Enhances Tumor Cell Survival Research Articles

The Role of Tumor-Associated Macrophages in Cancer Immunoevasion and Therapy Resistance

Tumor-associated macrophages (TAMs) are crucial components of the tumor microenvironment, playing significant roles in cancer progression, immune evasion, and therapy resistance. Originating from circulating monocytes, TAMs can polarize into M1 and M2 phenotypes, with M2-like TAMs predominating in many cancers. This M2 polarization fosters an immunosuppressive environment that promotes tumor growth, metastasis, and resistance to therapies, including chemotherapy and immune checkpoint inhibitors. TAMs secrete various cytokines, chemokines, and growth factors that enhance tumor cell survival, promote angiogenesis, and recruit additional immunosuppressive cells such as regulatory T cells. They also express immune checkpoint molecules, further inhibiting effective anti-tumor immune responses. Given their dual role in supporting tumor survival and mediating immune evasion, TAMs represent an attractive target for therapeutic intervention. Current strategies to target TAMs include depletion, reprogramming, and combination therapies aimed at enhancing anti-tumor immunity. This review explores the complex biology of TAMs, their mechanisms of action in promoting cancer immunoevasion and therapy resistance, and the therapeutic strategies being developed to exploit their unique characteristics. By providing insights into the multifaceted roles of TAMs, this review aims to highlight potential avenues for improving cancer treatment outcomes and addressing the challenges posed by tumor-induced immune suppression. Keywords: Tumor-Associated Macrophages (TAMs), Immune Evasion, Therapy Resistance, Macrophage Polarization, Immunotherapy

CTNI-73. ASSESSMENT OF MOLECULAR ALTERATIONS IN NEWLY DIAGNOSED GBM MGMT-UNMETHYLATED PATIENTS TREATED WITH VAL-083

Abstract Glioblastoma (GBM) commonly features molecular alterations in the TERT, EGFR, PTEN, and TP53 genes, which contributes to uncontrolled cell growth, evasion of apoptosis, and enhanced tumor cell survival. VAL-083 is a bi-functional DNA-targeting agent which rapidly induces inter-strand DNA cross-links at N7 and O6-guanine inducing double-strand breaks causing cell death independently of MGMT DNA repair and DNA mismatch repair deficiency. VAL-083 was evaluated in an open-label, biomarker-driven, phase 2 trial in MGMT-unmethylated, bevacizumab-naïve GBM patients. The molecular profile of tumors from a newly diagnosed GBM patient subgroup who received VAL-083 alone after chemo-radiation with concurrent TMZ, was determined in order to correlate with clinical outcomes. Thirty-four (34/36, 94.4%) patients who received 30 mg/m2 VAL-083 (days 1-3 of 21-day cycle) had available next-generation sequencing data on their primary tissue. Patient median age was 54.8 years (5-95pth: 29.8-66.0), median KPS was 90 (5-95pth: 80-100) and 58.8% were males. The median number of cycles of VAL-083 was 7.5 (5-95pth: 1-12). There were 5 dose reductions due to toxicity. The median time to progression (PFS) and overall survival (OS) were 9.2 mo (95%CI: 7.6-10.2) and 16.5 mo (95%CI: 13.3-19.0), respectively. The mean number of molecular alterations was 3.9 (5-95pth 1-8). Six (17.6%) patients had gene fusions. The most common molecular alterations were TERT promoter (91.2%), EGFR amplification (amp) (52.9%), PTEN (50.0%), EGFR (20.6%), and TP53 (20.6%). Additional alterations (in ≥2 patients; 6%) included EGFR-EGFR (EGFRvIII), BRCA2, CDKN2A/B, CDK4/6 amp, MDM2/4 amp, NF1, NOTCH1, PIK3R1 and RB1. While TP53 mutations showed a trend as predictors for time to progression (P 0.027), this was not observed with OS. None of the molecular alterations were predictors of number of treatment cycles or dose reductions. No specific molecular alterations were identified that predicted either improved or poorer patient outcome, during treatment with VAL-083. Clinicaltrials.gov identifier: NCT02717962.

