Dexamethasone enhances the cytotoxic effect of radioiodine therapy in prostate cancer cells expressing the sodium iodide symporter

Stress and thyroid gland

The review highlights the effects of acute and chronic stress on thyroid metabolism. Special attention is paid to the influence of stress and the direct effects of glucocorticoids on the thyroid status, the activities of thyrocyte iodine uptake, oxidation and organification as well as peripheral metabolism of thyroid hormones (deposition and transport of thyroid hormones, deiodinase activities in different tissues). The role of stress in the development of thyroid pathology is analysed and charestiristic features of thyroid function alterations during impaired functioning of the pitiutary-adrenal system are established. The mechanisms of the stress-induced impairments in thyroid functions are of interest for further research, taking into consideration serious consequences of thyroid deficiency for the body, even in subclinical thyroid insufficiency.

Targeted radioiodine therapy of neuroblastoma tumors following systemic nonviral delivery of the sodium iodide symporter gene

PURPOSE

We recently reported the significant therapeutic efficacy of radioiodine therapy in various tumor mouse models following transcriptionally targeted sodium iodide symporter (NIS) gene transfer. These studies showed the high potential of NIS as a novel diagnostic and therapeutic gene for the treatment of extrathyroidal tumors. As a next crucial step towards clinical application of NIS-mediated radionuclide therapy we aim at systemic delivery of the NIS gene to target extrathyroidal tumors even in the metastatic stage.

EXPERIMENTAL DESIGN

In the current study, we used synthetic polymeric vectors based on pseudodendritic oligoamines with high intrinsic tumor affinity (G2-HD-OEI) to target a NIS-expressing plasmid (CMV-NIS-pcDNA3) to neuroblastoma (Neuro2A) cells.

RESULTS

Incubation with NIS-containing polyplexes (G2-HD-OEI/NIS) resulted in a 51-fold increase in perchlorate-sensitive iodide uptake activity in Neuro2A cells in vitro. Through (123)I-scintigraphy and ex vivo gamma counting Neuro2A tumors in syngeneic A/J mice were shown to accumulate 8% to 13% ID/g (123)I with a biological half-life of 13 hours, resulting in a tumor-absorbed dose of 247 mGy/MBq (131)I after i.v. application of G2-HD-OEI/NIS. Nontarget organs, including liver, lung, kidneys, and spleen revealed no significant iodide uptake. Moreover, two cycles of systemic NIS gene transfer followed by (131)I application (55.5 MBq) resulted in a significant delay in tumor growth associated with markedly improved survival.

CONCLUSIONS

In conclusion, our data clearly show the high potential of novel pseudodendritic polymers for tumor-specific NIS gene delivery after systemic application, opening the prospect of targeted NIS-mediated radionuclide therapy of nonthyroidal tumors even in metastatic disease.

Differential expression of determinants of glucocorticoid sensitivity in androgen-dependent and androgen-independent human prostate cancer cell lines

Glucocorticoids (GCs) are widely used for the treatment of hormone refractory prostate cancer. However, few data are available on the expression and regulation of glucocorticoid and mineralocorticoid receptors (GR and MR) and 11beta-hydroxysteroid dehydrogenase (11beta-HSD) 1 and -2 activities in prostate cancer cells. Here we show that GR is expressed in both the androgen-independent PC-3 cell line and, at very low levels, in the androgen-dependent LNCaP cells, and MR is expressed in both cell lines. IL-1beta increased GR expression in both cell lines. In LNCaP cells IL-1beta also increased MR expression. Significant 11beta-HSD oxidase activity and 11beta-HSD2 protein were found in LNCaP cells, but not in PC3 cells, and no ketoreductase activity was detected in either cell lines. GR function was assessed by measuring the inhibitory effect of dexamethasone on constitutive and IL-1beta-inducible IL-6 and osteoprotegerin (OPG) production. In PC-3 cells, IL-1beta stimulated IL-6 and OPG release, and dexamethasone dose-dependently inhibited IL-1beta-inducible IL-6 release, and constitutive and IL-1beta-inducible OPG release. In LNCaP cells, IL-1beta stimulated only OPG release. While dexamethasone was ineffective, cortisol dose-dependently inhibited IL-1beta-inducible OPG release. Eplerenone (Epl), a selective mineralocorticoid antagonist, reverted this effect. We conclude that different patterns of expression of receptors and 11beta-HSD activity were associated with different responsiveness to GCs in terms of regulated gene expression. GR and MR expression may vary as a function not only of the malignant phenotype, but also of local conditions such as the degree of inflammation. Inhibition of IL-6 and OPG release by GCs may contribute to the antitumor efficacy in prostate cancer.

