Utilizing RNA nanotechnology to construct negatively charged and ultrasound-responsive nanodroplets for targeted delivery of siRNA.

Ultrasound nanodroplets (NDs) have been reported as a promising nanocarrier for siRNA delivery depending on its unique strengths of sonoporation. Presently, common means for NDs-mediated siRNA delivery is through electrostatic interaction, but challenges like cationic toxicity still exist. In this study, we demonstrated a novel strategy to construct negatively charged and ultrasound (US)-responsive O-carboxymethyl chitosan (O-CMS) NDs as a siRNA targeted delivery system through three-way junction of bacteriophage phi29 DNA packaging motor (3WJ-pRNA) nanotechnology. 39nt A10-3.2 aptamer targeting prostate specific membrane antigen (PSMA) and 21nt siRNA against cationic amino acid transporter 1 (siCAT-1) were annealed to 3WJ-pRNA scaffold via complementation with an extended sequence. The cholesterol molecule attached to one branch facilitates the 3WJ-pRNA nanoparticles anchoring onto NDs. The desired O-CMS NDs with siRNA-loading and RNA-aptamer modification (A10-3.2/siCAT-1/3WJ-NDs) were successfully prepared, which were with spherical shapes, core-shell structures and uniform in sizes (198 nm with PDI 0.3). As a main proportion of shell, O-CMC showed a certain anti-tumor effects. In vitro studies demonstrated that A10-3.2/siCAT-1/3WJ-NDs exhibited good contrast-enhanced US imaging, buffering capacity and high bio-safety, were able to deliver siCAT-1 to PSMA-overexpressed prostate cancer cells under US irradiation, thus silence the CAT-1 expression, and consequently suppressing 22RV1 cell proliferation and migration. Taken overall, our findings provide a promising strategy to develop negatively charged and US-responsive NDs for tumor-targeted siRNA delivery.

Improving power in PSA response analyses of metastatic castration-resistant prostate cancer trials.

BACKGROUND: To determine how much an augmented analysis approach could improve the efficiency of prostate-specific antigen (PSA) response analyses in clinical practice. PSA response rates are commonly used outcome measures in metastatic castration-resistant prostate cancer (mCRPC) trial reports. PSA response is evaluated by comparing continuous PSA data (e.g., change from baseline) to a threshold (e.g., 50% reduction). Consequently, information in the continuous data is discarded. Recent papers have proposed an augmented approach that retains the conventional response rate, but employs the continuous data to improve precision of estimation. METHODS: A literature review identified published prostate cancer trials that included a waterfall plot of continuous PSA data. This continuous data was extracted to enable the conventional and augmented approaches to be compared. RESULTS: Sixty-four articles, reporting results for 78 mCRPC treatment arms, were re-analysed. The median efficiency gain from using the augmented analysis, in terms of the implied increase to the sample size of the original study, was 103.2% (IQR [89.8,190.9%]). CONCLUSIONS: Augmented PSA response analysis requires no additional data to be collected and can be performed easily using available software. It improves precision of estimation to a degree that is equivalent to a substantial sample size increase. The implication of this work is that prostate cancer trials using PSA response as a primary endpoint could be delivered with fewer participants and, therefore, more rapidly with reduced cost.

Anti-androgen for myoepithelial tumor: a potent therapy yet a potential misleader.

Myoepithelial tumor is a rare form of cancer, mainly arising from the salivary glands and extremities. Due to its rarity, no formal treatment guidelines exist. Here we report a case of a male patient diagnosed with metastatic myoepithelial tumor which was successfully treated with an androgen-receptor (AR) antagonist (bicalutamide), based on the results of molecular testing. Six years after the initiation of bicalutamide, patient was diagnosed with metastatic prostate cancer. To our knowledge, this is the first case described in literature that demonstrate the effectiveness of anti-androgens in treating myoepithelial tumor. Vigilance should be maintained when screening these patients for prostate cancer as their 'true' prostate specific antigen levels might be masked by the ongoing endocrine therapy.

Molecular features of exceptional response to neoadjuvant anti-androgen therapy in high-risk localized prostate cancer.

