High gastrin and cholecystokinin (CCK) gene expression in human neuronal, renal, and myogenic stem cell tumors: comparison with CCK-A and CCK-B receptor contents

A stemness-based eleven-gene signature correlates with the clinical outcome of hepatocellular carcinoma

Background

Cumulative evidences have been implicated cancer stem cells in the tumor environment of hepatocellular carcinoma (HCC) cells, whereas the biological functions and prognostic significance of stemness related genes (SRGs) in HCC is still unclear.

Methods

Molecular subtypes were identified by cumulative distribution function (CDF) clustering on 207 prognostic SRGs. The overall survival (OS) predictive gene signature was developed, internally and externally validated based on HCC datasets including The Cancer Genome Atlas (TCGA), GEO and ICGC datasets. Hub genes were identified in molecular subtypes by protein-protein interaction (PPI) network analysis, and then enrolled for determination of prognostic genes. Univariate, LASSO and multivariate Cox regression analyses were performed to assess prognostic genes and construct the prognostic gene signature. Time-dependent receiver operating characteristic (ROC) curve, Kaplan-Meier curve and nomogram were used to assess the performance of the gene signature.

Results

We identified four molecular subtypes, among which the C2 subtype showed the highest SRGs expression levels and proportions of immune cells, whereas the worst OS; the C1 subtype showed the lowest SRGs expression levels and was associated with most favorable OS. Next, we identified 11 prognostic genes (CDX2, PON1, ADH4, RBP2, LCAT, GAL, LPA, CYP19A1, GAST, SST and UGT1A8) and then constructed a prognostic 11-gene module and validated its robustness in all three datasets. Moreover, by univariate and multivariate Cox regression, we confirmed the independent prognostic ability of the 11-gene module for patients with HCC. In addition, calibration analysis plots indicated the excellent predictive performance of the prognostic nomogram constructed based on the 11-gene signature.

Conclusions

Findings in the present study shed new light on the role of stemness related genes within HCC, and the established 11-SRG signature can be utilized as a novel prognostic marker for survival prognostication in patients with HCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08351-0.

Second primary neoplasms in patients with lung and gastroenteropancreatic neuroendocrine neoplasms: Data from a retrospective multi-centric study

BACKGROUND

Patients with sporadic neuroendocrine neoplasms may exhibit a higher risk of a second primary tumor than the general population.

AIM

This study aimed to analyze the occurrence of second primary malignancies.

METHODS

A retrospective cohort of 2757 patients with sporadic lung and gastro-entero-pancreatic neuroendocrine neoplasms, managed at eight Italian tertiary referral Centers, was included.

RESULTS

Between 2000 and 2019, a second primary malignancy was observed in 271 (9.8%) neuroendocrine neoplasms patients with 32 developing a third tumor. There were 135 (49.8%) females and the median age was 64 years. The most frequent locations of the second tumors were breast (18.8%), prostate (12.5%), colon (9.6%), blood tumors (8.5%), and lung (7.7%). The second primary tumor was synchronous in 19.2% of cases, metachronous in 43.2%, and previous in 37.6%. As concerned the neuroendocrine neoplasms, the 5- and 10-year survival rates were 87.8% and 74.4%, respectively. PFS for patients with a second primary malignancy was shorter than for patients without a second primary malignancy. Death was mainly related to neuroendocrine neoplasms.

CONCLUSION

In NEN patients the prevalence of second primary malignancies was not negligible, suggesting a possible neoplastic susceptibility. Overall survival was not affected by the occurrence of a second primary malignancy.

Occurrence of second primary malignancies in patients with neuroendocrine tumors of the digestive tract: A case report

RATIONALE

There is an association between the presence of neuroendocrine neoplasms and incremented risk to develop second primary malignancies. This risk is estimated to be 17%. The most common secondary neoplasms were found in the Gastrointestinal and Genitourinary tracts.

