Insulin-like growth factors and non-islet cell tumor hypoglycemia

The Great Masquerader's New Wardrobe in the Modern Era: The Paraneoplastic Manifestations of Renal Cancer

Paraneoplastic syndromes can occur in 8% to 20% of individuals with malignancies. They can occur in a variety of cancers that include breast, gastric, leukemia, lung, ovarian, pancreatic, prostate, testicular, as well as kidney. The classic presentation of the triad of mass, hematuria, and flank pain occurs in less than 15% of patients with renal cancer. Because of the protean presentations of renal cell cancer, it has been referred to as the internist's tumor or the great masquerader. This article will provide a review of the causes of these symptoms.

Resolution of paraneoplastic hypoglycemia following nephroureterectomy for treatment of canine renal cell carcinoma: Case report

Objectives

To describe the clinicopathologic findings, imaging results, surgical treatment, and outcome of a dog with renal cell carcinoma (RCC) and paraneoplastic hypoglycemia.

Animals

A 13-year-old female spayed mixed breed dog that was presented for facial twitching and neurologic decline and diagnosed with a renal mass and paraneoplastic hypoglycemia.

Study design

Case report.

Methods

Serum chemistry revealed severe hypoglycemia and normal renal values. Abdominal ultrasonography showed a large, heterogeneous, cavitated mass associated with the left kidney and no evidence of abdominal metastatic disease. Thoracic radiographs revealed no evidence of pulmonary metastatic disease. Fasted serum insulin was low concurrently with severe hypoglycemia. No other causes of hypoglycemia were detected, and paraneoplastic hypoglycemia was suspected.

Results

After initial medical management of the dog's hypoglycemia, left nephroureterectomy was performed. Histopathology was consistent with RCC. Postoperatively, the dog's hypoglycemia resolved, and supplementation was discontinued. The dog remained stable and was discharged from the hospital 3 days after surgery. At 2-week, 3-month, and 5-month follow up evaluations, the dog remained euglycemic, and no definitive evidence of disease progression was detected. Eight months postoperatively, the dog was euthanized due to decline in mobility. Necropsy and histopathology revealed cerebral and spinal cord multifocal myelin sheath dilation and two primary pulmonary carcinomas with no evidence of recurrence or metastasis of the RCC.

Conclusion

Surgical treatment of RCC with subsequent resolution of paraneoplastic hypoglycemia has not previously been reported in veterinary medicine. In this dog, nephroureterectomy for RCC resulted in immediate and sustained resolution of paraneoplastic hypoglycemia.

Severe recurrent hypoglycaemia in a patient with aggressive melanoma

We present a case of hypoglycemia in a young patient without diabetes mellitus who presented initially with enlarging neck mass and weight loss, and was found to have aggressive melanoma with metastasis to multiple organs and diffuse lymphadenopathy. He had presented to the emergency room two times with neuroglycopenic symptoms that required admission and intravenous dextrose continuously. Evaluation of hypoglycemia included C-peptide, insulin levels, insulin-like growth factor (IGF) -I and -II, and ß- hydroxybutyrate. Insulin levels were suppressed appropriately during hypoglycemia, however, IGF-II:IGF-I ratio was high, suggesting non-islet tumour induced hypoglycemia. The presence of IGF-II produced by large tumors results in a low hepatic glucose output and increased uptake by skeletal muscle, resulting in hypoglycemia especially in a patient with extremely low appetite such as our patient. Treating the culprit malignancy leads to resolution of hypoglycemia, but corticosteroids have been used to suppress IGF-II levels and alleviate symptoms.

Early Improvement of Non-islet Cell Tumor Hypoglycemia by Chemotherapy Using Lenvatinib in a Case with Type 2 Diabetes and Hepatocellular Carcinoma Producing Big IGF-II

A 77-year-old man was treated with a DPP-4 inhibitor for type 2 diabetes. Hypoglycemia occurred frequently, and an examination revealed a tumor with a maximum diameter of 140 mm in both lobes of the liver. Western immunoblotting detected a high-molecular-weight form of insulin-like growth factor-II, and non-islet cell tumor hypoglycemia was diagnosed. Although prednisolone 40 mg was started, hypoglycemia continued to occur frequently. Surgical tumor removal was not indicated, so lenvatinib was initiated. Hypoglycemia improved quickly, and the tumor shrank until it had partially disappeared. His condition continued to improve, and he was discharged.

