Treatment with rhenium-188-perrhenate and iodine-131 of NIS-expressing mammary cancer in a mouse model remarkably inhibited tumor growth

Evaluation of [18F]tetrafluoroborate as a Potential PET Imaging Agent in a Sodium Iodide Symporter-Transfected Cell Line A549 and Endogenous NIS-Expressing Cell Lines MKN45 and K1

[¹⁸F]tetrafluoroborate (TFB) has been introduced as the ¹⁸F-labeled PET imaging probe for the human sodium iodide symporter (NIS). Noninvasive NIS imaging using [¹⁸F]TFB has received much interest in recent years for evaluating various NIS-expressing tumors. Cancers are a global concern with enormous implications; therefore, improving diagnostic methods for accurate detection of cancer is extremely important. Our aim was to investigate the PET imaging capabilities of [¹⁸F]TFB in NIS-transfected lung cell line A549 and endogenous NIS-expressing tumor cells, such as thyroid cancer K1 and gastric cancer MKN45, and broaden its application in the medical field. Western blot and flow cytometry were used to assess the NIS expression level. Radioactivity counts of [¹⁸F]TFB, in vitro, in the three tumor cells were substantially higher than those in the KI inhibition group in the uptake experiment. In vivo PET imaging clearly delineated the three tumors based on the specific accumulation of [¹⁸F]TFB in a mouse model. Ex vivo biodistribution investigation showed high [¹⁸F]TFB absorption in the tumor location, which was consistent with the PET imaging results. These results support the use of NIS-transfected lung cell line A549 and NIS-expressing tumor cells MKN45 and K1, to investigate probing capabilities of [¹⁸F]TFB. We also demonstrate, for the first time, the feasibility of [¹⁸F]TFB in diagnosing stomach cancer. In conclusion, this study illustrates the promising future of [¹⁸F]TFB for tumor diagnosis and NIS reporter imaging.

Gut Microbiota as a Positive Potential Therapeutic Factor in Carcinogenesis: an Overview of Microbiota-Targeted Therapy

Cancer therapeutic methods comprising chemotherapy, radiotherapy, and surgery are so routine in cancer treatment. Remarkably, there are several personal features which affect the effectiveness of such treatments including nutrition, microbiome diversity, and physical activity which has distinct significant roles during and after therapies along with their bilateral connections. In this way, the ability of gut microbiota36 in modulating the efficacy of chemotherapeutic medications in cancer and other types of disorders is of great importance. In addition, the role of dietary, probiotic, and synthetically engineered bacteria in manipulating and optimizing the gut microbiota is of interest. Conspicuously, the correlation between the commensal microbiota and also host can regulate the physiological activities comprising the immunity system and inflammatory agents and it is scanned in the category of cancers. Bacterial species have been employed in cancer therapy; commensal microbes posse a key beneficial role in this field. Practically, the microbiota has this potential to accelerate and modulates a certain response by priming in order to release the pro-inflammatory agents. We would like to discuss these vital factors in this review as gut microbiota has the potential to be the main option for personalized cancer treatment strategies in the future. Meaning, this novel data present clinical promising feasibilities of modulating cancer therapy with using microbiota.

Improved Noninvasive In Vivo Tracking of AAV-9 Gene Therapy Using the Perchlorate-Resistant Sodium Iodide Symporter from Minke Whale

The sodium iodide symporter (NIS) is widely used as a reporter gene to noninvasively monitor the biodistribution and durability of vector-mediated gene expression via gamma scintigraphy, single-photon emission computed tomography (SPECT), and positron-emission tomography (PET). However, the approach is limited by background signal due to radiotracer uptake by endogenous NIS-expressing tissues. In this study, using the SPECT tracer pertechnetate (^99mTcO₄) and the PET tracer tetrafluoroborate (B¹⁸F₄), in combination with the NIS inhibitor perchlorate, we compared the transport properties of human NIS and minke whale (Balaenoptera acutorostrata scammoni) NIS in vitro and in vivo. Based on its relative resistance to perchlorate, the NIS protein from minke whale appeared to be the superior candidate reporter gene. SPECT and PET imaging studies in nude mice challenged with NIS-encoding adeno-associated virus (AAV)-9 vectors confirmed that minke whale NIS, in contrast to human and endogenous mouse NIS, continues to function as a reliable reporter even when background radiotracer uptake by endogenous NIS is blocked by perchlorate.

