Management of Hormone-Sensitive and Hormone-Refractory Metastatic Prostate Cancer

Ethanol extract of Remotiflori radix induces endoplasmic reticulum stress-mediated cell death through AMPK/mTOR signaling in human prostate cancer cells

Remotiflori radix is the root of Mosidae, which has long been used as a traditional medicine to treat chills, fever, and phlegm discharge. The ethanol extract of Mosidae leaves (MLE) possesses strong antioxidant and chemopreventive activities. However, the anti-cancer effects of the Remotiflori radix have not been examined. We used the ethanol extract of Remotiflori radix (ERR) and the PC-3 and DU145 prostate cancer cell lines in this study. We found that > 100 μg/mL ERR caused dose- and time-dependent cell death. Autophagic and apoptotic cell numbers increased in a dose-dependent manner as incubation time was prolonged, and LC3 punctuation, YO-PRO-1 uptake, DNA fragmentation, activation of caspases, and PARP cleavage were induced. Phosphorylation of AMPK, ULK, and p38 was increased after ERR treatment, and the level of the ER stress marker CHOP was also elevated. AMPK knockdown dramatically blocked ERR-mediated CHOP expression and cell death, suggesting that AMPK activation and ER stress play a critical role in ERR-induced cell death. Furthermore, oral administration of ERR at 50 mg/kg efficiently suppressed tumorigenic growth of PC-3 cells with no adverse effects. These results suggest that the ERR can be used as a safe and potent alternative therapy for patients with prostate cancer.

Piperine, a Bioactive Component of Pepper Spice Exerts Therapeutic Effects on Androgen Dependent and Androgen Independent Prostate Cancer Cells

Prostate cancer is the most common solid malignancy in men, with 32,000 deaths annually. Piperine, a major alkaloid constituent of black pepper, has previously been reported to have anti-cancer activity in variety of cancer cell lines. The effect of piperine against prostate cancer is not currently known. Therefore, in this study, we investigated the anti-tumor mechanisms of piperine on androgen dependent and androgen independent prostate cancer cells. Here, we show that piperine inhibited the proliferation of LNCaP, PC-3, 22RV1 and DU-145 prostate cancer cells in a dose dependent manner. Furthermore, Annexin-V staining demonstrated that piperine treatment induced apoptosis in hormone dependent prostate cancer cells (LNCaP). Using global caspase activation assay, we show that piperine-induced apoptosis resulted in caspase activation in LNCaP and PC-3 cells. Further studies revealed that piperine treatment resulted in the activation of caspase-3 and cleavage of PARP-1 proteins in LNCaP, PC-3 and DU-145 prostate cancer cells. Piperine treatment also disrupted androgen receptor (AR) expression in LNCaP prostate cancer cells. Our evaluations further show that there is a significant reduction of Prostate Specific Antigen (PSA) levels following piperine treatment in LNCaP cells. NF-kB and STAT-3 transcription factors have previously been shown to play a role in angiogenesis and invasion of prostate cancer cells. Interestingly, treatment of LNCaP, PC-3 and DU-145 prostate cancer cells with piperine resulted in reduced expression of phosphorylated STAT-3 and Nuclear factor-κB (NF-kB) transcription factors. These results correlated with the results of Boyden chamber assay, wherein piperine treatment reduced the cell migration of LNCaP and PC-3 cells. Finally, we show that piperine treatment significantly reduced the androgen dependent and androgen independent tumor growth in nude mice model xenotransplanted with prostate cancer cells. Taken together, these results support further investigation of piperine as a potential therapeutic agent in the treatment of prostate cancer.