PATIENT CONCERNS

A 74-year-old Caucasian patient with melaena came to our observation in June 2015. The Esophago-gastro-duodenoscopy exam found a polypoid formation in the duodenal bulb. Histopathological examination showed a well-differentiated neuroendocrine neoplasm (G1).

DIAGNOSIS

During the follow up for the neuroendocrine neoplasm, a CT scan was performed in August 2016 describing infiltration of the right renal sinus and the third proximal ureter segment with heterogeneous enhancement of vascular structure. An US-guided biopsy was conclusive for a Diffuse Large B Cell Lymphoma. In October 2016, a colonoscopy showed a neoplastic lesion at 20 cm from the anal orifice. The Histology exam was positive for an adenocarcinoma with a desmoplastic stroma infiltration.

INTERVENTIONS

In November 2016, the patient underwent a left hemicolectomy: the pathologic staging described a G2 adenocarcinoma pT3N1b. In May 2018, the Octreotide scan was negative. In the same month, the patient started a treatment based on 6 cycles of Rituximab, Oxaliplatin, and Capecitabine due to the persistence of lymphomatous disease and hepatic metastases. In July 2018, other 3 cycles of the same treatment were scheduled.

OUTCOMES

In January 2019, due to an increase in liver metastases' size, it was decided to start a new regimen for the colon cancer with FOLFIRI+Cetuximab. The patient is still in treatment with this regimen in April 2019.

LESSONS

The risk of a second primary tumor is increased among patients older than 70. Therefore, it is necessary to follow them using total body CT scan and endoscopic techniques of gastrointestinal and genitourinary tracts, not only for the evaluation of the neuroendocrine tumor but also for the higher risk to develop other neoplastic diseases.

Potential approaches to the treatment of Ewing's sarcoma

Ewing’s sarcoma (ES) is a highly aggressive and metastatic tumor in children and young adults caused by a chromosomal fusion between the Ewing sarcoma breakpoint region 1 (EWSR1) gene and the transcription factor FLI1 gene. ES is managed with standard treatments, including chemotherapy, surgery and radiation. Although the 5-year survival rate for primary ES has improved, the survival rate for ES patients with metastases or recurrence remains low. Several novel molecular targets in ES have recently been identified and investigated in preclinical and clinical settings, and targeting the function of receptor tyrosine kinases (RTKs), the fusion protein EWS-FLI1 and mTOR has shown promise. There has also been increasing interest in the immune responses of ES patients. Immunotherapies using T cells, NK cells, cancer vaccines and monoclonal antibodies have been considered for ES, especially for recurrent patients. Because understanding the pathogenesis of ES is extremely important for the development of novel treatments, this review focuses on the mechanisms and functions of targeted therapies and immunotherapies in ES. It is anticipated that integrating the knowledge obtained from basic research and translational and clinical studies will lead to the development of novel therapeutic strategies for the treatment of ES.

EWS/FLI1 Target Genes and Therapeutic Opportunities in Ewing Sarcoma

Ewing sarcoma is an aggressive bone malignancy that affect children and young adults. Ewing sarcoma is the second most common primary bone malignancy in pediatric patients. Although significant progress has been made in the treatment of Ewing sarcoma since it was first described in the 1920s, in the last decade survival rates have remained unacceptably invariable, thus pointing to the need for new approaches centered in the molecular basis of the disease. Ewing sarcoma driving mutation, EWS–FLI1, which results from a chromosomal translocation, encodes an aberrant transcription factor. Since its first characterization in 1990s, many molecular targets have been described to be regulated by this chimeric transcription factor. Their contribution to orchestrate Ewing sarcoma phenotype has been reported over the last decades. In this work, we will focus on the description of a selection of EWS/FLI1 targets, their functional role, and their potential clinical relevance. We will also discuss their role in other types of cancer as well as the need for further studies to be performed in order to achieve a broader understanding of their particular contribution to Ewing sarcoma development.