CNSC-37. ROLE OF PGE2-REGULATED NEUROINFLAMMATION IN CONSTRUCTING NEURON-NK-GLIOMA CIRCUIT FOR GLIOBLASTOMA

Abstract Glioblastoma (GBM), known for its aggressive nature and poor prognosis, frequently recurs and resists standard treatments such as temozolomide (TMZ). This resistance is partly due to complex interactions within the tumor microenvironment, particularly involving neuronal excitation. Recent insights suggest that neuronal activity, through mechanisms like neurogliomal synapses, not only promotes glioma cell proliferation but also contributes to the chemoresistance observed in recurrent tumors. Our focus is on Prostaglandin E2 (PGE2), a mediator that regulates neuronal excitation, and its role in the recurrence and resistance of GBM. We discovered that PGE2 upregulates synaptic proteins and alters neurotransmitter profiles, enhancing tumor cell survival and resistance to TMZ. Specifically, increased levels of neurotransmitters such as glutamine and asparagine were observed in PGE2-rich environments, correlating with heightened chemoresistance and tumor recurrence. Co-culture experiments further demonstrated that PGE2-treated neuronal cells could induce resistance in adjacent GBM cells. These findings highlight the potential of targeting PGE2 pathways as a therapeutic strategy. A significant advancement in our study was the development and application of compound #038, a novel celecoxib derivative designed to cross the blood-brain barrier (BBB). This compound demonstrated enhanced efficacy in inhibiting GBM growth and improving survival rates in mouse models, indicating its potential as an effective therapeutic agent against GBM.

Single-cell and spatial transcriptome assays reveal heterogeneity in gliomas through stress responses and pathway alterations.

Glioma is a highly heterogeneous malignancy of the central nervous system. This heterogeneity is driven by various molecular processes, including neoplastic transformation, cell cycle dysregulation, and angiogenesis. Among these biomolecular events, inflammation and stress pathways in the development and driving factors of glioma heterogeneity have been reported. However, the mechanisms of glioma heterogeneity under stress response remain unclear, especially from a spatial aspect. This study employed single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics (ST) to explore the impact of oxidative stress response genes in oligodendrocyte precursor cells (OPCs). Our analysis identified distinct pathways activated by oxidative stress in two different types of gliomas: high- and low- grade (HG and LG) gliomas. In HG gliomas, oxidative stress induced a metabolic shift from oxidative phosphorylation to glycolysis, promoting cell survival by preventing apoptosis. This metabolic reprogramming was accompanied by epithelial-to-mesenchymal transition (EMT) and an upregulation of stress response genes. Furthermore, SCENIC (Single-Cell rEgulatory Network Inference and Clustering) analysis revealed that oxidative stress activated the AP1 transcription factor in HG gliomas, thereby enhancing tumor cell survival and proliferation. Our findings provide a novel perspective on the mechanisms of oxidative stress responses across various grades of gliomas. This insight enhances our comprehension of the evolutionary processes and heterogeneity within gliomas, potentially guiding future research and therapeutic strategies.

In vivo imaging system (IVIS) therapeutic assessment of tyrosine kinase inhibitor-loaded gold nanocarriers for acute myeloid leukemia: a pilot study.

Acute myeloid leukemia (AML) is a malignancy in the myeloid lineage that is characterized by symptoms like fatigue, bleeding, infections, or anemia, and it can be fatal if untreated. In AML, mutations in tyrosine kinases (TKs) lead to enhanced tumor cell survival. The most frequent mutations in TKs are reported in Fms-like tyrosine kinase 3 (FLT3), Janus kinase 2 (JAK2), and KIT (tyrosine-protein kinase KIT), making these TKs potential targets for TK inhibitor (TKI) therapies in AML. With 30% of the mutations in TKs, mutated FLT3 is associated with poor overall survival and an increased chance of resistance to therapy. FLT3 inhibitors are used in FLT3-mutant AML, and the combination with hypomethylating agents displayed promising results. Midostaurin (MDS) is the first targeted therapy in FLT3-mutant AML, and its combination with chemotherapy showed good results. However, chemotherapies induce several side effects, and an alternative to chemotherapy might be the use of nanoparticles for better drug delivery, improved bioavailability, reduced drug resistance and induced toxicity. The herein study presents MDS-loaded gold nanoparticles and compares its efficacy with MDS alone, on both in vitro and in vivo models, using the FLT3-ITD-mutated AML cell line MV-4-11 Luc2 transfected to express luciferin. Our preclinical study suggests that MDS-loaded nanoparticles have a better tumor inhibitory effect than free drugs on in vivo models by controlling tumor growth in the first half of the treatment, while in the second part of the therapy, the tumor size was comparable to the cohort that was treatment-free.

