Margaret Hanausek

Synergistic Effects of Combined Phytochemicals and Skin Cancer Prevention in SENCAR Mice

The purpose of our study was to determine the inhibitory effect of combined phytochemicals on chemically induced murine skin tumorigenesis. Our hypothesis was that concurrent topical and dietary treatment with selected compounds would lead to more efficient prevention of skin cancer. We tested ellagic acid and calcium D-glucarate as components of diets, while resveratrol was applied topically; grape seed extract was applied topically or in the diet. The 4-week inflammatory-hyperplasia assay based on the 7,12-dimethylbenz[a]anthracene (DMBA)–induced skin carcinogenesis model in SENCAR mice was used. We have found that all the selected combinations caused a marked decrease of epidermal thickness compared with the DMBA-treated group and also with groups treated with a single compound and DMBA. All combinations of resveratrol with other compounds showed a synergistic effect on hyperplasia and Ha-ras mutations. Skin tissue of mice receiving the combinations showed decreased cell proliferation and Bcl2 expression; decreased p21, a regulator of cell cycle; and decreased marker of inflammation cyclooxygenase-2. All the selected combinations diminished the DMBA-induced mRNA expression of the CYP1B1 level, and also caused a marked decrease of proto-oncogenes c-jun and c-fos, components of transcription factor activator protein. In conclusion, all combinations showed either additive or synergistic effects and their joint actions allowed for decreasing the doses of the compounds. Especially, resveratrol combinations with ellagic acid, grape seed extract, and other phytochemicals are very potent inhibitors of skin tumorgenesis, based on the suppression of epidermal hyperplasia as well as on the modulation of intermediate biomarkers of cell proliferation, cell survival, inflammation, oncogene mutation, and apoptosis. Cancer Prev Res; 3(2); 170–8

Detoxifying Cancer Causing Agents to Prevent Cancer

Different vitamins and other micronutrients in vegetables, fruits, and other natural plant products may prevent cancer development (carcinogenesis) by interfering with detrimental actions of mutagens, carcinogens, and tumor promoters. The goal of current studies in cancer prevention is to determine the mechanisms of synergistic action of the natural source compounds known to inhibit one or more stages of carcinogenesis, that is, initiation and promotion/progression. Many natural cancer preventive agents are effective inhibitors of tumor initiation, promotion, and/or progression. The mechanism of action is related to their abilities to prevent critical carcinogen metabolism and to increase detoxification of carcinogens and tumor promoters. The authors review here the potential role of the detoxification system and, in particular, the roles of d-glucaric acid and the enzyme β-glucuronidase in early detection and prevention of cancer. There is now growing evidence for the possible control of different stages of the cancer induction by inhibiting β-glucuronidase with d-glucaric acid derivatives, especially with its salts (d-glucarates). d-Glucaric acid has been found in many vegetables and fruits. Therefore, the consumption of fruits and vegetables naturally rich in d-glucaric acid or self-medication with d-glucaric acid derivatives such as calcium d-glucarate offers a promising cancer prevention approach.

Differential effects of several phytochemicals and their derivatives on murine keratinocytes in vitro and in vivo: implications for skin cancer prevention

The purpose of our study was to investigate in vitro the potential cancer preventive properties of several phytochemicals, i.e. grape seed extract (GSE), resveratrol (RES), ursolic acid (URA), ellagic acid (ELA), lycopene and N-acetyl-L-cysteine (NAC) to define the mechanisms by which these compounds may inhibit murine skin carcinogenesis. We measured quenching of peroxyl, superoxide and hydroxyl radicals by these phytochemicals. We also used adenosine triphosphate (ATP) bioluminescence, Caspase-Glo 3/7 and P450-Glo (CYP1A1 and CYP1B1) assays to study antiproliferative, proapoptotic and CYP-inhibiting effects of the phytochemicals. We next determined their effects on a 4 week inflammatory hyperplasia assay using 7,12-dimethylbenz[a]anthracene-induced murine skin carcinogenesis model to further understand their mechanism of action. Three murine keratinocyte cell lines, i.e. non-tumorigenic (3PC), papilloma-derived (MT1/2) and squamous cell carcinoma-derived (Ca3/7) cell lines, were used in in vitro assays. We have found that GSE, ELA and RES are potent scavengers of peroxyl and superoxide radicals. Statistically significant effects on activities of caspase-3 and -7 were observed only after GSE and URA treatments. All tested compounds protected cells from hydrogen peroxide-induced DNA damage. Using a short-term complete carcinogenesis assay, we have found that all selected compounds caused marked decreases of epidermal thickness and (except RES) reduced percentages of mice with mutation in codon 61 of Ha-ras oncogene. In conclusion, differential effects of tested phytochemicals on events and processes critical for the growth inhibition of keratinocytes in vitro and in vivo indicate that combinations of tested compounds may, in the future, better counteract both tumor initiation and tumor promotion/progression.

