for any who may have become resistant to the herceptin/lapatinib combination

[Lani]

research is pointing the way toward a clinical trial

There are already Src inhibitors (dasatinib is one which is already FDA approved for CML), so progress may not be so far away if trials start up quickly



Research article
beta1 Integrin mediates an alternative survival pathway in breast cancer cells resistant to lapatinib
Catherine Huang, Catherine C Park, Susan G Hilsenbeck, Robin Ward, Mothaffar Rimawi, Yen-chao Wang, Jiang Shou, Mina J Bissell, C Kent Osborne and Rachel Schiff
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Breast Cancer Research 2011, 13:R84 doi:10.1186/bcr2936
Published: 31 August 2011
Abstract (provisional)
Introduction
The overexpression of human epidermal growth factor receptor (HER)-2 in 20% of human breast cancers and its association with aggressive growth has led to widespread use of HER2-targeted therapies such as trastuzumab (T) and lapatinib (L). Despite the success of these drugs, their efficacy is limited in patients whose tumors demonstrate de novo or acquired resistance to treatment. The beta1 integrin resides on the membrane of the breast cancer cell, activating several elements of breast tumor progression including proliferation and survival.

Methods
We developed a panel of HER2-overexpressing cell lines resistant to L, T, and the potent LT combination through long-term exposure and validated these models in 3D culture. Parental and L/T/LT-resistant cells were subject to HER2 and beta1 integrin inhibitors in 3D and monitored for 12 days, followed by quantification of colony number. Parallel experiments were conducted where cells were either stained for Ki-67 and TUNEL or harvested for protein and analyzed by immunoblot. Results were subject to statistical testing using analysis of variance and linear contrasts, followed by adjustment with the Sidak method.

Results
Using multiple cell lines including BT474 and HCC1954, we reveal that in L and LT resistance, where phosphorylation of EGFR/HER1, HER2, and HER3 are strongly inhibited, kinases downstream of beta1 integrin--including focal adhesion kinase (FAK) and Src--are upregulated. Blockade of beta1 by the antibody AIIB2 abrogates this upregulation and functionally achieves significant growth inhibition of L and LT resistant cells in 3D, without dramatically affecting the parental. SiRNA against beta1 as well as pharmacologic inhibition of FAK achieve the same growth inhibitory effect. In contrast, trastuzumab-resistant cells, which retain high levels of phosphorylated EGFR/HER1, HER2, and HER3, are only modestly growth-inhibited by AIIB2.

Conclusions
Our data suggest that HER2 activity, which is suppressed in resistance involving L but not T alone, dictates whether beta1 mediates an alternative pathway driving resistance. Our findings justify clinical studies investigating the inhibition of beta1 or its downstream signaling moieties as strategies to overcome acquired L and LT resistance.