Can we prevent prostate cancer? Rationale and current status of prostate cancer chemoprevention

Management of prostate cancer. Part 1: chemoprevention

Numerous agents have been investigated in prostate cancer prevention. Many manipulate sex steroid levels or function, some regulate response to oxidative stress and others affect tumor proliferation and/or apoptosis. Some are postulated to even affect downstream targets, such as cyclooxygenase-2, which has been shown to be elevated in prostate cancer by most investigators. The evidence for all these potential chemopreventive agents is critically reviewed. While the current information base is vast, level 1 evidence is lacking, and ongoing trials are not due to provide such evidence for many years to come. In addition, the current lack of ability to accurately differentiate clinically important prostate cancer from latent disease makes chemoprevention in this setting even more challenging. Currently, no reliable biomarkers that can act as surrogate endpoints for the development of clinically relevant prostate cancer exist, which makes performing large chemoprevention trials expensive. At present, there is little to suggest that the urologist or General Practitioner should be recommending any particular chemopreventive agent to either the general population or those deemed to be at higher risk of contracting prostate cancer.

AT-101 (R-(-)-gossypol acetic acid) enhances the effectiveness of androgen deprivation therapy in the VCaP prostate cancer model

Prostate cancer remains a leading cause of cancer death in American men. Androgen deprivation therapy (ADT) is the most common treatment for advanced prostate cancer patients; however, ADT fails in nearly all cases resulting in castration resistant or androgen-insensitive (AI) disease. In many cases, this progression results from dysregulation of the pro-survival Bcl-2 family proteins. Inhibition of pro-survival Bcl-2 family proteins, therefore, may be an effective strategy to delay the onset of AI disease. Gossypol, a small molecule inhibitor of pro-survival Bcl-2 family proteins, has been demonstrated to inhibit AI prostate cancer growth. The apoptotic effect of gossypol, however, has been demonstrated to be attenuated by the presence of androgen in a prostate cancer xenograft mouse model (Vertebral Cancer of Prostate [VCaP]) treated with AT-101 (R-(-)-gossypol acetic acid). This study was undertaken to better understand the in vitro effects of androgen receptor (AR) on AT-101-induced apoptosis. VCaP cells treated with AT-101 demonstrated an increase in apoptosis and downregulation of Bcl-2 pro-survival proteins. Upon AR activation in combination with AT-101 treatment, apoptosis is reduced, cell survival increases, and caspase activation is attenuated. Akt and X inhibitor of apoptosis (XIAP) are downregulated in the presence of AT-101, and AR stimulation rescues protein expression. Combination treatment of bicalutamide and AT-101 increases apoptosis by reducing the expression of these pro-survival proteins. These data suggest that combination therapy of AT-101 and ADT may further delay the onset of AI disease, resulting in prolonged progression-free survival of prostate cancer patients.

Laparoscopic Peritoneal Drainage of Symptomatic Lymphoceles after Pelvic Lymph Node Dissection Using Methylene Blue Instillation

BACKGROUND

Lymphoceles are frequent complications of pelvic lymph node dissection. While small lymphoceles often remain undetected, larger ones can cause complications and require further treatment, e.g. percutaneous tube drainage alone or in combination with sclerotherapy. However, recurrence rates are considerable, and long-lasting drainage may lead to infection, prolonged hospitalization, and as a consequence, increased overall costs. We report the results of a simplified laparoscopic approach to drain lymphoceles after radical prostatectomy plus pelvic lymphadenectomy using methylene blue instillation.

METHODS

13 patients with large symptomatic pelvic/retroperitoneal lymphoceles refractory to percutaneous tube drainage and doxycycline sclerotherapy received a laparoscopic transperitoneal marsupialization following instillation of a sterile diluted methylene blue solution into the drained cavity to refill and mark the lymphocele.

RESULTS

All lymphoceles were sterile and ranged in size from 7 x 6 x 4 to 15 x 12 x 6 cm. Clinical symptoms included lower abdominal swelling, tenderness in the iliac fossa, ipsilateral lymphedema, deep venous thrombosis, wound fistula, and hydronephrosis due to ureteral obstruction. After methylene blue instillation, the lymphoceles were easily identified and opened. Median total operative time was 50 (range 25-70) min; blood loss was negligible. There was one complication in the form of a metachronous infection in the operating field and no relapses. Patients were discharged 1-5 (median 3) days after the surgical procedure.

CONCLUSIONS

Laparoscopic peritoneal drainage requires greater operative skill than percutaneous approaches. However, the instillation of a methylene blue solution simplifies this procedure as the extent and location of the lymphoceles can be precisely identified during laparoscopy. We recommend early application of laparoscopic peritoneal drainage following methylene blue instillation for patients with sterile lymphoceles after pelvic lymph node dissection in whom temporary percutaneous drainage and sclerotherapy failed to resolve the lymph fluid collection.

Endocrine regulation of prostate cancer growth

Prostate cancer is one of the most frequently diagnosed malignant neoplasms in the Western world. The focus of this article is on regulation of proliferation, apoptosis, angiogenesis and differentiation by steroid and peptide hormones. Steroid hormones, in particular androgens and estrogens, exert their effects through respective receptors. The androgen receptor is functional in all stages of the disease and it can be activated in a ligand-dependent and -independent manner. In prostate cancer, expression of some androgen receptor coactivators increases during tumor progression. Interleukins and transforming growth factor-β are multifunctional regulators of prostate growth and proliferation. Signal transduction cascades of fibroblast growth factors and insulin-like growth factors are responsible for increased survival and angiogenesis in prostate cancer. In clinical specimens obtained from prostate cancer, there is an increased phosphorylation of mitogen-activated protein kinase and Akt kinase, whose action in the regulation of cell survival is redundant.

Pomegranate fruit juice for chemoprevention and chemotherapy of prostate cancer

Prostate cancer is the most common invasive malignancy and the second leading cause of cancer-related deaths among U.S. males, with a similar trend in many Western countries. One approach to control this malignancy is its prevention through the use of agents present in diet consumed by humans. Pomegranate from the tree Punica granatum possesses strong antioxidant and antiinflammatory properties. We recently showed that pomegranate fruit extract (PFE) possesses remarkable antitumor-promoting effects in mouse skin. In this study, employing human prostate cancer cells, we evaluated the antiproliferative and proapoptotic properties of PFE. PFE (10-100 microg/ml; 48 h) treatment of highly aggressive human prostate cancer PC3 cells resulted in a dose-dependent inhibition of cell growth/cell viability and induction of apoptosis. Immunoblot analysis revealed that PFE treatment of PC3 cells resulted in (i) induction of Bax and Bak (proapoptotic); (ii) down-regulation of Bcl-X(L) and Bcl-2 (antiapoptotic); (iii) induction of WAF1/p21 and KIP1/p27; (iv) a decrease in cyclins D1, D2, and E; and (v) a decrease in cyclin-dependent kinase (cdk) 2, cdk4, and cdk6 expression. These data establish the involvement of the cyclin kinase inhibitor-cyclin-cdk network during the antiproliferative effects of PFE. Oral administration of PFE (0.1% and 0.2%, wt/vol) to athymic nude mice implanted with androgen-sensitive CWR22Rnu1 cells resulted in a significant inhibition in tumor growth concomitant with a significant decrease in serum prostate-specific antigen levels. We suggest that pomegranate juice may have cancer-chemopreventive as well as cancer-chemotherapeutic effects against prostate cancer in humans.