Docetaxel followed by castration improves outcomes in LNCaP prostate cancer-bearing severe combined immunodeficient mice

Network meta-analysis of combination strategies in metastatic hormone-sensitive prostate cancer

This study compared different doublet and triplet therapies for efficacy and safety in metastatic hormone-sensitive prostate cancer (mHSPC). PubMed, EMBASE, and the Cochrane Library were comprehensively searched for eligible randomized controlled trials (RCTs) published from inception to October 2023. Interventions included abiraterone, apalutamide, enzalutamide, docetaxel, darolutamide, and androgen deprivation therapy (ADT), either as doublet or triplet therapies. The outcomes examined were overall survival (OS), progression-free survival (PFS), castration-resistant prostate cancer (CRPC)-free survival, time to symptomatic skeletal event (SSE), and toxicity. The surface under the cumulative ranking curve (SUCRA) was determined to identify the preferred treatments. Ten RCTs were included. The combination of darolutamide, docetaxel, and ADT had the highest SUCRA of 84.3 for OS, followed by combined abiraterone, docetaxel, and ADT (SUCRA = 71.6). The highest SUCRAs for PFS were observed for triplet therapies (abiraterone, docetaxel, and ADT [SUCRA = 74.9], followed by enzalutamide, docetaxel, and ADT [SUCRA = 74.3]) and other androgen receptor axis-targeted therapy-based doublet therapies (SUCRAs: 26.5-59.3). Darolutamide, docetaxel, and ADT had the highest SUCRAs, i.e ., 80.8 and 84.0 regarding CRPC-free survival and time to SSE, respectively. Regarding Grade >3 adverse events (AEs), the SUCRAs of triplet therapies (SUCRAs: 14.8-31.5) were similar to that of docetaxel and ADT (SUCRA = 39.5). Three studies had a low risk of bias in all categories; the remaining studies had at least an unclear risk of bias in at least one category. Triplet therapy demonstrated potentially enhanced effectiveness than doublet therapy in mHSPC, with acceptable safety concerns. Darolutamide might be the optimal option for triplet therapy in combination with docetaxel and ADT.

The cell-line-derived subcutaneous tumor model in preclinical cancer research

Tumor-bearing experimental animals are essential for preclinical cancer drug development. A broad range of tumor models is available, with the simplest and most widely used involving a tumor of mouse or human origin growing beneath the skin of a mouse: the subcutaneous tumor model. Here, we outline the different types of in vivo tumor model, including some of their advantages and disadvantages and how they fit into the drug-development process. We then describe in more detail the subcutaneous tumor model and key steps needed to establish it in the laboratory, namely: choosing the mouse strain and tumor cells; cell culture, preparation and injection of tumor cells; determining tumor volume; mouse welfare; and an appropriate experimental end point. The protocol leads to subcutaneous tumor growth usually within 1-3 weeks of cell injection and is suitable for those with experience in tissue culture and mouse experimentation.

Addition of Docetaxel to Androgen Receptor Axis-targeted Therapy and Androgen Deprivation Therapy in Metastatic Hormone-sensitive Prostate Cancer: A Network Meta-analysis

CONTEXT

Randomized controlled trials (RCTs) have shown that addition of docetaxel or androgen receptor axis-targeted therapy (ARAT) to androgen deprivation therapy (ADT) or addition of ARAT to ADT and docetaxel improves overall survival (OS) in metastatic hormone-sensitive prostate cancer (mHSPC). However, it is unknown whether docetaxel, when given as part of triplet therapy, has an independent OS benefit.

OBJECTIVE

To compare the efficacy of ADT plus ARAT with the triplet of ADT, ARAT, and docetaxel through a network meta-analysis (NMA) of RCTs in mHSPC.

EVIDENCE ACQUISITION

Bibliographic databases and conference proceedings were searched in March 2022 for RCTs that evaluated the addition of docetaxel, ARAT, or both to ADT in mHSPC. The primary endpoint was OS. Standard random-effect NMA and Bayesian analyses were performed to compare ADT plus ARAT with triplet therapy.