The C1q and gC1qR axis as a novel checkpoint inhibitor in cancer.

Understanding at the molecular level of the cell biology of tumors has led to significant treatment advances in the past. Despite such advances however, development of therapy resistance and tumor recurrence are still unresolved major challenges. This therefore underscores the need to identify novel tumor targets and develop corresponding therapies to supplement existing biologic and cytotoxic approaches so that a deeper and more sustained treatment responses could be achieved. The complement system is emerging as a potential novel target for cancer therapy. Data accumulated to date show that complement proteins, and in particular C1q and its receptors cC1qR/CR and gC1qR/p33/HABP1, are overexpressed in most cancer cells and together are involved not only in shaping the inflammatory tumor microenvironment, but also in the regulation of angiogenesis, metastasis, and cell proliferation. In addition to the soluble form of C1q that is found in plasma, the C1q molecule is also found anchored on the cell membrane of monocytes, macrophages, dendritic cells, and cancer cells, via a 22aa long leader peptide found only in the A-chain. This orientation leaves its 6 globular heads exposed outwardly and thus available for high affinity binding to a wide range of molecular ligands that enhance tumor cell survival, migration, and proliferation. Similarly, the gC1qR molecule is not only overexpressed in most cancer types but is also released into the microenvironment where it has been shown to be associated with cancer cell proliferation and metastasis by activation of the complement and kinin systems. Co-culture of either T cells or cancer cells with purified C1q or anti-gC1qR has been shown to induce an anti-proliferative response. It is therefore postulated that in the tumor microenvironment, the interaction between C1q expressing cancer cells and gC1qR bearing cytotoxic T cells results in T cell suppression in a manner akin to the PD-L1 and PD-1 interaction.

Non-Canonical Activin A Signaling Stimulates Context-Dependent and Cellular-Specific Outcomes in CRC to Promote Tumor Cell Migration and Immune Tolerance.

We have shown that activin A (activin), a TGF-β superfamily member, has pro-metastatic effects in colorectal cancer (CRC). In lung cancer, activin activates pro-metastatic pathways to enhance tumor cell survival and migration while augmenting CD4+ to CD8+ communications to promote cytotoxicity. Here, we hypothesized that activin exerts cell-specific effects in the tumor microenvironment (TME) of CRC to promote anti-tumoral activity of immune cells and the pro-metastatic behavior of tumor cells in a cell-specific and context-dependent manner. We generated an Smad4 epithelial cell specific knockout (Smad4-/-) which was crossed with TS4-Cre mice to identify SMAD-specific changes in CRC. We also performed IHC and digital spatial profiling (DSP) of tissue microarrays (TMAs) obtained from 1055 stage II and III CRC patients in the QUASAR 2 clinical trial. We transfected the CRC cells to reduce their activin production and injected them into mice with intermittent tumor measurements to determine how cancer-derived activin alters tumor growth in vivo. In vivo, Smad4-/- mice displayed elevated colonic activin and pAKT expression and increased mortality. IHC analysis of the TMA samples revealed increased activin was required for TGF-β-associated improved outcomes in CRC. DSP analysis identified that activin co-localization in the stroma was coupled with increases in T-cell exhaustion markers, activation markers of antigen presenting cells (APCs), and effectors of the PI3K/AKT pathway. Activin-stimulated PI3K-dependent CRC transwell migration, and the in vivo loss of activin lead to smaller CRC tumors. Taken together, activin is a targetable, highly context-dependent molecule with effects on CRC growth, migration, and TME immune plasticity.