Late-onset non-islet cell tumor hypoglycemia: A case report

BACKGROUND

Hypoglycemia due to non-insulin-producing tumors is referred to as non-islet cell tumor hypoglycemia (NICTH). As NICTH is a rare lesion, the natural course of NICTH is not well understood. We report a case of NICTH that was observed 30 years before the onset of hypoglycemia.

CASE SUMMARY

A 50-year-old man was diagnosed with an abnormal right chest shadow during a routine X-ray examination, but no further examination was undertaken because the lesion appeared benign. Thirty years after the tumor discovery, the patient was admitted to the hospital with symptoms of severe hypoglycemia, which was diagnosed as NICTH based on a complete examination. The tumor was resected and found to be a solitary fibrous mass (15.6 cm × 13.7 cm × 10.4 cm); thereafter, the patient’s blood glucose levels normalized and he completely recovered.

CONCLUSION

NICTH can have an acute onset, even if the tumor has been present and asymptomatic over a long time period.

Doege-Potter syndrome presenting as 'end-stage renal disease-associated hypoglycaemia': a primary presentation of retroperitoneal sarcoma

A middle-aged woman with end-stage renal disease (ESRD) due to obstructive nephropathy presented to the hospital for an episode of unresponsiveness and hypoglycaemia. Initially, she was diagnosed with hypoglycaemia associated with ESRD and was discharged. However, she returned to the hospital after experiencing tonic-clonic seizures and recurrent hypoglycaemia. Her hypoglycaemia workup revealed an elevated insulin-like growth factor 2 (IGF2) to IGF1 ratio consistent with paraneoplastic IGF2 secretion. Subsequently, a CT abdomen revealed a retroperitoneal mass, found to be a retroperitoneal sarcoma. Her hypoglycaemia was treated with glucocorticoids and growth hormone. Surgical debulking of her tumour was attempted, but she expired due to postoperative haemorrhagic shock. Doege-Potter syndrome is a rare cause of hypoglycaemia which should be suspected in any new-onset, worsening, inexplicable or refractory hypoglycaemia, particularly in non-diabetic ESRD. Here we present a report of retroperitoneal sarcoma presenting with hypoglycaemia in a patient with ESRD without diabetes.

Recurrent hypoglycemia triggered by sorafenib therapy in a patient with hemangiopericytoma

Targeted therapy has been proven to be one of the most effective cancer treatments. However, some endocrine disorders can occur during treatment with targeted agents. We report the case of a patient who exhibited a wax and wane pattern of hypoglycemia that was attributed to sorafenib therapy. A 32-year-old woman with metastatic hemangiopericytoma visited the emergency department in a stuporous state. Nonhyperinsulinemic hypoglycemia was diagnosed, was exacerbated shortly after sorafenib therapy, and was improved by the cessation of sorafenib with additional glucocorticoid therapy. Patients with metastatic hemangiopericytoma should be carefully monitored with particular attention to hypoglycemia when sorafenib therapy is initiated.

Management of non-islet-cell tumor hypoglycemia: a clinical review

CONTEXT

Non-islet cell tumor hypoglycemia (NICTH) is a rare but serious paraneoplastic syndrome in which a tumor secretes high molecular weight IGF-II, causing hypoglycemia. Complete tumor resection is curative but is often delayed or unfeasible. There is no clear "standard of care" for managing these patients.

EVIDENCE ACQUISITION

PubMed searches were conducted for: "non-islet-cell tumor hypoglycemia," "NICTH," "Doege-Potter," "Doege-Potter syndrome," "high molecular weight IGF-II," and "big IGF-II." Relevant articles were reviewed in detail. We limited our review to English-language articles, focusing on 1988-2013 (corresponding with the elucidation of the pathophysiology of NICTH).

EVIDENCE SYNTHESIS

The available literature exists as case reports or small case series, with a void of higher-order treatment studies. Thus, an evidence-based approach to data synthesis was difficult. Nevertheless, the available literature is presented objectively with an attempt to describe clinically useful trends and findings in the management of NICTH.

