Characterization of a human breast cancer cell line, MCF-7/RU58R-1, resistant to the pure antiestrogen RU 58,668

Antioxidant, Antimicrobial, Cytotoxicity, and Larvicidal Activities of Selected Synthetic Bis-Chalcones

Plants are known to have numerous phytochemicals and other secondary metabolites with numerous pharmacological and biological properties. Among the various compounds, polyphenols, flavonoids, anthocyanins, alkaloids, and terpenoids are the predominant ones that have been explored for their biological potential. Among these, chalcones and bis-chalcones are less explored for their biological potential under in vitro experiments, cell culture models, and animal studies. In the present study, we evaluated six synthetic bis-chalcones that were different in terms of their aromatic cores, functional group substitution, and position of substitutions. The results indicated a strong antioxidant property in terms of DPPH and ABTS radical-scavenging potentials and ferric-reducing properties. In addition, compounds 1, 2, and 4 exhibited strong antibacterial activities against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Salmonella enteritidis. The disc diffusion assay values were indicative of the antibacterial properties of these compounds. Overall, the study indicated the antioxidant and antimicrobial properties of the compounds. Our preliminary studies point to the potential of this class of compounds for further in vivo investigation.

Control of IGFBP-2 Expression by Steroids and Peptide Hormones in Vertebrates

IGFBP-2 (1) has been described as a brain tumor oncogene (2) and is widely expressed in cancers from different origins (3-8). IGFBP-2 alone cannot cause malignant transformation, yet progression of brain tumors to higher grade (9) and also has been provided as a protective element in earlier stages of multistage colon carcinogenesis (10). Therefore, it is crucial to understand the factors that determine expression patterns of IGFBP-2 under normal and malignant conditions. The present review provides a comprehensive update of known factors that have an impact on expression of IGFBP-2.

Tocotrienols and breast cancer: the evidence to date

Breast cancer is the second most frequent cancer affecting women worldwide after lung cancer. The toxicity factor associated with synthetic drugs has turned the attention toward natural compounds as the primary focus of interest as anticancer agents. Vitamin E derivatives consisting of the well-established tocopherols and their analogs namely tocotrienols have been extensively studied due to their remarkable biological properties. While tocopherols have failed to offer protection, tocotrienols, in particular, α-, δ-, and γ-tocotrienols alone and in combination have demonstrated anticancer properties. The discovery of the antiangiogenic, antiproliferative, and apoptotic effects of tocotrienols, as well as their role as an inducer of immunological functions, not only reveals a new horizon as a potent antitumor agent but also reinforces the notion that tocotrienols are indeed more than antioxidants. On the basis of a transcriptomic platform, we have recently demonstrated a novel mechanism for tocotrienol activity that involves estrogen receptor (ER) signaling. In silico simulations and in vitro binding analyses indicate a high affinity of specific forms of tocotrienols for ERβ, but not for ERα. Moreover, we have demonstrated that specific tocotrienols increase ERβ translocation into the nucleus which, in turn, activates the expression of estrogen-responsive genes (MIC-1, EGR-1 and Cathepsin D) in breast cancer cells only expressing ERβ cells (MDA-MB-231) and in cells expressing both ER isoforms (MCF-7). The binding of specific tocotrienol forms to ERβ is associated with the alteration of cell morphology, caspase-3 activation, DNA fragmentation, and apoptosis. Furthermore, a recently concluded clinical trial seems to suggest that tocotrienols in combination with tamoxifen may have the potential to extend breast cancer-specific survival.

Insulin-like growth factor binding protein-2 is a novel therapeutic target associated with breast cancer

PURPOSE

Insulin-like growth factor (IGF) binding proteins (IGFBP) modulate interactions of IGF ligands with the IGF-I receptor. The role of IGFBPs, and specifically IGFBP-2, in breast cancer progression has been poorly defined. This study assesses the effect of IGFBP-2 on the behavior of human breast cancer using clinical specimens as well as in vitro and in vivo experimental systems.