Stimulation of proliferation in the colorectal mucosa by gastrin precursors is blocked by desferrioxamine

Precursors of the peptide hormone gastrin stimulate proliferation in the colorectal mucosa and promote the development of colorectal carcinoma. Gastrins bind two ferric ions selectively and with high affinity, and the biological activity of glycine-extended gastrin (Ggly) in vitro is dependent on the presence of ferric ions. The aim of the present study was to determine whether or not iron is required for biological activity of progastrin and Ggly in vivo. Rats that had undergone a colostomy were infused with Ggly, and proliferation was measured in the defunctioned rectal mucosa. Proliferation was also measured in the colonic mucosa of hGAS and MTI-Ggly mice, which, by definition, overexpress progastrin and Ggly, respectively. The requirement for iron was assessed by thrice-weekly injection of the chelating agent desferrioxamine (DFO). The proliferation index in the defunctioned rectal mucosa was significantly increased in the Ggly-infused rats, and the increase was significantly reduced after treatment with DFO. Treatment with DFO significantly reduced the crypt height and proliferation index in the colonic mucosa of hGAS and MTI-Ggly mice but had no effect on the same variables in wild-type mice. These observations are consistent with the hypothesis that the biological activity of progastrin and Ggly in vivo is dependent on the presence of ferric ions and further suggest that chelating agents may block the stimulatory effects of gastrin precursors in the development of colorectal carcinoma.

Synthesis and in vitro characterization of radioiodinatable benzodiazepines selective for type 1 and type 2 cholecystokinin receptors

Radiolabeled antagonists of specific peptide receptors identify a higher number of receptor binding sites than agonists and may thus be preferable for in vivo tumor targeting. In this study, two novel radioiodinated 1,4-benzodiazepines, (S)-1-(3-iodophenyl)-3-(1-methyl-2-oxo-5-phenyl-2,3-dihydro-1H-benzo[e][1,4]diazepin-3-yl)urea (9) and (R)-1-(3-iodophenyl)-3-(1-methyl-2-oxo-5-phenyl-2,3-dihydro-1H-benzo[e][1,4]diazepin-3-yl)urea (7), were developed. They were characterized in vitro as high affinity selective antagonists at cholecystokinin types 1 and 2 (CCK(1) and CCK(2)) receptors using receptor binding, calcium mobilization, and internalization studies. Their binding to human tumor tissues was assessed with in vitro receptor autoradiography and compared with an established peptidic CCK agonist radioligand. The (125)I-labeled CCK(1) receptor-selective compound 9 often revealed a substantially higher amount of CCK(1) receptor binding sites in tumors than the agonist (125)I-CCK. Conversely, the radioiodinated CCK(2) receptor-selective compound 7 showed generally weaker tumor binding than (125)I-CCK. In conclusion, compound 9 is an excellent radioiodinated nonpeptidic antagonist ligand for direct and selective labeling of CCK(1) receptors in vitro. Moreover, it represents a suitable candidate to test antagonist binding to CCK(1) receptor-expressing tumors in vivo.

High expression of neuropeptide Y1 receptors in ewing sarcoma tumors

PURPOSE

Peptide receptors are frequently overexpressed in human tumors, allowing receptor-targeted scintigraphic imaging and therapy with radiolabeled peptide analogues. Neuropeptide Y (NPY) receptors are new candidates for these applications, based on their high expression in specific cancers. Because NPY receptors are expressed in selected sarcoma cell lines and because novel treatment options are needed for sarcomas, this study assessed the NPY receptor in primary human sarcomas.

EXPERIMENTAL DESIGN

Tumor tissues of 88 cases, including Ewing sarcoma family of tumors (ESFT), synovial sarcomas, osteosarcomas, chondrosarcomas, liposarcomas, angiosarcomas, rhabdomyosarcomas, leiomyosarcomas, and desmoid tumors, were investigated for NPY receptor protein with in vitro receptor autoradiography using (125)I-labeled NPY receptor ligands and for NPY receptor mRNA expression with in situ hybridization.

