Evidence that 99mTc-(V)-DMSA uptake is mediated by NaPi cotransporter type III in tumour cell lines

The Role of Inorganic Phosphate Transporters in Highly Proliferative Cells: From Protozoan Parasites to Cancer Cells

In addition to their standard inorganic phosphate (Pi) nutritional function, Pi transporters have additional roles in several cells, including Pi sensing (the so-called transceptor) and a crucial role in Pi metabolism, where they control several phenotypes, such as virulence in pathogens and tumour aggressiveness in cancer cells. Thus, intracellular Pi concentration should be tightly regulated by the fine control of intake and storage in organelles. Pi transporters are classified into two groups: the Pi transporter (PiT) family, also known as the Pi:Na⁺ symporter family; and the Pi:H⁺ symporter (PHS) family. Highly proliferative cells, such as protozoan parasites and cancer cells, rely on aerobic glycolysis to support the rapid generation of biomass, which is equated with the well-known Warburg effect in cancer cells. In protozoan parasite cells, Pi transporters are strongly associated with cell proliferation, possibly through their action as intracellular Pi suppliers for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity. Similarly, the growth rate hypothesis (GRH) proposes that the high Pi demands of tumours when achieving accelerated proliferation are mainly due to increased allocation to P-rich nucleic acids. The purpose of this review was to highlight recent advances in understanding the role of Pi transporters in unicellular eukaryotes and tumorigenic cells, correlating these roles with metabolism in these cells.

Radionuclide imaging of neuroendocrine tumors

Neuroendocrine tumors (NETs) are relatively rare and heterogeneous with a variaty of clinical expression. They derive from the sensory and secretory neuroendocrine cells mainly within the pulmonary and gastrointestinal tract. They comprise less than 2% of all malignancies. On the basis of clinical behavior, histology, and proliferation rate, they are devided into well differentiated (low grade to intermediate grade) and poorly differentiated (high grade) neuroendocrine carcinoma. Tumor stage and grade have the impact on treatment and prognosis. The treatment of choice is surgery. More than 50% of the patients present metastatic disease at the time of diagnosis, thus the systemic treatment should be considered including somatostatin analogs, chemotherapy, targeted therapy, immunotherapy and peptide receptor radionuclide therapy (PRRT). For the diagnosis and follow-up of these tumors, various radiological methods are used (computed tomography, magnetic resonance imaging, ultrasound) as well as endoscopy. Nuclear medicine methods are used in order to exploit their unique properties mainly amine precursor uptake and decarboxylation system characteristics, as well as the expression of somatostatin receptors. These methods enable whole body examination, staging, selection of patient for PRRT and treatment monitoring as well. Imaging can be performed with gamma camera (SPECT, SPECT/CT) or positron emission tomography (PET/ CT). Radiopharmaceuticals used for imaging with gamma camera are usually 99mTc-(V)-DMSA, 99mTc-MIBI, 99mTc-HYNIC TOC, 111In-pentetreotide and 131I-MIBG/123I-MIBG. Positron emitting radiopharmaceuticals has superior spatial resolution and faster imaging, such as 68Ga-DOTA-somatostatin analogues, 18F-FDG (particularly for high-grade tumors), 18F-L-DOPA/11C-L-DOPA and 11C-5-hydroxytryptophan that have demonstrated excellent imaging results. The new targeted agents present a challenge in the evaluation procedure of treatment and, therefore, new imaging techniques and an improvement of currently available techniques are mandatory. In this mini-review, the most frequent methods and radiopharmaceuticals are presented, as well as potential development.

Electronic properties of a PrPC-Cu(ii) complex as a marker of 5-fold Cu(ii) coordination

Human prion protein is a subject of extensive study, related in particular to the molecular basis of neurodegenerative disease development and prevention. This protein has two main domains: the membrane C-terminal, structured domain as well as the unstructured N-terminal domain. While PrPC (23-231) has up to eight Cu(ii) binding sites in the N-terminal domain, it includes a characteristic, conservative octarepeat region PHGGGWGQ, which was studied by means of X-ray absorption near edge spectroscopy. The measurements were conducted at the SuperXAS beamline (SLS, PSI, Villigen). For the initial 1 : 1 protein-to-Cu(ii) ratio, the two main Cu(ii) binding modes were identified using linear combination fitting and ab initio FEFF calculations for X-ray spectra. Their electronic structures indicated that Cu(ii) coordinated by strong π-donors could effectively suppress the pre-edge structure due to the filling of empty Cu(ii) d-states. The suppression was correlated with the charge transfer effect and filling of the virtual electronic Cu(ii) states. What is more, we showed that the 1s → 4p + LMCT (Ligand-to-Metal-Charge-Transfer) multielectron transition relation with the main edge transition could be used as a marker for preliminary comparison of an unknown organic compound to a reference. The presented results permitted a possible explanation of the mechanism of choosing the preferred Cu(ii) modes in PrPC-Cu(ii) coordination processes and of the complex stability from the electronic point of view.