PAQR8 promotes breast cancer recurrence and confers resistance to multiple therapies

BackgroundBreast cancer mortality is principally due to recurrent disease that becomes resistant to therapy. We recently identified copy number (CN) gain of the putative membrane progesterone receptor PAQR8 as one of four focal CN alterations that preferentially occurred in recurrent metastatic tumors compared to primary tumors in breast cancer patients. Whether PAQR8 plays a functional role in cancer is unknown. Notably, PAQR8 CN gain in recurrent tumors was mutually exclusive with activating ESR1 mutations in patients treated with anti-estrogen therapies and occurred in > 50% of both patients treated with anti-estrogen therapies and those treated with chemotherapy or anti-Her2 agents.MethodsWe used orthotopic mouse models to determine whether PAQR8 overexpression or deletion alters breast cancer dormancy or recurrence following therapy. In vitro studies, including assays for colony formation, cell viability, and relative cell fitness, were employed to identify effects of PAQR8 in the context of therapy. Cell survival and proliferation were quantified by immunofluorescence staining for markers of apoptosis and proliferation. Sphingolipids were quantified by liquid chromatography-high resolution mass spectrometry.ResultsWe show that PAQR8 is necessary and sufficient for efficient mammary tumor recurrence in mice, spontaneously upregulated and CN gained in recurrent tumors that arise following therapy in multiple mouse models, and associated with poor survival following recurrence as well as poor overall survival in breast cancer patients. PAQR8 promoted resistance to therapy by enhancing tumor cell survival following estrogen receptor pathway inhibition by fulvestrant or estrogen deprivation, Her2 pathway blockade by lapatinib or Her2 downregulation, and treatment with chemotherapeutic agents. Pro-survival effects of PAQR8 were mediated by a Gi protein-dependent reduction in cAMP levels, did not require progesterone, and involved a PAQR8-dependent decrease in ceramide levels and increase in sphingosine-1-phosphate levels, suggesting that PAQR8 may possess ceramidase activity.ConclusionsOur data provide in vivo evidence that PAQR8 plays a functional role in cancer, implicate PAQR8, cAMP, and ceramide metabolism in breast cancer recurrence, and identify a novel mechanism that may commonly contribute to the acquisition of treatment resistance in breast cancer patients.

Interleukin 4 Controls the Pro-Tumoral Role of Macrophages in Mammary Cancer Pulmonary Metastasis in Mice.

Simple SummaryMetastasis is the main cause of death from breast cancer. In mouse models of breast cancer lung metastasis, macrophages enhance metastasis by promoting tumor cell seeding and persistent growth. Here, we show that interleukin-4 (IL4) is required for this process as IL4 receptor (IL4rα)-null mice develop fewer and smaller lung metastases. This deficiency is partially rescued by adoptive transfer of wild-type monocytes. IL4 signaling in macrophages upregulates the expression of the chemokine receptor CXCR2, necessary for IL4-mediated tumor cell extravasation in vitro. In addition, expression of several other genes already causally associated with lung metastasis including Ccl2, Csf1, Ccr1, Hgf and Flt1 are upregulated in macrophages. High-resolution intravital imaging at the time of metastatic seeding showed reduced physical interaction between tumor cells and IL4rα-deficient macrophages, showing the dependence on IL4. We conclude that IL4 signaling in monocytes and macrophages is important during seeding and growth of breast metastasis in the lung.Metastasis is the systemic manifestation of cancer and the main cause of death from breast cancer. In mouse models of lung metastases, recruitment of classical monocytes from blood to the lung and their differentiation to metastasis-associated macrophages (MAMs) facilitate cancer cell extravasation, survival and growth. Ablation of MAMs or their monocytic progenitors inhibits metastasis. We hypothesized that factors controlling macrophage polarization modulate tumor cell extravasation in the lung. We evaluated whether signaling by Th1 or Th2 cytokines in macrophages affected transendothelial migration of tumor cells in vitro. Interferon gamma and LPS inhibited macrophage-dependent tumor cell extravasation while the Th2 cytokine interleukin-4 (IL4) enhanced this process. We demonstrated that IL4 receptor (IL4rα)-null mice developed fewer and smaller lung metastasis in E0771-LG mammary cancer models of this disease. Adoptive transfer of wild-type monocytes to IL4rα-deficient mice partially rescued this phenotype. IL4 signaling in macrophages controlled the expression of the chemokine receptor CXCR2, necessary for IL4-mediated tumor cell extravasation in vitro. Furthermore, IL4 signaling in macrophages regulated the transcript abundance of several other genes already causally associated with mammary cancer lung metastasis including Ccl2, Csf1, Ccr1, Hgf and Flt1. The central role of IL4 signaling in MAMs was confirmed by high-resolution intravital imaging of the lung in mice at the time of metastatic seeding, which showed reduced physical interaction between tumor cells and IL4rα-deficient macrophages. This interaction with wild-type MAMs enhanced tumor cell survival and seeding, which was lost in the IL4rα mice. These data indicate that IL4 signaling in monocytes and macrophages is key during seeding and growth of breast metastasis in the lung, as it regulates pro-tumoral paracrine signaling between cancer cells and macrophages.

