Epidermal growth factor-receptor activation modulates Src-dependent resistance to lapatinib in breast cancer models

Abstract

IntroductionSrc tyrosine kinase overactivation has been correlated with a poor response to human epidermal growth factor receptor 2 (HER2) inhibitors in breast cancer. To identify the mechanism by which Src overexpression sustains this resistance, we tested a panel of breast cancer cell lines either sensitive or resistant to lapatinib.MethodsTo determine the role of Src in lapatinib resistance, we evaluated the effects of Src inhibition/silencing in vitro on survival, migration, and invasion of lapatinib-resistant cells. In vivo experiments were performed in JIMT-1 lapatinib-resistant cells orthotopically implanted in nude mice. We used artificial metastasis assays to evaluate the effect of Src inhibition on the invasiveness of lapatinib-resistant cells. Src-dependent signal transduction was investigated with Western blot and ELISA analyses.ResultsSrc activation was higher in lapatinib-resistant than in lapatinib-sensitive cells. The selective small-molecule Src inhibitor saracatinib combined with lapatinib synergistically inhibited the proliferation, migration, and invasion of lapatinib-resistant cells. Saracatinib combined with lapatinib significantly prolonged survival of JIMT-1-xenografted mice compared with saracatinib alone, and impaired the formation of lung metastases. Unexpectedly, in lapatinib-resistant cells, Src preferentially interacted with epidermal growth factor receptor (EGFR) rather than with HER2. Moreover, EGFR targeting and lapatinib synergistically inhibited survival, migration, and invasion of resistant cells, thereby counteracting Src-mediated resistance. These findings demonstrate that Src activation in lapatinib-resistant cells depends on EGFR-dependent rather than on HER2-dependent signaling.ConclusionsComplete pharmacologic EGFR/HER2 inhibition is required to reverse Src-dependent resistance to lapatinib in breast cancer.

Role of ESR Pathway Genes in Breast Cancer: A Review

“…As mentioned previously, Src is a protein that cooperates with numerous proteins in breast cancer to promote tumor progression. This conclusion concurs with the implication that there is a functional crosstalk between EGFR and Src in the onset of lapatinib, an inhibitor of EGFR and HER 2, resistance [40]. Although much research has been done on investigating Src and the effects of its inhibi- …”

Mechanisms of lapatinib resistance in HER2-driven breast cancer

“…In fact, SFK inhibitors partially blocked PI3K activation in resistant cells and restored sensitivity to lapatinib in resistant xenografts [33]. Recently, we demonstrated that Src over-activation is coupled with increased interaction with EGFR rather than with HER2 in breast cancer cell lines with constitutive or acquired resistance to lapatinib [34]. Consistent with Src over-activation in lapatinibresistant breast cancer cells, the Src-dependent tyrosine phosphorylation levels of EGFR were increased.…”

“…We also found that inhibition of EGFR by the monoclonal antibody cetuximab and inhibition of Src by the small molecule saracatinib, synergistically inhibits survival of lapatinib-resistant cells when combined with lapatinib. In particular, the combination of cetuximab with lapatinib is effective, both in vitro and in vivo, in reducing signaling transduction under the control of EGFR/HER2 [34].…”

ESE-1 Knockdown Attenuates Growth in Trastuzumab-resistant HER2+ Breast Cancer Cells

“…The baseline Src activation observed in the resistant sublines, especially in Pool2, corroborates with previous findings, which showed that Src activation following IGFR phosphorylation is a compensatory response in these particular cell types 10 . An early increase in Src activation in response to trastuzumab treatment has far reaching implications in cases of resistance arising from trastuzumab and other tyrosine kinase inhibitors, such as lapatinib or gefitnib 20 . Upregulation in Src or mTOR expression leading to aberrant Akt signaling is one of many mechanisms of lapatinib resistance 20,21 .…”

“…An early increase in Src activation in response to trastuzumab treatment has far reaching implications in cases of resistance arising from trastuzumab and other tyrosine kinase inhibitors, such as lapatinib or gefitnib 20 . Upregulation in Src or mTOR expression leading to aberrant Akt signaling is one of many mechanisms of lapatinib resistance 20,21 . A therapeutic strategy for cancers that are refractory to anti-ERBB2 and/or anti-EGFR therapy is therefore to use mTOR or Src inhibitors, in combination with anti-HER inhibitors 1 .…”