Predicting biochemical recurrence after radical prostatectomy for patients with organ-confined disease using p27 expression

Regulation of p27 (Kip1) by Ubiquitin E3 Ligase RNF6

The cyclin-dependent kinase inhibitor p27 (Kip1) is an important regulator of the G1/S checkpoint. It is degraded by the SCF-SKP2 complex in late G1 thereby allowing cells to progress to the S phase. Here we investigated the role of the E3 ubiquitin ligase RNF6 (Ring Finger Protein 6) in cell cycle progression in prostate cancer cells. Our data demonstrate that RNF6 can promote cell cycle progression by reducing the levels of p27. Knockdown of RNF6 led to an increase in the stability of p27 and to the arrest of cells in the G1 phase. RNF6 interacted with p27 via its KIL domain and this interaction was found to be phosphorylation independent. RNF6 enhanced ubiquitination and subsequent degradation of p27 in the early G0/G1 phase of the cell cycle. Knockdown of RNF6 expression by short hairpin RNA led to inhibition of the CDK2/Cyclin E complex thereby reducing phosphorylation of Retinoblastoma protein (Rb) and to a subsequent decrease in cell cycle progression and proliferation. Our data suggest that RNF6 acts as a negative regulator for p27^kip1 leading to its proteasome-dependent degradation in the early G0/G1 phase of the cell cycle.

Upregulation of miR-130b Contributes to Risk of Poor Prognosis and Racial Disparity in African-American Prostate Cancer

Prostate cancer incidence and mortality rates are higher in African-American (AA) than in European-American (EA) men. The main objective of this study was to elucidate the role of miR-130b as a contributor to prostate cancer health disparity in AA patients. We also determined whether miR-130b is a prognostic biomarker and a new therapeutic candidate for AA prostate cancer. A comprehensive approach of using cell lines, tissue samples, and the TCGA database was employed. We performed a series of functional assays such as cell proliferation, migration, invasion, RT2-PCR array, qRT-PCR, cell cycle, luciferase reporter, immunoblot, and IHC. Various statistical approaches such as Kaplan-Meier, uni-, and multivariate analyses were utilized to determine the clinical significance of miR-130b. Our results showed that elevated levels of miR-130b correlated with race disparity and PSA levels/failure and acted as an independent prognostic biomarker for AA patients. Two tumor suppressor genes, CDKN1B and FHIT, were validated as direct functional targets of miR-130b. We also found race-specific cell-cycle pathway activation in AA patients with prostate cancer. Functionally, miR-130b inhibition reduced cell proliferation, colony formation, migration/invasion, and induced cell-cycle arrest. Inhibition of miR-130b modulated critical prostate cancer-related biological pathways in AA compared with EA prostate cancer patients. In conclusion, attenuation of miR-130b expression has tumor suppressor effects in AA prostate cancer. miR-130b is a significant contributor to prostate cancer racial disparity as its overexpression is a risk factor for poor prognosis in AA patients with prostate cancer. Thus, regulation of miR-130b may provide a novel therapeutic approach for the management of prostate cancer in AA patients.

The AR dependent cell cycle: mechanisms and cancer relevance

Prostate cancer cells are exquisitely dependent on androgen receptor (AR) activity for proliferation and survival. As these functions are critical targets of therapeutic intervention for human disease, it is imperative to delineate the mechanisms by which AR engages the cell cycle engine. More than a decade of research has revealed that elegant intercommunication between AR and the cell cycle machinery governs receptor-dependent cellular proliferation, and that perturbations in this process occur frequently in human disease. Here, AR-cell cycle interplay and associated cancer relevance will be reviewed.

Using molecular markers to help predict who will fail after radical prostatectomy

Recent phase III trial data clearly demonstrate that adjuvant therapy can reduce recurrence and increase survival after prostatectomy for prostate cancer. There is great interest in being able to accurately predict who is at risk of failure to avoid treating those who may not benefit. The standard markers consisting of prostate specific antigen (PSA), Gleason score, and pathological stage are not very specific, so there is an unmet need for other markers to aid in prognostic stratification. Numerous studies have been conducted with various markers and more recently gene signatures, but it is unclear whether any of them are really useful. We conducted a comprehensive review of the literature to determine the current status of molecular markers in predicting outcome after radical prostatectomy.

