Ovarian cyst formation in women of reproductive age receiving mitotane as part of the treatment of adrenocortical carcinoma: Clinical and experimental observations.

INTRODUCTION: Mitotane is an adrenolytic drug that is used as an adjuvant to treat adrenocortical carcinoma. This study aimed to evaluate the clinical course and pathogenetic mechanisms underlying ovarian cyst formation in women of reproductive age diagnosed with adrenocortical carcinoma and being treated with mitotane as an adjuvant to surgery. MATERIAL AND METHODS: Five women presented with stage III-IV adrenocortical carcinoma and ovarian cyst formation during mitotane treatment. The clinical course of the disease was followed during and after treatment. The effects of mitotane on progesterone production and cell proliferation were studied in cultured human ovarian granulosa cells. RESULTS: Computed tomography and vaginal ultrasonography during mitotane treatment repeatedly demonstrated ovarian cysts of varying size without solid intralocular structures. Two women became amenorrheic during the treatment period. After mitotane cessation, the ovarian cysts disappeared and normal menstrual cycles resumed. One woman had an uncomplicated pregnancy two years after mitotane treatment. In one woman, who underwent salpingo-oophorectomy, histological analysis demonstrated benign ovarian cysts. Mitotane impeded the synthesis of progesterone, reduced the stimulatory effect of gonadotropins on progesterone formation, and reduced labeling with [3 H]thymidine in cultured granulosa cells. CONCLUSIONS: Therapeutic concentrations of mitotane are associated with the formation of benign ovarian cysts and amenorrhea. Mitotane-induced suppression of ovarian steroidogenesis and impediment of the proliferative capacity of steroid-producing cells are suggested potential pathogenetic mechanisms underlying mitotane-induced ovarian dysfunction and cyst development. Mitotane treatment does not compromise future ovarian function.

Rotavirus stimulates release of serotonin (5-HT) from human enterochromaffin cells and activates brain structures involved in nausea and vomiting.

Rotavirus (RV) is the major cause of severe gastroenteritis in young children. A virus-encoded enterotoxin, NSP4 is proposed to play a major role in causing RV diarrhoea but how RV can induce emesis, a hallmark of the illness, remains unresolved. In this study we have addressed the hypothesis that RV-induced secretion of serotonin (5-hydroxytryptamine, 5-HT) by enterochromaffin (EC) cells plays a key role in the emetic reflex during RV infection resulting in activation of vagal afferent nerves connected to nucleus of the solitary tract (NTS) and area postrema in the brain stem, structures associated with nausea and vomiting. Our experiments revealed that RV can infect and replicate in human EC tumor cells ex vivo and in vitro and are localized to both EC cells and infected enterocytes in the close vicinity of EC cells in the jejunum of infected mice. Purified NSP4, but not purified virus particles, evoked release of 5-HT within 60 minutes and increased the intracellular Ca²âº concentration in a human midgut carcinoid EC cell line (GOT1) and ex vivo in human primary carcinoid EC cells concomitant with the release of 5-HT. Furthermore, NSP4 stimulated a modest production of inositol 1,4,5-triphosphate (IP3), but not of cAMP. RV infection in mice induced Fos expression in the NTS, as seen in animals which vomit after administration of chemotherapeutic drugs. The demonstration that RV can stimulate EC cells leads us to propose that RV disease includes participation of 5-HT, EC cells, the enteric nervous system and activation of vagal afferent nerves to brain structures associated with nausea and vomiting. This hypothesis is supported by treating vomiting in children with acute gastroenteritis with 5-HT3 receptor antagonists.

Radionuclide therapy via SSTR: future aspects from experimental animal studies.

There is need for better therapeutic options for neuroendocrine tumours. The aim of this review was to summarize results of experimental animal studies and raise ideas for future radionuclide therapy based on high expression of somatostatin (SS) receptors by many neuroendocrine tumours. In summary, one of the major options is individualized treatment for each patient, including choice of SS analogues, radionuclides and treatment schedules. Other options are methods to increase the treatment effect on tumour tissue (increasing tumour uptake and retention by upregulation of receptor expression and avoiding saturation of receptor binding), methods to increase the tumour tissue response (by choice of radionuclides, SS analogues or combined therapies), and methods to reduce side effects (diminished uptake and retention in critical organs and reduced normal tissue response). Furthermore, combination therapy with other radiopharmaceuticals, cytotoxic drugs or radiosensitizers can be considered to enhance the effects of radiolabelled SS analogues.

