Mucin-like carcinoma-associated antigen (MCA) during normal pregnancy

Cross-reactivity between MUC1 antigen and MCA: false elevation of serum CA 15-3 level in pregnant and lactating women by Ma695-Ma552-based assay

PURPOSE

Cancer antigen 153 (CA 15-3) is one of the most commonly used biomarkers of breast cancer. However, elevated CA 15-3 is reported in pregnant and lactating women more frequently on Beckman DxI 800 immunoassay system (Ma695-Ma552 antibody pair) than on Abbott ARCHITECT system (115D8-DF3 antibody pair) in laboratory methodological evaluation. We conducted this study in order to figure out the reason behind this phenomenon.

METHODS

Serum CA 15-3 concentration was analyzed in 426 subjects, including 180 patients with breast cancer, 121 patients with benign breast disease, and 125 healthy volunteers (45 pregnant and 80 non-pregnant women). CA 15-3 assay was further validated using another cohort of 112 pregnant or postpartum women. Immunological cross reaction was analyzed by Western blotting and immunoprecipitation.

RESULTS

The serum CA 15-3 level was abnormally higher in almost 95% of the pregnant and lactating women detected using Ma695-Ma552 antibody pair (median: 71.4 U/mL) than that detected using 115D8-DF3 antibody pair (median: 16.5 U/mL). Western blotting and immunoprecipitation indicated that such a significant difference was mainly due to the cross reaction between monoclonal antibody Ma552 and mucin-like carcinoma-associated antigen (MCA).

CONCLUSIONS

The CA 15-3 assay using 115D8-DF3 antibody pair is more suitable for monitoring therapy in pregnancy-associated breast cancer.

Tumor Markers In Biological Fluids Associated With Pregnancy

Proteins that are expressed by both malignant and healthy fetal tissues are recognized as oncofetal. These antigens are associated with cell proliferation and differentiation and are produced in high concentrations in pregnancy and malignancy. Their biological role in malignancy is the suppression of the host's immune system, while in pregnancy they affect the maternal immune response, generating maternal tolerance toward the embryo. This review describes the levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), carcinoembryonic antigen (CEA), cancer antigen 125 (CA 125), squamous cell carcinoma antigen (SCC), cancer antigen 15-3 (CA 15-3), mucin-like carcinoma-associated antigen (MCA), tissue polypeptide-specific antigen (TPS), carbohydrate antigen 19-9 (CA 19-9), and prostate-specific antigen (PSA) in maternal serum (MS), umbilical cord serum (UC), and amniotic fluid (AF) and outlines their roles in the assessment of pregnancy and malignancy. All antigens studied, except CA 15-3, are oncofetal. The presence of considerable concentrations of AFP, hCG, CEA, CA125, SCC, MCA, TPS, CA 19-9, and PSA in AF during pregnancy may be attributed to their involvement in biological functions associated with fetal development, differentiation, and maturation. MS CEA, CA 15-3, and CA 19-9, in contrast to all the others, are not influenced significantly by pregnancy and thus remain reliable tumor markers in monitoring malignancy in pregnant patients.

Mucin-like carcinoma-associated antigen in paired serum and breast milk samples of lactating mothers and sera of their neonates in the early postpartum period

OBJECTIVE

To evaluate postpartum MCH changes in the early postpartum period, and to examine whether neonatal MCA is related to that in maternal serum (MS) or milk.

STUDY DESIGN

MCA was measured by EIA on the second and fifth postpartum day in serum and BM from 30 lactating women and their single term neonates. Sera from 20 healthy women (controls), were also analyzed.

RESULTS

All neonatal antigen concentrations were below the cut-off level for MCA (11 ng/ml). MS MCA was significantly increased compared with that in controls (P<0.00001), while antigen values in BM were highly elevated (P<0.00001), with a significant increase (P<0.0003) from the second to the fifth postpartum day. A strong correlation was found between the second and fifth day postpartum samples in MS, neonatal serum and BM MCA concentrations (r(s)=0.94, P<0.00001; r(s)=0.75, P<0.00001 and r(s)=0.69, P<0.0001, respectively). A significant correlation was also found in MCA values on the fifth postpartum day between neonatal serum and BM (r(s)=0.54, P<0.02).

CONCLUSIONS

From these findings one may speculate on some ripening process in milk production and a possible transition of MCA from the neonatal gastro-intestinal tract into circulation.