Bispecific aptamer-decorated and light-triggered nanoparticles targeting tumor and stromal cells in breast cancer derived organoids: implications for precision phototherapies

BACKGROUND

Based on the established role of cancer-stroma cross-talk in tumor growth, progression and chemoresistance, targeting interactions between tumor cells and their stroma provides new therapeutic approaches. Dual-targeted nanotherapeutics selectively acting on both tumor and stromal cells may overcome the limits of tumor cell-targeting single-ligand nanomedicine due to the complexity of the tumor microenvironment.

METHODS

Gold-core/silica-shell nanoparticles embedding a water-soluble iridium(III) complex as photosensitizer and luminescent probe (Iren-AuSiO2_COOH) were efficiently decorated with amino-terminated EGFR (CL4) and PDGFRβ (Gint4.T) aptamers (Iren-AuSiO2_Aptamer). The targeting specificity, and the synergistic photodynamic and photothermal effects of either single- and dual-aptamer-decorated nanoparticles have been assessed by confocal microscopy and cell viability assays, respectively, on different human cell types including mesenchymal subtype triple-negative breast cancer (MES-TNBC) MDA-MB-231 and BT-549 cell lines (both EGFR and PDGFRβ positive), luminal/HER2-positive breast cancer BT-474 and epidermoid carcinoma A431 cells (only EGFR positive) and adipose-derived mesenchymal stromal/stem cells (MSCs) (only PDGFRβ positive). Cells lacking expression of both receptors were used as negative controls. To take into account the tumor-stroma interplay, fluorescence imaging and cytotoxicity were evaluated in preclinical three-dimensional (3D) stroma-rich breast cancer models.

RESULTS

We show efficient capability of Iren-AuSiO2_Aptamer nanoplatforms to selectively enter into target cells, and kill them, through EGFR and/or PDGFRβ recognition. Importantly, by targeting EGFR+ tumor/PDGFRβ+ stromal cells in the entire tumor bulk, the dual-aptamer-engineered nanoparticles resulted more effective than unconjugated or single-aptamer-conjugated nanoparticles in either 3D spheroids cocultures of tumor cells and MSCs, and in breast cancer organoids derived from pathologically and molecularly well-characterized tumors.

CONCLUSIONS

Our study proposes smart, novel and safe multifunctional nanoplatforms simultaneously addressing cancer-stroma within the tumor microenvironment, which are: (i) actively delivered to the targeted cells through highly specific aptamers; (ii) localized by means of their luminescence, and (iii) activated via minimally invasive light, launching efficient tumor death, thus providing innovative precision therapeutics. Given the unique features, the proposed dual targeted nanoformulations may open a new door to precision cancer treatment.

Subtype Transdifferentiation in Human Cancer: The Power of Tissue Plasticity in Tumor Progression

The classification of tumors into subtypes, characterized by phenotypes determined by specific differentiation pathways, aids diagnosis and directs therapy towards targeted approaches. However, with the advent and explosion of next-generation sequencing, cancer phenotypes are turning out to be far more heterogenous than initially thought, and the classification is continually being updated to include more subtypes. Tumors are indeed highly dynamic, and they can evolve and undergo various changes in their characteristics during disease progression. The picture becomes even more complex when the tumor responds to a therapy. In all these cases, cancer cells acquire the ability to transdifferentiate, changing subtype, and adapt to changing microenvironments. These modifications affect the tumor's growth rate, invasiveness, response to treatment, and overall clinical behavior. Studying tumor subtype transitions is crucial for understanding tumor evolution, predicting disease outcomes, and developing personalized treatment strategies. We discuss this emerging hallmark of cancer and the molecular mechanisms involved at the crossroads between tumor cells and their microenvironment, focusing on four different human cancers in which tissue plasticity causes a subtype switch: breast cancer, prostate cancer, glioblastoma, and pancreatic adenocarcinoma.

Mechanism of Action of Lactic Acid on Histones in Cancer

Significance: Metabolic end products and intermediates can exert signaling functions as chemical sources for histone posttranslational modifications, which remodel chromatin and affect gene expression. Among them, lactic acid is responsible for histone lactylation, a recently discovered histone mark that occurs in high lactate conditions, such as those resulting from the Warburg effect in cancer cells. Recent Advances: Late-breaking studies have advanced the knowledge on the mechanisms involved in histone lactylation, requiring independent nonenzyme and enzyme-dependent reactions, which is emerging as an important hallmark of cancer cells linking metabolic changes to gene expression reprogramming. Critical Issues: In this study, we give an overview about this new epigenetic modification, focusing on its mechanism of action in tumors and tumor microenvironment. Future Directions: Further investigation on the competition mechanism between lactylation and acetylation, as well as on the mechanisms by which lactate fluctuation can control a specific gene set in a given tissue, is needed in the coming years to exploit new anticancer therapeutic approaches. Antioxid. Redox Signal. 40, 236-249.

Tissue Inhibitor of Metalloproteinases-1 Overexpression Mediates Chemoresistance in Triple-Negative Breast Cancer Cells

Triple-negative breast cancer (TNBC) is among the most aggressive breast cancer subtypes. Despite being initially responsive to chemotherapy, patients develop drug-resistant and metastatic tumors. Tissue inhibitor of metalloproteinases-1 (TIMP-1) is a secreted protein with a tumor suppressor function due to its anti-proteolytic activity. Nevertheless, evidence indicates that TIMP-1 binds to the CD63 receptor and activates noncanonical oncogenic signaling in several cancers, but its role in mediating TNBC chemoresistance is still largely unexplored. Here, we show that mesenchymal-like TNBC cells express TIMP-1, whose levels are further increased in cells generated to be resistant to cisplatin (Cis-Pt-R) and doxorubicin (Dox-R). Moreover, public dataset analyses indicate that high TIMP-1 levels are associated with a worse prognosis in TNBC subjected to chemotherapy. Knock-down of TIMP-1 in both Cis-Pt-R and Dox-R cells reverses their resistance by inhibiting AKT activation. Consistently, TNBC cells exposed to recombinant TIMP-1 or TIMP-1-enriched media from chemoresistant cells, acquire resistance to both cisplatin and doxorubicin. Importantly, released TIMP-1 reassociates with plasma membrane by binding to CD63 and, in the absence of CD63 expression, TIMP-1-mediated chemoresistance is blocked. Thus, our results identify TIMP-1 as a new biomarker of TNBC chemoresistance and lay the groundwork for evaluating whether blockade of TIMP-1 signal is a viable treatment strategy.

PATZ1 in Non-Small Cell Lung Cancer: A New Biomarker That Negatively Correlates with PD-L1 Expression and Suppresses the Malignant Phenotype

Non-small cell lung cancer (NSCLC), the leading cause of cancer death worldwide, is still an unmet medical problem due to the lack of both effective therapies against advanced stages and markers to allow a diagnosis of the disease at early stages before its progression. Immunotherapy targeting the PD-1/PD-L1 checkpoint is promising for many cancers, including NSCLC, but its success depends on the tumor expression of PD-L1. PATZ1 is an emerging cancer-related transcriptional regulator and diagnostic/prognostic biomarker in different malignant tumors, but its role in lung cancer is still obscure. Here we investigated expression and role of PATZ1 in NSCLC, in correlation with NSCLC subtypes and PD-L1 expression. A cohort of 104 NSCLCs, including lung squamous cell carcinomas (LUSCs) and adenocarcinomas (LUADs), was retrospectively analyzed by immunohistochemistry for the expression of PATZ1 and PD-L1. The results were correlated with each other and with the clinical characteristics, showing on the one hand a positive correlation between the high expression of PATZ1 and the LUSC subtype and, on the other hand, a negative correlation between PATZ1 and PD-L1, validated at the mRNA level in independent NSCLC datasets. Consistently, two NSCLC cell lines transfected with a PATZ1-overexpressing plasmid showed PD-L1 downregulation, suggesting a role for PATZ1 in the negative regulation of PD-L1. We also showed that PATZ1 overexpression inhibits NSCLC cell proliferation, migration, and invasion, and that Patz1-knockout mice develop LUAD. Overall, this suggests that PATZ1 may act as a tumor suppressor in NSCLC.

