Differences in C/EBPs in normal tissue and papillomas of the larynx

Transcription factors belonging to the family of CAAT enhancer binding proteins (C/EBPs) programme differentiation in a wide variety of cells. We asked about the expression of C/EBPs in squamous epithelium. Using immunohistochemistry, C/EBPalpha and C/EBPbeta were easily detected in tissue sections from normal larynx or laryngeal papillomas, benign tumours with a papillomavirus aetiology and characterized by abnormal differentiation. A temporal expression of these C/EBPs occured as keratinocytes differentiated. In both tissues, C/EBPbeta appeared to be exclusively nuclear. In normal tissue, the greatest amount of C/EBPbeta was present in the spinous layer, and much less occurred in the granular layer. The basal layer of the laryngeal papillomas contained the most C/EBPbeta. Less was present in the spinous layer. Little C/EBPbeta was in the granular layer. Much C/EBPalpha was in the cytoplasm in both tissues. In normal tissue, nuclear C/EBPalpha staining was virtually absent in the basal layer, and became present in the spinous layer. Nuclear C/EBPalpha was randomly distributed in all layers in papillomas. Using immunoblots and Southwestern blots, we detected abundant truncated isoforms of C/EBPalpha in the papillomas. Since differentiation of many tissues is determined by the relative amounts of different C/EBPs, our data supports a role for C/EBPs in the differentiation of squamous epithelium.

BRCA1 and BRCA2 as molecular targets for phytochemicals indole-3-carbinol and genistein in breast and prostate cancer cells

Indole-3-carbinol (I3C) and genistein are naturally occurring chemicals derived from cruciferous vegetables and soy, respectively, with potential cancer prevention activity for hormone-responsive tumours (e.g., breast and prostate cancers). Previously, we showed that I3C induces BRCA1 expression and that both I3C and BRCA1 inhibit oestrogen (E2)-stimulated oestrogen receptor (ER-α) activity in human breast cancer cells. We now report that both I3C and genistein induce the expression of both breast cancer susceptibility genes (BRCA1 and BRCA2) in breast (MCF-7 and T47D) and prostate (DU-145 and LNCaP) cancer cell types, in a time- and dose-dependent fashion. Induction of the BRCA genes occurred at low doses of I3C (20 μM) and genistein (0.5–1.0 μM), suggesting potential relevance to cancer prevention. A combination of I3C and genistein gave greater than expected induction of BRCA expression. Studies using small interfering RNAs (siRNAs) and BRCA expression vectors suggest that the phytochemical induction of BRCA2 is due, in part, to BRCA1. Functional studies suggest that I3C-mediated cytoxicity is, in part, dependent upon BRCA1 and BRCA2. Inhibition of E2-stimulated ER-α activity by I3C and genistein was dependent upon BRCA1; and inhibition of ligand-inducible androgen receptor (AR) activity by I3C and genistein was partially reversed by BRCA1-siRNA. Finally, we provide evidence suggesting that the phytochemical induction of BRCA1 expression is due, in part, to endoplasmic reticulum stress response signalling. These findings suggest that the BRCA genes are molecular targets for some of the activities of I3C and genistein.

Suppression of breast cancer invasion and migration by indole-3-carbinol: associated with up-regulation of BRCA1 and E-cadherin/catenin complexes

Indole-3-carbinol (I3C) is a compound occurring naturally in cruciferous vegetables and has been indicated as a promising agent in preventing breast cancer development and progression. In the present study we have investigated the effect of I3C on the cell migration and invasion behavior in estrogen receptor positive MCF-7 and estrogen receptor negative MDA-MB-468 human breast cancer cell lines. Both MCF-7 and MDA-MB-468 were poorly invasive cell lines and exhibited modest invasion and migration capacity in the presence of fibronectin as the chemoattractant. I3C (50 or 100 microM) elicited a significant inhibition of in vitro cell adhesion, migration, and invasion as well as in vivo lung metastasis formation in both cell lines. I3C also suppressed the 17beta-estradiol stimulated migration and invasion in estrogen-responsive MCF-7 cells. These results indicate that anti-invasion and antimigration activities of I3C occur via estrogen-independent and estrogen-dependent pathways. Moreover, I3C significantly caused a dose-dependent increase in E-cadherin, three major catenins (alpha, beta, and gamma-catenin) and BRCA1 expression. Our current finding is the first demonstration that I3C can activate the function of invasion suppressor molecules associated with the suppression of invasion and migration in breast cancer cells. Thus, clinical application of I3C may contribute to the potential benefit for suppression of breast cancer invasion and metastasis.