Gastrointestinal stromal tumors (GISTs) express somatostatin receptors and bind radiolabeled somatostatin analogs.

BACKGROUND: Gastrointestinal stromal tumors (GISTs) can be effectively treated with tyrosine kinase inhibitors (TKIs). However, some patients with GIST develop drug resistance, and alternative treatment strategies are therefore needed. The aim of this study was to analyze the expression of somatostatin receptors (SSTR) in GIST as a target for peptide receptor-mediated radiotherapy (PRRT). MATERIAL AND METHODS: Expression profiling of SSTR1-5 was performed on biopsies from 34 GISTs (16 gastric tumors, 15 small intestinal tumors, and three rectal tumors). SSTR scintigraphy ((111)In-octreotide) and measurement of (111)In activity in tumor specimens was performed in seven patients. Uptake and internalization of (177)Lu- octreotate was studied in primary cell cultures from two patients. RESULTS: Quantitative PCR analysis showed expression of SSTR1 and SSTR2 in the majority of tumors, while SSTR3-5 were expressed at low levels. Immunohistochemical analysis confirmed the presence of SSTR1 and SSTR2 proteins in all GISTs, and SSTR3-5 in a subset of tumors. Diagnostic imaging by SSTR scintigraphy, using (111)In-octreotide, demonstrated tumor uptake of (111)In in three of six GIST patients. Measurement of (111)In activity in excised tumor specimens from five patients gave tumor-to-blood (T/B) activity ratios of between eight and 96. Tumor cells in primary culture (gastric and small intestinal GIST) specifically bound and internalized (177)Lu when incubated with the therapeutic compound (177)Lu-octreotate for 4-48 hours (p < 0.05). CONCLUSION: Peptide receptor-mediated radiotherapy via SSTR may provide a novel treatment strategy in carefully selected GIST patients with TKI-resistant tumors.

Inhomogeneous activity distribution of 177Lu-DOTA0-Tyr3-octreotate and effects on somatostatin receptor expression in human carcinoid GOT1 tumors in nude mice.

The aim of this study was to investigate the activity distribution in neouroendocrine tumors after diagnostic, or therapeutic, amounts of [(177)Lu-DOTA(0)-Tyr(3)]-octreotate and to investigate how the activity distribution influences the absorbed dose. Furthermore, the activity distribution of a second administration of radiolabeled octreotate was studied. Nude mice with subcutaneously grown human midgut carcinoid (GOT1) were injected intravenously with different amounts of (177)Lu-octreotate. At different time points thereafter (4 h to 13 days), a second injection of [(111)In-DOTA(0)-Tyr(3)]-octreotate was given to estimate the somatostatin receptor (sstr) expression. The activity distribution in the tumors was then determined. Monte Carlo simulations with PENELOPE were performed for dosimetry. Fifty-one out of 58 investigated tumors showed a lower activity concentration in the peripheral part than in the central part of the tumor. The amount of activity injected, or time after administration, did neither influence the relative activity nor the sstr distribution in the tumor. After an initial down-regulation (at 4-24 h), there was an up-regulation of sstr (1.5-2 times, at 7-14 days). Monte Carlo simulations demonstrated an inhomogeneous absorbed dose distribution in the tumor using (177)Lu, with twice as high absorbed dose centrally than peripherally. The high activity concentration centrally and the up-regulation of sstr demonstrated will facilitate fractionated therapy using radiolabeled somatostatin analogues if similar results will be obtained also in patients. The inhomogeneous activity distribution in the tumor has to be taken into account when the absorbed dose distribution in tumor is calculated.

Prevalence of germline mutations in patients with pheochromocytoma or abdominal paraganglioma and sporadic presentation: a population-based study in Western Sweden.

