Teng Ji

Silencing of the STAT3 signaling pathway reverses the inherent and induced chemoresistance of human ovarian cancer cells.

Ovarian cancer is the leading cause of gynecologic cancer deaths among women. Although platinum-based chemotherapy is the first-line treatment for human ovarian cancer, chemoresistance remains a major obstacle to successful treatment, and there are currently no approved molecularly targeted therapies. Recent evidence indicates that signal transducer and activator of transcription-3 (STAT3) is a determinant of chemoresistance and is related to tumor recurrence in a large number of solid malignancies. In this study, we demonstrated that high levels of pSTAT3 were associated with chemoresistance in human ovarian cancer cells. Targeting STAT3 by siRNA technology markedly enhanced cisplatin-induced apoptosis in cisplatin-resistant ovarian cancer cells that expressed a high level of pSTAT3. Interleukin-6 (IL-6) could induce STAT3 activation in cisplatin-sensitive ovarian cancer cells and led to protection against cisplatin. The STAT3 siRNA treatment also blocked IL-6-induced STAT3 phosphorylation, resulting in the attenuation of the anti-apoptotic activity of IL-6. We found that the combination of cisplatin and STAT3 siRNA resulted in the collapse of the mitochondrial membrane potential, attenuated the expression of Bcl-xL and Bcl-2, and increased the release of cytochrome C and expression of Bax. Taken together, these results suggest that the pharmacological inhibition of STAT3 may be a promising therapeutic strategy for the management of chemoresistance in ovarian cancer.

TALEN-mediated targeting of HPV oncogenes ameliorates HPV-related cervical malignancy

Persistent HPV infection is recognized as the main etiologic factor for cervical cancer. HPV expresses the oncoproteins E6 and E7, both of which play key roles in maintaining viral infection and promoting carcinogenesis. While siRNA-mediated targeting of E6 and E7 transcripts temporarily induces apoptosis in HPV-positive cells, it does not eliminate viral DNA within the host genome, which can harbor escape mutants. Here, we demonstrated that specifically targeting E6 and E7 within host DNA with transcription activator-like effector nucleases (TALENs) induces apoptosis, inhibits growth, and reduces tumorigenicity in HPV-positive cell lines. TALEN treatment efficiently disrupted E6 and E7 oncogenes, leading to the restoration of host tumor suppressors p53 and retinoblastoma 1 (RB1), which are targeted by E6 and E7, respectively. In the K14-HPV16 transgenic mouse model of HPV-driven neoplasms, direct cervical application of HPV16-E7-targeted TALENs effectively mutated the E7 oncogene, reduced viral DNA load, and restored RB1 function and downstream targets transcription factor E2F1 and cycling-dependent kinase 2 (CDK2), thereby reversing the malignant phenotype. Together, the results from our study suggest that TALENs have potential as a therapeutic strategy for HPV infection and related cervical malignancy.

Cytoplasmic p21 is a potential predictor for cisplatin sensitivity in ovarian cancer

BackgroundP21(WAF1/Cip1) binds to cyclin-dependent kinase complexes and inhibits their activities. It was originally described as an inhibitor of cancer cell proliferation. However, many recent studies have shown that p21 promotes tumor progression when accumulated in the cell cytoplasm. So far, little is known about the correlation between cytoplasmic p21 and drug resistance. This study was aimed to investigate the role of p21 in the cisplatin resistance of ovarian cancer.MethodsRT-PCR, western blot and immunofluorescence were used to detect p21 expression and location in cisplatin-resistant ovarian cancer cell line C13* and its parental line OV2008. Regulation of cytoplasmic p21 was performed through transfection of p21 siRNA, Akt2 shRNA and Akt2 constitutively active vector in the two cell lines; their effects on cisplatin-induced apoptosis were evaluated by flow cytometry. Tumor tissue sections of clinical samples were analyzed by immunohistochemistry.Resultsp21 predominantly localizes to the cytoplasm in C13* compared to OV2008. Persistent exposure to low dose cisplatin in OV2008 leads to p21 translocation from nuclear to cytoplasm, while it had not impact on p21 localization in C13*. Knockdown of cytoplasmic p21 by p21 siRNA transfection in C13* notably increased cisplatin-induced apoptosis through activation of caspase 3. Inhibition of p21 translocation into the cytoplasm by transfection of Akt2 shRNA into C13* cells significantly increased cisplatin-induced apoptosis, while induction of p21 translocation into the cytoplasm by transfection of constitutively active Akt2 in OV2008 enhanced the resistance to cisplatin. Immunohistochemical analysis of clinical ovarian tumor tissues demonstrated that cytoplasmic p21 was negatively correlated with the response to cisplatin based treatment.ConclusionsCytoplasmic p21 is a novel biomarker of cisplatin resistance and it may represent a potential therapeutic target for ovarian tumors that are refractory to conventional treatment.