RESULTS

ESFT expressed the NPY receptor subtype Y1 on tumor cells in remarkably high incidence (84%) and density (mean, 5,314 dpm/mg tissue). Likewise, synovial sarcomas expressed Y1 on tumor cells in high density (mean, 7,497 dpm/mg; incidence, 40%). The remaining tumors expressed NPY receptor subtypes Y1 or Y2 at lower levels. Moreover, many of the sarcomas showed Y1 expression on intratumoral blood vessels. In situ hybridization for Y1 mRNA confirmed the autoradiography results.

CONCLUSIONS

NPY receptors are novel molecular markers for human sarcomas. Y1 may inhibit growth of specific sarcomas, as previously shown in an in vivo mouse model of human ESFT. The high Y1 expression on tumor cells of ESFT and synovial sarcomas and on blood vessels in many other sarcomas represents an attractive basis for an in vivo tumor targeting.

Immunohistochemical examination of gastrin, gastrin precursors, and gastrin/CCK-2 receptor in human esophageal squamous cell carcinomas

A promoting effect of gastrin on stimulating Barrett's oesophagus proliferation has been demonstrated, but whether it plays a regulating role for esophageal squamous cell carcinoma (ESCC) to date has not been fully investigated. The aim of this study is to examine the expressions of gastrin, gastrin precursors and gastrin/CCK-2 receptor in ESCC. Tissue specimen sections from 38 patients with ESSC obtained from a high incidence area of north China were assessed using immunohistochemistry for amidated gastrin, gastrin precursors (progastrin and glycine-extended gastrin) and gastrin/CCK-2 receptors. Their clinical histopathological significance was also analyzed. Of 38 ESCC, the immunoreactivities of gastrin, glycine-extended gastrin and progastrin were observed in 13.2% (5/38), 7.9% (3/38) and 23.68% (9/38) cases. The expression of progastrin was obviously higher than other gastrins, though not significantly (P > 0.05). In positive cases for gastrin or glycine-extended gastrin, the scores of positive tumor cell numbers were at a lower density (<10/abundant-distributed field). However, the scores of progastrin positive tumor cell density in five of nine positive cases were over 10/abundant-distributed field. The immunoreactivity of gastrin/CCK-2 receptor was also observed in 15.8% (6/38) ESCC cases. There was not significant correlation regarding immunohistochemical results with known histomorphological parameters i.e. gender, tumor location and TNM stages. Based on our current results, ESCC tumor cells could be a possible cellular source of gastrin precursors, which has been postulated to play a role in regulating the growth in some human tumor cells.

Expression of gastrin receptor in tumors and its application as a molecular target for cancer diagnosis and therapy

Gastrin is widely distributed in gastrointestinal tract and pancreatic tissues, and it plays important roles in the modulation of physiological functions and pathogenic mechanism of some diseases. Recent studies showed that gastrin might promote the pathogenesis and growth of tumors, especially digestive tumors such as gastric cancer and colorectal cancer. The biological effect of gastrin is mainly mediated by cholecystokinin (CCK) receptors. Gastrin mRNA has been found in CCK-receptor positive small-cell lung carcinoma, breast cancer, ovarian cancer and cancer stem cells of various origins and it may serve as the indicator of self-secretive regulation. The tumors with over-expressed gastin receptor can be diagnosed and treated by radiolabelling or linking to the cytotoxic agents with gastin peptide and analogs, and scintigraphy was used to visualize the image in vivo.

Cholecystokinin and gastrin receptors

Cholecystokinin and gastrin receptors (CCK1R and CCK2R) are G protein-coupled receptors that have been the subject of intensive research in the last 10 years with corresponding advances in the understanding of their functioning and physiology. In this review, we first describe general properties of the receptors, such as the different signaling pathways used to exert short- and long-term effects and the structural data that explain their binding properties, activation, and regulation. We then focus on peripheral cholecystokinin receptors by describing their tissue distribution and physiological actions. Finally, pathophysiological peripheral actions of cholecystokinin receptors and their relevance in clinical disorders are reviewed.