BACKGROUND: Germline mutations in the susceptibility genes RET, SDHB, SDHD, and VHL have been reported in 7.5-24% of patients with pheochromocytoma (Pheo) or paraganglioma (PGL) and sporadic presentation. The purpose of the present study was to establish population-based data on the frequency of germline mutations in patients with apparently sporadic Pheo or abdominal PGL in Western Sweden. METHODS: From the Swedish National Cancer Registry, all patients with Pheo or PGL in Western Sweden (population 1.72 million) registered between 1958 and 2009 were identified (n = 256). Patients were characterized using register data, hospital records, and clinical interviews. All living patients with Pheo or abdominal PGL and sporadic presentation (n = 81) were invited to genetic screening; 71 patients accepted. Germline mutations were investigated by using direct sequencing for point mutations in RET, SDHB, SDHD, and VHL, and multiplex ligation-dependent probe amplification for gross deletions in SDHB, SDHC, SDHD, and VHL. Plasma or urinary metanephrines and/or urinary catecholamines were used for biochemical follow-up. RESULTS: The prevalence of germline mutations was 5.6%. Mutations were only seen in RET (n = 1) and SDHB (n = 3). Notably, in the patients with SDHB mutations, no malignant phenotype was observed during a mean follow-up of 23.3 years. CONCLUSIONS: The frequency of germline mutations in patients with apparently sporadic Pheo and abdominal PGL in Western Sweden was lower than in previous studies. Variations in reported frequencies of germline mutations in patients with clinically sporadic Pheo/PGL may reflect geographical differences or patient selection.

31P MR spectroscopy to evaluate the efficacy of hepatic artery embolization in the treatment of neuroendocrine liver metastases.

BACKGROUND: It is common to treat patients with metastatic disease from gastrointestinal neuroendocrine (NE) tumors with surgical reduction to prolong survival. This can be combined with hepatic arterial embolization (HAE) and medical treatment to reduce hormonal symptoms. Today there are no rapid and reliable methods to evaluate the efficacy of HAE in the treatment of neuroendocrine liver metastasis. PURPOSE: To investigate metabolic changes in hepatic metastases of NE tumors following HAE, and to establish if there are any early spectral patterns that might indicate therapeutic efficacy based on in vivo (31)P MRS data. MATERIAL AND METHODS: Volume selective (31)P MRS was used to study 11 patients with disseminated NE tumors with regional lymph nodes and bilobar liver metastases. Measurements were performed before and 1 and 3 days after HAE. RESULTS: Non-responders had significantly higher PME/Pi and αNTP/ΣNTP ratios than the responders before HAE (P < 0.05). Three days after HAE, non-responders still had significantly higher αNTP/ΣNTP than the responders did (P < 0.05). We also observed trends for increased PME ratios 3 days after HAE, decreased ATP-levels, and liberated Pi in responders. CONCLUSION: This (31)P-MRS study showed significant differences in PME/Pi and αNTP/ΣP ratios between responders and non-responders on the day before HAE, which is an interesting finding that may reflect intrinsic properties of the tumor tissue. We also observed trends for cell membrane renewal and increased energy consumption in responders after HAE. These results demonstrate potentials for (31)P-MRS to predict individual responsiveness prior to HAE.

Expression profiling of GIST: CD133 is associated with KIT exon 11 mutations, gastric location and poor prognosis.

In gastrointestinal stromal tumors (GISTs), KIT exon 11 deletions are associated with poor prognosis. The aim of this study was to determine the gene expression profiles of GISTs carrying KIT exon 11 deletions and to identify genes associated with poor prognosis. Expression profiling was performed on nine tumors with KIT exon 11 deletions and 7 without KIT exon 11 mutations using oligonucleotide microarrays. In addition, gene expression profiles for 35 GISTs were analyzed by meta-analysis. Expression of CD133 (prominin-1) protein was examined by tissue microarray (TMA) analysis of 204 GISTs from a population-based study in western Sweden. Survival analysis was performed on patients subjected to R0 resection (n=180) using the Cox proportional hazards model. Gene expression profiling, meta-analysis, and qPCR showed up regulation of CD133 in GISTs carrying KIT exon 11 deletions. Immunohistochemical analysis on TMA confirmed CD133 expression in 28% of all tumors. CD133 positivity was more frequent in gastric GISTs (48%) than in small intestinal GISTs (4%). CD133 positivity was also more frequent in GISTs with KIT exon 11 mutations (41%) than in tumors with mutations in KIT exon 9, platelet-derived growth factor receptor α (PDGFRA), or wild-type tumors (0-17%). Univariate survival analysis showed a significant correlation between the presence of CD133 protein and shorter overall survival (hazard ratio=2.23, p=0.027). Multivariate analysis showed that CD133 provided additional information on patient survival compared to age, sex, National Institutes of Health (NIH) risk group and mutational status. CD133 is expressed in a subset of predominantly gastric GISTs with KIT exon 11 mutations and poor prognosis.

Downsizing treatment with tyrosine kinase inhibitors in patients with advanced gastrointestinal stromal tumors improved resectability.

