Potential of memory T cells in bridging preoperative chemoradiation and immunotherapy in rectal cancer

The management of locally advanced rectal cancer has passed a long way of developments, where total mesorectal excision and preoperative radiotherapy are crucial to secure clinical outcome. These and other aspects of multidisciplinary strategies are in-depth summarized in the literature, while our mini-review pursues a different goal. From an ethical and medical standpoint, we witness a delayed implementation of novel therapies given the cost/time consuming process of organizing randomized trials that would bridge an already excellent local control in cT3-4 node-positive disease with long-term survival. This unfortunate separation of clinical research and medical care provides a strong motivation to repurpose known pharmaceuticals that suit for treatment intensification with a focus on distant control. In the framework of on-going phase II-III IG/IMRT-SIB trials, we came across an intriguing translational observation that the ratio of circulating (protumor) myeloid-derived suppressor cells to (antitumor) central memory CD8+ T cells is drastically increased, a possible mechanism of tumor immuno-escape and spread. This finding prompts that restoring the CD45RO memory T-cell pool could be a part of integrated adjuvant interventions. Therefore, the immunocorrective potentials of modified IL-2 and the anti-diabetic drug metformin are thoroughly discussed in the context of tumor immunobiology, mTOR pathways and revised Warburg effect.