Influence of epidermal growth factor receptor (EGFR), p53 and intrinsic MAP kinase pathway status of tumour cells on the antiproliferative effect of ZD1839 (‘Iressa’)

Abstract

ZD1839 ('Iressa') is an orally active, selective epidermal growth factor receptor -tyrosine kinase inhibitor (EGFR -TKI), which blocks signal transduction pathways implicated in proliferation and survival of cancer cells, and other host-dependent processes promoting cancer growth. Permanent downstream activation of the mitogen-activated protein kinase pathway can theoretically bypass the upstream block of epidermal growth factor receptor-dependent mitogen-activated protein kinase activation at the epidermal growth factor receptor level. We investigated the impact of epidermal growth factor receptor content, p53 status and mitogen-activated protein kinase signalling status on ZD1839 sensitivity in a panel of human tumour cell lines: seven head and neck cancer cell lines and two colon cancer cell lines (LoVo, HT29) with derivatives differing only by a specific modification in p53 status (LoVo p53 wt + p53 mut cells, HT29 p53 mut + p53 wt rescued cells). The antiproliferative activity of ZD1839 was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide test. ZD1839 concentrations ranged from 0.2 -200 mM (48 h exposure). Epidermal growth factor receptor expression, p53 status and p42/p44 (for testing a constitutively active mitogen-activated protein kinase pathway status) were determined by competition analysis (Scatchard plots), denaturing gradient cell electrophoresis and Western blot, respectively. Epidermal growth factor receptor levels ranged from 388 to 33794 fmol mg 71 protein, a range that is similar to that found in head and neck tumours. The IC 50 values for cell sensitivity to ZD1839 ranged from 6 to 31 mM and a significant inverse correlation (P=0.022, r=0.82) between IC 50 values and epidermal growth factor receptor levels was observed. There was no influence of p53 status on the sensitivity to ZD1839. In two head and neck cancer cell lines with comparably elevated epidermal growth factor receptor expression, a two-fold higher ZD1839 IC 50 value was found for the one with a constitutively active mitogen-activated protein kinase. In conclusion, ZD1839 was active against cells with a range of epidermal growth factor receptor levels, although more so in cells with higher epidermal growth factor receptor expression. Activity was unaffected by p53 status, but was reduced in cells strongly dependent on epidermal growth factor receptor signalling in the presence of an intrinsically activated mitogen-activated protein kinase pathway.

Differential radiosensitisation by ZD1839 (Iressa), a highly selective epidermal growth factor receptor tyrosine kinase inhibitor in two related bladder cancer cell lines

“…EGFR expression was found to be higher in the radiosensitive S40b cell line (21.5 fmol mg À1 of protein) compared to the radioresistant MGH-U1 line (16.7 fmol mg À1 of protein), although this does not represent particularly high expression. Previous studies demonstrating an inverse correlation between the IC 50 of ZD1839 and EGFR expression are in agreement with our findings (Magne et al, 2002). However, other studies have suggested that the effects of ZD1839 on EGFR are not simply related to EGFR expression alone and may involve a complex interaction of heterodimerisation of ErbB-1 (EGFR) with other glycoprotein receptors in the subfamily such as ErbB-2 or ErbB-3 (Normanno et al, 2002).…”

“…ZD1839 has been shown to have growth inhibitory effects across a wide variety of cell types. The IC 50 for ZD1839 has been reported to be relatively cell line specific with values ranging from 0.15 to 31 mM (Ciardiello et al, 2001a;Magne et al, 2002). In our study, ZD1839 was found to have little effect on the growth characteristics of both cell lines as a single agent when studied at the doses previously reported to have significant growth inhibitory effects (Ciardiello et al, 2000).…”

Safety and pharmacokinetics of paclitaxel and the oral mTOR inhibitor everolimus in advanced solid tumours

“…p70S6 kinase inactivates the pro-apoptotic factor BAD; mTOR inhibitors or paclitaxel may promote apoptosis by preventing this inactivation. Consistent with these mechanisms, it has been shown that breast cancer cells resistant to the growth inhibiting effects of rapamycin are also resistant to its chemosensitising effects (Mondesire et al, 2004), and sequence-dependent enhancement of paclitaxel cytotoxicity has also been seen with gefitinib and trastuzumab, agents that like mTOR inhibitors inhibit growth factor signal transduction (Lee et al, 2002;Magné et al, 2002). However, in another study with cervical cancer cells, treatment with rapamycin preceding paclitaxel produced the more favourable result (Faried et al, 2006), suggesting that sequence dependency may be influenced by different mechanisms in other types of cancer.…”

Molecular mechanisms underlying the interaction between ZD1839 (‘Iressa’) and cisplatin/5-fluorouracil

“…CAL33 cells carry a p53 mutation (codon 175: CGC-CAC) and exhibit high EGFR expression (34 000 fmol mg À1 protein). CAL33 has no intrinsic mitogen-activated protein (MAP) kinase activity or k-ras mutation (Magné et al, 2002b).…”