Understanding how variations in nuclear size after whole genome doubling affect tumorigenesis - Project Summary
Cancer is characterized by genomic, epigenetic, and metabolic changes, but also by a failure in cell/nuclear size
control. Nevertheless, little is known about size regulation in cancer cells and whether failures in size control
contribute to tumorigenesis. Whole genome doubling (WGD), which results in tetraploidy and is a frequent
intermediate event in tumor progression, is a key process that can alter cell and nuclear size. However, while
ploidy and nuclear size tend to scale proportionally in normal human cells, DNA content and nuclear size do not
always correlate in cancer cells. This suggests that understanding how nuclear size is controlled following
changes in DNA content may uncover important mechanisms underlying tumorigenesis. Addressing this issue
requires a suitable experimental model, such as the one that will be used for this project. This model consists of
a panel of tetraploid (4N) clonal cell lines that were derived by inducing WGD in colorectal and breast cancer
cells and can be divided into two groups (small and large) based on nuclear size. Previous studies showed that
the small and large 4N DLD1 clones display distinct mitotic phenotypes, which raised important questions about
the mechanisms of size control in 4N cells and the impact of nuclear size on other cell phenotypes. Indeed,
preliminary results indicate that the small 4N clones have increased tumor-like behavior in vitro, outperforming
the large 4N clones and 2N parental cells in soft agar colony formation assays. These size-specific phenotypic
differences suggest that the small 4N clones may also be more tumorigenic in vivo than the large 4N clones due
to their ability to restrict nuclear size scaling after WGD. This hypothesis will be tested in a first research aim
using a combination of in vitro, in vivo, and in silico methods and two experimental models, including the novel
panel of small and large 4N clones derived from 2N DLD1 cells (for a running total of 16 cell lines) and genomic,
histopathology, and clinical data from The Cancer Genome Atlas (TCGA). A second research aim will test the
hypothesis that the nuclear volumes of the 4N clones are dictated by the degree of genomic compaction and will
identify the transcriptional and epigenetic mechanisms that regulate nuclear size after WGD in colon- and breast-
derived cells. These experiments will address a fundamental yet underexplored question of whether variations
in nuclear size have important functional consequences that contribute to tumor formation following WGD. The
findings of this project could be leveraged for cancer diagnostics and unveil new cancer therapeutic targets. This
project will provide ample training opportunities in the use of animal models, computational analysis, and mass
spectrometry from an interdisciplinary group of leading researchers to help the applicant become an independent
scientist. The intellectual environment, resources, and training programs provided to the applicant are rich and
complementary to the proposed research project. Moreover, the collective institutional environment is strongly
supportive of multidisciplinary research, and it is instrumental to the success of the proposed studies and
scientific development of the applicant.
