Hormone-independent Prostate Cancer Research Articles

Anticancer Effects of Propolis Extracts Obtained with the Cold Separation Method on PC-3 and DU-145 Prostate Cancer Cell Lines

Plant extracts are increasingly tested for their biological activity and interactions with neoplastic cells. One of such sources of biologically active substances is propolis. This product has been known for thousands of years and is widely used in alternative, folk medicine. Articles describing its effects on the metabolism and cell signaling pathways of neoplastic cells derived from different organs are also published more and more frequently. The purpose of our study was to evaluate the biological activity of propolis extract produced with the cold separation method into hormone-dependent and hormone-independent prostate cancer cell lines. In our study, the propolis extracts showed at least an inhibitory effect on the growth of PC-3 and DU-145 neoplastic cells. Our results suggest that propolis extracts obtained with the cold separation method may be considered as promising compounds for the production of health-promoting supplements.

Docetaxel resistance-derived LINC01085 contributes to the immunotherapy of hormone-independent prostate cancer by activating the STING/MAVS signaling pathway

Acquired docetaxel (doc) resistance, one of the major reasons for unfavorable prognosis in patients with aggressive hormone-independent prostate cancer (HIPC), is a major obstacle for patient treatment. Dysregulation of long non-coding RNAs promotes or suppresses chemoresistance in multiple cancers; however, the specific molecular mechanisms underlying HIPC remain unknown. In this study, we found that the LINC01085, as a tumor-suppressor, which showed significant clinically relevant in HIPC patients with doc-resistance. Mechanistically, in docetaxel-sensitive cells, LINC01085 could specifically bind to both TANK-binding kinase 1 (TBK1) and glycogen synthase kinase 3β (GSK3β), and higher LINC01085 RNA levels could inhibit TBK1 dimerization. Whereas, in doc-resistant cells, lower LINC01085 RNA level lost the strong binding with both, meanwhile, the interaction between TBK1 and GSK3β enhanced which accelerated TBK1 phosphorylation at the Ser-172 site, resulting in decreased expression levels of PD-L1 and NF-κB as well as the secretion of type I/III interferons. Thus, Overexpression of LINC01085 combined with immune checkpoint blockade is an effective strategy for the treatment of HIPC patients.

Abstract 3311: Darolutamide potentiates the antitumor efficacy of a PSMA-targeted thorium-227 conjugate (PSMA-TTC) in a hormone-independent prostate cancer model

Abstract Androgen receptor (AR) inhibitors are standard of care for the treatment of advanced prostate cancer. Despite an initial response to treatment, patients eventually progress, and novel therapeutic approaches are required. Prostate-specific membrane antigen (PSMA; FOLH1) is an integral membrane glycoprotein that is highly expressed in prostate cancer but has limited expression in normal tissues. PSMA-TTC (227Th-pelgifatamab corixetan; BAY 2315497) consists of the alpha emitter thorium-227 complexed to a 3,2-HOPO chelator conjugated to a PSMA targeting antibody. PSMA-TTC delivers potent radiation to PSMA expressing cells. Here we evaluated the efficacy of PSMA-TTC in combination with darolutamide, a novel AR inhibitor in a hormone insensitive prostate cancer model and investigated the mode of action of the combination treatment. In vitro, darolutamide induced the expression of PSMA in the androgen-independent cell lines C4-2 and 22Rv1 more than 3-fold and 2-fold, respectively. Expression of the apoptosis marker CDKN1A was significantly induced in the PSMA-TTC alone and in the combination group compared to vehicle. Expression of the DNA repair genes BRCA1, XRCC2 and XRCC3 were significantly reduced in PSMA-TTC alone and in the combination group compared to vehicle. In vivo, a single i.v. injection of PSMA-TTC at 300 kBq/kg resulted in a tumor/control (T/C) ratio of 0.44 on day 19 in the 22Rv1 hormone-insensitive prostate cancer model while a twice daily oral treatment with 100 mg/kg darolutamide showed a T/C ratio of 0.82. The combination of darolutamide and PSMA-TTC resulted in a higher efficacy with a T/C ratio of 0.27. Tumor area on day 19 after treatment was significantly reduced in the PSMA-TTC alone group and more so in the combination group, compared to vehicle. As expected, darolutamide alone was not efficacious in this hormone insensitive model. Nine out of 10 mice showed disease control (CR, PR or SD) in the combination group whereas no animals showed disease control in either of the monotherapy groups. This difference was significant by Fisher’s exact test analysis. Treatments were well tolerated with no significant changes in body weight in any of the treatment groups. Using the tumor dissociation kit Miltenyi individual tumor cells were isolated from darolutamide treated and untreated 22Rv1 xenograft tumors. FACS analysis showed a 50fold increase in PSMA expression in the darolutamide treated 22Rv1 tumors compared to vehicle treated animals. These data indicate that darolutamide induces PSMA expression in the hormone independent 22Rv1 model, which may have contributed to the stronger efficacy observed when combined with PSMA-TTC. Altogether these results support the further evaluation of darolutamide combination with PSMA radionuclides. Citation Format: Christoph Schatz, Urs Hagemann, Sabine Zitzmann-Kolbe, Bernard Haendler, Hartwig Hennekes, Stefanie Hammer, Arne Scholz. Darolutamide potentiates the antitumor efficacy of a PSMA-targeted thorium-227 conjugate (PSMA-TTC) in a hormone-independent prostate cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3311.

