Project:
Macrophage-Mediated Delivery of the Breast Tumor Suppressor HoxD10 via Autologous Transfer to Breast Tumors

Principal Investigators - Nancy Boudreau, PhD, and Lisa Coussens, PhD

ABSTRACT

Breast cancer development is accompanied by a progressive loss of epithelial cell polarity and growth control, infiltration of macrophages and angiogenesis. Whereas the master morphoregulatory gene HoxD10 is highly expressed in normal breast epithelial cells and in quiescent vascular endothelium and fibroblasts, invasive breast tumors progressively lose HoxD10 in both breast epithelium and angiogenic endothelial cells. Significantly, restoration of HoxD10 into metastatic breast epithelial cells results in a "normal" polarized phenotype accompanied by growth arrest and diminished tumor formation in vivo, and directly restoring expression of HoxD10 in angiogenic endothelium blocks angiogenesis. Moreover, HoxD10 also suppresses expression of chemokines that recruit leukocytes to tumors. Thus, HoxD10 is a potent breast tumor suppressor-type protein that directly impacts epithelial cells and stabilizes the tumor microenvironment by inhibiting angiogenesis and inflammation, indicating that methods to restore HoxD10 expression to mammary tumors in vivo would have tremendous therapeutic potential. Since macrophages are actively recruited to developing breast tumors, and isolated, cultured monocytes actively home back to mammary tumors following autologous transfer, we propose to exploit them as carriers of HoxD10 to breast tumor tissues. We will isolate and transfect mammary tumor macrophages ex vivo with an expression vector producing a secreted form of HoxD10 (sHoxD10) that retains an endogenous sequence functionally similar to other protein transduction domains that facilitate protein transport across plasma membranes and nuclear translocation in tumors. Autologous sHoxD10-expressing monocytes/macrophages will also be labeled ex vivo with DiD, a lipophilic carbocyanine fluorochrome, and transferred (i.v.) back into mammary-tumor bearing MMTV-PymT mice in both early and late stages of tumor progression. This will enable ex vivo monitoring of monocytes/macrophages and their homing via optical imaging of the DiD and evaluate sHoxD10 uptake in malignant mammary tissues and determine its efficacy in thwarting aggressive tumor growth stromal invasion, inflammatory cell recruitment and angiogenesis.