Gene therapy for relapsed breast cancer

Gene therapy for advanced breast cancer is anticipated to be a useful therapeutic approach. Strategies in ongoing clinical protocols can be divided into four groups: (1) suppression of oncogenes or transfer of tumor-suppressor genes: (2) enhancement of immunological response: (3) transfer of suicide genes: (4) protection of bone marrow using drug resistance genes. We have started a clinical study of multidrug resistance (MDR1) gene therapy. Patients received high dose chemotherapy and autologous peripheral blood stem cell transplantation (PBSCT) with MDR1-transduced hematopoietic cells, and then were treated with docetaxel. Three patients have been treated so far, and in vivo enrichment of MDR1-transduced cells with docetaxel treatment has been seen. There has been no apparent adverse effect from the MDR1 gene transfer.