Methionine Restriction: Ready for Prime Time in the Cancer Clinic?

Attempts to selectively starve cancers in the clinic have been made at least since the time of Warburg beginning 100 years ago. Calorie-restriction or low-carbohydrate diets have had limited success with cancer patients. Methionine restriction is another strategy to selectively starve cancer cells, since cancers are addicted to methionine, unlike normal cells. Methionine addiction of cancer is termed the Hoffman effect. Numerous preclinical studies over the past half century have shown methionine restriction to be highly effective against all major cancer types and synergistic with chemotherapy. Low-methionine medical diets can be effective in lowering methionine and have shown some clinical promise, but they are not palatable and thereby not sustainable. However, selectively choosing among plant-based foods allows a variety of low-methionine diets that are sustainable. Our laboratory has developed a methioninase that can be administered orally as a supplement and has resulted in anecdotal positive results in patients with advanced cancer, including hormone-independent prostate cancer, and other recalcitrant cancers. The question is whether methionine restriction through a low-methionine diet, or even greater methionine restriction with methioninase in combination with a low-methionine diet, is ready for prime time in the clinic, especially in combination with other synergistic therapy. The question will hopefully be answered in the near future, especially for advanced cancer patients who have failed all standard therapy.

Vaccinium myrtillus L. extract and its native polyphenol-recombined mixture have anti-proliferative and pro-apoptotic effects on human prostate cancer cell lines.

Vaccinium myrtillus berry extract (VME) and a recombined standard mixture (RSM) of its main native phenolic compounds were investigated for cell growth inhibition and pro-apoptotic activity on hormone-dependent (LNCaP) and hormone-independent (PC3 and DU-145) prostate cancer (PCa) cell lines. Normal prostate epithelial cells (PrEC) were also studied in comparison. VME hindered anchorage-dependent PCa cell proliferation in a dose-dependent manner, that is, at 1/800 (v/v) dilution for LNCaP and PC3, and 1/100 (v/v) dilution for DU-145 (corresponding to 14.15 and 113.2 μg cyanidin-3-O-glucoside equivalents per ml of culture medium), respectively. VME had a growth inhibitory effect towards PrEC at the same dilution of DU-145 cells although the IC50 values indicated that PrEC are more resistant than PCa cell lines. VME also reduced the anchorage-independent growth of PCa cells. The study of the apoptotic profile (i.e., non-apoptotic, early apoptotic, late apoptotic and necrotic cells) evidenced that the apoptotic rate (early+late) was statistically higher in all three cell lines exposed to VME compared to control. Anchorage-dependent and anchorage-independent growth inhibition of RSM was very similar to that displayed by VME. Moreover, RSM exerted its growth inhibitory effect also under hypoxia, the latter representing a biological condition known to sustain PCa proliferation and aggressiveness.

