Re-induction of hormone sensitivity to diethylstilboestrol in androgen refractory prostate cancer patients following chemotherapy

Diethylstilboestrol for the treatment of prostate cancer: past, present and future

The aim of this review was to discuss the most recent data from current trials of diethylstilboestrol (DES) to identify its present role in advanced prostate cancer treatment as new hormonal therapies emerge. The most relevant clinical studies using DES in castration-refractory prostate cancer (CRPC) were identified from the literature. The safety, efficacy, outcomes and mechanisms of action are summarized. In the age of chemotherapy this review highlights the efficacy of oestrogen therapy in CRPC. The optimal point in the therapeutic pathway at which DES should be prescribed remains to be established.

Drug rechallenge and treatment beyond progression--implications for drug resistance

The established dogma in oncology for managing recurrent or refractory disease dictates that therapy is changed at disease progression, because the cancer is assumed to have become drug-resistant. Drug resistance, whether pre-existing or acquired, is largely thought to be a stable and heritable process; thus, reuse of therapeutic agents that have failed is generally contraindicated. Over the past few decades, clinical evidence has suggested a role for unstable, non-heritable mechanisms of acquired drug resistance pertaining to chemotherapy and targeted agents. There are many examples of circumstances where patients respond to reintroduction of the same therapy (drug rechallenge) after a drug holiday following disease relapse or progression during therapy. Additional, albeit limited, evidence suggests that, in certain circumstances, continuing a therapy beyond disease progression can also have antitumour activity. In this Review, we describe the anticancer agents used in these treatment strategies and discuss the potential mechanisms explaining the apparent tumour re-sensitization with reintroduced or continued therapy. The extensive number of malignancies and drugs that challenge the custom of permanently switching to different drugs at each line of therapy warrants a more in-depth examination of the definitions of disease progression and drug resistance and the resulting implications for patient care.

Drug rechallenge and treatment beyond progression--implications for drug resistance

The established dogma in oncology for managing recurrent or refractory disease dictates that therapy is changed at disease progression, because the cancer is assumed to have become drug-resistant. Drug resistance, whether pre-existing or acquired, is largely thought to be a stable and heritable process; thus, reuse of therapeutic agents that have failed is generally contraindicated. Over the past few decades, clinical evidence has suggested a role for unstable, non-heritable mechanisms of acquired drug resistance pertaining to chemotherapy and targeted agents. There are many examples of circumstances where patients respond to reintroduction of the same therapy (drug rechallenge) after a drug holiday following disease relapse or progression during therapy. Additional, albeit limited, evidence suggests that, in certain circumstances, continuing a therapy beyond disease progression can also have antitumour activity. In this Review, we describe the anticancer agents used in these treatment strategies and discuss the potential mechanisms explaining the apparent tumour re-sensitization with reintroduced or continued therapy. The extensive number of malignancies and drugs that challenge the custom of permanently switching to different drugs at each line of therapy warrants a more in-depth examination of the definitions of disease progression and drug resistance and the resulting implications for patient care.

Does androgen-ablation therapy (AAT) associated autophagy have a pro-survival effect in LNCaP human prostate cancer cells?

WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: Androgen-ablation therapy (AAT) and chemotherapy are commonly used to treat incurable prostate cancer. To improve outcome, there is major on-going research to develop more effective treatments with less toxicity. Autophagy has been suggested from previous studies to play a potential role in cell survival and may be associated with resistance to chemotherapy. Autophagy is known to be upregulated by nutrient starvation or AAT in prostate cancer. However, its functional impact is not fully known. The present study describes the potential synergism between the blockade of autophagy and AAT alone or AAT combined with taxane chemotherapy. Hence, future combined treatment options are warranted to further investigate the clinical impact of autophagy suppression as a treatment strategy.

OBJECTIVE

To study the cellular effects of the anti-androgen bicalutamide on autophagy and its potential impact on response to androgen-ablation therapy (AAT) alone or combined with docetaxel chemotherapy in human prostate cancer LNCaP cells.

MATERIALS AND METHODS

LNCaP cells were treated with bicalutamide ± docetaxel, and cellular effects were assayed: lipidated LC3 (a microtubule-associated protein) for autophagy and its trafficking to fuse with lysosome; flow cytometry using propidium iodide or caspase 3 for cell death; and sulforhodamine B assay for cell growth.

RESULTS

Bicalutamide treatment enhanced autophagy in LNCaP cells with increased level of autophagosome coupled with an altered cellular morphology reminiscent of neuroendocrine differentiation. Consistent with the literature on the interaction between androgen receptor activation and taxane chemotherapy, bicalutamide diminished docetaxel mediated cytotoxicity. Significantly, pharmacological inhibition of autophagy with 3-methyladenine significantly enhanced the efficacy cell kill mediated by AAT ± docetaxel.

CONCLUSION

Autophagy associated with bicalutamide treatment in LNCaP cells may have a pro-survival effect and strategy to modulate autophagy may have a potential therapeutic value.

Low-dose diethylstilbestrol for the treatment of advanced prostate cancer

OBJECTIVES

The purpose of this study was to assess the efficacy and safety of low-dose (1 mg) daily diethylstilbestrol (DES) for the treatment of castrate-resistant prostate cancer (CRPC).

MATERIALS AND METHODS

A retrospective chart review was performed on patients treated with low-dose DES who had CRPC despite anti-androgen withdrawal. The study population consists of 63 patients treated in the pre- and post-chemotherapy settings based on a database review; 58 had sufficient data for efficacy, all were analyzed for safety.

RESULTS

A PSA decrease of ≥50% was observed in 19 of 49 pre-chemotherapy patients (39%) with a median time to progression (TTP) of 30 weeks (95% CI, 21.9, 68.7). A PSA decrease of <50% was seen in another 16 patients (33%) with a median TTP of 16.4 weeks (95% CI, 13.0, 37.6). Fourteen patients (29%) had progressive disease by PSA testing; their median TTP was 6.9 weeks (95% CI, 5.6, 12.9). Thromboembolic events included 2 patients with DVTs and 1 patient who developed primary fibrinolysis syndrome. Additional adverse events included gynecomastia in 37 of 63 patients (59%). Secondary observations included PSA responses in 3 of 9 patients treated with DES after chemotherapy progression and a high rate of PSA responses in patients re-treated with DES after a drug holiday.

CONCLUSIONS

Low-dose DES is safe and effective in a modern cohort of men with CRPC despite anti-androgen treatment. Its potential role in the post-chemotherapy setting and the suggestion of efficacy on re-challenge merits additional consideration.