Genome-wide co-localization of active EGFR and downstream ERK pathway kinases mirrors mitogen-inducible RNA polymerase 2 genomic occupancy.

Genome-wide mechanisms that coordinate expression of subsets of functionally related genes are largely unknown. Recent studies show that receptor tyrosine kinases and components of signal transduction cascades including the extracellular signal-regulated protein kinase (ERK), once thought to act predominantly in the vicinity of plasma membrane and in the cytoplasm, can be recruited to chromatin encompassing transcribed genes. Genome-wide distribution of these transducers and their relationship to transcribing RNA polymerase II (Pol2) could provide new insights about co-regulation of functionally related gene subsets. Chromatin immunoprecipitations (ChIP) followed by deep sequencing, ChIP-Seq, revealed that genome-wide binding of epidermal growth factor receptor, EGFR and ERK pathway components at EGF-responsive genes was highly correlated with characteristic mitogen-induced Pol2-profile. Endosomes play a role in intracellular trafficking of proteins including their nuclear import. Immunofluorescence revealed that EGF-activated EGFR, MEK1/2 and ERK1/2 co-localize on endosomes. Perturbation of endosome internalization process, through the depletion of AP2M1 protein, resulted in decreased number of the EGFR containing endosomes and inhibition of Pol2, EGFR/ERK recruitment to EGR1 gene. Thus, mitogen-induced co-recruitment of EGFR/ERK components to subsets of genes, a kinase module possibly pre-assembled on endosome to synchronize their nuclear import, could coordinate genome-wide transcriptional events to ensure effective cell proliferation.

Aberrant DNA methylation of alternative promoter of DLC1 isoform 1 in meningiomas.

DLC1 encodes GTPase-activating protein with a well-documented tumor suppressor activity. This gene is downregulated in various tumors through aberrant promoter hypermethylation. Five different DLC1 isoforms can be transcribed from alternative promoters. Tumor-related DNA methylation of the DLC1 isoform 1 alternative promoter was identified as being hypermethylated in meningiomas in genome-wide DNA methylation profiling. We determined the methylation pattern of this region in 50 meningioma FFPE samples and sections of 6 normal meninges, with targeted bisulfite sequencing. All histopathological subtypes of meningiomas showed similar and significant increase of DNA methylation levels. High DNA methylation was associated with lack of DLC1 protein expression in meningiomas as determined by immunohistochemistry. mRNA expression levels of 5 isoforms of DLC1 transcript were measured in an additional series of meningiomas and normal meninges. The DLC1 isoform 1 was found as the most expressed in normal control tissue and was significantly downregulated in meningiomas. Transfection of KT21 meningioma cell line with shRNA targeting DLC1 isoform 1 resulted in increased activation of RHO-GTPases assessed with pull-down assay, enhanced cell migration observed in scratch assay as well as slight increase of cell metabolism determind by MTT test. Results indicate that isoform 1 represents the main pool of DLC1 protein in meninges and its downregulation in meningiomas is associated with hypermethylation of CpG dinucleotides within the corresponding promoter region. This isoform is functional GAP protein and tumor suppressor and targeting of its expression results in the increase of DLC1 related cell processes: RHO activation and cell migration.

DNA methylation status is more reliable than gene expression at detecting cancer in prostate biopsy.

BACKGROUND: We analysed critically the potential usefulness of RNA- and DNA-based biomarkers in supporting conventional histological diagnostic tests for prostate carcinoma (PCa) detection. METHODS: Microarray profiling of gene expression and DNA methylation was performed on 16 benign prostatic hyperplasia (BPH) and 32 cancerous and non-cancerous prostate samples extracted by radical prostatectomy. The predictive value of the selected biomarkers was validated by qPCR-based methods using tissue samples extracted from the 58 prostates and, separately, using 227 prostate core biopsies. RESULTS: HOXC6, AMACR and PCA3 expression showed the best discrimination between PCa and BPH. All three genes were previously reported as the most promising mRNA-based markers for distinguishing cancerous lesions from benign prostate lesions; however, none were sufficiently sensitive and specific to meet the criteria for a PCa diagnostic biomarker. By contrast, DNA methylation levels of the APC, TACC2, RARB, DGKZ and HES5 promoter regions achieved high discriminating sensitivity and specificity, with area under the curve (AUCs) reaching 0.95-1.0. Only a small overlap was detected between the DNA methylation levels of PCa-positive and PCa-negative needle biopsies, with AUCs ranging between 0.854 and 0.899. CONCLUSIONS: DNA methylation-based biomarkers reflect the prostate malignancy and might be useful in supporting clinical decisions for suspected PCa following an initial negative prostate biopsy.

Prognostic value of microRNA expression in operable non-small cell lung cancer patients.

BACKGROUND: About 50% of non-small cell lung cancer (NSCLC) patients develop distant metastases following pulmonary resection. Currently, there are no reliable factors allowing for individual selection of high-risk patients for adjuvant systemic therapies. METHODS: We assessed by quantitative reverse transcription PCR microRNA (miRNA) expression in 273 stage I-IIIA NSCLC samples. Expression of 677 miRNAs was evaluated in fresh-frozen tumour samples in the training cohort of 50 squamous cell carcinoma (SCC) patients who underwent curative surgery. Of those, 20 patients developed distant metastases, and 30 were free of recurrence for >4 years. In the second step, miRNAs with highest predictive value for distant relapse were re-evaluated in formalin-fixed paraffin-embedded material in an independent group of 134 stage I-IIIA SCC patients. Additionally, the same miRNAs were investigated in 89 lung adenocarcinoma (AC) patients and in normal lung parenchyma (NLP). RESULTS: In the training cohort of SCC, six miRNAs were differently expressed in the non-recurrent vs recurrent groups and correlated with distant recurrence-free survival, however none reached the level of significance after correction for multiple testing. Of these six miRNAs, miR-662, -192 and -192* were confirmed as prognostic in the independent SCC cohort. Expression of miR-128, -10b, -502-3p and -192 differed between SCC and AC, and miR-128 and -192 - between NLP and NSCLC. CONCLUSIONS: We identified three new miRNAs predictive of distant relapse in operable SCC. Future miRNA studies should account for differences between NSCLC subtypes.