Cai M. Roberts

Mesoporous silica nanoparticle delivery of chemically modified siRNA against TWIST1 leads to reduced tumor burden

UNLABELLED Growth and progression of solid tumors depend on the integration of multiple pro-growth and survival signals, including the induction of angiogenesis. TWIST1 is a transcription factor whose reactivation in tumors leads to epithelial to mesenchymal transition (EMT), including increased cancer cell stemness, survival, and invasiveness. Additionally, TWIST1 drives angiogenesis via activation of IL-8 and CCL2, independent of VEGF signaling. In this work, results suggest that chemically modified siRNA against TWIST1 reverses EMT both in vitro and in vivo. siRNA delivery with a polyethyleneimine-coated mesoporous silica nanoparticle (MSN) led to reduction of TWIST1 target genes and migratory potential in vitro. In mice bearing xenograft tumors, weekly intravenous injections of the siRNA-nanoparticle complexes resulted in decreased tumor burden together with a loss of CCL2 suggesting a possible anti-angiogenic response. Therapeutic use of TWIST1 siRNA delivered via MSNs has the potential to inhibit tumor growth and progression in many solid tumor types. FROM THE CLINICAL EDITOR Tumor progression and metastasis eventually lead to patient mortality in the clinical setting. In other studies, it has been found that TWIST1, a transcription factor, if reactivated in tumors, would lead to downstream events including angiogenesis and result in poor prognosis in cancer patients. In this article, the authors were able to show that when siRNA against TWIST1 was delivered via mesoporous silica nanoparticle, there was tumor reduction in an in-vivo model. The results have opened up a new avenue for further research in this field.

RNA-Based TWIST1 Inhibition via Dendrimer Complex to Reduce Breast Cancer Cell Metastasis

Breast cancer is the leading cause of cancer-related deaths among women in the United States, and survival rates are lower for patients with metastases and/or triple-negative breast cancer (TNBC; ER, PR, and Her2 negative). Understanding the mechanisms of cancer metastasis is therefore crucial to identify new therapeutic targets and develop novel treatments to improve patient outcomes. A potential target is the TWIST1 transcription factor, which is often overexpressed in aggressive breast cancers and is a master regulator of cellular migration through epithelial-mesenchymal transition (EMT). Here, we demonstrate an siRNA-based TWIST1 silencing approach with delivery using a modified poly(amidoamine) (PAMAM) dendrimer. Our results demonstrate that SUM1315 TNBC cells efficiently take up PAMAM-siRNA complexes, leading to significant knockdown of TWIST1 and EMT-related target genes. Knockdown lasts up to one week after transfection and leads to a reduction in migration and invasion, as determined by wound healing and transwell assays. Furthermore, we demonstrate that PAMAM dendrimers can deliver siRNA to xenograft orthotopic tumors and siRNA remains in the tumor for at least four hours after treatment. These results suggest that further development of dendrimer-based delivery of siRNA for TWIST1 silencing may lead to a valuable adjunctive therapy for patients with TNBC.

Nanoparticle delivery of siRNA against TWIST to reduce drug resistance and tumor growth in ovarian cancer models

Epithelial ovarian cancer (EOC) is the most deadly gynecologic malignancy on account of its late stage at diagnosis and frequency of drug resistant recurrences. Novel therapies to overcome these barriers are urgently needed. TWIST is a developmental transcription factor reactivated in cancers and linked to angiogenesis, metastasis, cancer stem cell phenotype, and drug resistance, making it a promising therapeutic target. In this work, we demonstrate the efficacy of TWIST siRNA (siTWIST) and two nanoparticle delivery platforms to reverse chemoresistance in EOC models. Polyamidoamine dendrimers and mesoporous silica nanoparticles (MSNs) carried siTWIST into target cells and led to sustained TWIST knockdown in vitro. Mice treated with cisplatin plus MSN-siTWIST exhibited lower tumor burden than mice treated with cisplatin alone, with most of the effect coming from reduction in disseminated tumors. This platform has potential application for overcoming the clinical challenges of metastasis and chemoresistance in EOC and other TWIST overexpressing cancers.