BACKGROUND: Gastrointestinal stromal tumors (GISTs) express the receptor tyrosine kinase KIT. Most GISTs have mutations in the KIT or PDGFRA gene, causing activation of tyrosine kinase. Imatinib, a tyrosine kinase inhibitor (TKI), is the first-line palliative treatment for advanced GISTs. Sunitinib was introduced for patients with mutations not responsive to imatinib. The aim was to compare the survival of patients with high-risk resected GISTs treated with TKI prior to surgery with historical controls and to determine if organ-preserving surgery was facilitated. METHODS: Ten high-risk GIST-patients had downsizing/adjuvant TKI treatment: nine with imatinib and one with sunitinib. The patients were matched with historical controls (n = 89) treated with surgery alone, from our population-based series (n = 259). Mutational analysis of KIT and PDGFRA was performed in all cases. The progression-free survival was calculated. RESULTS: The primary tumors decreased in mean diameter from 20.4 cm to 10.5 cm on downsizing imatinib. Four patients with R0 resection and a period of adjuvant imatinib had no recurrences versus 67% in the historical control group. Four patients with residual liver metastases have stable disease on continuous imatinib treatment after surgery. One patient has undergone reoperation with liver resection. The downsizing treatment led to organ-preserving surgery in nine patients and improved preoperative nutritional status in one patient. CONCLUSIONS: Downsizing TKI is recommended for patients with bulky tumors with invasion of adjacent organs. Sunitinib can be used for patients in case of imatinib resistance (e.g., wild-type GISTs), underlining the importance of mutational analysis for optimal surgical planning.

[177Lu-DOTA 0-Tyr 3]-octreotate treatment in patients with disseminated gastroenteropancreatic neuroendocrine tumors: the value of measuring absorbed dose to the kidney.

BACKGROUND: Peptide receptor radiation therapy (PRRT) using [(177)Lu-DOTA(0)-Tyr(3)]-octreotate is a new, promising option for treatment of disseminated gastroenteropancreatic neuroendocrine tumors (GEPNETs). METHODS: During 2006-2008, 26 patients with disseminated GEPNETs were treated with (177)Lu-octreotate. Radiologic response (RECIST), biochemical response [plasma chromogranin-A (P-CgA)], hematologic toxicity [Common Toxicity Criteria (CTC)], absorbed dose to the kidneys (conjugate view method), and glomerular filtration rate (GFR) were analyzed. RESULTS: (177)Lu-octreotate (8 GBq) was given one to five times (median = 3) with a 6-week interval between each. Sixteen of the 26 patients were evaluated radiologically; 6 (38%) had partial response (PR), 8 (50%) had stable disease (SD), and 2 (13%) had progressive disease (PD). Seventeen of the 26 patients were evaluated biochemically; 6 (35%) showed a >or=30% decrease, 8 (47%) showed a >or=20% increase, and 3 (18%) showed neither a >or=30% decrease nor a >or=20% increase. The mean absorbed dose to the kidneys was 24 Gy. With a dose limit of 27 Gy to the kidneys, 10 patients did not receive the planned four treatments, while four patients had the potential to receive additional treatment. A significant reduction (p = 0.0013) of GFR was observed at follow-up. Three patients experienced CTC grade 3 hematologic toxicity. CONCLUSIONS: By using the absorbed dose to the kidneys as a limiting factor, treatment with (177)Lu-octreotate can be individualized, e.g., overtreatment can be avoided and patients with the potential to receive additional treatment can be identified. Further studies are needed to define tolerance doses to the kidneys so that treatment can be optimized.

Quantitative analysis of tumor growth rate and changes in tumor marker level: specific growth rate versus doubling time.

BACKGROUND: Doubling time (DT) of tumor volume has been widely used to estimate the growth rate of tumors. However, DT gives incorrect estimates of the average growth rate of tumors when the uncertainty of growth rate is considerable. Specific growth rate (SGR) is less affected by uncertainties and is a more relevant parameter. Optimized imaging techniques and prolonged interval between observations can reduce the uncertainty of growth rate estimation. DT is also used for defining changes in tumor marker level. The aim of this study was to compare DT and SGR as measures of growth rate when the uncertainty is negligible. METHODS: Mathematical analysis and computer simulations were carried out assuming no uncertainty of growth rate estimation. Data from two previously published clinical studies were assessed by both variables. RESULTS: Due to the non-linear relationship between DT and SGR, using these variables does not give similar results. The variation of DT is not uniformly indicating variations of the growth rate. DT largely overestimates the difference in growth rate of slowly growing tumors and underestimates the difference in growth rate of rapidly growing tumors. On the other hand, SGR uniformly indicates the difference between growth rates throughout all ranges. Quantitative analysis of clinical observations can lead to contradictory results depending on the variable used for growth rate. CONCLUSION: The growth rate of tumor volume should be expressed by SGR, or percentage increase per unit time, regardless of the level of the uncertainty of growth rate estimation. This conclusion is also valid for changes in tumor marker level, whether it is correlated with the growth rate of tumor volume or not.