Rhenium-188 Labeled Radiopharmaceuticals: Current Clinical Applications in Oncology and Promising Perspectives

Rhenium-188 (188Re) is a high energy beta-emitting radioisotope with a short 16.9 h physical half-life, which has been shown to be a very attractive candidate for use in therapeutic nuclear medicine. The high beta emission has an average energy of 784 keV and a maximum energy of 2.12 MeV, sufficient to penetrate and destroy targeted abnormal tissues. In addition, the low-abundant gamma emission of 155 keV (15%) is efficient for imaging and for dosimetric calculations. These key characteristics identify 188Re as an important therapeutic radioisotope for routine clinical use. Moreover, the highly reproducible on-demand availability of 188Re from the 188W/188Re generator system is an important feature and permits installation in hospital-based or central radiopharmacies for cost-effective availability of no-carrier-added (NCA) 188Re. Rhenium-188 and technetium-99 m exhibit similar chemical properties and represent a "theranostic pair." Thus, preparation and targeting of 188Re agents for therapy is similar to imaging agents prepared with 99mTc, the most commonly used diagnostic radionuclide. Over the last three decades, radiopharmaceuticals based on 188Re-labeled small molecules, including peptides, antibodies, Lipiodol and particulates have been reported. The successful application of these 188Re-labeled therapeutic radiopharmaceuticals has been reported in multiple early phase clinical trials for the management of various primary tumors, bone metastasis, rheumatoid arthritis, and endocoronary interventions. This article reviews the use of 188Re-radiopharmaceuticals which have been investigated in patients for cancer treatment, demonstrating that 188Re represents a cost effective alternative for routine clinical use in comparison to more expensive and/or less readily available therapeutic radioisotopes.

Human sodium iodide transporter gene-mediated imaging and therapy of mouse glioma, comparison between 188Re and 131I

Novel treatment options are urgently required for patients with glioma who are not effectively treated through standard therapy. Human sodium iodide symporter (hNIS) is a molecular target of certain tumors types. Compared with ¹³¹I, ¹⁸⁸Re possesses a higher energy and shorter half-life; therefore, the effects of ¹⁸⁸Re and ¹³¹I were compared in hNIS-mediated gene imaging and therapy in the present study. Recombinant human brain glioma cell line U87 was transfected with a recombinant lentiviral vector containing hNIS (U87-hNIS). U87-0 cell line transfected with blank lentivirus was prepared as a control. In vitro, the ¹⁸⁸Re and ¹³¹I uptake of U87-hNIS cells were 21.3-times and 25.9-times that of the control groups, however the excretion rate of the two nuclides was very rapid, and the half-life was only ~4 min. Sodium perchlorate inhibited hNIS-mediated ¹⁸⁸Re and ¹³¹I uptake to levels observed in the control groups. ¹⁸⁸Re and ¹³¹I were able to kill U87-hNIS cells selectively, with a survival of only 21.6 and 36.2%, respectively. U87-hNIS nude mice appeared to accumulate ¹⁸⁸Re, with a ratio of radioactivity counts between tumor and non-tumor sites of ~13.5 compared with 10.3 of ¹³¹I 1 h after radionuclide injection. In contrast with in vitro studies, U87-hNIS cells demonstrated a notable increase in ¹⁸⁸Re retention in vivo, even 24 h after ¹⁸⁸Re injection. U87-hNIS cells also exhibited increased ¹³¹I retention in vivo; however, as the time increased, ¹³¹I was rapidly released with the tumor no longer able to be imaged 24 h after ¹³¹I injection. Following treatment, U87-hNIS tumors experienced a volume reduction of 24.1%, whereas U87-0 cells demonstrated an increase of 28.8%. ¹⁸⁸Re and ¹³¹I were revealed to be effective at decreasing tumor volume compared with the control. However, ¹⁸⁸Re was significantly more potent compared with ¹³¹I (P<0.01). The present study indicated that the U87-hNIS cell line is sufficient to induce specific ¹⁸⁸Re and ¹³¹I uptake, which may kill cells in vitro and in vivo. ¹⁸⁸Re exhibited an increased retention time in vivo compared with ¹³¹I, which facilitates the imaging and therapy of U87-hNIS tumors.

