Bcl-2 and Bax expression predict prostate cancer outcome in men treated with androgen deprivation and radiotherapy on radiation therapy oncology group protocol 92-02

The E2F1/Rb and p53/MDM2 pathways in DNA repair and apoptosis: understanding the crosstalk to develop novel strategies for prostate cancer radiotherapy

Both the p53- and E2F1-signaling pathways are defective in almost all types of tumors, suggesting very important roles for their signaling networks in regulating the process of tumorigenesis and therapy response. Studies on Radiation Therapy Oncology Group tissue samples have identified aberrant expression of p53, MDM2 (an E3 ubiquitin ligase that targets p53 for proteosomal degradation), and p16 (an upstream regulator of retinoblastoma and hence E2F1 in prostate cancer); abnormal expression of these biomarkers has been associated with clinical outcome after radiotherapy ± androgen deprivation therapy. Although the proapoptotic properties of p53 are well documented, a relatively new aspect of p53 function as an active mediator of prosurvival signaling pathways is now emerging. E2F1 is a transcription factor that possesses both proapoptotic and prosurvival properties. Thus, the role of E2F1 in the process of tumorigenesis versus apoptosis is a contested issue that needs to be resolved. Furthermore, the role of E2F1 in DNA repair is being increasingly recognized. Thus, novel approaches to curb the prosurvival and DNA repair capability of E2F1 while promoting apoptotic function are of interest. In this review, we discuss the challenges involved in targeting the p53/E2F1 pathways and the crosstalk networks, and further propose potential therapeutic strategies for prostate cancer management.

[Bladder preservation using chemoradiation therapy for locally invasive bladder cancer]

PURPOSE

We investigated the long-term results and molecular markers of outcome with selective organ preservation in invasive bladder cancer using chemoradiation therapy.

PATIENTS AND METHODS

We examined locally invasive bladder cancer in 32 patients (30 men, 2 women; mean age at treatment 68.1 years) who underwent bladder-sparing protocols in the Department of Urology at Sumitomo Hospital between 2000 and 2005. The clinical stage was T2, T3, and T4 in 13, 16, and 3 patients, respectively. Our protocol includes aggressive transurethral resection of the bladder tumor (TURBT) and 46 Gy radiotherapy (2 Gy/fraction, 5 fractions/week) to the pelvis with concurrent cisplatin chemotherapy (20 mg/body/day, 5 days/week, the first and fourth week, intravenously). The initial evaluation included magnetic resonance imaging (MRI), urine cytology, and cystoscopy with a biopsy. During follow-up, if the patients developed superficial recurrence, they was treated with TURBT and intravesical Bacillus Calmette-Guérin (BCG), while patients with invasive recurrence were advised to undergo a salvage cystectomy. We examined the association between the expression of the Bcl-2 family in pretreatment TUR specimens and patient outcome. The mean follow-up was 54.6 months.

RESULTS

The first assessment after the induction chemoradiotherapy showed that bladder preservation was achieved in 27 patients (84.4%). The actuarial local control rate with an intact bladder was 56.3% (18 patients) at 3 years. The 1-, 3-, and 5-year cancer-specific survival rate was 90.6, 84.0, and 66.9%, respectively. The 5-year cancer-specific survival rate was 75.0, 67.2, and 33.3% in T2, T3, and T4, respectively. Bcl-x positivity was significantly associated with a poor cancer-specific survival rate (log-rank test, p = 0.038).

CONCLUSIONS

Chemoradiation therapy for invasive bladder cancer can achieve survival rates similar to those in patients treated with radical cystectomy, with successful bladder preservation. Our results suggest that the expression of Bcl-x is a potential prognostic marker for chemoradiation therapy in invasive bladder cancer.

Metronomic small molecule inhibitor of Bcl-2 (TW-37) is antiangiogenic and potentiates the antitumor effect of ionizing radiation

PURPOSE

To investigate the effect of a metronomic (low-dose, high-frequency) small-molecule inhibitor of Bcl-2 (TW-37) in combination with radiotherapy on microvascular endothelial cells in vitro and in tumor angiogenesis in vivo.

METHODS AND MATERIALS

Primary human dermal microvascular endothelial cells were exposed to ionizing radiation and/or TW-37 and colony formation, as well as capillary sprouting in three-dimensional collagen matrices, was evaluated. Xenografts vascularized with human blood vessels were engineered by cotransplantation of human squamous cell carcinoma cells (OSCC3) and human dermal microvascular endothelial cells seeded in highly porous biodegradable scaffolds into the subcutaneous space of immunodeficient mice. Mice were treated with metronomic TW-37 and/or radiation, and tumor growth was evaluated.