Abrogation of constitutive Stat3 activity circumvents cisplatin resistant ovarian cancer

The aim of the present study was to investigate the role of Stat3 in cisplatin resistant ovarian cancer. It was first demonstrated that higher activated Stat3 was detected in cisplatin-resistant ovarian cancer cell lines. To provide evidence that supported the hypothesis that phosphorylated-Stat3 expression may promote cisplatin resistance, ectopic Stat3 was expressed by IL-6 stimulation that partially abrogates Stat3, as opposed to the knock-down of Stat3 by specific siRNA that restores cisplatin sensitivity against ovarian cancer cells. This hypothesis was further confirmed by clinical tumor specimens of ovarian cancer obtained from patients with cisplatin-resistance. Based on these premises, Stattic, an effective small molecular inhibitor of Stat3, was used to inhibit Stat3 activation. The data presented here show that Stattic restored the sensitivity to cisplatin in chemoresistant ovarian cancer by significant reductions in the expression of the anti-apoptosis protein Bcl-2, Bcl-XL, Survivin protein and phosphorylated-Akt levels. Consistent with these observations, this experiment demonstrated the first evidence of Stattic circumvented cisplatin resistance of orthotopic xenograft ovarian cancer in vivo. Altogether, these findings emphasize the importance of Stat3 in cisplatin resistance in ovarian cancer and provide a further impetus to clinically evaluate biological modifiers that may circumvent cisplatin resistance in patients with chemoresistant ovarian cancer.

Mesenchymal stem cells as carriers and amplifiers in CRAd delivery to tumors

BackgroundMesenchymal stem cells (MSCs) have been considered to be the attractive vehicles for delivering therapeutic agents toward various tumor diseases. This study was to explore the distribution pattern, kinetic delivery of adenovirus, and therapeutic efficacy of the MSC loading of E1A mutant conditionally replicative adenovirus Adv-Stat3(-) which selectively replicated and expressed high levels of anti-sense Stat3 complementary DNA in breast cancer and melanoma cells.MethodsWe assessed the release ability of conditionally replicative adenovirus (CRAd) from MSC using crystal violet staining, TCID50 assay, and quantitative PCR. In vitro killing competence of MSCs carrying Adv-Stat3(-) toward breast cancer and melanoma was performed using co-culture system of transwell plates. We examined tumor tropism of MSC by Prussian blue staining and immunofluorescence. In vivo killing competence of MSCs carrying Adv-Stat3(-) toward breast tumor was analyzed by comparison of tumor volumes and survival periods.ResultsAdv-Stat3(-) amplified in MSCs and were released 4 days after infection. MSCs carrying Adv-Stat3(-) caused viral amplification, depletion of Stat3 and its downstream proteins, and led to significant apoptosis in breast cancer and melanoma cell lines. In vivo experiments confirmed the preferential localization of MSCs in the tumor periphery 24 hours after tail vein injection, and this localization was mainly detected in the tumor parenchyma after 72 hours. Intravenous injection of MSCs carrying Adv-Stat3(-) suppressed the Stat3 pathway, down-regulated Ki67 expression, and recruited CD11b-positive cells in the local tumor, inhibiting tumor growth and increasing the survival of tumor-bearing mice.ConclusionsThese results indicate that MSCs migrate to the tumor site in a time-dependent manner and could be an effective platform for the targeted delivery of CRAd and the amplification of tumor killing effects.

