DT-Diaphorase Expression and Tumor Cell Sensitivity to 17-Allylamino,17-demethoxygeldanamycin, an Inhibitor of Heat Shock Protein 90

Abstract

These results suggest that the antitumor activity and possibly the toxicologic properties of 17AAG in humans may be influenced by the expression of DT-diaphorase. Careful monitoring for NQO1 polymorphism and the level of tumor DT-diaphorase activity is therefore recommended in clinical trials with 17AAG.

Professor Tom Connors and the development of novel cancer therapies by the Phase I/II Clinical Trials Committee of Cancer Research UK

“…Intriguingly, DT-diaphorase expression was also found to sensitise cancer cells to the benzoquinone ansamycin 17-AAG (V; Kelland et al, 1999), which has now entered clinical trial as the first-in-class inhibitor of the HSP90 molecular chaperone ATPase activity (see earlier section on clinical trial design and end points). The mechanism behind this potentiation by DT-diaphorase may relate to reduction of the benzoquinone, but the mode of action of 17-AAG in DT-diaphorase-rich cells remains HSP90 inhibition, leading to depletion of oncogenic client proteins and simultaneous inhibition of the PI3 kinase and RAS-ERK signal transduction pathways (Kelland et al, 1999;Clarke et al, 2000;Hostein et al, 2001).…”

“…The mechanism behind this potentiation by DT-diaphorase may relate to reduction of the benzoquinone, but the mode of action of 17-AAG in DT-diaphorase-rich cells remains HSP90 inhibition, leading to depletion of oncogenic client proteins and simultaneous inhibition of the PI3 kinase and RAS-ERK signal transduction pathways (Kelland et al, 1999;Clarke et al, 2000;Hostein et al, 2001). Tom Connors was initially sceptical about our ability to fully understand the mechanism of the antitumour action of even the most exquisitely designed agent (see The Connor's Rules of Anticancer Drug Development, Table 1).…”

Strategies for manipulating the p53 pathway in the treatment of human cancer

“…Two distinct classes of organic compounds have been shown to preserve the native PAb1620 + conformation of p53 in vitro and in vivo. One class of compounds, comprising the benzoquinone ansamycin class of antitumour fungal antibiotics (geldanamycin), inhibits the HSP90 (yellow)-dependent chaperone holoenzyme complex unfolding of p53 protein [165,184,185] and forms a precedent for developing therapeutically relevant agents that modulate chaperone-dependent anti-apoptotic pathways [182,183]. A second class of compounds (prototype being CP-31,398) presumably binds directly to native p53 protein and prevents its unfolding and inactivation by stabilizing the intrinsic thermoinstability (∆) of the tetramer [143,168,169,171,174,263].…”

Overexpression of BclXL in a human ovarian carcinoma cell line: Paradoxic effects on chemosensitivity in vitro versus in vivo

“…As described previously, Bcl XL protein was detected after lysis, separation using 8 -16% SDS-PAGE gels (Invitrogen, Groningen, The Netherlands), transfer to nitrocellulose membranes and visualisation by enhanced chemiluminescence (ECL) reagents using the S-18 antibody (Santa Cruz Biotechnology, Santa Cruz, CA). 27 Transfer efficiency and equal loading were checked by staining with Ponceau S. In addition, levels of other Bcl-2 family proteins were measured: Bcl-2 (using the mouse monoclonal antibody clone 124; Dako, Carpinteria, CA) and Bax (using the rabbit polyclonal antibody N-20; Santa Cruz Biotechnology).…”

“…25,27 When palpable tumours arose, 2 mm 2 pieces were transplanted by surgical incision under anaesthesia to other mice.…”