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The IGF-1/IGF-1R signaling axis in the skin: a new role for the dermis in aging-associated skin cancer.

ABSTRACT: The appropriate response of human keratinocytes to ultraviolet-B (UVB) is dependent on the activation status of the insulin-like growth factor 1 (IGF-1) receptor. Keratinocytes grown in conditions in which the IGF-1 receptor is inactive inappropriately replicate in the presence of UVB-induced DNA damage. In human skin, epidermal keratinocytes do not express IGF-1, and hence the IGF-1 receptor on keratinocytes is activated by IGF-1 secreted from dermal fibroblasts. We now show that the IGF-1 produced by human fibroblasts is essential for the appropriate UVB response of keratinocytes. Furthermore, the expression of IGF-1 is silenced in senescent fibroblasts in vitro. Using quantitative reverse transcriptase-PCR and immunohistochemisty, we can show that IGF-1 expression is also silenced in geriatric dermis in vivo. The diminished IGF-1 expression in geriatric skin correlates with an inappropriate UVB response in geriatric volunteers. Finally, the appropriate UVB response is restored in geriatric skin in vivo through pretreatment with exogenous IGF-1. These studies provide further evidence for a role of the IGF-1 receptor (IGF-1R) in suppressing UVB-induced carcinogenesis, suggest that fibroblasts have a critical role in maintaining appropriate activation of the keratinocyte IGF-1R, and imply that reduced expression of IGF-1 in geriatric skin could be an important component in the development of aging-related non-melanoma skin cancer.

SUBMITTER: Lewis DA

PROVIDER: S-EPMC2837099 | biostudies-literature | 2010 Mar

REPOSITORIES: biostudies-literature

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The IGF-1/IGF-1R signaling axis in the skin: a new role for the dermis in aging-associated skin cancer.

Lewis D A DA Travers J B JB Somani A-K AK Spandau D F DF

Oncogene 20091207 10

The appropriate response of human keratinocytes to ultraviolet-B (UVB) is dependent on the activation status of the insulin-like growth factor 1 (IGF-1) receptor. Keratinocytes grown in conditions in which the IGF-1 receptor is inactive inappropriately replicate in the presence of UVB-induced DNA damage. In human skin, epidermal keratinocytes do not express IGF-1, and hence the IGF-1 receptor on keratinocytes is activated by IGF-1 secreted from dermal fibroblasts. We now show that the IGF-1 prod ...[more]

PMID: 19966862

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Project description:BACKGROUND: Psoriasis is a complex disease at the cellular, genomic and genetic levels. The role of microRNAs in skin development was shown in a keratinocyte-specific Dicer knockout mouse model. Considering that two main characteristics of psoriasis are keratinocytes hyperproliferation and abnormal skin differentiation, we hypothesized that aberrant microRNA expression contributes to the psoriatic phenotype. Here, we describe the differential expression of miRNAs in psoriatic involved and uninvolved skin as compared to normal skin, revealing an additional aspect of this complex disorder. METHODOLOGY/PRINCIPAL FINDINGS: Expression arrays were used to compare microRNA expression in normal skin versus psoriatic involved and uninvolved skin. Fourteen differentially expressed microRNAs were identified, including hsa-miR-99a, hsa-miR-150, hsa-miR-423 and hsa-miR-197. The expression of these microRNAs was reevaluated by qPCR. IGF-1R, which is involved in skin development and the pathogenesis of psoriasis, is a predicted target of hsa-miR-99a. In an in situ hybridization assay, we found that IGF-1R and miR-99a are reciprocally expressed in the epidermis. Using a reporter assay, we found that IGF-1R is targeted by hsa-miR-99a. Moreover, over expression of miR-99a in primary keratinocytes down-regulates the expression of the endogenous IGF-1R protein. Over expression of miR-99a also inhibits keratinocyte proliferation and increases Keratin 10 expression. These findings suggest that overexpression of hsa-miR-99a in keratinocytes drives them towards differentiation. In primary keratinocytes grown in high Ca(++), miR-99a expression increases over time. Finally, we found that IGF1 increases the expression of miR-99a. CONCLUSIONS/SIGNIFICANCE: We identified several microRNAs that are expressed differentially in normal and psoriatic skin. One of these miRNAs is miR-99a that regulates the expression of IGF-1R. Moreover, miR-99a seems to play a role in the differentiation of keratinocytes. We suggest that miR-99a is one of the regulators of the IGF-1R signaling pathway in keratinocytes. Activation of IGF1 signaling results in elevation of miR-99a which represses the expression of IGF-1R.

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Dataset Information

The IGF-1/IGF-1R signaling axis in the skin: a new role for the dermis in aging-associated skin cancer.

Publications

The IGF-1/IGF-1R signaling axis in the skin: a new role for the dermis in aging-associated skin cancer.

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