The immunomodulatory effects of pegylated liposomal doxorubicin are amplified in BRCA1--deficient ovarian tumors and can be exploited to improve treatment response in a mouse model.

ABSTRACT

OBJECTIVE: Women with BRCA-associated ovarian cancer demonstrate excellent responses to Pegylated Liposomal Doxorubicin (PLD). PLD has also been shown to enhance T cell recognition of tumor cells. Here we characterize immunophenotypic changes associated with BRCA1 dysfunction in ovarian cancer cells, and evaluate the T cell contribution to the therapeutic efficacy of PLD in a BRCA1- ovarian cancer model to determine whether enhanced anti-tumor immunity contributes to the improved response to PLD in BRCA1- ovarian cancers. METHODS: The immunophenotype of BRCA1- and wild-type (WT) ovarian cancer cells and their response to PLD were compared in vitro using flow cytometry. T cell recruitment to BRCA1- tumors was evaluated with flow cytometry and immunohistochemistry. The contribution of T cell populations to the therapeutic effect of PLD in a BRCA1- model was evaluated using immunodepleting antibodies with PLD in vivo. RESULTS: The cytotoxic response to PLD was similar in BRCA1- and WT cells in vitro. BRCA1- inactivation resulted in higher expression of Fas and MHC-I at baseline and after PLD exposure. PLD prolonged the survival of BRCA1- tumor bearing mice and increased intratumoral T cell recruitment. CD4+ depletion combined with PLD significantly prolonged overall survival (p=0.0204) in BRCA1- tumor-bearing mice. CONCLUSION: Differences in the immunophenotype of BRCA1- and WT cells are amplified by PLD exposure. The enhanced immunomodulatory effects of PLD in BRCA1- tumors may be exploited therapeutically by eliminating suppressive CD4+ T cells. Our results support further study of combination therapy using PLD and immune agents, particularly in women with BRCA gene mutations.