Expression of the GLUT1 and GLUT9 facilitative glucose transporters in embryonic chondroblasts and mature chondrocytes in ovine articular cartilage.

Glucose transport across the chondrocyte membrane is essential for chondrogenesis and the development of the skeletal system. We have previously used RT-PCR to show that fully developed human articular chondrocytes express transcripts for the GLUT1 and GLUT9 glucose transporters. In this study we report on the expression and immunohistochemical localization of the GLUT1 and GLUT9 proteins in embryonic and mature ovine cartilage. We also provide Western blot evidence for GLUT1 and GLUT9 expression in mature ovine chondrocytes. Ovine embryos (developmental stages E32 to E36 and E42 to E45) were obtained from pregnant ewes humanely killed by injection with sodium pentobarbitone. Embryos were fixed and processed for immunohistochemistry. Polyclonal antibodies to GLUT1 and GLUT9 revealed that both transporters are expressed in developing chondrocytes in ovine embryos and in the superficial, middle and deep layers of ovine cartilage from mature animals. GLUT1 expression was observed in erythrocytes and organs including heart, liver, and kidney. GLUT9 was also found in heart, kidney and liver. Western blotting confirmed the presence of the GLUT1 protein which migrated between the 50 and 64 kDa markers and two specific GLUT9 bands migrating under the 50 and 60 kDa markers, respectively. The presence of GLUT1 and GLUT9 in developing joints of ovine embryos suggests that these proteins may be important in glucose delivery to developing chondroblasts. Expression of these GLUT isoforms may be an important bioenergetic adaptation for chondrocytes in the extracellular matrix of developing cartilage.

Endocrine pancreatic tumors.

Neuroendocrine tumors of the pancreas are rare neoplasms that may arise sporadically or in association with a hereditary endocrine neoplasia syndrome. Effective management requires directed biochemical testing, careful choice of preoperative imaging tests, and complete pancreatic exploration by an experienced endocrine surgeon utilizing intraoperative ultrasound. Pancreatic endocrine tumors arising in the familial setting present unique diagnostic and therapeutic dilemmas.

Surgical treatment of medullary thyroid carcinoma.

Medullary thyroid carcinoma (MTC) is a malignancy of the parafollicular C cells of the thyroid gland. It occurs sporadically or as part of the multiple endocrine neoplasia type 2 (MEN 2) syndromes. Patients who have inherited a mutation in the RET proto-oncogene should have thyroidectomy early in life to prevent formation and spread of this cancer. Most patients with sporadic disease present with a palpable neck mass. The diagnosis is made by fine needle aspiration biopsy and by measuring calcitonin levels in the blood. Primary treatment consists of surgical resection including a total thyroidectomy, central neck nodal dissection and functional lateral neck nodal dissections. Most patients with a palpable primary tumour have nodal disease present at the time of operation, and nodal involvement is often bilateral. Adequate resection of the primary tumour and cervical lymph nodes is important to optimize outcome and minimize the risk of recurrent disease. Proper handling of the parathyroid glands prevents hypoparathyroidism. Following primary surgical resection, more than half of the patients will have recurrent disease with persistent elevation of calcitonin levels. Currently, there is no adequate systemic therapy for treating recurrent disease. Surgical reoperation or conservative observation are the best available options. Diagnostic laparoscopy for liver evaluation is the most sensitive diagnostic test to detect the presence of distant metastases.

Molecular characterization and partial cDNA cloning of facilitative glucose transporters expressed in human articular chondrocytes; stimulation of 2-deoxyglucose uptake by IGF-I and elevated MMP-2 secretion by glucose deprivation.

