Anna Kozlowska

TLR9-mediated siRNA delivery for targeting of normal and malignant human hematopoietic cells in vivo

STAT3 operates in both cancer cells and tumor-associated immune cells to promote cancer progression. As a transcription factor, it is a highly desirable but difficult target for pharmacologic inhibition. We have recently shown that the TLR9 agonists CpG oligonucleotides can be used for targeted siRNA delivery to mouse immune cells. In the present study, we demonstrate that a similar strategy allows for targeted gene silencing in both normal and malignant human TLR9(+) hematopoietic cells in vivo. We have developed new human cell-specific CpG(A)-STAT3 siRNA conjugates capable of inducing TLR9-dependent gene silencing and activation of primary immune cells such as myeloid dendritic cells, plasmacytoid dendritic cells, and B cells in vitro. TLR9 is also expressed by several human hematologic malignancies, including B-cell lymphoma, multiple myeloma, and acute myeloid leukemia. We further demonstrate that oncogenic proteins such as STAT3 or BCL-X(L) are effectively knocked down by specific CpG(A)-siRNAs in TLR9(+) hematologic tumor cells in vivo. Targeting survival signaling using CpG(A)-siRNAs inhibits the growth of several xenotransplanted multiple myeloma and acute myeloid leukemia tumors. CpG(A)-STAT3 siRNA is immunostimulatory and nontoxic for normal human leukocytes in vitro. The results of the present study show the potential of using tumoricidal/immunostimulatory CpG-siRNA oligonucleotides as a novel 2-pronged therapeutic strategy for hematologic malignancies.

Leukemia cell–targeted STAT3 silencing and TLR9 triggering generate systemic antitumor immunity

Signal transducer and activator of transcription 3 (STAT3) is an oncogene and immune checkpoint commonly activated in cancer cells and in tumor-associated immune cells. We previously developed an immunostimulatory strategy based on targeted Stat3 silencing in Toll-like receptor 9 (TLR9)-positive hematopoietic cells using CpG-small interfering RNA (siRNA) conjugates. Here, we assessed the therapeutic effect of systemic STAT3 blocking/TLR9 triggering in disseminated acute myeloid leukemia (AML). We used mouse Cbfb-MYH11/Mpl-induced leukemia model, which mimics human inv(16) AML. Our results demonstrate that intravenously delivered CpG-Stat3 siRNA, but not control oligonucleotides, can eradicate established AML and impair leukemia-initiating potential. These antitumor effects require hosts effector T cells but not TLR9-positive antigen-presenting cells. Instead, CpG-Stat3 siRNA has direct immunogenic effect on AML cells in vivo upregulating major histocompatibility complex class-II, costimulatory and proinflammatory mediators, such as interleukin-12, while downregulating coinhibitory PD-L1 molecule. Systemic injections of CpG-Stat3 siRNA generate potent tumor antigen-specific immune responses, increase the ratio of tumor-infiltrating CD8(+) T cells to regulatory T cells in various organs, and result in CD8(+) T-cell-dependent regression of leukemia. Our findings underscore the potential of using targeted STAT3 inhibition/TLR9 triggering to break tumor tolerance and induce immunity against AML and potentially other TLR9-positive blood cancers.

TLR9 Signaling in the Tumor Microenvironment Initiates Cancer Recurrence after Radiotherapy

Cancer radiotherapy may be immunogenic, but it is unclear why its immunogenic effects are rarely sufficient to prevent tumor recurrence. Here, we report a novel Toll-like receptor 9 (TLR9)-dependent mechanism that initiates tumor regrowth after local radiotherapy. Systemic inhibition of TLR9, but not TLR4, delayed tumor recurrence in mouse models of B16 melanoma, MB49 bladder cancer, and CT26 colon cancer after localized high-dose tumor irradiation. Soluble factors in the microenvironment of regressing tumors triggered TLR9 signaling in freshly recruited myeloid cells appearing within four days of radiotherapy. The tumorigenic effects of TLR9 depended on MyD88/NF-κB-mediated upregulation of interleukin (IL)-6 expression, which in turn resulted in downstream activation of Jak/STAT3 signaling in myeloid cells. In comparing global gene expression in wild-type, TLR9-, or STAT3-deficient myeloid cells derived from irradiated tumors, we identified a unique set of TLR9/STAT3-regulated genes involved in tumor-promoting inflammation and revascularization. Blocking STAT3 function by two myeloid-specific genetic strategies corrected TLR9-mediated cancer recurrence after radiotherapy. Our results suggest that combining localized tumor irradiation with myeloid cell-specific inhibition of TLR9/STAT3 signaling may help eliminate radioresistant cancers.

