Thioredoxin-1 as a biological predictive marker for selecting diffuse large B-cell lymphoma patients for etoposide-containing treatment.

OBJECTIVE: In diffuse large B-cell lymphoma (DLBCL), there is an unmet medical need to select patients who would benefit from intensified frontline treatments such as adding etoposide to an R-CHOP regimen. METHODS: The present work included a retrospective clinical analysis of two patient cohorts and an in vitro study. Primary biopsy samples from DLBCL patients treated with an etoposide-containing high-dose regimen (n=37) and etoposide-containing frontline treatment (n=69, R-CHOEP) were studied using immunohistochemical thioredoxin-1 (Trx1) staining. Two DLBCL cell lines expressing Trx1 were cultured and their expression was silenced using the small interfering RNA knockdown technique. Chemoresistance was tested with doxorubicin, etoposide, vincristine, prednisolone and carboplatin. RESULTS: Trx1 knockdown sensitised DLBCL cells to doxorubicin (p < 0.0001) but decreased etoposide-induced cell death (p < 0.00001). In DLBCL patients who received etoposide containing frontline treatment, low cytoplasmic Trx1 expression was associated with inferior five-year overall survival (46% vs 76%, p = 0.026) and disease-specific survival (68% vs 90%, p = 0.026). CONCLUSIONS: Strong Trx1 expression appears to increase drug resistance to doxorubicin but sensitises cells to etoposide. This implies that Trx1 expression might be the first predictive biological marker to select the patients who might benefit from adding etoposide to R-CHOP immunochemotherapy.