Establishing Cell Lifespans in Cancer and Normal Breast

Institution: University of California, Davis
Investigator(s): Alexander Borowsky, M.D. -
Award Cycle: 2012 (Cycle 18) Grant #: 18IB-0016 Award: $155,728
Award Type: IDEA
Research Priorities
Biology of the Breast Cell>Pathogenesis: understanding the disease

Initial Award Abstract (2012)

Breast cancer is a diverse disease, and the tumors are made up of cells that display different behaviors. One of the populations of cells in a breast tumor is referred to as cancer stem cells (CSCs). This population of cells behaves similar to normal stem cells in that it displays the property of self-renewal. Breast CSCs have been isolated from human tumor samples before by using specific cell surface markers. CSCs are much more efficient at forming tumors in mice models than other tumor cell populations from the tumor. Additionally, CSCs are believed to contribute to both the resistance of breast cancer to current therapies and to metastasis.

Our objective in this study is to distinguish the CSC population from the bulk tumor cells in human samples and compare the age of the two populations using carbon-14 (14C) “bomb pulse dating” analyzed by accelerator mass spectrometry (AMS). 14C bomb pulse dating measures the 14C present in the DNA of cells. 14C levels on earth were relatively constant over long time periods except for the spike that occurred from 1955-1963 as a result of extensive above ground nuclear weapons testing. The 14C rapidly reacted with oxygen in the atmosphere to form carbon dioxide (CO2) gas and evenly distributed throughout the atmosphere and was incorporated into every living thing. By consuming plants and animals, the level of 14C in our body parallels what is present in the atmosphere. Genomic DNA in a cell is relatively stable once a cell has divided, therefore the level of 14C in the DNA will reflect the level of 14C in the atmosphere when the cell last divided. This methodology has been used to answer many fundamental questions of turnover in cells of the brain, fat, heart, pancreas and teeth.

By understanding the turnover of the CSC population in breast cancer, we will answer a fundamental question in the controversial field of CSCs. 14C bomb pulse dating is the only methodology that allows for the determination of turnover of a population of cells isolated directly from a human sample without any manipulation or delivery of chemicals before the measurement. This study would be the first application of 14C bomb pulse dating in a diseased tissue.

Final Report (2015)

This project aimed to further our understanding of breast cancer stem cells (BCSCs). Current therapy for breast cancer using a combination of surgery, radiotherapy and chemotherapy still results in about 40% of breast cancer patients that will have disease recurrence. Breast cancer stem cells (BCSCs) have been hypothesized to be responsible for this, as these cells may be resistant to current therapies and the repopulate the tumor after treatment. Our objective in this study was to distinguish the BCSC population from the bulk tumor in human breast tumors and compare the age of the two populations using carbon-14 (14C) bomb pulse dating with accelerator mass spectrometry (AMS). The underlying hypothesis to be tested was: Mammary stem cells and breast cancer stem cells are long-lived and slowly dividing as compared to non-stem progenitor cells, “transit amplifying” cells, or other populations of differentiated and/or neoplastic mammary epithelium. This project had three aims which included the isolation, characterization and carbon dating of breast cancer stem cells.

We have made progress on all three aims of the project. The most significant barrier that we needed to overcome was the low level of cancer stem cells in breast cancer tissue. We expect that with the combination of changing our sample acquisition and improvements in AMS sample introduction, we can overcome this challenge. Although we do not yet have any accomplishments that could be considered “major”, we have already submitted a letter of intent to the Department of Defense (DoD) to continue this research project. The scope of the DoD project would be an extension of this current project, but does not overlap with the existing goals of this project.