The insulin-like growth factor (IGF) system plays a crucial role in normal cell proliferation and malignant transformation.
1,2 It comprises IGF-I and IGF-II, the type I and type II receptors,
3 and a family of IGF binding proteins (IGFBPs) that specifically bind IGFs.
4 During the transition from the benign to the malignant state, qualitative and quantitative changes of the components of the IGF system are frequently observed. For example, increases in the type I IGF receptor are seen in human pancreatic cancer when compared with benign tissue.
5 Furthermore, IGFBP dysregulation also occurs in neuroblastoma,
6 nephroblastoma,
7 and acute lymphoblastic leukaemia,
8 among others. Thus, there is increasing evidence that IGFs and IGFBPs should be included in the panel of tumour markers used for histopathological diagnosis and serological surveillance procedures in various malignancies.
Paediatric tumours and syndromes (such as Beckwith-Wiedemann syndrome) associated with such tumours show increased IGF-II gene expression and transgenic mice overexpressing IGF-II have an enhanced risk of developing tumours.
9 Immunocytochemistry showed IGF-II in choroid plexus papillomas but not in normal human choroid plexus, suggesting that IGF-II is a useful marker for the differential diagnosis of choroid plexus papilloma.
10 IGF-II and H19, which is considered to be an oncofetal RNA and tumour suppressor gene,
11 are both imprinted genes located at 11p15. The H19 gene is expressed in tumours originating from tissues that express this gene in fetal life.
12 Thus, these factors show a tissue specific oncofetal pattern of expression.
13 In rhabdomyosarcoma, strong IGF-II mRNA expression was observed, which was inversely correlated with the degree of tumour cell differentiation. Various other soft tissue sarcomas showed no IGF-II mRNA expression and it was concluded that IGF-II is a potential new marker for differential diagnosis of rhabdomyosarcoma.
14 There is evidence indicating that IGF-II plays a pivotal role in rhabdomyosarcoma tumorigenesis.
15 Coexpression of IGF-II mRNA with the Ki-67 proliferation marker in hepatocellular carcinoma suggests that IGF-II may play an important role in the development of this particular tumour.
16 In addition, the expression of H19 is under the control of the same regulatory genes as α fetoprotein, which is a widely used tumour marker for hepatocellular carcinoma.
12 H19 was present in 13 of 18 cases, whereas staining for α fetoprotein was positive in only nine of 18 cases.
17 Earlier reports indicated that H19 gene expression in human bladder carcinomas was associated with a more malignant grade.
18 It was suggested that H19 is an oncodevelopmental marker for bladder tumour progression and that this gene has oncogenic properties in this type of tumour.
19Raised serum IGFBP-1 values have been reported in patients with primary liver cancer
20 and ovarian cancer.
21 Whether these serum concentrations of IGFBP-1 are related to tumour cachexia or to production by the tumour itself is unclear. In the serum of patients with non-islet cell tumour hypoglycaemia, free IGF-I and IGF-II, in addition to IGFBP-1 and IGFBP-2 values, are raised.
22Consistently increased concentrations of IGFBP-2 have been described in serum and cyst fluids surrounding tumours of different histology, such as lung tumours,
23 Wilms's tumours,
7 prostate cancer,
24,25 colorectal tumours,
26 ovarian cancer,
27,28 acute lymphoblastic leukaemia,
8 and brain tumours.
15Increased IGF-I and decreased IGFBP-3 concentrations are found in patients with lung cancer in comparison with control subjects, so that measuring those factors might be useful for the assessment of lung cancer risk.
29 IGFBP-2 serum concentrations were significantly increased in patients with lung cancer compared with normal controls.
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