The evaluation of disseminated epithelial
tumor cells in patients with early stages of
breast cancer has generated considerable interest because of its potential association with poor clinical outcome. Considering that O-glycosylation pathways are frequently altered in
breast cancer, we performed this work to evaluate the potential usefulness of
UDP-
N-acetyl-D-galactosamine:
polypeptide N-acetylgalactosaminyltransferases (ppGalNAc-Ts) (a family of
glycosyltransferases which catalyze the first key step of
mucin-type O-glycosylation) to detect disseminated cells in bone marrow samples from patients with operable
breast cancer. Using RT-PCR assays, we studied the gene expression of 9
enzymes (ppGalNAc-T1-T9). Among the ppGalNAc-Ts expressed by
breast tumors (-T1, -T2, -T3, -T6 and -T7), the best specificity (negative results on all PBMN cell samples from healthy donors) was shown for ppGalNAc-T6. Thus, we selected this
enzyme as a target gene for further evaluation. ppGalNAc-T6
mRNA was found in 22/25 (88%)
breast cancer samples, in all 3 human
breast cancer cell lines evaluated (MCF-7, ZR75-1 and T47D), in 1/30 (3%) PBMN cells and 0/19 bone marrow samples obtained from patients without
cancer. Using this method, 22/61 (36%) patients with
breast cancer, who underwent curative surgery, showed positive ppGalNAc-T6
mRNA in bone marrow aspirates obtained prior to surgery, including 11/34 patients with stage-I or -II, without histopathological lymph node involvement. In a preliminary follow-up evaluation, 19/61 patients experienced recurrence of the disease. ppGalNAc-T6 was positive in 11/19 (57.9%) of these patients. Interestingly, in the group of patients without lymph node involvement, disease recurrence was observed in 54.5% of patients who showed ppGalNAc-T6
mRNA-positive bone marrow aspirates and only in 4.3% of patients when ppGalNAc-T6 was negative (p = 0.014). These results indicate that ppGalNAc-T6
mRNA could be a specific marker applicable to the molecular diagnosis of
breast cancer cells dissemination.