Diagnostic, surgical and medical aspect of the midgut carcinoids

Primary versus secondary nature of mesenteric neuroendocrine tumours

Neuroendocrine tumours (NETs) are rare group of malignancy that originate from neuroendocrine cells present throughout the body. Most patients with NET first present with symptoms associated with metastasis, and up to 20% of patients have unknown primary site of tumour. Most common metastatic sites for small intestine NETs (SI-NETs) are the locoregional lymph nodes and liver. Although mesenteric metastasis through direct extension or lymphatic spread from SI-NETs is common, mesenteric extranodal involvement is extremely rare, and its biology and primary versus secondary nature are not well understood. Due to their small size and location, SI-NETs are frequently undetected on anatomical imaging or indium-111-pentetreotide single-photon emission computed tomography/CT (Octreoscan) and are difficult to be found via endoscopy. Gallium-68-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-octreotate positron emission tomography (⁶⁸Ga-DOTATATE PET)/CT has been increasingly used for accurate staging, unknown primary tumour site localisation and appropriate management planning. We present a case of an incidentally found mesenteric NET with occult SI-NETs localised preoperatively by ⁶⁸Ga-DOTATATE PET/CT.

The safety of lanreotide for neuroendocrine tumor

INTRODUCTION

Lanreotide autogel is a synthetic somatostatin analogue which has been FDA and EMA approved for unresectable, well to moderately differentiated, locally advanced or metastatic gastroenteropancreatic neuroendocrine tumor. Its action is mediated by its affinity to somatostatin receptors, especially sst2 and sst5 receptors. Its longer half-life offers the convenience of 4-week dosing over the need for frequent injections of short-acting somatostatin analogues. Areas covered: Lanreotide ATG offers progression-free survival benefit in locally advanced or metastatic neuroendocrine tumor (NET) compared to placebo, reflecting a strong antiproliferative signal. As lanreotide is commonly used for management of NET, it is imperative to recognize and appropriately manage any drug-related toxicities. In this review, we will provide an overview of the toxicity with lanreotide and its management. Expert opinion: Lanreotide is highly effective in managing carcinoid symptoms and has a robust anti-tumor effect in NET. Overall, it is well tolerated with low rates of treatment discontinuation due to toxicity. It's toxicity profile is mostly predictable, and patients should be informed of the transient nature of some of the upfront toxicities.

Extremely Long Survival under Combined Immunotherapy in a Metastatic Functional Neuroendocrine Neoplasia Patient

Treatment and prognosis of neuroendocrine neoplasia depends on tumor size, stage, grade, resectability, and extent of distant metastasis. In most cases a multimodality approach including surgical, locally invasive procedures, peptide-guided radioreceptor therapy (PRRT), and medical therapies represent the mainstay of treatment in advanced disease. In the reported case, a 68-year-old man was diagnosed in 2010 with an initially functional (histamine) neuroendocrine tumor of gastric type III, G2, stage IVB, cT4cN1cM1 (hepatic, peritoneal, nodal, osseous), including a hepatic tumor load of 25%. Intensive multimodality approaches including combined immunotherapy (vaccination and PD-1/CTLA-4 blockade) led to a survival of 8 years until now with a high quality of life and minimal residual disease (only a single, small paragastric recurrence) despite the dedifferentiation of the tumor into a neuroendocrine carcinoma G3 (Ki-67 of 80%) including a nonfunctional stage.

Nothing But NET: A Review of Neuroendocrine Tumors and Carcinomas

This review covers the diverse topic of neuroendocrine neoplasms (NENs), a relatively rare and heterogeneous tumor type, comprising ~2% of all malignancies, with a prevalence of <200,000 in the United States, which makes it an orphan disease (Basu et al., 2010).1 For functional purposes, NENs are divided into two groups on the basis of clinical behavior, histology, and proliferation rate: well differentiated (low grade to intermediate grade) neuroendocrine tumors and poorly differentiated (high grade) neuroendocrine carcinoma (Bosman et al., 2010)2; this histological categorization/dichotomization is highly clinically relevant with respect to impact on treatment and prognosis even though it is not absolute since a subset of tumors with a low-grade appearance behaves similarly to high-grade lesions. Given the relative dearth of evidenced-based literature about this orphan disease as a whole (Modlin et al., 2008),3 since the focus of most articles is on particular anatomic subtypes of NENs (i.e., gastroenteropancreatic or pulmonary), the purpose of this review is to summarize the presentation, pathophysiology, staging, current standard of care treatments, and active areas of current research.