Differential expression of microRNA-218 in hormone-dependent and hormone-independent prostate cancer cell lines

Objective To verify and analyze the expression of microRNA-218 in hormone-dependent and hormone-independent prostate cancer cell lines. Methods Specific SYBR Green quantitative real-time polymerase chain reaction(RT-PCR) was used to detect the relative expression of microRNA-218 in hormone-dependent prostate cancer LNCaP cell line and hormone-independent prostate cancer C4-2, PC-3 and DU-145 cell lines, and the differences were verified and analyzed. Results The expression of MicroRNA-218 was not different in C4-type, PC-3 and DU-145 three hormone-independent prostate cancer cell lines(P>0.05), but was significantly higher than that in hormone-dependent prostate cancer cell line LNCaP(P<0.05). Conclusions MicroRNA-218 is involved in the progression from steroid-dependent to hormone-independent prostate cancer and is expected to become a biomarker for predicting the progression of prostate cancer. Key words: Prostatic Neoplasms; Cell Line; MicroRNAs

Effect of polyunsaturated fatty acids on proliferation and survival of prostate cancer cells.

Progression of prostate cancer to lethal forms is marked by emergence of hormone-independent proliferation of the cancer cells. Nutritional and epidemiological studies have indicated that prostate cancer progression is correlated with the consumption of polyunsaturated fatty acids (PUFA). To shed additional light on the cell-level mechanisms of the observed correlation, we compared the sensitivity of hormone-dependent and hormone-independent prostate cancer cells to growth medium supplementation with free PUFAs in a cell proliferation and viability assay. Our data show that the hormone-dependent cells are comparatively insensitive to various PUFAs, at the same time as the growth and viability of hormone-independent cells lines are strongly inhibited by most of the tested PUFAs, whether n–3 or n–6. We speculate that this difference may be at least partially responsible for the observed effects of specific dietary lipids in prostate cancer. The new data strengthen the case for dietary intervention as part of potential new therapeutic strategies seeking to impede prostate cancer progression.

Abstract A009: Forty-three week follow-up of a phase 1a clinical trial of a PSA, IL-2, GM-CSF containing prostate cancer therapeutic vaccine in PSA defined biochemical recurrent prostate cancer patients

Abstract While progress has occurred in both cellular and immune checkpoint therapy, the benefit of therapeutic cancer vaccines has been difficult to demonstrate. Prostate cancer may be an exception with the modest activity of Sipuleucel T. We have developed a potentially low cost and easy to administer therapeutic vaccine with the combination of tumor antigen (PSA) and biologic adjuvants (IL2 and GM-CSF). This study is a phase 1a clinical trial of a PSA/IL-2/GM-CSF vaccine in biochemically recurrent hormone-naïve and hormone-independent prostate cancer patients. Major inclusion criteria include adenocarcinoma of the prostate, rising serum PSA and no measurable disease. Phase 1a examines the rate of serious adverse events (SAEs) and dose limiting adverse events (DLAEs) in an initial course of 6 vaccinations (“induction vaccination”). Twenty patients enrolled and nineteen patients completed all six intradermal injections (one patient received 5 vaccines, missed week 11 vaccine) of the PSA/IL-2/GM-CSF vaccine at weeks 1, 2, 3, 7, 11 and 15. None of the patients vaccinated in the phase 1a portion had an SAE or DLAE with the most common AE relating to grade 1 injection site reactions. Fifteen of the 18 patients who received vaccines had immune responses to PSA as demonstrated in a lymphocyte blastogenesis assay by week 31. Interestingly, after vaccination 14 of 20 patients had an increase in the doubling time of their serum PSA, suggesting a slowing of the growth of the prostate cancer. Five of 20 patients have progressed (3 PSA progression and 2 radiologic progression) at 43 weeks’ follow-up. Citation Format: Jonathan F. Head, Gregory A. Daniels, Michelle McKinney, Jessica Wang-Rodriguez. Forty-three week follow-up of a phase 1a clinical trial of a PSA, IL-2, GM-CSF containing prostate cancer therapeutic vaccine in PSA defined biochemical recurrent prostate cancer patients [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A009.

