Expert opinion on first-line therapy in the treatment of castration-resistant prostate cancer

Identification and validation of an immune-related gene pairs signature for three urologic cancers

Reliable biomarkers are needed to recognize urologic cancer patients at high risk for recurrence. In this study, we built a novel immune-related gene pairs signature to simultaneously predict recurrence for three urologic cancers. We gathered 14 publicly available gene expression profiles including bladder, prostate and kidney cancer. A total of 2,700 samples were classified into the training set (n = 1,622) and validation set (n = 1,078). The 25 immune-related gene pairs signature consisting of 41 unique genes was developed by the least absolute shrinkage and selection operator regression analysis and Cox regression model. The signature stratified patients into high- and low-risk groups with significantly different relapse-free survival in the meta-training set and its subpopulations, and was an independent prognostic factor of urologic cancers. This signature showed a robust ability in the meta-validation and multiple independent validation cohorts. Immune and inflammatory response, chemotaxis and cytokine activity were enriched with genes relevant to the signature. A significantly higher infiltration level of M1 macrophages was found in the high-risk group versus the low-risk group. In conclusion, our signature is a promising prognostic biomarker for predicting relapse-free survival in patients with urologic cancer.

Transcription factor 4 expression in circulating tumor cells from castration-resistant prostate cancer

INTRODUCTION

Neuroendocrine differentiation is partly caused by antiandrogen therapy and exhibits an androgen receptor-independent growth mechanism. We hypothesized that the expression of transcription factor 4, an inducer of neuroendocrine differentiation, in circulating tumor cells is related to drug resistance in castration-resistant prostate cancer.

CASE PRESENTATION

We evaluate the messenger ribonucleic acid expression of transcription factor 4 in circulating tumor cells from 17 patients with castration-resistant prostate cancer and compared these levels between patients receiving antiandrogen therapies and those who were resistant to antiandrogen therapies and receiving chemotherapies. The expression of transcription factor 4 in circulating tumor cells was significantly higher among patients receiving chemotherapies.

CONCLUSION

This study shows that transcription factor 4 is higher in the group of patients who were judged by their physicians to need chemotherapy treatment.

[Changes in the treatment of metastatic prostate cancer-new data and open questions]

The availability of taxane-based chemotherapy and androgen-receptor-targeted agents (ARTAs) have significantly broadened the therapeutic options for patients with metastatic prostate cancer and may also result in longer patient survival. The therapeutic sequence of ARTAs and taxanes may influence outcome and therefore decisions should be made on an individual basis. This article provides guidance for therapeutic decision-making in daily clinical practice by working out criteria that can be used to support individual therapeutic decisions. The focus is on metastatic castration-naive prostate cancer, oligometastatic disease as well as non-metastatic and metastatic castration-resistant prostate cancer.

TCF4 induces enzalutamide resistance via neuroendocrine differentiation in prostate cancer

In treating patients with castration resistant prostate cancer (CRPC), enzalutamide, the second-generation androgen receptor (AR) antagonist, is an accepted standard of care. However, clinical benefits are limited to a median time of 4.8 months because resistance inevitably emerges. To determine the mechanism of treatment resistance, we carried out a RNA sequence analysis and found increased expression levels of neuroendocrine markers in the enzalutamide-resistant LNCaP human prostate cancer (CaP) cell line when compared to the parental cell line. Subsequent studies demonstrated that Transcription Factor-4 (TCF4), a transcription factor implicated in WNT signaling, mediated neuroendocrine differentiation (NED) in response to enzalutamide treatment and was elevated in the enzalutamide-resistant LNCaP. In addition, we observed that PTHrP mediated enzalutamide resistance in tissue culture and inducible TCF4 overexpression resulted in enzalutamide-resistance in a mouse xenograft model. Finally, small molecule inhibitors of TCF4 or PTHrP partially reversed enzalutamide resistance in CaP cells. When tissues obtained from men who died of metastatic CaP were examined, a positive correlation was found between the expression levels of TCF4 and PTHrP. Taken together, the current results indicate that TCF4 induces enzalutamide resistance via NED in CaP.

