A maternal diet high in n − 6 polyunsaturated fats alters mammary gland development, puberty onset, and breast cancer risk among female rat offspring

We hypothesized that feeding pregnant rats with a high-fat diet would increase both circulating 17β-estradiol (E2) levels in the dams and the risk of developing carcinogen-induced mammary tumors among their female offspring. Pregnant rats were fed isocaloric diets containing 12% or 16% (low fat) or 43% or 46% (high fat) of calories from corn oil, which primarily contains the n − 6 polyunsaturated fatty acid (PUFA) linoleic acid, throughout pregnancy. The plasma concentrations of E2 were significantly higher in pregnant females fed a high n − 6 PUFA diet. The female offspring of these rats were fed with a laboratory chow from birth onward, and when exposed to 7,12-dimethylbenz(a)anthracene had a significantly higher mammary tumor incidence (60% vs. 30%) and shorter latency for tumor appearance (11.4 ± 0.5 weeks vs. 14.2 ± 0.6 weeks) than the offspring of the low-fat mothers. The high-fat offspring also had puberty onset at a younger age, and their mammary glands contained significantly higher numbers of the epithelial structures that are the targets for malignant transformation. Comparable changes in puberty onset, mammary gland morphology, and tumor incidence were observed in the offspring of rats treated daily with 20 ng of E2 during pregnancy. These data, if extrapolated to humans, may explain the link among diet, early puberty onset, mammary parenchymal patterns, and breast cancer risk, and indicate that an in utero exposure to a diet high in n − 6 PUFA and/or estrogenic stimuli may be critical for affecting breast cancer risk.

A single nucleotide polymorphism in the RAD51 gene modifies cancer risk in BRCA2 but not BRCA1 carriers

BRCA1 and BRCA2 carriers are at increased risk for both breast and ovarian cancer, but estimates of lifetime risk vary widely, suggesting their penetrance is modified by other genetic and/or environmental factors. The BRCA1 and BRCA2 proteins function in DNA repair in conjunction with RAD51. A preliminary report suggested that a single nucleotide polymorphism in the 5′ untranslated region of RAD51 (135C/G) increases breast cancer risk in BRCA1 and BRCA2 carriers. To investigate this effect we studied 257 female Ashkenazi Jewish carriers of one of the common BRCA1 (185delAG, 5382insC) or BRCA2 (6174delT) mutations. Of this group, 164 were affected with breast and/or ovarian cancer and 93 were unaffected. RAD51 genotyping was performed on all subjects. Among BRCA1 carriers, RAD51-135C frequency was similar in healthy and affected women [6.1% (3 of 49) and 9.9% (12 of 121), respectively], and RAD-135C did not influence age of cancer diagnosis [Hazard ratio (HR) = 1.18 for disease in RAD51-135C heterozygotes, not significant]. However, in BRCA2 carriers, RAD51-135C heterozygote frequency in affected women was 17.4% (8 of 46) compared with 4.9% (2 of 41) in unaffected women (P = 0.07). Survival analysis in BRCA2 carriers showed RAD51-135C increased risk of breast and/or ovarian cancer with an HR of 4.0 [95% confidence interval 1.6–9.8, P = 0.003]. This effect was largely due to increased breast cancer risk with an HR of 3.46 (95% confidence interval 1.3–9.2, P = 0.01) for breast cancer in BRCA2 carriers who were RAD51-135C heterozygotes. RAD51 status did not affect ovarian cancer risk. These results show RAD51-135C is a clinically significant modifier of BRCA2 penetrance, specifically in raising breast cancer risk at younger ages.

Combined effect of tumor necrosis factor-related apoptosis-inducing ligand and ionizing radiation in breast cancer therapy

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potent endogenous activator of the cell death pathway and functions by activating the cell surface death receptors 4 and 5 (DR4 and DR5). TRAIL is nontoxic in vivo and preferentially kills neoplastically transformed cells over normal cells by an undefined mechanism. Radiotherapy is a common treatment for breast cancer as well as many other cancers. Here we demonstrate that ionizing radiation can sensitize breast carcinoma cells to TRAIL-induced apoptosis. This synergistic effect is p53-dependent and may be the result of radiation-induced up-regulation of the TRAIL-receptor DR5. Importantly, TRAIL and ionizing radiation have a synergistic effect in the regression of established breast cancer xenografts. Changes in tumor cellularity and extracellular space were monitored in vivo by diffusion-weighted magnetic resonance imaging (diffusion MRI), a noninvasive technique to produce quantitative images of the apparent mobility of water within a tissue. Increased water mobility was observed in combined TRAIL- and radiation-treated tumors but not in tumors treated with TRAIL or radiation alone. Histological analysis confirmed the loss of cellularity and increased numbers of apoptotic cells in TRAIL- and radiation-treated tumors. Taken together, our results provide support for combining radiation with TRAIL to improve tumor eradication and suggest that efficacy of apoptosis-inducing cancer therapies may be monitored noninvasively, using diffusion MRI.