Augmented IFN-γ and TNF-α Induced by Probiotic Bacteria in NK Cells Mediate Differentiation of Stem-Like Tumors Leading to Inhibition of Tumor Growth and Reduction in Inflammatory Cytokine Release; Regulation by IL-10.

Our previous reports demonstrated that the magnitude of natural killer (NK) cell-mediated cytotoxicity correlate directly with the stage and level of differentiation of tumor cells. In addition, we have shown previously that activated NK cells inhibit growth of cancer cells through induction of differentiation, resulting in the resistance of tumor cells to NK cell-mediated cytotoxicity through secreted cytokines, as well as direct NK-tumor cell contact. In this report, we show that in comparison to IL-2 + anti-CD16mAb-treated NK cells, activation of NK cells by probiotic bacteria (sAJ2) in combination with IL-2 and anti-CD16mAb substantially decreases tumor growth and induces maturation, differentiation, and resistance of oral squamous cancer stem cells, MIA PaCa-2 stem-like/poorly differentiated pancreatic tumors, and healthy stem cells of apical papillae through increased secretion of IFN-γ and TNF-α, as well as direct NK-tumor cell contact. Tumor resistance to NK cell-mediated killing induced by IL-2 + anti-CD16mAb + sAJ2-treated NK cells is induced by combination of IFN-γ and TNF-α since antibodies to both, and not each cytokine alone, were able to restore tumor sensitivity to NK cells. Increased surface expression of CD54, B7H1, and MHC-I on NK-differentiated tumors was mediated by IFN-γ since the addition of anti-IFN-γ abolished their increase and restored the ability of NK cells to trigger cytokine and chemokine release; whereas differentiated tumors inhibited cytokine release by the NK cells. Monocytes synergize with NK cells in the presence of probiotic bacteria to induce regulated differentiation of stem cells through secretion of IL-10 resulting in resistance to NK cell-mediated cytotoxicity and inhibition of cytokine release. Therefore, probiotic bacteria condition activated NK cells to provide augmented differentiation of cancer stem cells resulting in inhibition of tumor growth, and decreased inflammatory cytokine release.

Differentiation by NK cells is a prerequisite for effective targeting of cancer stem cells/poorly differentiated tumors by chemopreventive and chemotherapeutic drugs

Natural Killer (NK) cells target oral, pancreatic, lung, breast, glioblastoma and melanoma stem-like/poorly differentiated tumors. Differentiation of the abovementioned tumors with supernatants from split-anergized NK cells decreases their susceptibility to NK cells, but increases their sensitivity to cisplatin (CDDP)-mediated cell death. Breast and melanoma tumor cells with CD44 knockdown display enhanced susceptibility to NK cell-mediated lysis, potentially due to decreased differentiation. We also demonstrate that sulindac, a non-steroidal anti-inflammatory drug and a chemopreventive agent, not only limits the growth of oral tumor cells, but also aids in cancer cell elimination by NK cells. Treatment of oral tumors with sulindac, but not adriamycin inversely modulates the expression and function of NFκB and JNK, resulting in a significant down-regulation of IL-6, and VEGF secretion by oral tumor cells. In addition, increased secretion of IL-6 and VEGF is blocked by sulindac during interaction of oral tumors with NK cells. Sulindac treatment prevents synergistic induction of VEGF secretion by the tumor cells after their co-culture with untreated NK cells since non-activated NK cells lack the ability to efficiently kill tumor cells. Moreover, sulindac is able to profoundly reduce VEGF secretion by tumor cells cultured with IL-2 activated NK cells, which are able to significantly lyse the tumor cells. Based on the data presented in this study, we propose the following combinatorial approach for the treatment of stem-like/ poorly differentiated tumors in cancer patients with metastatic disease. Stem-like/ poorly differentiated tumor cells may in part undergo lysis or differentiation after NK cell immunotherapy, followed by treatment of differentiated tumors with chemotherapy and chemopreventive agents to eliminate the bulk of the tumor. This dual approach should limit tumor growth and prevent metastasis.