A Molecular View of Pathological Microcalcification in Breast Cancer

Breast microcalcification is a potential diagnostic indicator for non-palpable breast cancers. Microcalcification type I (calcium oxalate) is restricted to benign tissue, whereas type II (calcium hydroxyapatite) occurs both in benign as well as in malignant lesions. Microcalcification is a pathological complication of the mammary gland. Over the past few decades, much attention has been paid to exploit this property, which forms the basis for advances in diagnostic procedures and imaging techniques. The mechanism of its formation is still poorly understood. Hence, in this paper, we have attempted to address the molecular mechanism of microcalcification in breast cancer. The central theme of this communication is "how a subpopulation of heterogeneous breast tumor cells attains an osteoblast-like phenotype, and what activities drive the process of pathophysiological microcalcification, especially at the invasive or infiltrating front of breast tumors". The role of bone morphogenetic proteins (BMPs) and tumor associated macrophages (TAMs) along with epithelial to mesenchymal transition (EMT) in manipulating this pathological process has been highlighted. Therefore, this review offers a novel insight into the mechanism underlying the development of microcalcification in breast carcinomas.

Dimercaptosuccinic acid: A multifunctional cost effective agent for imaging and therapy

Dimercaptosuccinic acid (DMSA) is an analog of dimercaprol used as metal chelating moiety in variety of conditions. In nuclear medicine itself two types of Tc-99m DMSA complexes are used, trivalent and pentavalent forms. In this review, we have discussed the mechanism of uptake of both complexes as well as diagnostic and therapeutic application in a clinical scenario.

Pentavalent technetium-99m-dimercaptosuccinic acid [Tc-99m (V) DMSA] brain SPECT: does it have a place in predicting survival in patients with glioblastoma multiforme?

Pentavalent technetium-99m dimercaptosuccinic acid (Tc-99m (V) DMSA) is reported as a useful tool for detection of residual or recurrent gliomas. We aimed to investigate the prognostic value of Tc-99m (V) DMSA brain SPECT in patients with glioblastoma multiforme (GBM). 40 patients [21 males and 19 females; mean age 48.6 ± 12.2 years] with GBM were included. Tc-99m (V) DMSA brain SPECT was done after surgery and before onset of radiation therapy or chemotherapy (Baseline study), at 4-6 weeks and at 6 months as a follow-up after therapy. The end point of the study was clinical follow-up for 2 years and/or death. 4-6 weeks after therapy, 40 and 60 % had negative and positive Tc-99m (V) DMSA for viable tumor tissues respectively (P = 0.09). At 6 months follow-up, 62.5 % of (V) DMSA negative patients and 12.5 % of the positive subjects were responders (P = 0.001). The median over-all survival (OS) of all patients was 12.3 month [range 5-24 month]. Patients with positive (V) DMSA had worse survival (8.87 month) compared to the negative ones (16.67 month) (P = 0.0001). Multivariate Cox regression analysis showed that Tc-99m (V) DMSA brain SPECT studies at 4-6 weeks and 6-months follow-up were independent prognostic factors for survival [OR 1.069; 95 % CI 1.417-2.174; P = 0.03 and OR 1.055; 95 % CI 0.821-1.186; P = 0.01 respectively]. Stratification of tumors into risk groups based on prognostic parameters may improve outcome by altering or intensifying treatment methods. Technetium-99m dimercaptosuccinic acid brain SPECT may have an additional prognostic role in patients with GBM which needs further evaluation in larger future series.

Single-photon emission computed tomography tracers in the diagnostics of neuroendocrine tumors

Different imaging strategies have been developed targeting the peculiar features of neuroendocrine tumors (NETs). Metabolic characteristics and receptor expression on the tumor surface have been studied, and expertise and knowledge are increasing as a result of the implementation of fusion imaging and the development of more detailed positron emission tomography tracers. Scintigraphic study of NETs is the most diffused and convenient technique for evaluating patients suspected to have NETs.

Assessment of tracer 99mTc(V)-DMSA uptake as a measure of tumor cell proliferation in vitro

PURPOSE

To examine whether (99m)Tc(V)-DMSA could be used as a non-invasive measure of cancer cell proliferation.