High-risk localized prostate cancer (HRLPC) is associated with a substantial risk of recurrence and disease mortality. Recent clinical trials have shown that intensifying anti-androgen therapies administered before prostatectomy can induce pathologic complete responses or minimal residual disease, called exceptional response, although the molecular determinants of these clinical outcomes are largely unknown. Here, we perform whole-exome and transcriptome sequencing on pre-treatment multi-regional tumor biopsies from exceptional responders (ERs) and non-responders (NRs, pathologic T3 or lymph node-positive disease) to intensive neoadjuvant anti-androgen therapies. Clonal SPOP mutation and SPOPL copy-number loss are exclusively observed in ERs, while clonal TP53 mutation and PTEN copy-number loss are exclusively observed in NRs. Transcriptional programs involving androgen signaling and TGF-ß signaling are enriched in ERs and NRs, respectively. These findings may guide prospective validation studies of these molecular features in large HRLPC clinical cohorts treated with neoadjuvant anti-androgens to improve patient stratification.

Lowering and Stabilizing PSA Levels in Advanced-prostate Cancer Patients With Oral Methioninase.

BACKGROUND/AIM: Methionine addiction is a general and fundamental hallmark of cancer due to the excess use of methionine for transmethylation reactions, termed the "Hoffman Effect". Methionine addiction has been shown to be a highly-effective target for cancer therapy by methionine restriction with oral recombinant methioninase (o-rMETase) in preclinical studies, including patient- derived orthotopic xenograft (PDOX) mouse models of cancer. A clinical study of o-rMETase as a supplement showed a 70% reduction of PSA levels in a patient with bone-metastatic prostate cancer. MATERIALS AND METHODS: In the present study, two advanced prostate-cancer patients took o-rMETase as a supplement for approximately one month. RESULTS: One of the patients taking o-rMETase showed a 38% reduction of PSA levels and the second patient showed a 20% PSA reduction. CONCLUSION: o-rMETase shows promise for treating patients with advanced prostate cancer.

A prostate-specific membrane antigen (PSMA)-targeted prodrug with a favorable in vivo toxicity profile.

Prostate-specific membrane antigen (PSMA) is a promising target for the treatment of advanced prostate cancer (PC) and various solid tumors. Although PSMA-targeted radiopharmaceutical therapy (RPT) has enabled significant imaging and prostate-specific antigen (PSA) responses, accumulating clinical data are beginning to reveal certain limitations, including a subgroup of non-responders, relapse, radiation-induced toxicity, and the need for specialized facilities for its administration. To date non-radioactive attempts to leverage PSMA to treat PC with antibodies, nanomedicines or cell-based therapies have met with modest success. We developed a non-radioactive prodrug, SBPD-1, composed of a small-molecule PSMA-targeting moiety, a cancer-selective cleavable linker, and the microtubule inhibitor monomethyl auristatin E (MMAE). SBPD-1 demonstrated high binding affinity to PSMA (Ki = 8.84 nM) and selective cytotoxicity to PSMA-expressing PC cell lines (IC50 = 3.90 nM). SBPD-1 demonstrated a significant survival benefit in two murine models of human PC relative to controls. The highest dose tested did not induce toxicity in immunocompetent mice. The high specific targeting ability of SBPD-1 to PSMA-expressing tumors and its favorable toxicity profile warrant its further development.

Antihormone treatment differentially regulates PSA secretion, PSMA expression and 68Ga-PSMA uptake in LNCaP cells.

BACKGROUND: In recent years, a variety of innovative therapeutics for castration-resistant prostate cancer have been developed, including novel anti-androgenic drugs, such as abiraterone or VPC-13566. Therapeutic monitoring of these pharmaceuticals is performed either by measuring PSA levels in serum or by imaging. PET using PSMA ligands labeled with Fluor-18 or Gallium-68 is the most sensitive and specific imaging modality for detection of metastases in advanced prostate cancer. To date, it remains unclear how PSMA expression is modulated by anti-hormonal treatment and how it correlates with PSA secretion. METHODS: We analyzed modulation of PSMA-mRNA and protein expression, 68Ga-PSMA uptake and regulation of PSA secretion by abiraterone or VPC-13566 in LNCaP cells in vitro. RESULTS: We found that abiraterone and VPC-13566 upregulate PSMA protein and mRNA expression but block PSA secretion in LNCaP cells. Both anti-androgens also enhanced 68Ga-PSMA uptake normalized by the number of cells, whereas abiraterone and VPC-13566 reduced 68Ga-PSMA uptake in total LNCaP monolayers treated due to cell death. CONCLUSION: Our data indicate that PSA secretion and PSMA expression are differentially regulated upon anti-androgen treatment. This finding might be important for the interpretation of 68Ga-PSMA PET images in monitoring therapies with abiraterone and VPC-13566 in prostate cancer patients, but needs to be validated in vivo.

