The present disclosure provides methods of preparing tumor infiltrating cells engineered to express a pro-inflammatory polypeptide. The pro-inflammatory polypeptide is expressed from the tumor infiltrating cell to counter a generally immunosuppressive state in and around tumors resulting from an imbalance between the number and activation state of immune effector cells versus those of suppressor cells. Delivering the proinflammatory polypeptide via expression from the TICs, as distinct from systemic administration, reduces side effects from increased inflammation at sides remote from a tumor to be treated.