Benford Mafuvadze

Apigenin prevents development of medroxyprogesterone acetate-accelerated 7,12-dimethylbenz(a)anthracene-induced mammary tumors in Sprague-Dawley rats

The use of progestins as a component of hormone replacement therapy has been linked to an increase in breast cancer risk in postmenopausal women. We have previously shown that medroxyprogesterone acetate (MPA), a commonly administered synthetic progestin, increases production of the potent angiogenic factor vascular endothelial growth factor (VEGF) by tumor cells, leading to the development of new blood vessels and tumor growth. We sought to identify nontoxic chemicals that would inhibit progestin-induced tumorigenesis. We used a recently developed progestin-dependent mammary cancer model in which tumors are induced in Sprague–Dawley rats by 7,12-dimethylbenz(a)anthracene (DMBA) treatment. The flavonoid apigenin, which we previously found to inhibit progestin-dependent VEGF synthesis in human breast cancer cells in vitro, significantly delayed the development of, and decreased the incidence and multiplicity of, MPA-accelerated DMBA-induced mammary tumors in this animal model. Whereas apigenin decreased the occurrence of such tumors, it did not block MPA-induced intraductal and lobular epithelial cell hyperplasia in the mammary tissue. Apigenin blocked MPA-dependent increases in VEGF, and suppressed VEGF receptor-2 (VEGFR-2) but not VEGFR-1 in regions of hyperplasia. No differences were observed in estrogen or progesterone receptor (ER/PR) levels, or the number of estrogen receptor–positive cells, within the mammary gland of MPA-treated animals administered apigenin, MPA-treated animals, and placebo treated animals. However, the number of progesterone receptor–positive cells was reduced in animals treated with MPA or MPA and apigenin compared with those treated with placebo. These findings suggest that apigenin has important chemopreventive properties for those breast cancers that develop in response to progestins. Cancer Prev Res; 4(8); 1316–24. ©2011 AACR.

Apigenin blocks induction of vascular endothelial growth factor mRNA and protein in progestin-treated human breast cancer cells.

Objective: The results of recent clinical trials indicate that hormone therapy with estrogen and progestin is associated with higher risk of breast cancer in postmenopausal women than treatment with estrogen alone or placebo. This observation is consistent with studies showing that progestins stimulate the expression of vascular endothelial growth factor (VEGF), which in turn stimulates angiogenesis. The objective of this study was to examine whether apigenin, a natural flavone, inhibits the progestin-dependent induction of VEGF in human breast cancer cells. Methods: T47-D human breast cancer cells were treated with medroxyprogesterone acetate (MPA; 10 nM) or other synthetic progestins in the presence or absence of antiprogestin RU-486 and variable doses of apigenin (1-100 &mgr;M). BT-474 cells were also treated with MPA ± 100 &mgr;M apigenin. Secreted VEGF was quantified by enzyme-linked immunosorbent assay, and total cellular VEGF mRNA was quantified by reverse transcriptase polymerase chain reaction. The expression of VEGF receptor-1 (flt), VEGF receptor-2 (flk), progesterone receptor, and estrogen receptor-&agr; was also quantified by Western blot analysis and/or reverse transcriptase polymerase chain reaction. Results: Apigenin (50 or 100 &mgr;M) prevented progestin-dependent induction of both VEGF mRNA and protein and reduced progesterone receptor levels in T47-D cells. Apigenin also blocked MPA-dependent secretion of VEGF from BT-474 cells. mRNA levels of progesterone and estrogen receptor-&agr; were unaffected by apigenin, which did exert somewhat suppressive, although complex, effects on VEGF receptor expression in MPA-treated T47-D cells. Conclusions: Apigenin blocks progestin-dependent induction of VEGF mRNA and protein and broadly inhibits the ability of progestins to alter the expression of other components of the angiogenesis pathway, including progesterone receptor and VEGF receptors, in human breast cancer cells. Further studies are warranted to explore the potential of apigenin as a chemopreventive agent in postmenopausal women exposed to oral progestins.

Luteolin inhibits progestin-dependent angiogenesis, stem cell-like characteristics, and growth of human breast cancer xenografts.