An open-label, multinational, multicenter study of G17DT vaccination combined with cisplatin and 5-fluorouracil in patients with untreated, advanced gastric or gastroesophageal cancer: the GC4 study

BACKGROUND

Gastrin hormone is trophic to in vitro gastric cancer, and the antigastrin antibodies (AGAs) are antiproliferative and antimetastatic. Human gastric cancers overexpress gastrin genes and receptors that react to gastrin's trophic effects. Immunogen G17DT elicits a specific and high-affinity AGA. The authors evaluated G17DT vaccination given with cisplatin plus 5-fluorouracil for the treatment gastric adenocarcinoma.

METHODS

In this multicenter, Phase II study, patients received G17DT vaccination intramuscularly on Weeks 1, 5, 9 and 25 and cisplatin plus 5-fluorouracil every 28 days. Eligible patients had untreated, metastatic, or unresectable gastric or gastroesophageal adenocarcinoma with near-normal organ function. The primary endpoint of the study was the over response rate (ORR), and secondary endpoints included overall survival (OS), safety, and the impact of successful vaccination on patient outcome.

RESULTS

In total, 103 patients were enrolled in 5 countries. Seven patients who were overdosed inadvertently with 5-fluorouracil (a major protocol violation) were removed from the analysis. The confirmed ORR was 30% in 79 patients who were evaluated for response. The median time-to-progression (TTP) was 5.4 months, and the median survival (MS) was 9.0 months (n = 96 patients). Sixty-five of 94 patients who were vaccinated (69%) had 2 consecutive AGA titers of > or =1 units (successfully vaccinated patients or immune-responders). The TTP was longer in immune-responders than in immune-nonresponders (P = .0005). Similarly, the MS was longer in immune-responders than in immune-nonresponders (10.3 months vs. 3.8 months; P < or =.0001). In a multivariate analysis, successful vaccination was an independent OS prognosticator (P = .0001). G17DT did not have an adverse effect on safety.

CONCLUSIONS

The results demonstrated that successful G17DT vaccination was correlated with longer TTP and MS. AGA response was an independent OS prognosticator. A Phase III evaluation of G17DT in gastric cancer is warranted.

Role of gastrointestinal hormones in neuroblastoma

As a neuroendocrine tumor, neuroblastoma expresses various gastrointestinal (GI) hormones, such as vasoactive intestinal peptide, gastrin-releasing peptide (GRP), neurotensin, and somatostatin, which exert diverse cellular functions in neuroblastoma. In particular, we have recently found that GRP and its cell surface receptor, GRP-R, are abundantly expressed in neuroblastomas. Moreover, more advanced-stage neuroblastomas demonstrated an increased level of GRP-R, suggesting an important role of GRP in aggressive tumor behavior. This review describes the role of several GI hormones commonly expressed in neuroblastoma and discusses in depth the mitogenic actions of GRP in neuroblastoma. In addition, the molecular mechanisms involved in the GRP-induced stimulation of neuroblastoma cell growth are discussed. Our study results demonstrate a role of GRP as an autocrine/paracrine growth factor and elucidate involvement of specific intracellular signaling, the phosphatidylinositol 3-kinase pathway, in the growth regulation of neuroblastoma.

Characterization of Gastrin-Induced Proangiogenic EffectsIn vivoin Orthotopic U373 Experimental Human Glioblastomas andIn vitroin Human Umbilical Vein Endothelial Cells

PURPOSE

This study aims to investigate the role of gastrin-17 (G17) on angiogenesis features in gliomas both in vitro and in vivo.

EXPERIMENTAL DESIGN

The influences of G17 and G17 receptor antagonists were characterized in vitro in terms of angiogenesis on human umbilical vein endothelial cell (HUVEC) tubulogenesis processes on Matrigel and in vivo with respect to U373 orthotopic glioma xenografts. The influence of phosphatidylinositol 3'-kinase, protein kinase C, and nuclear factor-kappaB inhibitors was characterized in vitro on G17-mediated HUVEC tubulogenesis. G17-mediated release of interleukin (IL)-8 from HUVECs and G17-induced modifications in nuclear factor-kappaB DNA binding activity were characterized by means of specific enzyme-linked immunosorbent assays. The influence of G17 on E- and P-selectin expression was determined by means of computer-assisted microscopy, whereas the influence of E- and P-selectin on HUVEC migration was approached by means of antisense oligonucleotides. The chemotactic influence of G17 and IL-8 on HUVEC migration was characterized by means of computer-assisted videomicroscopy with Dunn chambers.