OBJECTIVE: Recent evidence suggests that human chondrocytes express several facilitative glucose transporter (GLUT) isoforms and also that 2-deoxyglucose transport is accelerated by cytokine stimulation. The aim of the present investigation was to determine if human articular chondrocytes express any of the recently identified members of the GLUT/SLC2A gene family and to examine the effects of endocrine factors, such as insulin and IGF-I on the capacity of human chondrocytes for transporting 2-deoxyglucose. DESIGN/METHODS: PCR, cloning and immunohistochemistry were employed to study the expression of GLUT/SLC2A transporters in normal human articular cartilage. The uptake of 2-deoxyglucose was examined in monolayer cultured immortalized human chondrocytes following stimulation with TNF-alpha, insulin and IGF-I. Levels of MMP-2 were assessed by gelatin zymography following glucose deprivation of alginate cultures. RESULTS: Using PCR we detected transcripts for eight glucose transporter isoforms (GLUTs 1, 3, 6, 8, 9, 10, 11 and 12) and for a fructose transporter (GLUT5) in human articular cartilage. Expression of GLUT1, GLUT3 and GLUT9 proteins in normal human articular cartilage was confirmed by immunohistochemistry. The uptake of 2-deoxyglucose was dependent on time and temperature, inhibited by cytochalasin B and phloretin, and significantly accelerated in chondrocyte cultures stimulated with IGF-I. However, 2-deoxyglucose uptake was unaffected by short and long-term insulin treatment, which ruled out a functional role for insulin-sensitive GLUT4-mediated glucose transport. Furthermore, secretion of MMP-2 was increased in alginate cultures deprived of glucose. CONCLUSIONS: The data supports a critical role for glucose transport and metabolism in the synthesis and degradation of cartilage.

Allelic imbalance of the mutant and wild-type RET allele in MEN 2A-associated medullary thyroid carcinoma.

Germline mutations of the RET proto-oncogene are responsible for the familial tumor syndrome called multiple endocrine neoplasia type 2 (MEN 2) that includes medullary thyroid carcinoma (MTC). Although inherited mutations of RET lead to tumor formation in patients with MEN 2, it is not understood why only selected cells develop into tumors. We have recently shown that duplication of the mutated RET allele or loss of the wild-type allele might represent mechanisms of tumorigenesis in patients with MEN 2A-related pheochromocytoma. We now analysed 19 DNA samples of MTC (15 of which were non-microdissected, four of which were microdissected) from patients with MEN 2A. Using polymorphic marker and phosphorimage densitometry analyses, we found allelic imbalance of the mutated and wild-type RET allele in six of 19 DNA MTC samples. Of note, two of the four microdissected tumor DNA samples showed allelic imbalance of RET, whereas only four of the 15 non-microdissected MTC samples did. These results underscore the significance of microdissection in the analysis of tumor DNA. In our study, some of the non-microdissected tumor DNA samples may have failed to display allelic imbalance of RET, because of contamination of tumor DNA with nonneoplastic DNA or noninformative microsatellite marker analysis. Taken together, our results suggest allelic imbalance between mutated and wild-type RET as a possible mechanism for tumor formation in some patients with MEN 2A-related MTC.

Risk of malignancy in thyroid incidentalomas identified by fluorodeoxyglucose-positron emission tomography.

BACKGROUND: Thyroid tumors often exhibit increased metabolic activity, as evidenced by enhanced glucose uptake on positron emission tomography (PET) with use of (18)F-fluorodeoxyglucose (FDG). The incidence of new thyroid lesions found on routine FDG-PET has not been previously reported. METHODS: A retrospective review of all patients who underwent FDG-PET imaging at our institution from June 1, 1996, through March 15, 2001, identified patients with a newly diagnosed thyroid lesion. Thyroid incidentaloma was defined as a thyroid lesion seen initially on FDG-PET in a patient without a history of thyroid disease. Available follow-up data were documented. RESULTS: One hundred and two of 4525 FDG-PET examinations (2.3%) demonstrated thyroid incidentalomas. Eighty-seven of 102 patients had no thyroid histology because of other malignancies. Fifteen patients had thyroid biopsy: 7 (47%) with thyroid cancer, 6 (40%) with nodular hyperplasia, 1 with thyroiditis, and 1 with atypical cells of indeterminate origin. The average standardized uptake values were higher for malignant compared with benign lesions. CONCLUSIONS: Thyroid incidentaloma identified by FDG-PET occurred with a frequency of 2.3%. Of the thyroid incidentalomas that underwent biopsy, 47% were found to be malignant. Given the risk of malignancy, patients with new thyroid lesions on PET scan should have a tissue diagnosis if it will influence outcome and management. Standardized uptake values may be helpful in predicting benign versus malignant histology.