Subcellular localization of p27 and prostate cancer recurrence: automated digital microscopy analysis of tissue microarrays

Previous investigations have linked decreased nuclear expression of the cell cycle inhibitor p27 with poor outcome in prostate cancer. However, these reports are inconsistent regarding the magnitude of that association and its independence from other predictors. Moreover, cytoplasmic translocation of p27 has been proposed as a negative prognostic sign. Given the cost and accuracy limitations of manual scoring, particularly of tissue microarrays, we determined if laser-based fluorescence microscopy could provide automated analysis of p27 in both nuclear and cytoplasmic locations and, thus, clarify its significance as a prognostic biomarker. We constructed tissue microarrays covering 202 recurrent cases (rising prostate-specific antigen) and 202 matched controls without recurrence. Quadruplicate tumor samples encompassed 5 slides and 1616 cancer histospots. Cases and controls matched on age, Gleason grade, stage, and hospital. We immunolabeled epithelial cytoplasm with Alexafluor 647, p27 with Alexafluor 488, and nuclei with 4c6-diamidino-2-phenylindole·2HCl. Slides were scanned on an iCys laser scanning cytometer (CompuCyte Corp, Cambridge, MA). Nuclear crowding required a stereological approach--random arrays of circles (phantoms) were layered on images and the content of each phantom was analyzed in scatter plots. Both nuclear and cytoplasmic p27 were significantly lower in cases versus controls (P = .014 and P = .004, respectively). Regression models controlling for matching variables plus prostate-specific antigen showed strong linear trends for increased risk of recurrence with lower p27 in both nucleus and cytoplasm (highest versus lowest quartile; odds ratio, 0.35; P = .006). Manual scoring identified an inverse association between p27 expression and tumor grade but no independent association with recurrence. In conclusion, we developed an automated method for subcellular scoring of p27 without the need to segment individual cells. Our method identified a strong relationship, independent of tumor grade, stage, and prostate-specific antigen, between p27 expression--regardless of subcellular location--and prostate cancer recurrence. This relationship was not observed with manual scoring.

A pharmacodynamic study of rapamycin in men with intermediate- to high-risk localized prostate cancer

PURPOSE

Given discrepancies between preclinical and clinical observations of mammalian target of rapamycin (mTOR) inhibition in prostate cancer, we sought to determine the pharmacodynamic effects of the mTOR/TORC1 inhibitor rapamycin in men with intermediate- to high-risk prostate cancer undergoing radical prostatectomy.

EXPERIMENTAL DESIGN

Rapamycin was given at 3 or 6 mg orally for 14 days before radical prostatectomy in men with multifocal Gleason sum > or =7 prostate cancer; 10 untreated control subjects were included. The primary outcome was inhibition of phosphorylation of ribosomal S6 in posttreatment radical prostatectomy versus pretreatment biopsy tumor tissue, evaluated using a Simon two-stage design for pharmacodynamic efficacy.

RESULTS

Thirty-two subjects were accrued: 20 at 3 mg, 2 at 6 mg, and 10 controls. No dose-limiting toxicities were observed at 3 mg; however, two of two men enrolled at 6 mg experienced dose-limiting toxicities including thrombocytopenia and fever with grade 3 stomatitis. Adverse events observed at 3 mg included stomatitis, rash, ileus, and neutropenia. Pharmacodynamic studies showed tumor S6 phosphorylation inhibition in 50% of 10 evaluable rapamycin-treated men with sufficient paired tissue [median 58% inhibition (P = 0.049) versus 2% inhibition in controls (P = 0.75)] with no significant effect on AKT activity. We observed no change in Ki-67 or caspase-3 cleavage but noted a reduction in cytoplasmic p27 staining with increased nuclear localization with rapamycin treatment. Prostate tissue rapamycin concentrations were 3- to 4-fold higher than blood.

CONCLUSIONS

At 3 mg daily, rapamycin successfully and safely inhibited prostate cancer S6 phosphorylation and achieved relatively high prostate tissue concentrations. No effect on AKT phosphorylation, tumor proliferation, or apoptosis was observed.

Evaluating localized prostate cancer and identifying candidates for focal therapy

