Altered apoptotic response in MCF 10A cells treated with the equine estrogen metabolite, 4-hydroxyequilenin

Estrogen- and estrogen receptor (ER)-mediated cisplatin chemoresistance in cancer

Cisplatin is a platinum-based chemotherapeutic drug used in the standard treatment of various solid cancers including testicular, bladder, head and neck, cervical and ovarian cancer. Although successful clinical responses are observed in patients following initial cisplatin treatment, resistance to cisplatin ultimately develops in most patients, leading to therapeutic failure. Multiple molecular mechanisms contributing to cisplatin resistance in cancer cells have been identified to date. In this review, we discuss the effect of estrogen, estrogen receptors (ERs) and estrogen-related receptors (ERRs) on cisplatin resistance in various cancer types. We highlight that estrogen treatment or increased expression of ERs or ERRs are generally associated with higher cisplatin resistance in cancer in vitro, mostly due to decreased caspase activity, increased anti-apoptotic protein levels such as BCL-2, higher drug efflux and higher levels of antioxidant enzymes. Targeted inhibition of ERs or estrogen production in combination with cisplatin treatment thus can be a useful strategy to overcome chemoresistance in certain cancer types. Estrogen levels and ER status can also be considered to identify cancer patients with a high potential of therapy response against cisplatin. A better mechanistic understanding of the involvement of estrogen, ERs and ERRs in the development of cisplatin resistance is needed to improve the management of cancer treatment.

Further lead optimization on Bax activators: Design, synthesis and pharmacological evaluation of 2-fluoro-fluorene derivatives for the treatment of breast cancer

To further pursue potent Bax activators with better safety profiles for the treatment of breast cancer, structural optimization was conducted based on lead compound CYD-4-61 through several strategies, including scaffold hopping on the 2-nitro-fluorene ring, replacement of the nitro group with bioisosteres to avoid potential toxicity, and further optimization on the upper pyridine by exploring diverse alkylamine linkers as a tail or replacing the pyridine with bioisosteric heterocycles. F-containing compound 22d (GL0388) exhibited a good balance between the activity and toxicity, displaying submicromolar activities against a variety of cancer cell lines with 5.8-10.7-fold selectivity of decreased activity to MCF-10A human mammary epithelial cell line. Compound 22d dose-dependently blocked colony formation of breast cancer cells and prevented the migration and invasion of MDA-MB-231 cells. Mechanism of action studies indicate that 22d activated Bax, rendering its insertion into mitochondrial membrane, thereby leading to cytochrome c release from the mitochondria into the cytoplasm, subsequently inducing release of apoptotic biomarkers. Further in vivo efficacy studies of 22d in human breast cancer xenografts arisen from MDA-MB-231 cells demonstrated that this drug candidate significantly suppressed tumor growth, indicating the therapeutic promise of this class of compounds for the treatment of breast cancer as well as the potential for developing F-radiolabeled imaging ligands as anticancer chemical probes.

Marine bioactive compound dieckol induces apoptosis and inhibits the growth of human pancreatic cancer cells PANC-1

Pancreatic cancer, which threatens the global population, is a very aggressive disease with an increased mortality rate. Regarding the types of cancer, pancreatic cancer is prone to display significant resistance to conventional therapy, therefore there 5-year survival rate is only 2% to 9%. Bioactive metabolites of marine algae such as polysaccharides, chitin, carternoids, and sterols possess immense pharmacological properties and tend to be promising alternatives for cancer treatment. Dieckol is one such polyphenolic bioactive compound extracted from brown algae Ecklonia cava, which is proven to possess antioxidant, anti-inflammatory, antibacterial, antidiabetic properties. Therefore in the present study, we analyzed the anticancer property of dieckol on PANC-1 pancreatic carcinoma cells. The cytotoxicity property of dieckol against PANC-1 cells was assessed with 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide assay, and cell morphological analysis. The generation of reactive oxygen species by dieckol on PANC-1 was analyzed with DCFH-DA staining and confirmed by quantifying antioxidants levels in untreated and dieckol-treated PANC-1 cells. The induction of apoptosis was further evaluated with different staining techniques such as Rhodamine 123 staining, acridine orange/ethidium bromide staining, DAPI staining, propidium iodide staining and was confirmed by estimating the protein expression of apoptotic genes, Bax and Bcl2. Cell adhesion assay and estimation of inflammatory cytokines were performed to detect the inhibitory effect of dieckol against cancer cell progression. It is further confirmed by analyzing cancer cell progression proteins, that is, proliferating cell nuclear antigen and cyclin D1 expressions in untreated and dieckol-treated PANC-1 cells. Our overall results authentically prove dieckol persuasively induces apoptosis and inhibits the progression of human pancreatic cancer cells in vitro, suggesting dieckol as a potent marine-based phytochemical to treat pancreatic cancer.

