Discrimination by RT-Nested PCR of Alpha-Lactalbumin Transcript Expression in Mammary Tumors

Alpha-lactalbumin is a protein of milk expressed by mammary epithelial cells and by some breast tumors. The alpha-lactalbumin gene has two transcripts. The expression of transcript 2 has not yet been studied. The main objective of this paper was to establish the expression profile of alpha-lactalbumin at the mRNA level and to develop a technique discriminating between the two transcripts. The study was performed on 46 fresh mammary biopsies: 17 malignant tumors, 13 benign tumors, and 16 adjacent healthy tissues. We developed an RT-nested PCR to detect LALBA gene expression without distinction between transcripts. We also designed an RT-nested PCR that detects transcript 2. Both nested PCRs avoid amplification of potentially contaminating genomic DNA. We show that benign tumors tend to appear at a young age contrarily to malignant tumors appearing later with p value = 0.002. Moreover, LALBA transcript expression varies among tissues more important in benign (69%) than in malignant (35%) tumors with significant p value = 0.041. The intensity of the bands reflected differential expression between patients with concordant data between both RT-nested PCRs. We also performed a qualitative analysis according to histopathological parameters and molecular subtypes. The expression of transcript 2 appeared associated with the HER2+ subtype, while transcript 1 was associated with the luminal A and triple-negative subtypes. In conclusion, we designed specific and sensitive methods to detect LALBA transcripts. We show for the first time a differential expression of these transcripts, but we need to confirm their potential use as markers in breast cancer.