Sorafenib sensitizes (-)-gossypol-induced growth suppression in androgen-independent prostate cancer cells via Mcl-1 inhibition and Bak activation

The natural BH3-mimetic (-)-gossypol shows promising efficacy in ongoing phase II/III clinical trials for human prostate cancer. Here, we show for the first time, that treatment with (-)-gossypol and multikinase inhibitor sorafenib synergistically suppresses the growth of androgen-independent prostate cancer cells (AI-PC) in vitro and in vivo. Our data suggest that sorafenib attenuates (-)-gossypol-induced Mcl-1 upregulation in AI-PCs. In this way, it serves as a potent chemosensitizer to affect cell death. Interestingly, (-)-gossypol and sorafenib induce cell death via two distinct pathways among different AI-PCs; DU145 cells via apoptosis and PC-3 via autophagy. The appointed death pathway may depend on the level of proapoptotic protein Bak, although the level of antiapoptotic protein Bcl-2 plays some role in it. DU145 cells with high Bak level prefer apoptosis induction, whereas PC-3 cells with low Bak prefer the induction of autophagy. Furthermore, inhibiting nondominant death pathways, that is, autophagy in DU145 and apoptosis in PC-3, enhances cell killing by (-)-gossypol/sorafenib combination therapy. Ultimately, our data expose a new action for sorafenib as an enhancer of (-)-gossypol-induced cell growth suppression and reveal a novel cell death mode by Bak activation manners in AI-PCs. These new insights may facilitate the rational design of clinical trials by selecting patients most likely to benefit from the Bcl-2-targeted molecular therapy.

A natural BH3 mimetic induces autophagy in apoptosis-resistant prostate cancer via modulating Bcl-2-Beclin1 interaction at endoplasmic reticulum

A natural BH3-mimetic, small-molecule inhibitor of Bcl-2, (-)-gossypol, shows promise in ongoing phase II and III clinical trials for human prostate cancer. In this study we show that (-)-gossypol preferentially induces autophagy in androgen-independent (AI) prostate cancer cells that have high levels of Bcl-2 and are resistant to apoptosis, both in vitro and in vivo, but not in androgen-dependent (AD) cells with low Bcl-2 and sensitive to apoptosis. The Bcl-2 inhibitor induces autophagy through blocking Bcl-2-Beclin1 interaction, together with downregulating Bcl-2, upregulating Beclin1, and activating the autophagic pathway. The (-)-gossypol-induced autophagy is dependent on Beclin1 and Atg5. Our results show for the first time that (-)-gossypol can also interrupt the interactions between Beclin1 and Bcl-2/Bcl-xL at endoplasmic reticulum, thus releasing the BH3-only pro-autophagic protein Beclin1, which in turn triggers the autophagic cascade. Oral administration of (-)-gossypol significantly inhibited the growth of AI prostate cancer xenografts, representing a promising new regimen for the treatment of human hormone-refractory prostate cancer with Bcl-2 overexpression. Our data provide new insights into the mode of cell death induced by Bcl-2 inhibitors, which will facilitate the rational design of clinical trials by selecting patients who are most likely to benefit from the Bcl-2-targeted molecular therapy.

Chemosensitization of prostate cancer by modulating Bcl-2 family proteins

A major challenge in oncology is the development of chemoresistance. This often occurs as cancer progresses and malignant cells acquire mechanisms to resist insults that would normally induce apoptosis. The onset of androgen independence in advanced prostate cancer is a prime example of this phenomenon. Overexpression of the pro-survival/anti-apoptotic proteins Bcl-2, Bcl-xL, and Mcl-1 are hallmarks of this transition. Here we outline the evolution of therapeutics designed to either limit the source or disrupt the interactions of these pro-survival proteins. By either lessening the stoichiometric abundance of Bcl-2/xL/Mcl-1 in reference to their pro-apoptotic foils or freeing these pro-apoptotic proteins from their grip, these treatments aim to sensitize cells to chemotherapy by priming cells for death. DNA anti-sense and RNA interference have been effectively employed to decrease Bcl-2 family mRNA and protein levels in cell culture models of advanced prostate cancer. However, clinical studies are lagging due to in vivo delivery challenges. The burgeoning field of nanoparticle delivery holds great promise in helping to overcome the challenge of administering highly labile nucleic acid based therapeutics. On another front, small molecule inhibitors that block the hetero-dimerization of pro-survival with pro-apoptotic proteins have significant clinical advantages and have advanced farther in clinical trials with promising early results. Most recently, a peptide has been discovered that can convert Bcl-2 from a pro-survival to a pro-apoptotic protein. The future may lie in targeting multiple steps of the apoptotic pathway, including Bcl-2/xL/Mcl-1, to debilitate the survival capacity of cancer cells and make chemotherapy induced death their only option.

