Timothy M. Johnson

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A fundamental question in cancer biology is whether cells with tumorigenic potential are common or rare within human cancers. Studies on diverse cancers, including melanoma, have indicated that only rare human cancer cells (0.1-0.0001%) form tumours when transplanted into non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice. However, the(More)
We investigated whether melanoma is hierarchically organized into phenotypically distinct subpopulations of tumorigenic and nontumorigenic cells or whether most melanoma cells retain tumorigenic capacity, irrespective of their phenotype. We found 28% of single melanoma cells obtained directly from patients formed tumors in NOD/SCID IL2Rγ(null) mice. All(More)
Dysfunction of the endoplasmic reticulum (ER) has been reported in a variety of human pathologies, including cancer. However, the contribution of the ER to the early stages of normal cell transformation is largely unknown. Using primary human melanocytes and biopsies of human naevi (moles), we show that the extent of ER stress induced by cellular oncogenes(More)
PURPOSE To assess the accuracy and completeness of information regarding melanoma on the Internet, retrieved by use of search engines. METHODS The first 30 uniform/universal resource locators (URLs) from each of eight search engines using the search term "melanoma" were retrieved for evaluation of accuracy and completeness using a 35-point checklist(More)
Merkel cell carcinoma (MCC) is a relatively rare cutaneous malignancy that occurs predominantly in the older white population. The incidence of MCC appears to have tripled during the past 20 years; an increase that is likely to continue because of the growing number of older Americans. The pathogenesis of MCC remains largely unknown. However, ultraviolet(More)
BACKGROUND The management of Merkel cell carcinoma (MCC) has been complicated by a lack of detailed prognostic data and by the presence of conflicting staging systems. OBJECTIVE We sought to determine the prognostic significance of tumor size, clinical versus pathologic nodal evaluation, and extent of disease at presentation and thereby derive the first(More)
MicroRNAs (miRs) play a key role in cancer etiology by coordinately repressing numerous target genes involved in cell proliferation, migration and invasion. The genomic region in chromosome 9p21 that encompasses miR-31 is frequently deleted in solid cancers including melanoma; however the expression and functional role of miR-31 has not been previously(More)
PURPOSE To determine the survival rates and independent predictors of survival using a contemporary international cohort of patients with stage III melanoma. PATIENTS AND METHODS Complete clinicopathologic and follow-up data were available for 2,313 patients with stage III disease in an updated and expanded American Joint Committee on Cancer (AJCC)(More)
BACKGROUND Dermatofibrosarcoma protuberans (DFSP) is a rare sarcoma with a propensity for local recurrence. Treatments with wide excision, Mohs surgery, and other approaches have been reported with widely variable local control rates. The objective of this study was to review the experience with a multidisciplinary approach employing wide excision and Mohs(More)
BACKGROUND Tissue expansion is a concept based on the skin's natural ability to stretch in response to an underlying force. OBJECTIVE The purpose of this article is to review the histological and physiological changes that occur within the soft tissue and underlying structures during tissue expansion. METHODS An extensive search of the literature(More)