ABSTRACT: Certain anticancer drugs, particularly cyclophosphamide (CTX), were shown to enhance the antitumor efficacy of immunotherapy through different immunomodulatory mechanisms. A better understanding of the cellular and molecular basis of CTX-mediated immunomodulation is needed to improve the efficacy of chemoimmunotherapy. Transcript profiling and flow cytometry were used to explore CTX immune-enhancing activity in patients with hematologic malignancies. A single high-dose treatment quickly (1-2 days) induced an extensive transcriptional modulation in peripheral blood mononuclear cells, leading to the reduction of cell cycle and biosynthetic/metabolic processes and to the augmentation of transcripts related to DNA damage and cell death (p53 signaling pathway, CDKN1A, CCND3, BAX, BBC3, BID, DDB2, SESN2), of scavenger receptors involved in the recognition of death (MARCO, CD68, CD163L1, SCARB2), of antigen processing/presentation mediators (CIITA, CTSC, CTSL1, CTSZ, GLA, GAA, TPP1, NEU1, SLC11A1, LAMP-2), of T cell activation markers (CD69, OX40) and, noticeably, of a type I interferon (IFN-I) signature (OAS1, CXCL10, BAFF, IFITM2, IFI6, IRF5, IRF7, STAT2, UBE2L6, UNC93B1, ISG20L1, TYK2). Moreover, the plasma levels of IFN-I-induced proinflammatory mediators (CXCL10, CCL2, IL-8, BAFF) were increased by treatment. Accordingly, CTX preconditioning induced both monocyte and lymphocyte activation, leading to the expansion of CD14+CD16+ monocytes, of HLA-DR+, IL8RA+, MARCO+ monocytes/dendritic cells and of CD69+, OX40+, IL8RA+ lymphocytes. Altogether, these data define for the first time the immunomodulatory factors induced by CTX in humans and indicate that preconditioning chemotherapy may stimulate immunity as a consequence of danger perception associated to its cytotoxic action on blood cells, through p53 and IFN-I-related mechanisms.
