - from three hospitals. We assessed the validity of DBCG registry data on patient, tumor, and treatment factors, and follow-up information on menopausal transition, changes in endocrine therapy, and recurrence. We computed positive predictive values (PPVs) with 95% confidence intervals (95%CI). RESULTS: Agreement was near perfect for tumor size, lymph node involvement, receptor status, surgery type, and receipt of radiotherapy, chemotherapy, or tamoxifen treatment. The PPV for a change in endocrine therapy in the DBCG was 96% (95%CI = 83, 100). The PPV for menopausal transition was 61% (95%CI = 42, 77). The PPV for DBCG-recorded recurrence was 100%. However, of 19 patients who had a recurrence documented in their medical record, 13 had the recurrence registered in DBCG. CONCLUSIONS: DBCG data are valid for most epidemiological studies of breast cancer treatment. Data on menopausal transition may be less valid, though this interpretation depends on the suitability of medical records for making this assessment. Although recurrence is missing for some, this would not bias most ratio measures of association.

Impact of age, intrinsic subtype and local treatment on long-term local-regional recurrence and breast cancer mortality among low-risk breast cancer patients.

AIM: To evaluate the long-term prognostic impact of age, local treatment and intrinsic subtypes on the risk of local-regional recurrence (LRR) and breast cancer mortality among low-risk patients. MATERIAL AND METHODS: Cohort study with prospectively collected data, balanced five-year age groups, including 514 Danish lymph node negative breast cancer patients diagnosed between 1989 and 1998, treated with mastectomy (N = 320) or breast-conserving therapy (BCT) (N = 194) and without systemic treatment. Intrinsic subtype approximation was performed by combining information on estrogen-, progesterone-, HER2 receptor and Ki67. RESULTS: The majority of the tumors had a luminal subtype: 70% Luminal-A (LumA), 16% Luminal-B (LumB), and 10% Luminal-HER2 + (Lum-HER2+). The distribution of intrinsic subtypes between younger (≤45 years) and older (>45 years) patients was similar. Intrinsic subtypes had no prognostic impact on the 20-year LRR risk, regardless of age. A distinct 20-year mortality pattern was observed among the younger patients: 11% of patients with LumB tumor died of breast cancer within the first five years after primary surgery, 23% of patients with Lum-HER2+ tumor died within a 5-10-year period, whereas patients with LumA tumor died with a constant low rate throughout the 20-year period. After 20 years of follow-up, patients with LumA tumor had breast cancer mortality comparable to that of patients with LumB tumor (20%) and lower than Lum-HER2+ tumor (39%). Among the older patients, no distinct mortality pattern was observed, and the 20-year breast cancer mortality was not associated with intrinsic subtypes. CONCLUSION: Among low-risk patients, 96% of the tumors were Luminal and the distribution of intrinsic subtypes between younger (≤45 years) and older (>45 years) patients was similar. The observed higher frequency of LRR among younger low-risk BCT patients was not associated intrinsic subtype. The 20-year breast cancer mortality was non-significant for LumA tumors among the older patients, whereas among the younger patients, LumA tumors had a comparable mortality with LumB, but lower than for Lum-HER2 + tumors.

Opioids and breast cancer recurrence: A Danish population-based cohort study.

BACKGROUND: Opioids may alter immune function, thereby potentially affecting cancer recurrence. The authors investigated the association between postdiagnosis opioid use and breast cancer recurrence. METHODS: Patients with incident, early stage breast cancer who were diagnosed during 1996 through 2008 in Denmark were identified from the Danish Breast Cancer Cooperative Group Registry. Opioid prescriptions were ascertained from the Danish National Prescription Registry. Follow-up began on the date of primary surgery for breast cancer and continued until breast cancer recurrence, death, emigration, 10 years, or July 31, 2013, whichever occurred first. Cox regression models were used to compute hazard ratios and 95% confidence intervals associating breast cancer recurrence with opioid prescription use overall and by opioid type and strength, immunosuppressive effect, chronic use (≥6 months of continuous exposure), and cumulative morphine-equivalent dose, adjusting for confounders. RESULTS: In total, 34,188 patients were identified who, together, contributed 283,666 person-years of follow-up. There was no association between ever-use of opioids and breast cancer recurrence (crude hazard ratio, 0.98; 95% confidence interval, 0.90-1.1; adjusted hazard ratio, 1.0; 95% confidence interval, 0.92-1.1), regardless of opioid type, strength, chronicity of use, or cumulative dose. Breast cancer recurrence rates were lower among users of strongly (but not weakly) immunosuppressive opioids, possibly because of channeling bias among those with a high competing risk, because mortality was higher among users of this drug type. CONCLUSIONS: This large, prospective cohort study provided no clinically relevant evidence of an association between opioid prescriptions and breast cancer recurrence. The current findings are important to cancer survivorship, because opioids are frequently used to manage pain associated with comorbid conditions.