Can focal therapy successfully control prostate cancer? Also, if so, which patients should be considered eligible? With limited data available from relatively few patients, these questions are difficult to answer. At this writing, the most likely candidates for focal therapy are patients with low-risk, small-volume tumors, located in 1 region or sector of the prostate, who would benefit from early intervention. The difficulty lies in reliably identifying these men. The larger number of cores obtained in each needle biopsy session has increased both the detection of prostate cancer and the potential risk of overtreating many patients whose cancers pose very little risk to life or health. Urologists typically perform at least a 12-core template biopsy. Although the debate continues about the optimal template, laterally and peripherally directed biopsies have been shown to improve the diagnostic yield. However, as many as 25% of tumors arise anteriorly and can be missed with peripherally directed techniques. Prostate cancer tends to be multifocal, even in its earliest stages. However, the secondary cancers are usually smaller and less aggressive than the index cancer. They appear similar to the incidental cancers found in cystoprostatectomy specimens and appear to have little effect on prognosis in surgical series. When a single focus of cancer is found in 1 core, physicians rightly suspect that more foci of cancer are present in the prostate. Assessing the risk in these patients is challenging when determined by the biopsy data alone. To predict the presence of a very low-risk or "indolent" cancer, nomograms have been developed to incorporate clinical stage, Gleason grade, prostate-specific antigen levels, and prostate volume, along with the quantitative analysis of the biopsy results. Transperineal "mapping" or "saturation" biopsies have been advocated to detect cancers missed or underestimated by previous transrectal biopsies. This approach could provide the accurate staging, grading, and tumor localization needed for a focal therapy program. Nevertheless, for men with minimal cancer who are amenable to active surveillance or focal therapy, consensus about the most accurate biopsy strategy has not yet been reached. Imaging, particularly magnetic resonance imaging and magnetic resonance spectroscopic imaging, has been used to assess men with early-stage prostate cancer. Large-volume cancers can be seen reasonably well, but small lesions have been difficult to detect reliably or measure accurately. Factors such as voxel resolution, organ movement, biopsy artifact, and benign changes have limited the consistent estimation of the quantitative tumor volume. Nevertheless, magnetic resonance imaging and magnetic resonance spectroscopic imaging can aid in evaluating patients with prostate cancer being considered for focal therapy by providing additional evidence that the patient does not harbor an otherwise undetected high-risk, aggressive cancer. In some cases, imaging can usefully identify the location of even a limited-sized index cancer. When imaging findings are substantiated by mapping biopsy results, confidence in the accurate characterization of the cancer is enhanced. Correlating the imaging results with tissue changes during and after treatment can be of use in monitoring the ablative effects in the prostate and in assessing for tumor recurrence. More work is necessary before staging studies can uniformly characterize a prostate cancer before therapy, much less reliably identify and locate small-volume cancer within the prostate. However, exploring the role of focal ablation as a therapeutic option for selected men with low-risk, clinically localized, prostate cancer need not await the emergence of perfectly accurate staging studies, any more than the application of radical surgery or radiotherapy have. Modern biopsy strategies, combined with optimal imaging and nomograms to estimate the pathologic stage and risk, taken together, provide a sound basis for the selection of appropriate patients for entry into prospective clinical trials of focal therapy.

The Cdk inhibitor p27 in human cancer: prognostic potential and relevance to anticancer therapy

The cyclin-dependent kinase (Cdk) inhibitor p27 (also known as KIP1) regulates cell proliferation, cell motility and apoptosis. Interestingly, the protein can exert both positive and negative functions on these processes. Diverse post-translational modifications determine the physiological role of p27. Phosphorylation regulates p27 binding to and inhibition of cyclin-Cdk complexes, its localization and its ubiquitin-mediated proteolysis. In cancers, p27 is inactivated through impaired synthesis, accelerated degradation and by mislocalization. Moreover, studies in several tumour types indicate that p27 expression levels have both prognostic and therapeutic implications.

PSA outcome following radical prostatectomy for patients with localized prostate cancer stratified by prostatectomy findings and the preoperative PSA level

PURPOSE

Algorithms have been developed to predict time to biochemical failure (BF) following radical prostatectomy (RP) for patients with clinically localized prostate cancer. The purpose of this study was to validate an algorithm based on prostatectomy findings and to evaluate whether the preoperative serum prostate specific antigen (PSA) enhances the predictive ability of the algorithm.

MATERIALS AND METHODS

Between 1988 and 2002, 2417 patients underwent RP for clinically localized prostate cancer at one of 2 large university hospitals. Patients were retrospectively stratified into 4 risk groups based upon prostatectomy grade, stage, and margin status, and were then dichotomized by the preoperative PSA level (cut point 10 ng/mL). Cox regression multivariable analyses were performed to evaluate the ability of the risk group and preoperative PSA level to predict time to BF (PSA more than 0.2 ng/mL) following RP.

