UGT2B7 is not expressed in normal breast

Excerpt

It has been previously proposed that UDP-glucuronosyltransferase 2 family, polypeptide B7 (UGT2B7) is expressed in normal and cancerous breast tissue and that it plays an important protective role in the development of breast cancer [1‐7]. However, a reappraisal indicated that UGT2B7 is not expressed in breast. The original investigation [1] as well as a more recent one [8] reported UGT2B7 expression in breast on the basis of RT-PCR. However, in both cases the RT-PCR primers were improperly located in the first exon, which could not rule out the possibility of contamination from genomic DNA. We tried to replicate the above finding, but set the two primers in different exons (forward 5′-TGCTTTACTTTGACTTTTGGTTCG-3′ and reverse 5′-CCAGGAGTTTCGAATAAGCCATAC-3′). Using this strategy, the UGT2B7 transcript could not be amplified in normal breast cDNA (Fig. 1), thus indicating that this gene is not expressed or is expressed below the detectable level. This result was confirmed by real time PCR using the same primer pair in a cohort including 81 normal breast cDNA (result not shown). Since UGT2B7 was not detected also in a cell line derived from breast cancer [9], the probability that the UGT2B7 transcript is present in cancer tissues is low. UDP-glucuronosyltransferase activity on 4-hydroxyestrone (4-OH-E₁) were also detected in both normal and cancer tissues in previous report [1]. In light of the absence of UGT2B7 in breast, we proposed that this activity originates from other UGT members, especially UGT2B15, which shows relatively high glucuronidation activity on 4-OH-E₁ [9] and is highly expressed in breast [7].

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