Inhibition of cervical cancer cell growth in vitro and in vivo with dual shRNAs

Knocking down Insulin Receptor in Pancreatic Beta Cell lines with Lentiviral-Small Hairpin RNA Reduces Glucose-Stimulated Insulin Secretion via Decreasing the Gene Expression of Insulin, GLUT2 and Pdx1

Type 2 diabetes (T2D) is a metabolic disorder characterized by beta cell dysfunction and insulin resistance in fat, muscle and liver cells. Recent studies have shown that the development of insulin resistance in pancreatic beta cell lines may contribute to beta cell dysfunction in T2D. However, there still is a lack of detailed investigations regarding the mechanisms by which insulin deficiency may contribute in diabetes. In this study, we firstly established a stable insulin receptor knockdown cell line in pancreatic beta cells INS-1 (InsRβKD cells) using anti InsRβ small hairpin RNA (InsRβ-shRNA) encoded by lentiviral vectors. The resultant InsRβKD cells demonstrated a significantly reduced expression of InsRβ as determined by real-time PCR and Western blotting analyses. Upon removing glucose from the medium, these cells exhibited a significant decrease in insulin gene expression and protein secretion in response to 20 mM glucose stimulation. In accordance with this insulin reduction, the glucose uptake efficiency as indicated by a ³[H]-2-deoxy-d-glucose assay also decreased. Furthermore, InsRβKD cells showed a dramatic decrease in glucose transporter 2 (GLUT2, encoded by SLC2A2) and pancreatic duodenal homeobox (Pdx1) mRNA expression compared to the controls. These data collectively suggest that pancreatic beta cell insulin resistance contributes to the development of beta cell dysfunction by impairing pancreatic beta cell glucose sensation through the Pdx1- GLUT2 pathway. InsRβKD cells provide a good model to further investigate the mechanism of β-cell dysfunction in T2D.

Chondromodulin-1 ameliorates osteoarthritis progression by inhibiting HIF-2α activity

OBJECTIVES

Hypoxia is known to stabilize hypoxia-inducible factor (HIF) and initiate angiogenic signaling cascade. However, cartilage living in hypoxia environment can maintain avascularity. It is well known that abrogation of avascularity is related to cartilage degradation in osteoarthritis (OA). The aims of present study were to investigate the role of chondromodulin-1 (ChM-1), an endogenously anti-angiogenic protein in cartilage, during chondrocyte maturation and OA progression, as well as to explore the molecular mechanisms underlying the function of ChM-1 with a focus on HIF-2α pathway.

METHODS

Angiogenic-related markers were evaluated in OA cartilage and different stages of chondrocyte differentiation. Chondrocytes transfected with ChM-1 lentivirus or siRNA was treated with tumor necrosis factor (TNF-α) to investigate the role of ChM-1 in chondrocyte hypertrophic changes. In vivo study was conducted by using a surgical induced OA rat model with intra-articular injection of lentivirus ChM-1 (LV-ChM-1) or mock lentivirus (LV-GFP) control. Transcriptional activity of HIF-2α was determined by chromatin immunoprecipitation (ChIP) assay to unveil the mechanisms of ChM-1.

RESULTS

Majority angiogenic factors increased in severe OA cartilage, while anti-angiogenic factors including ChM-1 decreased. ChM-1 expression was strongly related with chondrocyte differentiation and chondrogenesis in vitro. ChM-1 overexpression protected chondrocytes from TNF-α induced hypertrophy, and intra-articular injection of LV-ChM-1 delayed OA progression. ChM-1 delayed HIF-2α nuclear translocation at early time-points and decreased transcriptional activity of HIF-2α on collagen type Х α1 (COL10A1), vascular endothelial growth factor A (VEGFA) and matrix metallopeptidase-13 (MMP-13).

CONCLUSIONS

ChM-1 maintains cartilage homeostasis by inhibiting HIF-2α induced catabolic activity and regulation of ChM-1 in cartilage may be a promising therapeutic strategy for OA.

Inhibition of vascular endothelial growth factor with shRNA in chondrocytes ameliorates osteoarthritis

