Tumor-associated macrophages subvert T-cell function and correlate with reduced survival in clear cell renal cell carcinoma

Abstract

Although malignant cells can be recognized and controlled by the immune system, in patients with clinically apparent cancer immunosurveillance has failed. To better understand local immunoregulatory processes that impact on cancer progression, we correlated intratumoral immunological profiles with the survival of patients affected by primary clear cell renal cell carcinoma (ccRCC). A retrospective analysis of 54 primary ccRCC samples for 31 different immune response-related transcripts, revealed a negative correlation of CD68 (a marker of tumor-associated macrophages, TAMs) and FOXP3 (a marker of regulatory T cells, Tregs) with survival. The subsequent analysis of 12 TAM-related transcripts revealed an association between the genes coding for CD163, interferon regulatory factor 4 (IRF4) and fibronectin 1 (FN1), all of which have been linked to the M2 TAM phenotype, with reduced survival and increased tumor stage, whereas the opposite was the case for the M1-associated gene coding for inducible nitric oxide synthetase (iNOS). The M2 signature of (CD68+) TAMs was found to correlate with CD163 expression, as determined in prospectively collected fresh ccRCC tissue samples. Upon co-culture with autologous tumor cells, CD11b+ cells isolated from paired blood samples expressed CD163 and other M2-associated proteins, suggesting that the malignant cells promote the accumulation of M2 TAMs. Furthermore, the tumor-associated milieu as well as isolated TAMs induced the skewing of autologous, blood-derived CD4+ T cells toward a more immunosuppressive phenotype, as shown by decreased production of effector cytokines, increased production of interleukin-10 (IL-10) and enhanced expression of the co-inhibitory molecules programmed death 1 (PD-1) and T-cell immunoglobulin mucin 3 (TIM-3). Taken together, our data suggest that ccRCC progressively attracts macrophages and induces their skewing into M2 TAMs, in turn subverting tumor-infiltrating T cells such that immunoregulatory functions are increased at the expense of effector functions.

Dynamic Treg interactions with intratumoral APCs promote local CTL dysfunction

“…CTLs subsequently activated by such Treg-preconditioned DCs that had lost their costimulatory capacity showed enhanced coinduction of PD-1 and TIM-3, which may directly render them dysfunctional, or make them more susceptible to the induction of dysfunction through continued stimulation in a low CD80/86 context, where coinhibitory signals cannot be balanced by costimulatory signals (60). Interestingly, tumor-associated macrophages from human cancer patients also induce PD-1 and TIM-3 expression in autologous T cells (61), which suggests that this property is not limited to DCs.…”

Immune signature of tumor infiltrating immune cells in renal cancer

“…36 A recent study on tumor-associated macrophages in RCC describes an association of the number of CD68C macrophages with a shorter survival as well as an accumulation of M2 type macrophages expressing the scavenger receptor CD163 and the interferon regulatory factor 4 in ccRCC. 37 Other authors investigated the intratumoral balance of polarized tumor-associated macrophages and showed that especially CD206/mannose receptor-positive macrophages (M2 type) are associated with reduced survival in RCC patients. 38 Recently, markers for human MDSC have been developed (e.g., CD14CHLA-DRlow) therefore the inclusion of myeloid cells in flow cytometric analyses would be a worthwhile approach in future studies.…”

Macrophage-derived nitric oxide initiates T-cell diapedesis and tumor rejection

“…4,5,21 Macrophage populations in tumors are known to be heterogeneous with varying proportions of M2 and M1 macrophages. Recent clinical studies suggest a correlation between the presence of M1-skewed CD68C HLA-DRC iNOSCmacrophages and clinical outcome in tumors such as non-small cell lung cancer, pancreatic cancer, colorectal cancer, ovarian cancer, and renal cell carcinoma [32][33][34][35][36] ). NO-producing macrophages can be cytocidal in vitro against tumor cells, 37,38 but formal evidence for in vivo cytoxicity against solid tumors is lacking.…”