siRNA targeting Notch-1 decreases glioma stem cell proliferation and tumor growth

Abstract

Glioblastoma multiforme (GBM), the most common brain tumor in adults, is neurologically destructive and has a dismal response to virtually all therapeutic modalities. One phenomenon that can contribute to this complexity is the presence of a relatively small subset of glioma stem cells (GSCs) within the tumor and the activation of pathways that control cellular differentiation. The Notch signaling pathway, which is responsible for maintaining a balance between cell proliferation and apoptosis, is believed to be deregulated in cancer stem cells (CSCs), leading to tumor growth through the generation or expansion of CSCs. In this study, Notch-1 small interfering RNA (siRNA) was used to silence Notch-1 gene expression in GSCs. An MTT assay demonstrated inhibitory effects on the proliferation of GSCs in vitro. Real-time PCR showed that Notch-1 expression levels were markedly decreased in GSCs transfected with Notch-1 siRNA in vitro. Notch-1 silenced GSCs engrafted on Balb/c nude mice showed a significantly greater reduction in oncogenicity than the control group (P < 0.05). Furthermore, direct intratumoral injections of Notch-1-siRNA/PEI significantly delayed the growth of pre-established tumors in nude mice (P < 0.05). These results suggest that siRNA-mediated silencing of the Notch-1 gene may represent a novel target for gene therapy of GBM.

Level of Notch activation determines the effect on growth and stem cell-like features in glioblastoma multiforme neurosphere cultures

“…36,[40][41][42] NSC and bCSC are commonly identified by their sphere forming capacity in culture, and thus the number of spheres formed in primary culture from acutely dissociated tumor tissue can be interpreted as a semi-quantification of the bCSC population in the tumor tissue sample. A correlation between primary neurosphere formation and survival of glioma patients has been suggested 69,70 and it has been shown that the vast majority of GBM tumors could be established and maintained as neurosphere cultures, whereas lower grade gliomas mostly lacked this ability.…”

“…16,[33][34][35][36][37][38] Furthermore, it has been suggested that Notch activity plays a central role in bCSC survival, tumorigenicity, and resistance mechanisms. 36,[39][40][41][42][43][44] In the present study, we seek to further dissect the relevance of Notch signaling in bCSC by investigating the importance of an active Notch pathway in GBM neurosphere cultures. We show that human-derived GBM xenograft cells cultured during NSC conditions in vitro contain cells with NSC-like characteristics.…”

Cancer stem cells: a challenging paradigm for designing targeted drug therapies

“…The pathway is deregulated in CSCs, which results in generation of tumors because of the expansion of CSCs (Table 2). Wang et al demonstrated that introduction of Notch-1-specific siRNA in GSCs resulted in a drastic decrease in Notch-1 expression levels and inhibited the proliferation of GSC in vitro [136]. Moreover, GSCs with silenced Notch-1 exhibited a dramatic reduction in oncogenicity when xenografted into Balb/c nude mice.…”

Asymmetric cell division: Implications for glioma development and treatment

“…Therefore, Notch signaling likely plays an important role in tumor associated angiogenesis and its inhibition may be beneficial in treating astrocytoma. When Notch 1 is inhibited in stem-like TPC, their tumorigenicity is impaired when injected into Balb/c nude mice [169]. Furthermore, siRNA knockdown of NOTCH1 in established tumors significantly slowed the cancerous growth when compared to control tumors [169].…”