Indole-3-carbinol is a negative regulator of estrogen receptor-alpha signaling in human tumor cells

Estrogen, via its binding to the estrogen receptor (ER), plays an important role in breast cancer cell proliferation and tumor development. Indole-3-carbinol (I3C), a compound occurring naturally in cruciferous vegetables, exhibits a potent antitumor activity via its regulation of estrogen activity and metabolism. This study was designed to determine the effect of I3C on the potential to inhibit the ER-alpha. Using a reporter gene driven by the estrogen receptor, I3C (10-125 micromol/L) significantly repressed the 17ss-estradiol (E2)-activated ER-alpha signaling in a dose-dependent manner. I3C and breast cancer susceptibility gene 1 (BRCA1) synergistically inhibited transcriptional activity of ER-alpha. Moreover, I3C down-regulated the expression of the estrogen-responsive genes, pS2 and cathepsin-D, and up-regulated BRCA1. The inhibitory effects of I3C did not contribute to its cytotoxic effects because these activities were observed at less than toxic concentrations. These results further suggest that antitumor activities of I3C are associated not only with its regulation of estrogen activity and metabolism, but also its modulation of ER transcription activity.

Altered growth and viral gene expression in human papillomavirus type 16-containing cancer cell lines treated with progesterone

This study explores interactions between high-risk human papillomavirus type 16 (HPV-16) and the female sex hormone progesterone in the growth of tumor cells and viral oncogene expression. For both the cervical cancer cell line CaSki containing integrated HPV-16 DNA and the laryngeal carcinoma cell line HEp-2 transfected with HPV-16 DNA, prolonged progesterone treatment enhances their colony formation efficiency both on plastic surface and in soft agar. In contrast, progesterone has no effect on the HPV-negative cervical cancer cell line C-33A or the untransfected HEp-2 parental cells. Progesterone increases HPV-16 E6/E7 oncogene transcription in both HPV-16-containing cell lines. A detectable increase requires at least 3 days of treatment, and this delayed response may be due, at least in part, to increased stability of viral transcripts as determined by actinomycin D treatment. The progesterone antagonist RU 486 and nuclease-resistant oligomers containing HPV-16 progesterone response element are able to abrogate the enhancement by progesterone on cell growth and E6/E7 gene transcription. Taken together, these results support the notion that progesterone can be a cofactor in HPV-related malignancies.

Anti-estrogenic activities of indole-3-carbinol in cervical cells: implication for prevention of cervical cancer

BACKGROUND

Cervical cancer constitutes the second most common cancer in women. Estrogen promotes development of cervical cancer in cells infected with high risk human papillomaviruses (HPVs). We asked whether the phytochemical indole-3-carbinol (I3C) has anti-estrogenic activities in cervical cells with the goal of preventing cancer in HPV infected cells.

MATERIALS AND METHODS

Using the cervical cancer cell line CaSki, we evaluated expression of HPV and cytochrome p450 (CYP) enzymes by Northern, RNase protection or quantitative RT-PCR. I3C binding to estrogen receptor was measured by competition with estradiol. Estrogen metabolites were measured by gas chromarography-mass spectrometry (GC-MS).

RESULTS

Estradiol increased expression of HPV oncogenes whereas I3C and the estrogen metabolite 2-hydroxyestrone (2-OHE) abrogated the estrogen-increased expression of HPV oncogenes. Both I3C and 2-OHE competed with estradiol for estrogen receptor binding. I3C enhanced gene expression of CYP enzymes responsible for 2-hydroxylation of estrogen, and induced the formation of 2-OHE.

CONCLUSION

I3C has anti-estrogenic activities which should prevent cancer in cervical cells.