RESULTS

Low-dose TW-37 sensitized primary endothelial cells to radiation-induced inhibition of colony formation. Low-dose TW-37 or radiation partially inhibited endothelial cell sprout formation, and in combination, these therapies abrogated new sprouting. Combination of metronomic TW-37 and low-dose radiation inhibited tumor growth and resulted in significant increase in time to failure compared with controls, whereas single agents did not. Notably, histopathologic analysis revealed that tumors treated with TW-37 (with or without radiation) are more differentiated and showed more cohesive invasive fronts, which is consistent with less aggressive phenotype.

CONCLUSIONS

These results demonstrate that metronomic TW-37 potentiates the antitumor effects of radiotherapy and suggest that patients with head and neck cancer might benefit from the combination of small molecule inhibitor of Bcl-2 and radiation therapy.

Quantitative analysis of mRNA for 10 different drug resistance factors in dogs with lymphoma

Expression levels of ABCB1, ABCC1, Lung resistance-associated protein (LRP), ABCG2, p53, p21(waf1), Bcl-2, CD40L, glutathione S-transferase alpha (GSTα), and O⁶-methylguanine-DNA-methyltransferase (MGMT) genes, and mutation of p53 gene were examined in 23 dogs with multicentric high-grade lymphoma to explore their association with drug resistance of the tumor cells. Dogs were divided into chemotherapy-sensitive (n=13) and -resistant (n=10) groups according to the response to a 6-month modified version of the University of Wisconsin (UW)-Madison chemotherapy protocol (UW-25), and expression levels of these factors and frequency of p53 gene mutation were compared between groups. No significant differences were observed in expression levels of each factor between groups. However, 4 dogs in the chemotherapy-resistant group showed high expression of ABCB1. No significant difference was observed in the frequency of p53 mutation between groups. A possible association of ABCB1 with resistance to UW-25 was shown, but no uniform mechanism associated with drug resistance could be identified in dogs with lymphoma.

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.

Targeting the Bcl-2

PURPOSE OF REVIEW

Members of the Bcl-2 family of proteins are critical components in regulating the intrinsic apoptotic pathway. Bcl-2 protein overexpression is associated with drug resistance and poor clinical outcome in cancer patients. Preclinical and clinical evaluations demonstrate that downregulation of Bcl-2 restores the intrinsic apoptotic pathways with antitumor effects. Thus, Bcl-2 is aggressively pursued as a therapeutic target in cancer with several new drugs undergoing clinical investigations. In this manuscript, we will review clinical information on some of the novel compounds specifically designed to target the Bcl-2 gene product(s).

RECENT FINDINGS

Extensive clinical evaluations using a Bcl-2-specific antisense have resulted in an overall disappointing experience. But new small molecule inhibitors of the Bcl-2 hold promise with high target affinity, ease of administration and improved toxicity profile. Early stage clinical trials of these agents are revealing promising results alone as well as in combination with existing anticancer therapeutics. Encouraging results from some of these clinical investigations are summarized in this review.

SUMMARY

Downregulation of Bcl-2 and restoration of a critical apoptotic pathway in cancer cells remains an important strategy. Novel Bcl-2 inhibitors have started to deliver the therapeutic promise of this target-specific quest.

An improved method for constructing tissue microarrays from prostate needle biopsy specimens

Background:

Prostate cancer diagnosis is routinely made by the histopathological examination of formalin fixed needle biopsy specimens. Frequently this is the only cancer tissue available from the patient for the analysis of diagnostic and prognostic biomarkers. There is, therefore, an urgent need for methods that allow the high-throughput analysis of these biopsy samples using immunohistochemical (IHC) markers and fluorescence in situ hybridisation (FISH) analysis based markers.

Methods:

A method that allows the construction of tissue microarrays (TMAs) from diagnostic prostate needle biopsy cores has previously been reported. However, the technique only allows the production of low-density biopsy TMAs with a maximum of 20 cores per TMA. Here two methods are presented that allow the rapid and uniform production of biopsy TMAs containing between 54 and 72 biopsy cores. IHC and FISH techniques were used to detect biomarker status.

Results:

Biopsy TMAs were constructed from prostate needle biopsy specimens taken from 102 patients entered into an active surveillance trial and 201 patients in a radiotherapy trial. The detection rate for cancer in slices of these biopsy TMAs was 66% and 79% respectively. Slices of a biopsy TMA prepared from biopsies from active surveillance patients were used to detect multiple IHC markers and to score TMPRSS2-ERG fusion status in a FISH-based assay.