CONCLUSIONS

Appropriate identification of NICTH and prompt and complete tumor resection represents ideal management. However, when prompt resection is not feasible, iv glucose or dextrose often does not suffice to prevent hypoglycemia. In such cases, we suggest consideration of local antitumor therapies for disease control and trial of glucocorticoids alone or in combination with GH. Continuous glucagon infusion can be successful if the patient has a positive response to a glucagon stimulation test, and parenteral nutrition may allow higher glucose delivery, but both are limited by the need for continuous iv infusion. Diazoxide and octreotide have no role in NICTH.

IGF2 and cancer

Insulin-like growth factor 2 (IGF2) is a 7.5  kDa mitogenic peptide hormone expressed by liver and many other tissues. It is three times more abundant in serum than IGF1, but our understanding of its physiological and pathological roles has lagged behind that of IGF1. Expression of the IGF2 gene is strictly regulated. Over-expression occurs in many cancers and is associated with a poor prognosis. Elevated serum IGF2 is also associated with increased risk of developing various cancers including colorectal, breast, prostate and lung. There is established clinical utility for IGF2 measurement in the diagnosis of non-islet cell tumour hypoglycaemia, a condition characterised by a molar IGF2:IGF1 ratio >10. Recent advances in understanding of the pathophysiology of IGF2 in cancer have suggested much novel clinical utility for its measurement. Measurement of IGF2 in blood and genetic and epigenetic tests of the IGF2 gene may help assess cancer risk and prognosis. Further studies will determine whether these tests enter clinical practice. New therapeutic approaches are being developed to target IGF2 action. This review provides a clinical perspective on IGF2 and an update on recent research findings.

The insulin-like growth factor system and sarcomas

Sarcomas are a diverse group of malignant mesenchymal tumours arising from bone and soft tissues. The identification of critical cellular signalling pathways in sarcomas is an important issue for the development of new targeted therapies. This review highlights the experimental and clinical evidence supporting the role of the insulin-like growth factor (IGF) signalling system in the cellular transformation and progression of several types of sarcoma, including rhabdomyosarcoma, synovial sarcoma, leiomyosarcoma, Ewing's sarcoma and osteosarcoma. Preclinical data suggest that the IGF system could be a promising target for therapy in these sarcomas. Currently, therapies interrupting IGF signalling have been or are being developed. In recent phase 1 clinical studies with humanized monoclonal antibodies directed against IGF receptor type 1 (IGF-1R), objective tumour responses were observed in several patients with Ewing's sarcoma, encouraging further clinical testing in Ewing's sarcoma and other sarcoma (sub)types. Moreover, the occasional occurrence of paraneoplastic hypoglycaemia as a result of the secretion of incompletely processed forms of pro-IGF-II by sarcomas is discussed.

A case of a giant phyllodes tumor of the breast with hypoglycemia caused by high-molecular-weight insulin-like growth factor II

We report the case of a patient who presented with hypoglycemia associated with a giant breast mass and presence of serum high-molecular-weight insulin-like growth factor II (big IGF-II). In July 2005, a 49-year-old woman was admitted because of delirium, transient loss of consciousness, and a giant mass of about 28 cm in diameter on the right breast. She had noticed the mass for more than 2 years, but had refused medical attention at that time. A blood examination indicated hypoglycemia (21 mg/dl) and decreased levels of endogenous insulin. Furthermore, a western blot analysis revealed that big IGF-II (20 kDa) was the predominant serum IGF-II peptide (mature IGF-II is 7.5 kDa). Because we suspected that the big IGF-II was produced by the breast tumor and was likely the cause of the hypoglycemia, a mastectomy was performed. A histological examination determined that the mass was a benign phyllodes tumor. After surgery, the hypoglycemia resolved, and endogenous insulin levels improved. We suspected that the patient had non-islet cell tumor hypoglycemia (NICTH), but the behavioral symptoms of the hypoglycemia caused by NICTH were similar to some mental diseases, which made diagnosis based on the behavior alone difficult. We suggest that co-occurrence of symptoms such as recent appearance of mental disease-like behavior, hypoglycemia, and giant breast tumor may help diagnose NICTH caused by big IGF-II.

Hypoglycemia associated with the production of insulin-like growth factor II in a pancreatic islet cell tumor: a case report

An insulinoma is characterized by endogenous hyperinsulinemia and hypoglycemia. However, it has been reported that insulinomas with normal levels of plasma insulin and a normal insulin to glucose ratio occur in patients with hypoglycemia. Although overproduction of Insulin-like growth factor II (IGF-II) by non-islet cell tumors such as large mesenchymal tumors, can cause hypoglycemia, no cases of circulating plasma IGF-II from an islet cell tumor contributing to hypoglycemia have been reported. We report here a rare case of a pancreatic islet tumor in a patient with hypoglycemia that was associated with increased plasma IGF-II, which returned to normal after tumor resection.