Fatal Systemic Vasoconstriction in a Case of Metastatic Small-Intestinal NET

An increased release of serotonin secreted by ileal NETs is thought to be the major factor causing the carcinoid syndrome. However, in acutely arising carcinoid crisis also other vasoactive factors may lead to hazardous fluctuations in blood pressure and bronchial constriction. In rare cases, systemic vasoconstriction can be observed, probably caused by catecholamines or similar acting substances. Here, we report a fatal case of fulminant systemic vasoconstriction possibly caused by catecholamines in a patient with metastasized ileal NET. The vasospasm was detected by CT-angiography, and hemodynamic monitoring revealed a high systemic vascular resistance. Epinephrine, norepinephrine, and chromogranin A levels in plasma were elevated as was the urinary 5-hydroxyindoleacetic acid (5-HIAA). The cause of death was heart failure due to severe circulatory insufficiency. The progression of the tumor disease was confirmed by autopsy.

Somatostatin analogues do not prevent carcinoid crisis

BACKGROUND

Carcinoid crisis is a life-threatening syndrome of neuroendocrine tumors (NETs) characterized by dramatic blood pressure fluctuation, arrhythmias, and bronchospasm. In the era of booming anti-tumor therapeutics, this has become more important since associated stresses can trigger carcinoid crisis. Somatostatin analogues (SSTA) have been recommended for prophylactic administration before intervention procedures for functioning NETs. However, the efficacy is still controversial. The aim of this article is to review efficacy of SSTA for preventing carcinoid crisis.

MATERIALS AND METHODS

PubMed, Cochrane Controlled trials Register, and EMBASE were searched using 'carcinoid crisis' as a search term combining terms with 'somatostatin'; 'octreotide'; 'lanreotide' and 'pasireotide' until December 2013.

RESULTS

Twenty-eight articles were retrieved with a total of fifty-three unique patients identified for carcinoid crisis. The most common primary sites of NETs were the small intestine and respiratory tract. The triggering factors for carcinoid crisis included anesthesia/ surgery (63.5%), interventional therapy (11.5%), radionuclide therapy (9.6%), examination (7.7%), medication (3.8%), biopsy (2%) and spontaneous (2%). No randomized controlled trials (RCTs) were identified and two case-control studies were included to assess the efficacy of SSTA for preventing carcinoid crisis by meta-analysis. The overall pooled risk of perioperative carcinoid crisis was similar despite the prophylactic administration of SSTA (OR 0.44, 95% CI: 0.14 to 1.35, p=0.15).

CONCLUSIONS

SSTA was not helpful for preventing carcinoid crisis based on a meta-analysis of retrospective studies. Attentive monitoring and careful intervention are essential. Future studies with better quality are needed to clarify any effect of SSTA for preventing carcinoid crisis.

Gastro-Enteropancreatic Neuroendocrine Tumor Cell Dynamics in Liver Microvasculature

For many cancers, liver metastasis is common and usually indicates poor prognosis. Gastro-enteropancreatic neuroendocrine tumors (GEPNETs) of the midgut are a heterogeneous group of cancers that typically remain asymptomatic until they metastasize to the liver. However, the mechanisms by which these usually indolent cancers establish distal metastasis remain unclear. To begin to elucidate this process, we performed standard in vitro assays to assess cell motility, transendothelial migration, and invasion using BON cells, a widely used model GEPNET cell line. In addition, transmission electron microscopy was used in combination with a novel ex vivo organ slice xenograft model to reveal ultrastructural details of the initial events of BON cell extravasation and re-distribution within the liver. The ultrastructural resolution of the extravasation process revealed the route, sequence, and time course by which tumor cells migrated from the sinusoidal lumen into the hepatic parenchyma in this organ slice model. Both standard in vitro assays and our organ slice model indicated that tumor cells migrated through the discontinuous sinusoidal endothelium to invade the liver parenchyma.