Hormonal prevention of breast cancer: Mimicking the protective effect of pregnancy

Full term pregnancy early in life is the most effective natural protection against breast cancer in women. Rats treated with chemical carcinogen are similarly protected by a previous pregnancy from mammary carcinogenesis. Proliferation and differentiation of the mammary gland does not explain this phenomenon, as shown by the relative ineffectiveness of perphenazine, a potent mitogenic and differentiating agent. Here, we show that short term treatment of nulliparous rats with pregnancy levels of estradiol 17β and progesterone has high efficacy in protecting them from chemical carcinogen induced mammary cancers. Because the mammary gland is exposed to the highest physiological concentrations of estradiol and progesterone during full term pregnancy, it is these elevated levels of hormones that likely induce protection from mammary cancer. Thus, it appears possible to mimic the protective effects of pregnancy against breast cancer in nulliparous rats by short term specific hormonal intervention.

Epidermal growth factor-induced nuclear factor κB activation: A major pathway of cell-cycle progression in estrogen-receptor negative breast cancer cells

The epidermal growth factor (EGF) family of receptors (EGFR) is overproduced in estrogen receptor (ER) negative (−) breast cancer cells. An inverse correlation of the level of EGFR and ER is observed between ER− and ER positive (+) breast cancer cells. A comparative study with EGFR-overproducing ER− and low-level producing ER+ breast cancer cells suggests that EGF is a major growth-stimulating factor for ER− cells. An outline of the pathway for the EGF-induced enhanced proliferation of ER− human breast cancer cells is proposed. The transmission of mitogenic signal induced by EGF–EGFR interaction is mediated via activation of nuclear factor κB (NF-κB). The basal level of active NF-κB in ER− cells is elevated by EGF and inhibited by anti-EGFR antibody (EGFR-Ab), thus qualifying EGF as a NF-κB activation factor. NF-κB transactivates the cell-cycle regulatory protein, cyclin D1, which causes increased phosphorylation of retinoblastoma protein, more strongly in ER− cells. An inhibitor of phosphatidylinositol 3 kinase, Ly294–002, blocked this event, suggesting a role of the former in the activation of NF-κB by EGF. Go6976, a well-characterized NF-κB inhibitor, blocked EGF-induced NF-κB activation and up-regulation of cell-cycle regulatory proteins. This low molecular weight compound also caused apoptotic death, predominantly more in ER− cells. Thus Go6976 and similar NF-κB inhibitors are potentially novel low molecular weight therapeutic agents for treatment of ER− breast cancer patients.

NF-κB activation and interleukin 6 production in fibroblasts by estrogen receptor-negative breast cancer cell-derived interleukin 1α

Several angiogenic factors and extracellular matrix-degrading enzymes that promote invasion and metastasis of cancer are produced by stromal fibroblasts that surround cancer cells. The expression of genes that code for some of these proteins is regulated by the transcription factor NF-κB. In this report, we demonstrate that conditioned medium (CM) from estrogen receptor (ER)-negative but not ER-positive breast cancer cells induces NF-κB in fibroblasts. In contrast, CM from both ER-positive and ER-negative breast cancer cells induces NF-κB in macrophages and endothelial cells. NF-κB activation in fibroblasts was accompanied by induction of interleukin 6 (IL-6) and urokinase plasminogen activator (uPA), both of which promote angiogenesis and metastasis. A survey of cytokines known for their ability to induce NF-κB identified IL-1α as the factor responsible for NF-κB activation in fibroblasts. Analysis of primary breast carcinomas revealed the presence of IL-1α transcripts in majority of lymph node-positive breast cancers. These results along with the known role of IL-1α and IL-6 in osteoclast formation provide insight into the mechanism of metastasis and hypercalcemia in advanced breast cancers.

