Testicular germ cell tumors (TGCTs) are the commonest tumors in young men. With the advancement of chemotherapies, most TGCTs are successfully cured, even when diagnosed at an advanced and metastatic stage. However, a proportion of often young patients, median age 35-40, with advanced disease are not cured and will inevitably die. Therefore, there is an unmet need in this small population of young patients who are candidates for experimental approaches. We investigated a new therapeutic option for this group of patients, aiming to significantly improve their outcome. In recent years, many targeted therapies have been developed which demonstrated high efficacy and low toxicity. Brentuximab vedotin, a monomethyl auristatin E conjugated CD30 antibody, targets CD30 to kill cancer cells. As a large proportion of TGCTs express CD30, in particular embryonal carcinomas, we investigated in vitro the efficacy of brentuximab vedotin in treating TGCTs as a single therapy and in combination with commonly used chemotherapy drugs. We determined CD30 expression levels in 12 TGCT cell lines, including three cisplatin resistant sublines. In general, the efficiency of cancer cell inhibition by brentuximab vedotin correlates with CD30 expression, but there were some exceptions. We also determined the efficacy of brentuximab vedotin in combination with commonly used chemotherapy drugs and found synergistic/additive effects with etoposide, paclitaxel and SN-38. However, cisplatin, the most commonly used chemotherapy drug in TGCT treatment, exhibited antagonism and we showed that cisplatin selectively kills CD30 positive cells. We also found that certain agents, which have been reported to induce CD30 expression in other human malignant diseases, including DNA demethylation drugs, methotrexate and CD30 ligands, were unable to enhance CD30 expression or brentuximab vedotin efficacy in TGCT cells. This study will help to design clinical trials using brentuximab vedotin for the treatment of TGCTs, either as a single agent or in combination with current clinical therapies.
Keywords: CD30 expression; Testicular germ cell tumor; brentuximab vedotin; chemotherapy; cisplatin; drug combination.