METHODS

Human breast cancer MCF-7, MDA-MB-231 and pII, and prostate cancer PC-3 cell lines were grown to 30, 50 and 100% confluency and pulsed with (99m)Tc(V)-DMSA in media for 60 min at 37°C. DNA synthesis was analysed by quantification of the S phase using flow cytometry, [methyl-(3)H]thymidine incorporation and expression of proliferation markers PCNA and Ki-67 using realtime PCR. One way ANOVA was used to compare groups.

RESULTS

In all cell lines rates of (99m)Tc(V)-DMSA uptake were inversely related to cell density. This was paralleled by similar trends in S phase proportions, [methyl-(3)H]thymidine incorporation and expression of PCNA and Ki-67.

CONCLUSION

Rates of (99m)Tc(V)-DMSA uptake into different types of tumour cells correlate well with cell density that is useful as a non-invasive measure of tumour cellular proliferation in vivo.

Glioma residual or recurrence versus radiation necrosis: accuracy of pentavalent technetium-99m-dimercaptosuccinic acid [Tc-99m (V) DMSA] brain SPECT compared to proton magnetic resonance spectroscopy (1H-MRS): initial results

We compared pentavalent technetium-99m dimercaptosuccinic acid (Tc-99m (V) DMSA) brain single photon emission computed tomography (SPECT) and proton magnetic resonance spectroscopy ((1)H-MRS) for the detection of residual or recurrent gliomas after surgery and radiotherapy. A total of 24 glioma patients, previously operated upon and treated with radiotherapy, were studied. SPECT was acquired 2-3 h post-administration of 555-740 MBq of Tc-99m (V) DMSA. Lesion to normal (L/N) delayed uptake ratio was calculated as: mean counts of tumor ROI (L)/mean counts of normal mirror symmetric ROI (N). (1)H-MRS was performed using a 1.5-T scanner equipped with a spectroscopy package. SPECT and (1)H-MRS results were compared with pathology or follow-up neuroimaging studies. SPECT and (1)H-MRS showed concordant residue or recurrence in 9/24 (37.5%) patients. Both were true negative in 6/24 (25%) patients. SPECT and (1)H-MRS disagreed in 9 recurrences [7/9 (77.8%) and 2/9 (22.2%) were true positive by SPECT and (1)H-MRS, respectively]. Sensitivity of SPECT and (1)H-MRS in detecting recurrence was 88.8 and 61.1% with accuracies of 91.6 and 70.8%, respectively. A positive association between the delayed L/N ratio and tumor grade was found; the higher the grade, the higher is the L/N ratio (r = 0.62, P = 0.001). Tc-99m (V) DMSA brain SPECT is more accurate compared to (1)H-MRS for the detection of tumor residual tissues or recurrence in glioma patients with previous radiotherapy. It allows early and non-invasive differentiation of residual tumor or recurrence from irradiation necrosis.

Increased breast density correlates with the proliferation-seeking radiotracer (99m)Tc(V)-DMSA uptake in florid epithelial hyperplasia and in mixed ductal carcinoma in situ with invasive ductal carcinoma but not in pure invasive ductal carcinoma or in mild epithelial hyperplasia

The purpose of this study was to assess the relationship of mammographic breast density (BD) and cell proliferation/focal adhesion kinase activation-seeking radiotracer technetium 99m pentavalent dimercaptosuccinic acid (99mTc(V)-DMSA) uptake in women with different breast histologies, that is, mild epithelial hyperplasia (MEH), florid epithelial hyperplasia (FEH), mixed ductal carcinoma in situ with invasive ductal carcinoma (DCIS + IDC), and pure IDC. Fifty-five women with histologically confirmed mammary pathologies were submitted preoperatively to mammography and 99mTc(V)-DMSA scintimammography. The percentage and intensity of 99mTc(V)-DMSA uptake and the percentage of BD were calculated by computer-assisted methods and compared (t-test) between the breast pathologies. In breasts with increased BD, FEH and DCIS + IDC were found. On the contrary, pure IDC and MEH were identified in breasts with significantly lower BD values. In breasts with increased 99mTc(V)-DMSA area and intensity of uptake, FEH was the main lesion found compared to all other histologies. Linear regression analysis between BD and 99mTc(V)-DMSA uptake area and intensity revealed significant coefficients of correlation (r  =  .689, p < .001 and r  =  .582, p < .001, respectively). Increased BD correlates with the presence of FEH and mixed DCIS + IDC but not with pure IDC or MEH. Its close relationship to 99mTc(V)-DMSA, which also showed an affinity to FEH, indicates that stromal microenvironment may constitute a specific substrate leading to progression to different subtypes of cancerous lesions originating from different pathways.

