Modulation of bone morphogenic protein signaling in T-cells for cancer immunotherapy

Abstract

Immunotherapy is becoming an increasingly attractive therapeutic alternative for conventional cancer therapy. In recent years Foxp3⁺ regulatory T-cells (T_R) were identified as the major obstacle to effective cancer immunotherapy. The abundance of these cells in peripheral blood is increased in patients with multiple types of cancer and their prevalence among tumor-infiltrating lymphocytes correlated with poor clinical prognosis. In contrast, removal or inactivation of T_R cells led to enhanced anti-tumor immune response and better efficacy of cancer vaccines. This study reports that Bone Morphogenic Protein Receptor 1α (BMPR1α, Alk-3) is expressed by activated effector CD4⁺ and T_R cells and modulates functions of both cell types. Bone Morphogenic Proteins (BMPs) belong to the transforming growth factor (TGF)-β family of cytokines that also include TGFβ and activins. BMPs play crucial roles in embryonic development, tissue differentiation and homeostasis, and development of cancer. It was demonstrated that BMPs and activins synergize with TGFβ to regulate thymic T-cell development, maintain T_R cells, and control peripheral tolerance. Inactivation of BMPR1α in T-cells results in impaired thymic and peripheral generation of T_R cells. BMPR1α-deficient activated T-cells produced a higher level of interferon (IFN)-γ than BMPR1α-sufficient T-cells. Moreover, transplanted B16 melanoma tumors grew smaller in mice lacking expression of BMPR1α in T-cells and tumors had few infiltrating T_R cells and a higher proportion of CD8⁺ T-cells than wild-type mice.

• Bone morphogenic protein
• cancer
• gene expression
• immunotherapy
• regulatory T-cells

Acknowledgements

We thank L. Ignatowicz and members of his laboratory for reading the manuscript and helpful discussions and Jeanene Pihkala for cell sorting. This research was funded by NIH grant R21 AI097600 to P.K.