Outcomes analysis in patients undergoing laparoscopic adrenalectomy for hormonally active adrenal tumors.

BACKGROUND: Laparoscopic adrenalectomy (LA) has become the preferred method of removal of most adrenal neoplasms, but few studies have evaluated the functional outcomes of this approach. The purpose of this study was to analyze our operative results and the clinical and biochemical responses to LA in patients with various hormonally active adrenal tumors. METHODS: From 1993 through November 2000, 72 patients with functional adrenal tumors underwent attempted LA. Data were obtained retrospectively by review of medical records, during routine follow-up, and by patient questionnaire. RESULTS: Indications for adrenalectomy were pheochromocytoma (n = 35), aldosteronoma (n = 29), cortisol-producing adenoma (n = 5), and adrenocorticotropic hormone-dependent Cushing's syndrome (n = 3). LA was completed in 70 of 72 patients, with 2 conversions (3%) to open adrenalectomy. Mean operative time for unilateral LA was 176 +/- 60 minutes, and postoperative length of hospital stay averaged 3.0 +/- 1.7 days. Complications, most of which were minor, occurred in 19% of patients; there were no serious complications or perioperative deaths. Two patients were unavailable for follow-up. At a mean follow-up interval of 37.6 months after LA (range, 2-90 months), resolution of clinical and biochemical signs of adrenal hyperfunction was accomplished in 34 of 34 patients with pheochromocytomas, 25 of 26 patients with aldosteronomas, 5 of 5 patients with cortisol-producing adenomas, and 3 of 3 patients with andrenocorticotropic hormone-dependent Cushing's syndrome. Two patients with multiple endocrine neoplasia (MEN) type 2 had contralateral pheochromocytomas removed 4 and 5 years after the initial surgery. Persistent hypertension necessitating medication was present in 72% of patients with aldosteronomas, although 92% of these patients had improved blood pressure control after LA. Recurrent hypokalemia developed in 1 patient (4%) with a cortical nodule in the contralateral adrenal. No local or distant tumor recurrences have occurred. CONCLUSIONS: LA results in an excellent clinical outcome in patients with various functional endocrine tumors. LA is associated with few major complications, and clinical and biochemical cure rates are comparable with those of open adrenalectomy during long-term follow-up.

Adrenal incidentaloma.

Because of the frequent use of computed tomography and other abdominal imaging modalities, clinicians more frequently see the incidentally discovered, clinically silent adrenal mass. Most adrenal incidentalomas should be evaluated for hormonal activity and assessed for their risk of malignancy. Adrenalectomy is indicated for hyperfunctioning tumors and for any potential primary malignant adrenal lesion. Nonfunctioning cortical adenomas < 4 to 5 cm in size should be followed clinically and radiographically. Laparoscopic adrenalectomy has been used increasingly as the preferred approach in patients who require surgical resection whereas open adrenalectomy is reserved for patients with large, malignant tumors. The indications for adrenalectomy in patients with nonfunctioning adrenal tumors should not be liberalized because of the laparoscopic approach.

Evaluation of the performance and clinical impact of a rapid intraoperative parathyroid hormone assay in conjunction with preoperative imaging and concise parathyroidectomy.