Natural BH3 mimetic (-)-gossypol chemosensitizes human prostate cancer via Bcl-xL inhibition accompanied by increase of Puma and Noxa

Antiapoptotic members of the Bcl-2 family proteins are overexpressed in prostate cancer and are promising molecular targets for modulating chemoresistance of prostate cancer. (-)-Gossypol, a natural BH3 mimetic, is a small-molecule inhibitor of Bcl-2/Bcl-xL/Mcl-1 currently in phase II clinical trials as an adjuvant therapy for human prostate cancer. Our objective is to examine the chemosensitization potential of (-)-gossypol in prostate cancer and its molecular mechanisms of action. (-)-Gossypol inhibited cell growth and induced apoptosis through mitochondria pathway in human prostate cancer PC-3 cells and synergistically enhanced the antitumor activity of docetaxel both in vitro and in vivo in PC-3 xenograft model in nude mouse. (-)-Gossypol blocked the interactions of Bcl-xL with Bax or Bad in cancer cells by fluorescence resonance energy transfer assay and overcame the Bcl-xL protection of FL5.12 model cells on interleukin-3 withdrawal. Western blot and real-time PCR studies showed that a dose-dependent increase of the proapoptotic BH3-only proteins Noxa and Puma contributed to the cell death induced by (-)-gossypol and to the synergistic effects of (-)-gossypol and docetaxel. The small interfering RNA knockdown studies showed that Noxa and Puma are required in the (-)-gossypol-induced cell death. Taken together, these data suggest that (-)-gossypol exerts its antitumor activity through inhibition of the antiapoptotic protein Bcl-xL accompanied by an increase of proapoptotic Noxa and Puma. (-)-Gossypol significantly enhances the antitumor activity of chemotherapy in vitro and in vivo, representing a promising new regime for the treatment of human hormone-refractory prostate cancer with Bcl-2/Bcl-xL/Mcl-1 overexpression.

Combined use of zoledronic acid and 153Sm-EDTMP in hormone-refractory prostate cancer patients with bone metastases

Purpose

¹⁵³Sm-ethylenediaminetetramethylenephosphonic acid (EDTMP; Quadramet®) is indicated for the treatment of painful bone metastases, whereas zoledronic acid (Zometa®) is indicated for the prevention of skeletal complications. Because of the different therapeutic effects, combining the treatments may be beneficial. Both, however, accumulate in areas with increased osteoblastic activity. Possible drug interactions were investigated.

Methods

Patients with hormone-refractory prostate cancer were treated with 18.5 MBq/kg ¹⁵³Sm-EDTMP in weeks 1 and 3 and with 37 MBq/kg in week 15. Treatment with 4 mg zoledronic acid began in week 3 and continued every 4 weeks through week 23. In weeks 3 and 15, zoledronic acid was administered 2 days before ¹⁵³Sm-EDTMP treatment. Urine was collected 48 h after injection of ¹⁵³Sm-EDTMP, and whole-body images were obtained 6, 24 and 48 h post-injection. The effect of zoledronic acid on total bone uptake of ¹⁵³Sm-EDTMP was measured indirectly by the cumulative activity excreted in the urine in weeks 1, 3 and 15. Biodistribution, safety, tolerability and effect on prostate-specific antigen level were also studied.

Results

The urinary excretion in week 3 divided by the urinary excretion in week 1 (baseline) times 100% was mean 98.4 ± 11.6% (median 96.2%). From week 1 to 15, after four zoledronic acid treatments, the mean ratio was 101.9 ± 10.7% (median 101.8%). Bioequivalence could be concluded by using a two-sample t test for both per-protocol (n = 13) and full-analysis sets (n = 18). Toxicity was comparable to of monotherapy with ¹⁵³Sm-EDTMP.

Conclusion

Zoledronic acid treatment does not influence ¹⁵³Sm-EDTMP skeletal uptake. Combined treatment is feasible and safe.

Randomised phase III study of intravenous vinorelbine plus hormone therapy versus hormone therapy alone in hormone-refractory prostate cancer

BACKGROUND

Vinorelbine (VRL) has been shown to be active in hormone-refractory prostate cancer (HRPC) in phase II studies, alone or in combination. Its moderate toxicity profile is well tolerated in elderly patients.