Molecular imaging of neuroendocrine tumors

Neuroendocrine tumors (NET) are a heterogeneous group of tumors that arise from neuroendocrine cells. These tumors may arise from various organs, including lung, thymus, thyroid, stomach, duodenum, small bowel, large bowel, appendix, pancreas, adrenal, and skin. Most are well differentiated and have the ability to produce biogenic amines and various hormones. NET usually occur sporadically but they also be associated with various familial syndromes. For the vast majority of NET, surgical resection is the treatment of choice whenever feasible. Localization of NET prior to surgery and for staging and follow-up relies on both anatomic and functional imaging modalities. In fact, the unique secretory characteristics of these tumors lend themselves to imaging by molecular imaging modalities, which can target specific metabolic pathways or receptors. Neuroendocrine cells have a variety of such target receptors and pathways for which radiopharmaceuticals have been developed, including [(123)I/(131)I]-metaiodobenzylguanidine (MIBG), [(111)In]pentetreotide, [(68)Ga] somatostatin analogs, [(18)F] fluorodeoxyglucose (FDG), [(11)C/(18)F] dihydroxyphenylalanine (DOPA), [(11)C] 5-hydroxytryptophan (5-HTP) (99m)Tc pentavalent dimercaptosuccinic acid ([(99m)Tc] (V) DMSA, and [(18)F] fluorodopamine (FDA). Here, we review the molecular imaging approaches for NET using various radiopharmaceuticals.

Assessment of glioma proliferation using imaging modalities

The assessment of glioma proliferation rate is important to predict tumor behavior, response to therapy and prognosis. Various methods, largely involving immunohistological markers in tissue samples, have been proposed to this aim; however, they all require tissue removal through a biopsy or during a surgical procedure. Consequently, non-invasive imaging modalities that could reliably assess the proliferative potential of intracranial space-occupying lesions in vivo would be of obvious significance. In the present study we review the contribution of MRI, positron emission tomography and single-photon emission CT for the assessment of the proliferative potential of gliomas.

Molecular imaging in neuroendocrine tumors: molecular uptake mechanisms and clinical results

Neuroendocrine tumors can originate almost everywhere in the body and consist of a great variety of subtypes. This paper focuses on molecular imaging methods using nuclear medicine techniques in neuroendocrine tumors, coupling molecular uptake mechanisms of radiotracers with clinical results. A non-systematic review is presented on receptor based and metabolic imaging methods. Receptor-based imaging covers the molecular backgrounds of somatostatin, vaso-intestinal peptide (VIP), bombesin and cholecystokinin (CCK) receptors and their link with nuclear imaging. Imaging methods based on specific metabolic properties include meta-iodo-benzylguanide (MIBG) and dimercapto-sulphuric acid (DMSA-V) scintigraphy as well as more modern positron emission tomography (PET)-based methods using radio-labeled analogues of amino acids, glucose, dihydroxyphenylalanine (DOPA), dopamine and tryptophan. Diagnostic sensitivities are presented for each imaging method and for each neuroendocrine tumor subtype. Finally, a Forest plot analysis of diagnostic performance is presented for each tumor type in order to provide a comprehensive overview for clinical use.

Evaluation of Tc-99m (V) DMSA binding to human plasma proteins

As a critical step toward elucidating the mechanism of localization of Tc-99m (V) dimercaptosuccinic acid (DMSA), we investigated its binding and transport in blood in comparison with Ga-67 citrate. The studies were performed in vitro by incubating Tc-99m (V) DMSA with blood (one sample at 4 degrees Celcius and another at 37 degrees Celcius) to assess its binding to plasma proteins using ultrafiltration, dialysis, electrophoresis, gel filtration chromatography and affinity chromatography. A parallel experiment for determining the blood binding of Ga-67 citrate was performed using the same procedures. Using ultrafiltration, dialysis, electrophoresis and gel filtration chromatography, labeled plasma samples showed that protein binding for Tc-99m (V) DMSA was 45-54% at 37 degrees Celcius and 73-80% at 4 degrees Celcius. The figures for Ga-67 citrate were 43-53% at 37 degrees Celcius and 75-81% at 4 degrees Celcius. Electrophoresis showed that Tc-99m (V) DMSA was mostly bound to plasma albumin (36.05 +/- 2.48% at 37 degrees Celcius and 60.04 +/- 1.87% at 4 degrees Celcius), and that the proportion of Ga-67 radioactivity associated with beta-globulin was 34.23 +/- 1.37% at 37 degrees Celcius and 55.71 +/- 3.69% at 4 degrees Celcius. In affinity chromatography experiments, Tc-99m (V) DMSA did not bind to transferrin, unlike Ga-67 citrate. This study demonstrates that, at the radiopharmaceutical tracer level, most Tc-99m (V) DMSA in blood is protein-bound, primarily to albumin, but not to transferrin. In contrast, Ga-67 citrate was bound primarily to transferrin. The knowledge that albumin is the main transport protein of Tc-99m (V) DMSA may contribute to a better understanding of its biodistribution and pharmacokinetics.