EVIDENCE SYNTHESIS

Eleven RCTs (n = 11 546) were eligible. Compared with ADT plus ARAT, the triplet had a nonsignificant OS benefit (hazard ratio [HR] 0.89, 95% confidence interval [CI] 0.68-1.16), while ADT plus docetaxel (HR 1.16 [0.94-1.43]) and ADT alone (HR 1.46 [1.30-1.64]) had an increased risk of death. By P-score ordering, the triplet was the most effective treatment strategy (P score = 0.936) followed by ADT plus ARAT (P score = 0.704). The triplet had a 77% likelihood of being the best treatment strategy compared with a 23% likelihood for ADT plus ARAT.

CONCLUSIONS

The triplet of ADT, ARAT, and docetaxel was the highest ranked treatment strategy, but it did not confer a statistically significant OS benefit over ADT plus ARAT. This NMA provides the highest-level comparative evidence for these treatment approaches in the initial management of mHSPC.

PATIENT SUMMARY

We synthesized the available evidence from clinical trials conducted in newly diagnosed metastatic prostate cancer to compare the survival of patients receiving triplet therapy (androgen receptor axis-targeted therapy [ARAT], androgen deprivation therapy [ADT], and docetaxel) with those receiving only ARAT and ADT. We conclude that the triplet is a somewhat more effective treatment approach.

Targeting the androgen receptor (AR) with AR degradation enhancer ASC-J9® led to increase docetaxel sensitivity via suppressing the p21 expression

Chemotherapy with docetaxel remains the effective therapy to suppress castration resistant prostate cancer (CRPC) in some patients. However, most chemotherapy with docetaxel eventually fails with the development of docetaxel resistance after 18-weeks of treatment. Here we found docetaxel treatment might have an adverse effect of increasing the androgen receptor (AR) protein level in the CRPC cells, and combining docetaxel with anti-AR therapy using AR-shRNA or the AR degradation enhancer ASC-J9® may increase docetaxel sensitivity to better suppress the CRPC cell growth. Mechanism dissection found docetaxel might have the adverse effect of increasing the AR protein stability via suppressing the AR ubiquitination due to the increased AR phosphorylation. The consequence of such increased AR protein may then lead to increase p21 expression via transcriptional regulation. Preclinical studies with in vitro cells lines also demonstrated that targeting AR with ASC-J9® led to suppressing the AR-increased p21 expression to improve the docetaxel sensitivity in the CRPC cells that already developed docetaxel resistance. Together, these results suggest that a combined therapy of docetaxel and ASC-J9® is a novel therapy to better suppress CRPC in patients that already developed docetaxel resistance.

[11C]Choline PET/CT in therapy response assessment of a neoadjuvant therapy in locally advanced and high risk prostate cancer before radical prostatectomy

PURPOSE

Recent studies have shown promising results of neoadjuvant therapy in prostate cancer (PC). The aim of this study was to evaluate the potential of [11C]Choline PET/CT in therapy response monitoring after combined neoadjuvant docetaxel chemotherapy and complete androgen blockade in locally advanced and high risk PC patients.

RESULTS

In [11C]Choline PET/CT there was a significant decrease of SUVmax and SUVmean (p = 0.004, each), prostate volume (p = 0.005) and PSA value (p = 0.003) after combined neoadjuvant therapy. MRI showed a significant prostate and tumor volume reduction (p = 0.003 and 0.005, respectively). Number of apoptotic cells was significantly higher in prostatectomy specimens of the therapy group compared to pretherapeutic biopsies and the control group (p = 0.02 and 0.003, respectively).

METHODS

11 patients received two [11C]Choline PET/CT and MRI scans before and after combined neoadjuvant therapy followed by radical prostatectomy and pelvic lymph node dissection. [11C]Choline uptake, prostate and tumor volume, PSA value (before/after neoadjuvant therapy) and apoptosis (of pretherapeutic biopsy/posttherapeutic prostatectomy specimens of the therapy group and prostatectomy specimens of a matched control group without neoadjuvant therapy) were assessed and tested for differences and correlation using SPSS.

CONCLUSIONS

The results showing a decrease in choline uptake after combined neoadjuvant therapy (paralleled by regressive and apoptotic changes in histopathology) confirm the potential of [11C]Choline PET/CT to monitor effects of neoadjuvant therapy in locally advanced and high risk PC patients. Further studies are recommended to evaluate its use during the course of neoadjuvant therapy for early response assessment.

