Quantification of creatine kinase BB isoenzyme in tumor cytosols and serum with an ultrasensitive time-resolved immunofluorometric technique.
OBJECTIVE
To develop a highly sensitive immunofluorometric procedure for creatine kinase BB isoenzyme and use it to measure CK-BB in tumor cytosolic extracts and serum of cancer patients and healthy volunteers.


METHODS
For assay development, we used two monoclonal antibodies in combination with time-resolved fluorometry and the biotin-avidin system. We measured CK-BB in breast tumor cytosols and studied its association with steroid hormone receptors. We also measured CK-BB in the serum of healthy subjects and patients with prostate cancer. We have examined the molecular weight of CK-BB in serum using high performance liquid chromatography.


RESULTS
The evaluation of the method revealed good precision and accuracy. Study of 336 breast tumor cytosols and 9 normal breast cytosols has shown that CK-BB is overexpressed by 95% of breast tumors and that CK-BB is present in its 80 kDa form. A close association between CK-BB and estrogen but not progesterone receptors was found, suggesting that CK-BB overexpression is another marker of estrogen sensitivity of these tumors. Previous studies, using CK-BB radioimmunoassay could not detect CK-BB in the serum of about 50% of healthy subjects. We have assessed CK-BB levels in 80 male volunteers, detected CK-BB in all sera and provided a detailed distribution of values. We further demonstrated that 30% of prostate cancer patients in remission (PSA < 0.4 microgram/L) post radical prostatectomy and 50% of patients with active prostate cancer (PSA > 20 microgram/L) have elevated serum CK-BB levels. The patients with highly elevated CK-BB also had highly elevated serum PSA. We have demonstrated that some patients who have elevated serum CK-BB also have macromolecular CK complexes in their serum with molecular weights of 700 and 350 kDa as well as the 80 kDa CK-BB isoenzyme. Only the latter was recognized by the assay developed.


CONCLUSIONS
CK-BB is a marker of estrogen sensitivity in breast cancer; Patients with prostate cancer have elevated CK-BB in their serum; The new highly specific and sensitive assay may be further used to study the role of CK-BB in various malignancies.
Zarghami
N
N
Department of Clinical Biochemistry, Toronto Western Division, Toronto Hospital, Ontario, Canada.
Yu
H
H
Diamandis
E P
EP
Sutherland
D J
DJ
D000367:Age Factors; D001943:Breast Neoplasms / Q000201:enzymology*; D002851:Chromatography, High Pressure Liquid; D003402:Creatine Kinase / Q000032:analysis* / Q000097:blood; D003600:Cytosol / Q000201:enzymology; D005260:Female; D015200:Fluoroimmunoassay / Q000379:methods*; D006801:Humans; D007527:Isoenzymes; D008297:Male; D011471:Prostatic Neoplasms / Q000201:enzymology*; D011960:Receptors, Estrogen / Q000032:analysis; D012680:Sensitivity and Specificity
D007527:Isoenzymes; D011960:Receptors, Estrogen; D003402:Creatine Kinase