The Na+/I- symporter (NIS): mechanism and medical impact

The Na(+)/I(-) symporter (NIS) is the plasma membrane glycoprotein that mediates active I(-) transport in the thyroid and other tissues, such as salivary glands, stomach, lactating breast, and small intestine. In the thyroid, NIS-mediated I(-) uptake plays a key role as the first step in the biosynthesis of the thyroid hormones, of which iodine is an essential constituent. These hormones are crucial for the development of the central nervous system and the lungs in the fetus and the newborn and for intermediary metabolism at all ages. Since the cloning of NIS in 1996, NIS research has become a major field of inquiry, with considerable impact on many basic and translational areas. In this article, we review the most recent findings on NIS, I(-) homeostasis, and related topics and place them in historical context. Among many other issues, we discuss the current outlook on iodide deficiency disorders, the present stage of understanding of the structure/function properties of NIS, information gleaned from the characterization of I(-) transport deficiency-causing NIS mutations, insights derived from the newly reported crystal structures of prokaryotic transporters and 3-dimensional homology modeling, and the novel discovery that NIS transports different substrates with different stoichiometries. A review of NIS regulatory mechanisms is provided, including a newly discovered one involving a K(+) channel that is required for NIS function in the thyroid. We also cover current and potential clinical applications of NIS, such as its central role in the treatment of thyroid cancer, its promising use as a reporter gene in imaging and diagnostic procedures, and the latest studies on NIS gene transfer aimed at extending radioiodide treatment to extrathyroidal cancers, including those involving specially engineered NIS molecules.

Stromal targeting of sodium iodide symporter using mesenchymal stem cells allows enhanced imaging and therapy of hepatocellular carcinoma

The tumor-homing property of mesenchymal stem cells (MSC) has lead to their use as delivery vehicles for therapeutic genes. The application of the sodium iodide symporter (NIS) as therapy gene allows noninvasive imaging of functional transgene expression by (123)I-scintigraphy or PET-imaging, as well as therapeutic application of (131)I or (188)Re. Based on the critical role of the chemokine RANTES (regulated on activation, normal T-cell expressed and presumably secreted)/CCL5 secreted by MSCs in the course of tumor stroma recruitment, use of the RANTES/CCL5 promoter should allow tumor stroma-targeted expression of NIS after MSC-mediated delivery. Using a human hepatocellular cancer (HCC) xenograft mouse model (Huh7), we investigated distribution and tumor recruitment of RANTES-NIS-engineered MSCs after systemic injection by gamma camera imaging. (123)I-scintigraphy revealed active MSC recruitment and CCL5 promoter activation in the tumor stroma of Huh7 xenografts (6.5% ID/g (123)I, biological half-life: 3.7 hr, tumor-absorbed dose: 44.3 mGy/MBq). In comparison, 7% ID/g (188)Re was accumulated in tumors with a biological half-life of 4.1 hr (tumor-absorbed dose: 128.7 mGy/MBq). Administration of a therapeutic dose of (131)I or (188)Re (55.5 MBq) in RANTES-NIS-MSC-treated mice resulted in a significant delay in tumor growth and improved survival without significant differences between (131)I and (188)Re. These data demonstrate successful stromal targeting of NIS in HCC tumors by selective recruitment of NIS-expressing MSCs and by use of the RANTES/CCL5 promoter. The resulting tumor-selective radionuclide accumulation was high enough for a therapeutic effect of (131)I and (188)Re opening the exciting prospect of NIS-mediated radionuclide therapy of metastatic cancer using genetically engineered MSCs as gene delivery vehicles.