Chemotherapy for metastatic castrate-sensitive prostate cancer

BACKGROUND

The role of docetaxel chemotherapy in combination with androgen deprivation therapy for metastatic castrate-sensitive prostate cancer is emerging.

METHODS

We reviewed the results from the pivotal randomized phase III trials in this area: GETUG15, CHAARTED and STAMPEDE.

RESULTS

All three studies demonstrated a benefit in progression-free survival with the use of docetaxel. However, two of the studies demonstrated a clinically meaningful overall survival benefit (CHAARTED and STAMPEDE), whereas the GETUG15 study did not demonstrate a major benefit.

CONCLUSIONS

Docetaxel is an important option to consider for men who are fit for chemotherapy with newly diagnosed metastatic prostate cancer commencing androgen deprivation therapy.

Why Chemotherapy Should be Given Early for Men with Metastatic Prostate Cancer

Metastatic hormone-sensitive prostate cancer (mHSPC) is an incurable disease, and despite a high response rate to androgen-deprivation therapy (ADT), outcomes have not significantly changed for many decades. Earlier attempts at multitargeted strategies with the addition of cytotoxic chemotherapy to ADT did not affect survival. As more effective therapies are emerging, including cytotoxic therapy for patients with metastatic castrate-resistant prostate cancer (mCRPC), there is increasing interest for testing these drugs earlier in the disease course. The premise is that agents with clinical benefit in advanced mCRPC may have a better effect if used preemptively before the development of significant resistance and to attack earlier de novo androgen resistant/independent clones. The recent results of the phase III clinical trial E3805 investigating ADT with or without docetaxel in mHSPC provide compelling support for this strategy. Docetaxel combined with ADT significantly improved overall survival from 44 to 57.6 months (p=0.0003), particularly in patients with high-volume disease (from 32.2 to 49.2 months; p=0.0006). Longer follow-up is needed to assess the effect on patients with low disease burden. Further studies are needed to further maximize the antitumor effect in patients with mHSPC and to investigate the effects of advancing therapy to this disease setting on the efficacy of respective agents in the castration-resistant setting.

Functional cyclic AMP response element in the breast cancer resistance protein (BCRP/ABCG2) promoter modulates epidermal growth factor receptor pathway- or androgen withdrawal-mediated BCRP/ABCG2 transcription in human cancer cells

Phosphorylated cyclic-AMP (cAMP) response element binding protein (p-CREB) is a downstream effector of a variety of important signaling pathways. We investigated whether the human BCRP promoter contains a functional cAMP response element (CRE). 8Br-cAMP, a cAMP analogue, increased the activity of a BCRP promoter reporter construct and BCRP mRNA in human carcinoma cells. Epidermal growth factor receptor (EGFR) pathway activation also led to an increase in p-CREB and in BCRP promoter reporter activity via two major downstream EGFR signaling pathways: the phosphotidylinositol-3-kinase (PI3K)/AKT pathway and the mitogen-activated protein kinase (MAPK) pathway. EGF treatment increased the phosphorylation of EGFR, AKT, ERK and CREB, while simultaneously enhancing BCRP mRNA and functional protein expression. EGF-stimulated CREB phosphorylation and BCRP induction were diminished by inhibition of EGFR, PI3K/AKT or RAS/MAPK signaling. CREB silencing using RNA interference reduced basal levels of BCRP mRNA and diminished the induction of BCRP by EGF. Chromatin immunoprecipitation assays confirmed that a putative CRE site on the BCRP promoter bound p-CREB by a point mutation of the CRE site abolished EGF-induced stimulation of BCRP promoter reporter activity. Furthermore, the CREB co-activator, cAMP-regulated transcriptional co-activator (CRTC2), is involved in CREB-mediated BCRP transcription: androgen depletion of LNCaP human prostate cancer cells increased both CREB phosphorylation and CRTC2 nuclear translocation, and enhanced BCRP expression. Silencing CREB or CRTC2 reduced basal BCRP expression and BCRP induction under androgen-depletion conditions. This novel CRE site plays a central role in mediating BCRP gene expression in several human cancer cell lines following activation of multiple cancer-relevant signaling pathways.

[[¹¹C]choline as a pharmacodynamic marker for docetaxel therapy. Response assessment in a LNCaP prostate cancer xenograft mouse model]

The AIM of this study was to determine whether [¹¹C]choline can be used for docetaxel therapy response assessment in a LNCaP-prostate cancer xenograft mouse model using [¹¹C]choline small-animal PET/CT.

