Chromosomal influence on hybrid cell proliferation

Mouse embryonic stem cells maintain differentiation potency into somatic lineage despite alternation of ploidy

Vertebrates, including mammals, are considered to have evolved by whole genome duplications. Although some fish have been reported to be polyploids that have undergone additional genome duplication, there have been no reports of polyploid mammals due to abnormal development after implantation. Furthermore, as the number of physiologically existing tetraploid somatic cells is small, details of the functions of these ploidy-altered cells are not fully understood. In this present study, we aimed to clarify the details of the differentiation potency of tetraploids using tetraploid embryonic stem cells. To clarify the differentiation potency, we used mouse tetraploid embryonic stem cells derived from tetraploid embryos. We presented tetraploid embryonic stem cells differentiated into neural and osteocyte lineage in vitro and tetraploid cells that contributed to various tissues of chimeric embryos ubiquitously in vivo. These results revealed that mouse embryonic stem cells maintain differentiation potency after altering the ploidy. Our results provide an important basis for the differentiation dynamics of germ layers in mammalian polyploid embryogenesis.

Cell fusion potentiates tumor heterogeneity and reveals circulating hybrid cells that correlate with stage and survival

High lethality rates associated with metastatic cancer highlight an urgent medical need for improved understanding of biologic mechanisms driving metastatic spread and identification of biomarkers predicting late-stage progression. Numerous neoplastic cell intrinsic and extrinsic mechanisms fuel tumor progression; however, mechanisms driving heterogeneity of neoplastic cells in solid tumors remain obscure. Increased mutational rates of neoplastic cells in stressed environments are implicated but cannot explain all aspects of tumor heterogeneity. We present evidence that fusion of neoplastic cells with leukocytes (for example, macrophages) contributes to tumor heterogeneity, resulting in cells exhibiting increased metastatic behavior. Fusion hybrids (cells harboring hematopoietic and epithelial properties) are readily detectible in cell culture and tumor-bearing mice. Further, hybrids enumerated in peripheral blood of human cancer patients correlate with disease stage and predict overall survival. This unique population of neoplastic cells provides a novel biomarker for tumor staging, as well as a potential therapeutic target for intervention.

Use of chromosome microdissection, the polymerase chain reaction, and dot blot hybridization to analyze double minute chromosomes

The potential usefulness of chromosome microdissection, the polymerase chain reaction (PCR), and dot blot hybridization as a quick screening method for determining the genetic composition of double minute chromosomes (DMs) was evaluated. DMs or abnormally banding regions (ABRs) were microdissected from multidrug-resistant hamster cell lines and amplified with PCR using primers specific for the hamster multidrug-resistance (MDR) gene, pgp 1. The microdissected-PCR-amplified products were shown to (a) hybridize to a 32P-labeled pCHP1 probe for the hamster MDR gene by using dot blot or Southern blot analysis and also (b) hybridize back to the chromosome region from which they were originally dissected by using fluorescent in situ hybridization. Microdissected/PCR-amplified DMs were also shown to hybridize to ABRs. When microdissected DMs and ABRs were amplified using hamster specific Alu primers, the resulting material was shown to hybridize with probes for hamster MDR and Alu. These results suggest that the DMs contained in these MDR hamster cell lines contain Alu-like sequences and the chromosome microdissection-PCR-hybridization approach might be used as a quick screening method for identifying genes amplified in DMs and ABRs in cell lines and human tumor samples.