Estrogen Receptor Imaging Research Articles

Synthesis of new carbon-11 labeled cyclofenil derivatives for PET imaging of breast cancer estrogen receptors

Carbon-11 labeled cyclofenil derivatives, [ 11C]methyl-2-{4-[bis(4-hydroxyphenyl)methylene]cyclohexyl}acetate ([ 11C] 16a), [ 11C]methyl-4-[bis(4-hydroxyphenyl)methylene]cyclohexanecarboxylate ([ 11C] 16b), [ 11C]methyl-2-{3-[bis(4-hydroxyphenyl)methylene]cyclohexyl}acetate ([ 11C] 18a), and [ 11C]methyl-3-[bis(4-hydroxyphenyl)methylene]cyclohexanecarboxylate ([ 11C] 18b), have been synthesized as new potential PET agents for imaging breast cancer estrogen receptors. The target tracers were prepared by O-[ 11C]methylation of their corresponding precursors using [ 11C]CH 3OTf and isolated by a simplified SPE purification procedure in 35–50% radiochemical yields decay corrected to EOB, 15–20 min overall synthesis time, and 74–111 GBq/μmol specific activity at EOS.

Functional Imaging of Estrogen Receptors with Radiolabeled-GAP-EDL in Rabbit Endometriosis Model

Endometriosis is a common women's health problem. Animal models provide an invaluable tool to study the natural history of endometriosis. We previously have reported that (99m)Tc-labeled glutamate peptide-estradiol ((99m)Tc-GAP-EDL) is a useful agent for imaging functional estrogen receptor (ER) via an ER-mediated process. This study was to evaluate the feasibility of using radiolabeled GAP-EDL to image ER-positive (ER +) endometriosis in nonprimate animal models. 3-Aminoethyl estradiol (EDL) was conjugated to glutamate peptide (GAP) to yield GAP-EDL. In vitro cellular uptake studies of (99m)Tc and (68)Ga-GAP-EDL inhibition with cold estrone were conducted in 13,762 rat mammary tumor cells. To create a rabbit model with endometriosis, part of uterine tissue was dissected and grafted in the peritoneal wall. Eight weeks after surgery, scintigraphic images were obtained after intravenous injection of (99m)Tc-GAP-EDL (1 mCi/rabbit, intravenous) at 0.5-2.0 hours, and (68)Ga-GAP-EDL at 45 minutes. We also performed (68)Ga-GAP-EDL blocking study in rabbit model by using tamoxifen. The rabbits were sacrificed and the grafts were excised for histologic examination. In vitro uptake study of (99m)Tc- and (68)Ga-GAP-EDL in 13,762 rat breast cancer cells showed gradually increasing uptake of both tracers. Accumulation of (68)Ga-GAP-EDL in 13,762 cells was inhibited with cold estrone in a dose-dependent manner. In the endometriosis model, the grafted uterine tissue could be visualized by (99m)Tc-GAP-EDL. Necropsy was performed at 2.5 hours after injection time. Four follicular endometrial lesions in eight implanted endometrial tissues were detected, and all lesions could be detected by (99m)Tc-GAP-EDL. Planar scintigraphy of uterus, ovary and implants of necropsy specimen revealed an increased uptake of (99m)Tc-GAP-EDL in comparison with surrounding abdominal wall tissue. Microscopic examinations support that (99m)Tc-GAP-EDL was accumulated in the microinvasive endometrial tissue. After blocking with tamoxifen, (68)Ga-GAP-EDL accumulation in the endometrial grafts could not be visualized, and endometrial tissue-to-normal tissue count ratios were statistically higher in a nonblocked image than that in the blocked image. Endometriosis uptake of radiolabeled GAP-EDL was via an estrogen receptor-mediated process. Radiolabeled-GAP-EDLs are useful agents for imaging endometriosis.

