Estrogen receptor ß and 17ß-hydroxysteroid dehydrogenase type 6, a growth regulatory pathway that is lost in prostate cancer.

Estrogen receptor ß (ERß) is activated in the prostate by 5α-androstane-3ß,17ß-diol (3ß-Adiol) where it exerts antiproliferative activity. The proliferative action of the androgen receptor is activated by 5α-dihydrotestosterone (DHT). Thus, prostate growth is governed by the balance between androgen receptor and ERß activation. 3ß-Adiol is a high-affinity ligand and agonist of ERß and is derived from DHT by 3-keto reductase/3ß-hydroxysteroid dehydrogenase enzymes. Here, we demonstrate that, when it is expressed in living cells containing an estrogen response element-luciferase reporter, 17ß-hydroxysteroid dehydrogenase type 6 (17ßHSD6) converts the androgen DHT to the estrogen 3ß-Adiol, and this leads to activation of the ERß reporter. This conversion of DHT occurs at concentrations that are in the physiological range of this hormone in the prostate. Immunohistochemical analysis revealed that 17ßHSD6 is expressed in ERß-positive epithelial cells of the human prostate and that, in prostate cancers of Gleason grade higher than 3, both ERß and 17ßHSD6 are undetectable. Both proteins were present in benign prostatic hyperplasia samples. These observations reveal that formation of 3ß-Adiol via 17ßHSD6 from DHT is an important growth regulatory pathway that is lost in prostate cancer.

Birt-Hogg-Dubé renal tumors are genetically distinct from other renal neoplasias and are associated with up-regulation of mitochondrial gene expression.

BACKGROUND: Germline mutations in the folliculin (FLCN) gene are associated with the development of Birt-Hogg-Dubé syndrome (BHDS), a disease characterized by papular skin lesions, a high occurrence of spontaneous pneumothorax, and the development of renal neoplasias. The majority of renal tumors that arise in BHDS-affected individuals are histologically similar to sporadic chromophobe renal cell carcinoma (RCC) and sporadic renal oncocytoma. However, most sporadic tumors lack FLCN mutations and the extent to which the BHDS-derived renal tumors share genetic defects associated with the sporadic tumors has not been well studied. METHODS: BHDS individuals were identified symptomatically and FLCN mutations were confirmed by DNA sequencing. Comparative gene expression profiling analyses were carried out on renal tumors isolated from individuals afflicted with BHDS and a panel of sporadic renal tumors of different subtypes using discriminate and clustering approaches. qRT-PCR was used to confirm selected results of the gene expression analyses. We further analyzed differentially expressed genes using gene set enrichment analysis and pathway analysis approaches. Pathway analysis results were confirmed by generation of independent pathway signatures and application to additional datasets. RESULTS: Renal tumors isolated from individuals with BHDS showed distinct gene expression and cytogenetic characteristics from sporadic renal oncocytoma and chromophobe RCC. The most prominent molecular feature of BHDS-derived kidney tumors was high expression of mitochondria-and oxidative phosphorylation (OXPHOS)-associated genes. This mitochondria expression phenotype was associated with deregulation of the PGC-1α-TFAM signaling axis. Loss of FLCN expression across various tumor types is also associated with increased nuclear mitochondrial gene expression. CONCLUSIONS: Our results support a genetic distinction between BHDS-associated tumors and other renal neoplasias. In addition, deregulation of the PGC-1α-TFAM signaling axis is most pronounced in renal tumors that harbor FLCN mutations and in tumors from other organs that have relatively low expression of FLCN. These results are consistent with the recently discovered interaction between FLCN and AMPK and support a model in which FLCN is a regulator of mitochondrial function.

Molecular cytogenetic characterization shows higher genetic homogeneity in conventional renal cell carcinoma compared to other kidney cancers.

In this study seven primary kidney tumors out of 13 were cytogenetically characterized by comparative genomic hybridization (CGH) on the surgical specimens as well as by spectral karyotyping (SKY) analysis after short-term culturing. In two of the seven cases only a normal karyotype was identified. Non-clonal aberrations were observed in four of the seven cases. Overall numerical alterations were more frequent than structural changes. The two structural alterations identified constituted of a deletion of the short arm of chromosome 3 in a conventional renal cell carcinoma (RCC), and a ring chromosome derived from chromosome 8 in a papillary RCC. By CGH gains of copy number were revealed on chromosomes 3, 5, 7, 8q, and 20, while the losses encompassed 3p and 17p. In the papillary RCCs only gains were found. Comparison between SKY and CGH data suggests that the conventional RCCs are genetically more homogeneous than the other types of kidney cancer. In the two papillary RCCs, trisomies of chromosomes 7 and 17 were typical findings. In the transitional cell carcinoma different findings by CGH and SKY would suggest that these tumors constitute a heterogeneous population of tumor cells which could represent different steps of somatic evolution of tumors.

Loss of 14q31-q32.2 in renal cell carcinoma is associated with high malignancy grade and poor survival.