Reserpine Induces Apoptosis and Cell Cycle Arrest in Hormone Independent Prostate Cancer Cells through Mitochondrial Membrane Potential Failure.

Reserpine, an indole alkaloid commonly used for hypertension, is found in the roots of Rauwolfia serpentina. Although the root extract has been used for the treatment of cancer, the molecular mechanism of its anti-cancer activity on hormonal independent prostate cancer remains elusive. we evaluated the cytotoxicity of reserpine and other indole alkaloids, yohimbine and ajmaline on Prostate Cancer cells (PC3) using MTT assay. We investigated the mechanism of apoptosis using a combination of techniques including acridine orange/ethidium bromide staining, high content imaging of Annexin V-FITC staining, flow cytometric quantification of the mitochondrial membrane potential and Reactive Oxygen Species (ROS) and cell cycle analysis. Our results indicate that reserpine inhibits DNA synthesis by arresting the cells at the G2 phase and showed all standard sequential features of apoptosis including, destabilization of mitochondrial membrane potential, reduced production of reactive oxygen species and DNA ladder formation. Our in silico analysis further confirmed that indeed reserpine docks to the catalytic cleft of anti-apoptotic proteins substantiating our results. Collectively, our findings suggest that reserpine can be a novel therapeutic agent for the treatment of androgen-independent prostate cancer.

MiR-29a affects the biological behavior by regulating HuR in prostate cancer cells

Objective To investigate regulation of human antigens R(HuR) by miR-29a in prostate cancer and affect cell proliferation, migration, invasion and apoptosis. Methods The expression levels of miR-29a, HuR mRNA and protein between normal prostate epithelial RWPE-1 cells and hormone independent prostate cancer PC-3 cells were detected by qRT-PCR and Western blot. The expressions of miR-29a, HuR mRNA and protein were detected again after transfected with miR-29a mimics, inhibitor and negative control(NC) of PC-3 cells for 48 h. The cell proliferation kit (CCK-8), migration and invasion assay (Transwell chamber) and Flow Cytometry were used to detect the change of PC-3 cells on proliferation, migration, invasion and apoptosis after transfection. Results Compared with RWPE-1 cells, miR-29a expression was down-regulated and HuR mRNA and protein were up-regulated in PC-3 cells(P<0.05). Compared with NC, there was no change in HuR mRNA expression, but HuR protein was changed after transfected with miR-29a mimics or inhibitor(P<0.05). MiR-29a had the function of inhibit cell proliferation, migration and invasion, and promote apoptosis(P<0.05). Conclusions MiR-29a regulates the expression of HuR protein in PC-3 cells, which may affect cell proliferation, migration, invasion and apoptosis. Key words: Prostatic Neoplasms; MicroRNAs; Antigens

Abstract CT061: Interim results of a phase Ia clinical trial of a PSA, IL-2, GM-CSF containing prostate cancer therapeutic vaccine in PSA defined biochemical recurrent prostate cancer patients

Abstract While progress has occurred in both cellular and immune checkpoint therapy, the benefit of therapeutic cancer vaccines has been difficult to demonstrate. Prostate cancer may be an exception with the modest activity of sipuleucel-T. We have developed a potentially lower cost and easy to administer therapeutic vaccine with the combination of tumor antigen (PSA) and biologic adjuvants (IL-2 and GM-CSF). This study is a Phase 1a clinical trial of a PSA/IL-2/GM-CSF vaccine in 20 biochemically recurrent hormone-naïve and hormone-independent prostate cancer patients. Major inclusion criteria include adenocarcinoma of the prostate, rising serum PSA and no measurable disease. Phase 1a examines the rate of serious adverse events (SAEs) and dose limiting adverse events (DLAEs) in an initial course of 6 vaccinations (“induction vaccination”). Twenty patients enrolled and nineteen patients completed all six intradermal injections (one patient received 5 vaccines, missed week 11 vaccine) of the PSA/IL-2/GM-CSF vaccine at weeks 1, 2, 3, 7, 11 and 15. None of the patients vaccinated in the Phase 1a portion had a SAE or DLAE with the most common AE relating to grade 1 injection site reactions. Fifteen of the 18 patients who received vaccines had immune responses to PSA as demonstrated in a lymphocyte blastogenesis assay by week 31. Interestingly, after vaccination 14 of 20 patients had an increase in the doubling time of their serum PSA, suggesting a slowing of the growth of the prostate cancer. Four of 20 patients have progressed (3 PSA progression and 1 radiological progression) at 31 weeks follow-up. Citation Format: Jonathan F. Head, Gregory A. Daniels, Michelle A. McKinney, Weg M. Ongkeko, Kyoko Sakamoto, Jessica Wang-Rodriguez. Interim results of a phase Ia clinical trial of a PSA, IL-2, GM-CSF containing prostate cancer therapeutic vaccine in PSA defined biochemical recurrent prostate cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT061.

