Dikla Ben-Shushan

A comparative study of folate receptor-targeted doxorubicin delivery systems: dosing regimens and therapeutic index.

Ligand-receptor mediated targeting may affect differently the performance of supramolecular drug carriers depending on the nature of the nanocarrier. In this study, we compare the selectivity, safety and activity of doxorubicin (Dox) entrapped in liposomes versus Dox conjugated to polymeric nanocarriers in the presence or absence of a folic acid (FA)-targeting ligand to cancer cells that overexpress the folate receptor (FR). Two pullulan (Pull)-based conjugates of Dox were synthesized, (FA-PEG)-Pull-(Cyst-Dox) and (NH2-PEG)-Pull-(Cyst-Dox). The other delivery systems are Dox loaded PEGylated liposomes (PLD, Doxil®) and the FR-targeted version (PLD-FA) obtained by ligand post-insertion into the commercial formulation. Both receptor-targeted drug delivery systems (DDS) were shown to interact in vitro specifically with cells via the folate ligand. Treatment of FR-overexpressing human cervical carcinoma KB tumor-bearing mice with three-weekly injections resulted in slightly enhanced anticancer activity of PLD-FA compared to PLD and no activity for both pullulan-based conjugates. When the DDS were administered intravenously every other day, the folated-Pull conjugate and the non-folated-Pull conjugate displayed similar and low antitumor activity as free Dox. At this dosing regimen, the liposome-based formulations displayed enhanced antitumor activity with an advantage to the non-folated liposome. However, both liposomal formulations suffered from toxicity that was reversible following treatment discontinuation. Using a daily dosing schedule, with higher cumulative dose, the folated-Pull conjugate strongly inhibited tumor growth while free Dox was toxic at this regimen. For polymeric constructs, increasing dose intensity and cumulative dose strongly affects the therapeutic index and reveals a major therapeutic advantage for the FR-targeted formulation. All DDS were able to abrogate doxorubicin-induced cardiotoxicity. This study constitutes the first side-by-side comparison of two receptor-targeted ligand-bearing systems, polymer therapeutics versus nanoparticulate systems, evaluated in the same mouse tumor model at several dosing regimens.

Overcoming obstacles in microRNA delivery towards improved cancer therapy

MicroRNAs (miRNAs) are small noncoding RNAs found to govern nearly every biological process. They frequently acquire a gain or a loss of function in cancer, hence playing a causative role in the development and progression of cancer. There are major obstacles on the way for the successful delivery of miRNA, which include low cellular uptake of the RNA and endosomal escape, immunogenicity, degradation in the bloodstream, and rapid renal clearance. The delivered miRNA needs to be successfully routed to the target organ, enter the cell and reach its intracellular target in an active form. Consequently, in order to exploit the promise of RNA interference, there is an urgent need for efficient methods to deliver miRNAs. These can be divided into three main categories: complexation, encapsulation, and conjugation. In this review, we will discuss the special considerations for miRNA delivery for cancer therapy, focusing on nonviral delivery systems: lipid, polymeric, and inorganic nanocarriers.

Incipient Melanoma Brain Metastases Instigate Astrogliosis and Neuroinflammation

Malignant melanoma is the deadliest of skin cancers. Melanoma frequently metastasizes to the brain, resulting in dismal survival. Nevertheless, mechanisms that govern early metastatic growth and the interactions of disseminated metastatic cells with the brain microenvironment are largely unknown. To study the hallmarks of brain metastatic niche formation, we established a transplantable model of spontaneous melanoma brain metastasis in immunocompetent mice and developed molecular tools for quantitative detection of brain micrometastases. Here we demonstrate that micrometastases are associated with instigation of astrogliosis, neuroinflammation, and hyperpermeability of the blood-brain barrier. Furthermore, we show a functional role for astrocytes in facilitating initial growth of melanoma cells. Our findings suggest that astrogliosis, physiologically instigated as a brain tissue damage response, is hijacked by tumor cells to support metastatic growth. Studying spontaneous melanoma brain metastasis in a clinically relevant setting is the key to developing therapeutic approaches that may prevent brain metastatic relapse. Cancer Res; 76(15); 4359-71. ©2016 AACR.