Avicin D: A Protein Reactive Plant Isoprenoid Dephosphorylates Stat 3 by Regulating Both Kinase and Phosphatase Activities

Avicins, a class of electrophilic triterpenoids with pro-apoptotic, anti-inflammatory and antioxidant properties, have been shown to induce redox-dependant post-translational modification of cysteine residues to regulate protein function. Based on (a) the cross-talk that occurs between redox and phosphorylation processes, and (b) the role of Stat3 in the process of apoptosis and carcinogenesis, we chose to study the effects of avicins on the processes of phosphorylation/dephosphorylation in Stat3. Avicins dephosphorylate Stat3 in a variety of human tumor cell lines, leading to a decrease in the transcriptional activity of Stat3. The expression of Stat3-regulated proteins such as c-myc, cyclin D1, Bcl2, survivin and VEGF were reduced in response to avicin treatment. Underlying avicin-induced dephosphorylation of Stat3 was dephosphorylation of JAKs, as well as activation of protein phosphatase-1. Downregulation of both Stat3 activity and expression of Stat 3-controlled pro-survival proteins, contributes to the induction of apoptosis in avicin treated tumor cells. Based on the role of Stat3 in inflammation and wounding, and the in vivo inhibition of VEGF by avicins in a mouse skin carcinogenesis model, it is likely that avicin-induced inhibition of Stat3 activity results in the suppression of the pro-inflammatory and pro-oxidant stromal environment of tumors. Activation of PP-1, which also acts as a cellular economizer, combined with the redox regulation by avicins, can aid in redirecting metabolism from growth promoting anabolic to energy sparing pathways.

The Role of Skin Painting in Predicting Lung Cancer

The mouse skin cancer model provides an important system for studying mechanisms involved in the various stages of carcinogenesis and for bioassaying tobacco smoke constituents and additives for carcinogenic/cocarcinogenic and tumor-promoting properties as well as for identifying compounds that may inhibit tumor formation and malignant conversion. In addition, it is an excellent model for studying the formation of precancerous lesions as well as squamous cell carcinomas. It relates very well to other squamous cell carcinoma models and contributes to better understanding of the human epithelial cancers including lung cancer. The SENCAR mouse is an established model system demonstrated to be more sensitive than the B6C3F1 or Swiss CD-1 strains in the initiation/promotion skin-painting test method. Although the relationship between mouse skin tumors and any manifestation of the toxicity of tobacco smoke and other complex environmental mixtures in humans is unknown, the skin-painting model is the only assay that provides a practical method of obtaining a tumorigenic end point with cigarette smoke condensates and other complex mixtures. This assay provides a rapid response with relative ease of quantification of various parameters of tumorigenic response including tumor incidence, latency, multiplicity, and malignancy.

Effects of combined phytochemicals on skin tumorigenesis in SENCAR mice.

The purpose of our study was to determine the effect of the combined action of phytochemicals on the early stages of skin tumorigenesis, i.e. initiation and promotion. We tested calcium D-glucarate (CG) given in the diet, while resveratrol (RES) and ursolic acid (UA) were applied topically. The 7,12-dimethylbenz[a]anthracene (DMBA)-initiated, 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted multistage skin carcinogenesis model in SENCAR mice was used. Mice received one topical dose of DMBA, then after one month, two weekly doses of TPA for 14 weeks until sacrifice. RES or UA were applied 20 min prior to DMBA or TPA treatment and 2% dietary CG was given from 2 weeks prior to 2 weeks after the DMBA dose or continually beginning 2 weeks prior to the first dose of TPA. UA applied alone and in combination with CG during the promotion stage was the only inhibitor of tumor multiplicity and tumor incidence. A number of combinations reduced epidermal proliferation, but only UA and the combination UA+CG applied during promotion significantly reduced epidermal hyperplasia. DMBA/TPA application resulted in significant increases in c-jun and p50, which were reversed by a number of different treatments. DMBA/TPA treatment also strongly increased mRNA levels of inflammation markers COX-2 and IL-6. All anti-promotion treatments caused a marked decrease in COX-2 and IL-6 expression compared to the DMBA/TPA control. These results show that UA is a potent inhibitor of skin tumor promotion and inflammatory signaling and it may be useful in the prevention of skin cancer and other epithelial cancers in humans.