Comparison of 24-h and overnight samples of urinary 5-hydroxyindoleacetic acid in patients with intestinal neuroendocrine tumors

Neuroendocrine tumors (NETs) arising in the small intestine are known to produce vasoactive substances, including serotonin, that may result in the carcinoid syndrome (flushing, diarrhea, bronchoconstriction, and carcinoid heart disease). Measurement of the serotonin breakdown product 5-hydroxyindoleacetic acid (5-HIAA) in urine is important in diagnosing and monitoring of patients with intestinal NETs. Our aim was to compare 5-HIAA measurement in 24-h urine sampling with overnight (∼8-h) sampling in patients with known NETs, or at follow-up of patients potentially cured for their NETs. Twenty-four-hour and overnight urine samples were collected from 34 patients and analyzed for urinary 5-HIAA (U5-HIAA) using HPLC. Comparison of the overnight sampling values with the 24-h values showed no difference, P=0.45, and there was a significant direct correlation between the two samples using linear regression (R=0.97, P<0.001). U5-HIAA sample collection during a nightly interval of ∼8 h appears to have the same accuracy as the 24-h collection in this group of patients.

Primary mesenteric carcinoid tumor

Primary mesenteric carcinoid tumor is very rare, although secondary mesenteric involvement is common, reported as 40% to 80%. And distant metastasis rate reported as 80% to 90%, when the size is larger than 2 cm. We present a case of very rare primary mesenteric carcinoid tumor showing benign character though large size. The patient visited St. Vincent's Hospital, The Catholic University of Korea with increasing palpable abdominal mass. At laparotomy, a well encapsulated mass arising from the mesentery near the ligament of Treitz was found without any adjacent organ invasion or distant metastasis. The mass was measured as 8.2 × 7.3 cm and histopathologically benign character. At 11 months of follow up, the patient was recurrence free.

Management of gastrointestinal carcinoid tumours - 10 years experience at a district general hospital

BACKGROUND

There is paucity of guidelines regarding management of gastrointestinal carcinoid tumours in district hospitals.

METHODS

This study was undertaken at a district hospital to analyse the management pathway of gastrointestinal carcinoid tumours.

RESULTS

Over a period of 10 years there were 35 patients, with an estimated annual incidence of 2.5 per 100,000 population. After a median follow up of 24 months, 22 (63%) patients were alive and disease free. Only 56% patients were referred to the regional neuro-endocrine multidisciplinary team.

CONCLUSIONS

Management of patients with carcinoid tumours in district hospitals needs streamling with increased utilisation of regional neuroendocrine multidisciplinary teams.

Radioguided exploration facilitates surgical cytoreduction of neuroendocrine tumors

INTRODUCTION

Radioguided exploration (RGS) can be an important tool to direct the cytoreduction of neuroendocrine tumors (NETs). The selection of the proper radiolabeled isotope, the dose, and the time interval between isotope injection and exploration are the major factors that lead to the successful use of this technique.

METHODS

Data on 43 patients who underwent RGS of their NET at our facility (Ochsner Medical Center-Kenner) was collected. These cases were reviewed to determine the optimal radiopharmaceutical, dose, and interval between injection and exploration.

RESULTS

The isotopes used were (99)technetium sulfur colloid in three patients, (123)I metaiodobenzylguanidine ((123)I-MIBG) in six patients, and (111)In-pentreotide in 30 abdominal NET patients and in four patients undergoing neck and mediastinum explorations. In 29 of 30 (111)In-pentreotide-guided abdominal explorations (five of which were re-explorations, all successful), the gamma detector was determined to be "helpful". In the four neck and mediastinum explorations, the gamma probe was deemed "essential" for completing a quick, safe, and minimally invasive procedure. (123)I-MIBG injection, in contrast, was useful in only one patient. The optimal dose and interval between injection and exploration of (111)In-pentreotide were discovered to be 6 mCi injected 7 days prior to the planned exploration.

CONCLUSION

Radioguided exploration is a useful tool to guide the cytoreduction of NETs. The correct choice of radiopharmaceutical, its dose, and the interval between injection and exploration are critical for obtaining optimal results.

Ingestion of a foreign body unmasks an asymptomatic small bowel carcinoid tumor

Bowel obstruction is a common surgical admission around the world. On the other hand, small intestinal tumors, such as midgut carcinoid, are uncommon neoplasms and an infrequent cause of intestinal obstruction leading to hospitalization. A foreign body is an extremely rare cause of intestinal obstruction and when ingested, foreign bodies most often lodge in the narrowest portion of the gastrointestinal tract. Narrowing of the small bowel due to a neoplasm can prohibit the passage of an accidentally ingested foreign object and produce an obstruction that neither the neoplasm nor the foreign body could have produced alone. We hereby report a case in which an accidentally ingested piece of foreign material leads to the finding of a small, early stage, asymptomatic, midgut carcinoid cancer in the proximal ileum that would have otherwise eluded detection for several years.