Aptamer-Based Strategies to Boost Immunotherapy in TNBC

The immune system (IS) may play a crucial role in preventing tumor development and progression, leading, over the last years, to the development of effective cancer immunotherapies. Nevertheless, immune evasion, the capability of tumors to circumvent destructive host immunity, remains one of the main obstacles to overcome for maximizing treatment success. In this context, promising strategies aimed at reshaping the tumor immune microenvironment and promoting antitumor immunity are rapidly emerging. Triple-negative breast cancer (TNBC), an aggressive breast cancer subtype with poor outcomes, is highly immunogenic, suggesting immunotherapy is a viable strategy. As evidence of this, already, two immunotherapies have recently become the standard of care for patients with PD-L1 expressing tumors, which, however, represent a low percentage of patients, making more active immunotherapeutic approaches necessary. Aptamers are short, highly structured, single-stranded oligonucleotides that bind to their protein targets at high affinity and specificity. They are used for therapeutic purposes in the same way as monoclonal antibodies; thus, various aptamer-based strategies are being actively explored to stimulate the IS’s response against cancer cells. The aim of this review is to discuss the potential of the recently reported aptamer-based approaches to boost the IS to fight TNBC.

Inhibition of Bone Marrow-Mesenchymal Stem Cell-Induced Carbonic Anhydrase IX Potentiates Chemotherapy Efficacy in Triple-Negative Breast Cancer Cells

Conventional chemotherapy represents the main systemic treatment used for triple-negative breast cancer (TNBC) patients, although many of them develop drug resistance. The hypoxic TME is the crucial driver in the onset of insensitivity to chemotherapy. In this research, we elucidated the role played by bone marrow-derived mesenchymal stem cells (BM-MSCs) in reducing cisplatin effects in TNBC. BT-549 and MDA-MB-231 cells, grown under hypoxic conditions in the presence of conditioned medium obtained from BM-MSCs (CM-MSCs), showed a strong cisplatin insensitivity and increased expression levels of carbonic anhydrase IX (CA IX). Therefore, we inhibited CM-MSC-induced CA IX by SLC-0111 to potentiate chemotherapy efficacy in TNBC cells. Our results showed that CM-MSCs under hypoxic conditions caused an increase in the ability of TNBC cells to form vascular structures, migrate and invade Matrigel. Cell treatment with cisplatin plus SLC-0111 was able to block these mechanisms, as well as the signaling pathways underlying them, such as p-AKT, p-ERK, CD44, MMP-2, vimentin, β-catenin, and N-cadherin, more effectively than treatment with single agents. In addition, a significant enhancement of apoptosis assessed by annexin V, caspase-3 expression and activity was also shown. Taken together, our results demonstrated the possibility, through CA IX inhibition, of returning TNBC cells to a more chemosensitive state.

Abstract 367: Nano-immunotherapy in TNBC: Aptamer-based nanoparticles for PD-L1 siRNA delivery to cancer cells

Triple-negative breast cancer (TNBC) is a heterogeneous and aggressive group of breast cancers. The lack of specific actionable targets makes chemotherapy the main treatment for TNBC patients. However, chemotherapy has limited success due to scarce bioavailability, severe systemic side effects and drug resistance. Polymeric nanoparticles (PNPs) may efficiently deliver in vivo therapeutics to tumors when conjugated to specific targeting agents. Potential agents for targeting tumor cells are aptamers: short, single-stranded oligonucleotides that interact at high affinity with their targets. Here, we report the characterization of new multifunctional nanovectors consisting of safe and biodegradable PNPs, highly specific TNBC aptamers as delivery agents and artificial small interfering RNA (siRNA) as drug payload, designed to suppress programmed cell death-ligand 1 (PD-L1) expression, a major feature of immune evasion in cancer cells. We efficiently entrapped siRNA-PD-L1 into PNPs. To enable active targeting, siPD-L1-PNPs were functionalized with TN145-aptamer, which we previously generated by cell-SELEX and shown to bind with nanomolar affinity to TNBC cells distinguishing them from both normal breast cells and non-TNBC breast cancer cells. TN145 aptamer actively internalizes into target cells, thus representing a good candidate to deliver a therapeutic payload. We show that the aptamer-decorated nanovectors efficiently deliver fluorescein-labeled siRNA into TNBC MDA-MB-231 and BT-549 cells, as assessed by confocal microscopy. Unconjugated nanovectors or conjugated with scrambled aptamers were used as controls. Non-TNBC BT-474 and MCF7 breast cancer cells, were used to exclude unspecific binding. Importantly, a 30-min incubation of TN145-conjugated nanovectors on target cells, at a siPD-L1 concentration of 1 nM, results in stronger PD-L1 silencing than that achieved by siPD-L1 delivered via a commercial transfection reagent. Furthermore, TN145-PNPs loaded with both siPD-L1 and cisplatin were generated and the efficacy of combined treatment was tested on tumor cells and tumor and immune cell co-cultures. Chemotherapy, including cisplatin, has been reported to induce PD-L1 enrichment in TNBC cells, hence an aptamer-targeted nanosystem enabling the synergistic effect of siRNA that directly knocks down PD-L1 expression on tumor cells with a powerful chemotherapeutic drug could be the future way to eradicate TNBC cells.

Citation Format: Lisa Agnello, Simona Camorani, Silvia Tortorella, Annachiara d’Argenio, Roberto Nilo, Monica Fedele, Antonella Zannetti, Mauro Comes Franchini, Laura Cerchia. Nano-immunotherapy in TNBC: Aptamer-based nanoparticles for PD-L1 siRNA delivery to cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 367.

Abstract 1040: Blocking hypoxia-induced carbonic anhydrases 9 enhances sensibility to cisplatin of head and neck squamous carcinoma

The head and neck squamous carcinomas (HNSSCs) are the sixth most common cancer worldwide. Given the heterogeneous nature of HNSCC, this carcinoma results in higher resistance to chemoradiotherapy. Recent evidence highlight the importance of the hypoxic microenvironment in contributing to cisplatin resistance. Therefore, the aim of this study was to investigate the role played by hypoxia-induced protein carbonic anhydrase 9 (CA9) in supporting HNSCC cisplatin resistance. Furthermore, we purpose to investigate the ability of CA9 inhibitor, SLC-0111, a small molecule already used in Phase I clinical trial, to sensitize HNSSC cells to chemotherapy in vitro and in vivo. We analyzed the expression of CA9 in a public data set of 103 HNSCC samples and 22 oral cavity normal tissues and in two HNSSC cell lines (FaDu; SCC-011). HNSCC cells grown in 2D and 3D models under hypoxic conditions (1% O2) showed increased levels of CA9 and greater resistance to cisplatin than cells grown under normoxic conditions. The addition of CA9 inhibitor SLC-0111 to cisplatin sensitized cells to the chemotherapeutic agent and caused a reduction of colony number, spheroid formation, tumor cell, and spheroid migration and invasiveness. Furthermore, the combination therapy hampered activation of STAT3, AKT, ERK, and EMT program whereas it induced apoptosis. Notably, the combined treatment caused inhibition of tumor growth and induction of apoptosis in HNSCC subcutaneous xenografts, as assessed by high-frequency ultrasonography and fluorescent molecular tomography (FMT) with NIR-Annexin V, respectively, at a higher extent than single agents. In addition, FMT with NIR-Prosense revealed a stronger reduction of lymph nodes metastases when mice bearing orthotopic xenografts were treated with cisplatin plus SLC-0111 with respect to a single treatment. Our findings taken together demonstrate the crucial role played by CA9 in promoting cisplatin resistance in HNSCC and the efficacy of SLC-0111 to sensitize tumor cells and xenografts to chemotherapy.

Citation Format: Annachiara Sarnella, Ylenia Ferrara, Luigi Auletta, Sandra Albanese, Vincenzo Alterio, Jean-Yves Winum, Claudiu T Supuran, Laura Cerchia, Giuseppina De Simone, Antonella Zannetti. Blocking hypoxia-induced carbonic anhydrases 9 enhances sensibility to cisplatin of head and neck squamous carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1040.

Inhibition of carbonic anhydrases IX/XII by SLC-0111 boosts cisplatin effects in hampering head and neck squamous carcinoma cell growth and invasion

Background

Hypoxic tumor microenvironment (TME) contributes to the onset of many aspects of the cancer biology associated to the resistance to conventional therapies. Hypoxia is a common characteristic and negative prognostic factor in the head and neck squamous carcinomas (HNSCC) and is correlated with aggressive and invasive phenotype as well as with failure to chemo- and radio-therapies. The carbonic anhydrase isoenzymes IX and XII (CA IX/XII), regulators of extra and intracellular pH, are overexpressed in TME and are involved in adaptative changes occurring in cancer cells to survive at low O₂. In this study, we aim to investigate in HNSCC cells and murine models the possibility to target CA IX/XII by the specific inhibitor SLC-0111 to potentiate the effects of cisplatin in hampering cell growth, migration and invasion. Furthermore, we analyzed the signal pathways cooperating in acquisition of a more aggressive phenotype including stemness, epithelial-mesenchymal transition and apoptotic markers.

