ETS1 Mediates MEK1/2-Dependent Overexpression of Cancerous Inhibitor of Protein Phosphatase 2A (CIP2A) in Human Cancer Cells

EGFR-MEK-ERK signaling pathway has an established role in promoting malignant growth and disease progression in human cancers. Therefore identification of transcriptional targets mediating the oncogenic effects of the EGFR-MEK-ERK pathway would be highly relevant. Cancerous inhibitor of protein phosphatase 2A (CIP2A) is a recently characterized human oncoprotein. CIP2A promotes malignant cell growth and is over expressed at high frequency (40–80%) in most of the human cancer types. However, the mechanisms inducing its expression in cancer still remain largely unexplored. Here we present systematic analysis of contribution of potential gene regulatory mechanisms for high CIP2A expression in cancer. Our data shows that evolutionary conserved CpG islands at the proximal CIP2A promoter are not methylated both in normal and cancer cells. Furthermore, sequencing of the active CIP2A promoter region from altogether seven normal and malignant cell types did not reveal any sequence alterations that would increase CIP2A expression specifically in cancer cells. However, treatment of cancer cells with various signaling pathway inhibitors revealed that CIP2A mRNA expression was sensitive to inhibition of EGFR activity as well as inhibition or activation of MEK-ERK pathway. Moreover, MEK1/2-specific siRNAs decreased CIP2A protein expression. Series of CIP2A promoter-luciferase constructs were created to identify proximal −27 to −107 promoter region responsible for MEK-dependent stimulation of CIP2A expression. Additional mutagenesis and chromatin immunoprecipitation experiments revealed ETS1 as the transcription factor mediating stimulation of CIP2A expression through EGFR-MEK pathway. Thus, ETS1 is probably mediating high CIP2A expression in human cancers with increased EGFR-MEK1/2-ERK pathway activity. These results also suggest that in addition to its established role in invasion and angiogenesis, ETS1 may support malignant cellular growth via regulation of CIP2A expression and protein phosphatase 2A inhibition

Genetic alterations of C9orf72, SOD1, TARDBP, FUS, and UBQLN2 genes in patients with Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis is the most common motor neuron disease of the adulthood. Genetic analyses performed on cases with sporadic ALS (sALS) and familial ALS (fALS) have revealed mutations most commonly in the genes C9orf72, SOD1, TARDBP, FUS, and UBQLN2. The aim of this study was to investigate the presence and incidence of these most common genomic alterations in these genes of 30 ALS cases. Increase in the number of hexanucleotide repeats within the gene C9orf72 was investigated using the fragment analysis method. A heterozygote c.-45 + 162_-45 + 163insGGGGCC alteration was observed in the first intron of the C9orf72 gene in only two sALS cases (6.6%), c.72 + 133C>T alteration was observed in the first intron of the SOD1 gene in six fALS and two sALS cases (26.6%), a c.169 + 41C>A alteration was observed in the second intron of the same gene in one case, a c.239 + 34A>C alteration was observed in the third intron of the same gene in three fALS cases (10%), and a c.714 + 67_714 + 68insG alteration was observed in the fifth intron of the TARDBP gene in six sALS cases (20%). Three different genomic alterations were detected in the FUS gene; two silent variants p.G49G (c.147C>A) in 3 cases (10%) and p.Y97Y (c.291C>T) in 25 cases (83%) and an intronic variant c.1067-61T˃C in 4 cases (13%). A novel missense variant, p.G457H (c.1371G>C), was observed in the UBQLN2 gene in one case with sALS. Our study has revealed three novel and previously reported genomic alterations in the ALS-related genes