Relaxin 1 and Relaxin 2 are 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 published microarray data (3-5) to discover in an unbiased manner the most significant transcriptional changes associated with trastuzumab treatment. We identified both relaxin 1 and relaxin 2, encoded by RLN1 and RLN2 as among the genes most differentially expressed in the primary tumors and tumor cells of patients with breast cancer treated with trastuzumab. The primary tumors of breast cancer patients treated with trastuzumab expressed higher levels of RLN1 and RLN2 messenger RNA than did patients not treated with trastuzumab; a single administration of trastuzumab was sufficient to result in differential expression of RLN1 in primary tumors of the breast, demonstrating increased expression of a peptide hormone important in the central nervous system and for reproduction (6-8) as a transcriptional consequence of treatment with trastuzumab.