title: Silencing oncogene expression in cervical cancer stem-like cells inhibits their cell growth and self-renewal ability.
abstract: Accumulating evidence supports the concept that cancer stem cells (CSCs) are responsible for tumor initiation and maintenance. They are also considered as an attractive target for advanced cancer therapy. Using a sphere culture method that favors the growth of self-renewal cells, we have isolated sphere-forming cells (SFCs) from cervical cancer cell lines HeLa and SiHa. HeLa-SFCs were resistant to multiple chemotherapeutic drugs and were more tumorigenic, as evidenced by the growth of tumors following injection of immunodeficient mice with 1 × 10(4) cells, compared with 1 × 10(6) parental HeLa cells required to grow tumors of similar size in the same time frame. These cells showed an expression pattern of CD44(high)/CD24(low) that resembles the CSC surface biomarker of breast cancer. We further demonstrated that HeLa-SFCs expressed a higher level (6.9-fold) of the human papillomavirus oncogene E6, compared with that of parental HeLa cells. Gene silencing of E6 with a lentiviral-short-hairpin RNA (shRNA) profoundly inhibited HeLa-SFC sphere formation and cell growth. The inhibition of cell growth was even greater than that for sphere formation after E6 silence, suggesting that the loss of self-renewing ability may be more important. We then measured the expression of self-renewal genes, transformation growth factor-beta (TGF-β) and leukemia-inhibitory factor (LIF), in shRNA-transduced HeLa-SFCs and found that expression of all three TGF-β isoforms was significantly downregulated while LIF remained unchanged. Expression of the Ras gene (a downstream component of TGF-β) was also markedly decreased, suggesting that the growth-inhibitory effect could be via the TGF-β pathway. The above data indicate RNA interference-based therapy may offer a new approach for CSC-targeted cancer therapy.
authors: Australian Research Council Centre of Excellence for Functional Nanomaterials and Australian Institute for Bioengineering and Nanotechnology, University of Queensland, Brisbane, Queensland, Australia. w.gu@uq.edu.au
authors: W
authors: W
authors: Gu
authors: E
authors: E
authors: Yeo
authors: N
authors: N
authors: McMillan
authors: C
authors: C
authors: Yu
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D015316:Genetic Therapy / Q000379:methods*; D006367:HeLa Cells; D006801:Humans; D053605:Leukemia Inhibitory Factor / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D014411:Neoplastic Stem Cells / Q000821:virology*; D009856:Oncogene Proteins, Viral / Q000037:antagonists & inhibitors* / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics*; D018874:Spheroids, Cellular / Q000821:virology*; D016212:Transforming Growth Factor beta / Q000378:metabolism; D002583:Uterine Cervical Neoplasms / Q000628:therapy*
chemical_list: D004268:DNA-Binding Proteins; C052603:E6 protein, Human papillomavirus type 18; C052633:E7 protein, Human papillomavirus type 18; C507837:LIF protein, human; D053605:Leukemia Inhibitory Factor; D009856:Oncogene Proteins, Viral; D034741:RNA, Small Interfering; D016212:Transforming Growth Factor beta