Arup K. Indra - US grants

[unreadable] DESCRIPTION (provided by applicant): The development of the skin from intrauterine to extrauterine life is an orchestrated interplay of epidermal proliferation, terminal differentiation, and barrier formation. Failure to construct an epidermal permeability barrier (EPB), which is a life-threatening problem in the majority of premature infants, results in increased transepidermal water loss with concomitant dehydration and electrolyte imbalance, as well as fragile skin. Barrier defects are also believed to contribute to several hereditary and acquired inflammatory skin disorders, such as psoriasis and atopic dermatitis (AD). Thus, understanding the pathways that are controlled by different regulatory proteins (e.g., transcription factors) in skin is the key for the development of effective treatments for the various skin diseases described above, as well as epithelial cell skin cancers, including head and neck squamous cell carcinoma (HNSCC). Chicken ovalbumin upstream promoter transcription factor (COUP-TF)-interacting protein 2 (CTIP2, also known as Bcl11b) is a transcriptional regulatory protein that is highly expressed in skin during mouse development, as well as in proliferating cells of the adult mouse. We have recently discovered that germline deletion of CTIP2 in mice results in a severe skin phenotype characterized by compromised EPB formation, and dramatically reduced epidermal thickness. We have also observed striking upregulation of CTIP2 in several human HNSCC biopsies, in which the level of CTIP2 expression was inversely correlated with the degree of differentiation of the tumor, i.e., poorly differentiated tumors were found to express very high levels of CTIP2 while highly differentiated tumors expressed very little CTIP2. However, the cellular and molecular mechanism underlying the activity of CTIP2 in skin during epidermal homeostasis and barrier formation is not known. Similarly, we do not understand the role of CTIP2 in proliferative events during skin development or in proliferative diseases of adults, such as HNSCC. Lack of this knowledge is a critical problem in our understanding of the biological roles of the CTIP2 in human health and disease. The long-term goal of this laboratory is to elucidate the molecular and cellular mechanisms that underlie the actions of CTIP2 in fetal, neonatal, and adult skin, and in proliferative diseases of the skin, towards the goal of extrapolating to the human situation. Based on the above observations and from the preliminary data, we propose the following three Specific Aims: (1) to elucidate the cellular and molecular mechanism(s) underlying the role of CTIP2 in EPB formation, (2) to elucidate the cellular and molecular mechanism(s) of CTIP2 action in epidermal proliferation/differentiation, and (3) to determine the role of CTIP2 in pathogenesis of head and neck squamous cell carcinoma. The proposed research is innovative because it will, for the first time, reveal the cellular and molecular mechanisms by which CTIP2 regulates skin organogenesis, EPB formation, and tissue homeostasis. We believe that this research will have significant, positive effects on human health because these outcomes will provide an enhanced understanding of regulatory influences on epidermal keratinocyte proliferation, differentiation and EPB formation, which may lead to development of more efficacious treatment paradigms for the human disorders, such as atopic dermatitis, and possibly HNSCC. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Malignant melanoma is one of the fastest increasing cancers in the United States and no curative treatment is yet available. Solar ultraviolet (UV) radiation, especially childhood sun exposure is an important etiological risk factor of melanoma. Retinoid X Receptor a (RXRa), a member of the nuclear receptor (NR) superfamily, is a central coordinator for transducing diverse cellular signals. In the context of studying the role of RXRa in skin, we have discovered an unexpected and novel role for this NR in melanomagenesis: RXRa[ep-/-] mice, specifically lacking RXRa in epidermal keratinocytes, develop melanocytic growths (MGs) resembling melanoma at high frequency when subjected to a two-step chemical carcinogenesis protocol (DMBA+TPA). Our results suggest that RXRa may regulate a keratinocyte ? melanocyte signaling pathway(s) implicated in the control of melanocytic proliferation. Thus, we have generated a new mouse model for melanomagenesis. However, the molecular mechanisms that underlie these activities of RXR are not known. Given the importance of keratinocytes in regulating melanocyte mitogenesis, understanding how this regulation becomes aberrant in melanoma is significant, since it can possibly lead to the development of effective therapeutic strategies to counteract melanoma formation and progression. Our long-term goal is to identify the mechanisms of signal transduction between keratinocytes and melanocytes that contribute to the development of melanoma. Based on the above observations and from the preliminary data, we propose the following two specific aims. First, we propose to elucidate the cellular and molecular mechanisms by which keratinocytes control melanocyte mitogenesis and transformation leading to a malignant phenotype. Our working hypothesis is that RXRa, directly or indirectly, represses keratinocytic expression of endothelin 1 (ET-1), SCF, POMC and FGF2 which may serve to regulate melanocytic mitogenesis in a paracrine manner. Second, we propose to identify intracellular targets (melanocytic factors) that control melanocyte homeostasis and UV-induced melanomagenesis. Our working hypothesis is that melanocytic factors, such as cyclin dependent kinase-4 (Cdk4), may modulate the responsiveness of these cells to the mitogenic effects of keratinocyte-derived paracrine factors. We believe that our efforts in the context of the work described herein will lead to a detailed understanding of the mechanism(s) by which melanocyte mitogenesis and melanomagenesis are regulated by keratinocytic RXRa, and perhaps other paracrine factors. The proposed project is potentially innovative as our laboratory generated the RXRa [ep-/-] mouse that has been used for these studies, and was the first to characterize the in vivo role of RXRa in skin during epidermal homeostasis. This contribution is significant and the results are expected to have a positive impact on human health, because the outcome of the work will provide the molecular cornerstone for the development of future pharmacological strategies designed to treat, and ultimately cure malignant melanoma. PUBLIC HEALTH RELEVANCE: Melanoma is generally recognized as an aggressive skin cancer that can metastasize early in the course of the disease and is highly resistant to most current therapeutic interventions. Understanding the genetic and environmental factors driving melanoma formation is essential for the development of new therapies to treat this disease. The present study involves the use of a novel melanoma mouse model to study the molecular mechanism underlying the role of skin keratinocytes to control melanocyte mitogenesis and melanomagenesis.