Trastuzumab supports transcription of genes associated with proliferation in human breast cancer.
The mechanism of action associated with trastuzumab function in breast cancer is thought to involve binding of the Fab domain of trastuzumab to the extracellular portion of the human epidermal growth factor receptor 2 (HER2) (1), but the transcriptional changes induced by signals transduced by this binding event are less described. We mined published and public microarray data (2-5) to understand in an unbiased fashion and at the systems level genes most differentially expressed in the tumors of breast cancer patients treated with trastuzumab. We discovered significant perturbation of genes associated with cell proliferation - most significantly but not restricted to the proliferating cell nuclear antigen, PCNA. Significant transcriptional induction of PCNA in the primary tumors of patients with breast cancer following administration of trastuzumab alludes to a seemingly paradoxical role for trastuzumab in support of tumor cell proliferation in human breast cancer.