Conclusions:

The construction of biopsy TMAs provides an effective method for the multiplex analysis of IHC and FISH markers and for their assessment as prognostic biomarkers in the context of clinical trials.

Biomolecular markers of outcome prediction in prostate cancer

Prostate cancer has a variable clinical outcome and, therefore, there is a clear need for novel molecular markers that are specifically associated with biologically aggressive disease to improve staging and prognostication and also to provide mechanistic information to facilitate treatment selection. Different candidate biomarkers have been identified that are linked to patient prognosis and/or response to specific treatments. Such molecules are involved in diverse cellular processes (including cell cycle regulation, cell death and apoptosis, signal transduction, cell adhesion, and angiogenesis) within which aberrant activity of several regulatory pathways has been seen in prostate cancer. Although the number of molecular markers continues to grow, mainly because of the advent of high-throughput methods, more work needs to be done to develop uniform standards for their characterization to enable comparison of markers across studies. Moreover, a rate-limiting step in the development of molecular markers is large-scale clinical assessment and their evaluation in the context of prediction model improvement. In fact, thus far, only a few studies have tested and demonstrated whether the addition of new biological markers improves the accuracy of standard clinical models (nomograms) in predicting biochemical progression in patients with clinically localized prostate cancer who underwent radical prostatectomy. Cancer 2009;115(13 suppl):3058-67. (c) 2009 American Cancer Society.

Predictive models in external beam radiotherapy for clinically localized prostate cancer

Predictive models are being used increasingly in effort to allow physician and patient expectations to be aligned with outcomes that are based on available data. Most predictive models for men who receive external beam radiotherapy for clinically localized prostate cancer are based on Gleason score, clinical tumor classification, and prostate-specific antigen (PSA) levels. More sophisticated models also have been developed that incorporate treatment-related variables, such as the dose of radiation and the use of androgen-deprivation therapy. Most of the predictive models applied to prostate cancer were derived using PSA recurrence rates as the major endpoint, but clinical endpoints have been incorporated increasingly into predictive models. Biomarkers also are increasingly being added to predictive models in an effort to strengthen them. The Radiation Therapy Oncology Group (RTOG) has completed studies on a wide range of markers using tissue from 2 phase 3 trials (RTOG 8610 and 9202). To date, preliminary assessments of p53; DNA ploidy; p16/retinoblastoma 1 protein; Ki-67; mouse double-minute p53 binding protein homolog; Bcl-2/Bcl-2-associated X protein; cytosine, adenine, and guanine repeats; cyclooxygenase-2; signal transducer and activator of transcription 3; cytochrome P450 3A4; and protein kinase A have been completed. Although they are not ready for widespread, routine use, there are reasons to believe that future models will combine these markers with traditional pretreatment and treatment-related variables and will improve our ability to predict outcome and select the optimal treatment. Cancer 2009;115(13 suppl):3112-20. (c) 2009 American Cancer Society.

Molecular fingerprinting of radiation resistant tumors: can we apprehend and rehabilitate the suspects?

Radiation therapy continues to be one of the more popular treatment options for localized prostate cancer. One major obstacle to radiation therapy is that there is a limit to the amount of radiation that can be safely delivered to the target organ. Emerging evidence suggests that therapeutic agents targeting specific molecules might be combined with radiation therapy for more effective treatment of tumors. Recent studies suggest that modulation of these molecules by a variety of mechanisms (e.g., gene therapy, antisense oligonucleotides, small interfering RNA) may enhance the efficacy of radiation therapy by modifying the activity of key cell proliferation and survival pathways such as those controlled by Bcl-2, p53, Akt/PTEN and cyclooxygenase-2. In this article, we summarize the findings of recent investigations of radiosensitizing agents in the treatment of prostate cancer.

