Mai N. Brooks

Nitroxyl inhibits breast tumor growth and angiogenesis

Nitroxyl (HNO) can inhibit the glycolytic enzyme glyceraldehyde 3‐phosphate dehydrogenase (GAPDH). Because of the importance of glycolysis in many malignant cells, we thus propose that HNO can adversely affect tumor growth. This hypothesis was tested using in vitro and in vivo models of breast cancer. We report here for the first time that HNO suppresses the proliferation of both estrogen receptor (ER)‐positive and ER‐negative human breast cancer cell lines, in a dose dependent manner. Mice treated with HNO either injected into the tumor itself or via the intraperitoneal approach had smaller xenograft tumor size. In addition to significantly decreased blood vessel density in the HNO‐treated tumors, we observed lower levels of circulating serum vascular endothelial growth factor (VEGF). Accordingly, there was a decrease in total HIF‐1α (hypoxia‐inducible factor) protein in HNO‐treated tumor cells. Further studies showed inhibition of GAPDH activity in HNO‐treated human breast cancer cell lines and in HNO‐treated tumor tissue derived from xenografts. One explanation for the multiplicity of actions observed after HNO treatment could be the effect from the initial inhibition of GAPDH, providing a potential therapeutic avenue based upon blocking glycolysis resulting in decreased HIF‐1α, thus leading to angiogenesis inhibition. Therefore, HNO appears to act via mechanism(s) different from those of existing breast cancer drugs, making it a potential candidate to overcome known and emerging drug resistance pathways.

A pilot clinical study of short-term isoflavone supplements in breast cancer patients.

Abstract: Many laboratory-based studies have shown that soy can suppress breast cancer proliferation. However, given the recent controversy generated by animal experiments that soy may under certain conditions stimulate breast cancer growth, we decided to carry out a pilot clinical trial in order to elucidate any interaction(s) between short-term isoflavone supplement administration and breast cancer growth. After a core-needle biopsy established the diagnosis of breast cancer, 17 patients were administered soy isoflavone tablets for two weeks. This surgically based study provided the unique opportunity to make objective observations based on human breast cancer tissues and blood obtained prior to and after isoflavone supplement treatment in the same patient. Twenty-six historical control cases with similar characteristics to the experimental patients were selected for comparison. We observed that the apoptosis/mitosis ratios in isoflavone-treated cancer specimens were not significantly different from those of control untreated cancer specimens. Furthermore, there appeared to be a statistically nonsignificant trend towards cancer growth inhibition in the isoflavone treatment group, as manifested by higher apoptosis/mitosis ratios compared with those from the control untreated group. Ex vivo/in vitro assays using serum from breast cancer patients prior to and at the conclusion of soy treatment reveal no significant proliferative changes on both breast cancer cells and endothelial cells. We concluded that the effect of soy on breast cancer deserves further studies in larger clinical trials.

Green Tea Extract Modulates Actin Remodeling via Rho Activity in an In vitro Multistep Carcinogenic Model

Alteration of actin polymerization and loss of actin filaments is a marker of cellular dedifferentiation and early malignant transformation. To study this phenomenon, an in vitro human urothelial model consisting of two cell lines, HUC-PC and MC-T11, were incorporated into the study design. These two cell lines have different malignant transformation potential. The effect of green tea extract (GTE), a potential anticancer agent, on actin remodeling was investigated. Upon exposure to the carcinogen 4-aminobiphenyl (4-ABP), the untransformed HUC-PC undergoes malignant transformation whereas the transformed MC-T11 progresses from noninvasive to invasive tumor. GTE induces actin polymerization in MC-T11 cells in a dose-responsive manner, but this effect is less obvious in the untransformed, more differentiated HUC-PC cells, which natively have higher actin polymerization status. In contrast, GTE antagonizes carcinogen 4-ABP induced actin depolymerization and stress fiber disruption in HUC-PC cells. In MC-T11 cells, GTE inhibits 4-ABP induced motility by increasing cell adhesion and focal adhesion complex formation. The effect of GTE on actin remodeling seems to be mediated by the stimulation of small GTP-binding protein Rho activity, because C3 exoenzyme, a specific inhibitor for Rho, blocks GTE-mediated Rho activation and stress fiber formation in MC-T11 cells. This study shows that GTE exerts an effect on cytoskeletal actin remodeling and provides further support for the use of GTE as a chemopreventive agent.

Expression Pattern of the Novel Gene EG-1 in Cancer

Purpose: We recently discovered a novel gene responsive to tumor-conditioned media: endothelial-derived gene 1 (EG-1). Its transcript has been shown to be present in epithelial cells, as well as in endothelial cells. In this study, we examined the levels of EG-1 protein expression in breast, colon, prostate, and lung cancers, which constitute the four most common solid malignancies in the United States. Experimental Design: Polyclonal antibodies were generated that recognize the EG-1 peptide. These antibodies were used in immunoblot analysis, as well as immunohistochemistry of multiple human clinical specimens of cancer. Results: In immunoblots of whole cell lysates, EG-1 antibodies revealed the presence of a 22-kDa peptide. Immunohistochemistry of breast, colon, and prostate specimens showed higher levels of EG-1 peptides in cancer tissues, in comparison with their benign counterparts. However, EG-1 expression was minimal in both benign and malignant lung tissues. Conclusions: Here, we demonstrated that the expression of EG-1 is elevated in cancerous in comparison to benign epithelial cells, as seen in immunohistochemistry of human pathological specimens. These observations collectively support the hypothesis that the novel gene EG-1 is associated with the malignant phenotype of the common epithelial-derived cancers of the breast, colon, and prostate.

