Inhibition of proliferation and induction of apoptosis in breast cancer cells by the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor ZD1839 (‘Iressa’) is independent of EGFR expression level

Abstract

High expression of the epidermal growth factor receptor (EGFR) in breast carcinoma confers a growth advantage to the tumor cells. The EGFR tyrosine kinase inhibitor (EGFR-TKI) ZD1839 ('Iressa') has clinical activity in a wide range of tumor types, although the mechanism(s) by which it exerts its antitumor activity effects remain unclear. We analyzed the ability of ZD1839 to induce apoptosis and/or inhibition of proliferation in breast carcinoma cell lines, as well any association between this ability and the downregulation activity of MAPK and Akt, two recently proposed markers of ZD1839 activity. Proliferation, survival, and activation of Akt and MAPK were evaluated in six human breast cancer cell lines expressing various levels of EGFR and HER2 and exposed to ZD1839. EGFR and HER2 expression levels were determined using specific monoclonal antibodies and FACS analysis. The effects of ZD1839 were independent of EGFR expression levels, but were influenced by high HER2 expression. ZD1839 significantly reduced the rate of [3H]-thymidine incorporation in the four sensitive cell lines, while apoptosis was also induced in two of these cell lines. No correlation was found between the cytostatic or cytotoxic effects of ZD1839 and its ability to downregulate MAPK and Akt activity in the tumor cell lines. Our data suggest that the antitumor activity of ZD1839 is due to a cytostatic effect, and involves apoptosis induction in a subset of sensitive cells only, and that neither MAPK nor Akt is a reliable marker of ZD1839 activity.

Effects of the combined blockade of EGFR and ErbB-2 on signal transduction and regulation of cell cycle regulatory proteins in breast cancer cells

“…In agreement with these findings, co-expression of EGFR, ErbB-2 and ErbB-3 was also found to have a negative synergistic effect on patient outcome, independent of tumor size or lymph node status [9]. Different anti-EGFR agents, including the EGFR tyrosine kinase inhibitor (EGFR-TKI) gefitinib (ZD1839, Iressa), have shown to inhibit the growth of human breast carcinoma cells [10][11][12][13][14]. We and other research groups have demonstrated that breast cancer cell lines with high levels of expression of ErbB-2 are more sensitive to gefitinib as compared with ErbB-2-negative cells [11][12][13][14].…”

“…Different anti-EGFR agents, including the EGFR tyrosine kinase inhibitor (EGFR-TKI) gefitinib (ZD1839, Iressa), have shown to inhibit the growth of human breast carcinoma cells [10][11][12][13][14]. We and other research groups have demonstrated that breast cancer cell lines with high levels of expression of ErbB-2 are more sensitive to gefitinib as compared with ErbB-2-negative cells [11][12][13][14]. However, clinical studies of gefitinib in breast cancer resulted in few clinical responses and in a disease control rate of approximately 10% [15][16][17].…”

An Apoferritin‐based Drug Delivery System for the Tyrosine Kinase Inhibitor Gefitinib

“…As a negative control MDA-MB-231 cell line was used which does not express HER2 but expresses high levels of EGFR. [ 24 ] Cellular internalization of H-AFt-encapsulated-Gefi tinib was observed by confocal microscopy and compared to that of Gefi tinib. SKBR3 and MDA-MB-231 cells were treated with H-AFt-encapsulated-Gefi tinib, Gefi tinib, and H-AFt (5 × 10 −6 M ) for 24 h ( Figure 2 ; Section S2, Supporting Information).…”

“…Gefi tinib activity requires a phosphorylated (active) form of EGFR whereas MDA-MB-231 cells express nonphosphorylated EGFR and hence are not sensitive to this drug. [ 24 ] On the other hand, cancer cells that express low levels of EGFR together with overexpression of HER2 are sensitive to this drug and indeed, high sensitivity of SKBR3 cells to Gefi tinib was observed. [ 24,25 ] HER2 remains the preferred dimerization partner of other ErbB receptors.…”

“…[ 20,22,23 ] Gefi tinib is used for treatment of EGFR and HER2 overexpressing breast cancers. [ 24,25 ] However, the therapeutic window of this drug is drastically narrowed by poor bioavailability, acquired resistance due to insuffi cient or ineffective cellular uptake and systemic toxicity resulting from interactions between drug and healthy tissue. [ 19,26 ] Also, orally administered Gefi tinib is taken up extensively by human serum albumin and hence other delivery systems such as liposomes have been investigated.…”