Amphiphilic nanocarrier-induced modulation of PLK1 and miR-34a leads to improved therapeutic response in pancreatic cancer

The heterogeneity of pancreatic ductal adenocarcinoma (PDAC) suggests that successful treatment might rely on simultaneous targeting of multiple genes, which can be achieved by RNA interference-based therapeutic strategies. Here we show a potent combination of microRNA and siRNA delivered by an efficient nanocarrier to PDAC tumors. Using proteomic-microRNA profiles and survival data of PDAC patients from TCGA, we found a novel signature for prolonged survival. Accordingly, we used a microRNA-mimic to increase miR-34a together with siRNA to silence PLK1 oncogene. For in vivo dual-targeting of this combination, we developed a biodegradable amphiphilic polyglutamate amine polymeric nanocarrier (APA). APA-miRNA–siRNA polyplexes systemically administered to orthotopically inoculated PDAC-bearing mice showed no toxicity and accumulated at the tumor, resulting in an enhanced antitumor effect due to inhibition of MYC oncogene, a common target of both miR-34a and PLK1. Taken together, our findings warrant this unique combined polyplex’s potential as a novel nanotherapeutic for PDAC.Treatment of pancreatic ductal adenocarcinoma is still challenging and patients survival has only marginally improved in the last decade. Here the authors produce a PGA-based polymeric nanocarrier for the dual delivery of miR-34a-mimic and PLK1-targeting siRNA resulting in killing of pancreatic cancer cells in vivo.

Systemic administration of radiation-potentiated anti-angiogenic gene therapy against primary and metastatic cancer based on transcriptionally controlled HSV-TK.

Transcription-targeted gene delivery directed against angiogenic endothelial cells is a new approach against advanced cancer. Moreover, the herpes simplex virus-thymidine kinase (HSV-TK) gene coupled with low dose radiotherapy is an efficient and externally controlled cytotoxic system. We have previously demonstrated enhanced endothelial-specific cell expression and killing using the modified murine pre-proendothelin-1 promoter (PPE1-3x) to direct adenoviral expression of a pro-apoptotic gene. The purpose of this study was to create an externally potentiated systemic antiangiogenic gene delivery system based on an adenoviral vector expressing HSV-TK under the regulation of PPE1-3X promoter combined with radiotherapy for eradicating metastatic cancer. Ad-PPE1-3x-TK induced endothelial-specific cell killing in-vitro upon introduction of the prodrug ganciclovir (GCV). BALB/c mice bearing a primary CT-26 colon carcinoma tumor showed tumor growth suppression and diminished tumor angiogenesis when the vector was administered intravenously, activated with GCV and potentiated with a single sub-therapeutic and non-toxic radiation dose. Moreover, intravenous administration of the vector, activated with GCV and potentiated with chest aimed radiation, to C57BL/6 mice bearing Lewis lung carcinoma metastases resulted in prolongation of mice survival. PPE1-3x-regulated HSV-TK expression was detected only in lung metastases in contrast to CMV-regulated expression. This novel system may benefit patients with metastatic disease.

Co-targeting the tumor endothelium and P-selectin-expressing glioblastoma cells leads to a remarkable therapeutic outcome

Glioblastoma is a highly aggressive brain tumor. Current standard-of-care results in a marginal therapeutic outcome, partly due to acquirement of resistance and insufficient blood-brain barrier (BBB) penetration of chemotherapeutics. To circumvent these limitations, we conjugated the chemotherapy paclitaxel (PTX) to a dendritic polyglycerol sulfate (dPGS) nanocarrier. dPGS is able to cross the BBB, bind to P/L-selectins and accumulate selectively in intracranial tumors. We show that dPGS has dual targeting properties, as we found that P-selectin is not only expressed on tumor endothelium but also on glioblastoma cells. We delivered dPGS-PTX in combination with a peptidomimetic of the anti-angiogenic protein thrombospondin-1 (TSP-1 PM). This combination resulted in a remarkable synergistic anticancer effect on intracranial human and murine glioblastoma via induction of Fas and Fas-L, with no side effects compared to free PTX or temozolomide. This study shows that our unique therapeutic approach offers a viable alternative for the treatment of glioblastoma.