ANIMALS, METHODS

The androgen-dependent human prostate cancer cell line LNCaP was implanted subcutaneously into the left flanks of 17 SCID-mice, 12.5 mg testosterone platelets were implanted in the neck wrinkle. All mice were injected 4-6 weeks after xenograft implantation with 37 MBq [¹¹C]choline via the tail vein. Dynamic imaging was performed for 60 minutes with a small-animal PET/CT scanner. After the first [¹¹C]choline PET/CT imaging 8 mice were subsequently injected intravenously with docetaxel twice (days 1 and 5) at a dose of 3 mg/kg body weight. 8 mice were treated with PBS as a control. [¹¹C]choline PET/CT imaging was performed on day 7, 14 and 21 after treatment. Image analysis was performed using tumor/muscle (T/M) ratios (ROI(T)/ROI(M) = T/M ratio).

RESULTS

All LNCaP tumours could be visualized by [¹¹C]choline PET/CT. Before treatment the mean T/M ratio was 2.0 ± 0.2 in the docetaxel-treated group and 1.9 ± 0.2 in the control group (p = 0.837). There was a reduction in the mean [¹¹C]choline uptake after docetaxel treatment of the tumours of the LNCaP cell line as early as 1 week after initiation of therapy (T/M(mean) ratio 1.5 ± 0.2 after one week, 1.3 ± 0.2 after 2 weeks and 1.4 ± 0.2 after 3 weeks). There was no decrease in [¹¹C]choline uptake in the control group.

CONCLUSION

Our results show that [¹¹C]choline has the potential for use in the early monitoring of the therapeutic effect of docetaxel in a LNCaP prostate cancer xenograft animal model.

Cytotoxic effects of the novel isoflavone, phenoxodiol, on prostate cancer cell lines

Phenoxodiol is an isoflavone derivative that has been shown to elicit cytotoxic effects against a broad range of human cancers. We examined the effect of phenoxodiol on cell death pathways on the prostate cell lines LNCaP, DU145 and PC3, representative of different stages of prostate cancer, and its effects on cell death pathways in these cell lines. Cell proliferation assays demonstrated a significant reduction in the rate of cell proliferation after 48 h exposure to phenoxodiol (10 and 30 μM). FACS analysis and 3'-end labelling indicated that all three prostate cancer cell lines underwent substantial levels of cell death 48 h after treatment. Mitochondrial membrane depolarization, indicative of early-stage cell death signalling, using JC-1 detection, was also apparent in all cell lines after exposure to phenoxodiol in the absence of caspase-3 activation. Caspase inhibition assays indicated that phenoxodiol operates through a caspase-independent cell death pathway. These data demonstrate that phenoxodiol elicits anti-cancer effects in prostate cancer cell lines representative of early and later stages of development through an as-yet-unknown cell death mechanism. These data warrant the further investigation of phenoxodiol as a potential treatment for prostate cancer.

Telomere and microtubule targeting in treatment-sensitive and treatment-resistant human prostate cancer cells

Modulating telomere dynamics may be a useful strategy for targeting prostate cancer cells, because they generally have short telomeres. Because a plateau has been reached in the development of taxane-based treatments for prostate cancer, this study was undertaken to evaluate the relative efficacy of targeting telomeres and microtubules in taxane-sensitive, taxane-resistant, androgen-sensitive, and androgen-insensitive prostate cancer cells. Paclitaxel- and docetaxel-resistant DU145 cells were developed and their underlying adaptive responses were evaluated. Telomere dynamics and the effects of targeting telomeres with sodium meta-arsenite (KML001) (an agent undergoing early clinical trials), including combinations with paclitaxel and docetaxel, were evaluated in parental and drug-resistant cells. The studies were extended to androgen-sensitive LNCaP cells and androgen-insensitive LNCaP/C81 cells. Both P-glycoprotein (Pgp)-dependent and non-Pgp-dependent mechanisms of resistance were recruited within the same population of DU145 cells with selection for drug resistance. Wild-type DU145 cells have a small side population (SP) (0.4-1.2%). The SP fraction increased with increasing drug resistance, which was correlated with enhanced expression of Pgp but not breast cancer resistance protein. Telomere dynamics remained unchanged in taxane-resistant cells, which retained sensitivity to KML001. Furthermore, KML001 targeted SP and non-SP fractions, inducing DNA damage signaling in both fractions. KML001 induced telomere erosion, decreased telomerase gene expression, and was highly synergistic with the taxanes in wild-type and drug-resistant DU145 cells. This synergism extended to androgen-sensitive and androgen-insensitive LNCaP cells under basal and androgen-deprived conditions. These studies demonstrate that KML001 plus docetaxel and KML001 plus paclitaxel represent highly synergistic drug combinations that should be explored further in the different disease states of prostate cancer.

