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MDM2 antagonists boost antitumor effect of androgen withdrawal: implications for therapy of prostate cancer.

Tovar C, Higgins B, Kolinsky K, Xia M, Packman K, Heimbrook DC, Vassilev LT - Mol. Cancer (2011)

Bottom Line: Using charcoal-stripped serum as a cellular model of androgen deprivation, we show an increased apoptotic effect of p53 activation by nutlin-3a in the androgen-dependent LNCaP cells and to a lesser extent in androgen-independent but responsive 22Rv1 cell line.This effect is due, at least in part, to an enhanced downregulation of AR expression by activated p53.Since majority of prostate tumors express wild-type p53, its activation by MDM2 antagonists in combination with androgen depletion may offer an efficacious new approach to prostate cancer therapy.

View Article: PubMed Central - HTML - PubMed

Affiliation: Discovery Oncology, Roche Research Center, Hoffmann-La Roche Inc., Nutley, NJ 07110, USA.

ABSTRACT

Background: Hormone therapy is the standard of care for newly diagnosed or recurrent prostate cancers. It uses anti-androgen agents, castration, or both to eliminate cancer promoting effect of testicular androgen. The p53 tumor suppressor controls a major pathway that can block cell proliferation or induce apoptosis in response to diverse forms of oncogenic stress. Activation of the p53 pathway in cancer cells expressing wild-type p53 has been proposed as a novel therapeutic strategy and recently developed MDM2 antagonists, the nutlins, have validated this in preclinical models of cancer. The crosstalk between p53 and androgen receptor (AR) signaling suggest that p53 activation could augment antitumor outcome of androgen ablation in prostate cancer. Here, we test this hypothesis in vitro and in vivo using the MDM2 antagonist, nutlin-3 and the p53 wild-type prostate cancer cell line, LNCaP.

Results: Using charcoal-stripped serum as a cellular model of androgen deprivation, we show an increased apoptotic effect of p53 activation by nutlin-3a in the androgen-dependent LNCaP cells and to a lesser extent in androgen-independent but responsive 22Rv1 cell line. This effect is due, at least in part, to an enhanced downregulation of AR expression by activated p53. In vivo, androgen deprivation followed by two weeks of nutlin administration in LNCaP-bearing nude mice led to a greater tumor regression and dramatically increased survival.

Conclusions: Since majority of prostate tumors express wild-type p53, its activation by MDM2 antagonists in combination with androgen depletion may offer an efficacious new approach to prostate cancer therapy.

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Related in: MedlinePlus

Nutlin-3a greatly enhances antitumor activity of androgen deprivation in vivo. A) LNCaP cells were grown subcutaneously in pre-castrated male athymic nude mice in the presence of testosterone pellets until reaching approximately 400 mm3 on average. Mice were administered Nutlin-3a at 200 mg/kg bid (n = 10) or testosterone pellets were removed to simulate androgen ablation (n = 20). Additional mice were treated with a combination of ablation + Nutlin-3a at 200 mg/kg bid orally for 14 days (n = 20). Control mice were dosed with vehicle for 14 days + sham pellet removal under anesthesia (n = 10). B) PSA levels reflect changes in tumor volume. At day 42, five random mice in each group were bled and PSA levels ± SD were determined. C) Combination of nutlin and androgen deprivation increases lifespan of mice. After completion of treatment, mice were monitored for over a year and ILS was calculated by the Kaplan-Meier formula. Survival was calculated using a cut-off of 1000 mm3.
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Figure 6: Nutlin-3a greatly enhances antitumor activity of androgen deprivation in vivo. A) LNCaP cells were grown subcutaneously in pre-castrated male athymic nude mice in the presence of testosterone pellets until reaching approximately 400 mm3 on average. Mice were administered Nutlin-3a at 200 mg/kg bid (n = 10) or testosterone pellets were removed to simulate androgen ablation (n = 20). Additional mice were treated with a combination of ablation + Nutlin-3a at 200 mg/kg bid orally for 14 days (n = 20). Control mice were dosed with vehicle for 14 days + sham pellet removal under anesthesia (n = 10). B) PSA levels reflect changes in tumor volume. At day 42, five random mice in each group were bled and PSA levels ± SD were determined. C) Combination of nutlin and androgen deprivation increases lifespan of mice. After completion of treatment, mice were monitored for over a year and ILS was calculated by the Kaplan-Meier formula. Survival was calculated using a cut-off of 1000 mm3.

Mentions: Finally, we examined if androgen ablation combined with nutlin-3a could enhance anti-tumor activity against established human prostate tumor xenografts (Figure 6A). To this end, pre-castrated nude mice were implanted with sustained-release testosterone pellets 5 days prior to injection of LNCaP cells. Tumors were fully established with an average starting tumor volume of approximately 400 mm3 in each group. Mice were administered an optimal oral dose of nutlin-3a at 200 mg/kg twice a day (bid) for 14 days. Others were treated with removal of testosterone pellets as a model of androgen ablation. Additional mice were treated with a combination of ablation + nutlin-3a. Control mice were dosed with vehicle + sham pellet removal. Nutlin was well tolerated in all groups with no significant body weight loss in any group throughout the study. Tumor regressions were observed in all groups relative to vehicle. Nutlin-treated animals had 6/10 partial regressions, androgen ablation caused 20/20 partial regressions, and combination of nutlin + ablation yielded 13/20 partial regressions including 7/20 complete regressions (no complete regressions were observed in the other groups). At day 42 post tumor cell inoculation (last day of nutlin treatment), measurement of prostate specific androgen (PSA) in serum showed a 68% decrease with nutlin treatment alone compared to vehicle control (Figure 6B). Androgen ablation and combination treatment reduced serum PSA levels 94% and 98%, respectively.


