Martina Kluth

CHD1 is a 5q21 tumor suppressor required for ERG rearrangement in prostate cancer

Deletions involving the chromosomal band 5q21 are among the most frequent alterations in prostate cancer. Using single-nucleotide polymorphism (SNP) arrays, we mapped a 1.3 megabase minimally deleted region including only the repulsive guidance molecule B (RGMB) and chromodomain helicase DNA-binding protein 1 (CHD1) genes. Functional analyses showed that CHD1 is an essential tumor suppressor. FISH analysis of 2,093 prostate cancers revealed a strong association between CHD1 deletion, prostate-specific antigen (PSA) biochemical failure (P = 0.0038), and absence of ERG fusion (P < 0.0001). We found that inactivation of CHD1 in vitro prevents formation of ERG rearrangements due to impairment of androgen receptor (AR)-dependent transcription, a prerequisite for ERG translocation. CHD1 is required for efficient recruitment of AR to responsive promoters and regulates expression of known AR-responsive tumor suppressor genes, including NKX3-1, FOXO1, and PPARγ. Our study establishes CHD1 as the 5q21 tumor suppressor gene in prostate cancer and shows a key role of this chromatin remodeling factor in prostate cancer biology.

Genomic deletion of MAP3K7 at 6q12-22 is associated with early PSA recurrence in prostate cancer and absence of TMPRSS2: ERG fusions

6q12-22 is the second most commonly deleted genomic region in prostate cancer. Mapping studies have described a minimally deleted area at 6q15, containing MAP3K7/TAK1, which was recently shown to have tumor suppressive properties. To determine prevalence and clinical significance of MAP3K7 alterations in prostate cancer, a tissue microarray containing 4699 prostate cancer samples was analyzed by fluorescence in situ hybridization. Heterozygous MAP3K7 deletions were found in 18.48% of 2289 interpretable prostate cancers. MAP3K7 deletions were significantly associated with advanced tumor stage (P<0.0001), high Gleason grade (P<0.0001), lymph node metastasis (P<0.0108) and early biochemical recurrence (P<0.0001). MAP3K7 alterations were typically limited to the loss of one allele as homozygous deletions were virtually absent and sequencing analyses revealed no evidence for MAP3K7 mutations in 15 deleted and in 14 non-deleted cancers. There was a striking inverse association of MAP3K7 deletions and TMPRSS2:ERG fusion status with 26.7% 6q deletions in 1125 ERG-negative and 11.1% 6q deletions in 1198 ERG-positive cancers (P<0.0001). However, the strong prognostic role of 6q deletions was retained in both ERG-positive and ERG-negative cancers (P<0.0001 each). In summary, our study identifies MAP3K7 deletion as a prominent feature in ERG-negative prostate cancer with strong association to tumor aggressiveness. MAP3K7 alterations are typically limited to one allele of the gene. Together with the demonstrated tumor suppressive function in cell line experiments and lacking evidence for inactivation through hypermethylation, these results indicate MAP3K7 as a gene for which haploinsufficency is substantially tumorigenic.

Marked heterogeneity of ERG expression in large primary prostate cancers

Approximately 50% of prostate cancers are characterized by TMPRSS2 (transmembrane protease serine 2)-ERG (avian v-ets erythroblastosis virus E26 oncogene homolog) gene fusions resulting in an androgen-regulated overexpression of the transcription factor ERG. Some studies have suggested prognostic or predictive relevance of ERG status in prostate cancer. Such concepts could be impaired by extensive ERG heterogeneity in analyzed tumors. The aim of this study was to analyze the extent of heterogeneity for TMPRSS2-ERG fusion in prostate cancer. To enable large-scale studies on the extent of heterogeneity of biomarkers in prostate cancer, a heterogeneity tissue microarray containing samples from 10 different tumor blocks of 190 large prostate cancers selected from a consecutive series of 480 radical prostatectomies was developed. ERG expression was analyzed by immunohistochemistry. Positive ERG immunostaining was found in arrayed cancer-containing samples from 103 of the 178 analyzable patients (58%). ERG immunostaining was homogeneously positive in 29 prostate cancers (16%), whereas heterogeneous ERG positivity was seen in 74 cancers (42%). ERG heterogeneity was within one tumor focus (intrafocal heterogeneity) in 69 cases (93% of heterogeneous cases) and between different tumor foci (interfocal heterogeneity) in 5 cases (7%). Marked intrafocal heterogeneity challenges the concept of TMPRSS2-ERG fusion always representing an early step in prostate cancer development. Marked heterogeneity also compromises the concept of analyzing ERG status for treatment decisions in diagnostic needle core biopsies.