Role of 99mTc-(V)DMSA in Detecting Tumor Cell Proliferation

Pentavalent technetium-99m dimercaptosuccinic acid (99mTc-(V)DMSA) is a tumor-seeking agent which was introduced to evaluate, image, and manage many types of cancers. In this review, the beginning of, and the most recent applications of using this agent was appraised. The relation with tumor cell detection and proliferation was reported and several mechanisms of uptake of 99mTc-(V)DMSA in tumor cells are described.

The potential role of Calcitonin Gene-Related Peptide (CGRP) in breast carcinogenesis and its correlation with 99mTc-(V)DMSA scintimammography

OBJECTIVES

Experimental data suggest a role for calcitonin gene-related peptide (CGRP) in normal breast development and angiogenesis. This pilot study correlated CGRP with neoangiogenesis and the uptake of the tumor-seeking, proliferation-imaging radiotracer pentavalent technetium-99m dimercaptosuccinate (99mTc-(V)DMSA) in invasive and preinvesive breast lesions.

METHODS

Among women evaluated preoperatively by 99mTc-(V)DMSA scintimammography, 29 invasive ductal carcinomas (IDCs) were retrospectively studied: 15 isolated (Group I); 14 mixed with preinvasive pathologies (ductal carcinoma in situ [DCIS] and/or epithelial hyperplasia [EH]; Group M). CGRP staining and neoangiogenesis were compared between invasive and DCIS/EH regions and were correlated. 99mTc-(V)DMSA displayed a diffusely increased uptake pattern corresponding to DCIS/EH; its lesion-to-background (L/B) ratio was compared between images acquired at 10 and 60 minutes and its retention ratio (RR) was correlated with CGRP.

RESULTS

Seven of 15 group I and 10 of 14 group M patients (58.6% of the population) were CGRP-positive. CGRP was prevalent in the DCIS/EH component of mixed-lesions (even in the surrounding normal epithelium of nearly half), with declining intensity as advancing from DCIS/EH to high-grade IDC. Similarly, neoangiogenesis was considerably higher in DCIS/EH than in group I pure IDCs. A significant CGRP-neoangiogenesis correlation was verified only in group I. The diffuse 99mTc-(V)DMSA uptake exhibited significant, time-related L/B increase and a RR positively correlating with CGRP.

CONCLUSIONS

CGRP expression and neoangiogenesis are intensified in mixed invasive-preinvasive breast lesions; an underlying relation may exist, requiring further investigation. CGRP also appears associated with 99mTc-(V)DMSA's propensity to depict preinvasive pathologies. This relationship could denote an additional proliferative role for CGRP.

The role of Tc-99m (V) DMSA scintigraphy in the diagnosis and follow-up of lung cancer lesions

OBJECTIVE

To define the role of Tc-99m (V) dimercaptosuccinic acid (DMSA) scanning in the detection of lung cancer (LC) and its metastases, and monitoring the response of LC lesions (LCL) to chemo/radiotherapy (TH).

METHODS

Tc-99m (V) DMSA whole-body scans, planar thorax views, and thorax Single-photon emission computed tomography (SPECT) images were obtained both 30 min (early) and 5 h (late) after Tc-99m (V) DMSA administration in 12 small/nonsmall cell LC patients (11 men, 1 woman; mean age 59 years). Five patients also had bone scans. The same scintigraphic protocol was performed in 7 of 12 patients, 3 weeks after first-line TH. TH response was evaluated visually in all LCL and semiquantitatively in primary tumors (PT) of six patients, by comparing the tumor uptake ratios (TUR) of pre-TH and post-TH Tc-99m (V) DMSA SPECT [TUR = mean counts of region of interests (ROI) in PT/mean counts in contralateral ROI]. In seven patients, a 6-month survival was determined.

