Schedule-dependent bortezomib modulation of gemcitabine pharmacokinetics and pharmacodynamics in non-small cell lung cancer and blood mononuclear cells
Authors: Elisa Giovannetti, Cecilia Ceresa, Adrie Laan, Jens Voortman, Richard Honeywell, Giuseppe Giaccone, Godefridus Peters
Journal: Cancer Research (2008)

AACR Annual Meeting-- Apr 12-16, 2008; San Diego, CA

3262 

In a phase IB trial of bortezomib combination with gemcitabine/cisplatin in patients with primarily non-small cell lung cancer (NSCLC) (Voortman et al., 2007) a transient drop in the plasma levels of deoxycytidine was observed, which has never been observed in cisplatin/gemcitabine-treated patients. The present study was aimed to investigate the pharmacokinetic and pharmacodynamic interactions between gemcitabine and bortezomib in NSCLC and peripheral blood mononuclear cells (PBMCs).    Accumulation of gemcitabine metabolites, including difluorodeoxycytidine triphosphate (dFdCTP), was studied by LC-MS/MS and HPLC in PBMCs from patients receiving bortezomib 1.0mg/m2 plus gemcitabine 1000mg/m2 and cisplatin 70mg/m2. dFdCTP was also measured in PBMCs from volunteers and NSCLC cells (H460 and SW1573) exposed to simultaneous 4h or sequential treatments consisting of 4h-exposure to gemcitabine (50μM) followed by 2h bortezomib (100nM), or the reverse order. Cytotoxicity was studied by MTT, while deoxycytidine kinase (dCK) expression was assessed by PCR and western blot.    Gemcitabine total phosphate levels in PBMCs from 9 bortezomib/gemcitabine/cisplatin-treated patients were significantly reduced after 90 min until 4 h from the start of gemcitabine infusion, compared to gemcitabine/cisplatin-treated patients. Bortezomib/gemcitabine combinations also reduced dFdCTP in PBMCs in vitro . In contrast, dFdCTP continued to increase for 24 h after drug removal in SW1573, while in H460 cells dFdCTP levels were reduced after the removal of the simultaneous and the gemcitabine→bortezomib combination. However, dFdCTP significantly increased in both cell lines after bortezomib pre-incubation with respect to gemcitabine alone. In line with dFdCTP increase, all the drug combinations showed a synergistic interaction in SW1573 cells. In H460 cells only the bortezomib→gemcitabine combination significantly reduced cell growth with respect to single drugs, associated with dFdCTP increase. The simultaneous and the gemcitabine→bortezomib combination showed a lower cytotoxicity than expected, associated with dFdCTP decrease. Western blot revealed a major increase of dCK expression after bortezomib pre-incubation in both cell lines.    Our data show that bortezomib affects gemcitabine pharmacokinetics and pharmacodynamics differently in PBMCs and NSCLC cells, suggesting that PBMCs are not an adequate surrogate tissue to evaluate the anticancer activity of bortezomib/gemcitabine combinations.    However the bortezomib→gemcitabine/cisplatin schedule appeared a safe and active combination for the treatment of advanced NSCLC patients, and the bortezomib→gemcitabine combination showed a synergistic interaction in NSCLC cells, associated with increase of dFdCTP levels and dCK expression.    Voortman J, et al., Clin Cancer Res 2007;13:3642-51