Na+,HCO3- -cotransport is functionally upregulated during human breast carcinogenesis and required for the inverted pH gradient across the plasma membrane.

Metabolic and biochemical changes during breast carcinogenesis enhance cellular acid production. Extrusion of the acid load from the cancer cells raises intracellular pH, while it decreases extracellular pH creating an inverted pH gradient across the plasma membrane compared to normal cells and promoting cancer cell metabolism, proliferation, migration, and invasion. We investigated the effects of breast carcinogenesis on the mechanisms of cellular pH control using multicellular epithelial organoids freshly isolated from human primary breast carcinomas and matched normal breast tissue. Intracellular pH was measured by fluorescence microscopy, while protein expression was investigated by immunofluorescence imaging and immunoblotting. We found that cellular net acid extrusion increased during human breast carcinogenesis due to enhanced Na(+),HCO3 (-)-cotransport, which created an alkaline shift (~0.3 units of magnitude) in steady-state intracellular pH of human primary breast carcinomas compared to normal breast tissue. Na(+)/H(+)-exchange activity and steady-state intracellular pH in the absence of CO2/HCO3 (-) were practically unaffected by breast carcinogenesis. These effects were evident under both acidic (pH 6.8, representative of the tumor microenvironment) and physiological (pH 7.4) extracellular conditions. Protein expression of the Na(+),HCO3 (-)-cotransporter NBCn1 (SLC4A7), which has been linked to breast cancer susceptibility in multiple genome-wide association studies, was twofold higher in human breast carcinomas compared to matched normal breast tissue. Protein expression of the Na(+)/H(+)-exchanger NHE1 (SLC9A1) was markedly less affected. We propose that upregulated NBCn1 during human breast carcinogenesis contributes to the characteristic acid distribution within human breast carcinomas and thereby plays a pathophysiological role for breast cancer development and progression.

Statins and breast cancer prognosis: evidence and opportunities.

Much preclinical and epidemiological evidence supports the anticancer effects of statins. Epidemiological evidence does not suggest an association between statin use and reduced incidence of breast cancer, but does support a protective effect of statins--especially simvastatin--on breast cancer recurrence. Here, we argue that the existing evidence base is sufficient to justify a clinical trial of breast cancer adjuvant therapy with statins and we advocate for such a trial to be initiated without delay. If a protective effect of statins on breast cancer recurrence is supported by trial evidence, then the indications for a safe, well tolerated, and inexpensive treatment can be expanded to improve outcomes for breast cancer survivors. We discuss several trial design opportunities--including candidate predictive biomarkers of statin safety and efficacy--and offer solutions to the key challenges involved in the enrolment, follow-up, and analysis of such a trial.

Use of ß-blockers, angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, and risk of breast cancer recurrence: a Danish nationwide prospective cohort study.

PURPOSE: To estimate associations between use of ß-blockers, angiotensin-converting enzyme (ACE) inhibitors, or angiotensin receptor blockers (ARBs) and breast cancer recurrence in a large Danish cohort. PATIENTS AND METHODS: We enrolled 18,733 women diagnosed with nonmetastatic breast cancer between 1996 and 2003. Patient, treatment, and 10-year recurrence data were ascertained from the Danish Breast Cancer Cooperative Group registry. Prescription and medical histories were ascertained by linkage to the National Prescription Registry and Registry of Patients, respectively. ß-Blocker exposure was defined in aggregate and according to solubility, receptor selectivity, and individual drugs. ACE inhibitor and ARB exposures were defined in aggregate. Recurrence associations were estimated with multivariable Cox regression models in which time-varying drug exposures were lagged by 1 year. RESULTS: Compared with never users, users of any ß-blocker had a lower recurrence hazard in unadjusted models (unadjusted hazard ratio [HR] = 0.91; 95% CI, 0.81 to 1.0) and a slightly higher recurrence hazard in adjusted models (adjusted HR = 1.3; 95% CI, 1.1 to 1.5). Associations were similar for exposures defined by receptor selectivity and solubility. Although most individual ß-blockers showed no association with recurrence, metoprolol and sotalol were associated with increased recurrence rates (adjusted metoprolol HR = 1.5, 95% CI, 1.2 to 1.8; adjusted sotalol HR = 2.0, 95% CI, 0.99 to 4.0). ACE inhibitors were associated with a slightly increased recurrence hazard, whereas ARBs were not associated with recurrence (adjusted ACE inhibitor HR = 1.2, 95% CI, 0.97 to 1.4; adjusted ARBs HR = 1.1, 95% CI, 0.85 to 1.3). CONCLUSION: Our data do not support the hypothesis that ß-blockers attenuate breast cancer recurrence risk.