Asha Acharya

Classification of human B-ZIP proteins based on dimerization properties.

B-ZIP transcription factors (98) are exclusively eukaryotic proteins that bind to sequence-specific double-stranded DNA as homodimers or heterodimers to either activate or repress gene transcription (34). We have examined both of the recently published DNA sequences of the human genome (51, 95) and identified 56 genes that contain the B-ZIP motif. Three sequences were identical, giving a total of 53 unique B-ZIP domains with the potential to form 2,809 dimers. This creates the possibility for a tremendous range of transcriptional control (23, 50, 52). While significant effort has been directed at identifying dimerization partners of B-ZIP proteins, the full complement of dimerization partners remains to be elucidated. This review highlights two topics: (i) the known structural rules that regulate leucine zipper dimerization specificity and (ii) experimental data addressing mammalian B-ZIP dimerization partners. We have annotated the leucine zippers of all human B-ZIP domains, highlighting amino acids in the a, d, e, and g positions that appear critical for leucine zipper dimerization specificity. These data were used to group B-ZIP proteins into 12 families with similar dimerization properties: (i) those that strongly favor homodimerization within the family (PAR, CREB, Oasis, and ATF6), (ii) those that have the ability to both homodimerize and heterodimerize with similar affinities (C/EBP, ATF4, ATF2, JUN, and the small MAFs), and (iii) those that favor heterodimerization with other families (FOS, CNC, and large MAFs).

Activator Protein-1 Activity Regulates Epithelial Tumor Cell Identity

To examine the consequences of inhibiting activator protein-1 (AP-1) transcription factors in skin, transgenic mice were generated, which use the tetracycline system to conditionally express A-FOS, a dominant negative that inhibits AP-1 DNA binding. Older mice develop mild alopecia and hyperplasia of sebaceous glands, particularly around the eyes. When A-FOS was expressed during chemical-induced skin carcinogenesis, mice do not develop characteristic benign and malignant squamous lesions but instead develop benign sebaceous adenomas containing a signature mutation in the H-ras proto-oncogene. Inhibiting AP-1 activity after tumor formation caused squamous tumors to transdifferentiate into sebaceous tumors. Furthermore, reactivating AP-1 in sebaceous tumors results in a reciprocal transdifferentiation into squamous tumors. In both cases of transdifferentiation, individual cells express molecular markers for both cell types, indicating individual tumor cells have the capacity to express multiple lineages. Molecular characterization of cultured keratinocytes and tumor material indicates that AP-1 regulates the balance between the wnt/beta-catenin and hedgehog signaling pathways that determine squamous and sebaceous lineages, respectively. Chromatin immunoprecipitation analysis indicates that c-Jun binds several wnt promoters, which are misregulated by A-FOS expression, suggesting that members of the wnt pathway can be a primary targets of AP-1 transcriptional regulation. Thus, AP-1 activity regulates tumor cell lineage and is essential to maintain the squamous tumor cell identity.

Chemopreventive properties of indole-3-carbinol, diindolylmethane and other constituents of cardamom against carcinogenesis.

Oxidative stress results from an imbalance in the production of reactive oxygen species (ROS) and cells own antioxidant defenses that in part lead to numerous carcinogenesis. Several phytochemicals, derived from vegetables, fruits, herbs and spices, have demonstrated excellent chemopreventive properties against carcinogenesis by regulating the redox status of the cells during oxidative stress. I3C (indole-3-carbinol) and DIM (diindolylmethane) are the phytochemicals that are found in all types of cruciferous vegetables and demonstrated exceptional anti-cancer effects against hormone responsive cancers like breast, prostate and ovarian cancers. Novel analogs of I3C were designed to enhance the overall efficacy, particularly with respect to the therapeutic activity and oral bioavailability and that results in several patent applications on symptoms associated with endometriosis, vaginal neoplasia, cervical dysplasia and mastalgia. Likewise, DIM and its derivatives are patented for treatment and prevention of leiomyomas, HPV infection, respiratory syncytial virus, angiogenesis, atherosclerosis and anti-proliferative actions. On the other hand, phytochemicals in cardamom have not been explored in great details but limonene and cineole demonstrate promising effects against carcinogenesis. Thus studies with selected phytochemicals of cardamom and bioavailability research might lead to many patent applications. This review is focused on the patents generated on the effects of I3C, DIM and selected phytochemicals of cardamom on carcinogenesis.

Abstract 2880: Spices suppress oxidative stress during DMBA induced skin carcinogenesis in mice, mimicking human non-melanoma skin cancer

Background: Cancer chemoprevention is the use of natural, synthetic or biologic substances to reverse, suppress, or prevent the development of cancer. Spices like cinnamon, cardamom and cumin are the naturally occurring phytoproducts that display an active cancer preventive strategy to inhibit, delay or reverse the human carcinogenesis. Aims and Objectives: Our aim of this study is to decipher the chemopreventive effect of aqueous infusion of the spices as a diet on DMBA induced skin carcinogenesis, which mimics UV radiation mediated non melanoma skin cancer that has high mortality rate if not diagnosed early. Research Design and Methodology: Female Swiss Albino Mice have been divided into 5 groups in each case. Normal control (NC) and DMBA treated control (CC) mice received acetone and DMBA/croton oil on it9s dorsally shaven skin for eight weeks, respectively. Aqueous suspensions of the spices were orally administered to three groups of mice either before or after or both before and after DMBA applications on the shaved skin during the entire study period. Treated skins were excised after harvesting the mice and H & E staining, immunohistochemistry assays for lipid peroxides, antioxidation enzymes activities, immunoblotting, cell proliferation and apoptosis were performed. Results: All the spices demonstrate inhibition of the skin papillomagenesis. The best chemopreventive actions of these spices were observed when the spice treatments were performed both before and after the induction of skin carcinogenesis by DMBA. An up-regulation of the phase II detoxification enzymes and induction of non-protein thiol antioxidants were observed in mice treated with the spices. Additionally, cumin and cardamom demonstrate downregulation of COX-2 expression, inhibit cell proliferation and block p53-induced apoptosis. Cardamom stimulates NRF2 and inhibits NF-κB transcription factors to demonstrate its beneficial action against skin carcinogenesis. Conclusion: Spices inhibit DMBA induced skin carcinoma in mice when treated early and it is believed to be due, at least in part, to the induction of cellular defense systems. We are in a process of identifying unique chemical components of these spices to maximize the benefits. References: 1. Das, I., and Saha, T.; Nutrition. (2009); 25(4):459-471. 2. Das, I., Das, S. and Saha, T.; Acta Histochem. (2009); (In Press) 3. Das, I., Rana, T., Sengupta, A., and Saha, T.; J. Biol. Chem. 2009; (In Revision) 4. Acharya, A, Das, I., Chandhok, D., and Saha, T.; Oxidative Stress and Cellular Longevity; 2009; (In Press) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2880.