Abstract LB-072: Activating and expanding NK cells using dissolvable alginate particles functionalized with αNKp46 and αCD2

Introduction: Generating clinical scale doses of natural killer (NK) cells is currently a challenge for manufacturing CAR-NK cell therapies. Current methods to expand NK cells include irradiated feeder cells that have been engineered to mimic dendritic cells as well as commercially available combinations of antibody & proteins for targeted NK cell expansion. These methods are restrictive due to high costs, scale-up challenges, and licensing restrictions for clinical & commercial applications. We hypothesized that using a dissolvable phase-change hydrogel conjugated with ligands targeting NK cell activation may provide a more efficient and defined alternative for NK manufacturing processes. Additionally, we investigated cytokine culture combinations that optimize the expansion of NK cells.

Methods: Hydrogel microspheres (9 µm median diameter) - referred to as Cloudz™ particles - were functionalized with αNKp46 and αCD2 ligands using standard bioconjugation techniques. In this study, human peripheral blood mononuclear cells (PBMCs) were cultured for 7 days in G-Rex® 24-well plates containing NK cell-functionalized Cloudz™ particles along with various cytokine combinations. Prior to expansion, PBMCs were analyzed for CD3-/CD56+ NK cells and 6x105 NK cells were seeded into each well with a 2:1 ratio of Cloudz™ particles:NK cells. Miltenyi MACS iBeads were used as a control and were prepared according to the manufacturer instructions. During days 0-3, the cells were cultured with IL-2 (40 U/mL) along with combinations of IL-12, IL-18, and IL-21 (10 ng/mL each). After 3 days, the IL-2 concentration was increased to 200 U/mL, while the other cytokine concentrations remained constant. The cytokines and media were refreshed every 3 days with ½ media changes. After 7 days in culture the cells were analyzed by flow cytometry for CD3-/CD56+ NK cell expansion and purity. NK cell purity was defined as the percentage of CD3-CD56+ cells relative to the total population.

Results: Cultures using NK cell-functionalized Cloudz™ particles combined with IL-2 resulted in a 69% NK cell purity and 29.9-fold expansion. In comparison, cultures using MACS iBeads combined with IL-2 resulted in 49% NK cell purity and a 6.8-fold expansion, suggesting that Cloudz™-based methods provide better expansion. When IL-12 was added to cultures with Cloudz™ particles, both the purity and expansion decreased (45% and 7.2-fold, respectively). When IL-12 and IL-18 were added, the expansion increased to 33.9-fold and the purity increased to 60%. The best combination was IL-2/IL-12/IL-18/IL-21 which had an 88.9-fold expansion with a 78% purity. IL-12 and IL-18 mimic the activating signals released by dendritic cells and IL-2 and IL-21 mimic the activating signals released by activated T cells.

Conclusion: These data demonstrate that Cloudz™ particles functionalized with αNKp46 and αCD2 can efficiently induce NK activation and expansion with high purity and growth. In future studies, we will determine if NK cells expanded using this method show killing ability of cancer cells and persistence in in vivo models. We will also further explore the possibilities of this novel system for rapid expansion and recovery of specific NK cell subtypes.

Citation Format: Christopher Johnson, Hannah Senior, Nithya Jesuraj. Activating and expanding NK cells using dissolvable alginate particles functionalized with αNKp46 and αCD2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-072.

Abstract LB-141: Specific and potent silencing of K-Ras by asymmetric silencing RNA (aiRNA) reveals addiction of cancer stem cells to mutant K-Ras amplification

K-Ras, the first oncogene identified in human cancer, is mutated in about 30% of human solid tumors. K-Ras protein, a small membrane-bound GTP-binding protein, acts as a molecular switch to transduce cell proliferation signals. Activating mutations of K-Ras lock the Ras protein into the hyper-active GTP-bound state, resulting in the activation of numerous signaling pathways that control cell survival and proliferation. Ras is also an important oncoprotein in many cancers where it is not mutated since Ras can be functionally activated through aberrant activation of other signal transduction elements. Activated K-Ras proteins are, therefore, found in a large proportion of all human cancers, and occupy a central position of interest.

Hypermalignant cancer cells, termed cancer stem cells (CSCs), that are highly tumorigenic and metastatic have been isolated from cancer patients with a variety of tumor types and found to have high stemness properties. These stemness-high cancer cells are hypothesized to be fundamentally responsible for cancer metastasis and relapse. Furthermore, a number of stemness genes, such as beta-catenin, nanog, Sox2, Oct3/4 have been implicated in cancer cell stemness. The role of oncogenes such as K-Ras in cancer cell stemness, however, is not clear.

To elucidate the role of K-Ras in the maintenance of cancer cell stemness, we employed asymmetric silencing RNA technology (aiRNA) which is able to silence target genes with high potency and precision. Moreover, aiRNA technology can be readily applied to CSCs. Here we report, to our surprise, that CSCs are not simply addicted to activating mutations of K-Ras, or activation of downstream regulators of the Ras pathway. However, CSCs with amplified mutant K-Ras are highly sensitive to K-Ras silencing. Moreover, the DNA copy number of the mutant K-Ras directly predicts the sensitivity of CSCs to K-Ras silencing. Our studies suggest that amplified mutated K-Ras is required for the maintenance of malignancy and cancer cell stemness, which may have significant implications for understanding the connections between oncogenes and cancer cell stemness, and for developing cancer stem cell inhibitors.

