CA19-9 epitope a possible marker for MUC-1/Y protein

It has been reported that MUG-I molecules devoid of the tandem repeat regio n (MUC-1/Y) are detected preferentially in carcinoma cells and are associat ed with their progression. However, its clinical significance is still unkn own. We constructed a mouse colon adenocarcinoma cell line (MC-38) transduc ed with either MUC-1/Y cDNA defecting the tandem repeat region (Y-MC-38) or MUC-1/R cDNA containing ten tandem repeats (R-MC-38). RT-PCR of mRNAs deri ved from Y-MC-38 cells using the specific primers to MUC-1/Y mRNAs, proved the existence of 600 bp RT-PCR products generated only from MUC-1/Y mRNAs. DF3 and CA19-9 epitopes out of the MUG-1-related tumor-associated antigens, have been reported to be involved in the prognosis of cancer patients. We examined the expression of DF3 and CA19-9 epitopes on Y-MC-38 and R-MC-38 c ells. Fluorescence-activated cell sorting (FACS) analysis of R-MC-38 and Y- MC-38 cells using two monoclonal antibodies against DF3 (mAb DF3) and CA19- 9 (mAb CA19-9) epitopes revealed that R-MC-38 cells expressed DF3 but not C A19-9 [DF3(+)CA19-9(-)], while Y-MC-38 cells expressed CA19-9 but not DF3 [ DF3(-)CA19-9(+)]. On Western blot, a 40 kDa protein product was recognized by mAb CA19-9 but not by mAb DF3 on cell lysates of Y-MC-38 cells, whereas a 70 kDa protein product was recognized by mAb DF3 but not by mAb CA19-9 on the cell lysates of R-MC-38. Further, we analyzed the expression of MUC-1/ Y mRNAs by RT-PCR on various human cancer cell lines: the gastric cancer ce ll line AZ521, the pancreatic cancer cell lines PANC-1 and Capan-1, the gal l bladder cell line GBK-1, the breast cancer cell line MCF-7, and the colon cancer cell lines HT-29 and Colo205. HT-29 and Capan-1 cells producing the 600 bp RT-PCR product, were positive for mAb CA19-9. These results demonst rate that CA19-9 epitope is produced only on MUC-1/Y core protein, suggesti ng that CA19-9 epitope may be a specific marker for MUC-1/Y protein.