Phase 2 study of neoadjuvant docetaxel plus bevacizumab in patients with high-risk localized prostate cancer: a Prostate Cancer Clinical Trials Consortium trial

BACKGROUND

Treatment of high-risk localized prostate cancer remains inadequate. The authors performed a phase 2 multicenter trial of neoadjuvant docetaxel plus bevacizumab before radical prostatectomy.

METHODS

Eligibility included any of the following: prostate-specific antigen (PSA) >20 ng/mL or PSA velocity >2 ng/mL/y, cT3 disease, any biopsy Gleason score 8 to 10, and Gleason score 7 with T3 disease by endorectal magnetic resonance imaging (MRI) at 1.5 T. Also, those with ≥50% biopsy cores involved and either Gleason score 7, PSA >10, or cT2 disease were eligible. Patients were treated with docetaxel 70 mg/m(2) every 3 weeks for 6 cycles and bevacizumab 15 mg/m(2) every 3 weeks for 5 cycles. The primary endpoint was partial response by endorectal MRI.

RESULTS

Forty-one patients were treated. Median age was 55 years (range, 40-66 years). Baseline characteristics included: median PSA, 10.1 ng/mL; cT2, 49%, cT3, 32%; and Gleason score 8 to 10, 73%. Thirty-eight of 41 (93%) patients completed all 6 cycles. Grade ≥3 adverse events were rare, although 3 of 41 (7%) experienced febrile neutropenia. Twelve patients (29%; 95% confidence interval [CI], 16%-45%) achieved a >50% reduction in tumor volume, and 9 patients (22%; 95% CI, 11%-38%) achieved a >50% post-treatment decline in PSA. Thirty-seven of the 41 patients underwent radical prostatectomy; there were no complete pathologic responses.

CONCLUSIONS

Neoadjuvant docetaxel and bevacizumab is safe, and results in reductions in both tumor volume and serum PSA, in men with high-risk localized prostate cancer. The role of neoadjuvant chemotherapy in prostate cancer, and perioperative antiangiogenic therapy in general, requires further elucidation through ongoing and planned trials.

Characterization of the small RNA transcriptomes of androgen dependent and independent prostate cancer cell line by deep sequencing

Given the important roles of miRNA in post-transcriptional regulation and its implications for cancer, characterization of miRNA facilitates us to uncover molecular mechanisms underlying the progression of androgen-independent prostate cancer (PCa). The emergence of next-generation sequencing technologies has dramatically changed the speed of all aspects of sequencing in a rapid and cost-effective fashion, which can permit an unbiased, quantitive and in-depth investigation of small RNA transcriptome. In this study, we used high-throughput Illumina sequencing to comprehensively represent the full complement of individual small RNA and to characterize miRNA expression profiles in both the androgen dependent and independent Pca cell line. At least 83 miRNAs are significantly differentially expressed, of which 41 are up-regulated and 42 are down-regulated, indicating these miRNAs may be involved in the transition of LNCaP to an androgen-independent phenotype. In addition, we have identified 43 novel miRNAs from the androgen dependent and independent PCa library and 3 of them are specific to the androgen-independent PCa. Function annotation of target genes indicated that most of these differentially expressed miRNAs tend to target genes involved in signal transduction and cell communication, epically the MAPK signaling pathway. The small RNA transcriptomes obtained in this study provide considerable insights into a better understanding of the expression and function of small RNAs in the development of androgen-independent prostate cancer.