Methods

The effects of cisplatin, CA IX/XII specific inhibitor SLC-0111, and the combinatorial treatment were tested on proliferation, migration, invasion of HNSCC cells grown in 2D and 3D models. Main signal pathways and the expression of stemness, mesenchymal and apoptotic markers were analyzed by western blotting. Molecular imaging using NIR-Annexin V and NIR-Prosense was performed in HNSCC xenografts to detect tumor growth and metastatic spread.

Results

HNSCC cells grown in 2D and 3D models under hypoxic conditions showed increased levels of CA IX/XII and greater resistance to cisplatin than cells grown under normoxic conditions. The addition of CA IX/XII inhibitor SLC-0111 to cisplatin sensitized HNSCC cells to the chemotherapeutic agent and caused a reduction of proliferation, migration and invasiveness. Furthermore, the combination therapy hampered activation of STAT3, AKT, ERK, and EMT program, whereas it induced apoptosis. In HNSCC xenografts the treatment with cisplatin plus SLC-0111 caused an inhibition of tumor growth and an induction of apoptosis as well as a reduction of metastatic spread at a higher extent than single agents.

Conclusion

Our results highlight the ability of SLC-0111 to sensitize HNSCC to cisplatin by hindering hypoxia-induced signaling network that are shared among mechanisms involved in therapy resistance and metastasis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02345-x.

Selective Photo-Assisted Eradication of Triple-Negative Breast Cancer Cells through Aptamer Decoration of Doped Conjugated Polymer Nanoparticles

Photodynamic therapy (PDT) may be an excellent alternative in the treatment of breast cancer, mainly for the most aggressive type with limited targeted therapies such as triple-negative breast cancer (TNBC). We recently generated conjugated polymer nanoparticles (CPNs) as efficient photosensitizers for the photo-eradication of different cancer cells. With the aim of improving the selectivity of PDT with CPNs, the nanoparticle surface conjugation with unique 2’-Fluoropyrimidines-RNA-aptamers that act as effective recognition elements for functional surface signatures of TNBC cells was proposed and designed. A coupling reaction with carbodiimide was used to covalently bind NH2-modified aptamers with CPNs synthetized with two polystyrene-based polymer donors of COOH groups for the amide reaction. The selectivity of recognition for TNBC membrane receptors and PDT efficacy were assayed in TNBC cells and compared with non-TNBC cells by flow cytometry and cell viability assays. Furthermore, in vitro PDT efficacy was assayed in different TNBC cells with significant improvement results using CL4, sTN29 and sTN58 aptamers compared to unconjugated CPNs and SCR non-specific aptamer. In a chemoresistance TNBC cell model, sTN58 was the candidate for improving labelling and PDT efficacy with CPNs. We proposed sTN58, sTN29 and CL4 aptamers as valuable tools for selective TNBC targeting, cell internalization and therapeutic improvements for CPNs in PDT protocols.

Synthesis and functionalization of casein nanoparticles with aptamers for triple-negative breast cancer targeting

This work shows the synthesis of a drug delivery system made of casein nanoparticles able to host hydrophobic molecules and be functionalized with aptamers targeting the epidermal growth factor receptor.

Profiling Cancer Cells by Cell-SELEX: Use of Aptamers for Discovery of Actionable Biomarkers and Therapeutic Applications Thereof

The identification of tumor cell-specific surface markers is a key step towards personalized cancer medicine, allowing early assessment and accurate diagnosis, and development of efficacious targeted therapies. Despite significant efforts, currently the spectrum of cell membrane targets associated with approved treatments is still limited, causing an inability to treat a large number of cancers. What mainly limits the number of ideal clinical biomarkers is the high complexity and heterogeneity of several human cancers and still-limited methods for molecular profiling of specific cancer types. Thanks to the simplicity, versatility and effectiveness of its application, cell-SELEX (Systematic Evolution of Ligands by Exponential Enrichment) technology is a valid complement to the present strategies for biomarkers' discovery. We and other researchers worldwide are attempting to apply cell-SELEX to the generation of oligonucleotide aptamers as tools for both identifying new cancer biomarkers and targeting them by innovative therapeutic strategies. In this review, we discuss the potential of cell-SELEX for increasing the currently limited repertoire of actionable cancer cell-surface biomarkers and focus on the use of the selected aptamers as components of innovative conjugates and nano-formulations for cancer therapy.

The IL13α 2R paves the way for anti-glioma nanotherapy

Glioblastoma (GBM) is one of the most aggressive (grade IV) gliomas characterized by a high rate of recurrence, resistance to therapy and a grim survival prognosis. The long-awaited improvement in GBM patients' survival rates essentially depends on advances in the development of new therapeutic approaches. Recent preclinical studies show that nanoscale materials could greatly contribute to the improvement of diagnosis and management of brain cancers. In the current review, we will discuss how specific features of glioma pathobiology can be employed for designing efficient targeting approaches. Moreover, we will summarize the main evidence for the potential of the IL-13R alpha 2 receptor (IL13α2R) targeting in GBM early diagnosis and experimental therapy.

Optimizing cisplatin delivery to triple-negative breast cancer through novel EGFR aptamer-conjugated polymeric nanovectors

BACKGROUND

Management of triple-negative breast cancer (TNBC) is still challenging because of its aggressive clinical behavior and limited targeted treatment options. Cisplatin represents a promising chemotherapeutic compound in neoadjuvant approaches and in the metastatic setting, but its use is limited by scarce bioavailability, severe systemic side effects and drug resistance. Novel site-directed aptamer-based nanotherapeutics have the potential to overcome obstacles of chemotherapy. In this study we investigated the tumor targeting and the anti-tumorigenic effectiveness of novel cisplatin-loaded and aptamer-decorated nanosystems in TNBC.

METHODS

Nanotechnological procedures were applied to entrap cisplatin at high efficacy into polymeric nanoparticles (PNPs) that were conjugated on their surface with the epidermal growth factor receptor (EGFR) selective and cell-internalizing CL4 aptamer to improve targeted therapy. Internalization into TNBC MDA-MB-231 and BT-549 cells of aptamer-decorated PNPs, loaded with BODIPY505-515, was monitored by confocal microscopy using EGFR-depleted cells as negative control. Tumor targeting and biodistribution was evaluated by fluorescence reflectance imaging upon intravenously injection of Cyanine7-labeled nanovectors in nude mice bearing subcutaneous MDA-MB-231 tumors. Cytotoxicity of cisplatin-loaded PNPs toward TNBC cells was evaluated by MTT assay and the antitumor effect was assessed by tumor growth experiments in vivo and ex vivo analyses.

RESULTS

We demonstrate specific, high and rapid uptake into EGFR-positive TNBC cells of CL4-conjugated fluorescent PNPs which, when loaded with cisplatin, resulted considerably more cytotoxic than the free drug and nanovectors either unconjugated or conjugated with a scrambled aptamer. Importantly, animal studies showed that the CL4-equipped PNPs achieve significantly higher tumor targeting efficiency and enhanced therapeutic effects, without any signs of systemic toxicity, compared with free cisplatin and untargeted PNPs.

CONCLUSIONS

Our study proposes novel and safe drug-loaded targeted nanosystems for EGFR-positive TNBC with excellent potential for the application in cancer diagnosis and therapy.

The Transcription Regulator Patz1 Is Essential for Neural Stem Cell Maintenance and Proliferation

Proper regulation of neurogenesis, the process by which new neurons are generated from neural stem and progenitor cells (NS/PCs), is essential for embryonic brain development and adult brain function. The transcription regulator Patz1 is ubiquitously expressed in early mouse embryos and has a key role in embryonic stem cell maintenance. At later stages, the detection of Patz1 expression mainly in the developing brain suggests a specific involvement of Patz1 in neurogenesis. To address this point, we first got insights in Patz1 expression profile in different brain territories at both embryonic and postnatal stages, evidencing a general decreasing trend with respect to time. Then, we performed in vivo and ex vivo analysis of Patz1-knockout mice, focusing on the ventricular and subventricular zone, where we confirmed Patz1 enrichment through the analysis of public RNA-seq datasets. Both embryos and adults showed a significant reduction in the number of Patz1-null NS/PCs, as well as of their self-renewal capability, compared to controls. Consistently, molecular analysis revealed the downregulation of stemness markers in NS/PCs derived from Patz1-null mice. Overall, these data demonstrate the requirement of Patz1 for NS/PC maintenance and proliferation, suggesting new roles for this key transcription factor specifically in brain development and plasticity, with possible implications for neurodegenerative disorders and glial brain tumors.

Aptamers and antibodies: rivals or allies in cancer targeted therapy?