Targeted functional imaging of estrogen receptors with 99mTc-GAP-EDL

To evaluate the feasibility of using (99m)Tc-glutamate peptide-estradiol in functional imaging of estrogen receptor-positive [ER(+)] diseases. 3-Aminoethyl estradiol (EDL) was conjugated to glutamate peptide (GAP) to yield GAP-EDL. Cellular uptake studies of (99m)Tc-GAP-EDL were conducted in ER(+) cell lines (MCF-7, 13762 and T47D). To demonstrate whether GAP-EDL increases MAP kinase activation, Western blot analysis of GAP-EDL was performed in 13762 cells. Biodistribution was conducted in nine rats with 13762 breast tumors at 0.5-4 h. Each rat was administered (99m)Tc-GAP-EDL. Two animal models (rats and rabbits) were created to ascertain whether tumor uptake of (99m)Tc-GAP-EDL was via an ER-mediated process. In the tumor model, breast tumor-bearing rats were pretreated with diethylstilbestrol (DES) 1 h prior to receiving (99m)Tc-GAP-EDL. In the endometriosis model, part of the rabbit uterine tissue was dissected and grafted to the peritoneal wall. The rabbit was administered with (99m)Tc-GAP-EDL. There was a 10-40% reduction in uptake of (99m)Tc-GAP-EDL in cells treated with DES or tamoxifen compared with untreated cells. Western blot analysis showed an ERK1/2 phosphorylation process with GAP-EDL. Biodistribution studies showed that tumor uptake and tumor-to-muscle count density ratio in (99m)Tc-GAP-EDL groups were significantly higher than those in (99m)Tc-GAP groups at 4 h. Among (99m)Tc-GAP-EDL groups, region of interest analysis of images showed that tumor-to muscle ratios were decreased in blocking groups. In the endometriosis model, the grafted uterine tissue could be visualized by (99m)Tc-GAP-EDL. Cellular or tumor uptake of (99m)Tc-GAP-EDL occurs via an ER-mediated process. (99m)Tc-GAP-EDL is a useful agent for imaging functional ER(+) disease.

Design and Synthesis of Functionalized Cyclopentadienyl Tricarbonylmetal Complexes for Technetium-94m PET Imaging of Estrogen Receptors

Cyclopentadienyl tricarbonylmetal (CpTM, M = Re, (94m)Tc) complexes, some based on a typical nonsteroidal estrogen, were prepared with the aim of developing technetium- and rhenium-labeled imaging agents for estrogen receptor (ER) positive breast tumors. CpT[(94m)Tc] compounds with simple cyclopentadienyl substituents were first synthesized using a modified double ligand transfer reaction. The in vivo biodistribution of one of these CpT[(94m)Tc] complexes was determined by tissue dissection and microPET imaging. Novel C-ring substituted analogues of cyclofenil, a nonsteroidal compound known to bind the ER, were also prepared, and their ER binding was measured. Because of their low ER affinity, however, labeling and imaging studies of these compounds were not pursued. It is notable that the highest ER binding analogue, a CpTRe cyclofenil derivative, could be synthesized from the corresponding ferrocenyl cyclofenil analogue by the double ligand transfer reaction. This further demonstrates the versatility of the double ligand transfer reaction and indicates that the synthesis of technetium and rhenium radiolabeled agents for breast tumor imaging and therapy is also likely to be successful.

7α- and 17α-Substituted estrogens containing tridentate tricarbonyl rhenium/Technetium complexes: synthesis of estrogen receptor imaging agents and evaluation using microPET with technetium-94m

To develop technetium and rhenium-labeled imaging agents for estrogen receptor (ER) positive breast tumors, we have prepared tridentate metal tricarbonyl chelates substituted at the 7α- and 17α-positions of estradiol. Some of the Re(CO)3 conjugates have high binding for the ER in vitro. The in vivo biodistribution of the highest affinity of these novel metal tricarbonyl conjugates, prepared as the 94mTc labeled analogue, was evaluated by tissue dissection and microPET imaging. Although target tissue-selective uptake was not apparent, it is notable that microPET imaging identified the stomach as a major site of activity deposition, a site that might have been missed by standard tissue distribution studies.

Imaging of Estrogen Receptors with Iodine-123- Iabeled Estradiol in Primary Breast Cancer Patients

Purpose: We evaluated the feasibility of non-invasive imaging of estrogen receptors (ER) in primary breast cancer with iodine-123-labeled ER specific ligand (17 , 20E)-21-[$^123$I] iodo-19-nonpregna-1,3,5-(10), 20-tetraene-3, 17-diol using conventional nuclear medicine technique. Methods: Before they underwent surgical management, planar scintigraphy and single-photon emission computed tomography (SPECT) were performed in 18 patients with proven primary breast cancer, after single IV injection of 510 mCi I-123-estradiol. The results were compared with those of immunohistochemical staining against ER of the surgical specimens. Results: Planar and SPECT imaging showed hot uptake in nine of eighteen (50%) breast cancer patients. The results of ER immunohistochemistry were all positive in these patients. In the 9 cases of negative scintigraphy, 8 showed negative staining results but one showed positive staining results. Therefore, the overall concordance rate of ER scintigraphy and ER immunohistochemistry was 94.4% (17/18). Conclusion: ER scintigraphy using 1-123-estradiol is a highly predictable in vivo technique to detect ER-positive breast cancer preoperatively. It has potential application as a reliable diagnostic modality and indicator of hormone therapy for breast cancer patients.