RESULTS

Tc-99m (V) DMSA accumulated in 34 LCL (11 PT, 19 bone metastases, 1 suprarenal mass, 1 axillary node, 2 supraclavicular nodes). A total of 11 patients displayed Tc-99m (V) DMSA uptake in LCL and one patient did not show uptake. In six patients, SPECT imaging showed deeply located PT in the lung parenchyma better than planar views. In five patients, both planar and SPECT views revealed peripherally located PT in the lungs. Early scans showed 18 LCL and late scans displayed all the LCL. Nine bone metastases on pre-TH Tc-99m (V) DMSA scans revealed matched areas of increased Tc-99m methylene diphosphonate (MDP) uptake on bone scans; six bone metastases were additionally detected on Tc-99m (V) DMSA scans when compared with bone scans, and four bone metastases on Tc-99m (V) DMSA scans could not be compared with bone scans because bone scan was not performed. In one patient, Tc-99m (V) DMSA scans became positive for bone metastases on post-TH later than the bone scans for some of the bone metastases. Neither planar nor SPECT imaging showed mediastinal lesions defined on thorax CT in nine patients. On TH monitoring, 17 LCL showed diminished Tc-99m (V) DMSA uptake, one disappeared, four were unchanged, three displayed increased uptake, and five new lesions were established. Of the six patients, TUR in PT increased in two (one survived), decreased in one (exitus), was unchanged in two (two exitus) on post-TH scans, and PT totally disappeared in one (survived) patient.

CONCLUSIONS

Tc-99m (V) DMSA scans are useful in detecting LCL, except for those around the blood pool regions, making it a promising modality to monitor TH response. Obtaining a single fifth hour late Tc-99m (V) DMSA scan is appropriate. SPECT should be applied to all patients for the detection of deeply located lesions.

Pentavalent technetium-99m dimercaptosuccinic acid [99m Tc-(V)DMSA] brain scintitomography--a plausible non-invasive depicter of glioblastoma proliferation and therapy response

The biological behavior and prognosis of gliomas depend largely on cellular proliferation, resistance to chemotherapy, and metastatic potential. Proliferative propensity has significant implications on patient management but its assessment requires tissue sampling; the non-invasive estimation of brain tumor proliferation represents therefore a major goal. Pentavalent technetium-99 m dimercapto-succinic acid [99m Tc-(V)DMSA] is a tumor-seeking radiotracer displaying affinity for gliomas; its intracellular accumulation is directly linked to cell proliferation. We performed a tomographic 99m Tc-(V)DMSA brain scan in a 35-year-old male baring a recurrent glioblastoma multiforme, to depict its proliferative disposition. The patient had been diagnosed 14 months earlier and had been submitted to surgery, followed by adjuvant radiotherapy and temozolomide-based chemotherapy. On clinical suspicion of recurrence 5 months later, magnetic resonance imaging (MRI) revealed a lesion at the site of preceded surgery, which was treated by imatinib mesylate. No improvement was ascertained the following months and radiographic assessment verified tumor progression. Scintitomography revealed avid radiotracer uptake in the entirety of the lesion (the distribution of radioactivity closely conforming to the morphological tumor boundaries), an indication that the neoplasm demonstrated no substantial proliferation decline in response to imatinib. The patient deceased a few weeks later. Mounting in vivo and in vitro evidence indicates that 99m Tc-(V)DMSA is a credible non-invasive proliferation depicter, its cellular accumulation linked closely to phosphate uptake and kinase pathway activation. A potential role in patient management, prognosis estimation, and therapy response monitoring could occur for this tracer.

Deciphering PiT transport kinetics and substrate specificity using electrophysiology and flux measurements

