Therapeutic targeting of B7-H1 in breast cancer.

INTRODUCTION: Breast cancer is the most common form of malignancy occurring in women worldwide. B7-H1 is a co-inhibitory molecule expressed by several types of tumors, including breast cancer. The aberrant expression of B7-H1 in breast cancer cells has been determined, its role in recruiting regulatory T cells into the tumor microenvironment has been elucidated and a strong link to B7-H1 induction in highly proliferative breast cancer has been provided. It has also been demonstrated that doxorubicin, a drug commonly used for breast cancer treatment, downregulates the cell surface expression of B7-H1 and upregulates its nuclear expression, which therefore suggests an anti-apoptotic role of B7-H1 in breast cancer. AREAS COVERED: This review illustrates the various factors involved in the induction of B7-H1 and its role in immune evasion and chemoresistance. It also provides potential therapeutic strategies for targeting B7-H1 in breast cancer. EXPERT OPINION: B7-H1 should be considered as a potential therapeutic target for breast cancer. Indeed, there is increasing evidence for the potential efficacy of B7-H1 blockade in the prevention of immune evasion by cancer cells. Additionally, B7-H1 targeting can be used in conjunction with other therapeutic modalities for improved efficacy and reduced toxicity. We expect that B7-H1 blockade in combination with other therapeutics will be a prime therapeutic strategy in the future.