Specific growth rate versus doubling time for quantitative characterization of tumor growth rate.

Doubling time (DT) is widely used for quantification of tumor growth rate. DT is usually determined from two volume estimations with measurement time intervals comparable with or shorter than DT. Clinical data show that the frequency distribution of DT in patients is positively skewed, with some very long DT values compared with the average DT. Growth rate can also be quantified using specific growth rate (SGR; %/d), equal to ln2/DT. The aim of this work was to compare DT and SGR as growth rate variables. Growth rate calculations were computer simulated for a tumor with DT of 100 days, measurement time interval of 1 to 200 days, and volume estimation uncertainty of 5% to 20%. Growth rate variables were determined and compared for previously published clinical data. The study showed that DT is not a suitable variable for tumor growth rate because (a) for short measurement time intervals, or high volume uncertainties, mean DT can either overestimate or underestimate the average growth rate; (b) DT is not defined if the consecutively estimated volumes are equal; and (c) the asymmetrical frequency distribution of DT makes it unsuitable for common statistical testing. In contrast, mean SGR and its equivalent DT give the correct values for average growth rate, SGR is defined for all tumor volume changes, and it has a symmetrical frequency distribution. SGR is also more accurate to use when discussing, for example, growth fraction, cell loss rate, and growth rate heterogeneities within the tumor. SGR should thus be used, instead of DT, to quantify tumor growth rate.

Amyloid precursor-like protein 1 is differentially upregulated in neuroendocrine tumours of the gastrointestinal tract.

We have examined the global gene expression profile of small intestinal carcinoids by microarray analysis. High expression of a number of genes was found including amyloid precursor-like protein 1 (APLP1). Quantitative real-time PCR and western blot analysis demonstrated higher expression of APLP1 in carcinoid metastases relative to primary tumours indicating a role of APLP1 in tumour dissemination. Tissue microarray analysis of gastroentero-pancreatic tumours demonstrated a high frequency of APLP1 expression and a low frequency of APLP2 expression in neuroendocrine (NE) tumours when compared with non-NE tumours at the same sites. Meta-analysis of gene expression data from a large number of tumours outside the gastrointestinal tract confirmed a correlation between APLP1 expression and NE phenotype where high expression of APLP1 was accompanied by downregulation of APLP2 in NE tumours. Cellular localization of APLP1, APLP2 and amyloid precursor protein (APP) in carcinoid cells (GOT1) by confocal microscopy demonstrated partial co-localization with synaptophysin. This suggests that the APP family of proteins is transported to the cell membrane by synaptic microvesicles and that they may influence tumour cell adhesion and invasiveness. We conclude that APLP1 is differentially upregulated in gastrointestinal NE tumours and that APLP1 may be important for the dissemination of small intestinal carcinoids. Identification of APLP1 in NE tumours offers a novel target for treatment and may also serve as a tumour-specific marker.

Comparison of [177Lu-DOTA0,Tyr3]-octreotate and [177Lu-DOTA0,Tyr3]-octreotide for receptor-mediated radiation therapy of the xenografted human midgut carcinoid tumor GOT1.

