Estimating stem cell fractions

14 Cancers arise as a result of genetic and epigenetic alterations. These accumulate in cells during the 15 processes of tissue development, homeostasis and repair. Many tumor types are hierarchically orga16 nized and driven by a sub-population of cells often called cancer stem cells. Cancer stem cells are 17 uniquely capable of recapitulating the tumor and can be highly resistant to radioand chemotherapy 18 treatment. We investigate tumor growth patterns from a theoretical standpoint and show how signif19 icant changes in preand post-therapy tumor dynamics are tied to the dynamics of cancer stem cells. 20 We identify two characteristic growth regimes of a tumor population that can be leveraged to estimate 21 cancer stem cell fractions in vivo using simple linear regression. Our method is a mathematically exact 22 result, parameter free and does not require any microscopic knowledge of the tumor properties. A 23 more accurate quantification of the direct link between the sub-population driving tumor growth and 24 treatment response promises new ways to individualize treatment strategies. 25 1 . CC-BY-NC 4.0 International license peer-reviewed) is the author/funder. It is made available under a The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/013672 doi: bioRxiv preprint first posted online Jan. 11, 2015;