BACKGROUND: (99m)Tc-sestamibi scans and rapid, intraoperative intact parathyroid hormone (PTH) assays allow preoperative identification of diseased glands and intraoperative confirmation of diseased gland removal, respectively. Use of these two new technologies may facilitate simpler, more concise surgery, shorter hospital stays, and decreased costs for frozen-section analysis. One major drawback to this new strategy has been the high cost of rapid point-of-care PTH assays. METHODS: We performed rapid PTH assays with the DPC Turbo PTH assay on the DPC IMMULITE automated analyzer. The number of intraoperative frozen sections, type of anesthesia, surgical approach, length of hospital stay, and pre- and postoperative calcium values were compared between a group of 49 patients undergoing parathyroidectomy where the intraoperative PTH assay was used in conjunction with preoperative imaging, and a historical control group of 55 patients before the use of these two technologies in our institution. RESULTS: Comparison of the Turbo PTH assay to the standard IMMULITE PTH assay gave the following: y = 1.08 x - 4.36 (r = 0.97; n = 48). For the 49 patients, the median turnaround time for each intraoperative PTH determination was 19 min (range, 14-40 min). The median decrease in PTH values from baseline was 88% (range, 33-99%). Thirty-seven patients required two PTH determinations, 7 required three, 4 had four, and 1 required five determinations. The average laboratory cost for the rapid intraoperative PTH assays was < $100 per patient (range, $55 to $113). Compared with the control group, the experimental group had significantly fewer frozen sections (1.4 vs 2.5; P < 0.0001), shorter hospital stays (17 discharged on the day of surgery vs none discharged on the day of surgery; P < 0.0001), greater use of local anesthesia (33% vs 0%; P < 0.001), and more unilateral, rather than bilateral neck explorations (65% vs 0%; P < 0.001). CONCLUSIONS: The combination of intraoperative Turbo PTH assay and preoperative (99m)Tc-sestamibi scans can lead to significant decreases in laboratory and surgical pathology costs, hospital stays, and exposure to general anesthesia by facilitating concise parathyroidectomy surgery.

Strategy for identification of novel glucose transporter family members by using internet-based genomic databases.

BACKGROUND: We previously reported that medullary thyroid carcinomas and pheochromocytomas avidly take up the glucose analog fluoro-deoxyglucose on positron emission tomography but do not express any of the known human facilitative glucose transporters. We therefore hypothesized that a novel glucose transporter is responsible for glucose uptake in these tumors. METHODS: Internet-based Expressed Sequence Tags and high throughput genome sequence databases were screened for novel sequences homologous to the known glucose transporters. Derived clones were used to screen cDNA libraries. Sequence comparison and hydropathic analysis of the putative proteins were performed. RESULTS: We identified 2 novel genes (GLUT8 and GLUT9) that are members of the facilitative glucose transporter family. The putative GLUT8 and GLUT9 proteins have 44% and 31% sequence identity to GLUT5 and GLUT3, respectively. Hydropathic analysis showed both have exofacial and transmembrane domains consistent with a hexose transporter. CONCLUSIONS: By using the Expressed Sequence Tags database, we identified novel members of the glucose transporter family. Further work will establish function and expression patterns in medullary thyroid carcinomas and pheochromocytomas. Internet-based genomic databases allow rapid screening and identification of candidate sequences of novel members of human gene families.

Soft-tissue sarcomas.

Sarcomas of the soft tissues are challenging lesions for the surgical oncologist. Careful planning must be done at all stages of diagnosis and treatment, because every sarcoma is unique with respect to histologic type, size, and location. Pretreatment discussions in a multidisciplinary format are useful to ensure appropriate and effective management of these tumors.

Cloning and expression analysis of a novel member of the facilitative glucose transporter family, SLC2A9 (GLUT9).

Several lines of evidence suggest the existence of additional members of the mammalian facilitative glucose transporter family. A human cDNA sequence corresponding to a novel member of the glucose transporter family (GLUT1-5) was identified (GLUT9; HGMW-approved symbol SLC2A9), and it encodes a putative transporter of 540 amino acids. The predicted protein has sequence identity of 44 and 38% to Glut5 and Glut1, respectively. Based on hydropathic analysis, the novel transporter's predicted topology consists of 12 transmembrane domains, similar to the other family members. Northern analysis reveals three mRNA species: a major transcript of 1.9 kb and two other transcripts of 3.1 and 5.0 kb, found primarily in kidney and liver, but present at low levels in several other tissues. GLUT9 was localized to chromosome 4 using a monochromosomal human/rodent somatic cell hybrid mapping panel. A portion of the GLUT9 cDNA is represented in a National Center for Biotechnology Information UniGene cluster, which maps to chromosome 4p15.3-p16.