Antiproliferative, cytotoxic and apoptotic activity of the bentonite transformation of sesquiterpene lactone glaucolide B to 5β-hydroxy-hirsutinolide on tumor cell lines

Numerous chemical compounds isolated from medicinal plants have anti-tumor properties, the effects of which on human cancer cells are currently under study. Here, the chemical transformation of glaucolide B were performed to produce a hirsutinolide. The antiproliferative and cytotoxic activity of 5β-hydroxy-hirsutinolide and its ability to induce apoptosis in tumor and non-tumor cells (lymphocyte cultures and the normal HaCaT cell line) (1a) are reported. We ascertained that compound 1a exerts an inhibitory effect on the proliferation of SK-Lu-1, MDA-MB-231 and CaSki cells in a dose-dependent manner at IC₅₀ values of 15, 18 and 30 μg/ml, respectively. The proliferation of lymphocyte cells treated with 1a was inhibited at a range from 14 to 28%, but the HaCaT cell line was not affected, suggesting that compound 1a has a selective action. Cytotoxic activity was evaluated by detecting the lactate dehydrogenase enzyme in supernatants from tumor and non-tumor cells. The 1a compound exhibited low or null cytotoxic activity in both cell types. The presence of apoptotic bodies and active caspase-3 in tumor cell lines treated with compound 1a are suggestive of apoptotic cell death. Notably, flow cytometry evaluation did not detect the presence of active caspase-3 on lymphocytes treated with this compound. Our results suggest that 5β-hydroxy-hirsutinolide is a molecule with antiproliferative activity and low cytotoxic activity in tumor and non-tumor cells; this induces apoptotic cell death in tumor cell lines through selective action. Hence, this lactone could be considered a molecule worthy of study as an anti-tumor agent with therapeutic potential.

Antiproliferative, Cytotoxic, and Apoptotic Activity of Steroidal Oximes in Cervicouterine Cell Lines

Steroidal sapogenins have shown antiproliferative effects against several tumor cell lines; and their effects on human cancer cells are currently under study. Changes in the functionality on the steroidal structure make it possible to modify the biological activity of compounds. Herein, we report the synthesis and in vitro antitumor activity of two steroidal oxime compounds on cervical cancer cells. These derivatives were synthesized from the steroidal sapogenin diosgenin in good yields. The in vitro assays show that the steroidal oximes show significant antiproliferative activity compared to the one observed for diosgenin. Cell proliferation, cell death, and the cytotoxic effects were determined in both cervical cancer cells and human lymphocytes. The cancer cells showed apoptotic morphology and an increased presence of active caspase-3, providing the notion of a death pathway in the cell. Significantly, the steroidal oximes did not exert a cytotoxic effect on lymphocytes.

Effects of the conjugated equine estrogen/bazedoxifene tissue-selective estrogen complex (TSEC) on mammary gland and breast cancer in mice

A tissue-selective estrogen complex (TSEC), combining a selective estrogen receptor modulator, bazedoxifene (BZA), with conjugated equine estrogen (CEE), represents a novel strategy of menopausal hormone therapy without involving a progestin. We hypothesized that the antiestrogenic properties of BZA can also block the estrogenic effects of CEE on breast tissue and thereby prevent breast cancer in women. To test our hypothesis, the effects of estradiol (E(2)), CEE, and BZA on mammary gland and breast cancer xenografts were assessed in mouse models. In immature castrate mice, BZA completely blocked CEE- or E(2)-stimulated ductal and terminal end bud growth of mammary gland as well as estrogen-responsive gene expression. As a positive control, E(2) stimulated tumor growth in nude mice bearing MCF-7 xenografts. This effect was completely blocked by BZA as were E(2)-stimulated expression of PR, pS2 (trefoil factor 1), cMyc, and AREG; the enhancement of Ki67 and proliferating cell nuclear antigen (PCNA); and the antiapoptotic effect. CEE was much less potent than E(2) in stimulating Ki67, reducing apoptosis, and stimulating gene expression, but all effects were blocked by BZA. Unexpectedly, CEE alone, even at high doses, did not stimulate tumor growth. As confirmation of its absorption and deconjugation, CEE caused a 6-fold increase in uterine weight and stimulation of gene expression. These data support our hypothesis that the net effect of the CEE/BZA TSEC is to block estrogen action in benign and malignant breast tissue. These findings provide a rationale for a clinical study to determine whether this TSEC prevents breast cancer in women.

