German scientists from the Max Planck Institute, T. Cantz et al., reported in the November 12th online edition of Stem Cells, the results of their study on the expression of the transcription factor Oct4 in tumor cell lines derived from human cancers. The investigators conducted the study in order to bring clarity to the discrepancy in previous studies regarding Oct4 expression in tumors and its role in carcinogenesis and tumor formation. With HeLa (cervical cancer), MCF7 (breast cancer) and nTera (teratoma) human cell lines, the investigators detected the presence of Oct4 in the nucleus of HeLa and MCF7 cells by immunohistochemical staining with monoclonal antibodies. However, the researchers were unable to detect Oct4 signaling by Western blot analysis nor Oct4 mRNA by RT-PCR. It was also noted that the Oct4 promoter region was highly methylated, indicating that Oct4 expression was suppressed. The authors speculated from their results that reports of Oct4 expression in cancer cell lines could be explained by either psuedogene expression or misinterpretation of background signals in the immunofluorescence experiments.

Japanese scientists F. Ishikawa et al. from the RIKEN Research Center for Allergy and Immunology reported in the October 21st online edition of Nature Biotechnology the results of their study on characterizing leukemic stem cells (LS) from human acute myelogenous leukemic cells implanted into newborn non-obese diabetic immunodeficient interleukin-2 γ^null (NOD/SCID) mice. In this animal model, the investigators discovered that the human tumor cells engrafted within the osteoblast-rich area of the bone marrow as well as recapitulate the AML and the ability to self-renew. It was also noted that the AML were not responsive to chemotherapies which induce apoptosis. The reseachers speculated that quiescence of the human LS may be the underlying mechanisms responsible for the cancer cells' resistance to cytotoxic therapy. The authors concluded that their results provide a useful AML xenograft model for developing "novel therapeutic strategies" which target LS cells.

Scientists from the University of Michigan, C. Ginestier et al., reported in today's (Nov. 15) issue of Cell Stem Cell the isolation and characterization of normal and cancer stem cells in human mammary tissues. The investigators found that cells with aldehyde dehydrogenase (ALDH) activity in both normal and cancer mammary epithelial cells were associated with a subpopulation of stem and progenitor cells. For example, normal ALDH expressing cells were found to be multipotent and formed xenografts in immunocompromised animals. Additionally, a subpopulation of cells from breast carcinoma expressing the ALDH marker were found to be tumorigenic, capable of self-renewal, and upon transplantation they could recapitulate the heterogeneous cancer cell population residing in the newly formed tumors. The investigators also noted that ALDH1 positive immunostaining of cells in 577 breast carcinoma samples correlated with poor prognosis. The authors concluded that their findings provide new tools for clinically evaluating patients with breast cancers.