Inhibition of Murine Skin Carcinogenesis by Freeze-Dried Grape Powder and Other Grape-Derived Major Antioxidants

Overexposure of the skin to carcinogenic insults causes a variety of adverse effects, among them the development of skin carcinomas. Since there is a need to develop efficient chemopreventive agents based on nutrition, our goal was to determine antioxidant and anti-carcinogenic properties of grapes by evaluating grape powder developed by the California Table Grape Commission. In order to elucidate the mechanism(s) of action of grape powder, three of the major antioxidant components found in grapes—resveratrol, catechin, quercetin, and grape seed extract, containing a proanthocyanidin B-2-gallate—were evaluated for their abilities to inhibit oxidative stress and to protect the immune system. Tested antioxidants given topically and/or systemically strongly inhibited 7,12-dimethylbenz[a]anthracene (DMBA)-induced epidermal hyperplasia, proliferation, and inflammation. The hydroxylation of 2′-deoxyguanosine was markedly inhibited by topical and dietary administration of test variables, i.e., by approximately 40–70%. Simultaneous dietary and topical treatment with antioxidants reduced these biomarkers, showing strong additive and in some combinations synergistic effects. DMBA-mediated Ha-ras mutations in codon 61 were reduced by up to 50% with topical applications, but much higher inhibition was observed in mice treated with different combinations. The results of the present study clearly show impressive effects of combined topical and dietary treatments with above grape-derived antioxidants.

Calorimetric study as a potential test for choosing treatment of B-cell chronic lymphocytic leukemia

Differential scanning calorimetry (DSC) and complementary techniques were utilized to evaluate the sensitivity of B-cell chronic lymphocytic leukemia (B-CLL) cell samples in vitro exposed to cladribine or fludarabine in combination with mafosfamide. Mafosfamide, the active in vitro form of cyclophosphamide with both purine analogs produced the cytotoxic effect on mononuclear cell probes, however, to a different degree. Our results indicated that higher sensitivity of examined leukemic cell samples to the used drug combinations was usually accompanied by a marked decrease or even a complete loss of thermal transition at 95+/-3 degrees C in DSC scans of nuclear preparations as well as by more significant reduction of cell viability, higher extent of DNA damage estimated by the comet assay and by dropping/disappearance of anti-apoptotic protein Mcl-1 in comparison with untreated cells. We have also observed that the reduction of transition at 95+/-3 degrees C in thermal scans of nuclear preparations isolated from blood of B-CLL randomized patients who showed response to cladribine or fludarabine combined with cyclophosphamide, i.e., CC and FC, respectively, corresponded with the decrease or disappearance of anti-apoptotic proteins Bcl-2 and/or Mcl 1. In conclusion, these in vitro and in vivo studies revealed that quick DSC technique, usually supplemented by other methods, is a potent tool to distinguish efficacy of B-CLL treatment and could be helpful in choosing the most effective manner of treatment for this type of leukemia.

Changes in leukemic cell nuclei revealed by differential scanning calorimetry

Using differential scanning calorimetry we analyzed the thermal profiles of nuclei from normal and B-cell chronic lymphocytic leukemia mononuclear cells. Intact nuclear fraction of normal mononuclear cells is characterized by four thermal transitions, i.e., at 60, 70, 83 and 103°C. Leukemic nuclear samples revealed the transitions at 67 and 83°C, however, in more aggressive stage of the disease additional thermal peaks at 76 and 93°C were observed. Our very preliminary results revealed that mononuclear cell nuclear fraction from blood of patients responding to the used therapy, i.e., cladribine alone or its combination with mitoxantrone and cyclophosphamide indicates decrease (or even loss) of transition at 93°C concomitant with increase of transition at 76°C. A complementary study showed that in mononuclear cells of patients who appeared to be sensitive to chemotherapy the decrease of antiapoptotic Bcl-2 protein expression and signs of apoptotic morphology were observed.

Desipramine inhibits the growth of a mouse skin squamous cell carcinoma cell line and affects glucocorticoid receptor-mediated transcription

The purpose of this study was to examine the effect of tricyclic antidepressant desipramine (DMI) on the growth inhibition and translocation of the glucocorticoid receptor (GR) from the cytoplasm to the nucleus in cancerous and noncancerous cell lines and the effect of DMI on GR‐mediated transcription. Nontumorigenic, immortalized keratinocytes cell line (3PC), papilloma (MT1/2), and squamous cell carcinoma (Ca3/7) cell lines were initially used to study the cell growth inhibition by DMI. Although, the growth of all three cell lines was suppressed by DMI, it was more effective in Ca3/7 cells. Therefore, we next examined the effect of DMI on Ca3/7 cells, resistant to growth inhibition by the synthetic glucocorticoid fluocinolone acetonide (FA). DMI inhibited cell proliferation in a time‐dependent manner. The translocation of GR was induced by FA alone, DMI alone, and combination of both agents. FA induced GR‐mediated transcription in Ca3/7 cells transfected with a luciferase reporter gene under the control of glucocorticoid response element (GRE), but DMI alone did not affect GR‐mediated transcription. However, DMI inhibited FA‐induced, GR‐mediated transcription when both agents were given together. Pretreatment with DMI followed by combination of DMI and FA decreased GR‐mediated transcription more than pretreatment with FA. The expression of metallothionein‐1 (Mt‐1) gene, which is regulated by GR, was induced significantly by the combination of DMI and FA, and enhanced significantly by pretreatment with FA but not DMI. DMI is suggested to inhibit the growth of Ca3/7 cells and to affect GR‐mediated transcription. Mol. Carcinog.