The Novel Gene EG-1 Stimulates Cellular Proliferation

We recently discovered a novel gene and named it endothelial-derived gene 1 (EG-1). Previously, we have shown that the expression of EG-1 is significantly elevated in the epithelial cells of breast cancer, colorectal cancer, and prostate cancer. Here, we report that EG-1 can stimulate cellular proliferation. Transfection experiments which overexpressed the full-length EG-1 gene in human embryonic kidney HEK-293 cells or human breast cancer cell lines resulted in significantly increased in vitro proliferation, in comparison with transfection with empty vectors. On the other hand, small interfering RNA cotransfection resulted in inhibition of proliferation. S.c. xenograft assays were carried out in a severe combined immunodeficient mouse model. We found that injection of high EG-1 expressing HEK-293 clones resulted in significantly larger tumors, in comparison with clones carrying the empty vectors. To further clarify the function of this gene, we investigated its interaction with Src and members of the mitogen-activated protein kinase (MAPK) family. Immunoprecipitation with anti-Src antibody, followed by immunoblotting with anti-EG-1 antibody, showed an association between these two molecules. Overexpression of EG-1 was correlated with activation of the following kinases: extracellular signal-regulated kinases 1 and 2, c-jun-NH2-kinase, and p38. These observations collectively support the hypothesis that the novel gene EG-1 is a positive stimulator of cellular proliferation, and may possibly be involved in signaling pathways involving Src and MAPK activation.

Nipple Fluid Basic Fibroblast Growth Factor in Patients with Breast Cancer

Purpose: It has been shown that early detection of breast cancer could save lives. Recently, there has been increasing interest in nipple fluid as a potential supplemental avenue for breast cancer diagnosis. Experimental Design: In this study, we determined the levels of an angiogenic factor basic fibroblast growth factor (bFGF) in the nipple fluid of healthy subjects as well as patients with benign breast conditions, those at high risk for breast cancer, and patients with active breast cancer. ELISAs were used to measure bFGF. Results: Nipple fluid bFGF levels were as follows (mean ± SE): 158 ± 17 pg/mL from benign breasts, 561 ± 277 pg/mL from high-risk breasts, and 1,343 ± 441 pg/mL from cancerous breasts. One-way ANOVA showed that the bFGF levels from cancerous breasts were significantly higher than those from benign and high-risk breasts (P = 0.0001 and P = 0.0193, respectively). After logarithmic transformation was applied to the data, high-risk breast bFGF levels were higher than those from benign breasts (P = 0.0028). With a cutoff level of 250 pg/mL, the sensitivity was 79.2%, specificity was 82.5%, and correct diagnosis was 66.4%. The area under the receiver operating characteristic curve was 0.86. Conclusions: We conclude that nipple fluid bFGF levels are progressively elevated in high-risk and cancerous breasts compared with benign breasts. The sensitivity and specificity of this test are promising compared with current breast cancer screening methods, and this test deserves further studies with larger clinical trials. Potential areas of usefulness include the detection of breast cancer risk or breast cancer, as well as the monitoring and/or prediction of the antiangiogenic effect of preventive therapies. (Cancer Epidemiol Biomarkers Prev 2005;14(12):2995–8)

The Use of Oxytocin in Nipple Fluid Aspiration

Abstract: It has been shown that early detection of breast cancer saves lives. Recently there has been increasing interest in nipple aspirate fluid as a potential avenue for breast cancer diagnosis. One major challenge regarding studies of nipple aspirate fluid is the ability to obtain adequate samples. Here we describe the use of nasal oxytocin in a group of volunteer women in order to increase the yield of nipple aspirate fluid. 

Targeted inhibition of EG-1 blocks breast tumor growth.

EG-1 is a gene product that is significantly elevated in human breast cancer tissues. Previously, we have shown that EG-1 overexpression stimulates cellular proliferation both in vitro and in vivo. Here, we ask whether this molecule can be targeted for experimental therapeutic purpose. siRNA lentivirus and polyclonal antibody were designed to suppress EG-1 expression. These agents were then used in cell culture proliferation assays and breast tumor xenograft models. Serum and urine from breast cancer patients were also analyzed for the presence of EG-1 peptide. We report here for the first time that endogenous EG-1 can be targeted to inhibit breast tumor growth. This inhibition, whether delivered via siRNA lentivirus or polyclonal antibody, resulted in decreased cellular proliferation in culture and smaller xenografts in mice. The effects were shown in both ER (estrogen receptor)-positive human breast cancer MCF-7 cells, as well as in ER-negative MDA-MB-231 cells. Furthermore, we detected soluble EG-1 in serum and urine of breast cancer patients. These observations demonstrate that EG-1 is relevant to human breast cancer, and is a molecular target worthy of translational efforts into effective breast cancer therapy.