Sodium iodide symporter (NIS)-mediated radionuclide ((131)I, (188)Re) therapy of liver cancer after transcriptionally targeted intratumoral in vivo NIS gene delivery

We reported the therapeutic efficacy of (131)I in hepatocellular carcinoma (HCC) cells stably expressing the sodium iodide symporter (NIS) under the control of the tumor-specific α-fetoprotein (AFP) promoter. In the current study we investigated the efficacy of adenovirus-mediated in vivo NIS gene transfer followed by (131)I and (188)Re administration for the treatment of HCC xenografts. We used a replication-deficient adenovirus carrying the human NIS gene linked to the mouse AFP promoter (Ad5-AFP-NIS) for in vitro and in vivo NIS gene transfer. Functional NIS expression was confirmed by in vivo γ-camera imaging, followed by analysis of NIS protein and mRNA expression. Human HCC (HepG2) cells infected with Ad5-AFP-NIS concentrated 50% of the applied activity of (125)I, which was sufficiently high for a therapeutic effect in an in vitro clonogenic assay. Four days after intratumoral injection of Ad5-AFP-NIS (3×10(9) plaque-forming units) HepG2 xenografts accumulated 14.5% injected dose (ID)/g (123)I with an effective half-life of 13 hr (tumor-absorbed dose, 318 mGy/MBq (131)I). In comparison, 9.2% ID/g (188)Re was accumulated in tumors with an effective half-life of 12.8 hr (tumor-absorbed dose, 545 mGy/MBq). After adenovirus-mediated NIS gene transfer in HepG2 xenografts administration of a therapeutic dose of (131)I or (188)Re (55.5 MBq) resulted in a significant delay in tumor growth and improved survival without a significant difference between (188)Re and (131)I. In conclusion, a therapeutic effect of (131)I and (188)Re was demonstrated in HepG2 xenografts after tumor-specific adenovirus-mediated in vivo NIS gene transfer.

Evaluation of [18F]-tetrafluoroborate as a potential PET imaging agent for the human sodium/iodide symporter in a new colon carcinoma cell line, HCT116, expressing hNIS

PURPOSE

Accumulation of iodide and other substrates via the human sodium/iodide symporter (hNIS) is fundamental to imaging and therapy of thyroid disease, hNIS reporter gene imaging and hNIS-mediated gene therapy. There is no readily available positron emission tomography (PET) tracer for hNIS. Our aim was to develop a colon carcinoma cell line stably expressing hNIS, and use it to evaluate a novel hNIS PET tracer, [18F]-tetrafluoroborate.

METHODS

Colon carcinoma cell line, HCT116, was stably transfected with hNIS, thus producing a cell line, HCT116-C19, with high hNIS expression. A Fisher rat thyroid cell line, FRTL5, which expresses rat sodium/iodide symporter when stimulated with thyroid-stimulating hormone, was used for comparison. Accumulation of [188Re]-perrhenate, [99mTc]-pertechnetate and [18F]-tetrafluoroborate was evaluated with and without perchlorate inhibition using an automated radioimmune assay system, LigandTracer. The affinity of [18F]-tetrafluoroborate for hNIS, and its half-maximal inhibitory concentration (IC50) for the inhibition of [99mTc]-pertechnetate transport were determined from the plateau accumulation of [18F]-tetrafluoroborate and [99mTc]-pertechnetate, respectively, as a function of tetrafluoroborate concentration.

RESULTS

[18F]-tetrafluoroborate accumulated effectively in both FRTL5 and HCT116-C19 cells. The accumulation in HCT116-C19 cells (plateau accumulation 31%) was comparable to that of [188Re]-perrhenate (41%) and [99mTc]-pertechnetate (46%). Its affinity for hNIS and half-maximal inhibitory concentration (IC50) for the inhibition of pertechnetate uptake was approximately micromolar.

CONCLUSION

We have produced a human colon cell line with a stable constitutive expression of functional hNIS (HCT116-hNIS-C19). [18F]-tetrafluoroborate accumulates in cells expressing hNIS or rat sodium/iodide symporter and is a potential PET imaging agent in thyroid disease and hNIS reporter gene imaging.

