Expression of insulin-like growth factor binding protein 2 (IGFBP-2) in Wilms' tumors

Targeting the HIF-1α-IGFBP2 axis therapeutically reduces IGF1-AKT signaling and blocks the growth and metastasis of relapsed anaplastic Wilms tumor

For patients with anaplastic Wilms tumor (WiT), metastasis and recurrence are common, and prognosis is generally poor. Novel therapies are needed to improve outcomes for patients with this high-risk WiT. A potential contributor to WiT development is constitutive activation of AKT by insulin-like growth factor 1 (IGF1) and its receptor (IGF1R) signaling pathway, but the complete underlying mechanism remains unclear. Here, we demonstrate that the hypoxia-inducible factor 1α (HIF-1α)-IGF binding protein 2 (IGFBP2) axis and the tumor-specific IGF1A are key players for constitutive activation of IGF1-AKT signaling leading to the tumor malignancy. HIF-1α and IGFBP2 are highly expressed in a majority of WiT patient samples. Deficiency of either HIF-1α or IGFBP2 or IGF1 in the tumor cells significantly impairs tumor growth and nearly abrogates metastasis in xenografted mice. Pharmacologic targeting of HIF-1α by echinomycin delivered via nanoliposomes can efficiently restrain growth and metastasis of patient-derived relapsed anaplastic WiT xenografts. Liposomal echinomycin is more potent and effective in inhibiting WiT growth than vincristine in an anaplastic WiT mouse model, and eliminates metastasis by suppressing HIF-1α targets and the HIF-1α-IGFBP2 axis, which governs IGF1-AKT signaling.

WT1 expression and hemihypertrophy in congenital mesoblastic nephroma

Congenital mesoblastic nephroma (CMN) is a rare primary pediatric renal tumor occurring predominantly in infants. There is no known association between CMN and WT1 gene expression and the association of hemihypertrophy and CMN is not well known. We report an infant with isolated hemihypertrophy and WT1-positive CMN, and the results of WT1 immunostaining in 13 other patients with CMN diagnosed over 14 years at SickKids. Of the 14 total patients 3 had positive nuclear immunostaining for WT1. Two patients also expressed WT1 RNA by reverse transcription-polymerase chain reaction. In conclusion, contrary to previous reports, WT1 may be expressed in CMN and CMN can be associated with hemihypertrophy in the absence of Beckwith-Wiedemann syndrome.

IGF-II dependent autocrine growth in cell lines derived from renal tumours of childhood

Aims-To determine the role of insulin-like growth factors (IGF) in the proliferation of tumour cells, by studying the mitogenic response to IGFs of three cell lines of differing phenotype established from both malignant rhabdoid and Wilms tumour, representing a range of cell types (GOS 4, G401, and T3/73).Methods-Production of IGF-II and IGF-I was measured by radioimmunoassay, and the presence of IGF binding protein complexes was observed by gel exclusion chromatography. Following growth analyses in serum-free media to ascertain the dependence of the cell lines on exogenous IGFs, the generation of autocrine growth was measured by a density dependence assay of proliferation in culture. Receptors were measured by radioligand cross linking and autocrine growth through these receptors assayed by the use of blocking antibodies.Results-While GOS 4 and G401 were able to proliferate in serum-free medium over a period of 5 d, T3/73 showed an absolute dependence on IGFs added daily at 1-10 ng/ml. Plating at clonal density showed that cell growth was directly density dependent in serum-free medium. The serum independent proliferation of G401 and GOS 4 was blocked by the addition of an antibody to the type 1 IGF receptor (alpha-IR3) suggesting that the effects of autocrine factors are mediated through type 1 IGF receptors. S1 nuclease protection analysis indicated that all three cell lines produced significant amounts of mRNA derived mainly from the P3 IGF-II promoter, but transcripts for IGF-I were undetectable. Radioimmunoassay of IGFs from conditioned media showed that all the lines made assayable IGF-II (8.6, 8.4, and 6.1 ng/ml/24 h/10(6) cells for GOS 4, G401, and T3/73 respectively). The presence of species consistent with both type 1 and type II IGF receptors was demonstrated using radioligand binding to cell membranes followed by cross linking.Conclusions-Autocrine IGF-II may contribute to the serum independence of GOS 4 and G401 cells, whereas T3/73 may depend on exogenous IGF-II for proliferation.