Genetic and Drug Inhibition of LDH-A: Effects on Murine Gliomas.

Simple SummaryThree different murine glioma cell lines were modified to downregulate expression of the murine LDH-A gene using shRNA knockdown (KD) and compared to pharmacologic (GNE-R-140) inhibition of the LDH enzyme complex, and to shRNA scrambled control (NC) cell lines. The effects of shRNA LDH-A knockdown and LDH drug-targeted inhibition (GNE-R-140) on tumor-cell metabolism, tumor growth, and animal survival were similar in each of the cell lines. However, an unexpected increase in the aggressiveness was observed in LDH-A KD and GNE-R-140 treated GL261 intracranial gliomas, but not in CT2A and ALTS1C1 i.c. gliomas. Our results show that LDH-A KD and GNE-R-140 treated GL261 cells are better able to metabolize lactate as a primary carbon source through the TCA cycle, and are a net consumer of lactate. These results suggest that inhibition of LDH-A/glycolysis may not be a general strategy to inhibit the i.c. growth of all gliomas, and that metabolic-inhibition treatment strategies need to be carefully assessed, since the inhibition of glycolysis may lead to the unexpected development and activation of alternative metabolic pathways resulting in enhanced tumor-cell survival in a nutrient-limited environment, leading to increased tumor aggressiveness.The effects of the LDH-A depletion via shRNA knockdown on three murine glioma cell lines and corresponding intracranial (i.c.) tumors were studied and compared to pharmacologic (GNE-R-140) inhibition of the LDH enzyme complex, and to shRNA scrambled control (NC) cell lines. The effects of genetic-shRNA LDH-A knockdown and LDH drug-targeted inhibition (GNE-R-140) on tumor-cell metabolism, tumor growth, and animal survival were similar. LDH-A KD and GNE-R-140 unexpectedly increased the aggressiveness of GL261 intracranial gliomas, but not CT2A and ALTS1C1 i.c. gliomas. Furthermore, the bioenergetic profiles (ECAR and OCR) of GL261 NC and LDH-A KD cells under different nutrient limitations showed that (a) exogenous pyruvate is not a major carbon source for metabolism through the TCA cycle of native GL261 cells; and (b) the unique upregulation of LDH-B that occurs in GL261 LDH-A KD cells results in these cells being better able to: (i) metabolize lactate as a primary carbon source through the TCA cycle, (ii) be a net consumer of lactate, and (iii) showed a significant increase in the proliferation rate following the addition of 10 mM lactate to the glucose-free media (only seen in GL261 KD cells). Our study suggests that inhibition of LDH-A/glycolysis may not be a general strategy to inhibit the i.c. growth of all gliomas, since the level of LDH-A expression and its interplay with LDH-B can lead to complex metabolic interactions between tumor cells and their environment. Metabolic-inhibition treatment strategies need to be carefully assessed, since the inhibition of glycolysis (e.g., inhibition of LDH-A) may lead to the unexpected development and activation of alternative metabolic pathways (e.g., upregulation of lipid metabolism and fatty-acid oxidation pathways), resulting in enhanced tumor-cell survival in a nutrient-limited environment and leading to increased tumor aggressiveness.

