The invention is based on the disclosure provided herein that secondary lymphoid organ chemokine (SLC) inhibits the growth of syngeneic tumors in vivo. Thus, the invention provides a method of treating cancer in a mammal subject by administering a therapeutically effective amount of an SLC to the mammal in combination with a checkpoint inhibitor, including monoclonal antibodies and small molecule inhibitors. Exemplary checkpoint molecules include CTLA-4, a CTLA-4 receptor, PD-1, PD1-L1, PD1-L2, 4-1BB, OX40, LAG-3, TIM-3 or a combination thereof. SLCs useful in the methods of the invention include SLC polypeptides, variants and fragments and related nucleic acids.