DNA double-strand break repair genes and oxidative damage in brain metastasis of breast cancer.

BACKGROUND: Breast cancer frequently metastasizes to the brain, colonizing a neuro-inflammatory microenvironment. The molecular pathways facilitating this colonization remain poorly understood. METHODS: Expression profiling of 23 matched sets of human resected brain metastases and primary breast tumors by two-sided paired t test was performed to identify brain metastasis-specific genes. The implicated DNA repair genes BARD1 and RAD51 were modulated in human (MDA-MB-231-BR) and murine (4T1-BR) brain-tropic breast cancer cell lines by lentiviral transduction of cDNA or short hairpin RNA (shRNA) coding sequences. Their functional contribution to brain metastasis development was evaluated in mouse xenograft models (n = 10 mice per group). RESULTS: Human brain metastases overexpressed BARD1 and RAD51 compared with either matched primary tumors (1.74-fold, P < .001; 1.46-fold, P < .001, respectively) or unlinked systemic metastases (1.49-fold, P = .01; 1.44-fold, P = .008, respectively). Overexpression of either gene in MDA-MB-231-BR cells increased brain metastases by threefold to fourfold after intracardiac injections, but not lung metastases upon tail-vein injections. In 4T1-BR cells, shRNA-mediated RAD51 knockdown reduced brain metastases by 2.5-fold without affecting lung metastasis development. In vitro, BARD1- and RAD51-overexpressing cells showed reduced genomic instability but only exhibited growth and colonization phenotypes upon DNA damage induction. Reactive oxygen species were present in tumor cells and elevated in the metastatic neuro-inflammatory microenvironment and could provide an endogenous source of genotoxic stress. Tempol, a brain-permeable oxygen radical scavenger suppressed brain metastasis promotion induced by BARD1 and RAD51 overexpression. CONCLUSIONS: BARD1 and RAD51 are frequently overexpressed in brain metastases from breast cancer and may constitute a mechanism to overcome reactive oxygen species-mediated genotoxic stress in the metastatic brain.

Prevention of carcinogenesis and inhibition of breast cancer tumor burden by dietary stearate.

Previous studies have shown that stearate (C18:0), a dietary long-chain saturated fatty acid, inhibits breast cancer cell neoplastic progression; however, little is known about the mechanism modulating these processes. We demonstrate that stearate, at physiological concentrations, inhibits cell cycle progression in human breast cancer cells at both the G(1) and G(2) phases. Stearate also increases cell cycle inhibitor p21(CIP1/WAF1) and p27(KIP1) levels and concomitantly decreases cyclin-dependent kinase 2 (Cdk2) phosphorylation. Our data also show that stearate induces Ras- guanosine triphosphate formation and causes increased phosphorylation of extracellular signal-regulated kinase (pERK). The MEK1 inhibitor, PD98059, reversed stearate-induced p21(CIP1/WAF1) upregulation, but only partially restored stearate-induced dephosphorylation of Cdk2. The Ras/mitogen-activated protein kinase/ERK pathway has been linked to cell cycle regulation but generally in a positive way. Interestingly, we found that stearate inhibits both Rho activation and expression in vitro. In addition, constitutively active RhoC reversed stearate-induced upregulation of p27(KIP1), providing further evidence of Rho involvement. To test the effect of stearate in vivo, we used the N-Nitroso-N-methylurea rat breast cancer carcinogen model. We found that dietary stearate reduces the incidence of carcinogen-induced mammary cancer and reduces tumor burden. Importantly, mammary tumor cells from rats on a stearate diet had reduced expression of RhoA and B as well as total Rho compared with a low-fat diet. Overall, these data indicate that stearate inhibits breast cancer cell proliferation by inhibiting key check points in the cell cycle as well as Rho expression in vitro and in vivo and inhibits tumor burden and carcinogen-induced mammary cancer in vivo.

Translational research in brain metastasis is identifying molecular pathways that may lead to the development of new therapeutic strategies.

Central nervous system (CNS) or brain metastasis is an emerging area of interest in organ-specific metastasis research. Lung and breast cancers are the most common types of primary tumors to develop brain metastases. This disease complication contributes significantly to the morbidity and mortality of both of these common cancers; as such, brain metastasis is designated an unmet medical need by the US Food and Drug Administration (FDA). Recently, an increase in incidence of CNS disease has been noted in the literature for breast cancer, while it has been an ongoing major complication from lung cancer. Progress in treating brain metastases has been hampered by a lack of model systems, a lack of human tissue samples, and the exclusion of brain metastatic patients from many clinical trials. While each of those is significant, the major impediment to effectively treating brain metastatic disease is the blood-brain barrier (BBB). This barrier excludes most chemotherapeutics from the brain and creates a sanctuary site for metastatic tumors. Recent findings on the biology of this disease and translational leads identified by molecular studies are discussed in this article.

