RNAi mediated silencing of Nanog expression suppresses the growth of human colorectal cancer stem cells

Colorectal cancer (CRC) is the third most common cancer in the world known for its poor recurrence-free prognosis. Previous studies have shown that it is closely linked with cancer stem cells (CSCs), which have self-renewal potential and the capacity to differentiate into diverse populations. Nanog is an important transcription factor that functions to maintain the self-renewal and proliferation of embryonic stem cells; however, many recent studies have shown that Nanog is also highly expressed in many cancer stem cells. To investigate whether Nanog plays a crucial role in maintaining the stemness of colorectal CSCs, RNA interference was used to downregulate Nanog expression in the CRC stem cell line, EpCAM+CD44+HCT-116 cells (CCSCs). We examined the anti-tumor function of Nanog in vitro and in vivo, using small interfering RNA. Our results revealed that the Nanog mRNA expression level in CCSCs was higher than that in HCT-116 cells. We found that the depletion of Nanog inhibited proliferation and promoted apoptosis in CCSCs. In addition, the invasive ability of CCSCs was markedly restricted when Nanog was silenced by small interfering RNA. Furthermore, we found that the silencing of Nanog decreased tumor size and weight and improved the survival rate of tumor-bearing mice. In conclusion, these findings collectively demonstrate that Nanog, which is highly expressed in CRC stem cells, is a key factor in the development of tumor growth, and it may serve as a potential marker of prognosis and a novel and effective therapeutic target for the treatment of CRC.

Rabbit induced pluripotent stem cells retain capability of in vitro cardiac differentiation

Stem cells are promising cell source for treatment of multiple diseases as well as myocardial infarction. Rabbit model has essentially used for cardiovascular diseases and regeneration but information on establishment of induced pluripotent stem cells (iPSCs) and differentiation potential is fairly limited. In addition, there is no report of cardiac differentiation from iPSCs in the rabbit model. In this study, we generated rabbit iPSCs by reprogramming rabbit fibroblasts using the 4 transcription factors (OCT3/4, SOX2, KLF4, and c-Myc). Three iPSC lines were established. The iPSCs from all cell lines expressed genes (OCT3/4, SOX2, KLF4 and NANOG) and proteins (alkaline phosphatase, OCT-3/4 and SSEA-4) essentially described for pluripotency (in vivo and in vitro differentiation). Furthermore, they also had ability to form embryoid body (EB) resulting in three-germ layer differentiation. However, ability of particular cell lines and cell numbers at seeding markedly influenced on EB formation and also their diameters. The cell density at 20,000 cells per EB was selected for cardiac differentiation. After plating, the EBs attached and cardiac-like beating areas were seen as soon as 11 days of culture. The differentiated cells expressed cardiac progenitor marker FLK1 (51 ± 1.48%) on day 5 and cardiac troponin-T protein (10.29 ± 1.37%) on day 14. Other cardiac marker genes (cardiac ryanodine receptors (RYR2), α-actinin and PECAM1) were also expressed. This study concluded that rabbit iPSCs remained their in vitro pluripotency with capability of differentiation into mature-phenotype cardiomyocytes. However, the efficiency of cardiac differentiation is still restricted.

The significance of the pluripotency and cancer stem cell-related marker NANOG in diagnosis and treatment of ovarian carcinoma

Ovarian cancer is among the most common gynecologic cancers and unfortunately the most common cause of death from gynecologic malignancies. Due to few early symptoms and insufficient screening programs, an early diagnosis of ovarian cancer is very difficult and new biomarkers related to early ovarian carcinogenesis are needed. In the last years a growing scientific knowledge about cancer stem cells and their markers opened a new perspective on screening and early diagnosis of ovarian cancer. The transcription factor NANOG is not only a pluripotency and cancer stem cell-related marker, but also promotes cancer stem cell-like characteristics of tumor, tumor growth, dissemination, immune evasion, and resistance to conventional therapy. The recent data showed that small stem cells resembling very small embryonic-like stem cells are present in the ovarian surface epithelium of adult human ovaries. These cells expressed several genes related to primordial germ cells, germinal lineage, and pluripotency, including NANOG, therefore their involvement in the manifestation of ovarian cancer are not excluded. As majority of cancer cells within a tumor are non tumorigenic, the therapies targeting these cells cause tumor regression, but the survived cancer stem cells regenerate the tumor, so tumor relapse or reoccur. The eradication of cancer actually requires the elimination of cancer stem cells, therefore new strategies in treatment that specifically target cancer stem cells are urgently needed. Although the therapeutic efficacy of targeting NANOG as a cancer treatment method is still in experimental phase, the gene therapy with small interfering RNA or short hairpin RNA have already shown some promising therapeutic potential. The authors can conclude that NANOG represents a promising diagnostic marker and agent for target therapy of ovarian cancer.