Discovery of a novel AR/HDAC6 dual inhibitor for prostate cancer treatment.

Androgen receptor (AR) and histone deacetylase 6 (HDAC6) are important targets for cancer therapy. Given that both AR antagonists and HDAC6 inhibitors modulate AR signaling, a novel AR/HDAC6 dual inhibitor is investigated for its anticancer effects in castration-resistant prostate cancer (CRPC). Zeta55 inhibits nuclear translocation of AR and suppresses androgen-induced PSA and TMPRSS2 expression. Meanwhile, Zeta55 selectively inhibits HDAC6 activity, leading to AR degradation. Zeta55 reduces the growth of AR-overexpressing VCaP prostate cancer cells both in vitro and in a CRPC xenograft model. These results provide preclinical proof of principle for Zeta55 as a promising therapeutic in prostate cancer treatment.

PSA response to antiandrogen withdrawal: a systematic review and meta-analysis.

BACKGROUND: Antiandrogen withdrawal (AAW) response is the paradoxical decrease in prostate-specific antigen (PSA) following the withdrawal of antiandrogen in patients with advanced prostate cancer. Currently, the reported literature on the proportion of patients exhibiting AAW response and the differences in PSA response between the types of antiandrogens is unclear. METHODS: This review aimed to explore the PSA response to AAW and to identify if the response depends on the type of antiandrogens. A literature search was performed using databases PubMed, Cochrane and EMBASE with a cut-off date of 23rd of November 2020. Studies reporting on outcomes of AAW and prostate cancer were included. Studies were screened by two reviewers and relevant data extracted. Meta-analysis of outcomes was reported using random-effects and fixed-effects model. A subgroup analysis was performed for type of antiandrogen. RESULTS: From 450 studies, 23 were included with a total of 1474 patients with advanced prostate cancer were available for further analysis. Overall, 395 (26%) patients had any reduction in PSA levels (95% CI: 20-32%) and 183 (11%) patients had a ≥50% reduction in PSA levels (95% CI: 6-16%). Among the 1212 patients on first-generation antiandrogens, 30% (95% CI: 23-38%) had any PSA decline with 15% patients having a ≥50% PSA decline (95% CI: 8-22%). In contrast, among the 108 patients on second-generation antiandrogens, 7% (95% CI: 0-13%) had any PSA decline and only 1% (95% CI: 0-5%) had a ≥50% PSA decline. Also, among the 154 patients on androgen synthesis inhibitors, 26% (95% CI: 19-33%) had any PSA decline and only 4% (95% CI: 0-13%) had a ≥50% PSA decline. CONCLUSIONS: One-fourth of patients treated with AAW show a PSA response. However, PSA response to AAW is uncommon with second-generation antiandrogens and androgen synthesis inhibitors. Further research is required to understand the differences in response between the types of antiandrogen.

In situ Generated 212Pb-PSMA Ligand in a 224Ra-Solution for Dual Targeting of Prostate Cancer Sclerotic Stroma and PSMA-positive Cells.

