CD8A and neoplasm: Importantly, according to the low half-life of ATP, which is rapidly converted into adenosine via the activation of CD39 and CD73 and highly expressed on regulatory T cells (T regs) and CD8+-exhausted T cells, it is likely that this TME facilitates the immunosuppressive adaptive immunity in that the accumulation of T regs and regulatory B cells (B regs) can support tumor cell proliferation rather than eradication, as observed for lung and breast tumor models [33].