The biology of the sodium iodide symporter and its potential for targeted gene delivery

The sodium iodide symporter (NIS) is responsible for thyroidal, salivary, gastric, intestinal and mammary iodide uptake. It was first cloned from the rat in 1996 and shortly thereafter from human and mouse tissue. In the intervening years, we have learned a great deal about the biology of NIS. Detailed knowledge of its genomic structure, transcriptional and post-transcriptional regulation and pharmacological modulation has underpinned the selection of NIS as an exciting approach for targeted gene delivery. A number of in vitro and in vivo studies have demonstrated the potential of using NIS gene therapy as a means of delivering highly conformal radiation doses selectively to tumours. This strategy is particularly attractive because it can be used with both diagnostic (99mTc, 125I, 124I)) and therapeutic (131I, 186Re, 188Re, 211At) radioisotopes and it lends itself to incorporation with standard treatment modalities, such as radiotherapy or chemoradiotherapy. In this article, we review the biology of NIS and discuss its development for gene therapy.

Synthesis and biological evaluation of [(18)F]tetrafluoroborate: a PET imaging agent for thyroid disease and reporter gene imaging of the sodium/iodide symporter

Purpose

The human sodium/iodide symporter (hNIS) is a well-established target in thyroid disease and reporter gene imaging using gamma emitters ¹²³I-iodide, ¹³¹I-iodide and ^99mTc-pertechnetate. However, no PET imaging agent is routinely available. The aim of this study was to prepare and evaluate ¹⁸F-labelled tetrafluoroborate ([¹⁸F]TFB) for PET imaging of hNIS.

Methods

[¹⁸F]TFB was prepared by isotopic exchange of BF₄⁻ with [¹⁸F]fluoride in hot hydrochloric acid and purified using an alumina column. Its identity, purity and stability in serum were determined by HPLC, thin-layer chromatography (TLC) and mass spectrometry. Its interaction with NIS was assessed in vitro using FRTL-5 rat thyroid cells, with and without stimulation by thyroid-stimulating hormone (TSH), in the presence and absence of perchlorate. Biodistribution and PET imaging studies were performed using BALB/c mice, with and without perchlorate inhibition.

Results

[¹⁸F]TFB was readily prepared with specific activity of 10 GBq/mg. It showed rapid accumulation in FRTL-5 cells that was stimulated by TSH and inhibited by perchlorate, and rapid specific accumulation in vivo in thyroid (SUV = 72 after 1 h) and stomach that was inhibited 95% by perchlorate.

Conclusion

[¹⁸F]TFB is an easily prepared PET imaging agent for rodent NIS and should be evaluated for hNIS PET imaging in humans.

Electronic supplementary material

The online version of this article (doi:10.1007/s00259-010-1523-0) contains supplementary material, which is available to authorized users.

Prolonged cardiac allograft survival using iodine 131 after human sodium iodide symporter gene transfer in a rat model

BACKGROUND

Radioiodine is efficiently concentrated by tissues expressing the human sodium iodide symporter (hNIS).

OBJECTIVE

To analyze the effects of iodine 131 on acute cardiac allograft rejection after ex vivo hNIS gene transfer in a rat model of cardiac allotransplantation.

MATERIALS AND METHODS

Hearts from Brown Norway rats were perfused ex vivo either with UW (University of Wisconsin) solution (n = 9) or UW solution containing 1 x 10(9) pfu/mL of adenovirus 5 plus NIS (Ad-NIS) (n = 18). Donor hearts were transplanted heterotopically into the abdomen of Lewis rats, and recipients were treated on postoperative day 3 with either 15,000 microCi of (131)I or saline solution. The hearts were explanted when no longer beating, and were evaluated histologically for evidence of rejection and other changes.

RESULTS

Grafts perfused with the Ad-NIS vector survived significantly longer in recipients injected with (131)I (mean [SD], 11.3 [1.9] days) compared with control animals not treated with (131)I (5.7 [0.65] days) (P < .001). Treatment with (131)I did not prolong graft survival in recipients of hearts that were not perfused with Ad-NIS (5.5 [1.0] vs 5.3 [0.8] days). In Ad-NIS (131)I-treated transplants, the level of myocardial damage on day 6 after surgery, when control hearts were rejected, was significantly lower (60.8 [28.0] vs 99.7 [0.8]; P < .05).

CONCLUSION

Our findings indicate that (131)I, after NIS gene transfer, can effectively prolong cardiac allograft survival. To our knowledge, this is the first report of the use of NIS-targeted (131)I therapy in cardiac transplantation. Further studies are required to determine the mechanism of this effect and its potential for clinical application.