Citation Format: Jun Oishi, Hiroki Umehara, Nithya Jesuraj, Jelena Barbulovic, Xiangao Sun, Chiang J. Li. Specific and potent silencing of K-Ras by asymmetric silencing RNA (aiRNA) reveals addiction of cancer stem cells to mutant K-Ras amplification. [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-141. doi:10.1158/1538-7445.AM2015-LB-141

Abstract LB-47: Specific and potent silencing of K-Ras by asymmetric RNA technology reveals addiction of gastric cancer stem cells

The protein K-Ras is a molecular switch that under normal conditions regulates cell growth and cell division. Mutations in this protein lead to the formation of tumors through continuous cell growth. About 30% of human cancers have a mutated Ras protein that is constitutively bound to GTP due to decreased GTPase activity and insensitivity to GAP action. Ras is also an important factor in many cancers in which it is not mutated but rather functionally activated through inappropriate activity of other signal transduction elements. Mutated K-Ras proteins are found in a large proportion of all tumour cells. K-Ras protein occupies a central position of interest. The identification of oncogenically mutated K-Ras in many human cancers led to major efforts to target this constitutively activated protein as a rational and selective treatment. Despite decades of active agent research, significant challenges still remain to develop therapeutic inhibitors of K-Ras.

To elucidate the function of K-Ras in the cancer development and maintenance, we developed asymmetric interfering RNAs (aiRNAs) which are able to silence target genes with high potency leading to long-lasting knockdown, and reducing off-target effects, and investigated the dependency of K-ras on cell survival in several types of human cancer cell lines. Much to our surprise, we found K-Ras plays a more significant role for gastric cancer maintenance compared to other types of cancer. Here we report aiRNA-induced silencing of K-Ras inhibited the cell proliferation of gastric cancer cells and the ability of gastric cancer cells to form colonies compared to other cancer types. Accumulating evidence has revealed that cancer stem cells (CSCs) are highly associated with prognosis, metastasis, and recurrence. To investigate the effect of K-Ras on CSCs, we tested the K-Ras gene silencing effects on an in vitro CSC culturing system. As a result, K-Ras inhibition decreased the colonies derived from gastric CSCs and altered the gene expression patterns of several genes involved in “stemness” compared to other cancer types. The results of these studies suggest that gastric cancer and gastric CSCs are affected by the K-Ras oncogene and that Kras aiRNAs are promising therapeutic candidates for the treatment of gastric cancer.

Citation Format: Xiangao Sun, Youzhi Li, Hiroki Umehara, Jun Oishi, Nithya Jesuraj, Jelena Barbulovic, Xiaoshu Dai, Keyur Gada, Chiang Li. Specific and potent silencing of K-Ras by asymmetric RNA technology reveals addiction of gastric cancer stem cells. [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 LB-47. doi:10.1158/1538-7445.AM2014-LB-47

Nerve guidance conduits based on double-layered scaffolds of electrospun nanofibers for repairing the peripheral nervous system

Compared to the nerve guidance conduits (NGCs) constructed from a single layer of aligned nanofibers, bilayer NGCs with random and aligned nanofibers in the outer and inner layers are more robust and tear-resistant during surgical procedures thanks to an isotropic mechanical property provided by the random nanofibers. However, it remains unclear whether the random nanofibers will interfere with the aligned nanofibers to alter the extension pattern of the neurites and impede regeneration. To answer this question, we seeded dorsal root ganglia (DRG) on a double-layered scaffold, with aligned and random nanofibers on the top and bottom layers, respectively, and evaluated the outgrowth of neurites. The random nanofibers in the bottom layer exerted a negative impact on the extension of neurites projecting from the DRG, giving neurites a less ordered structure compared to those cultured on a single layer of aligned nanofibers. The negative impact of the random nanofibers could be effectively mitigated by preseeding the double-layered scaffold with Schwann cells. DRG cultured on top of such a scaffold exhibited a neurite outgrowth pattern similar to that for DRG cultured on a single layer of aligned nanofibers. We further fabricated bilayer NGCs from the double-layered scaffolds and tested their ability to facilitate nerve regeneration in a rat sciatic nerve injury model. Both histomorphometric analysis and functional characterization demonstrated that bilayer NGCs with an inner surface that was preseeded with Schwann cells could reach 54%, 64.2%, and 74.9% of the performance of isografts in terms of nerve fiber number, maximum isometric tetanic force, and mass of the extensor digitorum longus muscle, respectively. It can be concluded that the bilayer NGCs hold great potential in facilitating motor axon regeneration and functional motor recovery.

Elastic characterization of transversely isotropic soft materials by dynamic shear and asymmetric indentation

The mechanical characterization of soft anisotropic materials is a fundamental challenge because of difficulties in applying mechanical loads to soft matter and the need to combine information from multiple tests. A method to characterize the linear elastic properties of transversely isotropic soft materials is proposed, based on the combination of dynamic shear testing (DST) and asymmetric indentation. The procedure was demonstrated by characterizing a nearly incompressible transversely isotropic soft material. A soft gel with controlled anisotropy was obtained by polymerizing a mixture of fibrinogen and thrombin solutions in a high field magnet (B = 11.7 T); fibrils in the resulting gel were predominantly aligned parallel to the magnetic field. Aligned fibrin gels were subject to dynamic (20-40 Hz) shear deformation in two orthogonal directions. The shear storage modulus was 1.08 ± 0. 42 kPa (mean ± std. dev.) for shear in a plane parallel to the dominant fiber direction, and 0.58 ± 0.21 kPa for shear in the plane of isotropy. Gels were indented by a rectangular tip of a large aspect ratio, aligned either parallel or perpendicular to the normal to the plane of transverse isotropy. Aligned fibrin gels appeared stiffer when indented with the long axis of a rectangular tip perpendicular to the dominant fiber direction. Three-dimensional numerical simulations of asymmetric indentation were used to determine the relationship between direction-dependent differences in indentation stiffness and material parameters. This approach enables the estimation of a complete set of parameters for an incompressible, transversely isotropic, linear elastic material.