Project description:The direct and indirect effects of targeting specific tumor-associated macrophage (TAM) subsets in cancer are not well-defined. TAM targeting strategies are frequently based on the ‘M1’ or ‘M2’ polarization categories, even as substantial data challenges this binary modeling of macrophage cell state. One molecule consistently referenced as a delineator of a putative immunosuppressive ‘M2’ state is the surface protein CD206. We thus made a novel conditional CD206 (Mrc1) knock-in mouse to specifically visualize and/or deplete CD206+ TAMs and assess their correspondence with pro-tumoral immunity. Early, but not late depletion of CD206+ macrophages and monocytes (here, ‘Mono/Macs’) led to an indirect loss of a key anti-tumor network of NK cells, conventional type I dendritic cells (cDC1) and CD8 T cells. Among myeloid cells, we found that the CD206+ TAMs are the primary producers of CXCL9, and able to differentially attract activated CD8 T cells. In contrast, a population of stress-responsive TAMs (“Hypoxic” or Spp1+) and immature monocytes, which lack CD206 expression and become prominent following early depletion, expressed markedly diminished levels of CXCL9. Those NK and CD8 T cells which enter CD206-depleted tumors express vastly reduced levels of the corresponding receptor Cxcr3, the cDC1-attracting chemokine Xcl1 and cDC1 growth factor Flt3l transcripts. Consistent with the loss of this critical network, early CD206+ TAM depletion decreased tumor control by antigen specific CD8 T cells in mice. Likewise, in humans, the CD206Replete, but not the CD206Depleted Mono/Mac gene signature correlated robustly with CD8 T cell, NK cell and stimulatory cDC1 gene signatures and transcriptomic signatures skewed towards CD206Replete Mono/Macs associated with better survival. Together, these findings negate the unqualified classification of CD206+ ‘M2-like’ macrophages as immunosuppressive and provide further evidence of the context-dependence of macrophage function in tumors.

Project description:The screen for genes involved in the spontaneous loss of heterozygosity mutagenesis (SLM) in diploid cells was done on the collections of deletion strains of Saccharomyces cerevisiae created by the Saccharomyces Genome Deletion Project (http://www-sequence.stanford.edu/group/yeast_deletion_project/). Screens were performed on the pools of clones. Barcode microarrays were used to detect the increased SLM frequency leading to relative increase in abundance of deletion clone in a pool. Collections used were: Homozygous Diploid (HD) and Essential (E) mixed to create single HDE pool. Three mutagenesis markers were used: (1) naturally existing mating type locus, and two newly introduced markers, (2) CAN1/can1delta, (3) URA3/ura3delta. 1. To detect the increased SLM frequency at the mating type locus HDE pool was crossed to MATa or MATalpha strain. Deletion clones that gained mating competence due to loss of heterozygosity (LOH) at the mating type locus gave rise to clones with the ability to grow on minimal medium. The relative abundance of these clones was compared to the abundance in the original HDE pool. 2. To detect the increased SLM frequency at the CAN1/can1delta locus the derivative HDE pool was created. Every cell of this pool had one of two copies of CAN1 gene deleted. The increased SLM frequency led to increased relative abundance of respective deletion clone under canavanine selection and could be estimated by comparing it to the abundance when pool was grown without selection. 3. To detect the increased SLM frequency at the URA3/ura3delta locus the derivative HDE pool was created. Every cell of this pool had one of two copies of URA3 gene deleted. The increased SLM frequency led to increased relative abundance of respective deletion clone under 5M-^R-fluoroorotic acid selection and could be estimated by comparing it to the abundance when pool was grown without selection. 4. For screens of SLM at CAN1 and URA3 markers the resistance control experiments were performed to detect genes whose deletion is sufficient to enable yeast cells with functional CAN1 or URA3 to grow in the presence of canavanine or 5M-^R- fluoroorotic acid respectively. 5. To include in the analysis slow-growing deletion clones control hybridizations were performed to detect genes whose deletion extends the doubling time of yeast cells.

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