Bacteria in tumors “hit the road” together

Tumors contain bacteria, but the functional significance of this tumor microbiota is not appreciated. Fu etal. show that bacteria within breast tumor cells contribute to metastasis, in part, by enhancing tumor cell survival to mechanical fluid shear stress as would be found in the circulation.

Cancer Burden Is Controlled by Mural Cell-β3-Integrin Regulated Crosstalk with Tumor Cells

Enhanced blood vessel (BV) formation is thought to drive tumor growth through elevated nutrient delivery. However, this observation has overlooked potential roles for mural cells in directly affecting tumor growth independent of BV function. Here we provide clinical data correlating high percentages of mural-β3-integrin-negative tumor BVs with increased tumor sizes but no effect on BV numbers. Mural-β3-integrin loss also enhances tumor growth in implanted and autochthonous mouse tumor models with no detectable effects on BV numbers or function. At a molecular level, mural-cell β3-integrin loss enhances signaling via FAK-p-HGFR-p-Akt-p-p65, driving CXCL1, CCL2, and TIMP-1 production. In particular, mural-cell-derived CCL2 stimulates tumor cell MEK1-ERK1/2-ROCK2-dependent signaling and enhances tumor cell survival and tumor growth. Overall, our data indicate that mural cells can control tumor growth via paracrine signals regulated by β3-integrin, providing a previously unrecognized mechanism of cancer growth control.

The significance of tumor cells-derived MFG-E8 in tumor growth of angiosarcoma

BackgroundPrevious studies have indicated that MFG-E8 enhances tumor cell survival, invasion and angiogenesis. However, the role of MFG-E8 in angiosarcoma (AS) has not been clarified. ObjectiveObjective was to elucidate the mechanism of the regulation by MFG-E8 in AS and the association between MFG-E8 and clinicopathological features of AS. MethodsThe effects of the depletion of MFG-E8 by siRNA on tube formation, migration and proliferation in murine AS cells were examined. The effect of administration of anti-MFG-E8 antibody (Ab) on tumor growth of AS in mice was examined. The associations of MFG-E8 expression and clinicopathological features of human AS were assessed. ResultsThe expressions of MFG-E8 in murine and human AS cells were significantly higher than those in melanoma cells, macrophages and endothelial cells. Depletion of MFG-E8 in murine AS cells by siRNA significantly inhibited the formation of capillary-like structures and migration, but not proliferation. Administration of anti-MFG-E8 Ab significantly inhibited tumor growth and decreased the number of tumor-associated macrophages (TAMs) in AS tumors. Tumor size and the number of TAMs in human AS with high expression of MFG-E8 were significantly increased compared to those of AS with low expression of MFG-E8. Progression-free survival and overall survival time of the patients of AS with high expression of MFG-E8 were significantly shorter than those of AS with low expression of MFG-E8. ConclusionsAS-derived MFG-E8 might enhance tumor growth via angiogenesis and the induction of TAMs in autocrine/paracrine manner, and administration of anti-MFG-E8 Ab could be a therapeutic potential for AS.

4-1BB-Costimulated CAR-Mediated Non-Canonical NF-Kb Signaling Enhances CAR T Cell Survival and Suppresses Bim Expression

