S Chiacchio

Reconstitution of functional dopamine D2s receptor by co-expression of amino- and carboxyl-terminal receptor fragments

An N-terminal dopamine D(2s) receptor clone was constructed and coexpressed in COS-7 cells together with a separate gene fragment coding for the C-terminal sequence of the dopamine D(2s) receptor. The truncated receptor (referred to as D(2trunc)) contained transmembrane domains I-V and the N-terminal portion of the third cytoplasmic loop, whereas the C-terminal receptor fragment (referred to as D(2tail)) contained transmembrane domains VI and VII and the adjacent intra- and extracellular sequences of the dopamine D(2s) receptor. Expression in COS-7 cells of either of these two polypeptides alone did not result in any detectable [3H]methylspiperone binding activity. However, specific [3H]methylspiperone binding could be observed after coexpression of the D(2trunc) and D(2tail) gene constructs; the number of receptors present on the plasma membrane was about 10% with respect to that of the wild type. The binding properties of the coexpressed fragments were similar to those of the wild-type dopamine D(2s) receptor for agonists and antagonists. Functional stimulation of the cotransfected D(2trunc) and D(2tail) fragments with quinpirole resulted in the inhibition of adenylate cyclase activity. Maximal inhibition corresponds to a 28% decrease in forskolin-stimulated adenylate cyclase. The apparent IC(50) of quinpirole was 5.1+/-0.3 mcM. These findings confirm and extend analogous data for other G protein-coupled receptors and indicate that this phenomenon is of general importance for the entire family of these proteins.

Sentinel lymph node mapping in melanoma: the issue of false-negative findings.

Abstract Management of cutaneous melanoma has changed after introduction in the clinical routine of sentinel lymph node biopsy (SLNB) for nodal staging. By defining the nodal basin status, SLNB provides a powerful prognostic information. Nevertheless, some debate still surrounds the accuracy of this procedure in terms of false-negative rate. Several large-scale studies have reported a relatively high false-negative rate (5.6%–21%), correctly defined as the proportion of false-negative results with respect to the total number of “actual” positive lymph nodes. In this review, we identified all the technical aspects that the nuclear medicine physician, the surgeon, and the pathologist should take into account to improve accuracy of the procedure and minimize the false-negative rate. In particular, SPECT/CT imaging detects more SLNs than those found by planar lymphoscintigraphy. Furthermore, the nuclear medicine community should reach a consensus on the radioactive counting rate threshold to better guide the surgeon in identifying the lymph nodes with the highest likelihood of housing metastases (“true biologic SLNs”). Analysis of the harvested SLNs by conventional techniques is also a further potential source for error. More accurate SLN analysis (eg, molecular analysis by reverse transcriptase–polymerase chain reaction) and more extensive SLN sampling identify more positive nodes, thus reducing the false-negative rate. The clinical factors identifying patients at higher-risk local recurrence after a negative SLNB include older age at diagnosis, deeper lesions, histological ulceration, and head-neck anatomic location of the primary lesion. The clinical impact of a false-negative SLNB on the prognosis of melanoma patients remains controversial, because the majority of studies have failed to demonstrate overall statistically significant disadvantage in melanoma-specific survival for false-negative SLNB patients compared with true-positive SLNB patients. When new more effective drugs will be available in the adjuvant setting for stage III melanoma patients, the implication of an accurate staging procedure for the sentinel lymph nodes will be crucial for both patients and clinicians. Standardization and accuracy of SLN identification, removal, and analysis are required.

Pharmacological evidence of muscarinic receptor heterodimerization

Publisher Summary This chapter discusses pharmacological evidence of muscarinic receptor heterodimerization. G protein-coupled receptors are transmembrane proteins that mediate a variety of signaling processes, such as neurotransmission, hormonal response, olfaction, and light transduction. Muscarinic receptors are members of this family and molecular cloning has revealed the existence of five different subtypes that show a high degree of sequence homology but differ in their ligand binding and functional properties, as well as in their tissue distribution. They are predicted to be composed of seven hydrophobic transmembrane domains (TMDs I-VII) connected by alternating cytoplasmic and extracellular loops, an extracellular amino-terminal domain, and an intracellular carboxyl-terminal segment. While they are generally considered as closely-packed structures, an increasing amount of evidence indicates that they can behave structurally in a fashion analogous to multiple subunit receptors. The subunit characteristic of the receptor could be at the basis of receptor interaction with the formation of new functional structures, the simplest of which is a dimer. The property of receptors to cross-interact at the molecular level suggests that when different subtypes of muscarinic receptors are co-expressed in the same cells, they might interact to form heterodimers with new pharmacological properties.

