High molecular weight forms of IGF-II ('big-IGF-II') released by Wilms' tumor cells

Abstract

Insulin-like growth factor-II (IGF-II) is thought to play a critical role in the development of embryonic tumors such as Wilms' tumor. However, despite highly elevated IGF-II mRNA levels in tumors, IGF-II is not elevated in the serum of patients with Wilms' tumors. Recently high molecular weight forms of IGF-II ('big'-or pro-IGF-II) have been found to be produced by some tumors. In order to prove whether or not high molecular weight forms of IGF-II are produced by Wilms' tumor cells and secreted into the culture medium, we established Wilms' tumor cell lines. After column chromatography of the culture medium, IGF-II and pro-IGF-II concentrations were measured. For pro-IGF-II measurement we established a pro-IGF-II RIA using a rabbit polyclonal antiserum directed against amino acids 7-21 (E 7-21 ) of the E-domain of pro-IGF-II. Gel electrophoresis and Western blotting with anti-IGF-II antibodies revealed a band at 7.5 kDa corresponding to fully processed IGF-II and bands between 10 and 20 kDa. Using pro-IGF-II antiserum, bands between 10 and 25 kDa were detected. We conclude that in vitro cultured Wilms' tumor cells produce and release various forms of 'big IGF-II' with molecular masses between 10 and 25 kDa. It remains uncertain whether these high molecular weight forms of IGF-II represent normal precursors of IGF-II or incorrectly processed IGF-II.

Inhibition of growth, production of insulin-like growth factor-II (IGF-II), and expression of IGF-II mRNA of human cancer cell lines by antagonistic analogs of growth hormone-releasing hormone in vitro

“…To assess the involvement of the antagonists in blocking the IGF-II autocrine regulatory pathway in tumor cells, in vitro experiments were performed. Previous studies reported IGF-II production in several tumors including sarcomas, adrenal, kidney, or brain tumors, as well as pancreatic and prostatic cancers (1,4,23,24,27,28). To extend this list, we tested 26 human cancer cell lines for IGF-II production in vitro.…”

“…ion (1,2,4,(27)(28)(29)(30)(31)(32)(33). Interrupting the autocrine regulatory circle of IGF-II could provide an efficacious approach to inhibiting various cancers.…”

Insulin‐like growth factor‐II and bioactive proteins containing a part of the E‐domain of pro‐insulin‐like growth factor‐II

“…In addition to the circulation, high MW forms of IGF-II have also been found in the brain, cerebrospinal, amniotic, and seminal fluids, tumor cyst fluid, and in the conditioned medium of several cell types. 47,[50][51][52][53][54]…”

Myelination Is Altered in Insulin-Like Growth Factor-I Null Mutant Mice

“…The ϳ7.5 kDa comigrates with recombinant IGF-II and represents mature IGF-II, whereas the more abundant bands migrating at ϳ12 kDa likely represent precursor forms. Precursor IGF-II forms of 10 -18 kDa have been reported in multiple tumor cells lines (Schmitt et al, 1997;Bae et al, 1998) and in the serum of normal and tumor patients (Hoeflich et al, 1995;Bae et al, 1998;Christofilis et al, 1998). The expression of IGF-II in developing and adult rodent CNS has been well studied using a variety of methods, including immunohistochemistry (Logan et al, 1994;Walter et al, 1999), in situ hybridization (Cavallaro et Logan et al, 1994;Walter et al, 1999), and RNA protection assay (Rotwein et al, 1988); however, only a few studies have documented its molecular forms in brain (Haselbacher et al, 1985).…”