EXPERIMENTAL DESIGN

4,181 primary invasive breast cancers and 120 benign breast tissue samples were identified for tumor tissue microarray construction and immunostained with IGFBP-2 antibody. Estrogen receptor-negative MDA-MB-231 cells constitutively overexpressing IGFBP-2 (MDA-MB-231BP-2) were created to assess the effect of IGFBP-2 gain-of-function. MDA-MB-468 cells, naturally expressing IGFBP-2, were used to determine the effect of IGFBP-2 loss-of-function using OGX-225, an antisense oligonucleotide drug candidate.

RESULTS

IGFBP-2 expression was significantly higher in breast cancer tissue compared with benign breast tissue. MDA-MB-231BP-2 cells grew more rapidly and were more resistant to paclitaxel both in vitro and in vivo compared with parental cells. OGX-225 decreased IGFBP-2 expression and attenuated the associated aggressive phenotype of MDA-MB-231BP-2 cells both in vitro and in vivo. Furthermore, OGX-225 inhibited the in vitro and in vivo growth of MDA-MB-468 cells.

CONCLUSIONS

This study provides evidence that IGFBP-2 expression is associated with breast cancer. Novel therapeutics targeting IGFBP-2, such as OGX-225, merit further evaluation.

Definition of functionally important mechanistic differences among selective estrogen receptor down-regulators

One subclass of antiestrogens, the selective estrogen receptor down-regulators (SERDs), have received considerable attention of late as they competitively inhibit estrogen binding and induce a rapid, proteasome-dependent degradation of the receptor. Contained within this class of molecules is the steroidal antiestrogen ICI182,780 (faslodex), recently approved for the treatment of metastatic cancer, and GW5638/DPC974, a SERD that is currently being evaluated in the clinic. Given that mechanistic differences between different selective estrogen receptor modulators have been translated into important clinical profiles, it was of interest to determine if the SERD subclass of ligands were likewise functionally or mechanistically distinguishable. In this study, we show that although the steroidal and nonsteroidal SERDs target ERalpha for degradation, the underlying mechanism(s) are different. Of note was the identification of a specific protein-protein interaction surface presented on ERalpha in the presence of the ICI182,780-activated receptor which is required for degradation. Interestingly, this surface is also presented on ERalpha in the presence of RU58,668, a SERD that is chemically distinct from ICI182,780. This surface is not required for GW5638-mediated degradation, and thus, this SERD seems to affect ERalpha down-regulation by a different mechanism. These data suggest that sequencing of therapies using drugs of this class is likely to be possible. Finally, because of the unmet need for orally active SERDS that function similarly to ICI182,780, we have used the insights from these mechanistic studies to develop and validate a high-throughput screen for compounds of this class with improved pharmaceutical properties.

Protein Kinase C alpha is a marker for antiestrogen resistance and is involved in the growth of tamoxifen resistant human breast cancer cells

Development of resistance to antiestrogen treatment in breast cancer patients is a serious therapeutic problem. The molecular mechanisms contributing to resistance are currently unclear; however it is known that increased activation of growth signaling pathways is involved. Protein Kinase C alpha (PKCalpha) is associated with a diverse range of cancers and is previously shown to be overexpressed in three out of four antiestrogen resistant breast cancer cell lines. In this study we investigated whether PKCalpha contributes to antiestrogen resistant growth. A panel of nine resistant cell lines was investigated, all of which displayed elevated levels of PKCalpha expression relative to parental MCF-7 cells. Stable PKCalpha overexpression in MCF-7 cells significantly reduced sensitivity to the antiestrogens, tamoxifen and ICI 182,780. Two resistant cell lines were chosen for further studies: tamoxifen resistant MCF-7/TAM(R)-1 (TAM(R)-1) and ICI 182,780 resistant MCF-7/182(R)-6 (182(R)-6). Treatment with the PKCalpha inhibitor Ro-32-0432 resulted in a preferential growth inhibition of these two cell lines relative to MCF-7 cells. Moreover, transient down-regulation of PKCalpha resulted in a 30-40% growth inhibition of TAM(R)-1 and 182(R)-6, while MCF-7 remained unaffected. Stable PKCalpha knock-down in TAM(R)-1 using small hairpin RNA, resulted in a tamoxifen sensitive "MCF-7-like" growth phenotype, while the same approach in 182(R)-6 cells did not alter their sensitivity to ICI 182,780. These results demonstrate a functional contribution of PKCalpha to tamoxifen resistant growth. Furthermore, our data suggest the potential for PKCalpha as a marker for antiestrogen resistance and as a promising therapeutic target in the treatment of tamoxifen resistant breast cancer.