Lonicera caerulea and Vaccinium myrtillus fruit polyphenols protect HaCaT keratinocytes against UVB-induced phototoxic stress and DNA damage

BACKGROUND

Sunlight is a very potent environmental factor in skin pathogenesis and can induce skin cancer. UVB irradiation is known to cause oxidative stress, inflammation and especially DNA damage. Topical application of agents with UV absorbing, antioxidant and anti-inflammatory activities is a successful strategy in the protection of the skin against UV-caused damage.

OBJECTIVE

To examine the ability of the phenolic fraction of Lonicera caerulea and Vaccinum myrtillus fruits to moderate UVB-induced damage.

METHODS

HaCaT keratinocytes, a well-established in vitro system for investigations on UV radiation induced cell damage, were used to assess the effects of pre- and post-treatment with L. caerulea (LCE) and V. myrtillus (VME) phenolic fractions (5-50 mg/l) on keratinocyte damage induced by a solar simulator (295-315 nm).

RESULTS

In this study, a model of UVB-induced damage to HaCaT was established. LCE and VME efficiently reduced the extent of DNA breakage (especially at concentrations of 25 and 10 mg/l) together with caspase-3 and -9 activity and DNA laddering induced by UVB (100 or 200 mJ/cm(2)). LCE and VME significantly decreased RONS generation and partially diminished IL-6 expression. LCE pre-treatment also prevented keratinocytes proliferation.

CONCLUSION

The results suggest that the phenolic fraction of L. caerulea and V. myrtillus fruits suppress UVB-caused injury to keratinocytes. These results now need to be demonstrated in vivo.

Determination of absolute configurations of 4-hydroxyequilenin-cytosine and -adenine adducts by optical rotatory dispersion, electronic circular dichroism, density functional theory calculations, and mass spectrometry

Estrogen components of some hormone replacement formulations have been implicated in the initiation of breast cancer. Some of these formulations contain equine estrogens such as equilin and equilenin that are metabolized to the genotoxic catechol 4-hydroxyequilenin (4-OHEN). Auto-oxidation generates the o-quinone form that reacts with dC and dA in oligodeoxynucleotides to form unusual stable cyclic bulky adducts, with four different stereoisomers identified for each base adduct. The dC and dA adducts have the same unsaturated bicyclo[3.3.1]nonane type linkage site with identical stereochemical characteristics. Stereochemical effects may play an important part in the biological consequences of the formation of 4-OHEN-DNA adducts, and the assignment of the absolute configurations of the stereoisomeric 4-OHEN-dC and -dA adducts is therefore needed to understand structure-function relationships. We used density functional theory (DFT) to compute the specific optical rotations and electronic circular dichroism (ECD) spectra of the four 4-OHEN-C stereoisomers, and the results were compared with experimentally measured optical rotatory dispersion (ORD) and ECD spectra. The predicted ORD curves for the four stereoisomeric base adducts reproduced the shapes and signs of experimental spectra in the transparent spectral region. The stereochemistry of the C3' atom was determined by comparison of the calculated and experimental ORD and ECD spectra, and the stereochemistry of C2' was determined by mass spectrometric methods. Combining the ORD and mass spectrometry data, the absolute configurations of the four 4-OHEN-C and the stereochemically identical -dC adducts have been identified. The molecular architecture of the linkage site at the 4-OHEN-C/A and 4-OHEN-dC/dA is identical, and it is shown that the deoxyribose group does not substantially contribute to the optical activities. The absolute configurations of the 4-OHEN-dA adducts were thus deduced by comparing the experimental ORD with computed ORD values of 4-OHEN-A adducts.