Sentinel Lymph Node Biopsy in Breast Cancer: Indications, Contraindications, and Controversies.

Abstract Axillary lymph node status, a major prognostic factor in early-stage breast cancer, provides information important for individualized surgical treatment. Because imaging techniques have limited sensitivity to detect metastasis in axillary lymph nodes, the axilla must be explored surgically. The histology of all resected nodes at the time of axillary lymph node dissection (ALND) has traditionally been regarded as the most accurate method for assessing metastatic spread of disease to the locoregional lymph nodes. However, ALND may result in lymphedema, nerve injury, shoulder dysfunction, and other short-term and long-term complications limiting functionality and reducing quality of life. Sentinel lymph node biopsy (SLNB) is a less invasive method of assessing nodal involvement. The concept of SLNB is based on the notion that tumors drain in an orderly manner through the lymphatic system. Therefore, the SLN is the first to be affected by metastasis if the tumor has spread, and a tumor-free SLN makes it highly unlikely for other nodes to be affected. Sentinel lymph node biopsy has become the standard of care for primary treatment of early breast cancer and has replaced ALND to stage clinically node-negative patients, thus reducing ALND-associated morbidity. More than 20 years after its introduction, there are still aspects concerning SLNB and ALND that are currently debated. Moreover, SLNB remains an unstandardized procedure surrounded by many unresolved controversies concerning the technique itself. In this article, we review the main indications, contraindications, and controversies of SLNB in breast cancer in the light of the most recent publications.

Dopamine agonists and analogues have an antiproliferative effect on CHO-K1 cells

Epidemiological studies have shown a reduced incidence of cancer in Parkinson’s disease. Since nearly all parkinsonian patients with clinical impairment are treated with L-β-3,4-dihydroxyphenylalanine (L-DOPA) and dopamine (DA)ergic agonists, a possibility exists that these therapeutic agents can influence the risk of cancer. We studied the antiproliferative effect of these therapeutic agents (and substances structurally correlated) on Chinese hamster ovary (CHO)-K1 cell growth. Among the compounds tested, apomorphine proved to be the most potent inhibitor of CHO-K1 cell growth, with an EC50 of 3.35 ± 0.12 μM. The apomorphine analogues, apocodeine and hydroxyethylnorapomorphine, were less active as inhibitors of CHO-K1 cell growth. The activity of DA, 6-hydroxydopamine (6-OHDA), phe-nylethylamine (PEA), L-DOPA and bromocriptine as antiproliferative was one order of magnitude lower than that of apomorphine while pergolide was ineffective. To test whether or not the oxidative potential of these compounds was important for their antiproliferative effect, several antioxidants were assayed. Among them, glutathione (GSH) and dithio-threitol (DTT) were effective in reversing the antiproliferative effect of apomorphine, DA, 6-OHDA and PEA, conversely they did not work with bromocriptine. GSH and DTT are sulphydryl-reducing agents; while their effect could explain the efficacy against apomorphine, DA and 6-OHDA, it is difficult to understand why they should have any effect on PEA as this substance does not react with sulphydryl groups. The oxidative potential as a mechanism of action was also questioned by the results obtained with dihydrorhodamine 123, a probe that changes its fluorescent emission wave when oxidized. None of the compounds, with the exception of 6-OHDA, had any effect on the fluorescent emission wave of the probe at the maximal concentrations used to inhibit CHO-K1 cell growth. At concentrations five times higher, apomorphine and DA generated reactive oxygen species but PEA and bromocriptine did not. These data demonstrate that the antiproliferative effect of these compounds is not due to their oxidative potential, but another mechanism must be postulated.

Role of 18F-DOPA PET/CT in diagnosis and follow-up of adrenal and extra-adrenal paragangliomas.

Purpose The objective of this study was to establish the clinical value of 18F-DOPA PET/CT in patients with adrenal and extra-adrenal paragangliomas (PGLs). Methods Twenty-six consecutive patients with suspected or recurrent PGL underwent MR (and/or CT) and 18F-DOPA PET/CT. Histopathology confirmation was obtained in 20 cases. Genetic analysis on known susceptibility genes for PGL (VHL, RET, SDHx, TMEM127) was available in 13 patients. Results Fourteen patients were affected by PGL (8 with head/neck location, 6 with abdominal/thoracic location), whereas 12 showed masses of other origin. Three patients proved to be SDHD, 1 SDHB, 2 SDHC, and 1 TMEM127 mutation carriers. 18F-DOPA PET/CT showed pathological uptake in 13 of 26 patients. The procedure identified all PGLs except one with bone metastases (previous malignant adrenal PGL). No uptake was found in patients without proven PGL. Thus, in the whole group, 18F-DOPA PET/CT sensitivity was 92.8%, and specificity was 100% with positive and negative predictive values of 100% and 92.3%, respectively. Total diagnostic accuracy was 96.2%. In the head/neck subgroup, sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy were 100%. In the abdominal location, sensitivity was 80% and specificity was 100%, and positive and negative predictive values were 100% and 91.7%, respectively. Abdominal diagnostic accuracy was 93.7%. Radiotracer uptake was superimposable in head/neck PGLs versus abdominal PGLs and in mutated versus wild-type patients. Conclusions The high diagnostic performance of 18F-DOPA PET/CT showed this technique to be a useful tool in detecting PGLs, above all those located at the head/neck site, regardless of the genetic pattern.