Targeting NCAM-expressing neuroblastoma with polymeric precision nanomedicine

&NA; Neural cell adhesion molecule (NCAM) expression is known to be associated with an aggressive biological behavior, increased metastatic capacity and expression of stem‐cell markers in several tumor types. NCAM was also found to be expressed on tumor endothelial cells while forming new capillary‐like tubes, but not on normal endothelial cells. An NCAM‐targeted polymer‐drug conjugate can be used both to target tumors expressing high levels of NCAM as well as the angiogenic vessels and cancer stem cells populations characterized by NCAM expression within tumors. Here, we describe the design, synthesis, physico‐chemical characterization and the biological evaluation of an NCAM‐targeted conjugate of polyglutamic acid with paclitaxel that was developed and evaluated on neuroblastoma, a high NCAM‐expressing tumor. This conjugate inhibited tumor growth to a higher extent compared to the control conjugates and was less toxic than free paclitaxel. The dose of the conjugate could be increased at least twice than the maximum tolerated dose of paclitaxel to achieve better activity without aggravating toxicity. This work presents evidence that NCAM targeting can highly increase the efficacy of nanomedicines in the appropriate tumor models. Graphical abstract Figure. No caption available.

Wilms Tumor NCAM-Expressing Cancer Stem Cells as Potential Therapeutic Target for Polymeric Nanomedicine

Cancer stem cells (CSC) form a specific population within the tumor that has been shown to have self-renewal and differentiation properties, increased ability to migrate and form metastases, and increased resistance to chemotherapy. Consequently, even a small number of cells remaining after therapy can repopulate the tumor and cause recurrence of the disease. CSCs in Wilms tumor, a pediatric renal cancer, were previously shown to be characterized by neural cell adhesion molecule (NCAM) expression. Therefore, NCAM provides a specific biomarker through which the CSC population in this tumor can be targeted. We have recently developed an NCAM-targeted nanosized conjugate of paclitaxel bound to a biodegradable polyglutamic acid polymer. In this work, we examined the ability of the conjugate to inhibit Wilms tumor by targeting the NCAM-expressing CSCs. Results show that the conjugate selectively depleted the CSC population of the tumors and effectively inhibited tumor growth without causing toxicity. We propose that the NCAM-targeted conjugate could be an effective therapeutic for Wilms tumor. Mol Cancer Ther; 16(11); 2462–72. ©2017 AACR.

PO-200 Prevention of melanoma brain colonisation by inhibiting cytokines secretion from activated astrocytes

