The present invention relates to methods for treating and/or preventing cancer. In particular the present invention relates to ex vivo immunotherapeutic methods. The methods comprise decreasing Stat3 (signal transducer and activator of transcription3) expression and/or function in tumor cells and the administration of such cells to a subject in need of treatment and/or prevention. Other methods of the invention comprise activating T-cells by co-culturing the T-cells with the tumor cells with decreased Stat3 expression or function. The invention further encompasses methods comprising decreasing Stat3 expression or function in antigen-presenting cells and co-administering tumor cells and the antigen-presenting cells with decreased Stat3 function to a patient. The invention further relates to methods for stimulating dendritic cell differentiation.