The goal of an efficacious cancer therapy is to specifically target diseased cells at high accuracy while sparing normal, healthy cells. Over the past three decades, immunotherapy, based on the use of monoclonal antibodies (mAbs) directed against tumor-associated antigens, to inhibit their oncogenic function, or against immune checkpoints, to modulate specific T cell responses against cancer, has proven to be an important strategy for cancer therapy. Nevertheless, the number of mAbs approved for clinical use is still limited because of significant drawbacks to their applicability. Oligonucleotide aptamers, similarly to antibodies, form high-affinity bonds with their specific protein targets, thus representing an effective tool for active cancer targeting. Compared to antibodies, aptamers’ use as therapeutic agents benefits from their low size, low/no immunogenicity, simple synthesis and design flexibility for improving efficacy and stability. This review intends to highlight recently emerged applications of aptamers as recognition elements, from biomarker discovery to targeted drug delivery and targeted treatment, showing aptamers’ potential to work in conjunction with antibodies for attacking cancer from multiple flanks.

Aptamer targeted therapy potentiates immune checkpoint blockade in triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is a uniquely aggressive cancer with high rates of relapse due to resistance to chemotherapy. TNBC expresses higher levels of programmed cell death-ligand 1 (PD-L1) compared to other breast cancers, providing the rationale for the recently approved immunotherapy with anti-PD-L1 monoclonal antibodies (mAbs). A huge effort is dedicated to identify actionable biomarkers allowing for combination therapies with immune-checkpoint blockade. Platelet-derived growth factor receptor β (PDGFRβ) is highly expressed in invasive TNBC, both on tumor cells and tumor microenvironment. We recently proved that tumor growth and lung metastases are impaired in mouse models of human TNBC by a high efficacious PDGFRβ aptamer. Hence, we aimed at investigating the effectiveness of a novel combination treatment with the PDGFRβ aptamer and anti-PD-L1 mAbs in TNBC.

METHODS

The targeting ability of the anti-human PDGFRβ aptamer toward the murine receptor was verified by streptavidin-biotin assays and confocal microscopy, and its inhibitory function by transwell migration assays. The anti-proliferative effects of the PDGFRβ aptamer/anti-PD-L1 mAbs combination was assessed in human MDA-MB-231 and murine 4 T1 TNBC cells, both grown as monolayer or co-cultured with lymphocytes. Tumor cell lysis and cytokines secretion by lymphocytes were analyzed by LDH quantification and ELISA, respectively. Orthotopic 4 T1 xenografts in syngeneic mice were used for dissecting the effect of aptamer/mAb combination on tumor growth, metastasis and lymphocytes infiltration. Ex vivo analyses through immunohistochemistry, RT-qPCR and immunoblotting were performed.

RESULTS

We show that the PDGFRβ aptamer potentiates the anti-proliferative activity of anti-PD-L1 mAbs on both human and murine TNBC cells, according to its human/mouse cross-reactivity. Further, by binding to activated human and mouse lymphocytes, the aptamer enhances the anti-PD-L1 mAb-induced cytotoxicity of lymphocytes against tumor cells. Importantly, the aptamer heightens the antibody efficacy in inhibiting tumor growth and lung metastases in mice. It acts on both tumor cells, inhibiting Akt and ERK1/2 signaling pathways, and immune populations, increasing intratumoral CD8 + T cells and reducing FOXP3 + Treg cells.

CONCLUSION

Co-treatment of PDGFRβ aptamer with anti-PD-L1 mAbs is a viable strategy, thus providing for the first time an evidence of the efficacy of PDGFRβ/PD-L1 co-targeting combination therapy in TNBC.

Abstract 5088: Blocking mesenchymal stem cell-induced CAIX hampers metastatic potential and chemoresistance in TNBC

Triple negative breast cancer (TNBC) is a heterogeneous disease, and even though it occurs in only 15-20% of all patients with breast cancer, it is characterized by an extremely high rate of mortality due to metastatic and drug-resistance recurrent disease. Chemotherapy is the primary established systemic treatment for TNBC patients in both the early and advanced-stages. The lack of targeted therapies and the poor prognosis of patients with TNBC have fostered a major effort to discover actionable molecular targets to treat patients with these tumors. Many evidences highlight the crucial role played by stromal cells in the hypoxic tumor microenvironment in promoting tumor growth, metastasis and chemoresistance. In this study, we aimed to investigate tumor-educated mesenchymal stem cells (TE-MSCs) function in supporting TNBC aggressive behavior through hypoxic-induced protein carbonic anhydrase IX (CAIX). First, we analyzed CAIX expression in a public data-set of 198 TNBC samples and in two TNBC cell lines (MDA-MB-231 and BT-549). All experiments were performed by growing the TNBC cells in normoxic (21% O2) and hypoxic conditions (1% O2) in presence of TE-MSCs or their conditioned medium (CM-MSC). CAIX expression was down-regulated using a specific siRNA. Cell migration and invasion assays were carried out using Boyden chamber uncoated and coated with matrigel, respectively. TNBC cell capability to form vascular-like tubular networks and mammospheres with stemness features were analyzed growing cells on Matrigel and Vitrogel-RGD, respectively. Furthermore, the ability of a novel molecule targeting CAIX (RC44) to hamper metastatic potential of TNBC cells as well as to sensitize them to cisplatin treatment was investigated. In addition, important signaling pathways underlying these mechanisms such as epithelial-mesenchymal-transition (EMT) markers (N-cadherin, β-catenin, slug) were analyzed by western blotting. TNBC cells grown in hypoxia in presence of TE-MSCs showed an increase of HIF-1α and CAIX levels as well as a strong enhancement of their ability to migrate, invade the extracellular matrix, form vascular channels and mammospheres. Furthermore, the effect of cisplatin on cell viability was reduced when TNBC cells were grown in these conditions thus demonstrating the protective effect of TE-MSCs against anti-cancer therapy. All these events were prevented when CAIX expression was inhibited by specific siRNA or its activity blocked by RC44. Furthermore, EMT program was hampered after CAIX inhibition. In conclusion, our findings suggest that targeting CAIX it is possible to hinder some malignant features of TNBC drastically modulated by mesenchymal stem cells in hypoxic microenvironment.

Citation Format: Annachiara Sarnella, Giuliana D'Avino, Billy Hill, Vincenzo Alterio, Jean Yves Winum, Giuseppina De Simone, Laura Cerchia, Antonella Zannetti. Blocking mesenchymal stem cell-induced CAIX hampers metastatic potential and chemoresistance in TNBC [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5088.

Abstract 5256: Toward biomarkers discovery: Profiling triple-negative breast cancer cells by cell-SELEX

Triple-negative breast cancer (TNBC) is a high heterogeneous group of tumors with a distinctly aggressive nature and high rates of relapse. So far, the lack of any known targetable proteins has not allowed a specific anti-tumor treatment, thus the identification of novel agents for specific TNBC recognition and treatment is desperately needed. Nucleic acids aptamers are emerging as the most promising candidates for targeting tumor cells. They are also termed "chemical antibodies" because their form unique tertiary structures, which allow specific binding to their target molecules. Recently, by cell-SELEX integrated to advanced Next Generation Sequencing and bioinformatics, we isolated a panel of six nuclease-resistant RNA aptamers able to bind at high affinity to TNBC cells, discriminating them from both normal cells and non-TNBC breast cancer cells, and interfere with their growth as mammospheres. Also, they diversify TNBC histological specimens in a tissue microarray without recognizing samples from both ER+, PR+, HER2+ breast cancers and normal adjacent tissues. Here, short versions of the aptamers have been generated, by truncating their length from 84 nt up to nearly 30 nt, which preserve efficacious targeting and anti-tumor properties as the parental moieties. In order to identify the targets of the above aptamers, which might be important surface cancer biomarkers crucial for the malignant phenotype, different biochemical approaches are harnessed that include aptamer-mediated affinity purification coupled to Mass Spectrometry and/or antibody array for human soluble receptors. Binding analyses on recombinant proteins, cells or tissues are used to verify the putative targets. Results obtained so far indicate that the target of one of the six aptamers is a secreted protein tightly and specifically associated to TNBC cell surface and with a poor prognosis. This protein identification and the functional role of its targeting by the aptamer will be shown here in detail.

The proposed cell-targeting aptamer strategy could provide an important new avenue for selective TNBC therapy.

Citation Format: Simona Camorani, Francesco Leonetti, Francesca Collina, Monica Cantile, Gerardo Botti, Antonella Zannetti, Monica Fedele, Laura Cerchia. Toward biomarkers discovery: Profiling triple-negative breast cancer cells by cell-SELEX [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5256.