Introduction The brain microenvironment consists of various cell types such as astrocytes, microglia, neurons and brain endothelial cells. It sustains the normal brain functions and the structures of the cerebral capillaries that form the blood brain barrier (BBB). During tumour progression, malignant cells release vascular endothelial growth factor and other cytokines that increase the permeability of blood vessels allowing them to intravasate into the circulation. In addition, the cells can take advantage of the patho-physiology of the tumour angiogenenic leaky blood vessels at distant organs and extravasate from them at inflamed sites. Such activated site can be the brain parenchyma, which may become a pro-inflammatory metastatic niche. Although little is known about the precise mechanisms and the factors that contribute to the brain metastatic process, there is increasing evidence that astrocytes are involved by mediating a neuroinflammation. They respond by releasing pro-inflammatory cytokines that compromise the integrity of the BBB, increasing the permeability of the capillary endothelium and preparing a metastatic niche for melanoma colonisation. Material and methods We established three spontaneous melanoma brain metastasis mouse models that present a pro-inflammatory microenvironment and a pro-metastatic niche preceding the colonisation of melanoma to the brain. siRNA targeting specific chemokines, neutralizating antibody, or a CRISPR/Cas9 system were used to downregulate the expression and secretion of chemokines for further in vitro studies. Results and discussions We identified MCP-1, a pro-inflammatory chemokine, implicated in the paracrine interaction between melanoma cells and the brain. The positive staining for GFAP and MCP-1 in the tumour area suggests a cooperation between melanoma and the tumour microenvironment, in which MCP-1 plays a pro-tumorigenic role during cell migration. Astrocytes-secreted MCP-1 expression levels increase when co-cultured with melanoma cells or their conditioned media. Downregulation of MCP-1 leads to decreased migration of melanoma cells in vitro. Moreover, neutralising antibody-targeting MCP-1 reduces melanoma invasion in matrigel towards sprouting aortas. Conclusion Activated astrocytes promote the migration of circulating melanoma cells to the brain by increased secretion of pro-inflammatory cytokines, such as MCP-1. Consequently, investigating the changes in melanoma and astrocytes gene-expression could be the key for interfering and preventing melanoma colonisation to the brain.

Abstract C26: Melanoma brain metastasis is facilitated by instigation of reactive astrogliosis

Melanoma frequently metastasizes to the brain, resulting in dismal survival. A major obstacle for characterizing mechanisms of brain metastasis is the lack of tractable pre-clinical models that mimic the multi-stage process of brain metastasis. We established a novel model of spontaneous melanoma brain metastasis in immunocompetent mice. Aggressive local tumors are formed following orthotopic injection, and 3-4 months after surgical excision of the primary tumor, 50% of the mice develop brain macrometastases. By utilizing a unique ex-vivo modeling system, we detected brain micrometastases in 50-60% of the mice and quantified the metastatic load. Moreover, we show that the detection of melanoma transcripts in cerebrospinal fluid (CSF) is correlated with brain metastases. Interestingly, preliminary findings suggest that the melanoma-derived transcripts are found in exosomes. Astrocytes are glial cells that maintain brain homeostasis, and constitute a central part of the brain microenvironment. Reactive astrogliosis is the primary response of astrocytes to brain insult. While much data have accumulated on the contribution of astrogliosis to neurodegenerative diseases, the functional role of astrogliosis in promoting melanoma brain metastases is unknown. Utilizing our model we demonstrate early changes in the microenvironment and show that micrometastases are associated with activation of astrocytes and with hyperpermeability of the blood-brain-barrier. In-vitro, paracrine signaling by melanoma cells activated astrocytes to up-regulate a ‘wound healing program’ including Cxcl10 and Serpins. Reciprocally, astrocytes facilitated the invasion of melanoma cells and were necessary for primary outgrowth in 3D co-cultures. Finally, we show that intracranial co-injection of astrocytes with melanoma cells resulted in a 9 fold increase of tumor volume, and that the same gene-signature was up-regulated in astrocytes in-vivo. Studying spontaneous melanoma brain metastasis in a clinically relevant setting enables in-depth understating of the metastatic microenviromet which is the key to developing therapeutic approaches that may prevent brain metastatic relapse. Citation Format: Hila Schwartz, Eran Blacher, Malak Amer, Nir Livneh, Anat Klein, Dikla Ben-Shushan, Shelly Soffer, Reuven Stein, Ronit Satchi-Fainaro, Viktor Umansky, Tobias Pukrop, Neta Erez. Melanoma brain metastasis is facilitated by instigation of reactive astrogliosis. [abstract]. In: Proceedings of the AACR Special Conference: Function of Tumor Microenvironment in Cancer Progression; 2016 Jan 7–10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2016;76(15 Suppl):Abstract nr C26.