In Vivo Study of the Effects of ERβ on Apoptosis and Proliferation of Hormone-Independent Prostate Cancer Cell Lines PC-3M.

Objective To evaluate the in vivo therapeutic effects of attenuated Salmonella carrying PCDNA3.1-ERβ plasmid in hormone-independent prostatic cancer in nude mice and to clarify the mechanism by which estrogen receptor β (ERβ) induces apoptosis and proliferation in prostatic cancer cells in mice. Methods The orthotopic prostatic cancer models of mice were randomly divided as follows: MOCK group, treated with PBS, PQ group, treated with attenuated Salmonella alone, PQ-PCDNA3.1 group, treated with attenuated Salmonella carrying PCDNA3.1 plasmid, and PQ-PCDNA3.1-ERβ group, treated with the attenuated Salmonella carrying PCDNA3.1-ERβ plasmid. Then, 10 μl of the plasmid-containing solution, comprising 1 × 107 cfu of the bacteria, was administered via intranasal delivery to each group except the MOCK group. The experimental methods included flow cytometry and terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling (TUNEL) assay, immunohistochemistry, and western blotting. Results Compared with the MOCK, PQ, and PQ-PCDNA3.1 groups, the weights of tumors in the PQ-PCDNA3.1-ERβ group were significantly reduced. The results of flow cytometry and TUNEL assay revealed that the number of apoptotic cells in the PQ-PCDNA3.1-ERβ group significantly increased. Compared with PQ-PCDNA3.1 group, the protein expression levels of ERβ, Bad, p-caspase 9, p-caspase 3, and cleaved PARP in the PQ-PCDNA3.1-ERβ group were significantly increased, while the expression levels of Akt, p-Akt, and Bcl-xl were decreased (P < 0.05). Conclusion The attenuated Salmonella carrying PCDNA3.1-ERβ plasmid could inhibit the growth of orthotopic prostatic cancer in mice by increasing the expression of ERβ.

Maspin Enhances the Anticancer Activity of Curcumin in Hormone-refractory Prostate Cancer Cells.

Androgen deprivation therapy remains the principal treatment for patients with advanced prostate cancer, though, most patients will eventually develop hormone-refractory prostate cancer (HRPC). Androgen ablation mediated maspin-induction has been identified in cancer patients. However, the role of maspin on the anticancer activity of curcumin derived from turmeric (Curcuma longa) in HRPC cells has not been elucidated. The anticancer action of curcumin in hormone-independent prostate cancer cells (DU145, and PC-3) was determined by measures of cell survival rate. The cause of maspin silencing on the anti-tumor abilities of curcumin in PC-3 cells was evaluated by measures of cell survival rate, cell-cycle distribution, and apoptosis signaling analysis. Our present study showed that PC-3 cells (with higher maspin expression) were more sensitive than DU145 cells to curcumin treatment (with lower maspin expression). RNA interference-mediated maspin silencing reduced curcumin sensitivity of PC-3 cells, as evidenced by reduced apoptotic cell death. After exposure to curcumin, maspin-knockdown cells showed lower expression levels of pro-apoptotic proteins, Bad and Bax, as compared with control cells. Maspin can enhance the sensitivity of HRPC cells to curcumin treatment.

