Preliminary evidences for recruitment of innate responses to rectal cancer cell death elicited by neoadjuvant radio-chemotherapy

Introduction: Rectal cancer patients with a cT3N+M0 tumor stage responds to the neo-adjuvant therapy, which causes necrosis and inflammation in situ. We cannot predict which patients will response. Methods: We collected blood and tissue samples at three time points: at diagnosis, at the end of the first CT cycle and at 8 week after the end of the therapy (coinciding with the surgical resection time of the tumour). At each time point we characterized circulating monocytes by flow cytometry, infiltrating macrophages by immunohistochemistry and selected inflammatory molecules in serum and plasma. Results: We recruited 28 pts, with No substantial changes were detectable in the number of circulating monocytes. In contrast we observed a clear expansion of CD14/CD86 and CD14/CD163 double positive subsets. In fact we observed that in the responder patients the expansion of the CD14/86 subset was clear in the first weeks of treatment and decreased there after. The immunohistochemical study revealed a massive tumoral infiltration by macrophages that displayed clear features of alternative M2 polarization. Conclusion: These data suggest that neoadjuvant therapy modulates the cellular components of innate immune responses that could represent valuable predictive factors