Breakthroughs in Medicinal Chemistry: New Targets and Mechanisms, New Drugs, New Hopes-7

Breakthroughs in Medicinal Chemistry [...].

Ipilimumab and Its Derived EGFR Aptamer-Based Conjugate Induce Efficient NK Cell Activation against Cancer Cells

The immune checkpoint CTLA-4 (cytotoxic T-lymphocyte-antigen 4), which inhibits the co-stimulatory CD28 signal on T cells, has been recently found expressed on other cell populations, such as tumor and natural killer (NK) cells. We tested for the first time the effects of ipilimumab, the human anti-CTLA4 mAb in clinical use, on these cells and found that it inhibits the growth of tumor cells expressing CTLA-4 also in the absence of lymphocytes, and efficiently activates NK cells, thus suggesting an important unexplored role of NK cells in ipilimumab-modulated immune responses. Interestingly, the epidermal growth factor receptor (EGFR) has been shown to play a key role in tumor cell escape from immune surveillance, and in cytotoxic T lymphocyte inhibition. Thus, we tested combinatorial treatments of ipilimumab with an anti-EGFR aptamer endowed with anti-tumor activity, and constructed for the first time a novel bispecific immunoconjugate, made up of these two compounds. The novel immunoconjugate binds to the target cells, induces the activation of lymphocytes, including NK cells, and inhibits the growth of tumor target cells more efficiently than the parental compounds, by strongly enhancing the cytotoxic activity of both human peripheral blood mononuclear cells and NK cells against tumor cells.

Breakthroughs in Medicinal Chemistry: New Targets and Mechanisms, New Drugs, New Hopes-6

Breakthroughs in Medicinal Chemistry: New Targets and Mechanisms, New Drugs, New Hopes is a series of Editorials that is published on a biannual basis by the Editorial Board of the Medicinal Chemistry section of the journal Molecules [...].

Novel Human Bispecific Aptamer-Antibody Conjugates for Efficient Cancer Cell Killing

Monoclonal antibodies have been approved by the Food and Drug Administration for the treatment of various human cancers. More recently, oligonucleotide aptamers have risen increasing attention for cancer therapy thanks to their low size (efficient tumor penetration) and lack of immunogenicity, even though the short half-life and lack of effector functions still hinder their clinical applications. Here, we demonstrate, for the first time, that two novel bispecific conjugates, consisting of an anti-epidermal growth factor receptor (EGFR) aptamer linked either with an anti-epidermal growth factor receptor 2 (ErbB2) compact antibody or with an immunomodulatory (anti-PD-L1) antibody, were easily and rapidly obtained. These novel aptamer-antibody conjugates retain the targeting ability of both the parental moieties and acquire a more potent cancer cell killing activity by combining their inhibitory properties. Furthermore, the conjugation of the anti-EGFR aptamer with the immunomodulatory antibody allowed for the efficient redirection and activation of T cells against cancer cells, thus dramatically enhancing the cytotoxicity of the two conjugated partners. We think that these bispecific antibody-aptamer conjugates could have optimal biological features for therapeutic applications, such as increased specificity for tumor cells expressing both targets and improved pharmacokinetic and pharmacodynamic properties due to the combined advantages of the aptamer and antibody.

Proneural-Mesenchymal Transition: Phenotypic Plasticity to Acquire Multitherapy Resistance in Glioblastoma

Glioblastoma (GBM) is an extremely aggressive tumor of the central nervous system, with a prognosis of 12–15 months and just 3–5% of survival over 5 years. This is mainly because most patients suffer recurrence after treatment that currently consists in maximal resection followed by radio- and chemotherapy with temozolomide. The recurrent tumor shows a more aggressive behavior due to a phenotypic shift toward the mesenchymal subtype. Proneural-mesenchymal transition (PMT) may represent for GBM the equivalent of epithelial–mesenchymal transition associated with other aggressive cancers. In this review we frame this process in the high degree of phenotypic inter- and intra-tumor heterogeneity of GBM, which exists in different subtypes, each one characterized by further phenotypic variability in its stem-cell compartment. Under the selective pressure of different treatment agents PMT is induced. The mechanisms involved, as well as the significance of such event in the acquisition of a multitherapy resistance phenotype, are taken in consideration for future perspectives in new anti-GBM therapeutic options.

Dual Oncogenic/Anti-Oncogenic Role of PATZ1 in FRTL5 Rat Thyroid Cells Transformed by the Ha-RasV12 Oncogene

PATZ1 is a transcriptional factor downregulated in thyroid cancer whose re-expression in thyroid cancer cells leads to a partial reversion of the malignant phenotype, including the capacity to proliferate, migrate, and undergo epithelial-to-mesenchymal transition. We have recently shown that PATZ1 is specifically downregulated downstream of the Ras oncogenic signaling through miR-29b, and that restoration of PATZ1 in Ha-Ras transformed FRTL5 rat thyroid cells is able to inhibit their capacities to proliferate and migrate in vitro. Here, we analyzed the impact of PATZ1 expression on the in vivo tumorigenesis of these cells. Surprisingly, FRTL5-Ras-PATZ1 cells showed enhanced tumor initiation when engrafted in nude mice, even if their tumor growth rate was reduced compared to that of FRTL5-Ras control cells. To further investigate the cause of the enhanced tumor engraftment of FRTL5-Ras-PATZ1 cells, we analyzed the stem-like potential of these cells through their capacity to grow as thyrospheres. The results showed that restoration of PATZ1 expression in these cells increases stem cell markers’ expression and self-renewal ability of the thyrospheres while limiting their growth capacity. Therefore, we suggest that PATZ1 may play a role in enhancing the stem cell potential of thyroid cancer cells, but, at the same time, it impairs the proliferation of non-stem cells.

TNBC Challenge: Oligonucleotide Aptamers for New Imaging and Therapy Modalities

Compared to other breast cancers, triple-negative breast cancer (TNBC) usually affects younger patients, is larger in size, of higher grade and is biologically more aggressive. To date, conventional cytotoxic chemotherapy remains the only available treatment for TNBC because it lacks expression of the estrogen receptor (ER), progesterone receptor (PR) and epidermal growth factor receptor 2 (HER2), and no alternative targetable molecules have been identified so far. The high biological and clinical heterogeneity adds a further challenge to TNBC management and requires the identification of new biomarkers to improve detection by imaging, thus allowing the specific treatment of each individual TNBC subtype. The Systematic Evolution of Ligands by EXponential enrichment (SELEX) technique holds great promise to the search for novel targetable biomarkers, and aptamer-based molecular approaches have the potential to overcome obstacles of current imaging and therapy modalities. In this review, we highlight recent advances in oligonucleotide aptamers used as imaging and/or therapeutic agents in TNBC, discussing the potential options to discover, image and hit new actionable targets in TNBC.

Targeted imaging and inhibition of triple-negative breast cancer metastases by a PDGFRβ aptamer

While the overall mortality for breast cancer has recently declined, management of triple-negative breast cancer (TNBC) is still challenging because of its aggressive clinical behavior and the lack of targeted therapies. Genomic profiling studies highlighted the high level of heterogeneity of this cancer, which comprises different subtypes with unique phenotypes and response to treatment. Platelet-derived growth factor receptor β (PDGFRβ) is an established mesenchymal/stem cell-specific marker in human glioblastoma and, as recently suggested, it may uniquely mark breast cancer cells with stem-like characteristics and/or that have undergone epithelial-mesenchymal transition.

Methods: Immunohistochemical analysis for PDGFRβ expression was performed on a human TNBC tissue microarray. Functional assays were conducted on mesenchymal-like TNBC cells to investigate the effect of a previously validated PDGFRβ aptamer on invasive cell growth in three-dimensional culture conditions, migration, invasion and tube formation. The aptamer was labeled with a near-infrared (NIR) dye and its binding specificity to PDGFRβ was assessed both in vitro (confocal microscopy and flow cytometry analyses) and in vivo (fluorescence molecular tomography in mice bearing TNBC xenografts). A mouse model of TNBC lung metastases formation was established and NIR-labeled PDGFRβ aptamer was used to detect lung metastases in mice untreated or intravenously injected with unlabeled aptamer.

Results: Here, we present novel data showing that tumor cell expression of PDGFRβ identifies a subgroup of mesenchymal tumors with invasive and stem-like phenotype, and propose a previously unappreciated role for PDGFRβ in driving TNBC cell invasiveness and metastases formation. We show that the PDGFRβ aptamer blocked invasive growth and migration/invasion of mesenchymal TNBC cell lines and prevented TNBC lung metastases formation. Further, upon NIR-labeling, the aptamer specifically bound to TNBC xenografts and detected lung metastases.

