Regulatory T (Treg) cells that infiltrate tumors express proteins that can serve as targets for therapeutic antibodies, suggesting that treatments aimed at these immune cells could be a promising approach in cancer treatment.

A team led by Ronald Levy, MD, chief of his own oncology laboratory at Stanford University in Stanford, California, made this discovery while studying the role of Tregs in the growth of cancer. As the researchers reported in The Journal of Clinical Investigation, they found that when Tregs infiltrate tumors, these lymphocytes express the proteins CTLA-4 and OX40.

Mice that were injected with antibodies targeting CTLA-4 and OX-40 had smaller tumors and improved survival. In addition, this antibody treatment cleared tumors at the primary site as well as distant metastases, including brain metastases that usually evade conventional systemic therapy.

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Based on these results, Levy and colleagues proposed that rather than using monoclonal antibodies to target cancer cells systemically, the antibodies could be used to target tumor-infiltrative immune cells locally, thereby eliciting a systemic immune response.