Synthesis of 2, 16α‐ and 4, 16α‐[16α‐18F]difluoroestradiols and their 11β‐methoxy derivatives for estrogen receptor imaging

AbstractWe have prepared the 2‐ and 4‐fluoro derivatives of 16α‐[18F]fluoroestradiol (FES) (4a, b) and 11β‐OMe‐FES (4c, d). Electrophilic substitution of estrone or 11β‐OMe‐estrone with N‐fluoropyridinium salt gave the 2‐and 4‐F derivatives 1, which were converted to the triols 2 and subsequently to the reactive 16β, 17β‐cyclic sulfates 3. Stereoselective opening of the cyclic sulfates via nucleophilic fluorination with Me4NF or [18F]F‐ and removal of the protecting ether and sulfate groups via rapid acid hydrolysis gave 4a‐d or [16α‐18F]‐(4a‐d).

(17α,20 E/Z)-iodovinyl- and 16α-iodo-18-homoestradiol derivatives: synthesis and evaluation for estrogen receptor imaging

Three new 125I-radioiodinated estrogens featuring a 13β-ethyl instead of the natural 13-methyl group, i.e. 18-homoestradiols, were synthesized and evaluated as potential estrogen receptor imaging agents. The 16α-iodo-18-methylestradiol and the 125I-labeled analog were synthesized from the corresponding 16β-bromo analog by the halogen-exchange method. The cis-bromohydrin precursor was obtained by bromination of an estrone enolacetate, followed by epimerization and reduction. The isomeric (17α,20 E/Z)-iodovinyl-18-methylestradiols were prepared via the vinyltin intermediates. Treatment of 18-methyl-17α-ethynylestradiol with tri- n-butyltin hydride, in the presence of azobis isobutyronitrile as catalyst and heating at 90–100°C afforded the (17α,20 E)-tri- n-butylstannyl isomer as the major product. Changing the catalyst for triethyl borane, at room temperature, mainly gave the 20 Z-isomer. The nca 125I-labeled analogs were obtained from their corresponding tin intermediates upon treatment with [ 125I]NaI in the presence of H 2O 2. The 16α-[ 125I]iodo- and isomeric (17α,20 E/Z)-[ 125I]iodovinyl-18-methylestradiols were evaluated for estrogen receptor-mediated uterine uptake in immature female rats. Homologation of the C13-methyl group did improve the uterine uptake of the iodovinyl derivatives, but also increased blood retention, resulting in lower target uptake ratios. In the case of the 16α-iodo analog uterine retention decreased upon C13-homologation.

Synthesis, Estrogen Receptor Binding, and Tissue Distribution of a New Iodovinylestradiol Derivative (17α,20E)-21-[ 123I]Iodo-11β-Nitrato-19-Norpregna-1,3,5(10),20-Tetraene-3,17-Diol (E-[ 123I]NIVE)

We have synthesized and evaluated E-11β-nitrato-17α-iodovinylestradiol (E-NIVE; E-3c) and its 123I-labelled form, as a new potential radioligand for imaging of estrogen receptor (ER)-positive human breast tumors. E-[ 123I]NIVE was prepared by stereospecific iododestannylation of the E-tri- n-butylstannylvinyl precursor (E-2c), obtained from reaction of 11β-nitrato-estrone (8) with E-tributylstannylvinyllithium. In competitive binding studies, E-NIVE proved to have high binding affinity for both the rat and the human ER (K i 280–730 pM), without significant binding to human sex hormone binding globulin. Distribution studies in normal and mammary tumor-bearing rats showed specific ER-mediated uptake of E-[ 123I]NIVE in the estrogen target tissues, i.e., uterus, ovaries, pituitary, and hypothalamus, but not in the mammary tumors. Selective retention in these target tissues, including tumor tissue, resulted in significant increases over time for the target tissue-to-muscle uptake ratios, but not for the target tissue-to-fat uptake ratios. The tumor-to-fat uptake ratio even appeared constantly below 1. In the primary estrogen target tissues, E-[ 123I]NIVE displayed high specific ER-mediated uptake and retention, which resulted in moderate target-to-nontarget tissue uptake ratios. In contrast, in tumor tissue, E-[ 123I]NIVE uptake appeared to be rather low and not ER-specific. As a consequence, E-[ 123I]NIVE appears to be a less favorable radioligand for ER imaging in breast cancer than the previously studied stereoisomers of 11β-methoxy-17α-[ 123I]iodovinylestradiol (E- and Z-[ 123I]MIVE; [ 123I]E- and [ 123I]Z-3b).