BACKGROUND: New treatments combating bone and extraskeletal metastases are needed for patients with metastatic castration-resistant prostate cancer. The majority of metastases overexpress prostate-specific membrane antigen (PSMA), making it an ideal candidate for targeted radionuclide therapy. OBJECTIVE: The aim of this study was to test a novel liquid 224Ra/212Pb-generator for the rapid preparation of a dual-alpha targeting solution. Here, PSMA-targeting ligands are labelled with 212Pb in the 224Ra-solution in transient equilibrium with daughter nuclides. Thus, natural bone-seeking 224Ra targeting sclerotic bone metastases and 212Pb-chelated PSMA ligands targeting PSMA-expressing tumour cells are obtained. METHODS: Two PSMA-targeting ligands, the p-SCN-Bn-TCMC-PSMA ligand (NG001), specifically developed for chelating 212Pb, and the most clinically used DOTA-based PSMA-617 were labelled with 212Pb. Radiolabelling and targeting potential were investigated in situ, in vitro (PSMA-positive C4-2 human prostate cancer cells) and in vivo (athymic mice bearing C4-2 xenografts). RESULTS: NG001 was rapidly labelled with 212Pb (radiochemical purity >94% at concentrations of ≥15 µg/ml) using the liquid 224Ra/212Pb-generator. The high radiochemical purity and stability of [212Pb]Pb- NG001 were demonstrated over 48 hours in the presence of ascorbic acid and albumin. Similar binding abilities of the 212Pb-labelled ligands were observed in C4-2 cells. The PSMA ligands displayed comparable tumour uptake after 2 hours, but NG001 showed a 3.5-fold lower kidney uptake than PSMA- 617. Radium-224 was not chelated and, hence, showed high uptake in bones. CONCLUSION: A fast method for the labelling of PSMA ligands with 212Pb in the 224Ra/212Pb-solution was developed. Thus, further in vivo studies with dual tumour targeting by alpha-particles are warranted.

Oral dosing of Recombinant Methioninase Is Associated With a 70% Drop in PSA in a Patient With Bone-metastatic Prostate Cancer and 50% Reduction in Circulating Methionine in a High-stage Ovarian Cancer Patient.

BACKGROUND/AIM: Methionine addiction is a general and fundamental hallmark of cancer. Methionine addiction can be targeted by methionine restriction (MR). Our laboratory has studied methionine addiction in cancer and MR for almost 50 years. The present study describes oral recombinant methioninase (o-rMETase), as a supplement, to induce MR in cancer patients. PATIENTS AND METHODS: One patient, a 67-year-old female with high-stage ovarian cancer took o-rMETase twice a day at 250 units per dose for approximately one month. A second patient, a 76-year-old male with bone-metastatic prostate cancer, took o-rMETase twice a day at 250 units per dose during three months. RESULTS: The first patient's circulating methionine levels decreased 50% within 4 hours of taking 250 units of o-rMETase. The second patient's PSA dropped approximately 70% over 3 months. During this time the patient's hemoglobin increased. CONCLUSION: o-rMETase has no side effects and is potentially efficacious. Future studies involving larger cohorts of patients with high-stage cancer are required to determine if o-rMETase, as a supplement, can increase survival and improve the quality of life.

Baicalin alleviates benign prostate hyperplasia through androgen-dependent apoptosis.

BPH is a disease prevalent among elderly men that is characterized by abnormal proliferation of prostatic epithelial and stromal tissues. No effective treatment exists for BPH owing to lack of a clear understanding of its molecular etiology. Although several studies have reported therapeutic effects of baicalin against numerous diseases, including prostate cancer, its beneficial effects on BPH have not yet been explored. The present study investigated the therapeutic effects of baicalin on the development of BPH and its mechanism of action. We established a testosterone-treated BPH animal model and DHT-stimulated prostate cell lines, including RWPE-1 and WPMY-1. Administration of baicalin ameliorated the pathological prostate enlargement, suppressed the production of DHT, and inhibited the activity of 5α- reductase Type II in the animal model. BC exerted these effects via its anti-proliferative effects by restoring the Bax/Bcl-2 ratio, activating caspase-3 and caspase-8, and inducing the phosphorylation of AMPK. In vitro studies using DHT-stimulated prostate cells demonstrated an up-regulation of BPH-related and proliferation markers, whereas baicalin clearly reduced the overexpression of AR, PSA, PCNA, and Bcl-2. These results suggested that baicalin could suppress androgen-dependent development of BPH both in vivo and in vitro by inducing apoptosis.

Influence of regular aspirin intake on PSA values, prostate cancer incidence and overall survival in a prospective screening trial (ERSPC Aarau).

