Knockdown of E2F2 Inhibits Tumorigenicity, but Preserves Stemness of Human Embryonic Stem Cells

Abstract

Tumorigenicity of human pluripotent stem cells is a major threat limiting their application in cell therapy protocols. It remains unclear, however, whether suppression of tumorigenic potential can be achieved without critically affecting pluripotency. A previous study has identified hyperexpressed genes in cancer stem cells, among which is E2F2, a gene involved in malignant transformation and stem cell self-renewal. Here we tested whether E2F2 knockdown would affect the proliferative capacity and tumorigenicity of human embryonic stem cells (hESC). Transient E2F2 silencing in hESC significantly inhibited expression of the proto-oncogenes BMI1 and HMGA1, in addition to proliferation of hESC, indicated by a higher proportion of cells in G1, fewer cells in G2/M phase, and a reduced capacity to generate hESC colonies in vitro. Nonetheless, E2F2-silenced cells kept expression of typical pluripotency markers and displayed differentiation capacity in vitro. More importantly, E2F2 knockdown in hESC significantly inhibited tumor growth in vivo, which was considerably smaller than tumors generated from control hESC, although displaying typical teratoma traits, a major indicator of pluripotency retention in E2F2-silenced cells. These results suggest that E2F2 knockdown can inhibit hESC proliferation and tumorigenicity without significantly harming stemness, providing a rationale to future protocols aiming at minimizing risks related to therapeutic application of cells and/or products derived from human pluripotent cells.

MiR-218 Inhibited Growth and Metabolism of Human Glioblastoma Cells by Directly Targeting E2F2

“…For instance, reduced activity of E2F2 in T cells results in evidently accelerated rates of proliferation of cancer cells, but this phenomenon was not observed in E2F1 or E2F3 (Opavsky et al 2007). However, time-course analysis in a recent study (Suzuki et al 2014) reported that cell proliferation of viable tumor cells is significantly reduced in vitro after E2F2 is silenced. Furthermore, Ning Wu et al illustrated that inhibition of E2F2 expression arrests cell division in the G1 phase in gliomas (Wu et al 2012).…”

“…According to prediction analysis, we found that E2F2 was a potential target of miR-218 based on the evidence that E2F2 was upregulated in glioma (Suzuki et al 2014), and it could regulate the cell cycle and tumor cell proliferation. We performed dual luciferase reporter assay to prove this hypothesis.…”

“…E2F2 regulates cell cycle and proliferation, and it is related to tumorigenesis of many cancers (Reimer et al 2006(Reimer et al , 2007. A recent study confirmed that E2F2 is overexpressed in glioblastoma, which promotes tumorigenesis in gliomas (Suzuki et al 2014). …”

Embryonic Stem Cells Promoting Macrophage Survival and Function are Crucial for Teratoma Development

“…Various strategies developed to reduce this risk of teratoma formation include prolonged pre-differentiation of ESCs in vitro , blocking signaling pathways that promote proliferation, induction of apoptosis of proliferative ESCs, sorting cells expressing precursor markers, and deleting undifferentiated ESCs immunologically, genetically, and chemically (7–18). However, it is difficult to obtain a yield of 100% pure differentiated stem cells for transplantation: the contamination of grafts with undifferentiated cells can give rise to teratoma formation (19–21).…”

Comparação do potencial terapêutico de células mesenquimais e pericitos em modelo murino de distrofia muscular

“…As células-tronco pluripotentes induzidas (induced Pluripotent Stem cells -iPS) foram criadas na tentativa de se obterem células com maior potencialidade a partir de células adultas (Takahashi & Yamanaka 2006), evitando assim o problema ético das embrionárias. Porém, a segurança de seu uso para a terapia celular ainda é duvidosa visto que para serem obtidas são utilizados vírus e pró-oncogenes durante a transformação da célula adulta, e apesar de alguns estudos procurarem formas de capacitar o uso dessas células para a terapia (Suzuki et al 2014), elas são em geral usadas como modelos in vitro para estudos de doenças que têm difícil acesso ao tecido de interesse, como as doenças neurológicas (Robinton & Daley 2013).…”