Antibody-activation of connexin hemichannels in bone osteocytes with ATP release suppresses breast cancer and osteosarcoma malignancy

Bone tissue represents the most frequent site of cancer metastasis. We developed a hemichannel-activating antibody, Cx43-M2. Cx43-M2, directly targeting osteocytes in situ, activates osteocytic hemichannels and elevates extracellular ATP, thereby inhibiting the growth and migration of cultured breast and osteosarcoma cancer cells. Cx43-M2 significantly decreases breast cancer metastasis, osteosarcoma growth, and osteolytic activity, while improving survival rates in mice. The antibody’s inhibition of breast cancer and osteosarcoma is dose dependent in both mouse and human cancer metastatic models. Furthermore, Cx43-M2 enhances anti-tumor immunity by increasing the population and activation of tumor-infiltrating immune-promoting effector T lymphocytes, while reducing immune-suppressive regulatory T cells. Our results suggest that the Cx43-M2 antibody, by activating Cx43 hemichannels and facilitating ATP release and purinergic signaling, transforms the cancer microenvironment from a supportive to a suppressive state. Collectively, our study underscores the potential of Cx43-M2 as a therapeutic for treating breast cancer bone metastasis and osteosarcoma. [Display omitted] •Developed Cx43-M2 antibody that activates Cx43 hemichannels in osteocytes•Cx43-M2 reduces breast cancer and osteosarcoma cell growth and improves survival rates•Cx43-M2 enhances anti-tumor immunity by activating Tc cells while suppressing Treg cells•ATP release by hemichannels and purinergic signaling inhibits tumor and enhances immunity Riquelme et al. report that the M2 antibody opens Cx43 hemichannels in bone osteocytes, releasing ATP. This activates P2X7R, inhibiting cancer cell growth and migration, as well as metastasis of breast cancer and osteosarcoma. Additionally, it enhances anti-tumor immunity by elevating tumor-infiltrating T effector cells and reducing immune-suppressive Treg cells.