Fish oil constituent docosahexa-enoic acid selectively inhibits growth of human papillomavirus immortalized keratinocytes

The omega-3-fatty acids inhibit proliferation of breast cancer cells whereas omega-6-fatty acids stimulate growth. In this study, we examined effects of these fatty acids on human pre-cancerous cells. Cervical keratinocytes, immortalized with the oncogenic human papillomavirus (HPV) type 16, were treated with linoleic acid, an omega-6-fatty acid, and the omega-3-fatty acids, eicosapentaenoic and docosahexaenoic acids. Using both cell counts and bromodeoxyuridine incorporation, docosahexaenoic acid inhibited growth of these cells to a greater extent than eicosapenta-enoic acid. Linoleic acid had no effect. The effect of docosahexaenoic acid was dose dependent and caused growth arrest. Docosahexaenoic acid inhibited growth of HPV16 immortalized foreskin keratinocytes and laryngeal keratinocytes grown from explants of benign tumors caused by papillomavirus, but had no effect on normal foreskin and laryngeal keratinocytes. Docosahexaenoic acid inhibited growth in the presence of estradiol, a growth stimulator for these cells. Indomethacin, a cyclooxygenase inhibitor like docosahexaenoic acid, had only minimal effect on growth. Alpha-tocopherol, a peroxidation inhibitor, abrogated effects of docosahexaenoic acid implying that inhibitory effects were via lipid peroxidation.

Estrogen metabolism and laryngeal papillomatosis: a pilot study on dietary prevention

Evidence exists that estrogen metabolism has a role in the pathogenesis of recurrent respiratory papillomatosis (RRP). This disease has a papillomavirus etiology and is characterized by recurrent benign tumors with a significant propensity to become malignant. We have measured the systemic transformation of estrogen using an enzyme-linked-immunoassay to measure estrogen metabolites in the urine of patients with RRP and compared these ratios to the severity of RRP, a measure of the average growth rate of papillomas. Our results show an inverse relationship between the ratio of C-2 to C-16 alpha-hydroxylated estrogens and the severity of RRP. In a pilot study, patients consumed cruciferous vegetables to induce C-2-hydroxylation. In this group of patients, an increase in the ratio correlated with an improvement in RRP. The ratio did not change in a subset of these patients, and their RRP did not improve. Regardless, the ratio correlated with severity of their RRP.

Estrogen metabolism and the malignant potential of human papillomavirus immortalized keratinocytes

Increased 16alpha-hydroxylation of estradiol has been shown to be associated with heightened cancer risk in estrogen responsive tissue. Certain types of human papillomavirus (HPV) are cofactors for cancer in the cervix, an estrogen sensitive tissue. We have demonstrated that estradiol and 16alpha-hydroxyestrone increased the number of cells positive for proliferating cell nuclear antigen in HPV immortalized keratinocytes, the in vitro correlate of the premalignant keratinocyte. These estrogens caused the abnormal proliferation and anchorage independent growth, which correlates with malignant conversion. Indole-3-carbinol, a phytochemical in cruciferous vegetables known to preferentially induce 2-hydroxylation with minimal effect on 16alpha-hydroxylation, markedly blocked the ability of estradiol to increase anchorage independent growth. The results indicate that 16alpha-hydroxyestrone increases the malignant phenotype of HPV immortalized keratinocytes. However, indole-3-carbinol will block this response.

C/EBPbeta is a negative regulator of human papillomavirus type 11 in keratinocytes

We have evaluated the impact of the CCAAT enhancer-binding protein (C/EBP) transcription factors on human papillomavirus type 11 (HPV11). C/EBPbeta is in nuclei of cultured foreskin keratinocytes and binds its consensus sequence in HPV11 DNA. We have used the novel approach of depleting the availability of C/EBPs in vivo using nuclease-resistant oligomers containing C/EBP DNA binding sites. In cultured foreskin keratinocytes containing replicating HPV11 DNA, levels of both HPV11 transcripts and HPV DNA increase after treatment with oligomers; containing the C/EBPbeta DNA binding motif. These results indicate that C/EBPbeta is a repressor for HPV11 in keratinocytes.

