Abstract 4330: Endometrial hyperplasia resulting from myeloid-specific targeting of the tumor suppressor APC

Abstract

Abstract The Adenomatous polyposis coli (APC1) tumor suppressor is a multi-function protein with a central role in Wnt-regulated cell growth and differentiation. Additionally, APC functions to modulate microtubule and microfilament dynamics to establish polarity in epithelia during directed cell migration and asymmetric cell division. APC frequently collaborates with the canonical Diaphanous-related formin, mDia1 (DIAPH1), which also binds microfilaments and microtubules to modulate cytoskeletal dynamics. APC1 and DIAPH1 are genetically linked on chromosome 5q in a region frequently disrupted in myeloproliferative neoplasms (MPNs). mDia1 knockout mice develop an age-dependent outgrowth of myeloid-lineage cells. The physical and functional linkage of APC and mDia1 as 5q tumor suppressors and in cytoskeletal remodeling led us to explore the role of APC in tumor suppression in myeloid-derived cell lineages affected by mDia1 knockout. To test this hypothesis in a genetic model, we created a mouse in which APC was knocked out in myeloid lineage cells by breeding the Apc-flox mice with mice expressing Cre recombinase under the control of lysozyme M (LyzsM) gene promoter. The resulting phenotype was unexpected and 100% penetrant: Female mice developed cystic endometrial hyperplasia and were unable to sustain pregnancy. Embryo implantation occurred, but embryos were resorbed mid-gestation irrespective of progeny genotype. Two hypothesized mechanisms to explain the initiation of endometrial hyperplasia are being pursued. The first hypothesis is that loss of APC impairs the homeostasis between growth and differentiation of myeloid lineage stem/progenitor cells that transdifferentiate into uterine epithelia. An alternate hypothesis is that loss of APC expression affects the inflammatory response of resident uterine macrophages that lead to defects in epithelial morphology. In either case, these genetic studies imply that APC gene defects in myeloid lineage cells may be an initiating event in endometrial cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4330. doi:10.1158/1538-7445.AM2011-4330