Insulin-like growth factor binding protein 2 is a marker for antiestrogen resistant human breast cancer cell lines but is not a major growth regulator

Antiestrogens target the estrogen receptor and counteract the growth stimulatory action of estrogen on human breast cancer. However, acquired resistance to antiestrogens is a major clinical problem in endocrine treatment of breast cancer patients. To mimic acquired resistance, we have used a model system with the antiestrogen sensitive human breast cancer cell line MCF-7 and several antiestrogen resistant cell lines derived from the parental MCF-7 cell line. This model system was used to study the expression and possible involvement in resistant cell growth of insulin-like growth factor binding protein 2 (IGFBP-2). By an oligonucleotide based microarray, we compared the expression of mRNAs encoding insulin-like growth factor binding protein 1,2,3,4,5 and 6 (IGFBP-1 to -6) in the parental MCF-7 cell line to three human breast cancer cell lines, resistant to the antiestrogen ICI 182,780 (Faslodex/Fulvestrant). Only IGFBP-2 mRNA was overexpressed in all three resistant cell lines. Thus, we compared the IGFBP-2 protein expression in MCF-7 cells to nine antiestrogen resistant breast cancer cell lines, resistant to either ICI 182,780 or tamoxifen or RU 58,668 and found that IGFBP-2 was overexpressed in all nine resistant cell lines. Three of the resistant cell lines, resistant to different antiestrogens, were selected for further studies and IGFBP-2 overexpression was demonstrated at the mRNA level as well as the intra- and extracellular protein level. The objective of this study was to examine if IGFBP-2 is involved in growth of antiestrogen resistant human breast cancer cells. Therefore, IGFBP-2 expression was inhibited by antisense oligonucletides and siRNA. Specific inhibition of IGFBP-2 protein expression was achieved in MCF-7 and the three selected antiestrogen resistant cell lines, but no effect on resistant cell growth was observed. Thus, we were able to establish IGFBP-2 as a marker for antiestrogen resistant breast cancer cell lines, although IGFBP-2 was not a major contributor to the resistant cell growth.

Putranjivain A from Euphorbia jolkini inhibits proliferation of human breast adenocarcinoma MCF-7 cells via blocking cell cycle progression and inducing apoptosis

Putranjivain A, isolated from the whole plant of Euphorbia jolkini Bioss (Euphorbiaceae), was investigated for its antiproliferative activity in human breast adenocarcinoma MCF-7 cells. The results showed that putranjivain A inhibited the proliferation of MCF-7 by blocking cell cycle progression in the G0/G1 phase and inducing apoptosis. Enzyme-linked immunosorbent assay showed that putranjivain A increased the expression of p21/WAF1 concomitantly as MCF-7 cell underwent G0/G1 arrest. An enhancement in Fas/APO-1 and its two forms of ligands, membrane-bound Fas ligand (mFasL) and soluble Fas ligand (sFasL), might be responsible for the apoptotic effect induced by putranjivain A. Our study reports here for the first time that the induction of p21/WAF1 and the activity of Fas/Fas ligand apoptotic system may participate in the antiproliferative activity of putranjivain A in MCF-7 cells.