The increased glycolysis in cancer cells has been well accepted to be an important process to support malignant phenotypes. Previous reports have shown that lactate dehydrogenase A (LDH-A), an enzyme in the glycolytic pathway, and heat shock factor 1 (HSF1), a multifunctional transcription factor, play critical roles in cancer cell development and regulation of glucose metabolism. Overexpression of the oncogene ErbB2 increases the transformation and invasion/metastatic potentials of breast cancers. However, only recently has data emerged that directly links ErbB2 to increased glycolysis. The mechanism underling ErbB2-mediated glycolysis and the role of ErbB2-mediated glycolysis in cancer development remains poorly understood. Our preliminary data have demonstrated that: 1) overexpression of ErbB2 promotes glycolysis in human breast cancer cells, 2) overexpression of ErbB2 transcriptionally activates LDH-A and promotes glycolysis, 3) overexpression of ErbB2 upregulates HSF1 through a post-transcriptional control mechanism, 4) ErbB2 upregulates LDH-A through HSF1, and 5) Herceptin, an ErbB2-targeting antibody, effectively inhibits metabolism-regulating PI3K/Akt/mTOR signaling and HSF1 expression. Based on previous reports and our preliminary studies, we hypothesize that in human breast cancer cells ErbB2 upregulates LDH-A through HSF1. This pathway plays an important role in promoting ErbB2-mediated glycolysis and cancer development. Inhibition of glycolysis will at least partially reverse ErbB2-mediated malignant behavior, and the combination of Herceptin, which inhibits ErbB2, with a glycolysis inhibitor will better inhibit ErbB2-overexpressing breast cancer cells. We will test these hypotheses through the pursuit of the following specific aims: Aim 1: To study the role of HSF1 in ErbB2-enhanced glycolysis, cell transformation, and invasion. Aim 2: To study the mechanism of upregulation of HSF1 by ErbB2. Aim 3: To study the mechanism of upregulation of LDH-A by HSF1. Aim 4: To determine whether the combination of an ErbB2- targeting agent with glycolysis inhibitors will enhance inhibition of transformation and invasion/metastasis of ErbB2-overexpressing breast cancers. Successful completion of the proposed studies will provide a better understanding of the impact of ErbB2-increased glycolysis on breast cancer transformation and invasion/metastasis and will substantially augment our knowledge of the molecular mechanisms underlying ErbB2-mediated glycolysis. Furthermore, new insights into the unique ErbB2-mediated metabolism in breast cancer cells that result from these studies may lead to a more effective targeted cancer therapy for treating ErbB2-overexpressing cancers.