Inhibin forms in serum from postmenopausal women with ovarian cancers.
OBJECTIVE
Previous studies have shown that serum inhibin as measured by alpha subunit-directed radioimmunoassay (RIA) and inhibin A ELISA was elevated in postmenopausal women with mucinous and granulosa cell cancers, with the RIA showing a more frequent elevation than the inhibin A ELISA. It was thus hypothesised that these cancers may also produce inhibin B or the free alpha subunit. The aim of the study was to identify the forms of inhibin found in a range of ovarian cancers using a range of inhibin assays with varying specificities.


METHODS
Serum samples obtained from women with ovarian cancer were assayed by inhibin B ELISA and Pro-alpha C subunit ELISA and compared with inhibin RIA and inhibin A ELISA.


METHODS
Blood samples were obtained from 34 postmenopausal women (> 55 years) with no history of endocrine disease and from women with ovarian serous cystadenocarcinomas (n = 66), mucinous cystadenocarcinomas (n = 20), granulosa cell tumours (n = 9-11), miscellaneous ovarian cancers (n = 46) and non ovarian cancers (n = 23).


METHODS
Inhibin B and inhibin Pro-alpha C subunit levels were determined by ELISA and compared to values obtained by RIA and inhibin A ELISA. Cancers were discriminated from controls based on values obtained 2SD above the geometric mean of the control values.


RESULTS
Granulosa cell tumours were detected by RIA and inhibin B ELISA (100%), Pro-alpha C ELISA (90%) and inhibin A ELISA (77%). Mucinous tumours were detected by RIA (70%), inhibin B ELISA (60%), Pro-alpha C ELISA (55%) and inhibin A (20%). Serous tumours were detected by RIA (35%) and the other assays (< 15%). Miscellaneous tumours were detected by RIA (41%) and other assays < 30%.


CONCLUSIONS
Ovarian neoplasms may produce a variety of peptides related to the inhibins, including dimeric inhibin A and B. Inhibin B is detected in more ovarian cancers than inhibin A but does not discriminate as well as the alpha subunit directed assays. The higher discrimination index obtained with the RIA compared to the Pro-alpha C ELISA suggests that assays detecting all inhibin forms containing the alpha subunit and not just those detecting the Pro-alpha C subunit will provide the most useful detection method.
Robertson
D M
DM
Prince Henry's Institute of Medical Research, Clayton, Victoria, Australia.
Cahir
N
N
Burger
H G
HG
Mamers
P
P
Groome
N
N
D000368:Aged; D000369:Aged, 80 and over; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006106:Granulosa Cell Tumor / Q000097:blood / Q000175:diagnosis*; D006801:Humans; D007265:Inhibins / Q000097:blood*; D008875:Middle Aged; D018297:Neoplasms, Cystic, Mucinous, and Serous / Q000097:blood / Q000175:diagnosis*; D010051:Ovarian Neoplasms / Q000097:blood / Q000175:diagnosis*; D010455:Peptides / Q000097:blood; D017698:Postmenopause / Q000097:blood*; D011237:Predictive Value of Tests; D029584:Prostatic Secretory Proteins; D011863:Radioimmunoassay
D010455:Peptides; D029584:Prostatic Secretory Proteins; C043076:beta-microseminoprotein; C094377:inhibin-alpha subunit; D007265:Inhibins; D005640:Follicle Stimulating Hormone