The present study was undertaken to further approach the importance of 14q deletions in renal cell carcinoma (RCC) development. The initial screening using 2 RFLP markers from distal 14q identified loss of heterozygosity (LOH) in 17 of 45 informative cases (38%). In addition, in 37 patients with primary RCCs, it was shown that cases with LOH at D14S1 had significantly shorter survival as compared to cases with-out LOH (p<0.005). Subsequently, 19 primary tumors and 6 metastases were genotyped for 20 polymorphic markers and the findings were evaluated in relation to the clinical characteristics of the primary tumor and the survival during follow-up. Overall LOH was identified in 11 of the primary tumors (58%) and 4 of the metastases (66%). In metastases as well as in primary tumors the highest frequency of LOH was detected with markers from the distal part of the chromosome i.e., 14q32. Five minimal regions of overlapping deletions were identified, three of which (II, IV and V) were defined from the primary RCCs. From centromere to telomere these include region I proximal of D14S259, region II between D14S255 and D14S588, region III in the D14S61-D14S617 interval, region IV between D14S617 and D14S260, and region V telomeric of D14S1007. For the primary tumors, losses in regions IV and V were each significantly associated with high tumor grade (i.e., grade 3; p<0.05). Furthermore, LOH within region IV was also associated with a significantly shorter survival (p=0.02). In conclusion, the high frequency of distal 14q LOH supports the relevance of this alteration for the development of RCC.

Gene expression profiling identifies clinically relevant subtypes of prostate cancer.

Prostate cancer, a leading cause of cancer death, displays a broad range of clinical behavior from relatively indolent to aggressive metastatic disease. To explore potential molecular variation underlying this clinical heterogeneity, we profiled gene expression in 62 primary prostate tumors, as well as 41 normal prostate specimens and nine lymph node metastases, using cDNA microarrays containing approximately 26,000 genes. Unsupervised hierarchical clustering readily distinguished tumors from normal samples, and further identified three subclasses of prostate tumors based on distinct patterns of gene expression. High-grade and advanced stage tumors, as well as tumors associated with recurrence, were disproportionately represented among two of the three subtypes, one of which also included most lymph node metastases. To further characterize the clinical relevance of tumor subtypes, we evaluated as surrogate markers two genes differentially expressed among tumor subgroups by using immunohistochemistry on tissue microarrays representing an independent set of 225 prostate tumors. Positive staining for MUC1, a gene highly expressed in the subgroups with "aggressive" clinicopathological features, was associated with an elevated risk of recurrence (P = 0.003), whereas strong staining for AZGP1, a gene highly expressed in the other subgroup, was associated with a decreased risk of recurrence (P = 0.0008). In multivariate analysis, MUC1 and AZGP1 staining were strong predictors of tumor recurrence independent of tumor grade, stage, and preoperative prostate-specific antigen levels. Our results suggest that prostate tumors can be usefully classified according to their gene expression patterns, and these tumor subtypes may provide a basis for improved prognostication and treatment stratification.

Difference between Swedish and Japanese men in the association between AR CAG repeats and prostate cancer suggesting a susceptibility-modifying locus overlapping the androgen receptor gene.

Previous studies have shown that short CAG repeats in the androgen receptor (AR) gene are associated with increased risk of prostate cancer. It is unclear if this association is due to linkage disequilibrium with a susceptibility locus or directly linked to the possible functional impact of the length of the CAG repeats. In this study, the number of the AR CAG repeats was determined in prostate cancer patients, benign prostatic hyperplasia (BPH) patients, and controls in both Swedish and Japanese men. Prostate cancer patients included 59 Swedish hereditary, 59 Swedish sporadic and 33 Japanese sporadic cases. BPH patients included 38 Swedish and 33 Japanese cases. Controls included 98 Swedish healthy men and 43 Japanese men without either prostate cancer or BPH. No significant difference in AR CAG repeats was found in comparison between BPH patients and controls. In contrast, both Swedish hereditary and sporadic prostate cancer patients had shorter AR CAG repeats than Swedish controls, but Japanese prostate cancer patients had longer repeats than controls. These differences between the two populations in the association of prostate cancer and the AR CAG repeats may suggest that the AR CAG repeats are in linkage disequilibrium with a prostate cancer susceptibility locus localized in a small region flanking or overlapping the AR gene at Xq12.1.

Clinical significance of chromosome 8p, 10q, and 16q deletions in prostate cancer.

BACKGROUND: We lack simple and reliable diagnostic tools to predict pathological staging as well as further progression of prostate cancer in individual cases. METHODS: We studied deletions on 8p (8p22 and 8p23-pter), 10q (10q24-qter), and 16q (16q24) by fluorescence in situ hybridization in 53 specimens from patients with prostate cancer, and compared the status of these deletions with various clinical parameters. Forty-five cases were further evaluated regarding disease progression with a median follow-up period of 62 months. RESULTS: The overall frequencies of deletions for 8p, 10q, and 16q were 74, 55, and 55%, respectively. The frequency of 8p and 16q deletions increased significantly in parallel with tumor grade (P < 0.01 and < 0.05, respectively), while that of 10q deletions did not. Patients whose tumors showed 8p22 deletions had a significantly higher frequency in pT3 or metastatic tumors than in pT2 tumors. Patients whose tumors showed both 8p22 and 16q24 deletions had a significantly higher frequency of nodal metastases than non-metastases. A Cox hazard proportional model revealed 8p22 deletion to be the strongest parameter predictive of disease progression (hazard ratio = 6.624; P = 0.0001). CONCLUSION: Estimation of 8p22 and 16q24 deletions may serve as a genetic diagnosis for predicting pathological staging as well as disease progression in prostate cancer.