Osteoarthritis (OA) is a chronic, incurable and destructive joint disease that is characterized by chondrocyte hypertrophy and cartilage degradation. Angiogenesis, mediated by the action of vascular endothelial growth factor (VEGF), is known to be a contributing factor in the pathogenesis of OA. In this study, we use a lentivirus-based approach to investigate whether VEGF knockdown would be beneficial to chondrogenesis and could prevent or slow down OA progression. We first profiled cytokines in human OA cartilage using cytokine antibody arrays. This revealed that as many as 21 angiogenesis-related cytokines were significantly upregulated in severe OA cartilage compared to mild OA samples. Next, we infected chondrocytes with VEGF small hairpin RNA (shRNA) lentivirus (LV-VEGF shRNA) and treated these cells with tumour necrosis factor alpha (TNF-α) to induce hypertrophy. The results showed that inhibition of VEGF not only enhanced chondrogenic differentiation, but also protected chondrocytes from TNF-α-induced hypertrophy. We also found that knockdown of VEGF suppressed TNF-α-induced phosphorylation of ERK1/2 in chondrocytes. Furthermore, using a surgically induced OA rat model, we showed that VEGF inhibition delayed OA progression in animals given intra-articular injection of LV-VEGF shRNA. In conclusion, in this study, we have shown that VEGF knockdown can enhance chondrogenesis and prevent OA progression, thus providing evidence that inhibition of VEGF may be a potential therapeutic approach for OA patients.

KEY MESSAGES

Numerous pro-angiogenic factors are upregulated in severe OA cartilage. Inhibition of VEGF by shRNA protects chondrocytes from TNF-α-induced hypertrophy. Knockdown of VEGF suppresses TNF-α-induced phosphorylation of ERK1/2 in chondrocytes. VEGF inhibition delays OA progression in rat model in vivo. Inhibition of VEGF may be a potential therapeutic approach for OA patients.

Adapted Resistance to the Knockdown Effect of shRNA-Derived Srsf3 siRNAs in Mouse Littermates

Gene silencing techniques are widely used to control gene expression and have potential for RNAi-based therapeutics. In this report, transgenic mouse lines were created for conditional knockdown of Srsf3 (SRp20) expression in liver and mammary gland tissues by expressing Srsf3-specific shRNAs driven by a U6 promoter. Although a small portion of the transgenic mouse littermates were found to produce siRNAs in the targeted tissues, most of the transgenic littermates at two months of age failed to display a knockdown phenotype of Srsf3 expression in their liver and mammary gland tissues where an abundant level of Srsf3 siRNAs remained. We saw only one of four mice with liver/mammary gland expressing Srsf3 siRNA displayed a suppressed level of Srsf3 protein, but not the mRNA. Data indicate that the host resistance to a gene-specific siRNA targeting an essential gene transcript can be developed in animals, presumably as a physiological necessity to cope with the hostile perturbation.

SAHA inhibits the transcription initiation of HPV18 E6/E7 genes in HeLa cervical cancer cells

High risk human papillomavirus (HPV) is a well recognized causative agent of cervical cancer. Suberoylanilide hydroxamic acid (SAHA) is a potential anti-cervical cancer drug; however, its effect on the expression of HPV E6 and E7 genes remains unclear. Here, we show that, in SAHA treated HeLa cells, HPV18 E6 and E7 mRNA and protein levels were reduced, HPV18 promoter activity was decreased, and the association of RNP II with HPV18 promoter was diminished, suggesting that SAHA inhibited the transcription initiation of HPV18 E6 and E7 genes. In SAHA-treated HeLa, although the level of lysine 9-acetylated histone H3 in the whole cell extracts increased obviously, its enrichment on HPV18 promoter was significantly reduced which is correlated with the down-regulation of HPV E6 and E7.

Targeted silencing of MLL5β inhibits tumor growth and promotes gamma-irradiation sensitization in HPV16/18-associated cervical cancers

We previously identified a novel MLL5 isoform, MLL5β, which was essential for E6 and E7 transcriptional activation in HPV16/18-associated cervical cancers. In this report, we investigated the potential of RNAi-mediated silencing of MLL5β through the use of MLL5β-siRNA as a novel therapeutic strategy for HPV16/18-positive cervical cancer. We observed concurrent downregulation of E6 and E7 after MLL5β silencing, leading to growth inhibition via the activation of apoptosis and senescence in the HeLa cell model. This corresponded with the enhanced antitumor effects of MLL5β-siRNA compared with E6- or E7-siRNA single treatments. Significant reduction in tumor size after MLLβ-siRNA treatment in the HeLa xenograft tumor model further emphasized the importance of MLL5β in HPV16/18-associated tumor growth and the potential of RNAi therapeutics that target MLL5β. We also identified MLL5β as a modulator of gamma-irradiation (IR) sensitization properties of cisplatin. We observed that while MLL5β silencing alone was enough to evoke cisplatin-like IR sensitization in tumor cells in vitro, overexpression of MLL5β inhibited the ability of cisplatin to sensitize HeLa cells to IR-induced cytotoxicity. MLL5β-siRNA-IR cotreatment was also observed to enhance tumor growth inhibition in vivo. Taken together, our findings highlight the potential of targeted silencing of MLL5β via the use of MLL5β-siRNA as a novel therapeutic strategy and propose that MLL5β-siRNA could be a viable alternative for cisplatin in the current cisplatin-based chemotherapeutics for HPV16/18-associated cervical cancers.