Estrogen metabolism and human papillomavirus-induced tumors of the larynx: chemo-prophylaxis with indole-3-carbinol

A relationship was established between estradiol 16 alpha-hydroxylation, papillomavirus and its malignant sequelae. In this study, we determined that 16 alpha-hydroxylation was substantial in normal larynx and further increased in laryngeal papillomas. Estradiol or 16 alpha-hydroxyestrone stimulated proliferation in both kinds of cells while 2-hydroxyestrone was antiproliferative. Indole-3-carbinol, which induces 2-hydroxylation, abrogated the proliferative effects of estradiol. In immunocompromised mice, papilloma cysts formed in HPV-11 infected laryngeal tissue implanted under the renal capsules in 100% of control mice but only in 25% of mice fed indole-3-carbinol.

Duplication of the upstream regulatory sequences increases the transformation potential of human papillomavirus type 11

Infections with certain types of papillomaviruses, e.g., human papillomavirus type 16 (HPV-16), often progress to cancer. Malignant lesions associated with the closely related HPV-11 are extremely rare. Additionally, HPV-11 DNA, unlike HPV-16, does not normally transform cells in vitro. We determined that HPV-11 DNA was able to transform baby rat kidney cells in a ras-dependent focus assay when the upstream regulatory region (URR) was present in two copies. Addition of a second HPV-11 URR or an HPV-16 URR was equally effective and was position and orientation independent. The transformation was enhanced by dexamethasone. On passage the HPV-11 genome was not retained at a detectable level. This analysis supports isolated observations in vivo that duplications of regulatory sequences in HPV-11 increase the transformation potential of this virus type.

Helicase, DNA-binding, and immunological properties of replication-defective simian virus 40 mutant T antigens

Simian virus 40 T antigen (TAg) exhibits nonspecific and origin-specific DNA binding (ori binding) and ATPase and helicase activities, all of which are related to its roles in viral DNA replication. We have characterized some of the properties of four replication-defective but transformation-competent mutant TAgs, C6-2, T22, C11, and C8A. C6-2 and T22 TAgs were each previously determined to lack ori-binding properties, while C11 TAg was reported to lack ATPase activity. The C8A TAg did not exhibit defects in either ori-binding or ATPase functions. We have analyzed additional aspects of these mutant TAgs pertaining to their helicase, DNA-binding, and immunological properties. With the exception of the C11 TAg, all the other TAgs exhibited helicase activity. The lack of helicase activity by C11 TAg was consistent with its previously shown inability to hydrolyze ATP or to replicate viral DNA. These results therefore show that ori-binding and helicase activities are separate functions of TAg. Wild-type and mutant TAgs bound with similar efficiency to either native or denatured calf thymus DNA-cellulose, indicating no marked differences in their nonspecific DNA-binding properties. We also tested the binding of wild-type and mutant TAgs to a monoclonal antibody, PAb 100, that was previously shown to recognize an extremely small class of TAg that may represent a unique conformational form of the protein. Interestingly, while less than 10% of the wild-type, C6-2, C11, and T22 mutant TAgs were recognized by PAb 100, more than 60% of the C8A mutant TAg was bound by this antibody. Therefore, although no defect in biochemical function was observed with the C8A TAg, its deficiency in viral DNA replication may be related to an unusual conformation, as detected by its dramatically increased recognition by PAb 100. These results show that the helicase activity of TAg is not required for its transformation function.

Enzymatic detection of the growth of Staphylococcus aureus in foods

A specific method has been developed for the extraction and measurement of staphylococcal nuclease in foods in which Staphylococcus aureus has grown. The method was used to compare staphylococcal growth with nuclease production in foods under varying conditions of temperature, aerobiosis, and competition from other microorganisms. It was concluded that the nuclease is produced under any conditions that permit growth of S. aureus, and little or no interference with the test was encountered either from mixed, natural populations or from a variety of pure, laboratory cultures. Nuclease and enterotoxin A production were shown to vary in synchrony for the 234 (Casman) strain of S. aureus, and the sensitivity of the enzymatic detection of nuclease was comparable to the sensitivity of serological detection of enterotoxin A. It was found that 15 min at 121 C was required to reduce the nuclease activity in slurries of contaminated ham below the level present in the unheated slurry. The extraordinary heat resistance of the nuclease permits its detection even in foods heated subsequent to the growth of S. aureus. The nuclease analysis requires about 3 hr to complete and requires no unusual equipment or reagents.