Secondary hypertrophic osteoarthropathy associated with solitary fibrous tumor of the lung

Secondary hypertrophic osteoarthropathy, synonymous with the terms "pulmonary hypertrophic osteoarthropathy" and "pachydermoperiostosis acquisita," is a syndrome characterized by finger clubbing, hypertrophic skin changes, and periosteal bone changes that can occur in patients with underlying disease of the cardiovascular and pulmonary systems. We report the case of a 56-year-old man with a solitary fibrous tumor of the lung causing symptomatic hypoglycemia and secondary hypertrophic osteoarthropathy. The patient was seen in the dermatology clinic because of his skin changes. Diagnostic work-up included imaging that revealed a large mass in the left lower lobe of his lung later identified as a solitary fibrous tumor. The patient underwent pneumonectomy and at 1-month follow-up had returned to a euglycemic state with resolution of his skin findings. Dermatologists may play a key role in early diagnosis of tumors of the lung and other extrathoracic sites, such as solitary fibrous tumors, as well as many endocrine disorders, through the recognition of the cutaneous and soft tissue manifestations.

Solitary fibrous tumor associated with non-islet cell tumor hypoglycemia

A 79-year-old man presented with abnormal fluttering movements of his extremities early in the morning. Fasting hypoglycemia was believed to be the cause of the movements. A computed tomographic scan showed a large mass in the left inferior hemithorax. Non-islet cell tumor hypoglycemia was suspected, and the mass was resected while the patient was under glucose supplementation therapy. The plasma glucose level became stable shortly after tumor excision. The resected tumor was diagnosed as a solitary fibrous tumor producing insulin-like growth factor II. In the follow-up examination approximately 2 years after the surgery, no recurrence of the tumor was observed, and the plasma glucose level was stable.

Mechanisms and management of non-islet cell tumour hypoglycaemia in gastrointestinal stromal tumour: case report and a review of published studies

Tumour-related hypoglycaemia is a rare paraneoplastic phenomenon most frequently occurring with insulinomas, but also associated with non-islet cell tumours. It has been observed in a range of tumour types, but recently a small number of cases have been described in association with gastrointestinal stromal tumours. We describe a further case of a patient with gastrointestinal stromal tumour that was complicated by non-islet cell tumour hypoglycaemia, and discuss the mechanisms and management of non-islet cell tumour hypoglycaemia in the context of gastrointestinal stromal tumour.

The therapeutic challenge of a nonresectable solitary fibrous tumor in a hypoglycemic patient

We report a patient with a nonresectable histologically benign solitary fibrous tumor who suffered from paraneoplastic non-islet cell tumor hypoglycemia (NICTH). Diagnostic workup revealed malignant characteristics in which the tumor showed up as, presumably, false-negative on fluorodeoxyglucose-positron emission tomography (FDG-PET), while being positive on tyrosine-PET. Neoadjuvant treatment, which consisted of combined chemo-radiation and consecutive selective embolization of the tumor feeding vessels, caused such a therapeutic effect, on both NICTH and reduction in tumor volume, that a secondary resection, with the patient in a normoglycemic status, was possible. Our report highlights several important issues in the management of the patient with a nonresectable solitary fibrous tumor with severe episodes of hypoglycemia due to NICTH.

Clinical features of insulin-like growth factor-II producing non-islet-cell tumor hypoglycemia

In some patients with non-islet-cell tumor hypoglycemia (NICTH), a high molecular weight form of IGF-II (big IGF-II) derived from tumors is present in the circulation and might be associated with recurrent hypoglycemia. In this study, in order to survey the clinical characteristics of patients with IGF-II producing NICTH, we analyzed the medical records of 78 patients with NICTH (M/F 44/34, age 62+/-1.8, range; 9-86 years.) whose serum contained a large amount of big IGF-II. Hepatocellular carcinoma and gastric carcinoma were the most common causes of NICTH. The diameters of the tumors were more than 10 cm in 70% of the patients. Basal immunoreactive insulin (IRI) levels were less than 3 microU/dl in 79% of the patients. Hypoglycemic attack was the onset of disease in 31 of 65 cases (48%), but the tumor was revealed prior to the occurrence of hypoglycemia in 34 cases (52%). Twenty-five of 47 (53%) patients had decreased serum potassium levels. These data suggested that hypoinsulinemic hypoglycemia associated with the presence of a large tumor supports the diagnosis of IGF-II producing NICTH. Hypokalemia was associated with hypoglycemia in some patients. The BMI (21.4+/-0.6 kg/m2) and serum total protein levels (6.6+/-0.1g/dl) were preserved at the occurrence of first hypoglycemic attack suggesting that malnutrition might not be the main cause of hypoglycemia in most patients.

