Rechallenge of docetaxel combined with epirubicin given on a weekly schedule in advanced castration-resistant prostate cancer patients previously exposed to docetaxel and abiraterone acetate: a single-institution experience

Functional implications and therapeutic targeting of androgen response elements in prostate cancer

The androgen receptor (AR) plays an essential role in the growth and progression of prostate cancer (CaP). Ligand-activated AR inside the nucleus binds to the androgen response element (ARE) of the target genes in dimeric form and recruits transcriptional machinery to facilitate gene transcription. Pharmacological compounds that inhibit the AR action either bind to the ligand binding domain (LBD) or interfere with the interactions of AR with other co-regulatory proteins, slowing the progression of the disease. However, the emergence of resistance to conventional treatment makes clinical management of CaP difficult. Resistance has been associated with activation of androgen/AR axis that restores AR transcriptional activity. Activated AR signaling in resistance cases can be mediated by several mechanisms including AR amplification, gain-of-function AR mutations, androgen receptor variant (ARVs), intracrine androgen production, and overexpression of AR coactivators. Importantly, in castration resistant prostate cancer, ARVs lacking the LBD become constitutively active and promote hormone-independent development, underlining the need to concentrate on the other domain or the AR-DNA interface for the identification of novel actionable targets. In this review, we highlight the plasticity of AR-DNA binding and explain how fine-tuning AR's cooperative interactions with DNA translate into developing an alternative strategy to antagonize AR activity.

Multiple Docetaxel Retreatments Without Prednisone for Metastatic Castration-Resistant Prostate Cancer in the Docetaxel-Only Era: Effects on PSA Kinetics and Survival

Introduction

This study aimed to assess the effects of multiple docetaxel (DOC) treatments on prostate-specific antigen (PSA) kinetics and survival among patients with metastatic castration-resistant prostate cancer (mCRPC) who were sensitive to first-line DOC and received no other life-prolonging agents. To eliminate the effect of cortisone on serum PSA, only patients who were treated without prednisone were included.

Methods

This IRB-approved retrospective study evaluated 52 patients with mCRPC who were retreated using DOC after first-line DOC (without prednisone in both cases), based on a PSA response of > 50% and no radiographic progression. Twenty-three PSA-based factors, including static and kinetic PSA measures, were evaluate for their ability to predict overall survival (OS)

Results

The patients received 688 cycles of DOC in 143 series, including 91 courses of retreatments (1 cycle: 28 patients, 2 cycles: 14 patients, 3 cycles: 8 patients, 4 cycles: 1 patient, and 7 cycles: 1 patient). The median overall number of cycles per patient was 12 (range: 7–31). The median durations of the first, second, and third holidays were 18 weeks (6–60 weeks), 16 weeks (3–44 weeks), and 17 weeks (8–51 weeks), respectively. The median OSs were 22 months (10.5–70 months) after the first DOC treatment and 14 months (3–65 months) after the second DOC treatment. The > 50% PSA decline rate was 48% after retreatment. Short treatment holidays (< 3 months) were associated with shortened OS (p = 0.01). In the multivariate analysis, a 25% PSA increase over the nadir was the strongest predictor of survival (HR: 3.20, 95% CI: 1.47–6.99, p = 0.003).

Conclusions

DOC retreatment without prednisone had anti-tumor activity in a considerable proportion of mCRPC cases that were initially sensitive to first-line DOC. A 25% PSA increase over the nadir might predict acquired DOC resistance.

Role of noncoding RNA in drug resistance of prostate cancer

Prostate cancer is one of the most prevalent forms of cancer around the world. Androgen-deprivation treatment and chemotherapy are the curative approaches used to suppress prostate cancer progression. However, drug resistance is extensively and hard to overcome even though remarkable progress has been made in recent decades. Noncoding RNAs, such as miRNAs, lncRNAs, and circRNAs, are a group of cellular RNAs which participate in various cellular processes and diseases. Recently, accumulating evidence has highlighted the vital role of non-coding RNA in the development of drug resistance in prostate cancer. In this review, we summarize the important roles of these three classes of noncoding RNA in drug resistance and the potential therapeutic applications in this disease.

