Abstract 1122: UVB-induced PTEN down-regulation and its association with skin carcinogenesis

Non-melanoma skin cancer including squamous cell carcinoma (SCC) is the most common cancer in the United States and ultraviolet (UV) radiation in sunlight is a major environmental trigger for skin carcinogenesis. PTEN (phosphatase and tensin homolog deleted on chromosome 10) is a proven critical tumor suppressor. We found that UVB down-regulates PTEN in primary human keratinocytes, human HaCaT keratinocytes and mouse skin, and the ERK/AKT/PTEN axis may form a positive feedback loop following UVB irradiation. We also examined PTEN levels in different types of skin cancer that are associated with chronic sun exposure, including actinic keratoses (AK, premalignant lesion), keratocanthoma (KA), squamous cell carcinoma (SCC) in situ (SCC is), SCC invasive (SCC iv). As compared with normal skin, PTEN expression is significantly down-regulated in human skin cancer with these different diagnoses. In addition, PTEN down-regulation is significantly associated with solar UV damage and age of patients. Our findings indicate that UVB radiation suppresses PTEN expression in human skin cancer and this down-regulation may play critical roles in the development and progression of human skin cancer.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

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 1122.

UVB-induced ERK/AKT-dependent PTEN suppression promotes survival of epidermal keratinocytes

Ultraviolet (UV) radiation in sunlight is the major environmental cause of skin cancer. PTEN (phosphatase and tensin homolog deleted on chromosome 10) is a proven critical tumor suppressor. We report here that UVB down-regulates PTEN in primary human keratinocytes, human HaCaT keratinocytes, and mouse skin. As compared to normal skin, the PTEN levels are reduced in human actinic keratosis, a precancerous skin lesion caused by solar UV. PTEN down-regulation is mediated by two mechanisms: (1) PTEN is cleaved by active caspase in apoptotic cells in which AKT activation is reduced; and (2) PTEN transcription is suppressed in surviving cells, and this suppression is independent of caspase activation and occurs in parallel with increased ERK and AKT activation. We report here that the combination of ERK and AKT activation is crucial for PTEN suppression in surviving cells following UVB irradiation. PTEN remains suppressed in these cells. AKT activation is higher in UVB-irradiated surviving cells as compared to UVB protected control cells. ERK and AKT pathways are involved in sustaining PTEN suppression in UVB-exposed cells. Increasing PTEN expression enhances apoptosis of keratinocytes in response to UVB radiation. Our findings indicate that (1) UVB radiation suppresses PTEN expression in keratinocytes, and (2) the ERK/AKT/PTEN axis may form a positive feedback loop following UVB irradiation. Identification of PTEN as a critical molecular target of UVB will add to our understanding of the pathogenesis of skin cancer.

Update on immunohistochemical methods relevant to dermatopathology

CONTEXT

Dermatopathology covers a large variety of entities, some having very similar histologic appearances. Immunohistochemistry is an incredibly helpful tool that is useful in diagnosis as well as prognosis of selected skin tumors.

OBJECTIVE

To provide a comprehensive review of recent trends and immunohistochemical stains used by dermatopathologists. Emphasis is placed on new stains as well as novel uses of existing stains.

DATA SOURCES

All data were gathered from published journal articles available through the National Center for Biotechnology Information PubMed database.

CONCLUSIONS

New immunohistochemical targets are continually being found, contributing to more accurate diagnosis and classification of skin tumors. The presence of specific markers can be used to determine the aggressiveness of malignancies and design treatment strategies. In addition, application of existing stains can help determine intravascular spread of malignancy in primary cutaneous lesions. And use of rapid immunohistochemical staining techniques on frozen sections can assist in more complete excision of tumor margins. Immunohistochemistry is a highly versatile and growing tool of dermatopathologists.

Altered expression of the iron transporter Nramp1 (Slc11a1) during fetal development of the retinal pigment epithelium in microphthalmia-associated transcription factor Mitf(mi) and Mitf(vitiligo) mouse mutants

Microphthalmia-associated transcription factor (Mitf) is expressed in neural crest cell-derived melanocytes, and in the retinal pigment epithelium (RPE) during ocular development. Mutations in Mitf are associated with auditory/visual/pigmentary syndromes in humans. Mitf(mi/mi) mouse mutants lack pigmentation, and are microphthalmic, while Mitf(vit/vit) mouse mutants display abnormal RPE pigmentation, and progressive retinal degeneration. Microarray analysis was used to identify novel downstream gene targets/pathways in the RPE that are altered by mutations in the transcription factor Mitf. Using the Affymetrix platform, gene expression profiles were generated using the eyes of E13.5 mouse fetuses that were wildtype, heterozygous, or homozygous for the Mitf(mi) mutation. In a separate experiment, eyes from E13.5 mouse fetuses homozygous for the Mitf(vit) mutation were compared to eyes from the C57BL/6 control background strain. Statistical analyses were performed using robust multiarray average, mixed-effects ANOVA and random-variance t-tests. Altered expression of genes involved in pigment formation, melanosome biogenesis/transport, and redox homeostasis were observed. Twelve genes were commonly mis-regulated in the eyes of both Mitf mutants: 10 of these genes were downregulated in both mutants relative to controls, while 2 of the genes (Nramp1 (Slc11a1) and epoxide hydrolase) were downregulated in Mitf(mi/mi) mutants, and conversely, upregulated in Mitf(vit/vit) mutants. Quantitative RT-PCR and immunohistochemistry were used to confirm altered gene/protein expression. RPE expression of the Fe(+2) iron transporter Nramp1 (Slc11a1) has not previously been reported. Fe(+2) is an important co-factor utilized by the iron-dependent isomerohydrolase RPE65 in the retinoid visual cycle. However, excess accumulation of Fe(+2) in the RPE has recently been associated with oxidative damage and age-related macular degeneration. Abnormal pigmentation and increased activity of Slc11a1 in the RPE of Mitf(vit) mice may contribute to the pathology and progressive retinal degeneration observed in these mutants.

Antibody-conjugated soybean oil-filled calcium phosphate nanoshells for targetted delivery of hydrophobic molecules

Hollow calcium phosphate nanoparticles capable of encapsulating poorly water-soluble molecules were produced by self-assembly. Previously reported were solid calcium phosphate nanoparticles and water-filled calcium phosphate nanocapsules suited for encapsulating mostly hydrophilic, but not hydrophobic compounds. Here, calcium phosphate was deposited around 100 nm diameter, 1,2-dioleoyl-sn-glycero-3-phosphate stabilized soybean oil nanoemulsions using either calcium chloride or NaOH titrations to achieve shell thickness between 20-70 nm. The surface was functionalized with carboxylic acid via the addition of carboxyethylphosphonic acid to attach Molecular Probes AB-594C antibody using sulpho-n-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride with an efficiency of approximately 70%, while retaining near complete antibody function. Hydrophobic pyrene was encapsulated with an efficiency of 95%, at concentrations much higher than its water solubility limit, and exhibited spectral features characteristic of a hydrophobic environment. These materials can be used in the targeted delivery of many useful, yet poorly water-soluble pharmaceutical and nutraceutical compounds.

The prevalent distrust of science

An account of the now common distrust of science, an explanation of its origins and a suggestion of what may, and indeed, should be done about it.

When to help farm animals grow faster

The European Commission has broken with precedent by sponsoring an independent scientific conference on the role of growth-promoting substances in animal husbandry.