RESULTS

Messenger RNAs for cholecystokinin (CCK)A, CCKB, and CCKC receptors were present in HUVECs and microvessels dissected from a human glioblastoma. Whereas G17 significantly increased the levels of angiogenesis in vivo in the U373 experimental glioma model and in vitro in the HUVECs, the CCKB receptor antagonist L365,260 significantly counteracted the G17-mediated proangiogenic effects. G17 chemoattracted HUVECs, whereas IL-8 failed to do so. IL-8 receptor alpha (CXCR1) and IL-8 receptor beta (CXCR2) mRNAs were not detected in these endothelial cells. Gastrin significantly (but only transiently) decreased the level of expression of E-selectin, but not P-selectin, whereas IL-8 increased the expression of E-selectin. Specific antisense oligonucleotides against E- and P-selectin significantly decreased HUVEC tubulogenesis processes in vitro on Matrigel.

CONCLUSIONS

The present study shows that gastrin has marked proangiogenic effects in vivo on experimental gliomas and in vitro on HUVECs. This effect depends in part on the level of E-selectin activation, but not on IL-8 expression/release by HUVECs.

Procholecystokinin as Marker of Human Ewing Sarcomas

PURPOSE

Ewing sarcoma is a rapidly growing mesenchymal tumor in young adults. Although it was shown previously to express the cholecystokinin (CCK) gene, it is unknown whether CCK gene expression is detectable at protein level in Ewing sarcoma tumor cell lines, in tumor tissue, and in plasma from Ewing sarcoma patients, and, if so, whether CCK peptides might play a role as tumor markers.

EXPERIMENTAL DESIGN

CCK gene expression was evaluated with in situ hybridization or reverse transcription-PCR in tumor tissue. CCK precursors and bioactive CCK were measured with specific RIAs in tumor tissue, in cell culture medium, and in plasma of Ewing sarcoma patients before and after chemotherapy as well as after tumor recurrence.

RESULTS

CCK mRNA was identified in 12 Ewing sarcoma biopsies sampled in two series and in four Ewing sarcoma cell lines but not in unrelated neoplasia. Immunoreactive proCCK was identified in the culturing medium of all Ewing sarcoma cell lines but not in the media from unrelated tumor cell lines. Moreover, in plasma from Ewing sarcoma patients, precursors and mature forms of CCK, in particular proCCK, were detected; several fold elevation of the total proCCK product was found in plasma from patients before treatment and after tumor recurrence, whereas successful chemotherapy reduced proCCK to basal concentrations. Plasma concentrations of proCCK paralleled the respective tumor size.

CONCLUSIONS

This is the first study that consistently documents an altered CCK metabolism in human cancer; Ewing sarcomas synthesize and secrete proCCK that can be identified in plasma as circulating tumor marker.

Peptide receptors as molecular targets for cancer diagnosis and therapy

During the past decade, proof of the principle that peptide receptors can be used successfully for in vivo targeting of human cancers has been provided. The molecular basis for targeting rests on the in vitro observation that peptide receptors can be expressed in large quantities in certain tumors. The clinical impact is at the diagnostic level: in vivo receptor scintigraphy uses radiolabeled peptides for the localization of tumors and their metastases. It is also at the therapeutic level: peptide receptor radiotherapy of tumors emerges as a serious treatment option. Peptides linked to cytotoxic agents are also considered for therapeutic applications. The use of nonradiolabeled, noncytotoxic peptide analogs for long-term antiproliferative treatment of tumors appears promising for only a few tumor types, whereas the symptomatic treatment of neuroendocrine tumors by somatostatin analogs is clearly successful. The present review summarizes and critically evaluates the in vitro data on peptide and peptide receptor expression in human cancers. These data are considered to be the molecular basis for peptide receptor targeting of tumors. The paradigmatic peptide somatostatin and its receptors are extensively reviewed in the light of in vivo targeting of neuroendocrine tumors. The role of the more recently described targeting peptides vasoactive intestinal peptide, gastrin-releasing peptide, and cholecystokinin/gastrin is discussed. Other emerging and promising peptides and their respective receptors, including neurotensin, substance P, and neuropeptide Y, are introduced. This information relates to established and potential clinical applications in oncology.