The aim of this study was to compare the tumor uptake versus time and the tumor response in nude mice transplanted with a human midgut carcinoid (GOT1), when treated with either [(177)Lu-DOTA(0),Tyr(3)]-octreotide or [(177)Lu-DOTA(0),Tyr(3)]-octreotate and to evaluate if plasma chromogranin A (P-CgA) was a reliable marker of tumor response. The tumor uptake and retention of activity of a single intravenous (i.v.) dose (15 MBq) of [(177)Lu-DOTA(0),Tyr(3)]-octreotate or [(177)Lu-DOTA(0),Tyr(3)]-octreotide were compared in nude mice xenografted with GOT1. The activity concentration 24 hours after injection was significantly higher in animals given [(177)Lu-DOTA(0),Tyr(3)]-octreotate versus [(177)Lu-DOTA(0),Tyr(3)]-octreotide (16%+/-1.4% of injected activity per gram [%IA/g] vs. 8.1%+/-2.1% IA/g, mean +/- standard error of the mean) (p=0.00061). The mean absorbed dose was higher in animals given [(177)Lu-DOTA(0),Tyr(3)]-octreotate (46+/-4.3 vs. 17 +/- 3.4 Gy). The reduction of tumor volume was accordingly more prominent in animals given [(177)Lu-DOTA(0),Tyr(3)]-octreotate than in animals given [(177)Lu-DOTA(0),Tyr(3)]-octreotide (p=0.003). The mean tumor volume for animals given [(177)Lu-DOTA(0),Tyr(3)]-octreotate was reduced to 3% of its initial value. P-CgA values were strongly correlated with tumor volume. Octreotate seems to be a more suitable somatostatin analog than octreotide for receptor-mediated radiation therapy. P-CgA is a simple, accurate method for the estimation of tumor response in this animal model.

Can the early reduction of tumour markers predict outcome in surgically treated sporadic medullary thyroid carcinoma?

BACKGROUND AND AIMS: Patients with sporadic medullary thyroid carcinoma (MTC) have a variable clinical course. Our aim was to analyse the reduction of tumour markers after thyroidectomy with meticulous dissection and relate it to clinical outcome. MATERIALS AND METHODS: Twenty consecutive patients with palpable sporadic MTC underwent thyroidectomy with central and uni- or bilateral modified radical neck dissection; three were subjected to mediastinal dissection. Basal (b-) and stimulated (s-) calcitonin (CT) and carcinoembryonic antigen (CEA)-levels were measured before and 6-8 weeks after primary surgery, and the reduction of these tumour markers was determined. RESULTS: Median CT (b- and s-) were markedly reduced after surgery (98.5% and 99.1%, respectively), and CEA decreased 11 times. CT (b-) fell >99% in seven patients after surgery; in these and four additional patients, CT (s-) showed a similar reduction. During follow-up (median 52.5 months), two patients (stages IV B and C) died of MTC; they had <95% reduction of CT. Four patients (stage IV A) are alive with verified metastases. Eight patients (one stage III, seven stage IV A) are alive with hypercalcitoninemia. Five stages I-III patients and one stage IV A patient are disease-free. CONCLUSIONS: Thyroidectomy and meticulous dissection caused a pronounced reduction of tumour markers. A postoperative reduction of CT (s-) >or=97% seems to be associated with less aggressive clinical course, while CEA had lower predictive value.

Gastrointestinal stromal tumors regularly express synaptic vesicle proteins: evidence of a neuroendocrine phenotype.

Gastrointestinal stromal tumors (GISTs) are thought to originate from the interstitial cells of Cajal, which share many properties with neurons of the gastrointestinal tract. Recently, we demonstrated expression of the hormone ghrelin in GIST. The aim of the present study was therefore to evaluate a possible neuroendocrine phenotype of GIST. Specimens from 41 GISTs were examined for the expression of 12 different synaptic vesicle proteins. Expression of synaptic-like microvesicle proteins, e.g., Synaptic vesicle protein 2 (SV2), synaptobrevin, synapsin 1, and amphiphysin was demonstrated in a majority of GISTs by immunohistochemistry, western blotting, and quantitative reversetranscriptase PCR. One-third of the tumors also expressed the large dense core vesicle protein vesicular monoamine transporter 1. Presence of microvesicles and dense core vesicles in GIST was confirmed by electron microscopy. The expression of synaptic-like microvesicle proteins in GIST was not related to risk profile or to KIT/platelet derived growth factor alpha (PDGFRA) mutational status. Thus, GISTs regularly express a subset of synaptic-like microvesicle proteins necessary for the regulated secretion of neurotransmitters and hormones. Expression of synaptic-like micro-vesicle proteins, ghrelin and peptide hormone receptors in GIST indicate a neuroendocrine phenotype and suggest novel possibilities to treat therapy-resistant GIST.

A transplantable human medullary thyroid carcinoma as a model for RET tyrosine kinase-driven tumorigenesis.