Carcinoid syndrome and perioperative anesthetic considerations

Carcinoid tumors are uncommon, slow-growing neoplasms. These tumors are capable of secreting numerous bioactive substances, which results in significant potential challenges in the management of patients afflicted with carcinoid syndrome. Over the past two decades, both surgical and medical therapeutic options have broadened, resulting in improved outcomes. The pathophysiology, clinical signs and symptoms, diagnosis, treatment options, and perioperative management, including anesthetic considerations, of carcinoid syndrome are presented.

Long-term survival with metastatic carcinoid tumors: a case report and review of the literature

Post hoc studies investigating patients with metastatic carcinoid tumors consistently have demonstrated outcomes that are not all too promising in terms of long-term survival, particularly for those with multiple metastases to the small bowel, mesentery, and liver. Here we present a patient with these clinical findings who, contrary to current expectations, has survived much longer than anticipated. This case is a sobering reminder for physicians not only to evaluate carefully and care for their patients but also to choose their words carefully in all communication with them.

Development and characterization of a novel in vivo model of carcinoid syndrome

PURPOSE

Carcinoid syndrome, characterized by flushing, diarrhea, and valvular heart disease, can occur following carcinoid tumor metastasis to the liver and systemic release of bioactive hormones into the systemic circulation. Treatment of this devastating disease is hampered by the lack of an in vivo model that recapitulates the clinical syndrome.

EXPERIMENTAL DESIGN

Here, we have injected BON cells, a novel human carcinoid cell line established in our laboratory, into the spleens of athymic nude mice to establish liver metastases.

RESULTS

The majority of mice injected intrasplenically with BON cells developed significant increases in plasma serotonin and urine 5-hydroxyindoleacetic acid, and several mice exhibited mesenteric fibrosis, diarrhea, and fibrotic cardiac valvular disease reminiscent of carcinoid syndrome by both echocardiographic and histopathologic evaluation. Mice pretreated with octreotide, a long-acting somatostatin analogue, or bevacizumab, a vascular endothelial growth factor inhibitor, developed fewer liver metastases and manifestations of carcinoid syndrome, including valvular heart disease.

CONCLUSION

We have provided an important in vivo model to further delineate novel treatment modalities for carcinoid syndrome that will also be useful to elucidate the factors contributing to the sequelae of carcinoid disease (e.g., mesenteric fibrosis and valvular heart disease).

Case of carcinoid crisis following a fine-needle biopsy of hepatic metastasis

Fine-needle biopsy of hepatic lesions in a patient with carcinoid liver metastasis can precipitate carcinoid crisis. We report a case of carcinoid crisis following a liver biopsy. Recognition of this unusual presentation of this condition is important to enable all appropriate preparatory measures to be taken and resuscitative equipment to be available.

Síndrome carcinóide: relato de caso

Os tumores carcinóides são raros, com incidência aproximada de um a dois casos por 100.000 habitantes. Estima-se que a síndrome carcinóide - que se caracteriza por flushing, diarréia, dor abdominal e, em menor freqüência, pelagra, broncoespasmo e doença valvar cardíaca - ocorra em menos de 10% dos doentes. Entretanto, nos casos avançados a incidência varia de 40 a 50%. Estudos retrospectivos e de série de casos mostram que as manifestações cutâneas são freqüentes nessa entidade, embora sejam raramente relatadas. Apresenta-se um caso de síndrome carcinóide diagnosticadoa partir das manifestações dermatológicas.

Carcinoid tumor and carcinoid syndrome

PURPOSE OF REVIEW

Carcinoid tumors secrete many different types of substances (e.g. serotonin, bradykinin) that may produce potentially fatal intraoperative reactions such as hypotension and bronchoconstriction. The most effective treatment for the deleterious cardiovascular and pulmonary effects of serotonin and bradykinin is octreotide, a somatostatin analogue. Carcinoid heart disease, which develops in the majority of patients with carcinoid syndrome, presents the anesthesiologist with more diagnostic and therapeutic dilemmas.