Preoperative and Intraoperative Lymphatic Mapping for Radioguided Sentinel Node Biopsy in Breast Cancer

Axillary lymph node status still is a major prognostic factor in early-stage breast cancer, providing information that is important for tailoring post-surgical treatment [1,2].

Diagnostic Applications of Nuclear Medicine: Penile Cancer

Penile carcinomas are rare in most developed countries; in contrast, this cancer is not infrequent in the tropical and subtropical regions of Latin America, Asia, and Africa. In addition, penile cancer is common in regions with high prevalence of human papilloma virus infection. More than 95% of penile carcinomas are of the squamous cell type; other histologic types include basal cell carcinoma, melanoma, and sarcoma. Penile carcinoma usually spreads through lymphatic channels to the superficial and deep inguinal lymph nodes; subsequently iliac lymph nodes are involved. The presence and extent of metastatic disease in inguinal nodes is the single most important prognostic factor in patients with penile cancer. Primary evaluation of penile cancer is based on physical examination including inguinal lymph node palpation. Ultrasound and MRI can provide information on tumor invasion of the corpora cavernosa if organ preservation is planned. Ultrasound can be used to evaluate nonpalpable inguinal lymph nodes, whereas pelvic CT scan can be used to assess pelvic lymph nodes. Lymphoscintigraphy, preferably with SPECT/CT imaging, and subsequently sentinel lymph node biopsy is gaining popularity in clinical practice, especially in patients with nonpalpable lymph nodes; sensitivity reported for this local staging approach ranges from 70% to 86%.Assessment of distantmetastases should be performed in patients with positive inguinal nodes; this includes abdomen and pelvis CT, chest X-ray, or thoracic CT. [F]FDG PET/CT can be used for initial staging of penile cancer with pooled sensitivity and specificity of 80.9% and 92.4% respectively; this staging technique is particularly advocated for patients with positive lymph nodes. [F]FDG PET/CT can also be employed to monitor the efficacy of induction chemotherapy. Follow-up of penile cancer is based mainly on clinical evaluation, while radionuclide imaging techniques have rarely been used for restaging purposes during regular follow-up.

Cancer of the Prostate, Testicles and Penis

In 2009, approximately 192,000 men were diagnosed with prostate cancer (PCa) in the USA. Adenocarcinoma, originating in the peripheral zone of the gland, is the most frequent histology. The clinical outcome of PCa is highly variable. PCa is diagnosed by transrectal ultrasound (TRUS)-guided biopsies. PCa is staged using the AJCC TNM classification. A combination of transrectal MRI and CT is used to detect extracapsular disease and distant metastases. Bone scintigraphy is recommended as the first-line modality to detect skeletal metastases. Bone scintigraphy may be also used to monitor the response to therapy. Lymphoscintigraphy and radioguided sentinel lymph node (SLN) biopsy is potentially a reliable procedure for nodal staging. [18F]FDG PET/CT does not play a major role in the initial evaluation and staging of PCa. In patients with advanced metastatic disease, however, [18F]FDG PET/CT often displays high uptake, discriminating active from quiescent osseous lesions. Following radical prostatectomy, prostate-specific antigen (PSA) levels greater than 0.2 ng/mL indicate biochemical failure, whereas in patients treated with antiandrogenic therapy or radiotherapy, a PSA value greater than 2 ng/mL above the nadir after therapy represents recurrent/persistent cancer.

Modalità di acquisizione con gamma-camera

Il presente capitola riguarda alcuni dei parametri pratici piu importanti che devono essere impostati quando si esegue un’acquisizione con la gamma-camera. A causa delle differenze tra le varie ditte, non saranno trattati gli aspetti tecnici legati ai sistemi di correzione per l’attenuazione mediante sorgente trasmissiva gamma o mediante TC. Per maggiori dettagli operativi sulle modalita di verifica dei corretti parametri di acquisizione, si rimanda al successivo Capitolo 11.