Members of the SLC20 family or type III Na(+) -coupled P(i) cotransporters (PiT-1, PiT-2) are ubiquitously expressed in mammalian tissue and are thought to perform a housekeeping function for intracellular P(i) homeostasis. Previous studies have shown that PiT-1 and PiT-2 mediate electrogenic P(i) cotransport when expressed in Xenopus oocytes, but only limited kinetic characterizations were made. To address this shortcoming, we performed a detailed analysis of SLC20 transport function. Three SLC20 clones (Xenopus PiT-1, human PiT-1, and human PiT-2) were expressed in Xenopus oocytes. Each clone gave robust Na(+)-dependent (32)P(i) uptake, but only Xenopus PiT-1 showed sufficient activity for complete kinetic characterization by using two-electrode voltage clamp and radionuclide uptake. Transport activity was also documented with Li(+) substituted for Na(+). The dependence of the P(i)-induced current on P(i) concentration was Michaelian, and the dependence on Na(+) concentration indicated weak cooperativity. The dependence on external pH was unique: the apparent P(i) affinity constant showed a minimum in the pH range 6.2-6.8 of approximately 0.05 mM and increased to approximately 0.2 mM at pH 5.0 and pH 8.0. Xenopus PiT-1 stoichiometry was determined by dual (22)Na-(32)P(i) uptake and suggested a 2:1 Na(+):P(i) stoichiometry. A correlation of (32)P(i) uptake and net charge movement indicated one charge translocation per P(i). Changes in oocyte surface pH were consistent with transport of monovalent P(i). On the basis of the kinetics of substrate interdependence, we propose an ordered binding scheme of Na(+):H(2)PO(4)(-):Na(+). Significantly, in contrast to type II Na(+)-P(i) cotransporters, the transport inhibitor phosphonoformic acid did not inhibit PiT-1 or PiT-2 activity.

Scintimammographic detection of usual ductal breast hyperplasia with increased proliferation rate at risk for malignancy

OBJECTIVES

To estimate whether breast uptake of (99m)Tc-(V)DMSA and (99m)Tc-sestamibi in usual ductal epithelial breast hyperplasia (UDH) and apocrine metaplasia is related to cell proliferation rate (Ki-67) and oestrogen receptor (ER) expression, both of which are associated with the potential risk of evolving to malignancy.

METHODS

Among patients referred for suspicious breast findings on palpation and/or mammography and evaluated preoperatively with both radiopharmaceuticals, we retrospectively studied 17 (10 with UDH: group I; and seven with apocrine metaplasia: group II). Lesion-to-background (L/B) ratios in early and late acquisitions were calculated for both radiotracers in both groups, as well as their retention ratios. Ki-67 and oestrogen receptor expression were determined immunohistochemically. The late L/B ratios between the two tracers were compared, as were the late ratios for each tracer between Ki-67 < or = 3% and > 3%, and between ER < or = 15% and > 15%. Linear regression analysis was also performed between L/B and retention ratios and Ki-67 expression.

RESULTS

There was a significant increase of the (99m)Tc-(V)DMSA L/B ratio in late images as compared to the early images in group I (P<0.05), while in group II it was not significantly increased (P=0.084). (99m)Tc-sestamibi ratios did not demonstrate variability over time in either group (P=0.156 and 0.274, respectively). Significant coefficient correlation was found between the (99m)Tc-(V)DMSA L/B(late) ratios and retention ratios and Ki-67 levels only for group I (r=0.889, P<0.001 and r=0.802, P<0.01, respectively). The (99m)Tc-(V)DMSA L/B(late) ratios in group I were significantly higher when Ki-67 > 3% than when Ki-67 < or = 3% (P=0.016) but did not differ considerably between ER > 15% and < or = 15% (P=0.732).

CONCLUSION

(99m)Tc-(V)DMSA uptake in UDH correlates with Ki-67 expression. This could prove useful in identifying women with benign but high-risk breast pathologies who might benefit from chemoprophylaxis.

Influence of Pi3-K and PKC activity on 99mTc-(V)-DMSA uptake: correlation with tumour aggressiveness in an in vitro malignant glioblastoma cell line model

PURPOSE

Intensive proliferation and a high degree of migration and invasion are characteristic features of malignant glioblastomas, associated with a poor prognosis. Phosphatidylinositol-3-kinase (Pi3-K) and protein kinase C (PKC) are two phosphorylated proteins involved in glioblastoma cell progression. Phosphorylated focal adhesion protein kinase (FAK) has also been reported to be involved in tumour progression. In a recent study, we demonstrated a correlation between phosphorylated FAK, proliferation rate and 99mTc-(V)-dimercaptosuccinate [(V)-DMSA] uptake. We hypothesised that 99mTc-(V)-DMSA could be a potential imaging agent to evaluate glioblastoma aggressiveness. The aim of the present study was to assess the relationship between 99mTc-(V)-DMSA incorporation rate and modulation of Pi3-K and PKC activity.

METHODS

Proliferation, migration and invasion capacities in the presence of protein kinase modulators-staurosporine (PKC inhibitor), 4-phorbol 12-myristate 13-acetate (PMA; PKC activator) and LY294002 (Pi3-K inhibitor)-were correlated with 99mTc-(V)-DMSA cell accumulation in an in vitro model of several malignant glioma cells: G111 (grade II), U-87-MG (grade III) and G152 (grade IV).

