Body mass index and γ-glutamyl transferase expression in normal and cancerous breast tissue

Localized to cell membrane, γ-glutamyl transferase (GGT) is a reliable marker for the evaluation of cell distress occurring in several pathological conditions including obesity, metabolic syndrome, and cancer. In particular, high GGT serum levels are associated with breast cancer incidence and progression.

The tissue expression of GGT1, the gene coding for GGT, was investigated in silico in a large case series of paired samples of breast cancer and adjacent histologically normal (HN) tissue, and in a collection of healthy breast tissues from reduction mammoplasty. The association of GGT1 with patient's body mass index (BMI), and the relationship between GGT1 and a panel of genes involved in apoptosis, IGF-1 signaling, or coding for adipokines and adipokine receptors were also investigated.

GGT1 expression was significantly higher in tumor than in the adjacent HN tissue (P = 0.0002). Unexpectedly, the expression of GGT1 was inversely associated with BMI in normal and HN tissue, whereas no correlation was found in cancerous tissue. In all tissues, GGT1 correlated positively with TP53 and negatively with BCL2 and LEPR, whereas only in normal and HN tissue GGT1 correlated positively with IGF1R. The linear regression model, adjusted for BMI, showed no confounding effect on any correlation, except for the correlation of GGT1 with LEPR in normal tissue from healthy women.

Even if present results provide interesting insights on the still elusive mechanism(s) underlying the association between obesity and epithelial cell proliferation, possibly promoting neoplastic transformation, such relationship deserves further investigation in other independent datasets.