Interleukins constitute a class of small-molecule proteins that mediate communication between immune cells and tissue cells, playing important roles in the development and progression of cancers.176 Some interleukins can promote tumor growth and metastatic spread (e.g., IL-4, IL-6, and IL-10),177–179 while others regulate immunosurveillance and thus tumor control (e.g., IL-2, IL-7 IL-12, IL-15, IL-18, IL-21, IL-23, and IL-24).180–183 Therefore, many OVs have been engineered to carry antitumoral ILs. Here, IL21 is linked to neoplasm.