[Treatment situation in metastastic Castration Naive Prostate Cancer (mCRPC) and the implications on clinical routine]

There is an ongoing change of paradigm in the treatment of metastatic prostate cancer (mPC). Taxan-based chemotherapy demonstrated a prolonged survival of patients in several randomized phase III trials. This is true in the situation of metastatic castration-resistent prostate cancer (mCRPC) as well as in the hormone-naïve stage (metastatic castration-naive PC [mCNPC]). In patients with mCNPC, treatment with docetaxel in combination with androgen deprivation therapy (ADT) prolonged the median total survival time by 15 months in comparison to ADT alone. Comparable results were obtained by the endocrine combination treatment with ADT/abiraterone. With the current data in mind it seems to be useful to discuss the value of early combination therapy with ADT/docetaxel or ADT/abiraterone as well as the impact on further treatment options in the mCRPC setting and to define criteria for treatment decisions in clinical practice.

Prostate Tumor Overexpressed-1 (PTOV1) promotes docetaxel-resistance and survival of castration resistant prostate cancer cells

Metastatic prostate cancer is presently incurable. The oncogenic protein PTOV1, first described in prostate cancer, was reported as overexpressed and significantly correlated with poor survival in numerous tumors. Here, we investigated the role of PTOV1 in prostate cancer survival to docetaxel and self-renewal ability. Transduction of PTOV1 in docetaxel-sensitive Du145 and PC3 cells significantly increased cell survival after docetaxel exposure and induced docetaxel-resistance genes expression (ABCB1, CCNG2 and TUBB2B). In addition, PTOV1 induced prostatospheres formation and self-renewal genes expression (ALDH1A1, LIN28A, MYC and NANOG). In contrast, Du145 and PC3 cells knockdown for PTOV1 significantly accumulated in the G2/M phase, presented a concomitant increased subG1 peak, and cell death by apoptosis. These effects were enhanced in docetaxel-resistant cells. Analyses of tumor datasets show that PTOV1 expression significantly correlated with prostate tumor grade, drug resistance (CCNG2) and self-renewal (ALDH1A1, MYC) markers. These genes are concurrently overexpressed in most metastatic lesions. Metastases also show PTOV1 genomic amplification in significant co-occurrence with docetaxel-resistance and self-renewal genes. Our findings identify PTOV1 as a promoter of docetaxel-resistance and self-renewal characteristics for castration resistant prostate cancer. The concomitant increased expression of PTOV1, ALDH1A1 and CCNG2 in primary tumors, may predict metastasis and bad prognosis.

First-line management of metastatic castrate-resistant prostate cancer patients: Audit of real-life practices

BACKGROUND

No reliable guidelines are available for choosing the best option between docetaxel and new hormonal therapies (NHTs) (i.e., abiraterone and enzalutamide) in first-line therapy for metastatic castration-resistant prostate cancer (mCRPC) patients. We performed an audit of real-life practices.

METHODS

We built an online questionnaire and distributed it with the help of French oncology networks. This questionnaire was sent to 481 physicians who treat patients with mCRPC. All of the answers were declarative, individual, and anonymized. A descriptive analysis was done. A univariate logistic regression analysis was performed for the criteria of choice between docetaxel and NHTs.

RESULTS

From March to July 2015, 109/481 physicians (22.6%) completed the questionnaire. The selection criteria for initially choosing docetaxel were as follows: presence of visceral metastases (79.8%), heavy tumor burden (68.8%), aggressive tumor disease (66.1%), and short-term efficacy of castration (66.1%). The selection criteria for initially choosing NHTs were as follows: long-term efficacy of castration (66.1%), higher age (67.9%), low tumor grade (56.9%), and absence of symptoms (54.1%). With docetaxel, the first tumor assessment was typically performed after three (1-6) cycles, including prostate-specific antigen (PSA) testing (96.3%), a thoraco-abdominopelvic CT scan (68.8%), and bone scintigraphy (59.6%). With NHTs, tumor assessment was mainly performed after 3 months of treatment (1-6) and included PSA testing, a thoraco-abdominopelvic CT, and bone scintigraphy in 90.8%, 61.5%, and 63.3% of cases, respectively.

CONCLUSIONS

This is the first study assessing real-life practices among physicians who treat patients with mCRPC. These practices were found to be homogeneous.