Zinc Finger Nucleases Targeting the Human Papillomavirus E7 Oncogene Induce E7 Disruption and a Transformed Phenotype in HPV16/18-Positive Cervical Cancer Cells

Purpose: Cervical cancer is mainly caused by infections of high-risk human papillomavirus (HR-HPV). Persistent expression of HR-HPV oncogenes E6 and E7 is implicated in malignant transformation. The aim was to provide proof-of-concept data to support use of zinc finger nucleases (ZFN) targeting HPV E7 to treat HPV-related cervical cancer. Experimental Design: We designed and constructed ZFNs that could specifically recognize and cleave HPV16/18 E7 DNA. We tested the cleavage efficiency of selected ZFN16-E7-S2 and ZFN18-E7-S2 by using single-strand annealing (SSA) assay. Cell viability and colony formation assays were used to estimate the inhibition of cell growth that received treatments of ZFNs. Gene disruption of HPV E7 and downstream genes were examined by Western blotting. Cell apoptosis assay was used to test the specificity and efficiency of induction of HPV type-specific apoptosis. We also introduced xenograft formation assays to estimate the potential of inhibition of HPV-related disease. Results: We found ZFN16-E7-S2 and ZFN18-E7-S2 disrupted HPV E7 oncogenes in HPV16/18–positive cervical cancer cells. Both ZFNs effectively led to inhibition of type-specific cervical cancer cell growth, and specifically induced apoptosis of corresponding HPV16- and HPV18-positive cervical cancer cell lines. ZFN16-E7-S2 and ZFN18-E7-S2 also repressed xenograft formation in vivo. Conclusion: ZFNs targeting HPV16/18 E7 could effectively induce disruption of E7 oncogenes and lead to type-specific and efficient growth inhibition and apoptosis of HPV-positive cells. ZFNs targeting HPV16/18 E7 oncogenes could be used as novel therapeutic agents for the treatment of HPV-related cervical cancer. Clin Cancer Res; 20(24); 6495–503. ©2014 AACR.

A Potent Oncolytic Adenovirus Selectively Blocks the STAT3 Signaling Pathway and Potentiates Cisplatin Antitumor Activity in Ovarian Cancer

Cisplatin-centered chemotherapy is the first-line treatment for human ovarian cancer. However, chemoresistance remains a major obstacle to successful treatment. Evidence has indicated that signal transducer and activator of transcription-3 (STAT3) is a determinant of chemoresistance; it was related to tumor recurrence in a large number of solid malignancies. Unfortunately, none of the compounds currently developed to block STAT3 signaling has been considered a serious clinical candidate because of toxicity or limited bioavailability. In this study, we clarified the significance of STAT3 activation in chemoresistant ovarian cancer and assessed the suitability of a novel oncolytic adenovirus (M4) designed to specifically deplete STAT3 and reverse cisplatin resistance in ovarian cancer. We showed that aberrant expression and constitutive activation of STAT3 was instrumental in cisplatin resistance in ovarian cancer cell lines and in ovarian cancer tissue samples. The M4 adenovirus could specifically deplete constitutive and inducible STAT3 and phosphorylated STAT3 proteins in ovarian cancer cells. This significantly inhibited cell survival and enhanced cisplatin-induced apoptosis. In contrast, normal human umbilical vein endothelial cells and human ovarian surface epithelial cells appeared to be unaffected by M4 treatment. Furthermore, a combined cisplatin plus M4 therapy substantially eliminated populations enriched in tumor-initiating cells. In mice, systemic intraperitoneal administration of M4 significantly potentiated the antitumor effect of cisplatin. These results suggest that M4 has great potential as a therapy against cisplatin resistance in human ovarian cancer. Thus, it warrants further clinical investigation.