Clinical significance of different types of p53 gene alteration in surgically treated prostate cancer

Despite a multitude of p53 immunohistochemistry (IHC) studies, data on the combined effect of nuclear p53 protein accumulation and TP53 genomic inactivation are lacking for prostate cancer. A tissue microarray including 11,152 prostate cancer samples was analyzed by p53 IHC and fluorescence in situ hybridization. Nuclear p53 accumulation was found in 10.1% of patients including 1.4% with high‐level and 8.7% with low‐level immunostaining. TP53 sequencing revealed that 17 of 22 (77%) cases with high‐level p53 immunostaining, but only 3% (1 of 31) low‐level p53 cases carried putative dominant‐negative mutations. TP53 deletions occurred in 14.8% of cancers. Both deletions and protein accumulation were linked to unfavorable tumor phenotype and prostate specific antigen (PSA) recurrence (p < 0.0001 each). The combination of both methods revealed subgroups with remarkable differences in their clinical course. Tumors with either TP53 deletion (14%) or low‐level p53 positivity (8.7%) had identical risks of PSA recurrence, which were markedly higher than in cancers without p53 alterations (p < 0.0001). Tumors with both p53 deletion and low‐level p53 positivity (1.5%) had a worse prognosis than patients with only one of these alterations (p < 0.0001). Tumors with strong p53 immunostaining or homozygous inactivation through deletion of one allele and disrupting translocation involving the second allele had the worst outcome, independent from clinical and pathological parameters. These data demonstrate a differential clinical impact of various TP53 alterations in prostate cancer. Strong p53 immunostaining—most likely accompanying dominant negative or oncogenic p53 mutation—has independent prognostic relevance and may thus represent a clinical useful molecular feature of prostate cancer.

SPINK1 expression is tightly linked to 6q15- and 5q21-deleted ERG-fusion negative prostate cancers but unrelated to PSA recurrence.

The serine peptidase inhibitor, Kazal type 1 (SPINK1) has been suggested to define an aggressive molecular subtype of ERG‐fusion negative prostate cancer. It was the aim of this study to further study the clinical relevance of SPINK1 expression and its relationship with other key genomic alterations of prostate cancer.

High level of Ets-related gene expression has high specificity for prostate cancer: a tissue microarray study of 11 483 cancers

Minner S, Luebke A M, Kluth M, Bokemeyer C, Jänicke F, Izbicki J, Schlomm T, Sauter G & Wilczak W 
(2012) Histopathology 61, 445–453

High nuclear karyopherin α 2 expression is a strong and independent predictor of biochemical recurrence in prostate cancer patients treated by radical prostatectomy

Increased levels of karyopherin α2 (KPNA2) expression have been described to be linked to poor prognosis in a variety of malignancies. This study was undertaken to evaluate the clinical impact of KPNA2 expression and its association with key genomic alterations in prostate cancers. A tissue microarray containing samples from 11 152 prostate cancers was analyzed for KPNA2 expression by immunohistochemistry. Results were compared with oncological follow-up data and genomic alterations such as TMPRSS2-ERG fusions and deletions of PTEN, 5q21, 6q15 or 3p13. KPNA2 expression was absent or weak in benign prostatic glands and was found to be in weak, moderate or strong intensities in 68.4% of 7964 interpretable prostate cancers. KPNA2 positivity was significantly linked to the presence of ERG rearrangement (P<0.0001). In ERG-negative and -positive prostate cancers, KPNA2 immunostaining was significantly associated with advanced pathological tumor stage (pT3b/pT4), high Gleason grade and early biochemical recurrence (P<0.0001 each). Multivariate analysis including all established prognostic criteria available after surgery revealed that the prognostic role of KPNA2 (P=0.001) was independent of high Gleason grade, advanced pathological tumor stage, high preoperative prostate-specific antigen level and positive surgical margin status (P<0.0001 each). The comparison of KPNA2 expression with deletions of PTEN, 5q21, 6q15 and 3p13 in ERG-positive and -negative cancers revealed a strong link to PTEN deletions in both subgroups (P<0.0001). In conclusion, the strong independent prognostic impact of KPNA2 expression raises the possibility that measurement of KPNA2 expression alone or in combination with other molecular parameters might possibly result in clinically useful information. The data also emphasize a critical role of the functionality of the nuclear import machinery for prostate cancer biology.