OBJECTIVES: To analyze the influence of aspirin (ASA) intake on PSA values and prostate cancer (PCa) development in a prospective screening study cohort. METHODS: 4314 men from the Swiss section of the European Randomized Study of Screening for Prostate Cancer (ERSPC) were included. A transrectal prostate biopsy was performed in men with a PSA level ≥ 3 ng/ml. Mortality data were obtained through registry linkages. PCa incidence and grade, total PSA, free-to-total PSA and overall survival were compared between ASA users and non-users. RESULTS: Median follow-up time was 9.6 years. In 789 men (18.3%) using aspirin [ASA +], the overall PCa incidence was significantly lower (6.8% vs. 9.6%, p = 0.015), but the multivariate Cox regression analysis showed no significant decrease in risk of PCa diagnosis (HR 0.84, p = 0.297). Total PSA values were significantly lower in ASA users for both baseline (1.6 vs. 1.8 ng/ml, p = 0.007) and follow-up visits (1.75 vs. 2.1 ng/ml, p < 0.001). Multivariate Cox regression analysis predicted significantly higher overall mortality risk among ASA users (HR 1.46, p = 0.009). CONCLUSIONS: In our study population, PCa incidence was significantly reduced among patients on aspirin. While we did not observe a statistically significant PCa risk reduction during the follow-up period, we found lower PSA values among ASA users compared to non-users, with a more distinct difference after 4 years of ASA intake, suggesting a cumulative effect and a potential protective association between regular ASA intake and PCa development. As for clinical practice, lowering PSA cutoff values by 0.4 ng/ml could be considered in long-term ASA users to avoid a potential bias towards delayed PCa detection.

TheraP: a randomized phase 2 trial of 177 Lu-PSMA-617 theranostic treatment vs cabazitaxel in progressive metastatic castration-resistant prostate cancer (Clinical Trial Protocol ANZUP 1603).

OBJECTIVE: To assess the activity and safety of cabazitaxel chemotherapy vs that of treatment with 177 Lu-PSMA-617, a novel radiolabelled small molecule that binds with high affinity to prostate-specific membrane antigen (PSMA), in men with metastatic castration-resistant prostate cancer (mCRPC) who have received prior docetaxel treatment. PATIENTS AND METHODS: The TheraP trial (ANZUP 1603) is an open-label, randomized, stratified, two-arm multicentre phase 2 trial comparing the activity and safety of cabazitaxel chemotherapy vs 177 Lu-PSMA-617 therapy in the treatment of men with mCRPC. Key eligibility criteria include prior docetaxel chemotherapy, rising prostate-specific antigen (PSA) level, sufficient PSMA avidity, as defined by centrally reviewed 68 Ga-PSMA-11 and fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) with no discordant FDG-avid PSMA-negative sites of disease. Patients in the control group receive standard treatment with cabazitaxel (20 mg/m2 ) i.v. every 3 weeks with prednisolone 10 mg daily orally, for a maximum of 10 cycles. Patients in the experimental group receive 177 Lu-PSMA-617 (8.5 GBq decreasing by 0.5 GBq per cycle) i.v. every 6 weeks, for up to a maximum of six cycles. In the event of an exceptional response as defined on centrally reviewed post-therapy single-photon emission CT imaging, treatment will be suspended but can recommence on progression. The trial aims to include 200 patients who will be centrally randomized to one of the two treatment groups, in a 1:1 ratio. The primary endpoint is PSA response. Secondary endpoints are overall survival, progression-free survival (PFS), radiographic PFS, PSA PFS, objective tumour response, pain response, pain PFS, health-related quality of life, and frequency and severity of adverse events. The treatment and outcomes of patients excluded on the basis of low PSMA avidity or discordant FDG-avid disease on screening 68 Ga-PSMA-11 and Fluorine-18 (18 F)-FDG-PET/CT scan will also be assessed. Enrolment in the study commenced on 29 January 2018. RESULTS AND CONCLUSIONS: 177 Lu-PSMA-617 offers a potential additional life-prolonging treatment option for men with mCRPC. The results of this trial will determine, for the first time in a randomized design, the activity and safety of 177 Lu-PSMA-617, as compared with cabazitaxel chemotherapy in men with progressive mCRPC.

