Expression of Cyclic Adenosine 3′,5′-Monophosphate (cAMP)-Responsive Element Binding Protein and Inducible-cAMP Early Repressor Genes in Growth Hormone-Secreting Pituitary Adenomas with or without Mutations of theGsαGene

Abstract

In about 30-40% of GH-secreting adenomas, gain-of-function mutations of the Gsalpha gene, which convert this gene into an oncogene termed gsp, occur. Gsalpha mutations have been related to pituitary tumorigenesis. We focused on 2 nuclear transcription factors that are final targets of the cAMP-dependent pathway and are positively regulated by cAMP signaling, i.e. the cAMP-responsive element binding protein (CREB) and the inducible cAMP early repressor (ICER), that derives from alternative splicing of cAMP-responsive element modulator gene. We examined 21 GH-secreting adenomas, 8 with (gsp(+)) and 13 without (gsp(-)) a mutated Gsalpha. Analysis of CREB and ICER I/II messenger RNA revealed that the levels of both transcripts were higher in gsp(+) than in gsp(-) tumors (CREB/glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mean optical density +/- SE, 2.34 +/- 0.36 in gsp(+) vs. 0.99 +/- 0.22 in gsp(-), P = 0.003; ICER I/GAPDH, 0.53 +/- 0.15 in gsp(+) vs. 0.14 +/- 0.07 in gsp(-), P = 0.01; ICER II/GAPDH, 1.5 +/- 0.21 in gsp(+) vs. 0.83 +/- 0.13 in gsp(-), P = 0.01), although a few cases in both groups did not display this pattern of expression. Moreover, no positive correlation between the levels of CREB and ICER transcripts was observed, suggesting the possible presence of alterations in the mechanisms by which cAMP signaling directs the expression of CREB and/or ICER genes. Our results indicate a complex pattern of expression of nuclear transcription factors that mediate cAMP action in both gsp(+) and gsp(-) tumors, suggesting that, beside Gsalpha gene mutations, different and partially unknown molecular events may contribute to the pathogenesis of these tumors.

G-protein αolf subunit promotes cellular invasion, survival, and neuroendocrine differentiation in digestive and urogenital epithelial cells

“…Recent studies suggest that AC hyperactivity results from activating point mutations of R201C and Q227L within the GTPase domain of the Gas-gene, termed the gsp oncogene. These mutations were found primarily in a subset of growth hormone-secreting human pituitary tumors (Peri et al, 2001). In addition, external factors activating the Gas/PKA pathways also recruit the src oncogenic cascade to induce vascular endothelial growth factor expression, an angiogenic factor playing a key role in the progression of solid tumors (Fredriksson et al, 2000).…”

Interferon-γ Stimulates the Expression of the Inducible cAMP Early Repressor in Macrophages through the Activation of Casein Kinase 2

“…These conditions were in the exponential phase of amplification and, therefore, provided a direct correlation between the amount of products and RNA template abundance in the samples. The sequences of the primers were 5Ј-CAAAAG-CCCAACATGGCTG-3Ј and 5ЈCCAATTCACACTCTACAGCAG-3Ј for murine ICER I/I␥ (7), 5Ј-ATGGCTGTAACTGGAGATGAAACT-3Ј and 5Ј-CTAATCTGTTTTGGGAGAGCAAATGTC-3Ј for murine ICER I/II (33), 5Ј-CTGATGAGGAAACTGAACTTG-3Ј and 5Ј-TCGGCTCTCCAG-ACATTTTAC-3Ј for human ICERs (34,35), 5Ј-ATGGCAACTGTTCCT-GAACTCAACT-3Ј and 5Ј-CAGGACAGGTATAGATTCTTTCCTTT-3Ј for IL-1␤ (36), 5Ј-CTCGAGTAGGATGGTAGCACGCAA-3Ј and 5Ј-CAT-CTTCACGCTGAGCGCGAAGAA-3Ј for SOCS1 (37), 5Ј-TGAACTATG-CTTGGGCAGGG-3Ј and 5Ј-AGCGCCATCCATTTTCAGGG-3Ј for 28 S rRNA (38), 5Ј-CCCTTCATTGACCTCAACTACATGG-3Ј and 5Ј-AGT-CTTCTGGGTGGCAGTGATGG-3Ј for GAPDH, and 5Ј-TGGAGAAG-AGCTATGAGCTGCCTG-3Ј and 5Ј-GTGCCACCAGACAGCACTGTG-TTG-3Ј for ␤-actin (16, 30 -32). The PCR products were size-fractionated on a 2% (w/v) agarose gel, photographed using a Syngene gel documentation system (GRI), converted to an uncompressed TIFF file format, and quantified using the Quantiscan computer package (Biosoft).…”

“…To rule out that this was not a peculiar property of this cell line, the experiment was repeated using primary cultures of human monocyte-derived macrophages. Thus, RNA from untreated macrophages and those exposed to IFN-␥ were subjected to RT-PCR using primers that have been used previously to study ICER expression in pituitary adenomas and hyperfunctioning thyroid adenomas (34,35). These primers have been shown to amplify products of 657 and 257 bp, which correspond to ICER I and II, respectively, along with additional product(s) that contain partial sequences of the 657-bp product, which have been postulated to be the result of alternative splicing (35).…”