Imaging of estrogen receptors in primary and metastatic breast cancer patients with iodine-123-labeled Z-MIVE.

To evaluate the feasibility of noninvasive imaging of estrogen receptors (ERs) in primary and metastatic breast cancer with the iodine-123-labeled ER-specific ligand cis-11beta-methoxy-17alpha-iodovinylestradiol-17beta (Z-[123I]MIVE) using conventional nuclear medicine techniques. Z-[123I]MIVE planar scintigraphy and single-photon emission computed tomography (SPECT) were performed in 12 patients with proven primary breast cancer and 13 patients with proven or from other imaging modalities evident bone, liver, lung, pleura and/or lymph node metastases. The results were compared with those of ER immunohistochemistry (IHC). Blocking studies with the antiestrogen tamoxifen were performed to test whether Z-[123I]MIVE tumor uptake was ER-mediated. Planar imaging showed uptake in 11 of 12 primary carcinomas. ER IHC performed for nine of these was positive. For the planar scintigraphy-negative patient, SPECT was faintly positive, but ER IHC negative (agreement, 90%). In nine of 13 metastatic patients, planar scintigraphy was positive. The agreement between the results of ER IHC on the original primary tumor and of Z-[123I]MIVE scintigraphy was 82%. Specificity of tumor Z-[123I]MIVE uptake was established by complete blockade of uptake by tamoxifen, except in two patients who showed progressive disease. Z-[123I]MIVE scintigraphy also enabled discriminating metastases from confounding nonmalignant abnormalities of the bone scan. Z-[123I]MIVE scintigraphy shows high sensitivity and specificity for the detection of ER-positive breast cancer. This may have impact on diagnostic possibilities and therapeutic management. Since ER imaging shows the functional status, addressing known intratumoral and intertumoral ER heterogeneity, it may improve the characterization of disease and the selection of patients who may benefit from hormonal therapy.

The Z-isomer of 11β-methoxy-17α-[ 123I]iodovinylestradiol is a promising radioligand for estrogen receptor imaging in human breast cancer

The potential of both stereoisomers of 11β-methoxy-17α[ 123I]iodovinylestradiol (E- and Z-[ 123I]MIVE) as suitable radioligands for imaging of estrogen receptor(ER)-positive human breast tumours was studied. The 17α-[ 123I]iodovinylestradiol derivatives were prepared stereospecifically by oxidative radioiododestannylation of the corresponding 17α-tri- n-butylstannylvinylestradiol precursors. Both isomers of MIVE showed high in vitro affinity for dimethylbenzanthracene-induced rat and fresh human mammary tumour ER, that of Z-MIVE however being manyfold higher than that of E-MIVE. In vivo distribution studies with E- and Z-[ 123I]MIVE in normal and tumour-bearing female rats showed ER-mediated uptake and retention in uterus, ovaries, pituitary, hypothalamus and mammary tumours, again the highest for Z-[ 123I]MIVE. The uterus- and tumour-to-nontarget tissue (fat, muscle) uptake ratios were also highest for Z-[ 123I]MIVE. Additionally, planar whole body imaging of two breast cancer patients 1–2 h after injection of Z-[ 123I]MIVE showed increased focal uptake at known tumour sites. Therefore, we conclude that Z-[ 123I]MIVE is a promising radioligand for the diagnostic imaging of ER in human breast cancer.

Quantitative imaging of estrogen and progesterone receptors, estrogen-regulated protein, and growth fraction: immunocytochemical assays in 52 meningiomas. Correlation with clinical and morphological data.