Cytoplasmic accumulation of Sequestosome 1 (p62) is a predictor of biochemical recurrence, rapid tumor cell proliferation and genomic instability in prostate cancer

Purpose: Sequestosome 1 (p62) is a multifunctional adapter protein accumulating in autophagy-defective cells. Experimental Design: To evaluate the clinical impact and relationship with key genomic alterations in prostate cancer, p62 protein levels were analyzed by immunohistochemistry on a tissue microarray containing 12,427 prostate cancers. Data on ERG status and deletions of PTEN, 3p13, 5q21, and 6q15 were available from earlier studies. Results: p62 immunostaining was absent in benign prostatic glands but present in 73% of 7,822 interpretable prostate cancers. Strong cytoplasmic p62 staining was tightly linked to high Gleason grade, advanced pathologic tumor (pT) stage, positive nodal status, positive resection margin, and early PSA recurrence (P < 0.0001 each). Increased levels of p62 were significantly linked to TMPRSS2–ERG fusions, both by FISH and immunohistochemical analysis (P < 0.0001 each). For example, moderate or strong p62 immunostaining was seen in 28.5% of cancers with TMPRSS2–ERG fusion detected by FISH and in 23.1% of cancers without such rearrangements (P < 0.0001). Strong p62 staining was significantly linked to the presence of all tested deletions, including PTEN (P < 0.0001), 6q15 (P < 0.0001), 5q21 (P = 0.0002), 3p13 (P = 0.0088), and 6q15 (P < 0.0001), suggesting a link between p62 accumulation and loss of genomic stability. The prognostic role of p62 protein accumulation was striking and independent of Gleason grade, pT stage, pN stage, surgical margin status, and preoperative PSA, regardless of whether preoperative or postoperative parameters were used for modeling. Conclusions: Our study identifies cytoplasmic accumulation of p62 as a strong predictor of an adverse prognostic behavior of prostate cancer independently from established clinicopathologic findings. Clin Cancer Res; 21(15); 3471–9. ©2015 AACR.

PTEN deletions are related to disease progression and unfavourable prognosis in early bladder cancer

This study aimed to determine the prevalence and clinical significance of deletions of the tumour suppressor gene PTEN in bladder cancer.

HDAC1 overexpression independently predicts biochemical recurrence and is associated with rapid tumor cell proliferation and genomic instability in prostate cancer.

Histone deacetylases (HDACs) play an important role in tumor development and progression by modifying histone and non-histone proteins. In the current study we analyzed prevalence and prognostic impact of HDAC1 in prostate cancer. HDAC1 expression was analyzed by immunohistochemistry on a tissue microarray containing more than 12,400 prostate cancer specimens. Results were compared to tumor phenotype, biochemical recurrence, and molecular subtypes defined by ERG status as well as genomic deletions of 3p, 5q, 6q and PTEN. HDAC1 immunostaining was detectable in 75.4% of 9744 interpretable cancers and considered strong in 15.4%, moderate in 39.4% and weak in 20.7% of cases. High HDAC1 expression was associated with high Gleason grade (p<0.0001), advanced pathological tumor stage (p<0.0001), positive nodal status (p=0.0010), elevated preoperative PSA-level (p=0.0127), early PSA recurrence (p<0.0001) and increased cell proliferation (p<0.0001). Moreover, high-level HDAC1 staining was associated with TMPRSS2:ERG rearrangement and ERG expression in prostate cancers (p<0.0001) and was linked to deletions of PTEN (p<0.0001), 6q (p<0.0001) and 5q (p=0.0028) in ERG-negative cancers. The prognostic impact of HDAC1 was independent of established clinicopathological parameters and was mostly driven by ERG-negative cancers as revealed by subgroup analyses. HDAC1 has strong prognostic impact in prostate cancer and might contribute to the development of a fraction of genetically instable and particularly aggressive prostate cancers. HDAC1 measurement might therefore be of clinical value for risk stratification of prostate cancer and should be further evaluated in this regard.