A System to Study Aneuploidy In Vivo

Aneuploidy, an imbalanced chromosome number, is associated with both cancer and developmental disorders such as Down syndrome (DS). To determine how aneuploidy affects cellular and organismal physiology, we have developed a system to evaluate aneuploid cell fitness in vivo. By transplanting hematopoietic stem cells (HSCs) into recipient mice after ablation of recipient hematopoiesis by lethal irradiation, we can directly compare the fitness of HSCs derived from a range of aneuploid mouse models with that of euploid HSCs. This experimental system can also be adapted to assess the interplay between aneuploidy and tumorigenesis. We hope that further characterization of aneuploid cells in vivo will provide insight both into the origins of hematopoietic phenotypes observed in DS individuals as well as the role of different types of aneuploid cells in the genesis of cancers of the blood.National Institutes of Health (U.S.) (Grant GM056800

Aneuploidy impairs hematopoietic stem cell fitness and is selected against in regenerating tissues in vivo

Aneuploidy, an imbalanced karyotype, is a widely observed feature of cancer cells that has long been hypothesized to promote tumorigenesis. Here we evaluate the fitness of cells with constitutional trisomy or chromosomal instability (CIN) in vivo using hematopoietic reconstitution experiments. We did not observe cancer but instead found that aneuploid hematopoietic stem cells (HSCs) exhibit decreased fitness. This reduced fitness is due at least in part to the decreased proliferative potential of aneuploid hematopoietic cells. Analyses of mice with CIN caused by a hypomorphic mutation in the gene Bub1b further support the finding that aneuploidy impairs cell proliferation in vivo. Whereas nonregenerating adult tissues are highly aneuploid in these mice, HSCs and other regenerative adult tissues are largely euploid. These findings indicate that, in vivo, mechanisms exist to select against aneuploid cells.National Institutes of Health (U.S.) (CA206157)Kathy and Curt Marble Cancer Research FundDavid H. Koch Institute for Integrative Cancer Research at MIT (Support Grant P30-CA14051)National Institute of General Medical Sciences (U.S.) (Training Grant T32GM007753

An in vivo evaluation of aneuploid hematopoietic stem cell fitness

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2016.Cataloged from PDF version of thesis. "February 2016."Includes bibliographical references.Aneuploidy is an unbalanced cell state associated with developmental conditions such as Down syndrome (DS) as well as cancer, a disease of rapid proliferation. Studies of yeast, mouse and human cells harboring one extra chromosome have demonstrated that aneuploid cells show a number of common phenotypes in vitro, notably decreased proliferation. However, the precise role of aneuploidy in cancer has yet to be elucidated, in part due to lack of systematic in vivo model systems. Furthermore, evaluation of aneuploidy-associated phenotypes in vivo has been difficult because autosomal trisomy is generally embryonic lethal in mice. Here, I have evaluated hematopoietic stem cells (HSCs) derived from three aneuploid mouse models in vivo, two models of autosomal trisomy and one model of chromosome instability. By performing hematopoietic reconstitutions, I found that aneuploid HSCs have a range of fitness in vivo that correlates with the amount of extra DNA in each line. My results demonstrate that aneuploidy-associated cellular phenotypes are observed in vivo and in the context of a euploid organism. Additionally, I found that aneuploidy is well tolerated in the hematopoietic lineage under normal conditions in two of the three mouse models analyzed. However, even these relatively fit aneuploid cells begin to show more severe phenotypes upon repeated proliferative challenge. In humans, DS is associated with perturbations in the hematopoietic system, often resulting in childhood leukemia. Trisomy is also frequently observed in non-DS leukemias. Establishment of this model system enables future systematic dissection of the source of aneuploidy-associated fitness defects in vivo both in hematopoiesis and in the context of cancer.by Sarah Jeanne Pfau.Ph. D

Aneuploid Cell Survival Relies upon Sphingolipid Homeostasis

Aneuploidy, a hallmark of cancer cells, poses an appealing opportunity for cancer treatment and prevention strategies. Using a cell-based screen to identify small molecules that could selectively kill aneuploid cells, we identified the compound N-[2hydroxy-1-(4-morpholinylmethyl)-2-phenylethyl]-decanamide monohydrochloride (DL-PDMP), an antagonist of UDP-glucose ceramide glucosyltransferase. DL-PDMP selectively inhibited proliferation of aneuploid primary mouse embryonic fibroblasts and aneuploid colorectal cancer cells. Its selective cytotoxic effects were based on further accentuating the elevated levels of ceramide, which characterize aneuploid cells, leading to increased apoptosis. We observed that DL-PDMP could also enhance the cytotoxic effects of paclitaxel, a standard-of-care chemotherapeutic agent that causes aneuploidy, in human colon cancer and mouse lymphoma cells. Our results offer pharmacologic evidence that the aneuploid state in cancer cells can be targeted selectively for therapeutic purposes, or for reducing the toxicity of taxane-based drug regimens.National Cancer Institute (U.S.) (Grant P30-CA14051