The transmembrane cell adhesion protein ADAM9 has been implicated in cancer cell migration and lung cancer metastasis to the brain, but the underpinning mechanisms are unclear and clinical support has been lacking. Here, we demonstrate that ADAM9 enhances the ability of tissue plasminogen activator (tPA) to cleave and stimulate the function of the promigratory protein CDCP1 to promote lung metastasis. Blocking this mechanism of cancer cell migration prolonged survival in tumor-bearing mice and cooperated with dexamethasone and dasatinib (a dual Src/Abl kinase inhibitor) treatment to enhance cytotoxic treatment. In clinical specimens, high levels of ADAM9 and CDCP1 correlated with poor prognosis and high risk of mortality in patients with lung cancer. Moreover, ADAM9 levels in brain metastases derived from lung tumors were relatively higher than the levels observed in primary lung tumors. Our results show how ADAM9 regulates lung cancer metastasis to the brain by facilitating the tPA-mediated cleavage of CDCP1, with potential implications to target this network as a strategy to prevent or treat brain metastatic disease. Cancer Res; 74(18); 1–15. ©2014 AACR.

Natural killer (NK) cells safeguard against early tumor formation by destroying transformed target cells in a process referred to as NK immune surveillance. However, the immune escape mechanisms used by malignant brain tumors to subvert this innate type of immune surveillance remain unclear. Here we show that malignant glioma cells suppress NK immune surveillance by overexpressing the β-galactoside–binding lectin galectin-1. Conversely, galectin-1–deficient glioma cells could be eradicated by host NK cells before the initiation of an antitumor T-cell response. In vitro experiments demonstrated that galectin-1–deficient GL26-Cit glioma cells are ∼3-fold more sensitive to NK-mediated tumor lysis than galectin-1–expressing cells. Our findings suggest that galectin-1 suppression in human glioma could improve patient survival by restoring NK immune surveillance that can eradicate glioma cells. Cancer Res; 74(18); 1–12. ©2014 AACR.

Radiotherapy can produce antitumor benefits beyond the local site of irradiation, an immune-based phenomenon known as the abscopal effect, but the mechanisms underlying these benefits are poorly understood. Preclinical studies of ECI301, a mutant derivative of macrophage inhibitory protein-1α, have shown that its administration can improve the antitumor effects of radiotherapy in a manner associated with a tumor-independent abscopal effect. In this article, we report that i.v. administration of ECI301 after intratumoral injection of tumor cell lysates can inhibit tumor growth, not only at the site of injection but also at nontreated sites. Effects of the tumor lysate were further recapitulated by i.v. administration of the alarmins HSP70 or HMGB1, but not HSP60, and combinations of ECI301 + HSP70 were sufficient to inhibit tumor growth. Although injection of ECI301 + HMGB1 did not inhibit tumor growth, we found that administration of a neutralizing HMGB1 antibody neutralized the cooperative effects of ECI301 on tumor irradiation. Moreover, mice genetically deficient in TLR4, an immune pattern receptor that binds alarmins, including HMGB1 and HSP70, did not exhibit antitumor responses to irradiation with ECI301 administration. Although ECI301 was cleared rapidly from peripheral blood, it was found to bind avidly to HSP70 and HMGB1 in vitro. Our results suggest a model in which sequential release of the alarmins HSP70 and HMGB1 from a tumor by irradiation may trap circulating ECI301, thereby licensing or restoring tumor immunosurveillance capabilities of natural killer cells or CD4+ and CD8+ T cells against tumor cells that may evade irradiation. Cancer Res; 74(18); 1–9. ©2014 AACR.

Telomere malfunction and other types of DNA damage induce an activin A–dependent stress response in mortal nontumorigenic human mammary epithelial cells that subsequently induces desmoplastic-like phenotypes in neighboring fibroblasts. Some characteristics of this fibroblast/stromal response, such as reduced adipocytes and increased extracellular matrix content, are observed not only in tumor tissues but also in disease-free breast tissues at high risk for developing cancer, especially high mammographic density tissues. We found that these phenotypes are induced by repression of the fatty acid translocase CD36, which is seen in desmoplastic and disease-free high mammographic density tissues. In this study, we show that epithelial cells from high mammographic density tissues have more DNA damage signaling, shorter telomeres, increased activin A secretion and an altered DNA damage response compared with epithelial cells from low mammographic density tissues. Strikingly, both telomere malfunction and activin A expression in epithelial cells can repress CD36 expression in adjacent fibroblasts. These results provide new insights into how high mammographic density arises and why it is associated with breast cancer risk, with implications for the definition of novel invention targets (e.g., activin A and CD36) to prevent breast cancer. Cancer Res; 74(18); 1–13. ©2014 AACR.

There have been a number of clinical trials testing the efficacy of FMS-like tyrosine kinase-3 (FLT3) tyrosine kinase inhibitors (TKI) in patients with acute myeloid leukemia (AML) harboring a constitutively activating mutation in FLT3. However, there has been limited efficacy, most often because of inadequate achievement of FLT3 inhibition through a variety of mechanisms. In a previous study, TTT-3002 was identified as a novel FLT3 inhibitor with the most potent activity to date against FLT3 internal tandem duplication (FLT3/ITD) mutations. Here, the activity of TTT-3002 is demonstrated against a broad spectrum of FLT3-activating point mutations, including the most frequently occurring D835 mutations. The compound is also active against a number of point mutations selected for in FLT3/ITD alleles that confer resistance to other TKIs, including the F691L gatekeeper mutation. TTT-3002 maintains activity against patients with relapsed AML samples that are resistant to sorafenib and AC220. Studies utilizing human plasma samples from healthy donors and patients with AML indicate that TTT-3002 is only moderately protein bound compared with several other TKIs currently in clinical trials. Tumor burden of mice in a FLT3 TKI–resistant transplant model is significantly improved by oral dosing of TTT-3002. Therefore, TTT-3002 has demonstrated preclinical potential as a promising new FLT3 TKI that may overcome some of the limitations of other TKIs in the treatment of FLT3-mutant AML. Cancer Res; 74(18); 1–12. ©2014 AACR.