I retired in the autumn of 2014 and closed my research laboratory after a 35 year independent research career, the final 21 years of which were in the Dermatology Department at Brigham and Women’s Hospital.  I am currently a Visiting Scholar in the Department of Molecular, Cellular, and Developmental Biology at U.C.L.A. in Los Angeles.

The long-term research interest of my lab was to understand the mechanisms that regulate growth, differentiation, and malignant transformation of epithelial cells.  Our major focus was the keratinocyte—the cell type that forms stratified squamous epithelial tissues, which include the epidermis and the oral, corneal, conjunctival, esophageal, and exocervical epithelia. We studied several other epithelial cell types, as well:  the mesothelial cell, which covers all surfaces within the peritoneal, pleural, and pericardial cavities and is the cell type from which the asbestos-induced cancer mesothelioma arises, and the myoepithelial cell, which surrounds the secretory units of the sweat, salivary, and mammary glands and provides structural integrity and contractility.  We also studied prostate epithelial cells, tracheobronchial epithelial cells, bladder urothelial cells, and an epithelial cell type derived in culture from human embryonic stem cells.

Our research used human cell culture systems and a somatic cell genetics approach to understand how growth, differentiation, and motility are regulated in normal cells and identify alterations of these that result in cancer.  The experimental tools we used included microscopy, genetic engineering using retroviral and lentiviral vectors, immunostaining, Western blotting, growth and motility assays, organotypic culture, flow cytometry, and Q RT-PCR. (See the Publications list on this website for our papers, available as pdfs).

The most recent research conducted by the Rheinwald lab was on two subjects:
The first was to understand the signaling proteins and pathways involved in a coupled hypermotility and growth-arrest response that we first discovered as a cell aging and senescence mechanism in cultured epithelial cells.  We found that keratinocyte senescence arrest in culture typically occurs from induction of the cell cycle inhibitor p16INK4A, before telomere shortening would induce the better known form of senescence by a different mechanism.  These studies also revealed that senescing keratinocytes often begin to express high levels of the γ2 subunit of the basement membrane protein Laminin-332 (Lamγ2) and display a burst of sustained directional hypermotility as they become senescent. Interestingly, we found that, in vivo, p16INK4A  is not expressed in normal epithelial tissues, even in aged adults, and that expression of Lamγ2 is normally very low.  Our studies disclosed that coordinate induction of p16INK4A and Lamγ2 occurs in two settings in vivo:  during normal wound repair and in premalignant dysplastic lesions that precede invasive squamous cell carcinoma.  The last papers we published on this subject described our discovery that hyperactive EGFR/MAPK signaling results in increased Lamγ2 and c-myc expression by a post-transcriptional mechanism involving ERK, RSK, eIF4B and translational initiation. We found that increases in the phosphorylated form of ribosomal protein S6, an RSK target, are detectable immunohistochemically in regions of potentially premalignant lesions of oral mucosal and vulvar epithelium.

The second was aimed at understanding the role of the transcriptional regulator p63 in regulating the set of genes expressed in common by a variety of epithelial lineages. p63 is required for the development of a large family of epithelial cells types including keratinocytes, urothelial cells, and tracheobronchial, prostate, and mammary epithelial cells.  Most of these epithelial cell types stably maintain p63 expression in culture, but we found that one cell type loses expression in certain conditions of culture while retaining viability and proliferative potential.  In doing so, it changes expression of hundreds of genes.  We are investigating this cell type, as well as fibroblasts and other cell types that are naturally p63 non-expressing, after we have engineered them to express p63.  Data analysis for this project is still ongoing in preparation for writing a paper on this research.

© 2010 James Rheinwald