Differential response to zinc-induced apoptosis in benign prostate hyperplasia and prostate cancer cells

Zinc concentrations in the prostate are uniquely high but are dramatically decreased with prostate cancer. Studies have suggested that increasing zinc in the prostate may be a potential therapeutic strategy. The goal of this study was to evaluate the antiproliferative effects of zinc in prostate cancer cells (PC-3) and noncancerous benign prostate hyperplasia (BPH) cells (BPH-1) and to define possible mechanisms. PC-3 and BPH-1 cells were treated with zinc (0-250 microM) for 24 and 48 h, and cell growth and viability were examined. Apoptosis was assessed by phosphatidylserine externalization, caspase activation and protein expression of B-cell CLL/lymphoma 2 (Bcl-2)-associated X protein (BAX):Bcl-2. BPH-1 cells were more sensitive to the antiproliferative effects of zinc compared to PC-3. The response to zinc in PC-3 and BPH-1 cells differed as evidenced by opposing effects on Bcl-2:BAX expression. Additionally, different effects on the nuclear expression and activity of the p65 subunit of nuclear factor kappa B were observed in response to zinc between the two cell types. The differential response to zinc in PC-3 and BPH-1 cells suggests that zinc may serve an important role in regulating cell growth and apoptosis in prostate cancer and hyperplasia cells.

The Paradox of Oestradiol-Induced Breast Cancer Cell Growth and Apoptosis

High dose oestrogen therapy was used as a treatment for postmenopausal patients with breast cancer from the 1950s until the introduction of the safer antioestrogen, tamoxifen in the 1970s. The anti-tumour mechanism of high dose oestrogen therapy remained unknown. There was no enthusiasm to study these signal transduction pathways as oestrogen therapy has almost completely been eliminated from the treatment paradigm. Current use of tamoxifen and the aromatase inhibitors seek to create oestrogen deprivation that prevents the growth of oestrogen stimulated oestrogen receptor (ER) positive breast cancer cells. However, acquired resistance to antihormonal therapy does occur, but it is through investigation of laboratory models that a vulnerability of the cancer cell has been discovered and is being investigated to provide new opportunities in therapy with the potential for discovering new cancer-specific apoptotic drugs. Laboratory models of resistance to raloxifene and tamoxifen, the selective oestrogen receptor modulators (SERMs) and aromatase inhibitors demonstrate an evolution of drug resistance so that after many years of oestrogen deprivation, the ER positive cancer cell reconfigures the survival signal transduction pathways so oestrogen now becomes an apoptotic trigger rather than a survival signal. Current efforts are evaluating the mechanisms of oestrogen-induced apoptosis and how this new biology of oestrogen action can be amplified and enhanced, thereby increasing the value of this therapeutic opportunity for the treatment of breast cancer. Several synergistic approaches to therapeutic enhancement are being advanced which involve drug combinations to impair survival signaling with the use of specific agents and to impair bcl-2 that protects the cancer cell from apoptosis. We highlight the historical understanding of oestrogen's role in cell survival and death and specifically illustrate the progress that has been made in the last five years to understand the mechanisms of oestrogen-induced apoptosis. There are opportunities to harness knowledge from this new signal transduction pathway to discover the precise mechanism of this oestrogen-induced apoptotic trigger. Indeed, the new biology of oestrogen action also has significance for understanding the physiology of bone remodeling. Thus, the pathway has a broad appeal in both physiology and cancer research.

Tumour growth fraction measured by immunohistochemical staining of Ki67 is an independent prognostic factor in preoperative prostate biopsies with small-volume or low-grade prostate cancer

Accurate prognostic parameters in prostate biopsies are needed to better counsel individual patients with prostate cancer. We evaluated the prognostic impact of morphologic and immunohistochemical parameters in preoperative prostate cancer biopsies. A consecutive series of prostate biopsies of 279 men (72% with clinical stage T1c and 23% with T2) who subsequently underwent radical prostatectomy was prospectively analysed for Gleason score, number and percentage of positive cores (NPC, PPC), total percentage of biopsy tissue with tumour (TPT), maximum tumour percentage per core (MTP), and expression of Ki67, Bcl-2 and p53. All biopsy features were significantly associated with at least one feature of the radical prostatectomy specimen. pT stage was independently predicted by PSA, seminal vesicle invasion by Ki67 LI, positive margins by PSA and MTP, large tumour diameter by PSA and PPC, and Gleason score by biopsy Gleason score, MTP, and Ki67 LI, respectively. Biopsy Gleason score, NPC (1 vs. >1), TPT (<7 vs. >or=7%), and Ki67 LI (<10 vs. >or=10%) were significant predictors of biochemical recurrence after radical prostatectomy (p < 0.01, each). KI67 LI was the only independent prognostic factor in case of a low TPT (<7%) or low Gleason score (<7), the hazard ratio being 6.76 and 6.44, respectively. In summary, preoperative Gleason score, NPC, TPT and Ki67 LI significantly predict the risk of recurrence after radical prostatectomy, and Ki67 is an independent prognosticator in biopsies with low-volume or low-grade prostate cancer. Analysis of Ki67 LI in these biopsies may help to better identify patients with clinically insignificant prostate cancer.

