Project Summary
Metastasis, the dissemination of cancer cells from the primary tumor to secondary sites, is the leading cause of
cancer-related mortality. Metastasis is a multistep process, culminating in formation of clinically detectable tumor
foci at distant organs. However, only a subpopulation of cancer cells within the primary tumor is capable of
completing the entire metastatic cascade, as they must be dissemination-competent and contain tumor-initiating
or stemlike capabilities. This deadly population of cells express high levels of MenaINV, a pro-metastatic isoform
of the actin-regulatory protein Mena, and are capable of using doorways for intravasation and dissemination
called Tumor Microenvironment of Metastasis (TMEM) sites. Preliminary studies lead to the hypothesis that the
NF-kB signaling pathway may be a critical regulator of both the expression of Mena and stemness in cancer
cells, promoting intravasation through blood vessels, through interactions with macrophages and through
crosstalk with the Notch1 signaling pathway. These are very complex and context dependent signals. Therefore,
while imaging tumors in live mice, these studies will use biosensors to determine the downstream consequences
of NF-kB activation on Mena expression and stemness in tumor cells which are actively intravasating through
TMEM. We will use two models of breast cancer metastasis, where human or mouse breast cancer cells are
injected into mice and allowed to grow tumors. The mice express fluorescently labelled macrophages and
endothelial cells. We will implant an imaging window over the tumor allowing for imaging at single-cell resolution
of the tumor cells in the native tumor microenvironment. Depending on the experiment, the tumor cells will
express biosensors to monitor activation of NF-kB signaling, stemness, and Mena promoter activity. Aim 1 will
determine if activation of NF-kB signaling in tumor cells following collision with macrophages causes a distinct
cellular phenotype compared to activation of NF-kB signaling without collision with macrophages. Whether
inhibition of notch signaling through macrophage-tumor cell contact affects activation of NF-kB signaling will also
be tested. Aim 2 will monitor the timing and order that the NF-kB, stemness, and Mena biosensors are activated
to determine which signals promote the formation of the deadly intravasation competent and stem-like cells. The
mice will then be treated with or without NF-kB inhibitors to examine if NF-kB signaling controls the activation of
stemness or Mena expression, and if NF-kB signaling is required for intravasation of tumor cells through TMEM.
Deciphering the mechanisms that produce a population of tumor cells that are both stem and intravasation-
competent is critical to further our understanding of metastasis. The research environment in the Condeelis Lab
at The Albert Einstein College of Medicine offers outstanding opportunities for training, collaborations, scientific
discussions, and career development. The proposed studies and training plan developed in this proposal will
instruct on mouse models of metastasis, biosensor development, and large volume high resolution intravital
imaging techniques, ensuring mastery of all the tools needed to establish an independent lab.