Orphan nuclear receptor RORγ confers doxorubicin resistance in prostate cancer

Prostate cancer (PCa) is a malignant tumor with an extremely high prevalence. Doxorubicin is the first-line clinical treatment for castration-resistant PCa. Clinically, relapse is almost inevitable due to the cancer cells' increasing resistance to doxorubicin. Our previous studies have revealed that retinoic acid-related orphan nuclear receptor γ (RORγ) is a key protein for cancer progression and a promising target for PCa therapy. Though, RORγ's role and mechanism in doxorubicin-resistant PCa remain unclear. To study the mechanism of doxorubicin resistance, we generated a doxorubicin-resistant PCa cell line C4-2B (C4-2B DoxR) in this study, by culturing cells in an increasing doxorubicin concentration. Here, we show that RORγ expression was upregulated in C4-2B DoxR cells compared with that in normal C4-2B cells. The RORγ-stably-overexpressing PCa cell line constructed by lentiviral transfection showed an obvious improvement in doxorubicin resistance and a trend toward castration resistance. Furthermore, RORγ-specific small molecule inhibitors XY018, GSK805, and SR2211 can significantly inhibit the proliferation of C4-2B DoxR cells and promote their apoptosis. Collectively, these results have demonstrated the correlation between the upregulation of RORγ and the development of PCa's doxorubicin resistance, thus providing new ideas for solving the problem of chemotherapy drug resistance in PCa.

Docetaxel Rechallenge in Patients with Metastatic Prostate Cancer: A Comprehensive Review

BACKGROUND

Recent years have witnessed a huge shift in the management and prognosis of metastatic prostate cancer with the advent of new-generation anti-hormonal treatments. Docetaxel, which was initially approved in the castrate-resistant prostate cancer setting, has been approved in the earlier course of the disease as it is still castrate sensitive.

SUMMARY

Apart from cabazitaxel and in the absence of other effective chemotherapies, docetaxel rechallenge (DR) in patients with proved sensitivity to docetaxel in the earlier stage of the disease remains a possible option. Unfortunately, the pivotal trials rarely reported on the outcomes of docetaxel retreatment which seems a plausible option in patients initially responding to docetaxel and maintaining a minimum progression-free interval of 3-6 months. In this review, a summary of the clinical evidence and potential concerns for the use of DR in patients with metastatic prostate cancer will be presented. Key Messages: Pivotal trials of docetaxel in metastatic castrate-sensitive prostate cancer as well as metastatic castrate-resistant prostate cancer have not reported on the outcomes of DR except in the GETUG-AFU 15 trial where the outcomes were disappointing. Based on the published retrospective data, DR may be effective in patients who initially responded to docetaxel and maintained a progression-free interval exceeding 6 months.

Is there still a place for vinorelbine in advanced metastatic castration resistant prostate cancer?

The aim of this paper was to evaluate the activity and tolerability of oral vinorelbine in patients with advanced castration resistant prostate cancer (CRPC) who progressed after a minimum of three lines including: abiraterone acetate, docetaxel, cabazitaxel, and enzalutamide.Treatment consisted of weekly oral vinorelbine 60 mg/m. Chemotherapy was administered until disease progression or unacceptable toxicity.Twenty-six patients received vinorelbine: their median age was 74 years (range 58-84 years). Twenty-four (92.3%) patients had bone metastases. A decrease in PSA levels ≥50% was observed in 2 patients (7.7%). Among the subjects who were symptomatic at baseline, pain was reduced in 3 patients (13.6%) with a significant decrease in analgesic use. Median progression-free survival was 9 weeks (95% CI: 7 to 11) and median overall survival was 17 weeks (95% CI: 12 to 22). Treatment was well tolerated, and no grade 4 toxicities were observed.Our findings do not suggest the use of oral vinorelbine on a weekly schedule, in CRPC heavily pre-treated.

Corticosteroid switch in heavily pre-treated castration-resistant prostate cancer patients progressed on abiraterone acetate plus prednisone

The aim of this retrospective study is to evaluate the activity and safety of a steroidal switch from prednisone to dexamethasone in patients with advanced, heavily pre-treated, castration-resistant prostate cancer (CRPC) who progressed on abiraterone acetate. Treatment consisted of oral daily abiraterone plus dexamethasone (0.5 mg once daily) administered until disease progression or unacceptable toxicity. Thirty-six patients were evaluated: all men underwent a prior treatment with enzalutamide. A PSA decrease ≥50% was observed in 11% of patients; median progression-free survival was 10.8 weeks (95% CI: 9.2-16), and median survival was 17.6 weeks (95% CI: 15.8-28.8). Better efficacy and survival were observed in the subgroup of patients treated with abiraterone acetate prior for a period >3 months; treatment was well tolerated, and no grade 3-4 toxicities were observed. Our findings did not suggest the use of steroid switch in all CRPC who were heavily pre-treated. However, the switch could be an option for patients who responded well to prior abiraterone acetate treatment.