RESULTS

In all cell lines tested, LY294002 and staurosporine treatment inhibited cell proliferation, migration and invasion. In contrast, treatment with PMA stimulated tumour aggressiveness. 99mTc-(V)-DMSA uptake was strongly correlated with the % of cellular proliferation (r=0.8462) and the % of cellular migration (r=0.9081), and to a lesser extent with the % of cellular invasion (r=0.7761).

CONCLUSION

Our results clearly demonstrated that 99mTc-(V)-DMSA reflects Pi3-K and PKC activity and is correlated with tumour aggressiveness. 99mTc-(V)-DMSA could be a reliable in vivo marker providing additional information on the biological status of malignant glioblastoma.

Correlation between 99mTc-(V)-DMSA uptake and constitutive level of phosphorylated focal adhesion kinase in an in vitro model of cancer cell lines

PURPOSE

Although a number of prognostic indicators have been developed, it is still difficult to predict the biological behaviour of all cancer types.( 99m)Tc-(V)-DMSA (V DMSA) uptake and focal adhesion kinase (FAK) expression and activation level could be potential agents for this purpose. We hypothesised the existence of a correlation between V DMSA, whose uptake is linked to phosphate ions, essential compounds for tumour growth and cell proliferation, and the adhesion protein FAK, whose elevated expression and level of constitutive activation are implicated in cancer progression. The aim of this study was to assess the relationship between V DMSA incorporation rate and FAK expression and activation by phosphorylation on tyrosine 397 residue.

METHODS

We determined V DMSA uptake in six different cancer cell lines and we measured FAK expression and activation by using Western Blotting analysis. Correlations with factors known to be associated with poor prognosis, such as invasive potential, resistance to chemotherapy and proliferation rate, were also investigated.

RESULTS

The cell lines exhibited different V DMSA incorporation rates. In addition, these cells showed the same FAK expression, but various degrees of activation. A correlation was observed between V DMSA uptake and level of FAK phosphorylation and between V DMSA or constitutive FAK activation and proliferation rate. However, no correlation was shown between these parameters and the other factors tested, i.e. invasive potential and anticancer drug resistance.

CONCLUSION

The results of this in vitro study clearly demonstrate that phosphorylation of FAK, proliferation rate and V DMSA uptake are closely related. Because proliferation and a high level of constitutive FAK activation are linked to cancer progression, it can be assumed that in vivo V DMSA uptake reflects tumour aggressiveness.

Imaging in situ breast carcinoma (with or without an invasive component) with technetium-99m pentavalent dimercaptosuccinic acid and technetium-99m 2-methoxy isobutyl isonitrile scintimammography

Introduction

The aim of the study was to retrospectively define specific features of the technetium-99m pentavalent dimercaptosuccinic acid (^99mTc-(V)DMSA) and technetium-99m 2-methoxy isobutyl isonitrile (^99mTc-Sestamibi [^99mTc-MIBI]) distribution in ductal breast carcinoma in situ and lobular breast carcinoma in situ (DCIS/LCIS), in relation to mammographic, histological and immunohistochemical parameters.

Materials and methods

One hundred and two patients with suspicious palpation or mammographic findings were submitted preoperatively to scintimammography (a total of 72 patients with ^99mTc-(V)DMSA and a total of 75 patients with ^99mTc-Sestamibi, 45 patients receiving both radiotracers). Images were acquired at 10 min and 60 min, and were evaluated for a pattern of diffuse radiotracer accumulation. The tumor-to-background ratios were correlated (T-pair test) with mammographic, histological and immunohistochemical characteristics.

Results

Histology confirmed malignancy in 46/102 patients: 20/46 patients had DCIS/LCIS, with or without coexistent invasive lesions, and 26/46 patients had isolated invasive carcinomas. Diffuse ^99mTc-(V)DMSA accumulation was noticed in 18/19 cases and ^99mTc-Sestamibi in 6/13 DCIS/LCIS cases. Epithelial hyperplasia demonstrated a similar accumulation pattern. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value for each tracer were calculated. Solely for ^99mTc-(V)DMSA, the tumor-to-background ratio was significantly higher at 60 min than at 10 min and the diffuse uptake was significantly associated with suspicious microcalcifications, with the cell proliferation index ≥ 40% and with c-erbB-2 ≥ 10%.

Conclusion

^99mTc-(V)DMSA showed high sensitivity and ^99mTc-Sestamibi showed high specificity in detecting in situ breast carcinoma (^99mTc-(V)DMSA especially in cases with increased cell proliferation), and these radiotracers could provide clinicians with preoperative information not always obtainable by mammography.