Novel, gross chromosomal alterations involving PTEN cooperate with allelic loss in prostate cancer.

There is increasing evidence that multiple chromosomal rearrangements occur in prostate cancer. PTEN loss is considered to be a key event in prostate carcinogenesis but the mechanisms of loss remain to be fully elucidated. We hypothesised that gross rearrangements may exist that cause disruption of the PTEN gene in the absence of genomic deletion. We therefore designed a novel fluorescence in situ hybridisation (FISH) assay with probes overlying regions 3' and 5' of PTEN and a third probe overlying the gene. We aimed to identify both genomic deletions and gross rearrangements of PTEN that would be overlooked by previously reported single-probe FISH assays. We proceeded to evaluate a tissue microarray with radical prostatectomy and trans-urethral resection of the prostate specimens from 187 patients. We identified PTEN genomic loss in 45/150 (30%) radical prostatectomy patients and 16/37 (43%) trans-urethral resection of the prostate patients. Importantly, our assay detected novel chromosomal alterations in the PTEN gene (characterised by splitting of FISH signals) in 13 tumours (6.9% of all prostate cancers; 21% of PTEN-lost cancers). All PTEN-rearranged tumours had genomic loss at the other allele and had no expression of PTEN by immunohistochemistry. PTEN-rearranged tumours were significantly more likely to have an underlying ERG rearrangement. Our assay differentiated loss of the probe overlying PTEN in isolation or in combination with either one of or both the probes overlying the 3' and 5' regions. This gave an indication of the size of genomic loss and we observed considerable inter-tumoural heterogeneity in the extent of genomic loss in PTEN-lost tumours. In summary, gross rearrangements of the PTEN locus occur in prostate cancer and can be detected by a 'break-apart' FISH assay. This observation could explain the absence of PTEN protein expression in a subgroup of tumours previously classified as having heterozygous genomic loss using single-probe traditional FISH assays.

Expression of Bcl-2, p53, and MDM2 in localized prostate cancer with respect to the outcome of radical radiotherapy dose escalation.

PURPOSE: Established prognostic factors in localized prostate cancer explain only a moderate proportion of variation in outcome. We analyzed tumor expression of apoptotic markers with respect to outcome in men with localized prostate cancer in two randomized controlled trials of radiotherapy dose escalation. METHODS AND MATERIALS: Between 1995 and 2001, 308 patients with localized prostate cancer received neoadjuvant androgen deprivation and radical radiotherapy at our institution in one of two dose-escalation trials. The biopsy specimens in 201 cases were used to make a biopsy tissue microarray. We evaluated tumor expression of Bcl-2, p53, and MDM2 by immunohistochemistry with respect to outcome. RESULTS: Median follow-up was 7 years, and 5-year freedom from biochemical failure (FFBF) was 70.4% (95% CI, 63.5-76.3%). On univariate analysis, expression of Bcl-2 (p < 0.001) and p53 (p = 0.017), but not MDM2 (p = 0.224), was significantly associated with FFBF. Expression of Bcl-2 remained significantly associated with FFBF (p = 0.001) on multivariate analysis, independently of T stage, Gleason score, initial prostate-specific antigen level, and radiotherapy dose. Seven-year biochemical control was 61% vs. 41% (p = 0.0122) for 74 Gy vs. 64 Gy, respectively, among patients with Bcl-2-positive tumors and 87% vs. 81% (p = 0.423) for 74 Gy vs. 64 Gy, respectively, among patients with Bcl-2-negative tumors. There was no statistically significant interaction between dose and Bcl-2 expression. CONCLUSIONS: Bcl-2 expression was a significant, independent determinant of biochemical control after neoadjuvant androgen deprivation and radical radiotherapy for prostate cancer. These data generate the hypothesis that Bcl-2 expression could be used to inform the choice of radiotherapy dose in individual patients.

Intrinsic markers of tumour hypoxia and angiogenesis in localised prostate cancer and outcome of radical treatment: a retrospective analysis of two randomised radiotherapy trials and one surgical cohort study.

BACKGROUND: Expression of intrinsic markers of tumour hypoxia and angiogenesis are important predictors of radiotherapeutic, and possibly surgical, outcome in several cancers. Extent of tumour hypoxia in localised prostate cancer is comparable to that in other cancers, but few data exist on the association of extent of tumour hypoxia with treatment outcome. We aimed to study the predictive value of intrinsic markers of tumour hypoxia and angiogenesis in localised prostate cancer, both in patients treated with radiotherapy and in those treated surgically. METHODS: We applied a new, needle biopsy tissue microarray (TMA) technique to study diagnostic samples from men with localised, previously untreated prostate cancer treated in two randomised controlled trials of radiotherapy-dose escalation. Multivariate analysis by Cox proportional hazards was done to assess the association between clinical outcome, in terms of biochemical control, and immunohistochemical staining of hypoxia inducible factor-1 alpha (HIF-1 alpha), vascular endothelial growth factor (VEGF), and osteopontin expression. The analysis was repeated on an independent series of men with localised, previously untreated prostate cancer treated by radical prostatectomy. The main outcome was time to biochemical (ie, prostate-specific antigen [PSA]) failure. FINDINGS: Between Oct 12, 1995, and Feb 5, 2002, 308 patients were identified from two prospective, randomised trials at the Royal Marsden Hospital, London and Sutton, UK, for the radiotherapy cohort and diagnostic biopsies were available for 201 of these patients. Between June 6, 1995, and Nov 4, 2005, 329 patients were identified from the Aarhus University Hospital, Skejby, Denmark, for the prostatectomy cohort; of these, 40 patients were excluded because the tumour was too small to sample (19 patients), because the paraffin block was too thin (19 patients), or because the blocks were missing (two patients), leaving 289 patients for analysis. For patients treated with radiotherapy, increased staining for VEGF (p=0.008) and HIF-1 alpha (p=0.02) expression, but not increased osteopontin expression (p=0.978), were significant predictors of a shorter time to biochemical failure on multivariate analysis, independent of clinical tumour stage, Gleason score, serum PSA concentration, and dose of radiotherapy. For patients treated with surgery, increased staining for VEGF (p<0.0001) and HIF-1 alpha (p<0.0001) expression, and increased osteopontin expression (p=0.0005) were each significantly associated with a shorter time to biochemical failure on multivariate analysis, independent of pathological tumour stage, Gleason score, serum PSA concentration, and margin status. INTERPRETATION: To our knowledge, this is the largest study of intrinsic markers of hypoxia and angiogenesis in relation to the outcome of radical treatment of localised prostate cancer. Increased expression of VEGF, HIF-1 alpha, and, for patients treated with surgery, osteopontin, identifies patients at high risk of biochemical failure who would be suitable for enrolment into trials of treatment intensification.