Future Roles of Lapatinib in ErbB2-Positive Breast Cancer: Adjuvant and Neoadjuvant Trials

Dual HER2-targeted approaches in HER2-positive breast cancer

Approximately 15-20% of all breast cancers are human epidermal growth factor receptor 2 (HER2) positive, with clinical studies having validated the HER2 receptor tyrosine kinase pathway as an important therapeutic target. Presently, two HER2-targeted therapies are approved by the Food and Drug Administration for treatment of HER2-positive breast cancer: the HER2-targeted humanized monoclonal antibody trastuzumab and the small-molecule tyrosine kinase inhibitor lapatinib. Despite use of these HER2-targeted agents, many patients still experience disease progression. For this reason, numerous new agents and therapeutic strategies are under investigation. Based on preclinical data suggesting synergistic effects from dual therapy targeting HER2, clinical trials that test the effects of combining anti-HER2 agents have been conducted and are ongoing. Here, we review recently presented data from several clinical trials, which indicate that the strategy of combining HER2 blockade therapies can offer greater clinical efficacy, with adverse effects of varying degrees. Specifically, we review new data reported at the 2010 San Antonio Breast Cancer Symposium (SABCS 2010), including the phase II NeoSphere and phase III NeoALTTO clinical trials, and data from three clinical trials reported at the 2011 American Society of Clinical Oncology (ASCO 2011) meeting. Together these trials elucidate the potential role of combining trastuzumab with lapatinib or pertuzumab. We also discuss additional ongoing studies that will help further define the role of dual HER2 blockade therapies and its impact on clinical practice.

Effect of the tyrosine kinase inhibitor lapatinib on CUB-domain containing protein (CDCP1)-mediated breast cancer cell survival and migration

The surface receptor CUB domain-containing protein 1 (CDCP1) is highly expressed in several adenocarcinomas and speculated to participate in anchorage-independent cell survival and cell motility. Tyrosine kinase phosphorylation seems to be crucial for intracellular signaling of CDCP1. Lapatinib, a tyrosine kinase inhibitor (TKI), is approved for treatment of HER-2/neu overexpressing metastatic breast cancer and functions by preventing autophosphorylation following HER-2/neu receptor activation. This study aimed to investigate the effect of CDCP1 expression on anchorage-independent growth and cell motility of breast cancer cells. Moreover, studies were performed to examine if lapatinib provided any beneficial effect on HER-2/neu((+)/-)/CDCP1(+) breast cancer cell lines. In our studies, we affirmed that CDCP1 prevents cells from undergoing apoptosis when cultured in the absence of cell-substratum anchorage and that migratory and invasive properties of these cells were decreased when CDCP1 was down-regulated. However, only HER-2/neu(+), but not HER-2/neu((+)/-) cells showed decreased proliferation and invasion and an enhanced level of apoptosis towards loss of anchorage when treated with lapatinib. Therefore, we conclude that CDCP1 might be involved in regulating adhesion and motility of breast cancer cells but that lapatinib has no effect on tyrosine kinases regulating CDCP1. Nonetheless, other TKIs might offer therapeutic approaches for CDCP1-targeted breast cancer therapy and should be studied considering this aspect.