TWIST1 drives cisplatin resistance and cell survival in an ovarian cancer model, via upregulation of GAS6, L1CAM, and Akt signalling

Epithelial ovarian cancer (EOC) is the most deadly gynaecologic malignancy due to late onset of symptoms and propensity towards drug resistance. Epithelial-mesenchymal transition (EMT) has been linked to the development of chemoresistance in other cancers, yet little is known regarding its role in EOC. In this study, we sought to determine the role of the transcription factor TWIST1, a master regulator of EMT, on cisplatin resistance in an EOC model. We created two Ovcar8-derived cell lines that differed only in their TWIST1 expression. TWIST1 expression led to increased tumour engraftment in mice, as well as cisplatin resistance in vitro. RNA sequencing analysis revealed that TWIST1 expression resulted in upregulation of GAS6 and L1CAM and downregulation of HMGA2. Knockdown studies of these genes demonstrated that loss of GAS6 or L1CAM sensitized cells to cisplatin, but that loss of HMGA2 did not give rise to chemoresistance. TWIST1, in part via GAS6 and L1CAM, led to higher expression and activation of Akt upon cisplatin treatment, and inhibition of Akt activation sensitized cells to cisplatin. These results suggest TWIST1- and EMT-driven increase in Akt activation, and thus tumour cell proliferation, as a potential mechanism of drug resistance in EOC.

Rad59 regulates association of Rad52 with DNA double-strand breaks

Homologous recombination among repetitive sequences is an important mode of DNA repair in eukaryotes following acute radiation exposure. We have developed an assay in Saccharomyces cerevisiae that models how multiple DNA double‐strand breaks form chromosomal translocations by a nonconservative homologous recombination mechanism, single‐strand annealing, and identified the Rad52 paralog, Rad59, as an important factor. We show through genetic and molecular analyses that Rad59 possesses distinct Rad52‐dependent and ‐independent functions, and that Rad59 plays a critical role in the localization of Rad52 to double‐strand breaks. Our analysis further suggests that Rad52 and Rad59 act in multiple, sequential processes that determine genome structure following acute exposure to DNA damaging agents.

Disruption of TWIST1-RELA binding by mutation and competitive inhibition to validate the TWIST1 WR domain as a therapeutic target

BackgroundMost cancer deaths result from tumor cells that have metastasized beyond their tissue of origin, or have developed drug resistance. Across many cancer types, patients with advanced stage disease would benefit from a novel therapy preventing or reversing these changes. To this end, we have investigated the unique WR domain of the transcription factor TWIST1, which has been shown to play a role in driving metastasis and drug resistance.MethodsIn this study, we identified evolutionarily well-conserved residues within the TWIST1 WR domain and used alanine substitution to determine their role in WR domain-mediated protein binding. Co-immunoprecipitation was used to assay binding affinity between TWIST1 and the NFκB subunit p65 (RELA). Biological activity of this complex was assayed using a dual luciferase assay system in which firefly luciferase was driven by the interleukin-8 (IL-8) promoter, which is upregulated by the TWIST1-RELA complex. Finally, in order to inhibit the TWIST1-RELA interaction, we created a fusion protein comprising GFP and the WR domain. Cell fractionation and proteasome inhibition experiments were utilized to elucidate the mechanism of action of the GFP-WR fusion.ResultsWe found that the central residues of the WR domain (W190, R191, E193) were important for TWIST1 binding to RELA, and for increased activation of the IL-8 promoter. We also found that the C-terminal 245 residues of RELA are important for TWIST1 binding and IL-8 promoter activation. Finally, we found the GFP-WR fusion protein antagonized TWIST1-RELA binding and downstream signaling. Co-expression of GFP-WR with TWIST1 and RELA led to proteasomal degradation of TWIST1, which could be inhibited by MG132 treatment.ConclusionsThese data provide evidence that mutation or inhibition of the WR domain reduces TWIST1 activity, and may represent a potential therapeutic modality.