Multi-drug loaded micelles delivering chemotherapy and targeted therapies directed against HSP90 and the PI3K/AKT/mTOR pathway in prostate cancer

BACKGROUND

Advanced prostate cancers that are resistant to all current therapies create a need for new therapeutic strategies. One recent innovative approach to cancer therapy is the simultaneous use of multiple FDA-approved drugs to target multiple pathways. A challenge for this approach is caused by the different solubility requirements of each individual drug, resulting in the need for a drug vehicle that is non-toxic and capable of carrying multiple water-insoluble antitumor drugs. Micelles have recently been shown to be new candidate drug solubilizers for anti cancer therapy.

METHODS

This study set out to examine the potential use of multi-drug loaded micelles for prostate cancer treatment in preclinical models including cell line and mouse models for prostate cancers with Pten deletions. Specifically antimitotic agent docetaxel, mTOR inhibitor rapamycin, and HSP90 inhibitor 17-N-allylamino-17-demethoxygeldanamycin were incorporated into the micelle system (DR17) and tested for antitumor efficacy.

RESULTS

In vitro growth inhibition of prostate cancer cells was greater when all three drugs were used in combination compared to each individual drug, and packaging the drugs into micelles enhanced the cytotoxic effects. At the molecular level DR17 targeted simultaneously several molecular signaling axes important in prostate cancer including androgen receptor, mTOR, and PI3K/AKT. In a mouse genetic model of prostate cancer, DR17 treatment decreased prostate weight, which was achieved by both increasing caspase-dependent cell death and decreasing cell proliferation. Similar effects were also observed when DR17 was administered to nude mice bearing prostate cancer cells xenografts.

CONCLUSION

These results suggest that combining these three cancer drugs in multi-drug loaded micelles may be a promising strategy for prostate cancer therapy.

Biodegradable brush-type copolymer modified with targeting peptide as a nanoscopic platform for targeting drug delivery to treat castration-resistant prostate cancer

Well-defined amphiphilic tumor-targeting brush-type copolymers, poly(oligo(ethylene glycol) monomethyl ether methacrylate-co-G3-C12)-g-poly(ε-caprolactone) (P(OEGMA-co-G3-C12)-g- PCL), were synthesized by the combination of ring-opening polymerization (ROP), reversible addition-fragmentation transfer (RAFT) polymerization and polymer post-functionalization, in which G3-C12 was castration-resistant prostate cancer (CRPC) targeting peptide. The obtained polymers were then employed for the targeted treatment of CRPC by delivering a hydrophobic anticancer drug (bufalin, BUF). Polymerizable monomer, 3-((2-(methacryloyloxy)ethyl)thio)propanoic acid (BSMA) and PCL-based macromolecular monomer (PCLMA) were synthesized at first. RAFT polymerization of OEGMA, BSMA, and PCLMA afforded amphiphilic brush-type copolymers, P(OEGMA-co-BSMA)-g-PCL. Post-functionalization of the obtained polymers with G3-C12 led to the formation of the final amphiphilic targeting brush-type copolymers, P(OEGMA-co-G3-C12)-g- PCL. In aqueous media, P(OEGMA-co-G3-C12)-g-PCL self-assembles into micelles with a hydrodynamic diameter (Dh) of ∼66.1±0.44nm. It was demonstrated that the obtained micellar nanoparticles exhibited good biocompatibility and biodegradability. Besides, BUF-loaded micellar nanoparticles assembled from P(OEGMA-co-G3-C12)-g-PCL, BUF-NP-(G3-C12), showed a controlled drug release in vitro and improved anticancer efficacy both in vitro and in vivo.

Nanoparticle formulation of small DNA molecules, Dbait, improves the sensitivity of hormone-independent prostate cancer to radiotherapy

Intensification of radiotherapy has been shown to improve prostate cancer (PCa) outcomes. We hypothesized that we could further improve radiotherapy efficacy through the use DNA repair inhibitors. In this study, we evaluated the use of a new class of DNA damage repair inhibitor, nanoparticle (NP) Dbait, in radiosensitization of PCa. NP Dbait was formulated using H1 nanopolymer (folate-polyethylenimine600-cyclodextrin). We demonstrated that NP Dbait was a potent radiosensitizer in vitro by colony forming assay using PCa cell lines. The result was validated in vivo using mouse xenograft models of PCa and we showed that NP Dbait significantly suppressed tumor growth and prolonged survival. Western blot, immunofluorescence and immunohistochemistry showed that NP Dbait inhibited DNA damage repair signaling pathways by mimicking DNA double-strand breaks. Our study supports further investigations of NP Dbait in improving the therapeutic efficacy of cancer radiotherapy.