The activation status of the insulin-like growth factor-1 receptor (IGF-1R) regulates the cellular response of keratinocytes to ultraviolet B (UVB) exposure, both in vitro and in vivo. Geriatric skin is deficient in IGF-1 expression resulting in an aberrant IGF-1R-dependent UVB response which contributes to the development of aging-associated squamous cell carcinoma. Furthermore, our lab and others have reported that geriatric keratinocytes repair UVB-induced DNA damage less efficiently than young adult keratinocytes. Here, we show that IGF-1R activation influences DNA damage repair in UVB-irradiated keratinocytes. Specifically, in the absence of IGF-1R activation, the rate of DNA damage repair following UVB-irradiation was significantly slowed (using immortalized human keratinocytes) or inhibited (using primary human keratinocytes). Furthermore, inhibition of IGF-1R activity in human skin, using either ex vivo explant cultures or in vivo xenograft models, suppressed DNA damage repair. Primary keratinocytes with an inactivated IGF-1R also exhibited lower steady-state levels of nucleotide excision repair mRNAs. These results suggest that deficient UVB-induced DNA repair in geriatric keratinocytes is due in part to silenced IGF-1R activation in geriatric skin and provide a mechanism for how the IGF-1 pathway plays a role in the initiation of squamous cell carcinoma in geriatric patients.
Malignant mesothelioma (MM) is an aggressive and invasive neoplasm primarily affecting the pleura, peritoneum and pericardium. While mesothelioma commonly metastasizes to visceral organs, it has rarely been documented to involve the skin and subcutaneous tissue. There is a paucity of reports of cutaneous metastatic mesothelioma, and histologic examination is often challenging because the tumor closely mimics other primary and metastatic neoplasms. We report a case of a 75-year-old man presenting with a firm, hard nodule on his upper back, which on initial histologic evaluation resembled metastatic adenocarcinoma. However, upon review of his medical history and immunohistochemical evaluation of the lesion, the diagnosis of epithelioid MM metastatic to the skin was rendered. The purpose of this case report and review of the literature is to summarize the most effective available immunostains to aid in the diagnosis of this challenging entity, highlight the histologic similarities between metastatic epithelioid MM and other primary and metastatic neoplasms of the skin, and provide prognostic information for these rare tumors.
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