Oligomeric proanthocyanidin complexes (OPC) exert anti-proliferative and pro-apoptotic effects on prostate cancer cells

BACKGROUND

Oligomeric proanthocyanidin complexes (OPC) are extracted from grape seeds or maritime pine bark and have been used for enhancement of capillary stability and lymphatic drainage. Since a role for OPC in cancer prevention was postulated, we asked whether they have an effect on prostate cancer cells.

METHODS

Cell proliferation was determined by (3)H-thymidine assay and cell cycle status was analyzed on a flow cytometer. Expression of regulators of proliferation and apoptosis was determined by Western blot.

RESULTS

We found that androgen-responsive cells LNCaP are more sensitive to OPC in terms of inhibition of proliferation in comparison to androgen receptor-negative PC3 or DU145 cells. Treatment with OPC resulted in a decrease in the percentage of LNCaP cells in the S phase and an increase in the percentage of cells in sub G1 phase. The anti-proliferative and pro-apoptotic effect of OPC in the LNCaP cell line was associated with down-regulation of expression of the androgen receptor. Interestingly, similar regulatory effects of OPC, such as inhibition of expression of cyclin-dependent kinases and cyclins and stimulation of tumor suppressors p21 and p27, were seen in LNCaP and PC3 cells. Favorable changes in the Bcl-2/Bax ratio were observed in LNCaP and PC3 cells after the treatment with OPC. OPC caused an increase of phosphorylated mitogen-activated protein kinase p44 and p42, thus suggesting induction of cellular differentiation.

CONCLUSIONS

We conclude that OPC is a candidate that fulfills criteria for chemopreventive strategies in prostate cancer that might be established in following in vivo studies.

Expanding circle of inhibition: small-molecule inhibitors of Bcl-2 as anticancer cell and antiangiogenic agents

The specific targeting of diseases, particularly cancer, is a primary aim in drug development, as specificity reduces unwelcome effects on healthy tissue and increases drug efficacy at the target site. Drug specificity can be increased by improving the delivery system or by selecting drugs with affinity for a molecular ligand specific to the disease state. The role of the prosurvival Bcl-2 protein in maintaining the normal balance between apoptosis and cellular survival has been recognized for more than a decade. Bcl-2 is vital during development, much less so in adults. It has also been noted that some cancers evade apoptosis and obtain a survival advantage through aberrant expression of Bcl-2. The new and remarkably diverse class of drugs, small-molecule inhibitors of Bcl-2 (molecular weight approximately 400 to 800 Daltons), is examined herein. We present the activities of these compounds along with clinical observations, where available. The effects of Bcl-2 inhibition on attenuation of tumor cell growth are discussed, as are studies revealing the potential for Bcl-2 inhibitors as antiangiogenic agents. Despite an enormous body of work published for the Bcl-2 family of proteins, we are still learning exactly how this group of molecules interacts and indeed what they do. The small-molecule inhibitors of Bcl-2, in addition to their therapeutic potential, are proving to be an important investigative tool for understanding the function of Bcl-2.

The alpha-5 helix of Bax is sensitive to ubiquitin-dependent degradation

The pro-apoptotic protein Bax is instable in many cancer cells but the mechanism of Bax degradation remains unclear. Four different lengths of deductive Bax degradation sensitive (BDS) sequences within BH3-BH1 region, BDS-1 (Bax 67-124), BDS-3 (Bax 74-107), BDS-5 (Bax 67-107), and BDS-7 (Bax 74-124), were tested for the susceptibility to ubiquitin-dependent degradation. Both BDS-1 and BDS-7 which contain the alpha5 helix, a putative pore-forming domain of Bax, are sensitive to proteasome-dependent degradation and ubiquitin-conjugation. The Bax alpha5-deletion mutant (Bax-Deltaalpha5) was stable and also maintained its apoptosis-inducing ability. Deletion of helices alpha1 and part of alpha2 (Bax-Delta1-66) or helices alpha3 and alpha4 (Bax-Deltaalpha3,4) did not affect the sensitivity to degradation. However, Bax-Delta1-66 mutant was not able to induce apoptosis. Thus, we propose that the alpha5 helix of Bax is sensitive to ubiquitin-dependent degradation. Moreover, Bax mutant retains its pro-apoptosis ability when the alpha5 helix is deleted.