Macrophage infiltration has been identified as an independent poor prognostic factor in several cancer types. The major survival factor for these macrophages is macrophage colony-stimulating factor 1 (CSF-1). We generated a monoclonal antibody (RG7155) that inhibits CSF-1 receptor (CSF-1R) activation. In vitro RG7155 treatment results in cell death of CSF-1-differentiated macrophages. In animal models, CSF-1R inhibition strongly reduces F4/80(+) tumor-associated macrophages accompanied by an increase of the CD8(+)/CD4(+) T cell ratio. Administration of RG7155 to patients led to striking reductions of CSF-1R(+)CD163(+) macrophages in tumor tissues, which translated into clinical objective responses in diffuse-type giant cell tumor (Dt-GCT) patients.

Colony-stimulating factor 1 (CSF1) is a key regulator of monocyte/macrophage differentiation that sustains the protumorigenic functions of tumor-associated macrophages (TAMs). We show that CSF1 is expressed in human melanoma, and patients with metastatic melanoma have increased CSF1 in blood compared to healthy subjects. In tumors, CSF1 expression correlated with the abundance of CD8 + T cells and CD163 + TAMs. Human melanoma cell lines consistently produced CSF1 after exposure to melanoma-specific CD8 + T cells or T cell-derived cytokines in vitro, reflecting a broadly conserved mechanism of CSF1 induction by activated CD8 + T cells. Mining of publicly available transcriptomic data sets suggested co-enrichment of CD8 + T cells with CSF1 or various TAM-specific markers in human melanoma, which was associated with nonresponsiveness to programmed cell death protein 1 (PD1) checkpoint blockade in a smaller patient cohort. Combination of anti-PD1 and anti-CSF1 receptor (CSF1R) antibodies induced the regression of BRAF V600E-driven, transplant mouse melanomas, a result that was dependent on the effective elimination of TAMs. Collectively, these data implicate CSF1 induction as a CD8 + T cell-dependent adaptive resistance mechanism and show that simultaneous CSF1R targeting may be beneficial in melanomas refractory to immune checkpoint blockade and, possibly, other T cell-based therapies.

Purpose: The aim of the present study was to identify human genes that might prove useful in the diagnosis and therapy of primary breast cancer. Experimental Design: Twenty-four matched pairs of invasive ductal breast cancer and corresponding benign breast tissue were investigated by a combination of laser microdissection and gene expression profiling. Differential expression of candidate genes was validated by dot blot analysis of cDNA in 50 pairs of matching benign and malignant breast tissue. Cellular expression of candidate genes was further validated by RNA in situ hybridization, quantitative reverse transcription-PCR, and immunohistochemistry using tissue microarray analysis of 272 nonselected breast cancers. Multivariate analysis of factors on overall survival and recurrence-free survival was done. Results: Fifty-four genes were found to be up-regulated and 78 genes were found to be downregulated. Dot blot analysis reduced the number of up-regulated genes to15 candidate genes that showed at least a 2-fold overexpression in >15 of 50 (30%) tumor/normal pairs. We selected phosphatidic acid phosphatase type 2 domain containing 1A (PPAPDC1A) and karyopherin a2 (KPNA2) for further validation. PPAPDC1A and KPNA2 RNA was up-regulated (fold change >2) in 84% and 32% of analyzed tumor/normal pairs, respectively. Nuclear protein expression of KPNA2 was significantly associated with shorter overall survival and recurrence-free survival. Testing various multivariate Cox regression models, KPNA2 expression remained a highly significant, independent and adverse risk factor for overall survival. Conclusions: Gene expression profiling of laser-microdissected breast cancer tissue revealed novel genes that may represent potential molecular targets for breast cancer therapy and prediction of outcome.

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