Gene therapy for breast cancer

Breast cancer is sensitive to chemotherapy and endocrine therapy, but the prognosis of advanced or relapsed breast cancer is unsatisfactory. Gene therapy is promising as another useful therapeutic approach for advanced breast cancer. Strategies of gene therapy for breast cancer in ongoing clinical protocols can be divided into four: (1) suppression of oncogenes or transduction of tumor suppressors; (2) enhancement of immunological response to cancer cells; (3) transduction of suicide genes; and (4) protection of bone marrow using drug resistance genes. We have started a clinical study of gene therapy for breast cancer using multidrug resistance gene (MDR1), in which advanced or relapsed breast cancer patients received high dose chemotherapy and autologous peripheral blood stem cell transplantation (PBSCT) with MDR1-transduced hemopoietic cells, and then were treated with docetaxel. Two patients have been treated so far, and in vivo enrichment of MDR1-transduced cells with docetaxel treatment after PBSCT was seen in both cases. Both patients are in complete remission and have no apparent adverse effect from MDR1 gene transduction.