Increased expression of preprotachykinin-I and neurokinin receptors in human breast cancer cells: Implications for bone marrow metastasis

Neuropeptides are implicated in many tumors, breast cancer (BC) included. Preprotachykinin-I (PPT-I) encodes multiple neuropeptides with pleiotropic functions such as neurotransmission, immune/hematopoietic modulation, angiogenesis, and mitogenesis. PPT-I is constitutively expressed in some tumors. In this study, we investigated a role for PPT-I and its receptors, neurokinin-1 (NK-1) and NK-2, in BC by using quantitative reverse transcription–PCR, ELISA, and in situ hybridization. Compared with normal mammary epithelial cells (n = 2) and benign breast biopsies (n = 21), BC cell lines (n = 7) and malignant breast biopsies (n = 25) showed increased expression of PPT-I and NK-1. NK-2 levels were high in normal and malignant cells. Specific NK-1 and NK-2 antagonists inhibited BC cell proliferation, suggesting autocrine and/or intercrine stimulation of BC cells by PPT-I peptides. NK-2 showed no effect on the proliferation of normal cells but mediated the proliferation of BC cells. Cytosolic extracts from malignant BC cells enhanced PPT-I translation whereas extracts from normal mammary epithelial cells caused no change. These enhancing effects may be protein-specific because a similar increase was observed for IL-6 translation and no effect was observed for IL-1α and stem cell factor. The data suggest that PPT-I peptides and their receptors may be important in BC development. Considering that PPT-I peptides are hematopoietic modulators, these results could be extended to understand early integration of BC cells in the bone marrow, a preferred site of metastasis. Molecular signaling transduced by PPT-I peptides and the mechanism that enhances translation of PPT-I mRNA could lead to innovative strategies for BC treatments and metastasis.

Immunization of metastatic breast cancer patients with a fully synthetic globo H conjugate: A phase I trial

The carbohydrate antigen globo H commonly found on breast cancer cells is a potential target for vaccine therapy. The objectives of this trial were to determine the toxicity and immunogenicity of three synthetic globo H-keyhole limpet hemocyanin conjugates plus the immunologic adjuvant QS-21. Twenty-seven metastatic breast cancer patients received five vaccinations each. The vaccine was well tolerated, and no definite differences were observed among the three formulations. Serologic analyses demonstrated the generation of IgM antibody titers in most patients, with minimal IgG antibody stimulation. There was significant binding of IgM antibodies to MCF-7 tumor cells in 16 patients, whereas IgG antibody reactivity was observed in a few patients. There was evidence of complement-dependent cytotoxicity in several patients. Affinity column purification supported the specificity of IgM antibodies for globo H. On the basis of these data, globo H will constitute one component of a polyvalent vaccine for evaluation in high-risk breast cancer patients.

Mutation detection by highly sensitive methods indicates that p53 gene mutations in breast cancer can have important prognostic value.

Human cancer cells with a mutated p53 tumor-suppressor gene have a selective growth advantage and may exhibit resistance to ionizing radiation and certain chemotherapeutic agents. To examine the prognostic value of mutations in the p53 gene, a cohort of 90 Midwestern Caucasian breast cancer patients were analyzed with methodology that detects virtually 100% of all mutations. The presence of a p53 gene mutation was by far the single most predictive indicator for recurrence and death (relative risks of 4.7 and 23.2, respectively). Direct detection of p53 mutations had substantially greater prognostic value than immunohistochemical detection of p53 overexpression. Analysis of p53 gene mutations may permit identification of a subset of breast cancer patients who, despite lack of conventional indicators of poor prognosis, are at high risk of early recurrence and death.

Ligand-directed retroviral targeting of human breast cancer cells.

We explored the feasibility of designing retroviral vectors that can target human breast cancer cells with characteristic receptors via ligand-receptor interaction. The ecotropic Moloney murine leukemia virus envelope was modified by insertion of sequences encoding human heregulin. Ecotropic virus, which normally does not infect human cells, when pseudotyped with the modified envelope protein now crosses species to infect human breast cancer cell lines that overexpress HER-2 (human epidermal growth factor receptor; also called ERBB2) and HER-4 (also called ERBB4), while human breast cancer cell lines expressing low levels of these receptors remain resistant to infection. Since about 20% of human breast cancers overexpress HER-2 and some of breast cancer cell lines overexpress both HER-2 and HER-4, cell-specific targeting of retroviral vectors may provide a different approach for in vivo gene therapy of this type of breast cancer.