Effects of geldanamycin and other naturally occurring small molecule antagonists of heat shock protein 90 on HER2 protein expression

A novel proteotoxic combination therapy for EGFR+ and HER2+ cancers

While HER2 and EGFR are overexpressed in breast cancers and multiple other types of tumors, the use of EGFR and/or HER2 inhibitors have failed to cure many cancer patients, largely because cancers acquire resistance to HER2/EGFR-specific drugs. Cancers that overexpress the HER-family proteins EGFR, HER2, and HER3 are uniquely sensitive to agents that disrupt HER2 and EGFR protein folding. We previously showed that disruption of disulfide bond formation by Disulfide Disrupting Agents (DDAs) kills HER2/EGFR overexpressing cells through multiple mechanisms. Herein, we show that interference with proline isomerization in HER2/EGFR overexpressing cells also induces cancer cell death. The peptidyl-prolyl isomerase inhibitor Cyclosporine A (CsA) selectively kills EGFR+ or HER2+ breast cancer cells in vitro by activating caspase-dependent apoptotic pathways. Further, CsA synergizes with the DDA tcyDTDO to kill HER2/EGFR overexpressing cells in vitro and the two agents cooperate to kill HER2+ tumors in vivo. There is a critical need for novel strategies to target HER2+ and EGFR+ cancers that are resistant to currently available mechanism-based agents. Drugs that target HER2/EGFR protein folding, including DDAs and CsA, have the potential to kill cancers that overexpress EGFR or HER2 through the induction of proteostatic synthetic lethality.

Treatment of HER2-positive metastatic breast cancer following initial progression

Significant advances in molecular-targeted therapies have provided more effective and less aggressive forms of therapy for patients with HER2-overexpressing metastatic breast cancers. Despite the initial encouraging results of many therapeutic randomized trials that have been undertaken in this setting, de novo and acquired resistance to trastuzumab, the first anti-HER2 monoclonal antibody to demonstrate significant activity in this setting, can occur. Because recent studies strongly support a role for trastuzumab in not only the management of metastatic disease but also the adjuvant setting for HER2-overexpressing breast cancers, the clinical problem of trastuzumab resistance is becoming increasingly important. Specific recommendations for the optimal treatment of HER2-overexpressing metastatic disease are challenging because considerable advances in the field have been made. This article will review some of the main points to be considered for decision-making in anti-HER2 treatment in the metastatic setting: (1) the benefit of continued trastuzumab after progression on a first-line trastuzumab-containing regimen, (2) novel agents that have been recently added to the plethora of drugs available to treat HER2-overexpressing breast cancers, and (3) molecular mechanisms that contribute to trastuzumab resistance. These issues are imperative in identifying novel therapeutic targets with the goal of increasing the magnitude and duration of response to trastuzumab-based treatment.

Affibody molecules: potential for in vivo imaging of molecular targets for cancer therapy

Targeting radionuclide imaging of tumor-associated antigens may help to select patients who will benefit from a particular biological therapy. Affibody molecules are a novel class of small (approximately 7 kDa) phage display-selected affinity proteins, based on the B-domain scaffold of staphylococcal protein A. A large library (3 x 10(9) variants) has enabled selection of high-affinity (up to 22 pM) binders for a variety of tumor-associated antigens. The small size of Affibody molecules provides rapid tumor localization and fast clearance from nonspecific compartments. Preclinical studies have demonstrated the potential of Affibody molecules for specific and high-contrast radionuclide imaging of HER2 in vivo, and pilot clinical data using indium-111 and gallium-68 labeled anti-HER2 Affibody tracer have confirmed its utility for radionuclide imaging in cancer patients.

Pochonins A-F, new antiviral and antiparasitic resorcylic acid lactones from Pochonia chlamydosporia var. catenulata

Monorden (1) and the novel resorcylic acid lactones pochonins A (2), B (4), C (6), D (7), and E (8) as well as tetrahydromonorden (5) and pseurotin A (22) were isolated from cultures of the clavicipitaceous hyphomycete Pochonia chlamydosporia var. catenulata strain P 0297. Fermentation of P 0297 in bromide-containing culture media led to a shift in secondary metabolite production and yielded monocillins III (3) and II (9) as major metabolites besides monorden (1) as well as the novel compounds pochonin F (10) and a monocillin II glycoside (11) as minor metabolites. Most of these compounds showed moderate activities in a cellular replication assay against Herpes Simplex Virus 1 (HSV1) and against the parasitic protozoan Eimeria tenella. In contrast to the structurally related zearalenone derivatives none of the metabolites of strain P 0297 were found to be active in a fluorescence polarization assay for determination of modulatory activities on the human estrogenic receptor ERbeta. Beta-zearalenol (17), but not zearalenone (15) and alpha-zearalenol (16), showed antiherpetic effects. We report the production, isolation, and structure elucidation of compounds 1-11 and their biological characterization.