Improvement of pharmacokinetics of radioiodinated Tyr(3)-octreotide by conjugation with carbohydrates

Among a variety of other factors, the clearance kinetics and routes of excretion of radiopharmaceuticals are of crucial importance for early and high tumor/background ratios and thus signal intensity in diagnostic imaging by single photon emission tomography (SPECT) or positron emission tomography (PET). To overcome the unfavorable pharmacokinetics of radiohalogenated octreotide analogues, we evaluated three carbohydrated conjugates of Tyr(3)-octreotide (TOC). Glucose ([(125)I]Gluc-TOC), maltose ([(125)I]Malt-TOC), and maltotriose ([(125)I]Mtr-TOC) derivatives of [(125)I]TOC were synthesized via Maillard reaction and subsequent radioiodination. In cells transfected with sst1-sst5, I-Malt-TOC, and I-Mtr-TOC show sst-subtype binding profiles similar to I-TOC with high affinity for sst2. Comparative biodistribution studies 10, 30, and 60 min pi in nude mice bearing rat pancreatic tumor xenografts showed fast blood clearance for all glycosylated derivatives. Due to their markedly increased hydrophilicity, [(125)I]Gluc-TOC and [(125)I]Malt-TOC were mainly cleared via the kidneys, which led to a significant decrease in activity accumulation in liver and intestine (5.3 and 1.4 versus 10.6%ID/g for [(125)I]TOC in the liver, 1.7 and 1.0 versus 3.8%ID/g for [(125)I]TOC in the intestine 60 min pi). For all compounds, hydrophilicity and uptake in liver and intestines correlate. Uptake of the carbohydrate conjugates in the kidney was comparable. Compared to the parent compound, the accumulation of the carbohydrated compounds in sst-rich tissues (pancreas, adrenals) was increased by a factor of 1.5-3.5. While tumor uptake of [(125)I]TOC (6.7 +/- 2.6%ID/g), [(125)I]Malt-TOC (5.3 +/- 1.9%ID/g), and [(125)I]Mtr-TOC (4.9 +/- 2.2%ID/g) at 30 min postinjection was comparable, accumulation of [(125)I]Gluc-TOC was significantly increased (10.1 +/- 2.8%ID/g at 30 min pi). Somatostatin receptor specificity of tumor uptake was confirmed by pretreatment, competition, and displacement experiments in vivo using 0.8 mg TOC/kg and gamma-camera imaging. Glycosylation proved to be a powerful tool for the development of high affinity sst ligands with excellent excretion profiles and improved tumor accumulation.

Gastrointestinal carcinoid tumors and second primary malignancies

The development of second primary malignancies (SPM) in patients with gastrointestinal carcinoid tumors is a well-described phenomenon, with reported rates as high as 55%. There is a predilection for gastrointestinal and genitourinary adenocarcinomas, but a variety of other malignancies have been reported as well. The etiology of this malignant predisposition may be rooted in the tumorigenic properties of the various neuroendocrine peptides elaborated and secreted by neuroendocrine cells. Peptides such as secretin, gastrin, bombesin, cholecystokinin (CCK), and vasoactive intestinal peptide (VIP) are believed to promote the growth of tumor cells. As many as 30 peptides and amines identified in neuroendocrine cells may have similar properties. This review of the literature on carcinoid-associated second primary malignancies is accompanied by a case report of metastatic carcinoid identified during surgical exploration for a perforating colon adenocarcinoma.