A Systematic Comparison of the Anti-Tumoural Activity and Toxicity of the Three Adv-TKs

Adenovirus 5 vectors, known respectively as, the first generation, second generation and oncolytic adenovirus, have been studied extensively in preclinical and clinical trials. However, hitherto few systemic evaluations of the efficacy and toxicity of these adenoviral vectors that have reflected the vertical history of adenovirus based cancer gene therapy strategies have been undertaken. This study has chosen Adv-TK, the well-established adjuvant treatment in cancer, and compared its efficacy and safety with those of the two newly synthesized oncolytic adenovirus vectors encoding the HSV-TK gene, namely M7 and M8. The results obtained showed that systemic administration of 1×108 pfu M7 had an anti-tumour efficacy similar to that of 3×1010 pfu Adv-TK whilst M8 performed even better. Furthermore, compared to Adv-TK, M7 and M8 reduced the incidence of metastases and substantially prolonged the survival time of the mice xenografted with human orthotopic gastric carcinomas with disseminated metastasis. Even more exciting, however, were the similar toxic and immune safety results obtained from the administration of high doses of M7 or M8 in comparison with Adv-TK in immunocompetent and permissive syrian hamster. The data here exhibit a comprehensive display of the efficacy and safety of the three mutants and provide evidence for the future preclinical use of the M7 and M8 viruses.

Targeting Leptin as a Therapeutic Strategy against Ovarian Cancer Peritoneal Metastasis.

BACKGROUND/AIMS Epithelial ovarian cancer (OC) is the leading cause of death in patients with gynecologic malignancy. Malignant ascites, a shared symptom of advanced OC patients, plays an important role in the peritoneal metastasis cascade of OC. Since leptin existed in great amount in malignant ascites, we speculated that it might be involved in the modulation of tumor cells malignant behavior. METHOD Here, we demonstrated that blocking of leptin could significantly suppress ovarian malignant ascitesinduced metastatic aggravation of OC cells. Furthermore, our results suggested that leptin was highly expressed in OC and correlated with poor outcome of OC patients. Recombinant leptin notably promoted the migration, invasion and proliferation of OC cells. RESULT Mechanistically, we found that leptin induced epithelial-mesenchymal transition (EMT) program in OC cells through the activation of the PI3K/Akt/mTOR pathway. Pharmacological inhibition of the PI3K/Akt/mTOR pathway partly impaired leptin-induced malignant transformation of OC cells. More importantly, our in vivo xenograft experiment showed that blocking of leptin could dramatically inhibit OC cells peritoneal dissemination. CONCLUSION Collectively, this study emphasized the importance of leptin in OC progression and illustrated a novel mechanism that the PI3K/Akt/mTOR pathway was involved in leptin-induced EMT. Our findings provide new insights into leptin exertion on OC metastasis and identify the potential of leptin neutralizing as a novel strategy against OC peritoneal dissemination.

Correction: A Systematic Comparison of the Anti-Tumoural Activity and Toxicity of the Three Adv-TKs

The authors would like to correct Figs ​Figs55 and ​and6,6, as errors were introduced in the preparation of these figures for publication. In Fig 5, the stain for in situ Ad5/dE1A/dADP was derived from the same image as M7 and has an area of overlap. In Fig 6, the image for Kidney Adv-TK+GCV appears as a duplicate of Kidney GCV in panel E. The authors have provided corrected versions of Figs ​Figs55 and ​and66 here. Fig 5 TK protein expression and viral titres of Adv-TK, M7 and M8 in orthotopic tumours. Fig 6 Evaluation of the safety profiles of Adv-TK, M7 and M8 in immunocompetent and permissive Syrian hamsters. The authors confirm that these changes do not alter their findings. The authors have provided the underlying images for all figures in the original article as Supporting Information.