Glutathione-S-Transferase Theta 2 (GSTT2) Modulates the Response to Bacillus Calmette-Guérin Immunotherapy in Bladder Cancer Patients.

Glutathione-S-transferases (GST) enzymes detoxify xenobiotics and are implicated in response to anticancer therapy. This study evaluated the association of GST theta 1 (GSTT1), GSTT2, and GSTT2B with Mycobacterium bovis Bacillus Calmette-Guérin (BCG) response in non-muscle-invasive bladder cancer treatment. In vitro assessments of GSTT2 knockout (KO) effects were performed using cell lines and dendritic cells (DCs) from GSTT2KO mice. Deletion of GSTT2B, GSTT1, and single-nucleotide polymorphisms in the promoter region of GSTT2 was analysed in patients ( n = 205) and healthy controls ( n = 150). Silencing GSTT2 expression in MGH cells (GSTT2B FL/FL ) resulted in increased BCG survival ( p < 0.05) and decreased cellular reactive oxygen species. In our population, there are 24.2% with GSTT2B Del/Del and 24.5% with GSTT2B FL/FL . With ≤ 8 instillations of BCG therapy ( n = 51), 12.5% of GSTT2B Del/Del and 53.8% of GSTT2B FL/FL patients had a recurrence ( p = 0.041). With ≥9 instillations ( n = 153), the disease recurred in 45.5% of GSTT2B Del/Del and 50% of GSTT2B FL/FL . GSTT2 FL/FL patients had an increased likelihood of recurrence post-BCG therapy (HR 5.5 [1.87-16.69] p < 0.002). DCs from GSTT2KO mice produced three-fold more IL6 than wild-type DCs, indicating a robust inflammatory response. To summarise, GSTT2B Del/Del patients respond better to less BCG therapy and could be candidates for a reduced surveillance regimen.