Exon 8 amplification of epidermal growth factor receptor (EGFR) in invasive breast carcinomas

Can EGFR be a therapeutic target in breast cancer?

Epidermal growth factor receptor (EGFR) is highly expressed in certain cancer types and is involved in regulating the biological characteristics of cancer progression, including proliferation, metastasis, and drug resistance. Various medicines targeting EGFR have been developed and approved for several cancer types, such as lung and colon cancer. To date, however, EGFR inhibitors have not achieved satisfactory clinical results in breast cancer, which continues to be the most serious malignant tumor type in females. Therefore, clarifying the underlying mechanisms related to the ineffectiveness of EGFR inhibitors in breast cancer and developing new EGFR-targeted strategies (e.g., combination therapy) remain critical challenges. Various studies have demonstrated aberrant expression and maintenance of EGFR levels in breast cancer. In this review, we summarize the regulatory mechanisms underlying EGFR protein expression in breast cancer cells, including EGFR mutations, amplification, endocytic dysfunction, recycling acceleration, and degradation disorders. We also discuss potential therapeutic strategies that act directly or indirectly on EGFR, including reducing EGFR protein expression, treating the target protein to mediate precise clearance, and inhibiting non-EGFR signaling pathways. This review should provide new therapeutic perspectives for breast cancer patients with high EGFR expression.

Epidermal growth factor receptor gene copy number may predict lapatinib sensitivity in HER2-positive metastatic breast cancer

OBJECTIVE

Lapatinib, a dual HER2/EGFR tyrosine kinase inhibitor (TKI), associated to capecitabine represents the treatment of choice in HER2-positive metastatic breast cancer (BC) patients in progression after trastuzumab-based therapy. Though lapatinib-based therapy prolongs the time to progression, its efficacy is often limited by the development of drug resistance. It is aimed to evaluate novel biomarkers predictive of lapatinib response, we analyzed EGFR protein and gene status in a series of 50 metastatic HER2-positive BC patients.

METHODS

Lapatinib was given at 1250 mg/day continuously and capecitabine at 2000 mg/m(2)/day every 3 weeks. EGFR protein expression and gene copy number (GCN) were assessed by immunohistochemistry and FISH, respectively. Receiver operating curve (ROC) analysis identified the value of > 3.36 EGFR copies/nucleus as the cut-off point able to discriminate responders versus non-responders.

RESULTS

A statistical significant correlation between EGFR GCN value > 3.36 and response to lapatinib (p = 0.01) was found. Cox regression analysis further supported these findings evidencing that HER2 score 3+ and EGFR GCN increase are positive predictor factors of lapatinib response.

CONCLUSIONS

Though further investigations are needed to confirm these findings, EGFR GCN could be a suitable screening to identify the subset of BC patients particularly responsive to the dual TKI lapatinib.