The effect of age on the acquisition and selection of cancer driver mutations in sun-exposed normal skin

BACKGROUND: The accumulation of somatic mutations contributes to ageing and cancer. Sunlight is the principal aetiological factor associated with skin cancer development. However, genetic and phenotypic factors also contribute to skin cancer risk. This study aimed at exploring the role of photoaging, as well as other well-known epidemiological risk factors, in the accumulation of somatic mutations in cancer-free human epidermis. MATERIAL AND METHODS: We deeply sequenced 46 genes in normal skin biopsies from 127 healthy donors, from which phenotypic data (including age, pigmentation-related genotype and phenotype) and sun exposure habits were collected. We determined the somatic mutational burden, mutational signatures, clonal selection and frequency of driver mutations in all samples. RESULTS: Our results reveal an exponential accumulation of UV-related somatic mutations with age, matching skin cancer incidence. The increase of mutational burden is in turn modified by an individual's skin phototype. Somatic mutations preferentially accumulated in cutaneous squamous cell carcinoma (cSCC) cancer genes and clonally expanded with age, with distinct mutational processes underpinning different age groups. Our results suggest loss of fidelity in transcription-coupled repair later in life. CONCLUSION: Our findings reveal that aging is not only associated with an exponential increase in the number of somatic mutations accumulated in normal epidermis, but also with selection and expansion of cancer-associated mutations. Aged, sun-exposed normal skin is thus an extended mosaic of multiple clones with driver mutations, poised for the acquisition of transforming events

Estudo quantitativo das células de Langerhans em carcinomas basocelulares com maior e menor potencial de agressividade local Quantitative study of Langerhans cells in basal cell carcinoma with higher or lower potential of local aggressiveness

FUNDAMENTOS - O carcinoma basocelular localiza-se principalmente em áreas expostas ao sol, apresentando formas clínicas e histológicas diferentes, algumas com grande e outras com pequena agressividade local. Células de Langerhans participam ativamente do sistema imune da pele. OBJETIVO - Avaliar quantitativamente as células de Langerhans sobrepostas aos carcinomas basocelulares de maior e menor potencial de agressividade local, assim como nas respectivas epidermes sãs adjacentes. MÉTODOS - Dois grupos com 14 preparações histológicas cada. No primeiro, carcinoma basocelular de menor potencial de agressividade local e, no segundo, carcinoma basocelular de maior potencial. Empregou-se a imunoistoquímica com proteína S100 para identificação das células de Langerhans. Utilizando microscópio óptico em aumento de 400 vezes e a grade morfométrica de Weibel, foram contadas as células de Langerhans presentes em sete campos, obtendo-se a média em cada lâmina. Foi utilizado teste estatístico de Wilcoxon para análise estatística. RESULTADOS - No grupo de menor potencial de agressividade local, na epiderme sã adjacente houve aumento significativo no número de células de Langerhans comparado ao da epiderme sobreposta ao carcinoma basocelular (p d 0,05). No grupo de maior potencial de agressividade local, não houve diferença com significado estatístico (p > 0,05). CONCLUSÃO - O maior número de células de Langerhans na epiderme sã vizinha à lesão tumoral de menor potencial de agressividade local poderia representar uma maior resistência imunológica da epiderme, limitando a agressividade da neoplasia.<br>BACKGROUNDS - Basal cell carcinoma affects areas of the body that have been exposed to the sun, and this disorder has different clinical and histopathologic presentations. Some of these forms have a higher potential of local aggressiveness, while others have a lower potential. Langerhans cells actively participate in the skin immune system. OBJECTIVES - To quantitatively evaluate the number of Langerhans cells on the epidermis of basal cell carcinoma with lower and higher potential of local aggressiveness and on adjacent normal epidermis. METHODOLOGY - The authors divided the sample into two groups with 14 histological slides each: one with basal cell carcinoma with lower potential of local aggressiveness and the other with basal cell carcinoma with higher potential of local aggressiveness. Immunohistochemistry with S-100 protein was used in the identification of Langerhans Cells. Langerhans cells present in 7 microscopic fields were counted using optical microscopy (400X magnification) and Weibel's morphometric grade. The mean for each lamina was obtained. Wilcoxon's statistical test was employed. RESULTS - In the group with lower potential of local aggressiveness, there was a significant increase in the number of Langerhans cells in the adjacent normal epidermis, as compared with the number of cells in the epidermis superposed to the basal cell carcinoma (pd 0.05). There was no significant statistical difference in the group with higher potential of local aggressiveness (p >0.05). CONCLUSION - The higher number of Langerhans cells in the normal epidermis adjacent to the tumoral lesion with lower potential of local aggressiveness could indicate greater immunological resistance of the epidermis, thus limiting the aggressiveness of the neoplasm

Kaposi's Sarcoma-Associated Herpesvirus Infection of Endothelial Cells Inhibits Neutrophil Recruitment through an Interleukin-6-Dependent Mechanism: a New Paradigm for Viral Immune Evasion ▿

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent of Kaposi's sarcoma (KS), an endothelial cell (EC) neoplasm characterized by dysregulated angiogenesis and inflammation. KSHV infection of EC causes production of proinflammatory mediators, regarded as possible initiators of the substantial mononuclear leukocyte recruitment seen in KS. Conversely, KSHV immune evasion strategies exist, such as degradation of EC leukocyte adhesion receptors by viral proteins. Here, we report the effects of KSHV infection of primary EC on recruitment of flowing leukocytes. Infection did not initiate adhesion of any leukocyte subset per se. However, on cytokine-stimulated EC, KSHV specifically inhibited neutrophil, but not PBL or monocyte, transmigration, an observation consistent with the inflammatory cell profile found in KS lesions in vivo. This inhibition could be recapitulated on uninfected EC using supernatant from infected cultures. These supernatants contained elevated levels of human interleukin 6 (hIL-6), and both the KSHV- and the supernatant-induced inhibitions of neutrophil transmigration were abrogated in the presence of a hIL-6 neutralizing antibody. Furthermore, preconditioning of EC with hIL-6 mimicked the effect of KSHV. Using RNA interference (RNAi), we show that upregulation of suppressor of cytokine signaling 3 (SOCS3) was necessary for this effect of hIL-6. These studies reveal a novel paracrine mode of KSHV immune evasion, resulting in reduced recruitment of neutrophils, a cell type whose antiviral and antitumor roles are becoming increasingly appreciated. Moreover, the findings have implications for our understanding of the contribution of hIL-6 to the pathogenesis of other inflammatory disorders and tumors in which this cytokine is abundant