Neoadjuvant therapy preceding prostatectomy for prostate cancer: rationale and current trials

Neoadjuvant therapy improves outcomes for a number of malignancies and provides intermediate pathologic outcomes, which correlate with long-term outcomes. Neoadjuvant androgen-deprivation therapy, alone or with docetaxel chemotherapy, preceding prostatectomy for localized prostate cancer is feasible and demonstrates pathologic activity, but evidence for improved long-term outcomes is lacking. Data in support of the further exploration of neoadjuvant therapy for localized prostate cancer preceding prostatectomy are reviewed. Ongoing randomized trials are elucidating the impact of neoadjuvant androgen deprivation combined with docetaxel chemotherapy on pathologic and long-term outcomes. The correlation of pathologic and biologic outcomes with long-term outcomes in this setting is unknown. The neoadjuvant therapy approach followed by prostatectomy is feasible with a wide array of agents and provides a paradigm for evaluating the activity, and mechanism of action and resistance to new treatments. This promising modality may aid the rapid development of novel therapeutic agents. A multidisciplinary approach involving oncologists, urologists and pathologists is critical to the success of this model.

Estradiol suppresses tissue androgens and prostate cancer growth in castration resistant prostate cancer

Background

Estrogens suppress tumor growth in prostate cancer which progresses despite anorchid serum androgen levels, termed castration resistant prostate cancers (CRPC), although the mechanisms are unclear. We hypothesize that estrogen inhibits CRPC in anorchid animals by suppressing tumoral androgens, an effect independent of the estrogen receptor.

Methods

The human CRPC xenograft LuCaP 35V was implanted into orchiectomized male SCID mice and established tumors were treated with placebo, 17β-estradiol or 17β-estradiol and estrogen receptor antagonist ICI 182,780. Effects of 17β-estradiol on tumor growth were evaluated and tissue testosterone (T) and dihydrotestosterone (DHT) evaluated by mass spectrometry.

Results

Treatment of LuCaP 35V with 17β-estradiol slowed tumor growth compared to controls (tumor volume at day 21: 785 ± 81 mm³ vs. 1195 ± 84 mm³, p = 0.002). Survival was also significantly improved in animals treated with 17β-estradiol (p = 0.03). The addition of the estrogen receptor antagonist ICI 182,780 did not significantly change survival or growth. 17β-estradiol in the presence and absence of ICI 182,780 suppressed tumor testosterone (T) and dihydrotestosterone (DHT) as assayed by mass spectrometry. Tissue androgens in placebo treated LuCaP 35V xenografts were; T = 0.71 ± 0.28 pg/mg and DHT = 1.73 ± 0.36 pg/mg. In 17β-estradiol treated LuCaP35V xenografts the tissue androgens were, T = 0.20 ± 0.10 pg/mg and DHT = 0.15 ± 0.15 pg/mg, (p < 0.001 vs. controls). Levels of T and DHT in control liver tissue were < 0.2 pg/mg.

Conclusions

CRPC in anorchid animals maintains tumoral androgen levels despite castration. 17β-estradiol significantly suppressed tumor T and DHT and inhibits growth of CRPC in an estrogen receptor independent manner. The ability to manipulate tumoral androgens will be critical in the development and testing of agents targeting CRPC through tissue steroidogenesis.

The relationship of neuroendocrine carcinomas to anti-tumor therapies in TRAMP mice

BACKGROUND

Neuroendocrine differentiation and neuroendocrine carcinoma (NEC) have been linked to androgen deprivation in prostate cancers. No previous study has directly connected neuroendocrine phenotypes to chemotherapy. The pathogenesis of prostatic NEC has not yet been determined.

METHODS

Using the transgenic adenocarcinoma of mouse prostate (TRAMP) model, we studied tumor progression after hormone ablation (castration) and/or chemotherapy (docetaxel), and analyzed the incidence of NEC as a function of the anti-tumor therapies. Non-treated mice were used as controls. Protein expressions in tumor tissues were analyzed by Western blots and immunohistochemistry.

RESULTS

Although all animals developed prostate cancer, no NEC was found in control mice. However, over 30% of the mice that received an anti-tumor therapy developed NEC. A similar incidence of NEC was found in the castration-only and docetaxel-only treatment groups, while a higher incidence was observed in the combined treatment (castration and docetaxel) group. The NEC-bearing mice had smaller tumors in their prostates and lived longer than mice with adenocarcinoma (ADC-only). However, NEC tumors had a higher proliferative index and greater potential for metastasis and drug-resistance, as evidenced by significantly higher expression levels of PCNA, S100A4, and Pgp, but lower levels of E-cadherin. SV40 T-antigen was highly expressed in both NEC and ADC tumors.

