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Progression from actinic keratosis to cutaneous squamous cell carcinoma involves miR-204 silencing and a switch towards STAT3 activation

ABSTRACT: Squamous cell carcinoma is the second most common skin cancer and frequently progress from an intraepithelial actinic keratosis. The role of microRNAs during the progression from actinic keratosis to cutaneous squamous cell carcinoma (cSCC) remains to be elicited. By using an Agilent microRNA expression microarray we found the expression of miR-204 to be markedly downregulated in cSCC when compared to actinic keratoses. DNA methylation of the TRPM3 promoter region upstream of miR-204-5p was identified as one of the repressive mechanisms that accounts for miR-204 silencing in cSCC. Functional studies on HaCaT cells revealed that this microRNA downregulates the Signal Transducer and Activator of Transcription 3 (STAT3) pathway and favours the MAPK signaling pathway, likely acting through PTPN11, a tyrosine phosphatase that is a direct miR-204 target. We found that activated STAT3, as detected by pY705-STAT3 immunofluorescence, is retained in the membrane and cytoplasm compartment in AK, whereas cSCC displayed STAT3 in the nuclei. Taken together, our data indicates that MiR-204 may act as a “rheostat” that controls the signaling towards the MAPK pathway or the STAT3 pathway.

ORGANISM(S): Homo sapiens

PROVIDER: GSE71953 | GEO | 2016/12/31

SECONDARY ACCESSION(S): PRJNA292560

REPOSITORIES: GEO

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Project description:Skin carcinogenesis is known to be a multi-step process with several stages along its malignant evolution. We hypothesized that transformation of normal epidermis to cutaneous squamous cell carcinoma (cSCC) is causally linked to alterations in miRNA expression. For this end we decided to evaluate their alterations in the pathologic states ending in cSCC. Total RNA was extracted from FFPE biopsies of five stages along the malignant evolution of keratinocytes towards cSCC: Normal epidermis, severe solar elastosis (SE), actinic keratosis (KIN1-2), advanced actinic keratosis, (KIN3) and well differentiated cSCC. Next generation small RNA sequencing was performed. We found that 18 miRNAs are over expressed and 28 miRNAs are under expressed in cSCC compared to normal epidermis. miR-424, miR-320, miR- 222 and miR-15a showed the highest fold change among the over expressed miRNAs. And miR-100, miR-101 and miR-497 showed the highest fold change among the under expressed miRNAs. Heat map of hierarchical clustering analysis of significantly changed miRNAs and principle component analysis disclosed that the most prominent change in miRNAs expression occurred in the switch from “early” stages; normal epidermis, solar elastosis and early actinic keratosis to the “late” stages of epidermal carcinogenesis; late actinic keratosis and cSCC. We found several miRNAs with "stage specific" alterations while others display a clear “gradual”, either progressive increase or decrease in expression along the malignant evolution of keratinocytes. The observed alterations focused in miRNAs involved in the regulation of AKT/mTOR or in those involved in epithelial to mesenchymal transition. We chose to concentrate on the evaluation of the molecular role of miR- 497. We found that it induces reversion of epithelial to mesenchymal transition. We proved that SERPINE-1 is its biochemical target. The present study allows us to further study the pathways which are regulated by miRNAs along the malignant evolution of keratinocytes towards cSCC.

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Progression from actinic keratosis to cutaneous squamous cell carcinoma involves miR-204 silencing and a switch towards STAT3 activation

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