Breast Cancer — Loss of PTEN Predicts Resistance to Treatment

A new study uncovers a mechanism by which trastuzumab (Herceptin) counters the progression of cancer. The findings point to a subgroup of patients who are likely to have a response to treatment. A new study uncovers a mechanism by which trastuzumab counters the progression of cancer. The findings point to a subgroup of patients who are likely to have a response to treatment. PTEN, the lipid phosphatase and tensin homologue, is a key tumor suppressor. Mutations resulting in the loss of PTEN or the loss of its function are common and functionally relevant in tumors of different histologic origins, including breast cancer. 1 A recent study by Nagata and colleagues 2 shows that PTEN not only antagonizes tumorigenesis but also sensitizes breast cancers to targeted therapy with trastuzumab (Herceptin), a humanized monoclonal antibody against ErbB2 (also referred to as HER2/neu), a membrane-receptor tyrosine kinase in the epidermal growth factor receptor family. 3 PTEN normally opposes the activation of the proto-oncogenic phosphatidylinositol 3' kinase (PI3K)–Akt signaling pathway . . .