Tumor Markers for Breast Carcinoma

Specific polypeptide differences in normal versus malignant breast tissue by two-dimensional electrophoresis

High resolution two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) in combination with computer-assisted densitometry was used to analyze 800-1000 silver stained postmitochrondrial and 600-800 cytosolic polypeptides extracted from malignant and nonmalignant human breast tissues. The 2D-PAGE patterns of polypeptides from malignant and normal tissues were similar, although both qualitative and quantitative polypeptide differences were noted. Six cytosolic polypeptides (pI/molecular mass x 10(-3), 5.20/80, 5.75/43, 6.20/40, 5.43/35, 5.46/34.5, and 5.50/34 were detected exclusively in malignant tissues. One constitutive polypeptide, p52 (7.25/52), was not detected in tumor samples. Marked quantitative differences in spot density were noted in polypeptides localized mainly in the molecular weight ranges of 22-40 kDa and pI of 5.65-7.00. An overall increase in polypeptide expression was noted in this region of 2D-PAGE gels of malignant tissues as compared to normal. Twenty-two acidic and 19 polypeptides separated under nonequilibrium isoelectric focusing conditions were significantly increased in tumor samples while one polypeptide was decreased. One polypeptide, p24 (6.15/24), was expressed in greatest concentrations in tumors which also expressed the greatest estrogen receptor content. Expression of p24 was markedly reduced in normal tissue and in malignant tissues expressing low levels of estrogen and progesterone receptors. No significant differences in the expression of the Yb and Ya subunits of glutathione-S-transferases (GST)-A, -B and ligandin were observed between normal and malignant breast tissue. None of the Yp subunits of the placental isoform of GST were detected in either normal or malignant breast tissues.

A rational postoperative follow-up with carcinoembryonic antigen, tissue polypeptide antigen, and urinary hydroxyproline in breast cancer patients

Breast cancer patients (n = 224) aged 28 to 81 were postoperatively followed up with serial determinations of carcinoembryonic antigen (CEA), tissue polypeptide antigen (TPA), and urinary hydroxyproline (OHP). The clinical usefulness of these tumor markers to diagnose and monitor distant metastases was compared with that of the imaging techniques commonly used to monitor breast cancer patients (bone scanning [BS], liver echography [LE], chest radiograph, and skeletal radiograph). So far, 23 patients withdrew from the study, and distant metastases occurred in 33 patients. In 91% of the metastatic patients, constant elevation or progressive increase in serum CEA and/or TPA levels were the first pathologic findings of the relapse. Of the remaining 168 nonrelapsed patients, 122 were followed up longer than 24 months (43 +/- 17 months; mean +/- SD). In these 122 patients the false-positive results of CEA, TPA, and OHP were 0.8%, 2.4%, and 0%, respectively, when used simultaneously with clinical examination and the common laboratory examinations. BS and LE are the only imaging techniques that showed such a high sensitivity to be suitable in the postoperative follow-up of breast cancer patients. Nevertheless, because BS has a low specificity and is not harmless, it should be performed at longer intervals than tumor markers. Eventually, in the relapsed patients, TPA and OHP well reflected the response to treatment better than CEA and prevented useless radiologic examinations.

Biological markers for breast carcinoma

During the last decade, there has been an intense search for biological markers for breast carcinoma. Many different types of materials have been found that may be elevated in the body fluids of patients with this disease. However, no markers specific for breast cancer have been discovered and those currently available lack the sensitivity and specificity for early detection of the disease or for determining when the tumor burden is low. Problems may also occur in the interpretation of marker data due to apparent biological variations in synthesis or secretion. Plasma carcinoembryonic antigen (CEA), elevated in 60%-70% of patients with metastases, has had the most extensive evaluation. For the latter patients with increased plasma CEA, the levels in general are proportional to tumor burden. Changes in level with therapy correlate with measurable clinical parameters of response or progression in the majority of these patients. Specific patterns of serial CEA measurements after mastectomy may be helpful for predicting those patients most likely to develop recurrent disease. More recent attention has focused on trials of combinations of markers and on tissue measurement. The search for a specific marker for breast cancer using monoclonal antibody techniques is a promising area of considerable research interest.