Conclusions: We propose PDGFRβ as a reliable biomarker of a subgroup of mesenchymal TNBCs with invasive and stem-like phenotype as well as the use of the PDGFRβ aptamer as a high efficacious tool for imaging and suppression of TNBC lung metastases. This study will allow for the significant expansion of the current repertoire of strategies for managing patients with more aggressive TNBC.

Trabectedin modulates the senescence-associated secretory phenotype and promotes cell death in senescent tumor cells by targeting NF-κB

Therapy-induced senescence is a major cellular response to chemotherapy in solid tumors. Senescent tumor cells acquire a secretory phenotype, or SASP, and produce pro-inflammatory factors, whose expression is largely under NF-κB transcriptional control. Secreted factors play a positive role in driving antitumor immunity, but also exert negative influences on the microenvironment, and promote tumor growth and metastasis. Moreover, subsets of cancer cells can escape the senescence arrest, driving tumor recurrence after treatments. Hence, removal the senescent tumor cells, or reprogramming of the senescent secretome, have become attractive therapeutic options.

The marine drug trabectedin was shown to inhibit the production of pro-inflammatory mediators by tumor-infiltrating immune cells and by myxoid liposarcoma cells. Here, we demonstrate that trabectedin inhibits the SASP, thus limiting the pro-tumoral activities of senescent tumor cells in vitro. We show that trabectedin modulates NF-κB transcriptional activity in senescent tumor cells. This results in disruption of the balance between antiapoptotic and proapoptotic signals, and sensitization of cells to Fas-mediated apoptosis. Further, we found that trabectedin inhibits escape from therapy-induced senescence, at concentrations that do not affect the viability of bulk tumor population.

Overall, our data demonstrate that trabectedin has the potential to inhibit multiple detrimental effects of therapy-induced senescence.

PATZ1 expression correlates positively with BAX and negatively with BCL6 and survival in human diffuse large B cell lymphomas

Non-Hodgkin lymphomas (NHLs) include a heterogeneous group of diseases, which differ in both cellular origin and clinical behavior. Among the aggressive malignancies of this group, the diffuse large B-cell lymphomas (DLBCLs) are the most frequently observed. They are themselves clinically and molecularly heterogeneous and have been further sub-divided in three sub-types according to different cell of origin, mechanisms of oncogenesis and clinical outcome. Among them, the germinal center B-cell-like (GCB) derives from the germinal center and expresses the BCL6 oncogene. We have previously shown that Patz1-knockout mice develop B-cell neoplasias, suggesting a tumor suppressor role for PATZ1 in human NHLs. Here, by immunohistochemical analysis of a tissue-microarray including 170 NHLs, we found that PATZ1 nuclear expression is down-regulated in follicular lymphomas and DLBCLs. Moreover, consistent with our previous results showing a PATZ1-dependent regulation of BCL6 and BAX transcription, we show that low PATZ1 nuclear expression significantly correlates with high BCL6 expression, mainly in DLBCLs, and with low BAX expression, also considering separately follicular lymphomas and DLBCLs. Finally, by analyzing overall and progression-free survival in DLBCL patients that underwent rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone chemotherapy, low levels of PATZ1 were significantly associated to a worst outcome and demonstrated an independent prognostic factor in multivariate analysis, including known prognostic factors of DLBCL, IPI score and cell of origin (GCB/non-GCB). Therefore, we propose PATZ1 as a new prognostic marker of DLBCLs, which may act as a tumor suppressor by enhancing apoptosis through inhibiting and enhancing transcription of BCL6 and BAX, respectively.

The POZ/BTB and AT-Hook Containing Zinc Finger 1 (PATZ1) Transcription Regulator: Physiological Functions and Disease Involvement

PATZ1 is a zinc finger protein, belonging to the POZ domain Krüppel-like zinc finger (POK) family of architectural transcription factors, first discovered in 2000 by three independent groups. Since that time accumulating evidences have shown its involvement in a variety of biological processes (i.e., embryogenesis, stemness, apoptosis, senescence, proliferation, T-lymphocyte differentiation) and human diseases. Here we summarize these studies with a focus on the PATZ1 emerging and controversial role in cancer, where it acts as either a tumor suppressor or an oncogene. Finally, we give some insight on clinical perspectives using PATZ1 as a prognostic marker and therapeutic target.

The Epithelial-to-Mesenchymal Transition in Breast Cancer: Focus on Basal-Like Carcinomas

Breast cancer is a heterogeneous disease that is characterized by a high grade of cell plasticity arising from the contribution of a diverse range of factors. When combined, these factors allow a cancer cell to transition from an epithelial to a mesenchymal state through a process of dedifferentiation that confers stem-like features, including chemoresistance, as well as the capacity to migrate and invade. Understanding the complex events that lead to the acquisition of a mesenchymal phenotype will therefore help to design new therapies against metastatic breast cancer. Here, we recapitulate the main endogenous molecular signals involved in this process, and their cross-talk with paracrine factors. These signals and cross-talk include the extracellular matrix; the secretome of cancer-associated fibroblasts, macrophages, cancer stem cells, and cancer cells; and exosomes with their cargo of miRNAs. Finally, we highlight some of the more promising therapeutic perspectives based on counteracting the epithelial-to-mesenchymal transition in breast cancer cells.

Inhibition of Bone Marrow-Derived Mesenchymal Stem Cells Homing Towards Triple-Negative Breast Cancer Microenvironment Using an Anti-PDGFRβ Aptamer

Bone marrow-derived mesenchymal stem cells (BM-MSCs) are shown to participate in tumor progression by establishing a favorable tumor microenvironment (TME) that promote metastasis through a cytokine networks. However, the mechanism of homing and recruitment of BM-MSCs into tumors and their potential role in malignant tissue progression is poorly understood and controversial. Here we show that BM-MSCs increase aggressiveness of triple-negative breast cancer (TNBC) cell lines evaluated as capability to migrate, invade and acquire stemness markers. Importantly, we demonstrate that the treatment of BM-MSCs with a nuclease-resistant RNA aptamer against platelet-derived growth factor receptor β (PDGFRβ) causes the inhibition of receptor-dependent signaling pathways thus drastically hampering BM-MSC recruitment towards TNBC cell lines and BM-MSCs trans-differentiation into carcinoma-associated fibroblast (CAF)-like cells. Moreover, in vivo molecular imaging analysis demonstrated the aptamer ability to prevent BM-MSCs homing to TNBC xenografts. Collectively, our results indicate the anti-PDGFRβ aptamer as a novel therapeutic tool to interfere with BM-MSCs attraction to TNBC providing the rationale to further explore the aptamer in more complex pre-clinical settings.

Aptamer Functionalization of Nanosystems for Glioblastoma Targeting through the Blood-Brain Barrier

Polymeric nanoparticles (PNPs) may efficiently deliver in vivo therapeutics to tumors when conjugated to specific targeting agents. Gint4.T aptamer specifically recognizes platelet-derived growth factor receptor β and can cross the blood-brain barrier (BBB). We synthesized Gint4.T-conjugated PNPs able of high uptake into U87MG glioblastoma (GBM) cells and with astonishing EC₅₀ value (38 pM) when loaded with a PI3K-mTOR inhibitor. We also demonstrated in vivo BBB passage and tumor accumulation in a GBM orthotopic model.

Oligonucleotide aptamers for glioma targeting: an update

Malignant glioma is the most prevalent and lethal primary brain tumor. Due to molecular heterogeneity and organ-specific clinical manifestations, it is essential to improve glioma treatment by shifting from conventional cytotoxic chemotherapy to more targeted therapies. Hence, innovative approaches based on ligands able to specifically detect and measure mutated proteins associated to a specific tumor phenotype are needed in order to refine diagnosis and therapy of glioma. To date, antibody- based approaches have been developed for in vivo applications but, in most cases, they show toxicity, do not reach adequate sensitivity and have a low permeability across the blood-brain-barrier. Single-stranded nucleic acid aptamers, generated by the SELEX (Systematic Evolution of Ligands by EXponential enrichment) process, have been shown as a valuable alternative to protein antibodies because may couple the advantages of their chemical nature to the high specific binding of antibodies to their proper targets. The simplicity of aptamers selection and derivatization with other molecules (nanocarriers, tracers for imaging, drugs) combined to low immunogenicity and toxicity, render them a versatile tool for identification of new biomarkers, in vitro diagnosis, in vivo imaging and targeted therapy. Aim of this review article is to discuss contemporary applications of aptamers as innovative tools for glioma diagnosis and therapy. We will describe promising new approaches for the identification of aptamers targeting proteins with a crucial role in glioma, including SELEX protocols against living glioma cells and brain tumor-initiating cells. Additionally, we will review recently proposed aptamer-based strategies for site-targeted controlled delivery of therapeutics and imaging agents to the brain. Summarizing, we hope that this article will provide an updated overview of perspectives and challenges for aptamer-based glioma treatment in the near future.

