PHF20 is differentially expressed in the tumors of breast cancer patients treated with trastuzumab.
Trastuzumab (Herceptin) is a monoclonal antibody targeting the extracellular domain of the human epidermal growth factor receptor 2 (HER2) (1) utilized for the treatment of adjuvant and metastatic breast cancer (2) in the United States and worldwide. We mined public and published microarray data (3, 4) to discover in an unbiased manner the most significant transcriptional changes associated with trastuzumab treatment. We identified the plant homeodomain (PHD) finger protein 20, PHF20, as among the genes most differentially expressed in the primary tumors of patients with breast cancer treated with trastuzumab. The primary tumors of breast cancer patients treated with trastuzumab expressed lower levels of PHF20 messenger RNA than did patients not treated with trastuzumab, demonstrating decreased primary tumor expression of an epigenetic molecule which is described to stabilize and activate the tumor suppressor p53 (5) as a direct or indirect transcriptional consequence of treatment with trastuzumab.