Deep vein thrombosis and malignancy: a surgical oncologist's perspective

Oncology patients are at increased risk of developing deep vein thrombosis (DVT) and its potentially fatal sequel, pulmonary embolism. This is due to multiple factors, including the presence of the malignancy itself, comorbid factors and therapy-related interventions. Issues that are peculiar to venous thrombosis in the oncology setting are discussed, based on a MEDLINE search of the English literature. These include the need to screen for malignancy in idiopathic DVT, a high index of suspicion for venous thrombosis in the cancer patient, the use of vena cava filters, and the anti-neoplastic effects of heparin. Asian patients appear to have a lower incidence of DVT compared to Caucasians. A recommended regimen for prophylaxis of DVT must take into account the varying thrombosis risk associated with different malignancies. Cancer patients not undergoing abdominal, pelvic or orthopaedic surgery (e.g. mastectomy) should use elastic compression stockings and be mobilized early, whereas low-molecular-weight heparin should be given to those undergoing more major surgery. In advanced malignancy, treatment of DVT palliates symptoms. These patients may need long-term anticoagulation with warfarin.

Treatment of haemangiopericytoma-associated hypoglycaemia with embolisation

A 48-year-old woman with a known history of metastatic haemangiopericytoma presented with intractable hypoglycaemia. Hypoglycaemia was accompanied by undetectable serum insulin levels with high levels of proforms of insulin-like growth factor-II ('big' IGF-II). Reduction of tumour load with embolisation resulted in a normal pattern of serum glucose levels throughout the day.

Alterations of the 11p15 imprinted region and the IGFs system in a case of recurrent non-islet-cell tumour hypoglycaemia (NICTH)

BACKGROUND AND OBJECTIVE

Non-islet-cell tumour hypoglycaemia (NICTH) is a rare disorder and has been explained by oversecretion of non mature IGF-II and dysregulation of the IGFs sytem. The mechanisms responsible for tumoural IGF-II overexpression in NICTH have been rarely studied. We report an extensive study of IGF-II and IGFBPs as well as chromosome 11p15 gene expression regulation in a case of a pleural fibrosarcoma in a 63-year-old patient presenting with NICTH.

METHODS AND RESULTS

Abnormal high molecular weight precusor forms of IGF-II were present in the patient's serum and were associated with dramatic alterations in the circulating levels of IGF-I, IGF-II and their binding proteins, as well as an inhibition of the somatotroph axis. These alterations returned to normal following complete surgical removal of the tumour. No structural change in chromosome 11p15 region was apparent in the tumour. However, dysregulation of this imprinted region was demonstrated, leading to the loss of imprinting of the IGF-II gene associated with high IGF-II expression, and by contrast decreased level of expression of H19 and p57KIP2 genes. Recurrence of the tumour four years latter was not associated with hypoglycaemia or changes in the levels of circulating IGFs or IGFBPs, despite IGF-II overexpression by the tumour. This suggests that a large tumour volume is required to reach high enough levels to cause changes in the levels of circulating IGFs and IGFBPs, and to cause hypoglycaemia.

CONCLUSION

These results suggest that a dysregulation of gene expression and imprinting of chromosome 11p15 region is associated with tumour growth and IGF-II overexpression in non-islet-cell tumour hypoglycaemia.

Hepatic and pulmonary metastases from a meningeal hemangiopericytoma and severe hypoglycemia due to abnormal secretion of insulin-like growth factor: a case report

A 42-year-old woman was hospitalized for severe hypoglycemic coma. She had a voluminous hepatic metastasis and multiple small lung metastases from a meningeal hemangiopericytoma initially operated on 11 years earlier. High blood levels of an abnormal form of insulin-like growth factor type 2 (IGF II) associated with low blood levels of insulin, growth hormone, IGF I, and IGF BP3 were observed. After surgical resection of the liver and pulmonary metastases, serum glucose levels and hormonal abnormalities returned to normal.

