Citations

AbstractMetastatic renal cell carcinoma (RCC) is an aggressive disease refractory to most existing therapeutic modalities. Identifying new markers for disease progression and drug targets for RCC will benefit this unmet medical need. We report a subset of clear cell and papillary cell RCC aberrantly expressing the lymphocyte activation marker CD70, a member of the tumor necrosis factor superfamily. Importantly, CD70 expression was found to be maintained at the metastatic sites of RCC. Anti-CD70 antibody-drug conjugates (ADC) consisting of auristatin phenylalanine phenylenediamine (AFP) or monomethyl auristatin phenylalanine (MMAF), two novel derivatives of the anti-tubulin agent auristatin, mediated potent antigen-dependent cytotoxicity in CD70-expressing RCC cells. Cytotoxic activity of these anti-CD70 ADCs was associated with their internalization and subcellular trafficking through the endosomal-lysosomal pathway, disruption of cellular microtubule network, and G2-M phase cell cycle arrest. The efficiency of drug delivery using anti-CD70 as vehicle was illustrated by the much enhanced cytotoxicity of antibody-conjugated MMAF compared with free MMAF. Hence, ADCs targeted to CD70 can selectively recognize RCC, internalize, and reach the appropriate subcellular compartment(s) for drug release and tumor cell killing. In vitro cytotoxicity of these ADCs was confirmed in xenograft models using RCC cell lines. Our findings provide evidence that CD70 is an attractive target for antibody-based therapeutics against metastatic RCC and suggest that anti-CD70 ADCs can provide a new treatment approach for advanced RCC patients who currently have no chemotherapeutic options. (Cancer Res 2006; 66(4): 2328-37)

ABSTRACT Neurofibrillary tangles (NFTs) are a characteristic neuropathological feature of Alzheimer's disease (AD), and molecular chaperones appear to be involved in the removal of disease‐associated hyperphosphorylated tau, a primary component of NFTs. Here, novel HSP90 inhibitors were used to examine the impact of chaperone elevation on clearance of different tau species in transfected cells using a unique quantitative assay. The HSP90 inhibitors reduced levels of tau phosphorylated at proline‐directed Ser/Thr sites (pS202/T205, pS396/S404) and conformationally altered (MC‐1) tau species, an epitope that is immeasurable by standard Western blot techniques. The selective clearance of these phospho‐tau species and MC‐1 tau was mediated via the proteasome, while lysosomal‐mediated tau degradation seems to lack specificity for certain tau species, suggesting a more general role in total tau removal. Interestingly, tau phosphorylated at S262/S356 within the tau microtubule binding domain was minimally affected by chaperone induction. Overall, our data show that chaperone induction results in the selective clearance of specific phospho‐tau and conformationally altered tau species mediated by the proteasome; however, the apparent stability of pS262/S356 tau may also explain why MARK is able to regulate normal tau function yet still be linked to the initiation of pathogenic tau hyperphosphorylation in AD.