Association of FGFR4 genetic polymorphisms with prostate cancer risk and prognosis.

The fibroblast growth factor receptor 4 (FGFR4) is thought to be involved in many critical cellular processes and has been associated with prostate cancer risk. Four single nucleotide polymorphisms (SNPs) within or near FGFR4 were analyzed in a population-based study of 1458 prostate cancer patients and 1352 age-matched controls. We found no evidence to suggest that any of the FGFR4 SNP genotypes were associated with prostate cancer risk or with disease aggressiveness, Gleason score or stage. A weak association was seen between rs351855 and prostate cancer-specific mortality. Subset analysis of cases that had undergone radical prostatectomy revealed an association between rs351855 and prostate cancer risk. Although our results confirm an association between FGFR4 and prostate cancer risk in radical prostatectomy cases, they suggest that the role of FGFR4 in disease risk and outcomes at a population-based level appears to be minor.

Rare germline mutations in the BRCA2 gene are associated with early-onset prostate cancer.

Studies of families who segregate BRCA2 mutations have found that men who carry disease-associated mutations have an increased risk of prostate cancer, particularly early-onset disease. A study of sporadic prostate cancer in the UK reported a prevalence of 2.3% for protein-truncating BRCA2 mutations among patients diagnosed at ages < or =55 years, highlighting the potential importance of this gene in prostate cancer susceptibility. To examine the role of protein-truncating BRCA2 mutations in relation to early-onset prostate cancer in a US population, 290 population-based patients from King County, Washington, diagnosed at ages <55 years were screened for germline BRCA2 mutations. The coding regions, intron-exon boundaries, and potential regulatory elements of the BRCA2 gene were sequenced. Two distinct protein-truncating BRCA2 mutations were identified in exon 11 in two patients. Both cases were Caucasian, yielding a mutation prevalence of 0.78% (95% confidence interval (95%CI) 0.09-2.81%) and a relative risk (RR) of 7.8 (95%CI 1.8-9.4) for early-onset prostate cancer in white men carrying a protein-truncating BRCA2 mutation. Results suggest that protein-truncating BRCA2 mutations confer an elevated RR of early-onset prostate cancer. However, we estimate that <1% of early-onset prostate cancers in the general US Caucasian population can be attributed to these rare disease-associated BRCA2 mutations.

Granulocyte-macrophage colony-stimulating factor stimulation results in phosphorylation of cAMP response element-binding protein through activation of pp90RSK.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) activates several kinases and transcription factors through interaction with a heterodimeric receptor complex. We previously demonstrated that phosphorylation of the cyclic adenosine monophosphate (cAMP) response element-binding protein, CREB, occurs through a protein kinase A-independent pathway and is required for GM-CSF-induced transcriptional activation of the immediate early gene, early growth response-1 (egr-1). Recent reports indicate that receptor tyrosine kinases can induce CREB phosphorylation through activation of pp90RSK. We performed immune complex kinase assays in the human myeloid leukemic cell line, TF-1, which revealed that GM-CSF induced pp90RSK activation and phosphorylation of CREB within 5 minutes of stimulation. Transfection with the kinase-defective pp90RSK expression plasmid demonstrated a statistically significant decrease in transcriptional activation of a -116 CAT/egr-1 promoter construct in response to GM-CSF. Furthermore, activation of pp90RSK, CREB and egr-1 in GM-CSF-treated cells was inhibited by the presence of the inhibitor, PD98059. In this study, we report that GM-CSF induces CREB phosphorylation and egr-1 transcription by activating pp90RSK through an MEK-dependent signaling pathway. (Blood. 2000;95:2552-2558)

Mechanism of transcriptional activation of the immediate early gene Egr-1 in response to PIXY321.

Studies with the granulocyte-macrophage colony-stimulating factor (GM-CSF)/interleukin-3 (IL-3) fusion protein, PIXY321, demonstrated enhanced biological activity of this molecule in comparison with GM-CSF or IL-3 alone or in combination. Experiments were performed to study the mechanisms resulting in PIXY321-induced egr-1 expression in human myeloid leukemic cells (TF-1). Transfections of egr-1 promoter constructs revealed that PIXY321 stimulation resulted in fourfold induction of the -116 and -600 nucleotide (nt) constructs. We transfected a -116 nt construct containing a deletion of the cyclic AMP response element (CRE) or mutation in the serum response element (SRE) and demonstrated that both the SRE and CRE are necessary for maximal induction. However, PIXY321 stimulation resulted in 2.5-fold induction of a SRE-CRE-containing construct (P < .05), suggesting that the SRE and CRE are sufficient for PIXY321 responsiveness. Electrophoretic mobility shift assays (EMSA) revealed that the CRE binding protein (CREB) was phosphorylated on serine 133 in PIXY321-stimulated but not -unstimulated extracts from cells cultured in GM-CSF. By Western analysis and EMSA, CREB was constitutively phosphorylated in TF-1 cells grown on PIXY321 before growth factor and serum starvation. However, in TF-1 cells grown on GM-CSF before starvation, CREB phosphorylation was observed 10 minutes after PIXY321 stimulation. Further-more, ENSAs with PIXY321-stimulated and -unstimulated extracts demonstrated the presence of specific proteins that recognize the SRE. Our data demonstrate that transcriptional regulation of egr-1 by PIXY321 is mediated by the CRE and SRE.