CONCLUSIONS

Stress induced by anti-cancer treatments may play a role in NEC development. Although NEC and ADC differ in their expressions of many proteins, a high level of SV40 T-antigen in both tumor types suggest a common progenitor..

Phase II trial of short-term neoadjuvant docetaxel and complete androgen blockade in high-risk prostate cancer

BACKGROUND

The low probability of curing high-risk prostate cancer (PC) with local therapy suggests the need to study modality of therapeutic approaches. To this end, a prospective phase II trial of neoadjuvant docetaxel (D) and complete androgen blockade (CAB) was carried out in high-risk PC patients. The primary end point was to detect at least 10% of pCRs after chemohormonal treatment.

METHODS

Patients with T1c-T2 clinical stage with prostate-specific antigen (PSA) >20 ng ml(-1) and/or Gleason score >or=7 (4+3) and T3 were included. Treatment consisted of three cycles of D 36 mg m(-2) on days 1, 8 and 15 every 28 days concomitant with CAB, followed by radical prostatectomy (RP).

RESULTS

A total of 57 patients were included. Clinical stage was T1c, 11 patients (19.3%); T2, 30 (52.6%) and T3, 16 (28%) patients. Gleason score was >or=7 (4+3) in 44 (77%) patients and PSA >20 ng ml(-1) in 15 (26%) patients. Treatment was well tolerated with 51 (89.9%) patients completing neoadjuvant therapy together with RP. The rate of pCR was 6% (three patients). Three (6%) additional patients had microscopic residual tumour (near pCR) in prostate specimen. With a median follow-up of 35 months, 18 (31.6%) patients presented PSA relapse.

CONCLUSION

Short-term neoadjuvant D and CAB induced a 6% pCR rate, which is close to what would be expected with ADT alone. The combination was generally well tolerated.

Divergent effects of castration on prostate cancer in TRAMP mice: possible implications for therapy

PURPOSE

Divergent responses to androgen deprivation have been found in patients and in animal models of prostate cancer. The molecular basis for these different outcomes is unknown. Our aim was to identify the molecular responses of prostate cancer with divergent outcomes to androgen deprivation in TRAMP mice.

EXPERIMENTAL DESIGN

Castrated and noncastrated B6xFVB TRAMP mice were evaluated for survival, tumor development, pathology, and expressions of specific proteins at different time points.

RESULTS

TRAMP mice responded differentially to androgen deprivation. In the majority, primary tumors regressed after castration (positive response), whereas in others the tumors grew even more aggressively than in the noncastrated mice (negative response). Mice with regressed tumors had the highest survival rates. Androgen receptor was elevated in all tumors from castrated mice despite significant differences in tumor sizes. In positively responding tumors, expressions of Bcl-2 and Grp78 were greatly increased by 10 weeks after castration, whereas expressions of Bax, Bcl-xl, SV40 T antigen, and c-myc were lower. These tumors also showed a reduction in proliferating cells compared with noncastrates and negatively responding tumors. Most of these changes disappeared 20 weeks after castration, by which time there was an increase in the size of primary tumors as well as in distant metastasis.

CONCLUSIONS

In TRAMP prostate cancer that responded positively to castration, different expression patterns of proteins involved in cellular apoptosis, stress, and proliferation occur approximately 10 weeks after castration. This may be an optimal time for targeting Bcl-2, and perhaps Grp78, to enhance the antitumor effects of androgen deprivation.

Neoadjuvant therapy followed by prostatectomy for clinically localized prostate cancer

The results of this assessment of the literature indicated that neoadjuvant therapy followed by prostatectomy may improve long-term outcomes for patients with high-risk localized disease. In addition, this approach provides a paradigm for evaluating the activity and mechanism of action of new agents as correlative studies are facilitated by the availability of tumor tissue before and after therapy. The authors determined that a multidisciplinary approach involving oncologists, urologists, and pathologists is critical to the success of this model. Recent and ongoing studies of neoadjuvant therapy followed by prostatectomy were reviewed.