Gene expression and serum levels of insulin-like growth factors (IGFs) and IGF-binding proteins in a case of non-islet cell tumour hypoglycaemia

We describe a case of non-islet cell tumour hypoglycaemia (NICTH) associated with a renal cell carcinoma. Serum insulin-like growth factors (IGFs) (including IGF-II E peptide), IGF-binding proteins (IGFBPs), insulin and C-peptide were measured before and after surgical removal of the tumour. IGFBPs were visualized by Western ligand blotting. Preoperatively 'big' IGF-II and IGFBP-2 levels were raised. IGF-I, IGFBP-1 and IGFBP-3 were low, while insulin, C-peptide and GH were undetectable. These changes were reversed by 2 days postoperatively. Protease assays showed little IGFBP-3 protease activity preoperatively. Preoperatively, neutral chromatography demonstrated most of the immunoassayable IGFBP-3 in a high molecular weight form with a small amount of IGF-II. Most of the IGF-II and big IGF-II eluted in lower molecular weight forms. Postoperative samples showed a shift in IGF-II which became increasingly associated with IGFBP-3 in both low and high molecular weight complexes. By Northern blotting, expression of all species of IGF-II mRNA in the tumour was 10-fold greater than in normal human liver. The tumour did not express IGFBP-1 or IGFBP-2. IGFBP-3 was expressed in small amounts, while the expression of IGFBP-4 was two-fold higher than in liver. In conclusion, we have confirmed high levels of big IGF-II and IGFBP-2 in NICTH, changes which are reversed postoperatively. The IGF-II is derived from the tumour which overexpresses these genes but IGFBP-2 probably arises from extratumour upregulation.

Insulin-like growth factor I induces tumor hexokinase RNA expression in cancer cells

Increased glycolysis is a characteristic of cancer cells. Though less efficient in energy production, it ensures continuous supply of energy and phosphometabolites for biosynthesis enabling metastatic and less vascularized cancer cells to proliferate even under hypoxic conditions. Since hexokinase is the first rate limiting enzyme in the glycolytic pathway, elevated levels of Type II like hexokinase in tumors are of great significance in this context. Under normal conditions insulin regulates expression of hexokinase Type II isoenzyme, which is predominantly expressed in muscle. On the other hand cancer cells overexpress insulin-like growth factors and their receptors which mimic many activities of insulin. This prompted us to examine a hypothesis that insulin-like growth factors may be responsible for overexpression of tumor hexokinase. Our experiments demonstrate that insulin-like growth factor I indeed induces hexokinase gene expression in a concentration and time dependent manner in two cancer cell lines we studied.

Alterations in the promoter-specific imprinting of the insulin-like growth factor-II gene in Wilms' tumor

The human IGF2 gene, which encodes a mitogenic peptide required for normal fetal development, is overexpressed in many types of tumors. IGF2 is transcribed from four promoters (P1-P4), and in most tissues, the gene is imprinted. In this study, we have analyzed IGF2 promoter usage and determined the allelic expression from each promoter in 19 ApaI- and 22 AluI-heterozygous Wilms' tumors. Loss of IGF2 imprinting (LOI) was observed in 8 ApaI-informative tumors. In these tumors, each parental allele was expressed in equal abundance, indicating that there was complete relaxation of IGF2 imprinting. In each LOI tumor, expression from promoter P1 as well as from the normally imprinted promoters P2-P4 was biallelic. In the 11 ApaI-informative tumors which maintained IGF2 imprinting (maintenance of imprinting), transcription from promoters P2-P4 was always monoallelic, while transcripts from P1 were derived from either one or both alleles. The lack of consistency of IGF2 imprinting of promoter P1 in maintenance of imprinting tumors was also observed in normal fetal tissues of 6 12 weeks gestation, suggesting a similarity in IGF2 regulation between Wilms' tumors and embryonic tissue development. These data suggest that the increased expression of IGF2 in Wilms' tumor may be caused either by biallelic gene expression in LOI tumors from promoters P2-P4 and/or by a reversion to an earlier stage of development which is characterized by increased synthesis of this fetal growth factor.