Multiple endocrine neoplasias.

Multiple endocrine neoplasia type 1 (MEN 1), and the multiple endocrine neoplasia type 2 syndromes (MEN 2A, MEN 2B, and familial non-MEN medullary thyroid carcinoma [FMTC]) encompass a wide range of endocrine problems, but arise from only two genes: the MEN 1 tumor suppressor gene and the RET proto-oncogene. MEN 1 is characterized by parathyroid hyperplasia, pancreaticoduodenal neuroendocrine tumors (PNTs), and pituitary adenomas. Surgery is the principal treatment modality for hyperparathyroidism and PNTs, but questions still remain concerning the timing and extent of surgery for PNTs. The MEN 2 syndromes are characterized by complete penetrance of medullary thyroid cancer. The MEN 2 syndromes differ in their variable expression of hyperparathyroidism, pheochromocytomas, and other clinical features. Genetic testing for mutations in the RET gene has revolutionized treatment by enabling thyroidectomies before significant disease occurs.

Brain metastases from medullary thyroid carcinoma in a patient with multiple endocrine neoplasia type 2A.

Medullary thyroid carcinoma (MTC) is an uncommon thyroid cancer occurring in less than 10% of patients with thyroid cancer. Brain metastasis from MTC is exceedingly rare. Only six cases of brain metastasis from MTC have been reported in the literature and none had MTC as a part of multiple endocrine neoplasia (MEN) syndrome. We report a 42-year-old Caucasian male with MEN 2A who presented with neurological symptoms 25 years after total thyroidectomy with lymphadenectomy for MTC metastatic to local lymph nodes. A brain magnetic resonance imaging (MRI) showed a 4-cm cystic mass and a 1-cm nodule in the left frontal-parietal lobe in addition to a 0.8-cm cystic mass in the left frontal lobe and multiple tiny cerebellar metastatic lesions. Partial resection of the cerebral metastasis followed by whole brain radiotherapy resulted in resolution of the neurological symptoms. However, the patient had multiple systemic metastasis from the MTC and he died of systemic complications due to metastatic MTC. To our knowledge this is the first report of brain metastases from MTC in a patient with MEN 2A.

Preservation of the recurrent laryngeal nerves in thyroid and parathyroid reoperations.

BACKGROUND: The recurrent laryngeal nerve (RLN) is vulnerable to injury in thyroid and parathyroid reoperations because of the presence of scar tissue and displacement of the nerve from its normal position. METHODS: Since 1993, we have performed 132 reoperations for recurrence of thyroid or parathyroid carcinoma (102 cases), persistent hyperparathyroidism (21 cases), and recurrent goiter (9 cases). One or both RLNs were identified in all cases (208 nerves). Exposure of the nerve was accomplished by a lateral approach (159 nerves), a low anterior approach (41 nerves), or the identification of the nerve between the larynx and the upper pole of the thyroid, in parathyroid reoperations (8 nerves). Dissection was then done while the nerve was kept in view at all times. RESULTS: Preoperatively, unilateral vocal cord paralysis was noted in 6 patients. Resection of a functioning RLN encased with a tumor was intentionally carried out in 5 patients. The RLNs were identified and preserved in all other cases. Among these 121 patients, transient hoarseness lasting up to a month occurred in 12 patients. CONCLUSIONS: Careful identification and exposure of the RLN through a previously undissected area can be done safely in thyroid and parathyroid reoperations and resulted in no permanent recurrent nerve injuries in our experience.

Compartment-mediated dissection for papillary thyroid cancer.