RECENT FINDINGS

The incidence of carcinoid tumors is much greater than previously recognized. New diagnostic techniques permit identification and localization of carcinoid tumors with greater accuracy. Short term and long term therapy with octreotide significantly improves survival and reduces the severity of 'carcinoid crises'. Echocardiographic studies have demonstrated a very high incidence of carcinoid heart disease (tricuspid and pulmonary insufficiency) in patients with carcinoid syndrome. Cardiac valve surgery is, consequently, becoming much more common in patients with carcinoid syndrome.

SUMMARY

More patients with carcinoid tumors and carcinoid syndrome are requiring anesthesia and surgery. Specific therapy with somatostatin analogues (octreotide) has replaced older less specific drugs (e.g. antihistamines) for the treatment of adverse effects caused by products of carcinoid tumors.

Therapeutic options for gastrointestinal carcinoids

Although wide surgical resection is the optimal curative therapy for carcinoid tumors, in most patients the presence of metastatic disease at diagnosis usually renders excision a palliative procedure. This nevertheless decreases tumor burden, facilitates symptom control, and prevents complications caused by bleeding, perforation, or bowel obstruction resulting from fibrosis. In the stomach (types I and II) and rectum endoscopic excision may be adequate provided the lesion(s) are local. Long-term therapy is focused on symptom alleviation and improvement of quality of life using somatostatin analogues, particularly in a subcutaneous depot formulation. In some instances interferons may have a role but their usage often is associated with substantial adverse events. Conventional chemotherapy and external radiotherapy either alone or in a variety of permutations are of minimal efficacy and should be balanced against the decrease in quality of life often engendered by such agents. Hepatic metastases may be amenable to surgery, radiofrequency ablation, or embolization either alone or in combination with chemotherapeutic agents or isotopically loaded microspheres. Rarely hepatic transplantation may be of benefit although controversy exists as to its actual use. Peptide-receptor-targeted radiotherapy for advanced disease using radiolabeled octapeptide analogs (111In/90Yt/177Lu-octreotide) appear promising but data are limited and its status remains investigational. A variety of antiangiogenesis and growth factor-targeted agents have been evaluated, but as yet have shown little promise. The keystone of current therapy remains the long-acting somatostatin analogues that alleviate symptomatology and substantially improve quality of life with minimal adverse effects.

Carcinoid syndrome: diagnosis and medical management

Gastro-intestinal carcinoids are slow growing tumors arising from enterochromaffin or Kulchitsky cells. Their clinical presentation depends on what combination of bioactive substances is secreted. Midgut carcinoid can present with the carcinoid syndrome in the presence of liver metastases. Its most typical clinical manifestations include cutaneous flushing and diarrhea. A nonspecific biochemical tumor marker for carcinoid tumors is serum chromogranin A and a specific marker for the carcinoid syndrome is the increased urinary excretion of 5-hydroxy indole acetic acid (5-HIAA). Localizing studies in carcinoid tumors/syndrome are: transabdominal ultrasonography (US), endoscopy, endoscopic US, videocapsule endoscopy, computerized tomography, magnetic resonance imaging, selective abdominal angiography, 111In-pentetreotide scintigraphy (and intraoperative radionuclide probe), 123I (131I)-metaiodobenzylguanidine (MIBG) scintigraphy, bone scintigraphy and 11C-5-HT positron emission tomography (PET). Therapies for carcinoid tumors/syndrome are: surgery, somatostatin analogs, interferon-alpha, radiotherapy, liver dearterialization, liver (chemo, or radio)-embolization, alcohol sclerotherapy of liver metastases, radiofrequency ablation of liver metastases, cryosurgery of liver metastases, occasionally liver transplantation, radiotherapy-coupled somatostatin analogs, 131I-MIBG and occasionally chemotherapy.

Midgut carcinoid tumours: surgical treatment and prognosis

Midgut carcinoids originating in the small intestine are the most common cause of the carcinoid syndrome. These tumours typically progress slowly and have an extended disease course, and although they often present with metastases at diagnosis, surgical treatment has become increasingly important for their management. Surgery should include efforts to remove mesenteric metastases, which may cause severe long-term abdominal complications with typical fibrotic intestinal entrapment and small-bowel ischaemia due to compression of mesenteric vessels. Attempts should also be made to surgically remove or ablate liver metastases, since this may provide considerable palliation of the carcinoid syndrome. For patients with the carcinoid syndrome surgery is combined with continuous biotherapy with long-acting somatostatin analogues, which may alleviate symptoms and stabilize disease or slow progression. Favourable survival and appreciable quality of life can be expected with this combined treatment, even in patients with advanced midgut carcinoids.

