Using androgen receptor (AR) knockout mice to determine AR functions in selective prostate cancer (PCa) cells, we determined that AR might play differential roles in various cell types, either to promote or suppress PCa development/progression. These observations partially explain the failure of current androgen deprivation therapy (ADT) to reduce/prevent androgen binding to AR in every cell. Herein, we identified the AR degradation enhancer ASC-J9, which selectively degrades AR protein via interruption of the AR-AR selective coregulator interaction. Such selective interruption could, therefore, suppress AR-mediated PCa growth in the androgen-sensitive stage before ADT and in the castration-resistant stage after ADT. Mechanistic dissection suggested that ASC-J9 could activate the proteasome-dependent pathway to promote AR degradation through the enhanced association of AR-Mdm2 complex. The consequences of ASC-J9-promoted AR degradation included reduced androgen binding to AR, AR N-C terminal interaction, and AR nuclear translocation. Such inhibitory regulation could then result in suppression of AR transactivation and AR-mediated cell growth in eight different mouse models, including intact or castrated nude mice xenografted with androgen-sensitive LNCaP cells or androgen-insensitive C81 cells and castrated nude mice xenografted with castration-resistant C4-2 and CWR22Rv1 cells, and TRAMP and Pten(+/-) mice. These results demonstrate that ASC-J9 could serve as an AR degradation enhancer that effectively suppresses PCa development/progression in the androgen-sensitive and castration-resistant stages.

Fibrin (Fn) deposition defines several type 1 immune responses, including delayed-type hypersensitivity and autoimmunity in which PMNs are involved. Fn monomer and fibrinogen (Fg) are multivalent ligands for a variety of cell receptors during cell adhesion. These cell receptors provide critical linkage between thrombosis, inflammation and cancer metastasis under venous flow conditions. However, the mechanisms of Fn-mediated interactions among immune cells and circulating tumor cells remain elusive. By using a cone-plate viscometer shear assay and dual-color flow cytometry, we demonstrated that soluble Fg and Fn had different abilities to enhance heterotypic aggregation between polymorphonuclear leukocytes (PMNs) and Lu1205 melanoma cells in a shear flow, regulated by thrombin levels. In addition, the involvement of integrin αvβ3, Intercellular Adhesion Molecule-1 (ICAM-1) and CD11b/CD18 (Mac-1) in fibrin(ogen)-mediated melanoma-PMN aggregations was explored. Kinetic studies provided evidences that ICAM-1 mediated initial capture of melanoma cells by PMNs, while αvβ3 played a role in sustained adhesion of the two cell types at a shear rate of 62.5 s-1. Quantitative analysis of the melanoma-PMN interactions conducted by a parallel-plate flow chamber assay further revealed that at a shear rate of 20 s-1, αvβ3 had enough contact time to form bonds with Mac-1 via Fn, which could not otherwise occur at a shear rate higher than 62.5 s-1. Our studies have captured a novel finding that leukocytes could be recruited to tumor cells via thrombin-mediated Fn formation within a tumor microenvironment, and αvβ3 and ICAM-1 may participate in multi-step fibrin(ogen)-mediated melanoma cell adhesion within the circulation.

Expression of macrophage inhibitory cytokine-1 (MIC-1), a member of the transforming growth factor-␤ family, normally increases during inflammation or organ injury. MIC-1 is also expressed at higher levels in melanomas; however, its role in tumorigenesis is unknown. This report identifies a novel function for MIC-1 in cancer. MIC-1 was overexpressed in ϳ67% of advanced melanomas, accompanied by fivefold to six-fold higher levels of secreted protein in serum of melanoma patients compared with normal individuals. Constitutively active mutant