MDM2 antagonists boost antitumor effect of androgen withdrawal: implications for therapy of prostate cancer.

Tovar C, Higgins B, Kolinsky K, Xia M, Packman K, Heimbrook DC, Vassilev LT - Mol. Cancer (2011)

Nutlin-3a greatly enhances antitumor activity of androgen deprivation in vivo. A) LNCaP cells were grown subcutaneously in pre-castrated male athymic nude mice in the presence of testosterone pellets until reaching approximately 400 mm3 on average. Mice were administered Nutlin-3a at 200 mg/kg bid (n = 10) or testosterone pellets were removed to simulate androgen ablation (n = 20). Additional mice were treated with a combination of ablation + Nutlin-3a at 200 mg/kg bid orally for 14 days (n = 20). Control mice were dosed with vehicle for 14 days + sham pellet removal under anesthesia (n = 10). B) PSA levels reflect changes in tumor volume. At day 42, five random mice in each group were bled and PSA levels ± SD were determined. C) Combination of nutlin and androgen deprivation increases lifespan of mice. After completion of treatment, mice were monitored for over a year and ILS was calculated by the Kaplan-Meier formula. Survival was calculated using a cut-off of 1000 mm3.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3094321&req=5

Figure 6: Nutlin-3a greatly enhances antitumor activity of androgen deprivation in vivo. A) LNCaP cells were grown subcutaneously in pre-castrated male athymic nude mice in the presence of testosterone pellets until reaching approximately 400 mm3 on average. Mice were administered Nutlin-3a at 200 mg/kg bid (n = 10) or testosterone pellets were removed to simulate androgen ablation (n = 20). Additional mice were treated with a combination of ablation + Nutlin-3a at 200 mg/kg bid orally for 14 days (n = 20). Control mice were dosed with vehicle for 14 days + sham pellet removal under anesthesia (n = 10). B) PSA levels reflect changes in tumor volume. At day 42, five random mice in each group were bled and PSA levels ± SD were determined. C) Combination of nutlin and androgen deprivation increases lifespan of mice. After completion of treatment, mice were monitored for over a year and ILS was calculated by the Kaplan-Meier formula. Survival was calculated using a cut-off of 1000 mm3.
Mentions: Finally, we examined if androgen ablation combined with nutlin-3a could enhance anti-tumor activity against established human prostate tumor xenografts (Figure 6A). To this end, pre-castrated nude mice were implanted with sustained-release testosterone pellets 5 days prior to injection of LNCaP cells. Tumors were fully established with an average starting tumor volume of approximately 400 mm3 in each group. Mice were administered an optimal oral dose of nutlin-3a at 200 mg/kg twice a day (bid) for 14 days. Others were treated with removal of testosterone pellets as a model of androgen ablation. Additional mice were treated with a combination of ablation + nutlin-3a. Control mice were dosed with vehicle + sham pellet removal. Nutlin was well tolerated in all groups with no significant body weight loss in any group throughout the study. Tumor regressions were observed in all groups relative to vehicle. Nutlin-treated animals had 6/10 partial regressions, androgen ablation caused 20/20 partial regressions, and combination of nutlin + ablation yielded 13/20 partial regressions including 7/20 complete regressions (no complete regressions were observed in the other groups). At day 42 post tumor cell inoculation (last day of nutlin treatment), measurement of prostate specific androgen (PSA) in serum showed a 68% decrease with nutlin treatment alone compared to vehicle control (Figure 6B). Androgen ablation and combination treatment reduced serum PSA levels 94% and 98%, respectively.

Bottom Line: Using charcoal-stripped serum as a cellular model of androgen deprivation, we show an increased apoptotic effect of p53 activation by nutlin-3a in the androgen-dependent LNCaP cells and to a lesser extent in androgen-independent but responsive 22Rv1 cell line.This effect is due, at least in part, to an enhanced downregulation of AR expression by activated p53.Since majority of prostate tumors express wild-type p53, its activation by MDM2 antagonists in combination with androgen depletion may offer an efficacious new approach to prostate cancer therapy.

View Article: PubMed Central - HTML - PubMed

Affiliation: Discovery Oncology, Roche Research Center, Hoffmann-La Roche Inc., Nutley, NJ 07110, USA.

ABSTRACT

Background: Hormone therapy is the standard of care for newly diagnosed or recurrent prostate cancers. It uses anti-androgen agents, castration, or both to eliminate cancer promoting effect of testicular androgen. The p53 tumor suppressor controls a major pathway that can block cell proliferation or induce apoptosis in response to diverse forms of oncogenic stress. Activation of the p53 pathway in cancer cells expressing wild-type p53 has been proposed as a novel therapeutic strategy and recently developed MDM2 antagonists, the nutlins, have validated this in preclinical models of cancer. The crosstalk between p53 and androgen receptor (AR) signaling suggest that p53 activation could augment antitumor outcome of androgen ablation in prostate cancer. Here, we test this hypothesis in vitro and in vivo using the MDM2 antagonist, nutlin-3 and the p53 wild-type prostate cancer cell line, LNCaP.

Results: Using charcoal-stripped serum as a cellular model of androgen deprivation, we show an increased apoptotic effect of p53 activation by nutlin-3a in the androgen-dependent LNCaP cells and to a lesser extent in androgen-independent but responsive 22Rv1 cell line. This effect is due, at least in part, to an enhanced downregulation of AR expression by activated p53. In vivo, androgen deprivation followed by two weeks of nutlin administration in LNCaP-bearing nude mice led to a greater tumor regression and dramatically increased survival.

Conclusions: Since majority of prostate tumors express wild-type p53, its activation by MDM2 antagonists in combination with androgen depletion may offer an efficacious new approach to prostate cancer therapy.

Show MeSH
Related in: MedlinePlus