AbstractPurposeClinical trials and epidemiological evidence have shown that combined estrogen/progestin hormone replacement therapy, but not estrogen therapy alone, increases breast cancer risk in post-menopausal women. Previously we have shown that natural and synthetic progestins, including the widely used synthetic progestin medroxyprogesterone acetate (MPA), increase production of a potent angiogenic factor, vascular endothelial growth factor (VEGF), in human breast cancer cells, potentially providing an explanation for progestin’s mechanism of action. Here, we tested the effects of luteolin (LU), a flavonoid commonly found in fruits and vegetables, on inhibiting progestin-dependent VEGF induction and angiogenesis in human breast cancer cells, inhibiting stem cell-like characteristics, as well as breast cancer cell xenograft tumor growth in vivo and expression of angiogenesis markers.MethodsViability of both T47-D and BT-474 cells was measured using sulforhodamine B assays. Enzyme-linked immunosorbent assays were used to monitor VEGF secretion from breast cancer cells. Progestin-dependent xenograft tumor growth was used to determine LU effects in vivo. CD31 immunohistochemistry was used to determine blood-vessel density in xenograft tumors. CD44 expression, aldehyde dehydrogenase activity, and mammosphere-formation assays were used to monitor stem cell-like characteristics of breast cancer cells.ResultsLuteolin treatment reduced breast cancer cell viability, progestin-dependent VEGF secretion from breast cancer cells, and growth of MPA-dependent human breast cancer cell xenograft tumors in nude mice. LU treatment also decreased xenograft tumor VEGF expression and blood-vessel density. Furthermore, LU blocked MPA-induced acquisition of stem cell-like properties by breast cancer cells.ConclusionsLuteolin effectively blocks progestin-dependent human breast cancer tumor growth and the stem cell-like phenotype in human breast cancer cells.

Effects of Dietary Apigenin on Tumor Latency, Incidence and Multiplicity in a Medroxyprogesterone Acetate- Accelerated 7,12-Dimethylbenz(a)anthracene- Induced Breast Cancer Model

Medroxyprogesterone acetate (MPA) is a synthetic progestin commonly administered to postmenopausal women for hormone replacement therapy and has been associated with increased risk of breast cancer. MPA has been shown to accelerate the development of mammary tumors in a 7,12-dimethylbenz(a)anthracene (DMBA)-induced breast cancer animal model. Previously, we have shown that intraperitoneally administered apigenin effectively treated and prevented the progression of MPA-accelerated breast cancer in DMBA-induced and xenograft mammary cancer models. Here we used the DMBA model to examine the chemopreventive effect of dietary apigenin against MPA-accelerated tumors with 3 different levels of apigenin (0.02%, 0.1%, and 0.5% w/w) incorporated into a phytoestrogen-free diet. Results showed that 0.1% dietary apigenin reduced MPA-dependent tumor incidence; however, the same dietary level increased tumor multiplicity in animals that developed tumors. Neither 0.02% nor 0.5% dietary apigenin reduced MPA-dependent tumor incidence or latency, and tumor multiplicity increased significantly in response to 0.5% apigenin. These results contrast with previous chemopreventive effects observed when apigenin was administered intraperitoneally, suggesting that route of administration may influence its action. Consequently, until further research clarifies the effect of dietary apigenin on progestin-accelerated mammary tumors, caution should be exercised when considering the flavonoid as a dietary supplement for preventing hormone-dependent breast cancer.

The impact of traditional and religious practices on the spread of Ebola in West Africa: time for a strategic shift

The current Ebola outbreak in West Africa is the largest ever recorded since the discovery of the virus. While several factors may have contributed to perpetuation of the viral spread among affected communities, the role of traditional and religious practices in the spread of the disease is unquestionable. The World Health Organization (WHO) reported that a majority of Ebola cases in some communities can be linked to traditional burial practices. Additionally, one of the major challenges in controlling the spread of the disease has been notable resistance against prescribed scientific ways of combating the transmission of Ebola in some affected communities for cultural and religious reasons. Herein, we identified notable religious and traditional practices in West Africa that potentially contributed to the spread of Ebola and exacerbated the current outbreak. We further discussed ways that the identified practices could be modified to levels that leave them within culturally acceptable standards and, at the same time, effective at preventing the spread of Ebola. One of our proposed strategies is deliberate targeting of leaders of traditional and religious institutions in community-directed preventive programs. It emerged from the current outbreak in West Africa that traditional and spiritual healers can significantly contribute to spreading of Ebola. We, thus, propose specifically targeting traditional and spiritual healers for awareness and increasing their collaboration with public health official in fighting against Ebola. It is our contention that traditional and spiritual healers and leaders can play a significant role in fostering mutual trust between health officials and affected communities. As custodians of cultural practices, traditional leaders can also play a significant role in promotion, monitoring, and implementation of prescribed preventive measures against the spread of Ebola.