Novel Strategy to Expand Super-Charged NK Cells with Significant Potential to Lyse and Differentiate Cancer Stem Cells: Differences in NK Expansion and Function between Healthy and Cancer Patients

Natural killer (NK) cells are known to target cancer stem cells and undifferentiated tumors. In this paper, we provide a novel strategy for expanding large numbers of super-charged NK cells with significant potential to lyse and differentiate cancer stem cells and demonstrate the differences in the dynamics of NK cell expansion between healthy donors and cancer patients. Decline in cytotoxicity and lower interferon (IFN)-γ secretion by osteoclast (OC)-expanded NK cells from cancer patients correlates with faster expansion of residual contaminating T cells within purified NK cells, whereas healthy donors’ OCs continue expanding super-charged NK cells while limiting T cell expansion for up to 60 days. Similar to patient NK cells, NK cells from tumor-bearing BLT-humanized mice promote faster expansion of residual T cells resulting in decreased numbers and function of NK cells, whereas NK cells from mice with no tumor continue expanding NK cells and retain their cytotoxicity. In addition, dendritic cells (DCs) in contrast to OCs are found to promote faster expansion of residual T cells within purified NK cells resulting in the decline in NK cell numbers from healthy individuals. Addition of anti-CD3 mAb inhibits T cell proliferation while enhancing NK cell expansion; however, expanding NK cells have lower cytotoxicity but higher secretion of IFN-γ. Expansion and functional activation of super-charged NK cells by OCs is dependent on interleukin (IL)-12 and IL-15. Thus, in this report, we not only provide a novel strategy to expand super-charged NK cells, but also demonstrate that rapid and sustained expansion of residual T cells within the purified NK cells during expansion with DCs or OCs could be a potential mechanism by which the numbers and function of NK cells decline in cancer patients and in BLT-humanized mice.

Differential Cytotoxicity but Augmented IFN-γ Secretion by NK Cells after Interaction with Monocytes from Humans, and Those from Wild Type and Myeloid-Specific COX-2 Knockout Mice

The list of genes, which augment NK cell function when knocked out in neighboring cells is increasing, and may point to the fundamental function of NK cells targeting cells with diminished capability to differentiate optimally since NK cells are able to target less differentiated cells, and aid in their differentiation. In this paper, we aimed at understanding the effect of monocytes from targeted knockout of COX-2 in myeloid cells (Cox-2flox/flox;LysMCre/+) and from control littermates (Cox-2flox/flox;LysM+/+) on ex vivo function of NK cells. Furthermore, we compared the effect of monocytes treated with and without lipopolysaccharide (LPS) on NK cells from mice and humans. NK cells purified from Cox-2flox/flox;LysMCre/+ mice had heightened cytotoxic activity when compared to those obtained from control littermates. In addition, NK cells cultured with autologous Cox-2flox/flox;LysMCre/+ monocytes and DCs, mouse embryonic fibroblasts from global knockout COX-2, but not with knockout of COX-2 in T cells, had increased cytotoxic function as well as augmented IFN-γ secretion when compared to NK cells from control littermates cultured with monocytes. LPS inhibited NK cell cytotoxicity while increasing IFN-γ secretion when cultured in the presence of monocytes from either Cox-2flox/flox;LysMCre/+ or control littermates. In contrast to mice, NK cells from humans when cultured with monocytes lost cytotoxic function and gained ability to secrete large amounts of IFN-γ, a process, which we had previously coined as “split anergy.” Similar to mice, LPS potentiated the loss of human NK cell cytotoxicity while increasing IFN-γ secretion in the presence of monocytes. Greater loss of cytotoxicity and larger secretion of IFN-γ in NK cells induced by gene knockout cells may be important for the greater need of these cells for differentiation.

Fyn and CD70 Expression in CD4+ T Cells from Patients with Systemic Lupus Erythematosus

Objective. CD4+ T cells from patients with systemic lupus erythematosus (SLE) display defective function that contributes to abnormal activation of B cells and autoantibody production. Methods. We compared the transcript and protein levels of Fyn and CD70 in CD4+ T cells from patients with SLE (n = 41) and healthy individuals (n = 34). The CD4+ T cells were isolated by positive biomagnetic separation technique. The quantitative analysis of messenger RNA was performed by reverse transcription and real-time quantitative PCR. The protein contents in the CD4+ T cells were determined by Western blotting analysis. Results. We observed significantly higher levels of Fyn (p = 0.03) and CD70 (p = 0.029) transcripts in SLE CD4+ T cells than in controls. There was a significant increase in CD70 protein levels (p < 0.0001), but not Fyn protein levels (p = 0.081) in CD4+ T cells from patients with SLE compared to healthy individuals. In the group with high disease activity [SLE Disease Activity Index (SLEDAI) ≥ 9], we observed a significantly higher Fyn protein content than in controls (p = 0.030). There was no correlation between Fyn and CD70 protein levels in SLE CD4+ T cells and disease activity as expressed in the SLEDAI scale. Conclusion. We confirmed previous observations of higher expression of CD70 in CD4+ T cells from patients with SLE. Our findings suggest that increased Fyn protein content in CD4+ T cells can be associated with high SLE disease activity.

