Carbohydrate antigens Lewis a and Lewis b act as tumor markers cooperating with CA19.9 in the management of PDAC patients.

BACKGROUND

CA19.9 is the unique marker recommended for the preoperative staging and the follow-up of patients suffering from pancreatic ductal adenocarcinoma (PDAC) but up to 30% of PDAC patients maintain normal CA19.9 values and cannot be monitored in this way. Lewis a (Lea Galβ1,3[Fucα1,4]GlcNAc) and b (Leb, Fucα1,2Galβ1,3[Fucα1,4]GlcNAc) are antigens which are structurally similar to sialyl-Lewis a (Siaα2,3Galβ1,3[Fucα1,4]GlcNAc), the epitope of CA19.9.

METHODS

We set an ELISA procedure determining the levels of Lea, Leb, and CA19.9 in the blood of healthy individuals or PDAC patients. Moreover, such antigens were also detected in cancer resections by immunofluorescence microscopy, and the levels of glycosyltransferase transcripts involved in Lewis antigen biosynthesis were determined by RT-qPCR.

RESULTS

In our cohort of 116 healthy individuals, the distribution of circulating Lea and Leb was similar to that of CA19.9, allowing us to set putative cutoff values for both antigens. In a cohort of 115 PDAC patients, the differential distribution with respect to the controls was statistically significant for both antigens (p < 0.001). Out of 37 patients presenting normal CA19.9 values, 15 patients presented Lea or Leb above the cutoffs. By immunofluorescence, Lea, Leb and CA19.9 were all detected in cancer resections and expression levels were heterogeneous among patients in terms of intensity, localization and diffusion. The levels of relevant glycosyltransferase transcripts were found to be heterogeneous between cancers of different patients and no association was detectable with the levels of any circulating antigen.

CONCLUSIONS

The concurrent quantification of Lea and Leb together with CA19.9 improves the management of PDAC patients.