A phase II study investigating the re-induction of endocrine sensitivity following chemotherapy in androgen-independent prostate cancer

When chemotherapy is used in androgen-independent prostate cancer (AIPC), androgen deprivation is continued despite its failure. In this study, we investigated whether it was possible to re-induce hormone sensitivity in previously castrate patients by stopping endocrine therapy during chemotherapy. A phase II prospective study investigated the effects of reintroduction of endocrine therapy after oral chemotherapy in 56 patients with AIPC, which was given without concurrent androgen deprivation. After chemotherapy, patients were given maximum androgen blockade until failure when treatment was switched to diethylstilbestrol and dexamethasone. Patients had already received these endocrine treatments in the same sequence before chemotherapy. All patients were castrate at the start of chemotherapy. Forty-three subsequently restarted endocrine therapy after the completion of chemotherapy. The median overall survival for these 43 patients from the time of restarting endocrine therapy was 7.7 months (95% confidence interval (CI): 3.7–10.9 months). Sixteen (37%) patients had a 50% PSA response to treatment, which was associated with improved overall survival (14.0 months vs 3.7 months P=0.003). Eight out of 12 patients who did not respond to diethylstilbestrol before chemotherapy did so post chemotherapy. Re-induction of hormone sensitivity can occur after chemotherapy in AIPC.

Mitogenic action of the androgen receptor sensitizes prostate cancer cells to taxane-based cytotoxic insult

Prostate cancer cells are dependent on androgen for growth and survival; as such, inhibition of androgen receptor (AR) activity is the first line of intervention for disseminated disease. Recently, specific cytotoxic agents have been shown to extend survival times in patients with advanced disease. Given the established ability of androgen to modify cell survival in prostate cancer cells, it is imperative to determine the effect of the hormonal environment on cytotoxic response. Here, we show that the response of prostate cancer cells to taxane-induced cell death is significantly enhanced by androgen stimulation in AR-positive, androgen-dependent prostate cancer cells. Similar results were observed on androgen-independent AR activation. By contrast, AR-positive yet androgen-independent or AR-negative cells were refractory to androgen influence on taxane function. The ability of androgen to potentiate taxane activity was dependent on its mitogenic capacity and was separable from overall AR activity, as coadministration of AR antagonists, G(1) cyclin-dependent kinase inhibitors, or high-dose (growth inhibitory) androgen nullified the proapoptotic function of androgen. Observed induction of cell death was attributed to caspase-dependent apoptosis and correlated with p53 activation. Combined, these data indicate that the cytotoxic effects of taxanes are substantially influenced by the hormonal environment and/or status of AR activity in prostate cancer cells and provide the foundation for refinement and optimization of cytotoxic intervention in prostate cancer.

The Case for Early Chemotherapy for the Treatment of Metastatic Disease

PURPOSE

Several important questions are raised by the data from Southwest Oncology Group 99-16 and TAX 327. What is the optimal timing of chemotherapy for metastatic hormone refractory prostate cancer? Should asymptomatic patients be treated? Is there a theoretical survival advantage for treatment for hormone sensitive prostate cancer? We reviewed arguments for the early use of docetaxel in the hormone sensitive and hormone naïve disease states.

MATERIALS AND METHODS

Androgen independent prostate cancer was traditionally viewed as a chemoresistant disease. At best palliation of bone pain but not improved survival could be achieved with the combination of mitoxantrone and prednisone. Median survival rates for chemotherapy in this disease state were reported to be between 10 and 12 months. Phase II studies administering docetaxel weekly or every 3 weeks as a single agent or in combination with estramustine demonstrated median survival rates of 14 to 23 months, which appeared to be an improvement over standard therapy. Consequently the 2 randomized trials, Southwest Oncology Group 99-16 and TAX 327, were designed to confirm the preliminary observations of improved survival with docetaxel based therapy.

RESULTS

TAX 327 and Southwest Oncology Group 99-16 treated asymptomatic as well as symptomatic patients. Thus, in contrast with mitoxantrone/prednisone, which was approved in symptomatic men with hormone refractory prostate cancer, the exact timing of the initiation of chemotherapy in docetaxel treated patients is still the subject of debate.

CONCLUSIONS

Studies should be performed to investigate the optimal timing of chemotherapy as well as sequencing with androgen ablation in patients at high risk for progression and death from metastatic prostate cancer. Prognostic factors for death that have been identified in patients with androgen independent prostate cancer are hemoglobin, alkaline phosphatase, visceral disease and performance status.