Active glutamine utilization is a major biochemical feature of most tumor cells and is fundamental for the survival and proliferation of tumor cells.Glutaminolysis represents the first and rate-limiting step of glutamine utilization,which is catalyzed by glutaminases.The oncogenic pathway activated by c-Myc has been reported to regulate glutamine utilization by increasing the expression of glutaminase and glutamine transporter.Whether other oncogenic signaling pathways promote glutamine utilization in tumors remains elusive.Breast cancer is the second most common cause of death for women in the United States and ErbB2 activation is one of the major causes of breast cancers.Using MCF 10A and MCF 10A-derived NeuT cells, we studied the effect of ErbB2 activation on glutaminase expression,and found that ErbB2 activation increased glutaminase 1 expression at both mRNA and protein levels.Knockdown of ErbB2 decreased glutaminase 1 expression in several human ErbB2-positive cell lines.In addition, blocking ErbB2 signaling pathway by trastuzumab reduced the expression levels of glutaminase 1.Importantly, ErbB2-mediated upregulation of glutaminase 1 was independent of c-Myc expression in MCF 10A cells.Activation of either PI3K/Akt or MAPK pathway was not sufficient to up-regulate glutaminase 1 expression;instead, inhibition of NF-κB pathway down-regulated glutaminase 1 expression whereas stimulation of NF-κB induced glutaminase 1 expression.Finally,inhibition of glutaminase activity significantly decreased human breast cancer cell proliferation.Taken together, our data indicate that ErbB2 activation promotes glutaminase 1 expression by PI3K/Akt-independent activation of NFκB in breast cancer cells, identifying another oncogenic pathway which stimulates glutamine utilization in tumor cells.These findings will facilitate the identification of novel targets for cancer diagnosis and treatment.