Combined radionuclide-chemotherapy and in vivo imaging of hepatocellular carcinoma cells after transfection of a triple-gene construct, NIS, HSV1-sr39tk, and EGFP

The sodium iodine symporter (NIS) or mutant Herpes-simplex virus type1 sr39 thymidine kinase (HSV1-sr39tk) gene is used for in vivo imaging and cancer therapy. Transfection of both NIS and HSV1-sr39tk genes to hepatocellular carcinoma cells (Huh-7/NTG) could enhance intracellular accumulation of therapeutic radionuclides and guanosine nucleoside analogue prodrugs to produce better outcomes than single gene therapy. Non-invasive imaging with I-124, F-18 FHBG and combination therapy with I-131 and GCV were performed in hepatocellular carcinoma cells transfected with NIS, HSV1-sr39tk and GFP. Our results show that: (1) all three genes are stably expressed in Huh-7/NTG cells, (2) I-125 and H3-PCV uptake were markedly increased in the Huh-7/NTG cells in vitro, (3) cellular survival and tumor growth of Huh-7/NTG was inhibited by I-131 or GCV both in vitro and in vivo, and was much prominent with combination therapy, (4) in vivo imaging with I-124 and F-18 FHBG revealed increased uptake in the Huh-7/NTG tumor. Our results demonstrated the potential of combination gene therapy using NIS and HSV1-sr39tk followed by radioiodine treatment and chemotherapy in human hepatocellular carcinoma cells.

Pharmacokinetics and dosimetry of 188 Re-pharmaceuticals

The main objective of this review is to apportion current and new insight into the biodistribution, radiopharmacokinetics, dosimetry and cell targeting of rhenium-188 labeled radiopharmaceuticals used as therapeutic drugs. The emphasis lies on the generator obtained rhenium-188, its physical, therapeutic, dosimetric and coordinated compounds. Its use in radioimmunotherapy for lymphoma and other hematological diseases with monoclonal antibodies is discussed. Radiolabeled peptides to target cell receptors are an important field in nuclear medicine and in some research facilities are already being used, especially, somatostatin, bombesin and other peptides. Small molecules labeled with 188 Re are promising as therapeutic drugs. A review about some of the non-specific targeting molecules with therapeutic or pain palliation effect such as phosphonates, lipiodol, microparticles and other interesting molecules is included. Research on the labeling of biomolecules with the versatile rhenium-188 has contributed to the development of therapeutics with favorable pharmacokinetic and dosimetric properties for cancer treatment.

The importance of sodium/iodide symporter (NIS) for thyroid cancer management

The thyroid gland has the ability to uptake and concentrate iodide, which is a fundamental step in thyroid hormone biosynthesis. Radioiodine has been used as a diagnostic and therapeutic tool for several years. However, the studies related to the mechanisms of iodide transport were only possible after the cloning of the gene that encodes the sodium/iodide symporter (NIS). The studies about the regulation of NIS expression and the possibility of gene therapy with the aim of transferring NIS gene to cells that normally do not express the symporter have also become possible. In the majority of hypofunctioning thyroid nodules, both benign and malignant, NIS gene expression is maintained, but NIS protein is retained in the intracellular compartment. The expression of NIS in non-thyroid tumoral cells in vivo has been possible through the transfer of NIS gene under the control of tissue-specific promoters. Apart from its therapeutic use, NIS has also been used for the localization of metastases by scintigraphy or PET-scan with 124I. In conclusion, NIS gene cloning led to an important development in the field of thyroid pathophysiology, and has also been fundamental to extend the use of radioiodine for the management of non-thyroid tumors.

Targeting sodium/iodide symporter gene expression for estrogen-regulated imaging and therapy in breast cancer

Expression of the sodium iodide symporter (hNIS) has been detected in breast cancer tissue, but frequently, not at the levels necessary to mediate (131)I accumulation. Transducing the hNIS gene into breast cancer cells with adenovirus could be a tractable strategy to render breast cancer susceptible to radioiodide therapy. We constructed the replication-incompetent virus, AdSERE, in which an estrogen-responsive promoter directs the expression of hNIS. In vitro, we demonstrate that AdSERE mediates hNIS expression and iodide uptake in ER+ breast cancer cells. In vivo, we show that AdSERE-infected ER+ tumors can be imaged due to tracer accumulation; in addition, AdSERE in combination with therapeutic doses of (131)I suppresses tumor growth.

