This is a pretty cool study with some interesting findings! Cancer immunotherapy has a long history but has become very prominent in recent years. (Fun fact: the senior author on this paper, Ed Engleman, co-founded of one of the first cancer cell therapy companies, Dendreon, in the early 90s). However, the success of immunotherapies has been limited by the immune-exclusionary nature of the tumor microenvironment (TME). Why some tumors are immune-hot and others are immune-cold is still a very open research question.

In this study, the authors demonstrate pretty convincingly that erythropoietin (EPO, a hormone that stimulates red blood cell production in the bone marrow) reduces the recruitment of tumor-cell-killing T cells to the TME. It does this by acting on tumor macrophages, another type of immune cell, and changes the state of these cells to facilitate accumulation of immunosuppressive cells.

They work out the mechanism largely through mouse models and associative analysis in human tissue samples, but I thought it was interesting that this finding aligns with the clinical observation that cancer patients who receive recombinant EPO for treatment of anemia frequently experience tumor progression.

After reading this, I am going back to check out EPO expression in old datasets that I worked with haha.