HPV16-E2 protein modifies self-renewal and differentiation rate in progenitor cells of human immortalized keratinocytes.

BACKGROUND: Cervical cancer is the fourth cause of death worldwide by cancer in women and is a disease associated to persistent infection with human papillomavirus (HPV), particularly from two high-risk types HPV16 and 18. The virus initiates its replicative cycle infecting cells located in the basal layer of the epithelium, where a small population of epithelial stem cells is located performing important functions of renewal and maintenance of the tissue. Viral E2 gene is one of the first expressed after infection and plays relevant roles in the replicative cycle of the virus, modifying fundamental processes in the infected cells. Thus, the aim of the present study was to demonstrate the presence of hierarchic subpopulations in HaCaT cell line and evaluate the effect of HPV16-E2 expression, on their biological processes. METHODS: HaCaT-HPV16-E2 cells were generated by transduction of HaCaT cell line with a lentiviral vector. The α6-integrin-CD71 expression profile was established by immunostaining and flow cytometric analysis. After sorting, cell subpopulations were analyzed in biological assays for self-renewal, clonogenicity and expression of stemness factors (RT-qPCR). RESULTS: We identified in HaCaT cell line three different subpopulations that correspond to early differentiated cells (α6-integrindim), transitory amplifying cells (α6-integrinbri/CD71bri) and progenitor cells (α6-integrinbri/CD71dim). The last subpopulation showed stem cell characteristics, such as self-renewal ability, clonogenicity and expression of the well-known stem cell factors SOX2, OCT4 and NANOG, suggesting they are stem-like cells. Interestingly, the expression of HPV16-E2 in HaCaT cells changed its α6-integrin-CD71 immunophenotype modifying the relative abundance of the cell subpopulations, reducing significantly the percentage of α6-integrinbri/CD71dim cells. Moreover, the expression of the stem cell markers was also modified, increasing the expression of SOX2 and NANOG, but decreasing notably the expression of OCT4. CONCLUSIONS: Our data demonstrated the presence of a small subpopulation with epithelial "progenitor cells" characteristics in the HaCaT cell line, and that HPV16-E2 expression on these cells induces early differentiation.

Selection of a MCF-7 Breast Cancer Cell Subpopulation with High Sensitivity to IL-1ß: Characterization of and Correlation between Morphological and Molecular Changes Leading to Increased Invasiveness.

Cancer and inflammation are closely related in tumor malignancy prognosis. Breast cancer MCF-7 cells have a poor invasive phenotype, although, under IL-1ß stimulus, acquire invasive features. Cell response heterogeneity has precluded precise evaluation of the malignant transition. MCF-7A3 cells were selected for high sensitivity to IL-1ß stimulus, uniform expression of CXCR4, and stability of IL1-RI. Structural changes, colony formation ability, proliferation rate, chemotaxis, Matrigel invasion, E-cadherin mRNA expression and protein localization were determined in these cells and in MCF-7 parental cells under the stimulus of IL-1ß. Selected MCF-7A3 cells showed a uniform response to IL-1ß stimulation increasing features of invasive cells such as scattering, colony formation, proliferation, chemokinesis and invasion. Basal expression of E-cadherin mRNA was higher, and IL-1ß stimulus had no further effect at early times of cytokine exposure. Total E-cadherin levels remained unchanged in parental cells, whereas levels decreased, as MCF-7A3 cells became fibroblastoid or scattered. Triton X-100 soluble/insoluble E-cadherin ratios were highly increased in these cells, while, in MCF-7pl cells, ratios could not be correlated with morphology changes. MCF-7A3 cells uniform response to IL-1ß allowed characterization of changes induced by the cytokine that had not been assessed when using heterogeneous cell lines.