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Supplementary Figures 1-2 from Tip30 Deletion in MMTV-Neu Mice Leads to Enhanced EGFR Signaling and Development of Estrogen Receptor–Positive and Progesterone Receptor–Negative Mammary Tumors

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posted on 2023-03-30, 20:31 authored by Chengliang Zhang, Mikito Mori, Shenglan Gao, Aimin Li, Isamu Hoshino, Mark D. Aupperlee, Sandra Z. Haslam, Hua Xiao
Supplementary Figures 1-2 from Tip30 Deletion in MMTV-Neu Mice Leads to Enhanced EGFR Signaling and Development of Estrogen Receptor–Positive and Progesterone Receptor–Negative Mammary Tumors

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ARTICLE ABSTRACT

Estrogen receptor–positive and progesterone receptor–negative (ER+/PR−) breast cancers account for 15% to 25% of all human breast cancers and display more aggressive malignant characteristics than ER+/PR+ cancers. However, the molecular mechanism underlying development of ER+/PR− breast cancers still remains elusive. We show here that Tip30 deletion dramatically accelerated the onset of mammary tumors in the MMTV-Neu mouse model of breast cancer. The mammary tumors arising in Tip30−/−/MMTV-Neu mice were exclusively ER+/PR−. The growth of these ER+/PR− tumors depends not only on estrogen but also on progesterone despite the absence of detectable PR. Tip30 is predominantly expressed in ER+ mammary epithelial cells, and its deletion leads to an increase in the number of phospho-ERα–positive cells in mammary glands and accelerated activation of Akt in MMTV-Neu mice. Moreover, we found that Tip30 regulates the EGFR pathway through controlling endocytic downregulation of EGFR protein level and signaling. Together, these findings suggest a novel mechanism in which loss of Tip30 cooperates with Neu activation to enhance the activation of Akt signaling, leading to the development of ER+/PR− mammary tumors. Cancer Res; 70(24); 10224–33. ©2010 AACR.

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