A novel antagonist of CXCR4 prevents bone marrow-derived mesenchymal stem cell-mediated osteosarcoma and hepatocellular carcinoma cell migration and invasion

Recent findings suggest that bone marrow-derived mesenchymal stem cells (BM-MSCs) are recruited into the microenvironment of developing tumors, where they contribute to metastatic processes. The aim of this study was to investigate the role of BM-MSCs in promoting osteosarcoma and hepatocellular carcinoma cell progression in vitro and the possible mechanisms involved in these processes. U2OS and SNU-398 are osteosarcoma and hepatocellular carcinoma cell lines, respectively, that can be induced to proliferate when cultured in the presence of BM-MSCs. To determine the effect of BM-MSCs on U2OS and SNU-398 cells, the AKT and ERK signaling pathways were investigated, and increases were observed in active P-Akt and P-Erk forms. Moreover, BM-MSCs caused an increase in tumor cell migration and invasion that was derived from the enhancement of CXCR4 levels. Thus, when tumor cells were treated with the CXCR4 antagonist AMD3100, a reduction in their migration and invasion was observed. Furthermore, a new CXCR4 inhibitor, Peptide R, which was recently developed as an anticancer agent, was used to inhibit BM-MSC-mediated tumor invasion and to overcome AMD3100 toxicity. Taken together, these results suggest that inhibiting CXCR4 impairs the cross-talk between tumor cells and BM-MSCs, resulting in reduced metastatic potential in osteosarcoma and hepatocellular carcinoma cells.

Abstract LB-022: Aptamer-mediated inhibition of EGFRvIII mutant in glioblastoma cells

High-grade glioblastoma multiforme (GBM) is the most aggressive and common of gliomas in human populations, accounting for 55% of primary brain tumors. The prognosis of GBM is very poor and most patients die of tumor recurrence.

The epidermal growth factor receptor (EGFR) and the platelet-derived growth factor receptor β (PDGFRβ) are hallmarks in GBM since they influence multiple aspects of tumor biology including cell proliferation, migration, invasiveness and resistance to treatment. In approximately half of the tumors with amplified EGFR, the EGFRvIII truncated extracellular mutant is detected. EGFRvIII does not bind ligand, is highly oncogenic and appears to be relatively resistant to treatment with conventional anti-EGFR agents such as ligand blocking monoclonal antibodies or EGFR tyrosine kinase inhibitors (TKIs). Recently, it has been demonstrated that EGFRvIII-dependent cancers may escape targeted therapy by developing dependence on PDGFRβ signaling, thus providing a strong rationale for combination therapy aimed at blocking both EGFRvIII and PDGFRβ signaling.

We have generated two nuclease resistant 2′F-Py RNA aptamers, CL4 and Gint4.T, as high affinity ligands and inhibitors of human wild-type EGFR (EGFRwt) and PDGFRβ, respectively. Thanks to their unique characteristics (low size, good target affinity, no immunogenicity, high stability) aptamers represent a new class of molecules with a great potential to rival monoclonal antibodies in both therapy and diagnosis.

Herein, by different approaches we demonstrate that CL4 aptamer binds to the EGFRvIII mutant even though it lacks amino acids 6-273 in the extracellular domain. As a consequence of binding, the aptamer inhibits EGFRvIII activation by hampering receptor homodimerization and downstream STAT3 pathway, thus confirming the critical role of EGFRvIII dimerization for signaling. Further, we show that targeting EGFRvIII by CL4, as well as by erlotinib and gefitinib, causes upregulation of PDGFRβ as a compensatory response to support cancer cell survival. Importantly, CL4 and EGFRTKIs cooperate with the anti-PDGFRβ aptamer in inhibiting survival and proliferation of EGFRvIII-overexpressing glioblastoma cells.

Given the paucity of selective inhibitors for receptor tyrosine kinases, this study could have impact in the fields of targeted molecular cancer therapeutics and may result in progress against GBM.

Citation Format: Simona Camorani, Elvira Crescenzi, David Colecchia, Andrea Carpentieri, Angela Amoresano, Mario Chiariello, Laura Cerchia. Aptamer-mediated inhibition of EGFRvIII mutant in glioblastoma cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-022. doi:10.1158/1538-7445.AM2015-LB-022

Abstract 4196: An RNA aptamer-based approach for human glioma treatment

Gliomas are the most common primary central nervous system tumors with a dismal prognosis. Despite recent advances in surgery, radiotherapy, and chemotherapy, current treatment regimens have a modest survival benefit.

Due to a combination of its complex phenotype and organ-specific clinical manifestations, efforts to refine glioma treatment with targeted therapies have largely been frustrated. Hence, finding specific ligands capable of detecting and measuring the altered pattern of gene expression and to discriminate between different tumor phenotypes, is a strategic and plausible objective for the diagnosis and therapy of glioma. To date, antibody-based approaches have been developed for in vivo applications but, in most cases, they show toxicity in vivo and do not reach adequate sensitivity. Thanks to their unique characteristics (low size, good affinity for the target, no immunogenicity, chemical structures that can be easily modified to improve their in vivo applications), single-stranded nucleic acid ligand molecules, named aptamers, represent a valid alternative to antibodies for in vivo targeted recognition as therapeutics or delivery agents for nanoparticles, small interfering RNAs, chemotherapeutic cargos and molecular imaging probes.

By applying cell-SELEX on cancer cells we have generated and characterized different nuclease resistant 2′fluoro-pyrimidines RNA aptamers as high affinity ligands and inhibitors of human receptor tyrosine kinases (RTKs) with a crucial role in glioma, including EGFR, EGFRVIII, EphB3, Axl and PDGFRβ. All the aptamers are able to efficiently and specifically inhibit tumor growth in cell based assays and in animal models of human glioma. Further, some of these aptamers strongly cooperates in inducing inhibition of tumor growth thus providing the basis for further development of antitumor combination therapies.

Citation Format: Simona Camorani, Carla L. Esposito, Silvia Catuogno, Paola Amero, Anna Rienzo, Gennaro De Vita, Gerolama Condorelli, Vittorio de Franciscis, Laura Cerchia. An RNA aptamer-based approach for human glioma treatment. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4196. doi:10.1158/1538-7445.AM2014-4196

Abstract 3053: Aptamer-mediated cancer cell-specific delivery of therapeutic microRNAs and miRNA inhibitors

The most recent advances in the field of cancer therapy have shown the great potential of using RNA-based molecules for human cancer treatment. RNA-based oligonucleotides, such as siRNA, miRNA mimic or miRNA inhibitors are being developed to modulate the expression of genes important in cancer, thus blocking tumourigenesis, inhibiting tumour growth or preventing metastasis. However a major limitation in the translation to clinic of RNA oligonucleotides is represented by the need of technologies that mediate their selective delivery improving their efficacy and safety. Conjugation with nucleic acid aptamers represents an innovative and promising approach to overcome this obstacle. Aptamers are single-stranded oligonucleotides that have been shown as high-affinity ligands and potential antagonists of cancer-associated proteins. They discriminate between closely related targets and are characterized by high specificity and low toxicity thus revealing as compounds of choice for in vivo cell recognition as delivery agents for various secondary reagents such as nanoparticles, siRNA bioconjugates, chemotherapeutic cargoes and molecular imaging probes. We have recently generated and characterized two 2’fluoro-pyrimidines containing RNA aptamers, named GL21.T and Gint4, that bind at high affinity and high specificity to human Axl tyrosine kinase receptor and PDGFRβ, respectively. These aptamers not only bind to their proper RTK but are also rapidly internalized into target cell, getting about 30% of cell internalization following 15 min-incubation and reached about 60% following 2h of aptamer treatment. By using different approaches, we have generated several completely RNA-based chimeric molecules containing internalizing aptamers coupled to therapeutic miRNAs that are down-regulated in human tumors and whose expression results in selective tumour growth inhibition. We have shown that when applied to cells expressing the specific aptamer target, the chimeric molecules are internalized and processed by Dicer, thus increasing miRNA cellular level and inhibiting miRNA target protein. As a consequence, the depletion of the targeted protein leads to miRNA herapeutic effect. Remarkably, no binding or functionality of the chimeras has been detected in cells that do not express aptamer target receptor. In addition, since miRNAs are frequently up-regulated in different alignancies, acting as oncogenes, we have developed different pproaches to conjugate internalizing aptamers to therapeutic miRNA inhibitors. The ability of these molecules to bind to and internalize in aptamer target-positive cells has been verified. The characterization in vitro and in vivo of the different chimeras is ongoing in our laboratory revealing these hybrid compounds as potential tools for innovative anti-cancer targeted therapeutics.

