The present application provides methods and compositions for treating cancers (such as solid tumors) using a recombinant oncolytic virus encoding a sialidase. In some embodiments, the oncolytic virus further encodes one or more other heterologous proteins. In some embodiments, the recombinant oncolytic virus is delivered via an engineered immune cell. In some embodiments, the present application provides methods and compositions for treating cancers using a recombinant oncolytic vims encoding a sialidase or another heterologous protein and an engineered immune cell (e.g., a CAR-T, CAR-NK, or CAR-NKT cell) expressing a chimeric receptor capable of binding to the sialidase or other heterologous protein.