There is considerable controversy surrounding the appropriate treatment of papillary thyroid carcinoma (PTC), most of which centers around the extent of thyroidectomy. Despite the advocation of less than total thyroidectomy by many surgeons, there is a renewed interest by others, mainly in Europe and Japan, in the performance of routine total thyroidectomy and extensive lymph-node dissection for PTC. This has been shown to be an effective strategy for medullary thyroid carcinoma, which is not responsive to thyroid suppression or radioactive iodine treatment. PTC, however, is well treated by these adjuvant modalities and, in general, has an excellent prognosis. The benefit of extensive operations for routine cases of PTC has not been proven, and this practice is not employed by most surgeons in the United States. Node dissection is reserved for those patients with palpable adenopathy.

Patterns of nodal metastases in palpable medullary thyroid carcinoma: recommendations for extent of node dissection.

OBJECTIVE: To establish the frequency, pattern and location of cervical lymph node metastases from palpable medullary thyroid carcinoma (MTC). Recommendations are made regarding the extent of surgery for this tumor. SUMMARY BACKGROUND DATA: Medullary thyroid carcinoma is a tumor of neuroendocrine origin that does not concentrate iodine. Surgical extirpation of the thyroid tumor and cervical node metastases is the only potentially curative therapeutic option. Patterns of node metastases in the neck and guidelines for the extent of dissection for palpable MTC are not well established. METHODS: Seventy-three patients underwent thyroidectomy for palpable MTC with immediate or delayed central and bilateral functional neck dissections. The number and location of lymph node metastases in the central (levels VI and VII) and bilateral (levels II to V) nodal groups were noted and were correlated with the size and location of the primary thyroid tumor. Intraoperative assessment of nodal status by palpation and inspection by the surgeon was correlated with results of histologic examination. RESULTS: Patients with unilateral intrathyroid tumors had lymph node metastases in 81% of central node dissections, 81% of ipsilateral functional (levels II to V) dissections, and 44% of contralateral functional (levels II to V) dissections. In patients with bilateral intrathyroid tumors, nodal metastases were present in 78% of central node dissections, 71% of functional (levels II to V) node dissections ipsilateral to the largest intrathyroid tumor, and 49% of functional (levels II to V) node dissections contralateral to the largest thyroid tumor. The sensitivity of the surgeon's intraoperative assessment for nodal metastases was 64%, and the specificity was 71%. CONCLUSION: In this series, >75% of patients with palpable MTC had associated nodal metastases, which often were not apparent to the surgeon. Routine central and bilateral functional neck dissections should be considered in all patients with palpable MTC.

Laparoscopic ultrasound imaging of adrenal tumors during laparoscopic adrenalectomy.

BACKGROUND: The purpose of this study was to determine the usefulness of laparoscopic ultrasound (LUS) during laparoscopic adrenalectomy (LA) and to define the ultrasound imaging characteristics of various adrenal tumors. METHODS: LUS was utilized in 27 patients who underwent LA (including one bilateral adrenalectomy) from May 1994 to October 1998. Tumor size ranged from 1.0 to 5.5 cm (mean 3.3 cm), and a transabdominal lateral approach to LA was used. RESULTS: LUS localized the adrenal gland and tumor in all 28 adrenalectomies and demonstrated the relationship of the tumor to the kidney and adjacent vascular structures (renal artery/vein and inferior vena cava). The adrenal vein was visualized sonographically in only six cases (21 %). Pheochromocytomas were mild to markedly heterogenous, whereas most aldosteronomas and cortical adenomas were homogenous. LUS provided useful information to the surgeon in 11 of 28 cases (39%) by: 1) localizing the adrenal gland and tumor and/or guiding the dissection; 2) demonstrating that tumors > or =4 cm were confined to the adrenal gland; and 3) investigating suspected pathology in other organs. Mean operating time for LUS was 10.9 min (range 5 to 24 min) and calculated hospital charges were $602. CONCLUSIONS: LUS accurately localizes adrenal tumors, helps define their relationship to adjacent structures, and provides confirmation that larger tumors are amenable to laparoscopic resection. LUS is a useful adjunct to laparoscopic adrenalectomy in selected patients.