New developments in the pharmacological management of prostate cancer

Efficacy of a second line luteinizing hormone-releasing hormone agonist after advanced prostate cancer biochemical recurrence

PURPOSE

Men with castrate resistant prostate cancer have limited treatment options. Although luteinizing hormone-releasing hormone agonists are in the same class, they are slightly different in their pharmacology. We determined whether rechallenging patients with prostate cancer, who were receiving a luteinizing hormone-releasing hormone analogue but had progression, with a different luteinizing hormone-releasing hormone analogue (goserelin or leuprolide acetate) would result in a prostate specific antigen response. Secondary objectives were to calculate the PSA response and determine whether sequence order impacted the response.

MATERIALS AND METHODS

We performed a retrospective, ethics approved review of the records of patients with prostate cancer at multiple institutions who received a luteinizing hormone-releasing hormone analogue (goserelin or leuprolide acetate), experienced progression, as measured by 2 consecutive prostate specific antigen increases, and were rechallenged with the other analogue (goserelin or leuprolide acetate). Prostate specific antigen and relevant clinical data were obtained and statistical analysis was done.

RESULTS

Of 39 available men 27 (69%) had decreased prostate specific antigen after 3 months of switching regimens. The median change in prostate specific antigen was -1.5 (IQR -10.0, 0.8), indicating a statistically significant decrease (p=0.01). The median percent prostate specific antigen change for leuprolide acetate to goserelin was -69.3% (IQR -81.5, 26.2) and for goserelin to leuprolide acetate it was -6.4% (IQR -61.7, 21.8, p=0.05). Median time to a subsequent prostate specific antigen increase was 5.2 months (95% CI 3.5-17.4).

CONCLUSIONS

Prostate specific antigen decreased after switching luteinizing hormone-releasing hormone therapies. This decrease appeared most significant in the group that switched from leuprolide acetate to goserelin. The duration of response after switching was approximately 5 months. The study is limited by its retrospective nature but should encourage prospective evaluation of this observation.

Caffeic acid phenethyl ester-induced PC-3 cell apoptosis is caspase-dependent and mediated through the loss of inhibitors of apoptosis proteins

OBJECTIVE

To investigate the effects of a novel agent, caffeic acid phethyl ester (CAPE) on nuclear factor (NF)-kappaB activation and apoptosis in the androgen-independent PC3 prostate cancer cell line.

MATERIALS AND METHODS

PC-3 cells were assessed for NF-kappaB activation induced by paclitaxel and tumour necrosis factor-alpha (TNF-alpha), using a p65 enzyme-linked immunosorbent assay, with or without CAPE treatment. The corresponding apoptosis was assessed with propidium iodide DNA staining using flow cytometry. The pan-caspase inhibitor Z-VAD-FMK was used to investigate the mechanism of apoptosis. Alterations in the expression of inhibitor of apoptosis proteins (IAP), cIAP-1, cIAP-2 and XIAP, were detected using western blot analysis.

RESULTS

CAPE prevented paclitaxel and TNFalpha-mediated NF-kappaB activation. Its ability to induce apoptosis in a dose-dependent manner was associated with the loss of cIAP-1, cIAP-2 and XIAP expression. Pretreatment with Z-VAD-FMK prevented CAPE-induced apoptosis and the loss of the IAPs.

CONCLUSIONS

CAPE is an effective inhibitor of NF-kappaB activation in PC-3 cells, but the mechanism of apoptosis, and the corresponding loss of IAP expression, is caspase-dependent.

Endothelin-1 production by prostate cancer cell lines is up-regulated by factors involved in cancer progression and down-regulated by androgens

BACKGROUND

Recent data demonstrate that endothelin-1 (ET-1) concentration increases in plasma of men with advanced, hormone-refractory prostate adenocarcinoma. In addition, ET-1 is involved in osteblastic remodelling and new bone formation, suggesting a role for this vasoactive peptide in the metastatic progression of prostate cancer to the bone.

METHODS

We investigated the regulation of ET-1 expression in androgen-sensitive and insensitive prostate cancer cell lines by androgens and several factors involved in progression of prostate cancer (EGF) and bone remodelling (TGFbeta-1, IL1-alpha and IGF-1).

RESULTS

Northern analysis and radio immunoassay demonstrated that all the ET-1 pathways are tuned off in the androgen-sensitive LNCaP cell line when compared to the androgen-insensitive PC-3 and DU145. In PC-3 cells transfected with a full-length androgen receptor expression vector (PC-3-AR), treatment with androgens reduced gene expression and secretion of ET-1 without affecting the gene expression of ET-3. Collectively, these data support a role for androgens in the regulation of ET-1 production by prostate adenocarcinoma cells. In PC-3 and DU145 cells, ET-1 gene expression and secretion were up-regulated by TGFbeta-1, EGF and IL1-alpha, whereas IGF-1 was ineffective. Conversely, none of the treatments affected ECE-1 or ET-3 gene expression.

CONCLUSIONS

In conclusion, ET-1 production by prostate adenocarcinoma cells is down-regulated by androgens and up-regulated by factors involved in tumour progression indicating a role for this peptide in the biology of prostate cancer. In view of the role exerted by ET-1 in the process of bone metastasis, our data suggest the use of ET-1 receptor antagonists in the treatment of advanced prostate cancer.