Response of glutathione S-transferase Pi (GSTP1) to neoadjuvant therapy in rectal adenocarcinoma

The response of rectal adenocarcinoma to neoadjuvant therapy is variable. Accurate prediction of response would enable selective administration of therapy. The enzyme glutathione S-transferase Pi (GSTP1) has been shown to influence response to therapy in some solid tumours. Few data are available for rectal cancer.

The GSTP1 levels in rectal adenocarcinoma and adjacent normal mucosa were quantified before and after exposure to neoadjuvant therapy. Venous blood samples and biopsies of normal rectal mucosa and tumour were prospectively obtained from patients with primary rectal cancer. Patients were stratified by exposure to neoadjuvant therapy or surgery alone. GSTP1 was quantitatively measured using an enzyme-linked immunosorbent assay.

Ninety-two patients (54 men; median age 68 years) were recruited. The median GSTP1 level was significantly higher in rectal adenocarcinoma than in matched normal mucosa [6.59 μg/mg vs 4.57 μg/mg; P < 0.001]. The median tumour GSTP1 level was significantly lower in the therapy group compared with unmatched samples from the no-therapy group [4.47 μg/mg vs 7.76 μg/mg; P < 0.001].

The GSTP1 level is increased in rectal adenocarcinoma compared with adjacent normal mucosa. It decreases following neoadjuvant therapy. Future studies correlating pre-therapy GSTP1 levels with pathological response would be of interest.