Stem Cell Dynamics and Heterogeneity: Implications for Epidermal Regeneration and Skin Cancer

Esophageal cancer stem cells express PLGF to increase cancer invasion through MMP9 activation

Cancer stem cells (CSCs) are a distinct population in tumors and cause cancer relapse and metastasis. Thus, treating CSCs are believed to be potential to cure rapidly growing and highly metastatic cancers. To date, CSCs in esophageal cancer have not been characterized. In the current study, we detected significant higher levels of placental growth factor (PLGF) and matrix metalloproteinase 9 (MMP9) in the esophageal cancers with metastasis, compared to those without metastasis, in which the expression levels of PLGF and MMP9 strongly correlated with each other. Thus, we used a human esophageal cancer cell line, TE-1, to examine the cross talk of PLGF and MMP9. We found that the levels of PLGF in TE-1 cells positively affected the levels of MMP9, while the levels of MMP9 did not affected the levels of PLGF, suggesting that PLGF may activate MMP9 in esophageal cancer cells. Then, we separated PLGF-positive and PLGF-negative TE-1 cells that had been transfected with a GFP reporter under a PLGF promoter by flow cytometry. We found that PLGF-positive cells grew significantly faster than PLGF-negative cells both in vitro and in vivo in a stereotactical implantation model, suggesting that PLGF-positive cells are likely CSCs in esophageal cancer. Taken together, we demonstrate that PLGF-positive cells appear to be CSCs in esophageal cancer, and they may release PLGF to promote cancer metastasis through MMP9 activation.

Protein Kinase C ε , Which Is Linked to Ultraviolet Radiation-Induced Development of Squamous Cell Carcinomas, Stimulates Rapid Turnover of Adult Hair Follicle Stem Cells

To find clues about the mechanism by which kinase C epsilon (PKCε) may impart susceptibility to ultraviolet radiation (UVR)-induced development of cutaneous squamous cell carcinomas (SCC), we compared PKCε transgenic (TG) mice and their wild-type (WT) littermates for (1) the effects of UVR exposures on percent of putative hair follicle stem cells (HSCs) and (2) HSCs proliferation. The percent of double HSCs (CD34+ and α6-integrin or CD34+/CD49f+) in the isolated keratinocytes were determined by flow cytometric analysis. Both single and chronic UVR treatments (1.8 kJ/m²) resulted in an increase in the frequency of double positive HSCs in PKCε TG mice as compared to their WT littermates. To determine the rate of proliferation of bulge region stem cells, a 5-bromo-2′-deoxyuridine labeling (BrdU) experiment was performed. In the WT mice, the percent of double positive HSCs retaining BrdU label was 28.4 ± 0.6% compared to 4.0 ± 0.06% for the TG mice, an approximately 7-fold decrease. A comparison of gene expression profiles of FACS sorted double positive HSCs showed increased expression of Pes1, Rad21, Tfdp1 and Cks1b genes in TG mice compared to WT mice. Also, PKCε over expression in mice increased the clonogenicity of isolated keratinocytes, a property commonly ascribed to stem cells.