Metastasis is the major cause of death in breast cancer patients. However, the molecular mechanisms underlying tumor initiation and metastasis are not clear. We have recently identified tumor initiation cells (TICs) from human breast tumors. TICs carry certain properties of stem cells, are more resistant to conventional cancer therapies, and are involved in tumor metastasis. How to effectively target TICs or metastasis initiating cells (MICs) thus becomes one of the most propelling questions. Endogenous single strand small RNAs of 20- 22 nucleotides in length, known as microRNAs (miRNAs, miRs), have emerged to be powerful regulators of tumor progression. In this project, we aim to characterize novel miRs that regulate human breast cancer initiation and metastasis and identify their target genes. Then in our future endeavors, we will examine miR regulation mechanisms at the transcriptional level and further translate our understanding to clinical applications, such as novel cancer biomarkers or therapeutics. Most previous metastasis models are limited in their ability to fully represent human tumors, due to genetic changes accumulated in culture for human cancer cell lines, genetic differences in mouse tumor models compared to human tumors, and bypassing the natural steps of metastasis via bloodstream inoculations. This project will take advantage of our recently established human-in-mouse breast cancer models, which are derived from clinical tumor specimens and develop spontaneous lung or lymph node metastases upon orthotopic transplantation into mouse mammary fat pads. To closely monitor breast tumor initiation and metastasis in vivo, we have also transduced primary cancer cells with optical reporters and improved the detection sensitivity to 10 cells in vivo via non-invasive bioluminescence imaging. MiRs are more stable and resistant to analysis protocols than mRNAs, thus serving as promising novel cancer biomarkers. Furthermore, they are endogenous small RNAs with little toxicity compared to compound drugs;therefore hold the promise to be developed as innovative cancer therapeutics. Our long-term goal is to combine our understanding of tumor initiation and metastasis with knowledge in multi- disciplinary technology (such as chemistry and bioengineering) to improve clinical medicine and reduce cancer mortality.

Public Health Relevance

Using patient tumor-derived human breast cancer models, this project aims to identify a novel network of microRNAs and their target genes critical for breast cancer initiation and/or metastasis. Newly identified microRNAs are promising candidates for novel biomarkers and therapeutics for cancer medicine. I am a permanent resident in the United States. I am in my 5th year of postdoctoral training at The University of Chicago, and am ready to make a timely transition to an independent investigator upon completing the one-year mentored phase. This application proposes a 1-year mentored phase (100% effort) and a 3-year independent phase (80% effort) to complete the research and training goals.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Career Transition Award (K99)
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Subcommittee G - Education (NCI)
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Schmidt, Michael K
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University of Chicago
Internal Medicine/Medicine
Schools of Medicine
United States
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Bockhorn, Jessica; Prat, Aleix; Chang, Ya-Fang et al. (2014) Differentiation and loss of malignant character of spontaneous pulmonary metastases in patient-derived breast cancer models. Cancer Res 74:7406-17
Bockhorn, Jessica; Yee, Kathy; Chang, Ya-Fang et al. (2013) MicroRNA-30c targets cytoskeleton genes involved in breast cancer cell invasion. Breast Cancer Res Treat 137:373-82
Bockhorn, Jessica; Dalton, Rachel; Nwachukwu, Chika et al. (2013) MicroRNA-30c inhibits human breast tumour chemotherapy resistance by regulating TWF1 and IL-11. Nat Commun 4:1393