Pterostilbene, a natural phenolic compound, synergizes the antineoplastic effects of megestrol acetate in endometrial cancer

Endometrial cancer is the most common gynecologic cancer in the United States and its incidence and mortality has been rising over the past decade. Few treatment options are available for patients with advanced and recurring endometrial cancers. Novel therapies, which are frequently toxic, are difficult to establish in this patient population which tends to be older and plagued by comorbidities such as diabetes mellitus and hypertension. Therefore, novel, non-toxic therapies are urgently needed. Megestrol acetate is a frequently used drug in endometrial cancer patients. However, its response rate is only 20–30%. To enhance the activity of megestrol acetate in endometrial cancer patients, we explored the potential of combining natural supplements with megestrol acetate and found that the addition of the natural phenolic compound, pterostilbene, to megestrol acetate resulted in a synergistic inhibition of cancer cell growth in vitro and an enhanced reduction of tumor growth in a xenograft mouse model. In addition, dual treatment led to attenuation of signaling pathways, as well as cell cycle and survival pathways. Our results demonstrated for the first time that the anti-tumor activity of megestrol acetate can be enhanced by combining with pterostilbene, providing an insight into the potential application of pterostilbene and megestrol acetate combination for the treatment of endometrial cancer.

Pterostilbene Suppresses Ovarian Cancer Growth via Induction of Apoptosis and Blockade of Cell Cycle Progression Involving Inhibition of the STAT3 Pathway

A growing body of evidence has demonstrated the promising anti-tumor effects of resveratrol in ovarian cancer cells, including its inhibitory effects on STAT3 activation. Nonetheless, the low bioavailability of resveratrol has reduced its attractiveness as a potential anti-cancer treatment. In contrast, pterostilbene, a stilbenoid and resveratrol analog, has demonstrated superior bioavailability, while possessing significant antitumor activity in multiple solid tumors. In this study, the therapeutic potential of pterostilbene was evaluated in ovarian cancer cells. Pterostilbene reduces cell viability in several different ovarian cancer cell lines by suppressing cell cycle progression and inducing apoptosis. Further molecular study has shown that pterostilbene effectively suppressed phosphorylation of STAT3, as well as STAT3 downstream genes that regulate cell cycle and apoptosis, indicating that inhibition of STAT3 pathway may be involved in its anti-tumor activity. The addition of pterostilbene to the commonly used chemotherapy cisplatin demonstrated synergistic antiproliferative activity in several ovarian cancer cell lines. Pterostilbene additionally inhibited cell migration in multiple ovarian cancer cell lines. The above results suggest that pterostilbene facilitates significant anti-tumor activity in ovarian cancer via anti-proliferative and pro-apoptotic mechanisms, possibly via downregulation of JAK/STAT3 pathway. Pterostilbene thus presents as an attractive non-toxic alternative for potential adjuvant or maintenance chemotherapy in ovarian cancer.

Abstract P2-07-04: Treatment of metastatic breast cancer using two nanoparticles combined with siRNA targeting Twist1 to inhibit EMT

