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

Abstract

#2130 Co-expression of EGFR and ErbB-2 occurs in a subset of primary breast carcinoma, and it is associated with worse prognosis. We previously demonstrated that treatment of breast cancer cells that express both receptors with a combination of the EGFR tyrosine kinase inhibitor gefitinib (G) and the anti-ErbB-2 monoclonal antibody herceptin (H) results in a synergistic anti-tumor effect. Such combination failed to show significant activity in a phase I/II clinical trial. However, patients enrolled in this trial were not selected for expression of EGFR. We explored the molecular mechanisms involved in the synergism of G and H in breast cancer cells. Treatment of both SK-BR-3 and BT-474 cells with a combination of G+H produced a more significant reduction of AKT and p42/p44-MAPK (MAPK) activation as compared with treatment with a single agent. The combination also produced a more prolonged blockade of both signalling pathways. In agreement with these findings, treatment with G+H induced a more pronounced accumulation of cells in the G0/G1 phase of the cell cycle as compared with treatment with a single drug. A sub-G0/G1 peak, suggestive of apoptosis, was evident in cells treated with the combination but not with G or H. The combination of G+H produced a more significant increase in the levels of p27kip1 and of hypophosphorylated forms of pRb2, and a more significant decrease in the levels of Cyclin D1 and survivin as compared with a single agent. Analysis of p27kip1 protein stability, in presence of the protein synthesis inhibitor cycloheximide, revealed that both G and the combination of G+H significantly increased the stability of p27kip1, with the combination showing higher effects. Furthermore, breast cancer cells treated with the combination expressed higher levels of p27kip1 mRNA as compared with cells treated with a single drug. The combination also induced a significant increase in the nuclear levels of the FKHRL-1 transcription factor that was not observed in cells treated with G or H alone. Treatment of breast cancer cells with the dual EGFR/ErbB-2 inhibitor lapatinib produced an increase in the levels of p27kip1 and of hypophosphorylated pRb2, and a decrease in the levels of Cyclin D1 and survivin comparable to that observed following treatment with the combination of G+H. In addition, an increase in p27kip1 mRNA and in the nuclear levels of FKHRL-1 was induced in breast cancer cells by treatment with lapatinib. These findings suggest that the synergistic anti-tumor effects deriving from EGFR and ErbB-2 blockade are mediated by significant alterations in the expression of cell cycle regulatory proteins, including transcriptional and post-transcriptional regulation of p27kip1 expression. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2130.

miR-1470 mediates lapatinib induced p27 upregulation by targeting c-jun

“…1C). This result was in accordance with the study reported by D'Alessio et al that treatment with lapatinib produced a significance increase in the nuclear levels of p27 and Forkhead box O3 box O3 (D'Alessio et al, 2010).…”

Lapatinib in Breast Cancer - The Predictive Significance of Her1 (Egfr), Her2, Pten and Pik3ca Genes and Lapatinib Plasma Level Assessment

“…In a study by Reis-Filho et al 69 , which assessed 47 metaplastic cancers, HER1 amplification showed a significant association with HER1 overexpression and was restricted to cancers with homologous metaplasia. Coexpression of HER1 and HER2 has been observed in 10-36% primary BC, and it is associated with a poorer prognosis than in cases with expression of a single receptor [74][75][76][77] . In one study, where HER1 expression was found in only 15% of 807 invasive BC, the majority of HER1-positive tumors (87%) coexpressed HER2.…”

Levels of p27 Sensitize to Dual PI3K/mTOR Inhibition

“…Reversal of this effect by pharmacologic blockade of the PI3K signaling cascade is predicted to restore cell-cycle regulation and consequently diminish tumor cell growth and improve the clinical outcome of the patient (17). Indeed, an increase in nuclear p27 upon drug administration has been associated with induction of G 0 -G 1 arrest following treatment of tumor cells with several chemotherapeutic compounds, including the tyrosine kinase enzymes inhibitors imatinib mesylate (Gleevec), lapatinib (Tyverb), and mitogen-activated protein kinase/extracellular signal-regulated kinase inhibitor PD98059 (18)(19)(20). p27 is rarely deleted or mutated in human cancers but its level of expression is reduced in the vast majority of human cancers, phenomenon that associates with poor clinical outcome in several malignancies, including cancers of the breast, colon, prostate, and ovary, among others (21).…”