Cholesterol biosynthesis inhibitors as potent novel anti-cancer agents: suppression of hormone-dependent breast cancer by the oxidosqualene cyclase inhibitor RO 48-8071

In most human breast cancers, tumor cell proliferation is estrogen dependent. Although hormone-responsive tumors initially respond to anti-estrogen therapies, most of them eventually develop resistance. Our goal was to identify alternative targets that might be regulated to control breast cancer progression. Sulforhodamine B assay was used to measure the viability of cultured human breast cancer cell lines exposed to various inhibitors. Protein expression in whole-cell extracts was determined by Western blotting. BT-474 tumor xenografts in nude mice were used for in vivo studies of tumor progression. RO 48-8071 ([4′-[6-(Allylmethylamino)hexyloxy]-4-bromo-2′-fluorobenzophenone fumarate]; RO), a small-molecule inhibitor of oxidosqualene cyclase (OSC, a key enzyme in cholesterol biosynthesis), potently reduced breast cancer cell viability. In vitro exposure of estrogen receptor (ER)-positive human breast cancer cells to pharmacological levels of RO or a dose close to the IC50 for OSC (nM) reduced cell viability. Administration of RO to mice with BT-474 tumor xenografts prevented tumor growth, with no apparent toxicity. RO degraded ERα while concomitantly inducing the anti-proliferative protein ERβ. Two other cholesterol-lowering drugs, Fluvastatin and Simvastatin, were less effective in reducing breast cancer cell viability and were found not to induce ERβ. ERβ inhibition or knockdown prevented RO-dependent loss of cell viability. Importantly, RO had no effect on the viability of normal human mammary cells. RO is a potent inhibitor of hormone-dependent human breast cancer cell proliferation. The anti-tumor properties of RO appear to be in part due to an off-target effect that increases the ratio of ERβ/ERα in breast cancer cells.

Breast Cancer Knowledge and Awareness among High School and College Students in Mid-Western USA

Early detection of breast cancer and its subsequent treatment lead to better patient prognosis and survival rates. However, despite advanced screening and detection techniques, the disease all too frequently remains undetected until it has reached an advanced stage. Despite a number of means of disseminating breast cancer awareness, such as public health programs, public and private media and the internet, breast cancer remains a major health problem which exerts a tremendous economic burden on the health care system. Consequently, promoting early awareness of the disease to students at both high school and college levels might potentially lead to improved health habits later in life. This study investigated breast cancer awareness among college and high school students. A self-administered questionnaire was given to 355 high school students and 132 college students in a mid-western area of the USA to determine their perceptions of breast cancer, risk factors and the need for breast self-examination. Despite many annual efforts to disseminate breast cancer awareness and the availability of information about the disease, our study showed that both college and high school students have a poor understanding of breast cancer. Most participants, however, were receptive to the provision of more information at school. Based on our findings, we recommend more breast cancer awareness programs targeting high school and college students. Breast cancer awareness could be included as a component of the high school curriculum, as well as via the internet and public health programs.

Natural and synthetic progestins enrich cancer stem cell-like cells in hormone-responsive human breast cancer cell populations in vitro

Clinical trials and studies have shown that combination estrogen/progestin hormone replacement therapy, but not estrogen therapy alone or placebo, increases breast cancer risk in postmenopausal women. Using animal models, we have previously shown that both natural and synthetic progestins (including medroxyprogesterone acetate [MPA], a synthetic progestin used widely in the clinical setting) accelerate the development of breast tumors in vivo and increase their metastasis to lymph nodes. Based on these observations, we have hypothesized that progestin-induced breast cancer tumor growth and metastasis may be mediated by an enrichment of the cancer stem cell (CSC) pool. In this study, we used T47-D and BT-474 hormone-responsive human breast cancer cells to examine the effects of progestin on phenotypic and functional markers of CSCs in vitro. Both natural and synthetic progestins (10 nM) significantly increased protein expression of CD44, an important CSC marker in tumor cells. MPA increased the levels of both CD44 variants v3 and v6 associated with stem cell functions. This induction of CD44 was blocked by the antiprogestin RU-486, suggesting that this process is progesterone receptor (PR) dependent. CD44 induction was chiefly progestin dependent. Because RU-486 can bind other steroid receptors, we treated PR-negative T47-DCO-Y cells with MPA and found that MPA failed to induce CD44 protein expression, confirming that PR is essential for progestin-mediated CD44 induction in T47-D cells. Further, MPA treatment of T47-D cells significantly increased the activity of aldehyde dehydrogenase (ALDH), another CSC marker. Finally, two synthetic progestins, MPA and norethindrone, significantly increased the ability of T47-D cells to form mammospheres, suggesting that enrichment of the CD44high, ALDHbright subpopulation of cancer cells induced by MPA exposure is of functional significance. Based on our observations, we contend that exposure of breast cancer cells to synthetic progestins leads to an enrichment of the CSC pool, supporting the development of progestin-accelerated tumors in vivo.