The potential of 211Astatine for NIS-mediated radionuclide therapy in prostate cancer

PURPOSE

We reported recently the induction of selective iodide uptake in prostate cancer cells (LNCaP) by prostate-specific antigen (PSA) promoter-directed sodium iodide symporter (NIS) expression that allowed a significant therapeutic effect of (131)I. In the current study, we studied the potential of the high-energy alpha-emitter (211)At, also transported by NIS, as an alternative radionuclide after NIS gene transfer in tumors with limited therapeutic efficacy of (131)I due to rapid iodide efflux.

METHODS

We investigated uptake and therapeutic efficacy of (211)At in LNCaP cells stably expressing NIS under the control of the PSA promoter (NP-1) in vitro and in vivo.

RESULTS

NP-1 cells concentrated (211)At in a perchlorate-sensitive manner, which allowed a dramatic therapeutic effect in vitro. After intraperitoneal injection of (211)At (1 MBq), NP-1 tumors accumulated approximately 16% ID/g (211)At (effective half-life 4.6 h), which resulted in a tumor-absorbed dose of 1,580+/-345 mGy/MBq and a significant tumor volume reduction of up to 82+/-19%, while control tumors continued their growth exponentially.

CONCLUSIONS

A significant therapeutic effect of (211)At has been demonstrated in prostate cancer after PSA promoter-directed NIS gene transfer in vitro and in vivo suggesting a potential role for (211)At as an attractive alternative radioisotope for NIS-targeted radionuclide therapy, in particular in smaller tumors with limited radionuclide retention time.

Dexamethasone suppresses DU145 cell proliferation and cell cycle through inhibition of the extracellular signal-regulated kinase 1/2 pathway and cyclin D1 expression

AIM

To determine the mechanisms of glucocorticoids in inhibiting advanced prostate cancer growth.

METHODS

The cell proliferation and cell cycle of prostate cancer DU145 cells following dexamethasone treatment were determined by proliferation assay and fluorescence-activated cell sorter. Western blot analysis was carried out to evaluate the effects of dexamethasone on phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and expression of cyclin D1 in DU145 cells with or without glucocorticoid receptor (GR) antagonist RU486. Reverse transcription-polymerase chain reaction verified the expression of GR mRNA in DU145 cells.

RESULTS

Dexamethasone significantly inhibited DU145 cell proliferation at the G(0)/G(1) phase. Western blot analysis showed a dramatic reduction of ERK1/2 activity and cyclin D1 expression in dexamethasone-treated cells. The decreased phosphorylation of ERK1/2 in dexamethasone-treated cells was attenuated by GR blockade. Additionally, the effects of dexamethasone in inhibiting cyclin D1 expression were altered by GR blockade.

CONCLUSION

Dexamethasone suppresses DU145 cell proliferation and cell cycle, and the underlying mechanisms are through the inhibition of phosphorylation of ERK1/2 and cyclin D1 expression. The inhibition of ERK1/2 phosphorylation and cyclin D1 expression is attenuated by GR blockade, suggesting that GR regulates ERK1/2 and cyclin D1 pathways. These observations suggest that dexamethasone has a potential clinical application in prostate cancer therapy.

Application of 188rhenium as an alternative radionuclide for treatment of prostate cancer after tumor-specific sodium iodide symporter gene expression

CONTEXT

We reported recently the induction of iodide accumulation in prostate cancer cells (LNCaP) by prostate-specific antigen promoter-directed sodium iodide symporter (NIS) expression that allowed a significant therapeutic effect of (131)iodine ((131)I). These data demonstrated the potential of the NIS gene as a novel therapeutic gene, although in some extrathyroidal tumors, therapeutic efficacy may be limited by rapid iodide efflux due to a lack of iodide organification.

OBJECTIVE

In the current study, we therefore studied the potential of (188)rhenium ((188)Re), as an alternative radionuclide, also transported by NIS, with a shorter half-life and higher energy beta-particles than (131)I.

