Poster abstracts

Poster number 26 submitted by Jenna Karras

Fhit loss - associated neoplasia initiation and progression in vitro

Jenna R. Karras (MCDB), Morgan S. Schrock (Biomedical Sciences), Bahadir Batar (MVIMG, The Ohio State University)

Abstract:
Genomic alterations are first observed at common fragile sites in preneoplastic cells, with FRA3B being the most frequently affected locus [1,2]. The FHIT gene encompasses FRA3B, resulting in the frequent loss or reduction of Fhit protein expression in the early stages of tumorigenesis. Loss of Fhit protein expression causes a nucleotide TTP pool imbalance via TK1 down-regulation, followed by replication stress – induced DNA damage. This damage accumulates with cell division in vitro, as Chk1 is not activated leading to global genome instability [3]. Thus, Fhit, which is reduced in expression in the majority of human cancers, is a genome ‘caretaker’ whose loss initiates genome instability in preneoplastic lesions. The goal of this study was to follow this process from loss of Fhit genome caretaker function, through development of genetic alterations to isolation of clones with tumorigenic potential. We established epithelial cell lines from kidney tissues of Fhit-/- and +/+ mice early after weaning of pups, and subjected some cell lines to nutritional and carcinogen stress; the Fhit +/+ cell lines did not survive either of these additional stresses. We confirmed that supplementation of the Fhit-/- cell lines with low levels of thymidine in culture medium prevented the accumulation of DNA damage. Through transcriptome profiling and protein expression analysis, we observed changes in the p53/p21 pathway as well as epithelial to mesenchymal transition states. Additionally, some of the Fhit-deficient cell lines demonstrated anchorage-independent growth and increased invasion capacity in vitro. When injected subcutaneously and intravenously into nude mice, cells of a stressed Fhit-/- cell line formed subcutaneous tumors and lung micro-metastases that expressed Vimentin, but not Cytokeratin or E-cadherin. Thus, Fhit loss-induced genome instability results in changes in expression patterns promoting cellular transformation in vitro and in vivo.

References:
1. Gourgoulis, V.G.; Vassiliou, L.V. Nature, 2005, 434, 907-913.
2. Bartkova, J.; Horejsi, Z. Nature, 2005, 434, 864-870.
3. Saldivar, J.C.; Miuma, S. PLoS Genet, 2012, 8, e1003077.

Keywords: common fragile site, genome instability, cell transformation