Antigen specific memory T cells and their putative need for the generation of sustained anti-tumor responses

Memory T-cell responses to cancer antigens may be an effective way to sustain long-term tumor-free survival. However, finding an effective vaccination strategy to induce memory T-cell responses toward tumor associated antigens in patients with existing disease has proven to be extremely difficult. Immune stimulation regimens have been combined with tumor vaccination in an attempt to boost the immune response resulting in better vaccine efficacy. In these instances immune stimulation alone has shown some promise as a primary tumor therapy, but has been less effective at eliciting long-term tumor immunity. Likewise, combining systemic adjuvant therapy with tumor antigen vaccination also demonstrated a lack of sustained anti-tumor immunity in cancer patients. In this review, we discuss whether the immune response generated during immune stimulation is appropriate for supporting memory T-cell generation or whether initial tumor regression and generation of sustained anti-tumor immunity have different immunological signaling requirements.