Refractoriness of solid tumors including colorectal cancers (CRC) to immunotherapies is attributed to the immunosuppressive tumor microenvironment that protects malignant cells from cytotoxic T lymphocytes (CTL). We found that downregulation of the type I interferon receptor chain IFNAR1 occurs in human CRC and mouse models of CRC. Downregulation of IFNAR1 in tumor stroma stimulated CRC development and growth, played a key role in formation of the immune privileged niche and predicted poor prognosis in human CRC patients. Genetic stabilization of IFNAR1 improved CTL survival and increased the efficacy of the chimeric antigen receptor T cell transfer and PD-1 inhibition. Likewise, pharmacologic stabilization of IFNAR1 suppressed tumor growth providing the rationale for upregulating IFNAR1 to improve anti-cancer therapies.

Cell adhesion molecules have been implicated in the colonization of cancer cells to distant organs. Prostate cancer (PCa) has a propensity to metastasize to bone, and cadherin-11, which is an osteoblast cadherin aberrantly expressed in PCa cells derived from bone metastases, has been shown to play a role in the metastasis of PCa cells to bone. However, the mechanism by which cadherin-11 is involved in this process is not known. Here, we show that expression of cadherin-11 in cadherin-11-negative C4-2B4 cells increases their spreading and intercalation into an osteoblast layer and also stimulates C4-2B4 cell migration and invasiveness. The downregulation of cadherin-11 in cadherin-11-expressing metastatic PC3 cells decreases cell motility and invasiveness. Further, both the juxtamembrane (JMD) and β-catenin binding domains (CBS) in the cytoplasmic tail of cadherin-11 are required for cell migration and invasion, but not spreading. Gene array analyses showed that several invasion-related genes, including MMP-7 and MMP-15, are upregulated in cadherin-11-expressing, but not in cad11-ΔJMD-expressing or cad11-ΔCBS-expressing, C4-2B4 cells. These observations suggest that cadherin-11 not only provides a physical link between PCa cells and osteoblasts but also increases PCa cell motility and invasiveness that may facilitate the metastatic colonization of PCa cells in bone. Cancer Res; 70(11); 4580-9. ©2010 AACR.

Graphical AbstractHighlights d Tumor-derived extracellular vesicles (TEV) downregulate IFNAR1 and CH25H d CH25H acts to restrict TEV uptake and limit the education of healthy cells d Downregulation of CH25H in normal cells promotes melanoma metastasis d Disruption of TEV uptake and education by reserpine elicits anti-metastatic effects SUMMARY Tumor-derived extracellular vesicles (TEV) ''educate'' healthy cells to promote metastases. We found that melanoma TEV downregulated type I interferon (IFN) receptor and expression of IFN-inducible cholesterol 25-hydroxylase (CH25H). CH25H produces 25-hydroxycholesterol, which inhibited TEV uptake. Low CH25H levels in leukocytes from melanoma patients correlated with poor prognosis. Mice incapable of downregulating the IFN receptor and Ch25h were resistant to TEV uptake, TEV-induced pre-metastatic niche, and melanoma lung metastases; however, ablation of Ch25h reversed these phenotypes. An anti-hypertensive drug, reserpine, suppressed TEV uptake and disrupted TEV-induced formation of the pre-metastatic niche and melanoma lung metastases. These results suggest the importance of CH25H in defense against education of normal cells by TEV and argue for the use of reserpine in adjuvant melanoma therapy.

Oncogene activation induces DNA damage responses and cell senescence. We report a key role of type I interferons (IFN) in oncogene-induced senescence. IFN signaling-deficient melanocytes expressing activated Braf do not exhibit senescence and develop aggressive melanomas. Restoration of IFN signaling in IFN-deficient melanoma cells induces senescence and suppresses melanoma progression. Additional data from human melanoma patients and mouse transplanted tumor models suggest the importance of non-cell-autonomous IFN signaling. Inactivation of IFN pathway is mediated by the IFN receptor IFNAR1 downregulation that invariably occurs during melanoma development. Mice harboring an IFNAR1 mutant, which is partially resistant to downregulation, delay melanoma development, suppress metastatic disease, and better respond to BRAF or PD1 inhibitors. These results suggest that IFN signaling is an important tumor suppressive pathway that inhibits melanoma development and progression and argue for targeting IFNAR1 downregulation to prevent metastatic disease and improve the efficacy of molecularly-targeted and immune-targeted melanoma therapies.

Cadherin-11 is a member of a superfamily mainly expressed in osteoblasts but not in epithelial cells. However, prostate cancer (PCa) cells with bone metastasis propensity express high levels of cadherin-11 and reduced levels of E-cadherin. Downregulation of cadherin-11 inhibits interaction of PCa cells with osteoblasts in vitro and homing of PCa cells to bone in an animal model of metastasis. These findings raise the possibility that targeting the extracellular domain of cadhein-11 may prevent PCa bone metastasis. To explore this possibility, we generated a panel of monoclonal antibodies (mAbs) against cadherin-11 extracellular domain. From the 21 antibodies obtained, mAbs 2C7 and 1A5 inhibited cadherin-11 mediated cell-cell aggregation in L-cells transfected with cadherin-11 in vitro. Both antibodies were specific to cadherin-11 as they did not recognize E-cadherin or N-cadherin on C4-2B or PC3 cells, respectively. Further, mAb 2C7 inhibited cadherin-11-mediated aggregation between PC3-mm2 cells and MC3T3-E1 osteoblasts. To determine which cadherin domains are critical for PCa and osteoblast interactions, a series of deletion mutants were analyzed. We identified a previously unknown unique motif, aa 343-348, in the cadherin-11 EC3 domain that is recognized by mAb 2C7 and showed that this motif mediated cell-cell adhesion. Consistent with the inhibition of cell-cell aggregation in vitro, application of mAb 2C7 in a prophylactic setting as a single agent effectively prevented dissemination of highly metastatic PC3-mm2 cells to bone in a mouse model of metastasis. These results suggest that targeting the extracellular domain of cadherin-11 may be developed for the prevention of bone metastases.