Citation Format: Carla L. Esposito, Silvia Catuogno, Simona Camorani, Antonella di Costanzo, Margherita Iaboni, Gerolama Condorelli, Laura Cerchia, Vittorio de Franciscis. Aptamer-mediated cancer cell-specific delivery of therapeutic microRNAs and miRNA inhibitors. [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 3053. doi:10.1158/1538-7445.AM2013-3053

The isolectin IB4 binds RET receptor tyrosine kinase in microglia

Ret receptor tyrosine kinase is the signaling component of the receptor complex for the family ligands of the glial cell line-derived neurotrophic factor (GDNF). Ret is involved in the development of enteric nervous system, of sympathetic, parasympathetic, motor and sensory neurons, and it is necessary for the post-natal maintenance of dopaminergic neurons. Ret expression has been as well demonstrated on microglia and several evidence indicate that GDNF regulates not only neuronal survival and maturation but also certain functions of microglia in the brain. Here, we demonstrated that the plant lectin Griffonia (Bandeiraea) simplicifolia lectin I, isolectin B4 (IB4), commonly used as a microglial marker in the brain, binds to the glycosylated extracellular domain of Ret on the surface of living NIH3T3 fibroblasts cells stably transfected with Ret as well as in adult rat brain as revealed by immunoblotting. Furthermore, confocal immunofluorescence analysis demonstrated a clear overlap in staining between pRet and IB4 in primary microglia cultures as well as in adult rat sections obtained from control or post-ischemic brain after permanent middle artery occlusion (pMCAO). Interestingly, IB4 staining identified activated or ameboid Ret-expressing microglia under ischemic conditions. Collectively, our data indicate Ret receptor as one of the IB4-reactive glycoconjugate accounting for the IB4 stain in microglia under physiological and ischemic conditions.

Electrochemical detection of miRNA-222 by use of a magnetic bead-based bioassay

MicroRNAs (miRNAs, miRs) are naturally occurring small RNAs (approximately 22 nucleotides in length) that have critical functions in a variety of biological processes, including tumorigenesis. They are an important target for detection technology for future medical diagnostics. In this paper we report an electrochemical method for miRNA detection based on paramagnetic beads and enzyme amplification. In particular, miR 222 was chosen as model sequence, because of its involvement in brain, lung, and liver cancers. The proposed bioassay is based on biotinylated DNA capture probes immobilized on streptavidin-coated paramagnetic beads. Total RNA was extracted from the cell sample, enriched for small RNA, biotinylated, and then hybridized with the capture probe on the beads. The beads were then incubated with streptavidin-alkaline phosphatase and exposed to the appropriate enzymatic substrate. The product of the enzymatic reaction was electrochemically monitored. The assay was finally tested with a compact microfluidic device which enables multiplexed analysis of eight different samples with a detection limit of 7 pmol L(-1) and RSD = 15 %. RNA samples from non-small-cell lung cancer and glioblastoma cell lines were also analyzed.

Abstract 192: MiR-34c has an anti-apoptotic role in non-small-cell lung carcinoma

MicroRNAs (miRNAs) constitute a class of small non-coding RNAs that negatively regulate the expression of their target genes. They are involved in many biological processes, including cell proliferation, apoptosis and differentiation, and are considered as promising new therapeutic targets for cancer. However, the identity of miRNAs involved in apoptosis and their respective targets remain largely unknown. Given the elevated complexity of miRNA regulation of gene expression, we performed a functional screening as an alternative strategy to identify those miRNAs that in lung cancer cells may interfere with the apoptotic process. To this aim we generated a derivative of the non-small cell lung carcinoma A549 cell line in which caspase-8, a critical upstream initiator of apoptosis, can be activated by the administration of the small dimerizer drug AP20187. We found a number of miRNAs that may rescue cell viability from caspase-8 activation. They included miRNAs already described as oncogenic such as miR-17, miR-135, miR-520, but also some miRNAs such as miR-124a and miR-34c for which a tumor suppressive role has been instead described or expected. Among them, miR-34c-5p markedly increased resistance to paclitaxel induced apoptosis. We demonstrate that Bmf (Bcl-2 modifying factor) is a target of miR-34c-5p and that its silencing, together with that of c-myc, a known target of miR-34c-5p, contributes to resistance to apoptosis induced by paclitaxel via p53 downregulation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 192. doi:1538-7445.AM2012-192

Abstract 883: Cell-based selection of RNA-aptamers to specifically target glioblastoma cancer stem cells

Stem cells are a group of cells, which have two important fundamental properties: self-renewal and multipotency. Stem cells have been identified also in many human cancers on the basis of being both morphologically and functionally distinct from other cells within the heterogeneous tumor mass. According to “cancer stem cell hypothesis,” the cancer stem cells (CSC) would remain unaffected by conventional therapies, and capable of repopulating the tumor and giving rise to cancer recurrence. The possibility to identify highly selective biomarkers on CSC would greatly improve cancer diagnosis and treatment. Recently, nucleic acid-based aptamers have proven useful as reagents for identifying cell surface proteins and for cell typing. Further, their high specificity and low toxicity render them a valid alternative to antibodies for in vivo cell recognition. We have developed the SELEX technology on intact glioblastoma cancer stem cells to generate aptamers as biologically active high affinity ligands for CSC-specific cell surface proteins. The approach has been applied by utilizing glioblastoma differentiated tumor cells as a negative selection, and cancer stem cells obtained from two different patients, as positive selection. Upon 16 cycles of SELEX, we generated a set of 2′-fluoro-pyrimidines containing RNA aptamers that, based on sequence analysis, have been grouped into 5 main families. Best aptamers have been then selected by binding experiments for their ability to distinguish glioblastoma CSC from differentiated tumor cells. We thus determined the binding affinity of each molecule to the cell surface specific targets. Functional experiments will be as well presented to further insight the biological role of the most promising aptamer molecules in the acquisition and maintenance of stem cells properties of glioma cancer cells. Results demonstrate the possibility to generate RNA-based aptamers as potential innovative tools for the selective targeting of cancer stem cells. A proteomic approach will define the specific membrane targets of the selected aptamers

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 883. doi:1538-7445.AM2012-883

miR-34c may protect lung cancer cells from paclitaxel-induced apoptosis

MicroRNAs (miRNAs) constitute a class of small non-coding RNAs that negatively regulate the expression of their target genes. They are involved in many biological processes, including cell proliferation, apoptosis and differentiation, and are considered as promising new therapeutic targets for cancer. However, the identity of miRNAs involved in apoptosis and their respective targets remain largely unknown. Given the elevated complexity of miRNA regulation of gene expression, we performed a functional screening as an alternative strategy to identify those miRNAs that in lung cancer cells may interfere with the apoptotic process. To this aim, we generated a derivative of the non-small cell lung carcinoma A549 cell line in which caspase-8, a critical upstream initiator of apoptosis, can be activated by administration of the small dimerizer drug AP20187. We found a number of miRNAs that may rescue cell viability from caspase-8 activation. They included miRNAs already described as oncogenic such as miR-17, miR-135 and miR-520, but also some miRNAs such as miR-124-1 and miR-34c for which a tumor-suppressive role has instead been described or expected. Among them, miR-34c-5p markedly increased resistance to paclitaxel-induced apoptosis. We demonstrate that Bmf (Bcl-2-modifying factor) is a target of miR-34c-5p, and that its silencing, together with that of c-myc, a known target of miR-34c-5p, contributes to resistance to apoptosis induced by paclitaxel through p53 downregulation.

Nucleic acid aptamers against protein kinases

Deregulation of kinase function has been implicated in several important diseases, including cancer, neurological and metabolic disorders. Because of their key role in causing disease, kinases have become one of the most intensively pursued classes of drug targets. To date, several monoclonal antibodies (mAbs) and small-molecule inhibitors have been approved for the treatment of cancer. Aptamers are short structured single stranded RNA or DNA ligands that bind at high affinity to their target molecules and are now emerging as promising molecules to target specific cancer epitopes in clinical diagnosis and therapy. Further, because of their high specificity and low toxicity aptamers will likely reveal among the most promising molecules for in vivo targeted recognition as therapeutics or delivery agents for nanoparticles, small interfering RNAs bioconjugates, chemotherapeutic cargos and molecular imaging probes. In this article, we discuss recent advances in the development of aptamers targeting kinase proteins.