A rapid method for analyzing serum pro-insulin-like growth factor-II in patients with non-islet cell tumor hypoglycemia.
BACKGROUND
Non-islet cell tumor hypoglycemia (NICTH) results from the hypersecretion of pro-IGF-II by a large, usually mesenchymal tumor. Detection of pro-IGF-II in serum is a potential tumor marker in these patients.


OBJECTIVE
The aim of this study was to validate a rapid and reliable method for determining serum pro-IGF-II.


METHODS
Serum samples from 16 patients with NICTH were studied.


METHODS
The main outcome measure was serum concentration of pro-IGF-II determined by immunoblot analysis of pro-IGF-II and mature IGF-II after 16.5% tricine-SDS-PAGE, which was compared with pro-IGF-II measured by standard RIA after size-exclusion acid chromatography.


RESULTS
The analyses of patients' sera by size-exclusion acid chromatography showed that 68 +/- 19% of IGF-II were present in the pro-IGF-II form, whereas only 18 +/- 4% corresponded to pro-IGF-II in controls. Scanning densitometry of immunoblots showed 67 +/- 16% in the bands corresponding to pro-IGF-II in patients' sera, compared with 27 +/- 9% in controls. The detection sensitivity of tricine-SDS-PAGE method was the same as for size-exclusion chromatography, but the tricine-SDS-PAGE method is quicker and requires smaller amounts of serum.


CONCLUSIONS
Tricine-SDS-PAGE followed by IGF-II immunoblot analysis provides a rapid, reproducible, and sensitive method for the separation of serum pro-IGF-II from mature IGF-II and is a useful laboratory evaluation of patients with a clinical diagnosis of NICTH.
Miraki-Moud
Farideh
F
Department of Endocrinology, 51-53 Bartholomew Close, St. Bartholomew's Hospital, London EC1A 7BE, United Kingdom.
Grossman
Ashley B
AB
Besser
Michael
M
Monson
John P
JP
Camacho-Hübner
Cecilia
C
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015153:Blotting, Western; D002850:Chromatography, Gel; D005260:Female; D006801:Humans; D007003:Hypoglycemia / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D007335:Insulin-Like Growth Factor II / Q000032:analysis; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000097:blood*; D011498:Protein Precursors / Q000097:blood*
D011498:Protein Precursors; C066038:proinsulin-like growth factor II; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II