Hereditary medullary thyroid carcinoma (MTC) is caused by germline mutations in the RET proto-oncogene, resulting in constitutive activation of the RET tyrosine kinase. A substantial proportion of sporadic MTCs also have RET mutations, making the RET tyrosine kinase a potential therapeutic target in MTC. We have established a transplantable MTC in nude mice from a sporadic human MTC carrying a RET C634R mutation. Transplanted tumors had an exponential growth rate with an approximate doubling time of about 3 weeks, and expressed a neuroendocrine phenotype characteristic of MTC, e.g., expression of calcitonin, chromogranin A (CgA), synaptophysin, synaptic vesicle protein 2 (SV2), vesicular monoamine transporter-1 and -2, carcinoembryonic antigen, cytokeratin 8/18, epithelial cadherin, and neural cell adhesion molecule. Plasma calcitonin and CgA levels were elevated in tumor-bearing mice and correlated with tumor size. Cytogenetic analysis, including spectral karyotyping, confirmed the human origin of the xenografted tumors and demonstrated an abnormal, near triploid karyotype. Treatment of tumor-bearing nude mice with the tyrosine kinase inhibitor ZD6474, which specifically inhibits RET, epidermal growth factor receptor (EGFR), and vascular endothelium growth factor receptor (VEGFR) tyrosine kinases, resulted in a dose-dependent inhibition of tumor growth. Oral ZD6474 given once daily (250 mg/kg, 5 days/week) reduced tumor volume to 11% when compared with controls after 4 weeks. Our results show that this transplantable MTC, designated GOT2, represents a novel and useful model for studies of MTC and RET tyrosine kinase-dependent tumor growth.

Effects of treatment with (177)Lu-DOTA-Tyr(3)-octreotate on uptake of subsequent injection in carcinoid-bearing nude mice.

PURPOSE: The aim of this study was to analyze the effect therapeutic injections of (177)Lu-DOTA(0)-Tyr(3)]-octreotate (DOTATATE) had on the tumor uptake of a subsequent injection with (111)In-DOTATATE in GOT1-bearing nude mice. METHODS AND MATERIALS: Nude mice, xenografted with the human midgut carcinoid, GOT1, were first intravenously injected with a curative (30 MBq) or a suboptimal (7.5 MBq) amount of (177)Lu-DOTATATE. At various intervals thereafter (4-13 days), a second injection with (111)In-DOTATATE (0.5 MBq) was given. One (1) day after the second injection, the animals were sacrificed, tumor tissues collected, the tumor (111)In and (177)Lu activity concentration determined, and tumor regression/cell density was recorded. RESULTS: In animals given curative amounts, the uptake of (111)In was lower than in untreated animals. On the other hand, a second late injection (3-13 days) after suboptimal amounts resulted in a twofold higher tumor activity concentration versus untreated animals. When the uptake of the curative injection was corrected for tumor cell density, which decreased from 66% to 4% over 2 weeks, an enhanced uptake per tumor cell was observed. The curative and suboptimal amounts resulted in a different uptake and retention of (177)Lu in tumors. The suboptimal amount resulted in a constant activity concentration, while the curative amount resulted in an increased activity concentration over time. CONCLUSIONS: Our results, as presented in this paper, describe how the second injection in a fractionation protocol will be affected by the first therapeutic amount. This new information might be useful in the optimization of radionuclide therapy.

Gastrointestinal stromal tumors express the orexigen ghrelin.

Expression of the neuroendocrine marker synaptic vesicle protein 2 (SV2) has been reported in a few cases of gastrointestinal stromal tumors (GISTs). The goal of the present study was to assess the relevance of this finding and identify a possible hormone production in these tumors. We chose to study the orexigen ghrelin and its receptor, since these patients are seldom cachexic, even in advanced disease stages. We investigated ghrelin expression by means of immunohistochemistry on frozen or paraffin-embedded sections from 22 GISTs from a well-characterized patient material. Expression of the growth hormone secretagogue receptor, the ghrelin receptor, was investigated in a subset of lesions. In six tumors, mRNA levels of ghrelin, the ghrelin receptor, and SV2 were analyzed by real-time quantitative PCR. Totally 17 out of 22 tumors showed immunoreactivity for ghrelin. Five out of ten tumors were immunoreactive for the ghrelin receptor, and all of these co-expressed ghrelin. All tumors expressed ghrelin, ghrelin receptor, and SV2 mRNA. GISTs frequently express SV2, ghrelin, and its receptor, indicating the presence of autocrine/paracrine loops.