Functionalized bioengineered spider silk spheres improve nuclease resistance and activity of oligonucleotide therapeutics providing a strategy for cancer treatment

Cell-selective delivery and sensitivity to serum nucleases remain major hurdles to the clinical application of RNA-based oligonucleotide therapeutics, such as siRNA. Spider silk shows great potential as a biomaterial due to its biocompatibility and biodegradability. Self-assembling properties of silk proteins allow for processing into several different morphologies such as fibers, scaffolds, films, hydrogels, capsules and spheres. Moreover, bioengineering of spider silk protein sequences can functionalize silk by adding peptide moieties with specific features including binding or cell recognition domains. We demonstrated that modification of silk protein by adding the nucleic acid binding domain enabled the development of a novel oligonucleotide delivery system that can be utilized to improve pharmacokinetics of RNA-based therapeutics, such as CpG-siRNA. The MS2 bioengineered silk was functionalized with poly-lysine domain (KN) to generate hybrid silk MS2KN. CpG-siRNA efficiently bound to MS2KN in contrary to control MS2. Both MS2KN complexes and spheres protected CpG-siRNA from degradation by serum nucleases. CpG-siRNA molecules encapsulated into MS2KN spheres were efficiently internalized and processed by TLR9-positive macrophages. Importantly, CpG-STAT3siRNA loaded in silk spheres showed delayed and extended target gene silencing compared to naked oligonucleotides. The prolonged Stat3 silencing resulted in the more pronounced downregulation of interleukin 6 (IL-6), a proinflammatory cytokine and upstream activator of STAT3, which limits the efficacy of TLR9 immunostimulation. Our results demonstrate the feasibility of using spider silk spheres as a carrier of therapeutic nucleic acids. Moreover, the modified kinetic and activity of the CpG-STAT3siRNA embedded into silk spheres is likely to improve immunotherapeutic effects in vivo. STATEMENT OF SIGNIFICANCE We demonstrated that modification of silk protein by adding the nucleic acid binding domain enabled the development of a novel oligonucleotide delivery system that can be utilized to improve pharmacokinetics of RNA-based therapeutics. Although, the siRNA constructs have already given very promising results in the cancer therapy, the in vivo application of RNA-based oligonucleotide therapeutics still is limited due to their sensitivity to serum nucleases and some toxicity. We propose a carrier for RNA-based therapeutics that is made of bioengineered spider silk. We showed that functionalized bioengineered spider silk spheres not only protected RNA-based therapeutics from degradation by serum nucleases, but what is more important the embedding of siRNA into silk spheres delayed and extended target gene silencing compared with naked oligonucleotides. Moreover, we showed that plain silk spheres did not have unspecific effect on target gene levels proving not only to be non-cytotoxic but also very neutral vehicles in terms of TLR9/STAT3 activation in macrophages. We demonstrated advantages of novel delivery technology in safety and efficacy comparing with delivery of naked CpG-STAT3siRNA therapeutics.

Novel strategies to target cancer stem cells by NK cells; studies in humanized mice.

We have previously shown that following selection, Natural Killer (NK) cells, differentiate Cancer stem cells (CSCs)/undifferentiated or poorly differentiated tumors via secreted and membrane bound IFN-gamma and TNF-alpha, leading to prevention of tumor growth and remodeling of the tumor microenvironment. Since conventional therapeutic strategies including chemotherapy and radiotherapy remain unsuccessful in treating stem-like tumors, there has been an increasing interest in NK cell based immunotherapy for the treatment of resistant tumors. In our recent studies, we used bone marrow, liver, thymus humanized (hu-BLT) mouse model to demonstrate the efficacy of adoptive transfer of ex vivo expanded super-charged NK cells in the selection and differentiation of stem-like tumors within the context of a fully reconstituted human immune system. We have also shown that CSCs differentiated with split anergized NK cells prior to implantation in humanized mice did not grow or metastasize. In this review, we present current advances in NK cell detection, expansion and therapeutic delivery, and discuss the utility of different humanized mouse models in studying NK cell based therapies in the preclinical settings.