Clinical efficacy of combined 125I brachytherapy and intermittent androgen deprivation for locally mediate-high risk prostate cancer

Objective To evaluate the clinical efficacy of combined 125I brachytherapy and intermittent androgen deprivation for locally mediate-high risk prostate cancer. Methods A total of 25 patients with prostate cancer ranging from 64 to 85 years old (average age of 75) were recruited. The PSA level of these patients was 10.3~354.8 ng/mL, and the Gleason score was 7~9. All patients were clinically staged as T2~T3N0M0. Under continual epidural anesthesia in the lithotomy position, these patients underwent transrectal ultrasound scans from the basement of the prostate to the apex. Pictures were transmitted to the computer system to undergo three-dimensional reconstruction of the prostate and intra-operational planning. According to the plan, patients received 125I brachytherapy under the guidance of the transrectal ultrasound. All patients underwent maximal androgen blockage (MAB) therapy after surgery. Treatment was stopped when PSA fell to 0 ng/mL and stabilized for 2 months. The criterion for the resumption of hormonal therapy was a continuously increasing PSA level as detected in 3 consecutive tests. Results All 25 patients completed the surgery without complications. The number of implanted seeds was 85~110, with an average of 93. The follow-up period was 8~20 months, with an average of 12 months. One case was diagnosed with bone metastasis 10 months after the surgery. Within the 3 to 6 months after surgery, all the PSA levels fell below the normal level. Ten cases did not reach 0 ng/mL, so they continued the hormonal therapy. Five cases had increasing PSA levels 5~16 months after surgery, so MAB was restarted. After that, the PSA levels decreased to 0 ng/mL within 3~6 months. Two cases changed into hormone independent prostate cancer and bone metastasis occurred in these patients. At the end of the follow up period, the remaining 17 patients' PSA level was 0~1.2 ng/mL, and 10 patients of them had a PSA level less than 0.2 ng/mL. Early complications included mild to moderate urethral irritation (24%, 6/25), acute urine retention (8%, 2/25) and rectal irritation or bloody stool (16%, 4/25). Conclusions The combination of intermittent androgen deprivation and 125I brachytherapy is an effective and safe treatment for locally advanced prostate cancer. Key words: Prostatic Neoplasms; Iodine

HMGB1-mediated autophagy confers resistance to gemcitabine in hormone-independent prostate cancer cells.

As a main treatment of prostate cancer, castration therapy has been widely applied in the clinic. However, the therapeutic strategy for hormone-independent prostate cancer (HIPC) was not satisfied. Gemcitabine is an important chemotherapeutic agent that has been approved for the treatment of numerous human solid tumors, including HIPC, whereas the gemcitabine resistance has become a serious problem in clinical chemotherapy. In the present study, the mechanisms of resistance to gemcitabine were investigated in HIPC cell lines. The results demonstrated that the autophagy markers were induced significantly in HIPC cells subsequent to gemcitabine treatment. Meanwhile, administration of gemcitabine to HIPC cells increased the expression of high mobility group box1 (HMGB1). Furthermore, the gemcitabine-induced autophagy response was attenuated in stable HIPC cells harboring HMGB1 shRNA. Notably, the HIPC cells stably transfected with HMGB1 shRNA or treated with autophagy inhibitors were more sensitive to gemcitabine compared with the control group. These data suggested that inhibition of HMGB1 increased the sensitivity to gemcitabine by decreasing autophagy response in HIPC cells. Overall, the present findings demonstrate a new mechanism for the resistance to gemcitabine in HIPC cell lines.

Carnosol inhibits Hedgehog signaling pathway in both LNCaP and DU145 prostate cancer cell lines

