The POU transcription factor Drifter/Ventral veinless regulates expression of Drosophila immune defense genes.

Innate immunity operates as a first line of defense in multicellular organisms against infections caused by different classes of microorganisms. Antimicrobial peptides (AMPs) are synthesized constitutively in barrier epithelia to protect against microbial attack and are also upregulated in response to infection. Here, we implicate Drifter/Ventral veinless (Dfr/Vvl), a class III POU domain transcription factor, in tissue-specific regulation of the innate immune defense of Drosophila. We show that Dfr/Vvl is highly expressed in a range of immunocompetent tissues, including the male ejaculatory duct, where its presence overlaps with and drives the expression of cecropin, a potent broad-spectrum AMP. Dfr/Vvl overexpression activates transcription of several AMP genes in uninfected flies in a Toll pathway- and Imd pathway-independent manner. Dfr/Vvl activates a CecA1 reporter gene both in vitro and in vivo by binding to an upstream enhancer specific for the male ejaculatory duct. Further, Dfr/Vvl and the homeodomain protein Caudal (Cad) activate transcription synergistically via this enhancer. We propose that the POU protein Dfr/Vvl acts together with other regulators in a combinatorial manner to control constitutive AMP gene expression in a gene-, tissue-, and sex-specific manner, thus promoting a first-line defense against infection in tissues that are readily exposed to pathogens.

NRAS and BRAF mutations in melanoma tumours in relation to clinical characteristics: a study based on mutation screening by pyrosequencing.

We have previously demonstrated the use of pyrosequencing to investigate NRAS [neuroblastoma RAS viral (v-ras) oncogene homolog] mutations in melanoma biopsies. Here, we expanded the analysis to include BRAF (V-raf murine sarcoma viral oncogene homolog B1), another member of the Ras-Raf-mitogen-activated protein kinase (MAPK) signalling pathway, and analysed a total of 294 melanoma tumours from 219 patients. Mutations in BRAF exons 11 and 15 were identified in 156 (53%) tumours and NRAS exon 2 mutations in 86 (29%) tumours. Overall, mutations in NRAS or BRAF were found in 242 of 294 tumours (82%) and were found to be mutually exclusive in all but two cases (0.7%). Multiple metastases were analysed in 57 of the cases and mutations were identical in all except three, indicating that BRAF and NRAS mutations occur before metastasis. Association with preexisting nevi was significantly higher in BRAF mutated tumours (P=0.014). In addition, tumours with BRAF mutations showed a significantly more frequent moderate to pronounced infiltration of lymphocytes (P=0.013). NRAS mutations were associated with a significantly higher Clark level of invasion (P=0.022) than BRAF mutations. Age at diagnosis was significantly higher in tumours with NRAS mutations than in those with BRAF mutations (P=0.019). NRAS and BRAF mutations, however, did not influence the overall survival from time of diagnosis (P=0.7). In conclusion, the separate genotypes were associated with differences in several key clinical and pathological parameters, indicating differences in the biology of melanoma tumours with different proto-oncogene mutations.

Gene expression analysis of human epidermal keratinocytes after N-acetyl L-cysteine treatment demonstrates cell cycle arrest and increased differentiation.

OBJECTIVES: Several cancer prevention programmes have previously been executed using treatment of antioxidant compounds. The antioxidant N-acetyl L-cysteine (NAC), a membrane-permeable aminothiol, is a sulfhydryl reductant reducing oxidised glutathione, as well as being a precursor of intracellular cysteine and glutathione. A previous report based on the cellular response to NAC treatment showed that NAC induced a 10-fold more rapid differentiation in normal primary keratinocytes as well as a reversion of a colon carcinoma cell line from neoplastic proliferation to apical-basolateral differentiation. In order to investigate molecular events underlying the changes in proliferation and differentiation induced by NAC treatment, we performed global gene expression analysis of normal human epidermal keratinocytes in a time series. METHODS: Treated samples were compared to untreated samples through a reference design using a spotted cDNA array comprising approximately 30,000 features. B statistics was used to identify differentially expressed genes, and RT-PCR of a selected set of genes was performed to verify differential expression. RESULTS: The number of differentially expressed genes increased over time, starting with 0 at 30 min, 73 at 3 h and increasing to 952 genes at 48 h. Results of the expression analysis showed arrest of the cell cycle and an upregulation of cytoskeletal reorganisation, implicating increased differentiation. A comparison to gene ontology groups indicated downregulation of a large number of genes involved in cell proliferation and regulation of the cell cycle. CONCLUSIONS: A significant fraction of the differentially expressed genes could be classified according to their role in the differentiation process, demonstrating that NAC regulates the conversion from proliferation to differentiation at a transcriptional level.

Global gene expression analysis in time series following N-acetyl L-cysteine induced epithelial differentiation of human normal and cancer cells in vitro.

BACKGROUND: Cancer prevention trials using different types of antioxidant supplements have been carried out at several occasions and one of the investigated compounds has been the antioxidant N-acetyl-L-cysteine (NAC). Studies at the cellular level have previously demonstrated that a single supplementation of NAC induces a ten-fold more rapid differentiation in normal primary human keratinocytes as well as a reversion of a colon carcinoma cell line from neoplastic proliferation to apical-basolateral differentiation. The investigated cells showed an early change in the organization of the cytoskeleton, several newly established adherens junctions with E-cadherin/beta-catenin complexes and increased focal adhesions, all features characterizing the differentiation process. METHODS: In order to investigate the molecular mechanisms underlying the proliferation arrest and accelerated differentiation induced by NAC treatment of NHEK and Caco-2 cells in vitro, we performed global gene expression analysis of NAC treated cells in a time series (1, 12 and 24 hours post NAC treatment) using the Affymetrix GeneChip Human Genome U95Av2 chip, which contains approximately 12,000 previously characterized sequences. The treated samples were compared to the corresponding untreated culture at the same time point. RESULTS: Microarray data analysis revealed an increasing number of differentially expressed transcripts over time upon NAC treatment. The early response (1 hour) was transient, while a constitutive trend was commonly found among genes differentially regulated at later time points (12 and 24 hours). Connections to the induction of differentiation and inhibition of growth were identified for a majority of up- and down-regulated genes. All of the observed transcriptional changes, except for seven genes, were unique to either cell line. Only one gene, ID-1, was mutually regulated at 1 hour post treatment and might represent a common mediator of early NAC action. The detection of several genes that previously have been identified as stimulated or repressed during the differentiation of NHEK and Caco-2 provided validation of results. In addition, real-time kinetic PCR analysis of selected genes also verified the differential regulation as identified by the microarray platform. CONCLUSION: NAC induces a limited and transient early response followed by a more consistent and extensively different expression at later time points in both the normal and cancer cell lines investigated. The responses are largely related to inhibition of proliferation and stimulation of differentiation in both cell types but are almost completely lineage specific. ID-1 is indicated as an early mediator of NAC action.