One specific limitation to the clinical development of targeted cancer therapeutics is the lack of well-validated pharmacodynamic markers. Such tools might conceivably provide a framework within which to better evaluate the selection of specific molecules as therapeutic targets. Nevertheless, the practical application of this hypothesis in clinical development remains elusive. In this study, we present a minimally invasive pharmacodynamic assay for monitoring therapy-mediated changes in the activity of target signaling pathways by using fine needle aspiration (FNA) samples and quantitative ELISA methods. To this end, we used the HuCCT-1 cholangiocarcinoma cell line treated with gefitinib (ZD1839, Iressa), a selective blocker of the epidermal growth factor receptor (EGFR), and CI-1040, a selective inhibitor of the mitogen extracellular regulated kinase [mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase 1/2]. HuCCT-1 cells were resistant to gefitinib and CI-1040 alone but susceptible to the combination of these drugs in vitro and in vivo. This effect was associated with a greater inhibition of ERK1/2 activation, a downstream mediator in the EGFR-mitogen-activated protein/ERK kinase pathway. Using this model, we sought to assess whether FNA-obtained tumor biopsies could be used to measure signaling pathway activation. Cellular extracts prepared from FNA samples yielded adequately cellular, high-quality samples to assess therapy-mediated changes in EGFR and ERK1/2 phosphorylation by Western blotting and quantitative ELISA assays. Treatment with gefitinib alone effectively inhibited EGFR activation but failed to block ERK1/2 phosphorylation and tumor growth. Blocking was achieved by the addition of CI-1040 to the treatment regimen. These results show that the combination of serial FNA sampling with highly sensitive quantitative ELISA assays permits assessment of therapy-mediated changes in signaling pathways, which correlate well with antitumor effects. This assay is simple to implement and broadly applicable to diverse tumor types in clinical studies with cancer patients and may be useful in the development of targeted anticancer agents.
ASJC Scopus subject areas
- Drug Discovery