Luteolin suppresses development of medroxyprogesterone acetate-accelerated 7,12-dimethylbenz(a)anthracene-induced mammary tumors in Sprague-Dawley rats

Postmenopausal women undergoing hormone-replacement therapy containing both progestins and estrogens are at an increased risk of developing breast cancer compared with women taking estrogen alone. We recently demonstrated that medroxyprogesterone acetate, a progestin commonly used for hormone-replacement therapy, accelerates development of mammary carcinogenesis in 7,12-dimethylbenz(a)anthracene‑treated Sprague-Dawley rats. Synthetic antiprogestins used to block the deleterious effects of progestins, are themselves associated with toxic side-effects. In order to circumvent this, we used the aforementioned model to identify less toxic natural compounds that may prevent the development of progestin-accelerated tumors. Luteolin, a naturally-occurring flavonoid commonly found in fruits and vegetables, has previously been shown to possess anticancer properties. In our studies, both low (1 mg/kg) and high (25 mg/kg) doses of luteolin significantly suppressed progestin-dependent increases in tumor incidence, while increasing tumor latency and reducing the occurrence of large (>300 mm3) mammary tumors. However, an intermediate dose of luteolin (10 mg/kg), while suppressing the development of large tumors, did not affect either tumor incidence or latency. Immunohistochemical analysis of tumor tissues revealed that all concentrations of luteolin (1, 10, and 25 mg/kg) significantly reduced levels of VEGF within tumors. The suppressive effects of luteolin on tumor incidence and volume, together with its ability to reduce VEGF and blood vessels, persisted even after treatment was terminated. This suggests that luteolin possesses anti‑angiogenic properties which could mechanistically explain its capacity to control tumor progression. Thus luteolin may be a valuable, non-toxic, naturally-occurring anticancer compound which may potentially be used to combat progestin-accelerated mammary tumors.

Cholesterol biosynthesis inhibitor RO 48-8071 suppresses growth of hormone-dependent and castration-resistant prostate cancer cells.

Standard treatment for primary prostate cancer includes systemic exposure to chemotherapeutic drugs that target androgen receptor or antihormone therapy (chemical castration); however, drug-resistant cancer cells generally emerge during treatment, limiting the continued use of systemic chemotherapy. Patients are then treated with more toxic standard therapies. Therefore, there is an urgent need for novel and more effective treatments for prostate cancer. The cholesterol biosynthetic pathway is an attractive therapeutic target for treating endocrine-dependent cancers because cholesterol is an essential structural and functional component of cell membranes as well as the metabolic precursor of endogenous steroid hormones. In this study, we have examined the effects of RO 48-8071 (4′-[6-(allylmethylamino)hexyloxy]-4-bromo-2′-fluorobenzophenone fumarate; Roche Pharmaceuticals internal reference: RO0488071) (RO), which is an inhibitor of 2, 3-oxidosqualene cyclase (a key enzyme in the cholesterol biosynthetic pathway), on prostate cancer cells. Exposure of both hormone-dependent and castration-resistant human prostate cancer cells to RO reduced prostate cancer cell viability and induced apoptosis in vitro. RO treatment reduced androgen receptor protein expression in hormone-dependent prostate cancer cells and increased estrogen receptor β (ERβ) protein expression in both hormone-dependent and castration-resistant prostate cancer cell lines. Combining RO with an ERβ agonist increased its ability to reduce castration-resistant prostate cancer cell viability. In addition, RO effectively suppressed the growth of aggressive castration-resistant human prostate cancer cell xenografts in vivo without any signs of toxicity to experimental animals. Importantly, RO did not reduce the viability of normal prostate cells in vitro. Our study is the first to demonstrate that the cholesterol biosynthesis inhibitor RO effectively suppresses growth of human prostate cancer cells. Our findings suggest that cholesterol biosynthesis inhibitors such as RO, when used in combination with commonly used chemotherapeutic drugs or ERβ specific ligands, could represent a novel therapeutic approach to prevent the growth of prostate cancer tumors.