To investigate the effect of carnosol on the Hedgehog (HH) signaling pathway in human hormone-dependent prostate cancer cell line LNCaP and hormone-independent prostate cancer cell line DU145. The expression levels of glioma-associated oncogene homolog 1 (Gli1) and Sonic hedgehog (Shh) in human prostate cancer tissues were detected by immunohistochemistry. After treated with carnosol (0.25-16 μmol/L), the cell survival of LNCaP and DU145 cells were detected by MTT assay. The expression levels of Gli1 and Shh mRNA and protein in the two cells were detected by qRT-PCR and western blot, respectively. The apoptosis was determined by the caspase-3 activity assay. Results showed that Shh and Gli1 were upregulated in cancer tissues. The inhibitory effect of carnosol on cell survival was enhanced with concentration, suggesting both LNCaP and DU145 cells were sensitive to carnosol. The inhibitory effects of carnosol on Gli1 and Shh mRNAs in the hormone-dependent LNCaP prostate cancer cell was stronger than that in the hormone-independent DU145 prostate cancer cells. Carnosol downregulated the expression of Gli1 in nucleus, and Shh in cells. Greater carnosol concentration resulted in lower levels of Gli1 and Shh. Carnosol increased caspase-3 activity in a dose-dependent manner, suggesting that carnosol promotes cell apoptosis. Thus, carnosol can inhibit the proliferation and induce the apoptosis of prostate cancer cells in vitro, and its mechanism might be associated with the inhibiting of HH signaling pathway. Although the inhibitory effect of carnosol on hormone-dependent LNCaP prostate cancer cells is stronger than hormone-independent DU145 prostate cancer cells, carnosol might be a potential drug for hormone-independent prostate cancer.

Abstract 176: Early development of GMC1, a novel molecule targeting FKBP52 for the treatment of hormone-refractory prostate cancer

Abstract Purpose: GMC1 directly inhibits FKBP52, effectively blocking androgen receptor dependent gene expression and androgen-stimulated proliferation. This make it an attractive option for the treatment of hormone-dependent and hormone-independent prostate cancer. This study investigated an analytical method for GMC1 quantification, pre-formulation characteristics of GMC1, and developed intravenous formulations for the evaluation of GMC1 in animal models. Method: An LC/MS/MS method for the quantification of GMC1 in solution, plasma and urine was developed, validated and applied to the determination of the stability, log P, plasma protein binding and solubility of GMC1 in various solvents. Liposomal formulations and co-solvent systems with various ratios of high capacity vehicles were formulated and the optimal formulation applied, at 2 mg/kg single IV bolus dose, to the pharmacokinetic study of GMC1 in a rat model. Result: The intra- and inter-day accuracy (%RE) and precision (%CV) of the LC/MS/MS method ranged from 1.6 – 11.7 % and 1.4 – 8.8 %, respectively. GMC1 is stable in solid and solution state, moderately lipophilic (log P = 1.38 ± 0.05), poorly water soluble (0.4 ± 0.01 mg/mL), and highly plasma protein bound (&amp;gt;71%). The optimal formulation consisting of PEG 300 and Labrasol ® (1:1, v/v) allowed us to achieve a GMC1 concentration of 10 mg/mL, and tolerated an aqueous environment. GMC1 has a tri-exponential disposition with a Cmax of 7.6 ± 1.97 mg/L, clearance of 0.53 L/kg/hr, α-distribution, β-phase and terminal elimination half-lives of 0.1 ± 0.04 hr, 1.2 ± 0.34 hr, and 19.7 ± 5.09 hr respectively. Conclusion: The LC/MS/MS method, formulations and pharmacokinetic study can be applied to the pre-clinical and clinical development of GMC1. Grant Support: This work was performed under funding from NIH/NIGMS grant (5SC3GM102018) and NIH/NIMHD/RCMI grant (5G12MD007605). Citation Format: Huan Xie, Oscar Ekpenyong. Early development of GMC1, a novel molecule targeting FKBP52 for the treatment of hormone-refractory prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 176. doi:10.1158/1538-7445.AM2017-176

New gonadotropin-releasing hormone glycolipids with direct antiproliferative activity and gonadotropin-releasing potency

