Tumor-targeted TNFα stabilizes tumor vessels and enhances active immunotherapy

Remodeling of tumor stroma and response to therapy

Solid tumors are intrinsically resistant to therapy. Cancer progression occurs when tumor cells orchestrate responses from diverse stromal cell types such as blood vessels and their support cells, inflammatory cells, and fibroblasts; these cells collectively form the tumor microenvironment and provide direct support for tumor growth, but also evasion from cytotoxic, immune and radiation therapies. An indirect result of abnormal and leaky blood vessels in solid tumors is high interstitial fluid pressure, which reduces drug penetration, but also creates a hypoxic environment that further augments tumor cell growth and metastatic spread. Importantly however, studies during the last decade have shown that the tumor stroma, including the vasculature, can be modulated, or re-educated, to allow better delivery of chemotherapeutic drugs or enhance the efficiency of active immune therapy. Such remodeling of the tumor stroma using genetic, pharmacological and other therapeutic approaches not only enhances selective access into tumors but also reduces toxic side effects. This review focuses on recent novel concepts to modulate tumor stroma and thus locally increase therapeutic efficacy.

An antiestrogen-binding protein in human tissues

Although nonsteroidal antiestrogens of the triphenylethylene type are generally considered to act through the estrogen receptor, some observations suggest that estrogen target tissues may also contain a binding protein specific for these compounds. The data so far reported, however, are also consistent with ligand-induced changes in conformation or in the state of aggregation of the estrogen receptor. The studies reported here demonstrate the existence of a protein in human myometrial cytosol which binds 1-[4-(2-dimethylaminoethoxy)phenyl]1,2-diphenylbut-1(Z)-ene ([3H]tamoxifen) with high affinity (Kd = 2.3 X 10(-9) M). This protein exhibits striking specificity for nonsteroidal antiestrogens. Estradiol competes weakly for bound [3H]tamoxifen, while other estrogens and nonestrogenic steroid hormones do not compete at all. Sedimentation analysis and molecular sieve chromatography indicate that the antiestrogen-binding protein is a larger species than the estrogen receptor and elutes from DEAE-Sephacel at a lower KCl concentration (0.03 M) than the estrogen receptor (0.15 M). Differential thermal stability of the estrogen receptor and the antiestrogen-binding protein was demonstrable in the absence of added ligand. The antiestrogen-binding protein was ubiquitous, being present in many tissues where estrogen receptor was undetectable. These findings support the separate existence of an antiestrogen-binding protein.