MEG8 as an antagonistic pleiotropic mechanism in breast cancer.

Cellular senescence connects aging and cancer. Cellular senescence is a common program activated by cells in response to various types of stress. During this process, cells lose their proliferative capacity and undergo distinct morphological and metabolic changes. Senescence itself constitutes a tumor suppression mechanism and plays a significant role in organismal aging by promoting chronic inflammation. Additionally, age is one of the major risk factors for developing breast cancer. Therefore, while senescence can suppress tumor development early in life, it can also lead to an aging process that drives the development of age-related pathologies, suggesting an antagonistic pleiotropic effect. In this work, we identified Rian/MEG8 as a potential biomarker connecting aging and breast cancer for the first time. We found that Rian/MEG8 expression decreases with age; however, it is high in mice that age prematurely. We also observed decreased MEG8 expression in breast tumors compared to normal tissue. Furthermore, MEG8 overexpression reduced the proliferative and stemness properties of breast cancer cells both in vitro and in vivo by activating apoptosis. MEG8 could exemplify the antagonistic pleiotropic theory, where senescence is beneficial early in life as a tumor suppression mechanism due to increased MEG8, resulting in fewer breast tumors at an early age. Conversely, this effect could be detrimental later in life due to aging and cancer, when MEG8 is reduced and loses its tumor-suppressive role.