RNA interference-mediated depletion of TRPM8 enhances the efficacy of epirubicin chemotherapy in prostate cancer LNCaP and PC3 cells

Several studies have shown that transient receptor potential cation channel subfamily M member 8 (TRPM8), which has been regarded as a novel prostate-specific marker, serves a key role in processes such as the proliferation, viability and cell migration of prostate cancer cells. Efforts have been made to uncover the potential role of targeting TRPM8 in the management of prostate cancer; it has been verified that TRPM8-targeted blockade, either by RNA interference-mediated depletion or specific TRPM8 inhibitors, could reduce the rate of proliferation and proliferative fraction, and induce apoptosis in prostate cancer cells. The aim of the present study was to investigate the effect of knockdown of TRPM8 on chemosensitivity in prostate cancer LNCaP and PC3 cells. The RNA interference-mediated depletion of TRPM8 inhibited proliferation and enhanced epirubicin chemosensitivity of LNCaP and PC3 cells, and promoted epirubicin-induced apoptosis by increasing the phosphorylation of p38 mitogen-activated protein kinase (hereafter p38) and c-Jun N-terminal kinase (JNK)/mitogen-activated protein kinase signaling pathways, which was demonstrated via the use of specific inhibitors of phosphorylation of p38 and JNK. The results demonstrate that the targeted silencing of TRPM8 expression is a therapeutic strategy for treatment of prostate cancer that has considerable potential, even for castration-resistant prostate cancer.

Costunolide enhances doxorubicin-induced apoptosis in prostate cancer cells via activated mitogen-activated protein kinases and generation of reactive oxygen species

The management of castration-resistant prostate cancer (CRPC) is challenging, attributable to a lack of efficacious therapies. Chemotherapy is one of the most important treatments for CRPC. Doxorubicin has been extensively used in many different tumors and is often combined with other drugs to enhance effects and reduce toxicity. Costunolide is a natural sesquiterpene lactone with anti-cancer properties. In this study, we first demonstrated that the combination of costunolide and doxorubicin induced apoptosis significantly more than either drug alone in prostate cancer cell lines. Costunolide combined with doxorubicin induced mitochondria-mediated apoptosis through a loss of mitochondrial membrane potential and modulation of Bcl-2 family proteins. We found that this drug combination significantly increased the production of reactive oxygen species (ROS), as well as phosphorylation of c-jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinases, which play upstream roles in mitochondria-mediated apoptosis. Further studies showed that N-acetyl cysteine blocked JNK and p38 phosphorylation, suggesting that ROS were upstream activators of JNK and p38. However, a JNK inhibitor, but not a p38 inhibitor, blocked the increase in ROS observed in cells treated with a combination of costunolide and doxorubicin, suggesting that ROS and JNK could activate each other. In vivo, inhibition of tumor growth and induction of apoptosis were greater in mice treated with the costunolide and doxorubicin combination than in mice treated with either drug alone, without an increase in toxicity. Therefore, we suggested that costunolide in combination with doxorubicin was a new potential chemotherapeutic strategy for treating prostate cancer.

Second-line therapy in patients with metastatic castration-resistant prostate cancer with progression after or under docetaxel: A systematic review of nine randomized controlled trials

Treatment decisions are challenging in patients with metastatic castration-resistant prostate cancer with progression after or under docetaxel. The current review systematically searched the published literature on all treatment options, and assessed the risk of bias and quality of evidence. It found the best available evidence for effective prolongation of overall survival and progression-free survival for abiraterone acetate plus prednisone versus placebo plus prednisone and enzalutamide versus placebo. Other treatment modalities could be beneficial for individual patients by taking into consideration the: selection criteria of the randomized clinical trials, risk of bias, subgroup analyses, and quality of life and adverse events. Further research is needed to determine the sequence, timing asnd combination of different treatments.