PATIENTS AND METHODS

Patients with metastatic prostate cancer, progressive after primary hormonal therapy, were randomised to receive intravenous VRL 30 mg/m2 on days 1 and 8 every 3 weeks, and hydrocortisone 40 mg/day or hydrocortisone alone until disease progression. Centres could choose to add aminoglutethimide 1000 mg/day to hydrocortisone as second-line hormone therapy (HT) for all their patients. Randomisation was stratified by centre. Further chemotherapy was allowed after progression. The primary end point was progression-free survival (PFS). The final analysis was performed on a total of 414 patients. Reported results were all based on intention-to-treat analyses. All progressions and responses were reviewed by an independent panel.

RESULTS

PFS was significantly prolonged in the VRL plus HT arm compared with the HT alone arm, according to the statistical hypothesis of the protocol (P=0.055 in the two-sided log-rank test with a pre-specified significance level of 10%). The 6-month PFS rates were 33.2% versus 22.8%, and the median durations of PFS were 3.7 versus 2.8 months. In the multivariate Cox analysis, which included age, Karnofsky performance status (PS), haemoglobin, alkaline phosphatase at study entry and number of prior hormonal treatments, the P value was decreased to 0.005. The prostate-specific antigen (PSA) response rate (> or =50% decline sustained for at least 6 weeks) was significantly higher for VRL plus HT compared with HT (30.1% versus 19.2%; P=0.01). Clinical benefit, defined as a decrease in pain intensity or analgesic consumption or an improvement of Karnofsky PS for at least 9 weeks, and at least stable assessment in the other two, was also more frequently observed in patients who received VRL plus HT versus HT alone (30.6% and 19.2%; P=0.008). There was no statistical difference in overall survival. Forty-three per cent of patients in the HT arm received at least one line of further chemotherapy after progression, compared with 28% of patients in the VRL-based arm. Aminoglutethimide did not seem to result in better efficacy for either arm. VRL plus HT was well tolerated, with a median administered relative dose intensity of 90%; grade 4 neutropenia occurred in 6.5% of patients and non-haematological toxicity was rare.

CONCLUSIONS

The combination of VRL and hydrocortisone compared with hydrocortisone alone resulted in improved clinical benefit, PFS and PSA response rate. This therapeutic gain is similar to that previously reported with mitoxantrone in combination with low-dose corticosteroids. There was no gain in survival; however, the combination is well tolerated in this elderly group of patients, who often present cardiac co-morbidities, and therefore offers an active and safe therapeutic option for patients with hormone-refractory prostate cancer.

Trends in hormonal management of prostate cancer: a population-based study in Ontario

OBJECTIVE

To provide a population-based description of current practice in the use of hormonal management of prostate cancer. DESIGN,SETTING & PARTICIPANTS: All men in Ontario, Canada, age 65 and older, with confirmed prostate cancer starting maintained hormonal therapy, from July 1992 through December 1998 (11,435 patients). Data sources included the provincial drug benefit plan, hospital services data, and Ontario Cancer Registry.

OUTCOME MEASURES

Rates and trends in the use of: surgical or medical castration; total androgen blockade (TAB); and monotherapies based on steroidal or nonsteroidal antiandrogens.

RESULTS

In 5.5 years, use of 'standard' therapy based on surgical or medical castration alone dropped from 36% to 26% of patients, while the use of TAB doubled from 22% to 41%. Approximately 15% of patients received nonsteroidal antiandrogens without evidence of therapy aimed at central androgen blockade. Marked regional differences were observed and not explained by patient age or practitioner specialty.

CONCLUSIONS

New hormonal therapies for prostate cancer have implications in terms of disease control, patient survival, side effects, and costs. Rapid growth in prescribing of antiandrogens may represent an unnecessary expense for public or private payers, and observed regional differences likely reflect lack of consensus on the relative merit of TAB. Patients and practitioners must have current information on the advantages and disadvantages of different therapeutic options, and quality-of life, particularly with respect to emerging drug therapies.