Quantitative imaging of estrogen receptors (ER's), progesterone receptors (PR's), estrogen-regulated protein (pS2), and growth fraction (Ki67) immunocytochemical assays were performed in 52 meningiomas. The results were correlated with clinical (age, sex, hormonal status, and tumor volume and location) and morphological (histological types and grades) data. The authors observed a lack of ER's in all meningiomas but the presence of PR's in 53% of these meningiomas. The immunoreactivity was restricted to tumor cell nuclei. The PR immunocytochemical assay was correlated with tumor location, histological type, histological grade, and pS2 immunocytochemical assay, but not with Ki67 immunocytochemical assay; high PR content was observed in cisternae, transitional, meningothelial, and low-grade meningiomas. Only 11 meningiomas showed more than 1% Ki67 immunoreactive nuclei. These meningiomas were usually located in the convexity and were of high histological grade. Estrogen-regulated protein immunoreactivity was observed in 34 meningiomas but the number of immunoreactive nuclei was low. The pS2 immunocytochemical assay was not related to clinicopathological features but was preferentially observed in PR-negative meningiomas. The results of this study are compared with those previously reported, and the function and regulation of PR's in meningiomas is discussed. The results indicate that 1) regulation of PR's and pS2 proteins in meningiomas differs from regulation in estrogen-dependent tissues such as breast or endometrium; 2) interruption of hormonal therapy in women presenting with a meningioma is not absolutely necessary; 3) meningiomas have different biological properties according to their clinicopathological features; and 4) future studies of hormonal clinical trials should be performed on well-defined meningioma subgroups.

Estrogen receptor imaging with 17α-[ 123I]iodovinyl-11β-methoxyestradiol (MIVE 2)—part I. Radiotracer preparation and characterization

It is important to know the estrogen receptor rate in breast carcinoma management. Thus, an in vivo and atraumatic method would be very useful. Different ligands have been proposed for this. We present here the specific synthesis of 20E- and 20Z-17α-iodovinyl-11β-methoxyestradiols and their biological characterization as estrogen receptor ligands. The two isomers were analysed by current chemical methods (NMR) and purified by HPLC. We carried out an in vivo study with 21-day-old Swiss mice to compare properties of the two ligands. The 20E-MIVE 2 showed the best affinity for estrogen receptors, the uterus-to-blood ratio was 15-fold higher for the trans derivative. We enhanced the in vivo and in vitro properties of the 20E-MIVE 2: the affinity constant was determined by Scatchard analysis, K d = 16 × 10 −10M, and biodistributions were performed with unlabelled estradiol pre-injection. We concluded that 20E-MIVE 2 can be used for a feasibility study in patients with breast carcinoma.

Estrogen receptor imaging with 17α-[ 123I]iodovinyl-11β-methoxyestradiol (MIVE 2)—part II. Preliminary results in patients with breast carcinoma

17α-[ 123I]Iodovinyl-11β-methoxyestradiol was injected into 19 women: group 1 ( n = 8), initial evaluation of breast cancer; group 2, ( n = 11) postoperative follow-up including 9 patients with bone metastases. The primary tumor (size: 8–10 mm) was visualized by breast tomoscintigraphy in 2 4 patients of group 1 with high estrogen receptor concentration (162–445 fmol/mg) and was not detectable in 4 patients with low estrogen receptor concentration (6–32 fmol/mg). Axillary lymph node metastases were detected in 1 patient of group 1 and in 1 patient of group 2. In 4 patients of group 2 with previous primary tumor containing estrogen receptors, MIVE 2 uptake in bone metastases was demonstrated. MIVE 2 scintigraphy is an original, specific and non-invasive method for breast cancer estrogen receptor imaging in primary and in metastatic tumors.

Breast cancer: PET imaging of estrogen receptors.

Thirteen patients with primary breast masses were studied with positron emission tomography (PET) and 16 alpha-[fluorine-18]-fluoroestradiol-17 beta. PET images demonstrated uptake of the labeled estrogen analog at sites of primary carcinomas and in several foci of axillary lymph node metastases, as well as in one distant metastatic site. There was excellent correlation between uptake within the primary tumor measured on the PET images and the tumor estrogen-receptor concentration measured in vitro after excision (r = .96). This technique may provide an in vivo method of assessing estrogen receptors in primary and metastatic breast cancers and thus guide management of this disease with antiestrogen chemotherapy.