Stearate preferentially induces apoptosis in human breast cancer cells.

Stearic acid (stearate) is an 18-carbon saturated fatty acid that has been shown to inhibit invasion and proliferation and induce apoptosis in various human cell types. The specificity of stearate-induced apoptosis for cancerous versus noncancerous breast cells has not been examined, and the mechanism underlying stearate-induced apoptosis is unknown. Morphological analysis, cell viability, and caspase-3 activity assays demonstrated that stearate activated apoptosis preferentially in cancerous breast cells in a time- and dose-dependent manner. Inhibition of de novo diacylgycerol synthesis or protein kinase C (PKC) blocked stearate-induced caspase-3 activity, indicating the involvement of a novel or classical PKC isozyme. To our knowledge this is the first study showing that stearate induces apoptosis preferentially in breast cancer cells and implicates protein kinase C in the signaling cascade. These results raise the possibility of dietary stearate having a beneficial role in the prevention or treatment of breast cancer.

Dietary stearate reduces human breast cancer metastasis burden in athymic nude mice.

Stearate is an 18-carbon saturated fatty acid found in many foods in the western diet, including beef and chocolate. Stearate has been shown to have anti-cancer properties during early stages of neoplastic progression. However, previous studies have not investigated the effect of dietary stearate on breast cancer metastasis. In this study, we present evidence that exogenously supplied dietary stearate dramatically reduces the size of tumors that formed from injected human breast cancer cells within the mammary fat pads of athymic nude mice by approximately 50% and partially inhibits breast cancer cell metastasis burden in the lungs in this mouse model system. This metastatic inhibition appears to be independent of primary tumor size, as stearate fed animals that had primary tumors comparable in size to littermates fed either a safflower oil enriched diet or a low fat diet had reduced lung metastasis. Also stearate fed mice sub-groups had different primary tumor sizes but no difference in metastasis. This anti-metastasis effect may be due, at least in part, to the ability of stearate to induce apoptosis in these human breast cancer cells. Overall, this study suggests the possibility of dietary manipulation with selected long-chain saturated fatty acids such as stearate as a potential adjuvant therapeutic strategy for breast cancer patients wishing to maximize the suppression of metastatic disease.

Cardiac rehabilitation for the treatment of women with chest pain and normal coronary arteries.

OBJECTIVE: To explore cardiac rehabilitation (CR) as a treatment for psychological and physiological morbidity in women with chest pain and normal coronary arteries (cardiac syndrome X). DESIGN: Sixty-four women aged 57.3+/-8.6 years (mean +/- SD) with cardiac syndrome X were randomly assigned to an 8-week phase III CR exercise program or symptom monitoring control. All women completed the Hospital Anxiety and Depression Scale, Health Anxiety Questionnaire, and Short Form-36 before and after intervention and at the 8-week follow-up. CR patients underwent physical assessment before and after CR. RESULTS: After CR, patients demonstrated improved symptom severity (2.0+/-0.8 vs 1.26+/-1.1, P=0.009), Hospital Anxiety and Depression Scale depression score (8.0+/-3.4 vs 6.4+/-3.1, P=0.04), total Health Anxiety Questionnaire score (12.0+/-5.5 vs 9.5+/-6.0, P=0.008), health worry (4.5+/-3.1 vs 3.52+/-2.4, P=0.025) and interference (2.4+/-1.8 vs 1.6+/-1.8, P=0.004), SF-36 physical functioning (53.1+/-20.4 vs 62.3+/-23.9, P = 0.006), energy (36.3+/-20.7 vs 49.8+/-19.1, P<0.001), pain (49.9+/-20.7 vs 58.1+/-22.9, P=0.028), and general health (48.8+/-17.9 vs 57.6+/-17.0, P=0.01) not found among the control women. Improvements were maintained at follow-up. CR patients showed significant improvements in Shuttle Walk Test performance (326.8+/-111.0 vs 423.6+/-133.2 m, P<0.001), diastolic blood pressure (84.7+/-9.4 vs 79.7+/-7.3 mm Hg, P=0.007), and body mass index (29.1+/-6.0 vs 28.4+/-6.17 kg/m2, P=0.003). CONCLUSIONS: An 8-week phase III CR program improves exercise tolerance, quality of life, psychological morbidity, symptom severity, and cardiovascular risk factors in women with cardiac syndrome X.