RESULTS

NIS-transfected LNCaP cells (NP-1) concentrated 8% of the total applied activity of (188)Re as compared with 16% of (125)I, which was sufficient for a therapeutic effect in an in vitro clonogenic assay. gamma-Camera imaging of NP-1 cell xenografts in nude mice revealed accumulation of 8-16% injected dose (ID)/g (188)Re (biological half-life 12.9 h), which resulted in a 4.7-fold increased tumor absorbed dose (450 mGy/MBq) for (188)Re as compared with (131)I. After application of 55.5 MBq (131)I or (188)Re, smaller tumors showed a similar average volume reduction of 86%, whereas in larger tumors volume reduction was significantly increased from 73% after (131)I treatment to 85% after application of (188)Re.

CONCLUSION

Although in smaller prostate cancer xenografts both radionuclides seemed to be equally effective after prostate-specific antigen promoter-mediated NIS gene delivery, a superior therapeutic effect has been demonstrated for (188)Re in larger tumors.

Phase II study evaluating oral triamcinolone in patients with androgen-independent prostate cancer

OBJECTIVES

To assess the effect of triamcinolone administration on the serum prostate-specific antigen (PSA) response and the time to progression in patients with androgen-independent prostate cancer (AIPC).

METHODS

Patients with AIPC were prospectively treated with oral triamcinolone 4 mg twice daily, and their serum PSA and cortisol levels were measured monthly. Patients with greater than 25% increases in serum PSA from baseline were considered to have progressive disease and were removed from the study. Those patients who had a decrease in serum PSA levels or stable disease continued in the study until disease progression. Bone scans were obtained every 12 weeks and at progression.

RESULTS

Twenty-four patients with AIPC were treated from November 2002 to June 2004. A partial response with a more than 50% decrease in serum PSA level was seen in 29%. Another 21% achieved stable disease. No statistically significant difference was found in the time to progression in the partial responders and patients with stable disease. The median time to progression in both groups was 7.5 months. Treatment was well tolerated without any grade 3 or 4 toxicity.

CONCLUSIONS

Oral triamcinolone was well tolerated by patients with AIPC, with 50% of the patients exhibiting a good response to therapy in terms of serum PSA level and time to progression.

Dexamethasone stimulation of retinoic Acid-induced sodium iodide symporter expression and cytotoxicity of 131-I in breast cancer cells

CONTEXT

The sodium iodide symporter (NIS) mediates the active iodide uptake in the thyroid gland as well as lactating breast tissue. Recently induction of functional NIS expression was reported in the estrogen receptor-positive human breast cancer cell line MCF-7 by all-trans retinoic acid (atRA) treatment in vitro and in vivo, which might offer the potential to treat breast cancer with radioiodine.

OBJECTIVE

In the current study, we examined the effect of dexamethasone (Dex) on atRA-induced NIS expression and therapeutic efficacy of 131-I in MCF-7 cells.

DESIGN

For this purpose, NIS mRNA and protein expression levels in MCF-7 cells were examined by Northern and Western blot analysis after incubation with Dex (10(-9) to 10(-7) m) in the presence of atRA (10(-6) m) as well as immunostaining using a mouse monoclonal human NIS-specific antibody. In addition, NIS functional activity was measured by iodide uptake and efflux assay, and in vitro cytotoxicity of 131-I was examined by in vitro clonogenic assay.

RESULTS

After incubation with Dex in the presence of atRA, NIS mRNA levels in MCF-7 cells were stimulated up to 11-fold in a concentration-dependent manner, whereas NIS protein levels increased up to 16-fold and iodide accumulation was stimulated up to 3- to 4-fold. Furthermore, iodide efflux was modestly decreased after stimulation with Dex in the presence of atRA. Furthermore, in the in vitro clonogenic assay, selective cytotoxicity of 131-I was significantly increased from approximately 17% in MCF-7 cells treated with atRA alone to 80% in MCF-7 cells treated with Dex in the presence of atRA.

CONCLUSION

Treatment with Dex in the presence of atRA significantly increases functional NIS expression levels in addition to inhibiting iodide efflux, resulting in an enhanced selective killing effect of 131-I in MCF-7 breast cancer cells.