Hereditary hormone excess: genes, molecular pathways, and syndromes

Hereditary origin of a tumor helps toward early discovery of its mutated gene; for example, it supports the compilation of a DNA panel from index cases to identify that gene by finding mutations in it. The gene for a hereditary tumor may contribute also to common tumors. For some syndromes, such as hereditary paraganglioma, several genes can cause a similar syndrome. For other syndromes, such as multiple endocrine neoplasia 2, one gene supports variants of a syndrome. Onset usually begins earlier and in more locations with hereditary than sporadic tumors. Mono- or oligoclonal ("clonal") tumor usually implies a postnatal delay, albeit less delay than for sporadic tumor, to onset and potential for cancer. Hormone excess from a polyclonal tissue shows onset at birth and no benefit from subtotal ablation of the secreting organ. Genes can cause neoplasms through stepwise loss of function, gain of function, or combinations of these. Polyclonal hormonal excess reflects abnormal gene dosage or effect, such as activation or haploinsufficiency. Polyclonal hyperplasia can cause the main endpoint of clinical expression in some syndromes or can be a precursor to clonal progression in others. Gene discovery is usually the first step toward clarifying the molecule and pathway mutated in a syndrome. Most mutated pathways in hormone excess states are only partly understood. The bases for tissue specificity of hormone excess syndromes are usually uncertain. In a few syndromes, tissue selectivity arises from mutation in the open reading frame of a regulatory gene (CASR, TSHR) with selective expression driven by its promoter. Polyclonal excess of a hormone is usually from a defect in the sensor system for an extracellular ligand (e.g., calcium, glucose, TSH). The final connections of any of these polyclonal or clonal pathways to hormone secretion have not been identified. In many cases, monoclonal proliferation causes hormone excess, probably as a secondary consequence of accumulation of cells with coincidental hormone-secretory ability.

Management of midgut carcinoids

Midgut carcinoids developing in the small intestine represent the most common cause of the carcinoid syndrome, with severe symptoms of flush, diarrhoea, and fibrotic valvular heart disease. The tumours may be histologically identified with specific chromogranin A or synaptophysine immunostainings, and by serotonin reactivity, which supports a midgut origin. Urinary 5-HIAA excretion and serum chromogranin A measurements are used as biochemical tumour markers for clinical diagnosis, and as important monitors of treatment effects and prognostic predictors. The midgut carcinoids have typically slow proliferation and extended disease course, and surgical treatment has become increasingly important for their management. Surgery should aim to remove primary tumours and mesenteric metastases, which may cause long-term abdominal complications, by typical fibrotic intestinal entrapment and small bowel ischaemia due to encasement of mesenteric vessels. Attempts should also be made to surgically remove or ablate liver metastases, since this may significantly contribute to palliation of the carcinoid syndrome. In patients with this syndrome surgery is combined with continuous biotherapy with long-acting somatostatin analogues and interferon, which may alleviate symptoms and cause stable disease with slow progression. Favourable survival and life-quality can be expected with this treatment also in patients with advanced midgut carcinoids.

Characterization of Site-Specific ScFv PEGylation for Tumor-Targeting Pharmaceuticals