Flavonolignans from Silybum marianum moderate UVA-induced oxidative damage to HaCaT keratinocytes

BACKGROUND

UV radiation from sunlight is a very potent environmental risk factor in the pathogenesis of skin cancer. Exposure to UV light, especially the UVA part, provokes the generation of reactive oxygen species (ROS), which induce oxidative stress in exposed cells. Topical application of antioxidants is a successful strategy for protecting the skin against UV-caused oxidative damage.

OBJECTIVE

In this study, silybin (SB) and 2,3-dehydrosilybin (DS) (1-50 micromol/l), flavonolignan components of Silybum marianum, were tested for their ability to moderate UVA-induced damage.

METHODS

Human keratinocytes HaCaT were used as an appropriate experimental in vitro model, to monitor the effects of SB and DS on cell viability, proliferation, intracellular ATP and GSH level, ROS generation, membrane lipid peroxidation, caspase-3 activation and DNA damage.

RESULTS

Application of the flavonolignans (1-50 micromol/l) led to an increase in cell viability of irradiated (20 J/cm(2)) HaCaT keratinocytes. SB and DS also suppressed intracellular ATP and GSH depletion, ROS production and peroxidation of membrane lipids. UVA-induced caspases-3 activity/activation was suppressed by treatment with SB and DS. Lower concentrations of both compounds (10 micromol/l) significantly reduced cellular DNA single strand break formation.

CONCLUSION

Taken together, the results suggest that these flavonolignans suppress UVA-caused oxidative stress and may be useful in the treatment of UVA-induced skin damage.

The effect of chelerythrine on cell growth, apoptosis, and cell cycle in human normal and cancer cells in comparison with sanguinarine

We compared the effects of chelerythrine (CHE) and sanguinarine (SA) on human prostate cancer cell lines (LNCaP and DU-145) and primary culture of human gingival fibroblasts. CHE and SA treatment of cell lines for 24 h resulted in (1) inhibition of cell viability in a dose-dependent manner in all tested cells (as evaluated by MTT test and bromodeoxyuridine incorporation assay); (2) dose-dependent increase in DNA damage in all tested cells (as evaluated by DNA comet assay); (3) changes in apoptosis (assessed by western blot analysis and TUNEL assay); and (4) significant induction of cyclin kinase inhibitors p21(Waf1/Cip1) and p27(Kip1) in prostate cancer cells (identified by western blot analysis). Our study demonstrates that CHE had significant cytotoxic effect, independent of p53 and androgen status, on human prostate cancer cell lines. Normal gingival fibroblasts and DU-145 cells were more sensitive to the treatment with both alkaloids than were LNCaP cells. CHE and SA may be prospective natural molecules for use in the treatment of prostate cancer owing to their involvement in apoptosis and cell cycle regulation.

Response of human mammary epithelial cells to DNA damage induced by 4-hydroxyequilenin: Lack of p53-mediated G1 arrest

Long-term exposure to synthetic and endogenous estrogens has been associated with the development of cancer in several tissues. One potential mechanism of estrogen carcinogenesis involves catechol formation and these catechols are further oxidized to electrophilic/redox active o-quinones, which have the potential to both initiate and promote the carcinogenic process. 4-Hydroxyequilenin (4-OHEN), a major phase I metabolite of several estrogens present in Premarin, is considerably more cytotoxic, carcinogenic, and mutagenic as compared to the catechol estrogen metabolites of endogenous estrogens. Previously, we showed that 4-OHEN autoxidized to an o-quinone and caused a variety of damage to DNA. Allowing more time between the induction of DNA damage and the entry of a damaged cell into the DNA synthetic phase of the cell cycle protects that cell from mutagenesis. Central to this response is the establishment of a G1 checkpoint. This checkpoint is mediated by the cyclin-dependent kinase inhibitor p21WAF1, a direct downstream target for transcriptional activation by p53. In this study, we investigated this signaling pathway. Surprisingly, exposure of the human MCF-10A immortalized nontransformed mammary epithelial cell line to 4-OHEN did not induce a p53-induced G1 arrest. A 24 h treatment with 4-OHEN significantly induced p53 and p21WAF1 protein expression at 10 and 20 microM, as well as significantly induced the transactivation of a p53-luciferase reporter gene at 20 microM. Significant decreases in cell proliferation were also observed with concentrations of 5 microM and higher of 4-OHEN. However, 4-OHEN did not induce a G1 checkpoint and cells with damaged DNA accumulated in the S phase. This S phase delay could be beneficial for the survival of the damaged cells which could contribute to the carcinogenic process.