Gonadotropin-releasing hormone (GnRH) is an endogenous peptide with a short biological half-life. Although GnRH analogs (eg. triptorelin) are developed with enhanced stability compared to the native peptide, they still suffer from poor biological stability and pharmacokinetic properties. Furthermore, they are only effective in the treatment of hormone-dependent reproductive cancers. In this study we applied lipidation and glycosylation along with D-amino acid substitution at position 6 (D-Trp 6 ) to improve the stability, permeability, and consequently the potency of the GnRH peptide and triptorelin. We showed that the conjugation of GnRH with a lipid moiety and carbohydrates made all modified constructs ( 1– 8 ) more stable than the parent peptide against enzymatic degradation (5.5–6.5 times). Two of the lactose-modified glycolipopeptides, 3 and 6 , showed 27 and 16 times higher membrane permeability than the parent GnRH, respectively. All analogs with D-Trp 6 -substitution ( 4–6 ) exerted GnRH receptor-mediated antiproliferative activity in prostate and ovarian GnRH-receptor positive cell lines. They were more potent than triptorelin in the hormone-independent prostate cancer cell line: DU145. Compound 6 (lactose-modified) was the most potent analog for stimulating the release of luteinizing hormone (LH) and follicle stimulating hormone (FSH) gonadotropins from rat pituitary cells in vitro . The same glycolipopeptide exhibited a higher efficacy and duration of action in stimulating the release of LH than triptorelin in a preclinical mouse model. The superior activity of lipid- and carbohydrate-substituted triptorelin analog 6 made it a promising candidate for the development of new GnRH agonists to treat both hormone-dependent and hormone-refractory prostate cancer.

Oridonin induces G2/M cell cycle arrest and apoptosis via the PI3K/Akt signaling pathway in hormone-independent prostate cancer cells.

Oridonin is an active constituent isolated from the traditional Chinese herb Rabdosia rubescens, which exerts antitumor effects in experimental and clinical settings. However, its antitumor effects and underlying mechanisms on prostate cancer cells have not yet been clearly identified. In the present study, the androgen-independent prostate cancer PC3 and DU145 cell lines were used as models to investigate the effects and possible mechanisms of oridonin on cellular proliferation and apoptosis. Results demonstrated that oridonin inhibited cellular proliferation, and was able to significantly induce G2/M cell cycle arrest and apoptosis. Detailed signaling pathway analysis by western blotting demonstrated that the expression levels of p53 and p21 were upregulated, whereas the expression of cyclin-dependent kinase 1 was downregulated following oridonin treatment, which led to cell cycle arrest in the G2/M phase. Oridonin also upregulated the proteolytic cleaved forms of caspase-3, caspase-9 and poly (ADP-ribose) polymerase. Furthermore, the protein expression levels of B-cell lymphoma 2 were decreased and those of Bcl-2-associated X protein were increased following oridonin treatment. In addition, oridonin treatment significantly inhibited the expression of phosphoiniositide-3 kinase (PI3K) p85 subunit and the phosphorylation of Akt. The downstream gene murine double minute 2 was also downregulated, which may contribute to the elevated expression of p53 following oridonin treatment. In conclusion, the results of the present study suggested that oridonin is able to inactivate the PI3K/Akt pathway and activate p53 pathways in prostate cancer cells, resulting in the suppression of proliferation and the induction of caspase-mediated apoptosis.

Folate-targeted nanoparticle delivery of androgen receptor shRNA enhances the sensitivity of hormone-independent prostate cancer to radiotherapy

Androgen receptor (AR) plays a crucial role in the development and progression of prostate cancer (PCa). PCa patients typically receive androgen deprivation therapy; nonetheless, these patients eventually develop castration and radiation resistance. We hypothesized that we could further improve radiotherapeutic efficacy of hormone-independent PCa (HIPC) by silencing AR. In this study, nanoparticle (NP) AR-shRNA was formulated using folate-targeted H1 nanopolymer. We demonstrated that NP AR-shRNA enhances PCa radiosensitivity as indicated by the inhibition of cell growth, increased apoptosis, and increased cell cycle arrest in AR-dependent HIPC in vitro. The radiosensitizing effect of NP AR-shRNA could be validated in vivo, as NP AR-shRNA significantly suppressed tumor growth and prolonged the survival of HIPC tumor-bearing mice. Analysis at the molecular level revealed that NP AR-shRNA inhibits DNA damage repair signaling pathways. Our study supports further investigation of NP AR-shRNA for the improvement of radiotherapy efficacy in HIPC.