Breast cancer is the 2nd leading cause of cancer related deaths among women in the US with over 240,000 diagnoses and 40,000 deaths expected in 2014. Among the more serious and deadly forms of breast cancer are the Triple Negative Breast Cancers (TNBC) (ER-, PR-, HER2-). Mortality rates among patients rise dramatically when these cancers spread beyond the primary tumor site. Therefore reduction of tumor cell dispersion is a key component to minimizing mortality rates. Epithelial-Mesenchymal Transition (EMT) is the process by which cancer cells downregulate proteins associated with cell to cell adhesion (e.g. E-cadherin) resulting in cells that are able to detach from neighboring cancer cells, invade adjacent tissue, and eventually enter the circulatory system or lymphatics. The process of EMT is tightly regulated by the transcription factor Twist1, which is often overexpressed in breast cancer. Therefore, Twist1 serves as an excellent therapeutic target whose downregulation would result in fewer metastatic cancer cells and correspondingly reduce cancer mortality. Our lab has designed and tested (in vitro) two siRNA based therapeutics that target Twist1 in a TNBC cell line (SUM 1315). These siRNA molecules have been strategically designed and modified to make them resistant to degradation, enhance silencing effects and diminish their immunogenicity. To overcome the inherent problems with delivery of siRNA (both in vitro and in vivo) we have been testing two nanoparticle delivery systems. Recent advances in nanotechnology have led to the development of a variety of nanoparticles that provide valuable tools for cancer therapy. We are testing two different types of nanoparticles in this study: The first is a Polyamidoamine (PAMAM) dendrimer (YTZ3-15) which is a truncated 3rd generation dendrimer which has been modified with a lipophilic tail to enhance cellular uptake. The second is a mesoporous silica nanoparticle (MSNs) which is able to not only deliver siRNA, but is also contains pores which allow simultaneously delivering chemotherapies such as doxorubicin. This novel siRNA gene silencing and nanotechnology-based therapy should allow us to exert more precise temporal control during breast cancer treatment. When complexed with either nanoparticle we have found significant Twist1 knock down in vitro as well as reduction of Twist1 target genes that are associated with EMT. We have also shown that Twist1 silencing reduces migration and invasion of SUM 1315 breast cancer cells in vitro Recently we began testing these siRNA+Nanoparticle complexes in an orthotopic murine model using Firefly Luciferase expressing SUM 1315 cells in immunocompromised mice (NSG). The results of this in vivo research have shown that there is significant uptake of the siRNA+Nanoparticle complexes in the tumors when compared to other organs. Results of these studies are significant because TNBC is particularly drug resistant and metastatic; and superior therapies are urgently needed to effectively treat patients with these breast cancers. This approach paves the way for TNBC treatment that incorporates Twist1 knock down (resulting in renewed chemosensitivity) and simultaneous delivery of a chemotherapy reagent. Citation Format: James B Finlay, Cai M Roberts, Gina Lowe, Ling Peng, Jeff I Zink, Fuyuhiko Tamanoi, Carlotta A Glackin. Treatment of metastatic breast cancer using two nanoparticles combined with siRNA targeting Twist1 to inhibit EMT [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-07-04.

Abstract 2692: Dendrimer delivery of RNA based Twist1 inhibitors to reduce breast cancer cell metastasis.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Breast cancer in women is a leading cause of cancer related deaths in the United States with metastatic disease being the chief cause of mortality. Metastatic breast cancer tumors are often found in their later stages making them difficult to remove or treat. Inhibition of tumor cell dispersion is therefore a key component to a reduction in mortality rates among women with breast cancer. Epithelial-Mesenchymal Transition (EMT) is the process by which cancer cells downregulate proteins associated with cell to cell adhesion (e.g. E-cadherin) resulting in cells that are able to mobilize. Breast cancer cells are known to commandeer the EMT process through overexpression of Twist1, thus allowing the cells to metastasize beyond the primary tumor. Twist1 therefore serves as an excellent therapeutic target whose disruption would result in fewer metastatic cancer cells and correspondingly reduce cancer mortality. Twist1 is also a desirable target because it is almost nonexistent in adult tissues and thus its silencing would have minimal side effects. Our lab has elected to use an siRNA mediated gene silencing approach to decrease the expression levels of Twist1 in two highly invasive breast cancer cell lines (SUM 1315 and MCF7-Tw). Due to their fragile nature, siRNA molecules are often difficult to deliver at therapeutic levels. We have overcome these delivery limitations through the optimization and use of Poly (amidoamine) (PAMAM) dendrimers. We hypothesize that suppression of the activity of Twist1 via dendrimer-delivered Twist1 siRNA will inhibit metastatic behavior of aggressive breast cancer cells. Here we demonstrate successful delivery of Cy3-labled siRNA using two different dendrimers (Generation 5 and a modified Generation 3) with transfection efficiency results exceeding those of Lipofectamine 2000 and with far less toxicity to cells. We also show up to a 90% reduction (lasting at least 4 days) in Twist1 expression using Western Blot and qPCR analysis. Phenotypically we were able to appreciate a significant decrease in the invasive nature of the breast cancer cells using migration/invasion assays. Taken together these results demonstrate successful knockdown of Twist1 using siRNA dendrimer complexes resulting in an altered cellular phenotype. These data will serve as a foundation for optimization of future in vivo experiments with both orthotopic and metastatic breast cancer models. Citation Format: James B. Finlay, Cai M. Roberts, Carlotta A. Glackin. Dendrimer delivery of RNA based Twist1 inhibitors to reduce breast cancer cell metastasis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2692. doi:10.1158/1538-7445.AM2013-2692