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EGAS00001002165-8-sc-2020-06-03T10:04:38Z - samples

ABSTRACT: The risk of getting non-melanoma skin cancer varies over 40-fold across the body. Here we map mutations in normal skin in high and low risk sites in normal donors and those with an increased risk of skin cancer. The density of mutations varied widely, with evidence of positive and negative genetic selection.Ã‚Â Regional differences in mutational signatures in high and low cancer risk sites and preferential selection of mutants of TP53 in high risk skin and FAT1 in lower risk skin were observed. 10% of clones had copy number changes in cancer associated genes and the largest had multiple driver mutations with loss of heterozygosity. In hair follicles, a proposed site of origin of skin cancers, mutations in the upper follicle resembled adjacent skin, but the lower follicle was sparsely mutated. We conclude cancer risk reflects the efficiency of transformation of oncogenic mutants rather than the density of mutant clones.

PROVIDER: EGAD00001006194 | EGA |

REPOSITORIES: EGA

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Project description:Introduction Mammographic density (MD), as assessed from film screen mammograms, is determined by the relative content of adipose, connective and epithelial tissue in the female breast. In epidemiological studies, a high percentage of MD confers a four to six fold risk elevation of developing breast cancer, even after adjustment for other known breast cancer risk factors. However, the biologic correlates of density are little known. Methods Gene expression analysis using whole genome arrays was performed on breast biopsies from 143 women; 79 women with no malignancy (healthy women) and 64 newly diagnosed breast cancer patients, both included from mammographic centres. Percent MD was determined using a previously validated, computerized method on scanned mammograms. Significance analysis of microarrays (SAM) was performed to identify genes influencing MD and generalized regression models were used to assess the independent contribution from different variables to MD. Results SAM-analysis identified 24 genes differentially expressed between samples from breasts with high and low MD. These genes included three uridine 5'-diphospho-glucuronosyltransferase (UGT) genes and the oestrogen receptor gene (ESR1). These genes were down-regulated in samples with high MD compared to those with low MD. The UGT gene products, which are known to inactivate oestrogen metabolites, were also down-regulated in tumour samples compared to samples from healthy individuals. Several single nucleotide polymorphisms (SNPs) in the UGT genes associated with the expression of UGT and other genes in their vicinity were identified. Conclusions Three UGT enzymes were lower expressed both in breast tissue biopsies from healthy women with high MD and in biopsies from newly diagnosed breast cancers. The association was strongest among young women and women using hormonal therapy. UGT2B10 predicts MD independently of age, hormone therapy and parity. Our results indicate that down-regulation of UGT genes in women exposed to female sex hormones is associated with high MD and might increase the risk of breast cancer. Gene expression analysis of breast biopsies from 143 women, 79 non-cancer (healthy women with no cancer who had a mammogram taken) and 64 breast cancer.

Project description:The skin epidermis is constantly renewed throughout life. Disruption of the balance between renewal and differentiation can lead to uncontrolled growth and tumor initiation. Basal cell carcinoma (BCC) is the most frequent cancer in human. Cell competition is a biological process that leads to the elimination of cells by winner cells, which have been proposed to be important for tumour initiation. Recent studies identified somatic mutations in cancer drivers in normal tissues that get colonized by clones carrying oncogenic mutations. However, how the different oncogenic mutations impact the balance between renewal and differentiation and lead to clonal expansion, cell competition, tissue colonization and tumor development is currently unknown. Here, using multidisciplinary approaches combining in vivo clonal analysis using intra-vital microscopy, single cell analysis, and functional analysis, we defined at a single cell resolution in living animals how mutations associated with BCC development (SmoM2) affect clonal competition and tumor initiation in real time. We found that SmoM2 expression in the ear epidermis induces a stereotypical pattern of cell competition with clonal expansion leading tumor initiation and invasion. In contrast, SmoM2 expression in the back skin epidermis led to a similar clonal expansion that induces lateral cell competition but without inducing dermal invasion and tumor formation. Single cell analysis showed that oncogene expression is associated with a cellular reprogramming of adult interfollicular cells into embryonic hair follicle progenitor (EHFP) state in the ear but not in the back skin. Comparison between ear and back skin epidermis revealed a very different composition of the dermis with increased stiffness and a denser collagen 1 network in the back skin. Decreasing Collagen 1 expression in the back skin overcame the natural resistance of these cells to undergo EHFP reprogramming and tumor initiation following SmoM2 expression. Altogether our study demonstrates that ECM composition controls the mode of clonal competition and competence to undergo oncogenic transformation upon oncogene expression.

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EGAS00001002165-8-sc-2020-06-03T10:04:38Z - samples

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