RESULTS

The preoperative PSA level (P < 0.0001) and risk group (P < 0.0001) were significant predictors of time to BF following RP. Estimates of the BF rates 7 years following RP were 13%, 30%, 51%, and 72% for groups 1-4, respectively (pairwise P values <or=0.0002). Further stratification within each risk group using the preoperative PSA level with a cut point at 10 ng/mL revealed BF rates of 8% versus 35%, 25% versus 54%, 31% versus 73%, and 63% versus 86% for risk groups 1-4, respectively (all P values <0.0001).

CONCLUSIONS

An algorithm to predict BF based on prostatectomy findings has been validated, and the addition of the preoperative PSA level improved its ability to identify high risk patients who may benefit from entry into adjuvant treatment trials.

A Simple Inexpensive Method for the Production of Tissue Microarrays from Needle Biopsy Specimens

The use of tissue microarrays has become an efficient method for the high-throughput analysis of tissues with molecular markers, yet these studies have not been used to leverage the limited materials present in needle biopsies of human tissues. The use of these biopsy tissues is crucial to study diseases in patients who are treated by nonsurgical methods such as radiation, chemotherapy, or palliative care. The authors present a simple, inexpensive method for using needle biopsy specimens in tissue microarrays. Using this process with prostate cancer specimens, the authors demonstrate that over 150 slides can be produced from a single area of cancer in a needle biopsy and that the length of the core involved by cancer in the needle biopsy determines the number of available tissue microarray slides. The authors also note the optimal number of samples (three) needed from a single patient biopsy to guarantee sufficient material for analysis and perform an immunohistochemical correlation between needle biopsy and surgical resection tissue microarray samples for the quantitative marker Ki-67. This process can be extended to any type of needle biopsy specimen, increasing the number of studies and potential use of these tissues as a practical reality.

TNF receptor 1 is involved in the induction of apoptosis by the cyclin dependent kinase inhibitor p27Kip1 in the prostate cancer cell line PC-3

Loss of p27Kip1, a cyclin-dependent kinase inhibitor, is observed in aggressive prostate cancers. We demonstrated that intratumoral injections of recombinant adenovirus overexpressing p27Kip1 (Adp27) reduced the growth of prostate cancer xenografts in nude mice. Presently, we studied the mechanism(s) of cell death induced by Adp27 in prostate cancer cell line PC-3. Cells were infected with Adp27 and compared with those infected by empty virus or were non-infected. Cell cycle and typical markers of apoptosis were analyzed by flow cytometry in the presence of the following reagents: cycloheximide, pan-caspase inhibitor ZVAD-fmk, neutralizing anti-TNFR1, and anti-TNFR2. Overexpression of p27Kip1 protein and cell cycle arrest were noted within 24 h after Adp27-infection. Sub-G1 fraction, chromatin margination, and phosphatidylserine exposure were evident by the third day of treatment. Cycloheximide elevated sub-G1 fraction in Adp27-infected cells by threefold, while ZVAD-fmk reduced sub-G1 to control levels. Caspase-dependent apoptosis occurred in a third of the population, while two-thirds were ZVAD-fmk insensitive but TUNEL-positive. Flow cytometry showed increased expression of TNFR1 and TNFR2 in Adp27-infected cells. Neutralizing anti-TNFR1 decreased TUNEL-positive score, while anti-TNFR2 did not affect p27Kip1-induced apoptosis. This is the first report showing that p27Kip1 induces caspase-dependent and -independent stages of cell death that may involve TNF-signaling through TNFR1.

Update of staging and risk assessment for prostate cancer patients

PURPOSE OF REVIEW

This paper will review the current staging system for prostate adenocarcinoma patients, and will also review new information that can be combined with clinical and pathological staging in order to assess a patient's risk of success or failure of treatment.

RECENT FINDINGS

There has been significant stage migration of prostate cancer patients in the past 15 years, such that patients are currently being diagnosed younger, with lower clinical stages and serum prostate-specific antigen levels, and a lower risk of metastatic disease than previously. The incorporation of the results of extended prostate biopsy schemes, with stage, grade and serum prostate-specific antigen levels, improves the risk assessment of newly diagnosed prostate cancer patients. New imaging techniques, such as transrectal ultrasound Doppler flow and magnetic resonance spectroscopy hold promise for improving risk assessment. Molecular biomarkers may improve risk assessment in the future, although none are currently approved by the US Food and Drug Administration for this indication. Gene chip arrays may further refine risk assessment and assist with the identification of therapeutic targets.

SUMMARY

There has been significant stage migration of prostate cancer patients in the prostate-specific antigen era. Incorporating biopsy information into nomograms and risk assessment equations improves upon clinical staging and risk assessment. New imaging techniques, molecular markers and gene chip arrays hold promise for future risk assessment.