New radiopharmaceuticals are possible using site-specific conjugation of small tumor binding proteins and poly(ethylene glycol) (PEG) scaffolds to provide modular multivalent, homo- or heterofunctional cancer-targeting molecules having preferred molecular size, valence, and functionality. Residence time in plasma can be optimized by modification of the size, number, and charge of the protein units. However, random PEG conjugation (PEGylation) of these small molecules via amine groups has led to variations of structural conformation and binding affinity. To optimize PEGylation, scFvs have been recombinantly produced in a vector that adds an unpaired cysteine (c) near the scFv carboxy terminus (scFv-c), thus providing a specific site for thiol conjugation. To evaluate the general applicability of this unpaired cysteine for PEGylation of scFv-c, conjugation efficiency was determined for four different scFvs and several PEG molecules having thiol reactive groups. The effect of the PEG molecular format on scFv-c PEG malignant cell binding was also addressed. ScFvs produced as scFv-c and purified by anti E-TAG affinity chromatography were conjugated using PEG molecules with maleimide (Mal) or o-pyridyl disulfide (OPSS). Conjugations were performed at pH 7.0, with 2 molar excess TCEP/scFv and PEG-(Mal) or PEG-OPSS, using 5:1 (PEG/scFv). PEG-Mal conjugation efficiency was also evaluated with 1:5 (PEG/scFv). PEGylation efficiency was determined for each reaction by quantitation of the products on SDS-PAGE. ScFv-c conjugation with unifunctional maleimide PEGs resulted in PEG conjugates incorporating 30-80% of the scFv-c, but usually above 50%. Efficiency of scFv-c conjugation to both functional groups of the bifunctional PEG-(Mal)2 varied between the PEG and scFv-c molecules studied. A maximum of 45% of scFv-c protein was conjugated as PEG- (scFv-c)2 using the smallest PEG-(Mal)2 (2 kDa). No significant increase in scFv-c conjugation was observed by the use of greater than a 5 molar excess of PEG/scFv-c. Under the same conjugation conditions, PEG as OPSS yielded less than 10% PEG-scFv-c. PEG-(scFv)2 conjugates had increased binding in ELISA using malignant cell membranes, when compared with unmodified scFv-c. PEGylated-scFv binding was comparable with unmodified scFv-c. In summary, scFv-c can be PEGylated in a site-specific manner using uni- or bivalent PEG-Mal, either linear or branched. ScFv-c was most efficiently conjugated to smaller PEG-Mal molecules, with the smallest, 2 kDa PEG-Mal, usually PEGylating 60-90% of the scFv-c. ScFv-c conjugation to form PEG-(scFv-c)2 reached greatest efficiency at 45%, and its purified form demonstrated greater binding than the corresponding scFv-c.

[Solitary hepatic carcinoid tumor in a man with prior treatment for rectal adenocarcinoma. Rapid growth without carcinoid syndrome]

We describe a case of hepatic carcinoid tumor that was diagnosed after right hepatectomy. The tumor was initially believed to be metastases from a rectal adenocarcinoma for which surgery had been performed seven years earlier. We highlight the localization of the tumor in the liver only, its large size and rapid growth, as well as the absence of carcinoid syndrome. Diagnostic studies of function and localization are presented. The absence of neoplasia in other locations suggested that this neoplasm was probably a primary hepatic carcinoid tumor. The association of carcinoid tumors with other neoplasms is well-known. However, because of our patient's history and the absence of symptoms, the preoperative diagnosis was incorrect. The definitive diagnosis was confirmed by pathological analysis, allowing specific studies of function and localization to be performed and therapeutic and follow-up measures to be adopted. Although surgery plays a crucial role in the treatment of these tumors, it should be performed in the context of the multidisciplinary management recommended for this disease.

Production of Soluble ScFvs with C-Terminal-Free Thiol for Site-Specific Conjugation or Stable Dimeric ScFvs on Demand

ScFv recombinant antibody fragments can provide specific tumor binding modules for targeting drugs. In the process of building multimeric tumor targeting pharmaceuticals, a prerequisite is the conservation of functional scFv antigen binding domains, thereby excluding scFv random conjugation to a carrier molecule or to another scFv. The pCANTAB 5E phage display/expression vector was genetically engineered to express any scFv gene as scFv with an additional C-terminal cysteine (scFv-Cys) such that the specific conjugation site is removed from the binding domain. Selected scFvs derived from an anti-MUC-1 scFv phage library were expressed in pCANTAB 5E and its modified version pCANTAB 5E Cys vectors, and compared for key characteristics. Production yields of scFv and scFv-Cys in shaker flask and biofermentor were compared. In the absence of a reducing agent, stable dimers (covalent scFv homodimers (scFv-Cys)2) were the major form of scFv-Cys. These diabodies provided substantial signal enhancement for immunohistochemical staining of tissues. In the presence of a reducing agent, scFv-Cys molecules remained monomeric, with the free SH available for conjugation to a PEG(maleimide)2 scaffold to form immunoreactive PEG(scFv)2 bioconjugates. ScFv expression from pCANTAB 5E Cys allowed for the production of soluble scFv-Cys protein from E.coli, either as stable scFv-Cys or (scFv-Cys)2. ScFv-Cys can be used for conjugation to PEG to form bivalent PEG (scFv-Cys)2 molecules or used as (scFv-Cys)2 for increased sensitivity in IHC.