Pembrolizumab in men with heavily treated metastatic castrate-resistant prostate cancer.

BACKGROUND: Pembrolizumab is approved for patients with metastatic, microsatellite instability (MSI)-high or mismatch repair-deficient (dMMR) solid tumors. However, very few men with prostate cancer were included in these initial studies. METHODS: We performed a single institution retrospective review of men with metastatic castrate-resistant prostate cancer (mCRPC) who were treated with pembrolizumab. The primary objective was to describe the clinical efficacy of pembrolizumab associated with patient and genomic characteristics. RESULTS: We identified 48 men who received ≥1 cycle of pembrolizumab for mCRPC. Of these, 94% (45/48) had ≥3 prior lines of therapy for mCRPC. Somatic tumor sequencing was available in 18/48 men (38%). We found that 17% (8/48) had a ≥50% confirmed PSA decline with pembrolizumab, and 8% (4/48) had a ≥90% PSA decline with durations of response ranging from 3.1 to 16.3 months. Two of these four men had mutations in LRP1b, one of whom also had MSH2 loss and was MSI-H and TMB-high. Despite prior progression on enzalutamide, 48% (23/48) of men were treated with concurrent enzalutamide. The median PSA progression-free-survival was 1.8 months (range 0.4-13.7 months), with 31% of patients remaining on pembrolizumab therapy and 54% of men remain alive with a median follow-up of 7.1 months. CONCLUSIONS: In a heavily pretreated population of men with mCRPC, pembrolizumab was associated with a ≥50% PSA decline in 17% (8/48) of men, including a dramatic ≥90% PSA response in 8% (4/48), two of whom harbored pathogenic LRP1b mutations suggesting that LRP1b mutations may enrich for PD-1 inhibitor responsiveness in prostate cancer.

The efficacy and safety comparison of docetaxel, cabazitaxel, estramustine, and mitoxantrone for castration-resistant prostate cancer: A network meta-analysis.

AIMS: The aim of this study was to compare the efficacy and safety of docetaxel, cabazitaxel, docetaxel + estramustine, mitoxantrone in the management of castration-resistant prostate cancer (CRPC). METHODS: Electronic databases including PubMed, Cochrance Library and Embase were searched for studies published from when the databases were established to January 1st, 2018. Randomized controlled trials (RCTs) that compared docetaxel + prednisone (DP), cabazitaxel + prednisone (CP), docetaxel + estramustine + prednisone (DEP), and mitoxantrone + cabazitaxel + prednisone (MP) for CRPC treatment were identified. The network meta-analysis was conducted with software R 3.3.2. We analyzed the main outcomes, including the overall survival (OS), progression-free survival (PFS), prostate-specific antigen (PSA) response, tumor response and severe adverse events (AEs). Ranking of the chemotherapeutic agents was based on probabilities of interventions for each of the outcomes that were performed. The consistency of direct and indirect evidence was assessed by node splitting. RESULTS: 10 RCTs, with 3590 patients, were analyzed. The network meta-analysis results revealed that CP significantly increased OS, PFS, PSA response, tumor response, and severe AEs compared to MP. DP showed similar results with CP except for tumor response, where it showed slight inferiority in effectiveness. DEP was associated with clearly improved outcomes in PFS, PSA response and tumor response compared to those of MP, but this was not the case for OS benefit and severe AEs. No significant difference was detected in DP, CP and DEP except for the outcomes of severe AEs. MP was less effective in survival and clinical benefit, but much safer in safety outcomes than other chemotherapy agents. The probabilities of rank plots showed that CP ranked first in OS and tumor response; DEP ranked first in PFS time and PSA response; MP was the best treatment mode for safety. CONCLUSIONS: DP and CP survival benefit (OS, PFS) and clinical benefit (PSA response and tumor response) were comparable, as well as their associated AEs. DEP was associated with less survival benefit, similar clinical improvement and more AEs than DP or CP. MP had the lowest survival and clinical benefit but excellent safety than other agents. Based on evidences of current results, we recommended CP as the most suitable chemotherapy agent for CRPC patients, followed by DP, MP as third, and DEP as the last choice. However, considering limitations of our network meta-analysis, additional high-quality studies are needed for further evaluation.