Image-guided radioiodide therapy of medullary thyroid cancer after carcinoembryonic antigen promoter-targeted sodium iodide symporter gene expression

In contrast to follicular cell-derived thyroid cancer, medullary thyroid cancer (MTC) remains difficult to treat because of its unresponsiveness to radioiodine therapy, or to conventional chemo- and radiotherapy. We therefore examined the feasibility of radioiodine therapy of MTC after human sodium iodide symporter (hNIS) gene transfer, using the tumor-specific carcinoembryonic antigen (CEA) promoter for transcriptional targeting. NIS gene transfer was performed in vivo in human MTC cell (TT) xenografts, using adenoviral vectors carrying the NIS gene linked to the cytomegalovirus promoter (Ad5-CMV-NIS) or a CEA promoter fragment (Ad5-CEA-NIS). Functional NIS expression was confirmed by immunostaining as well as in vivo (123)I gamma-camera imaging followed by application of a therapeutic (131)I dose. TT cell xenografts in nude mice injected intratumorally with Ad5-CEA-NIS accumulated 7.5 +/- 1.2% ID/g (percentage injected dose per gram tumor tissue; 5 x 10(8) PFU) and 12 +/- 2.95% ID/g (1 x 10(9) PFU) with an average biological half-life of 6.1 +/- 0.8 and 23.6 +/- 3.7 hr, respectively, as compared with accumulation of 8.4 +/- 0.9% ID/g with a biological half-life of 12 +/- 8 hr after application of Ad5-CMV-NIS (5 x 10(8) PFU). After Ad5-CEA-NIS-mediated NIS gene transfer in TT cell xenografts administration of a therapeutic dose of 111 MBq (3 mCi) of (131)I resulted in a significant reduction of tumor growth associated with significantly lower calcitonin serum levels in treated mice as well as improved survival. We conclude that a therapeutic effect of (131)I was demonstrated in vivo in MTC cell xenografts after adenovirus-mediated induction of tumor-specific iodide accumulation by CEA promoter-directed hNIS expression.

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.

Functional sodium iodide symporter expression in breast cancer xenografts in vivo after systemic treatment with retinoic acid and dexamethasone

CONTEXT

The sodium iodide symporter (NIS) mediates iodide uptake in the thyroid gland as well as in lactating breast, and is also expressed in the majority of breast cancers. Recently, we have reported stimulation of all-trans retinoic acid (atRA)-induced NIS expression in the human breast cancer cell line MCF-7 by dexamethasone (Dex), resulting in an enhanced therapeutic effect of (131)I in vitro.

OBJECTIVE

In the current study we examined the efficacy of Dex stimulation of atRA-induced NIS expression in vivo in MCF-7 xenotransplants in nude mice.

DESIGN

After systemic treatment with atRA alone or in combination with Dex, iodide accumulation in the tumors was assessed by gamma camera imaging and gamma counter analysis. In addition, NIS expression was examined on RNA and protein level by RT-PCR and immunohistochemistry, respectively.

RESULTS

Using gamma camera imaging after intraperitoneal injection of 18.5 MBq (123)I, no iodide accumulation was detected in tumors of untreated mice or mice treated with atRA only. After combined treatment with atRA/Dex significant (123)I accumulation was detected in MCF-7 xenografts, which, by ex vivo gamma counting revealed a 3.3-fold increase in iodide accumulation as compared to control tumors. Surprisingly, in a subset of mice treated with atRA or atRA/Dex iodide accumulation was also detected in the normal mammary glands. In a normal human mammary epithelial cell line HB-2, however, no functional NIS expression was induced after treatment with atRA and/or Dex in vitro. Further, NIS mRNA and protein expression was detected in atRA/Dex treated MCF-7 tumors by RT-PCR and immunohistochemistry, respectively.

CONCLUSION

Treatment with Dex in the presence of atRA is able to induce significant amounts of iodide accumulation in breast cancer xenotransplants in vivo due to stimulation of functional NIS protein expression, which opens exciting perspectives for a possible diagnostic and therapeutic role of radioiodine in the treatment of breast cancer.