Chimeric Antigen Receptor (CAR) T cell therapy induces deep and durable responses in a large percentage of patients with B-cell malignancies. These responses often correlate with CAR T cell persistence in patients. The first two FDA-approved CAR-T cell therapies employ 2nd generation CARs that use different costimulatory domains derived from either CD28 or 4-1BB. Data from pre-clinical studies as well as clinical trials suggest that 4-1BB CAR (BBz) T cells persist longer than CD28 CAR (28z) T cells.One signal associated with cellular survival and activated by endogenous 4-1BB, but not CD28, is the non-canonical NF-kB (ncNF-kB) pathway. NcNF-kB is required for memory T cell persistence and enhances tumor cell survival by suppressing pro-apoptotic gene transcription. Therefore, we hypothesize that the BBz, but not the 28z CAR, activates ncNF-kB signaling, which promotes CAR T cell persistence by suppressing pro-apoptotic gene expression.Using primary human T cells isolated from the apheresis products of anonymous healthy donors, we generated 28z or BBz T cells by lentiviral transduction following activation by CD3 and CD28. Induction of ncNF-kB signaling following CAR activation was assessed by western blot. NcNF-kB function was evaluated by concomitant expression of a dominant-negative mutant of NF-kB-inducing Kinase (dnNIK) to block the ncNF-kB pathway. In addition to pathway analysis by western blotting, T cell proliferation, immunophenotype and survival were assessed by bead-based counting via flow cytometry. To explore mechanisms affecting survival, pro- and anti-apoptotic gene expression was analyzed by qPCR and western blot over three weeks following restimulation through the CAR.Following CAR activation, ncNF-kB signaling was detected in BBz but not 28z T cell lysates. Control mRFP BBz T cells expanded approximately 10 fold more than BBz T cells coexpressing dnNIK. DnNIK-expressing BBz T cells exhibited higher rates of cell death contributing to the observed differences apparent in ex vivo expansion. This cell death was associated with a 2 fold increase in the message and nearly 3 fold increase in the expression of the pro-apoptotic protein, Bim, in the dnNIK BBz T cells relative to control. In contrast, dnNIK 28z T cells had no appreciable difference in proliferation or survival compared with control.Therefore, BBz, but not 28z signaling activates the ncNF-kB pathway, which protects BBz T cells from cell death likely by restricting the expression of the pro-apoptotic protein, Bim. DisclosuresMilone:Novartis: Patents & Royalties.

Nuclear factor 90 promotes angiogenesis by regulating HIF-1\u03b1/VEGF-A expression through the PI3K/Akt signaling pathway in human cervical cancer

Vascular endothelial growth factor A (VEGF-A), a fundamental component of angiogenesis, provides nutrients and oxygen to solid tumors, and enhances tumor cell survival, invasion, and migration. Nuclear factor 90 (NF90), a double-stranded RNA-binding protein, is strongly expressed in several human cancers, promotes tumor growth by reducing apoptosis, and increasing cell cycle process. The mechanisms by which cervical cancer cells inducing VEGF-A expression and angiogenesis upon NF90 upregulation remain to be fully established. We demonstrated that NF90 is upregulated in human cervical cancer specimens and the expression of NF90 is paralleled with that of VEGF-A under hypoxia. The expressions of hypoxia inducible factor-1α (HIF-1α) and VEGF-A are downregulated upon NF90 knockdown, which can be rescued by ectopic expression of NF90. Suppression of NF90 decreases the tube formation and cell migration of HUVECs. Moreover, the PI3K/Akt signaling pathway participates in the regulation. Knockdown of NF90 also reduces the tumor growth and angiogenesis of cervical cancer cell line in the mouse xenograft model. Taken together, suppression of NF90 in cervical cancer cell lines can decrease VEGF-A expression, inhibit angiogenesis, and reduce tumorigenic capacity in vivo.

Intrinsic apoptotic pathway activation increases response to anti-estrogens in luminal breast cancers

Estrogen receptor-α positive (ERα+) breast cancer accounts for approximately 70–80% of the nearly 25,0000 new cases of breast cancer diagnosed in the US each year. Endocrine-targeted therapies (those that block ERα activity) serve as the first line of treatment in most cases. Despite the proven benefit of endocrine therapies, however, ERα+ breast tumors can develop resistance to endocrine therapy, causing disease progression or relapse, particularly in the metastatic setting. Anti-apoptotic Bcl-2 family proteins enhance breast tumor cell survival, often promoting resistance to targeted therapies, including endocrine therapies. Herein, we investigated whether blockade of anti-apoptotic Bcl-2 family proteins could sensitize luminal breast cancers to anti-estrogen treatment. We used long-term estrogen deprivation (LTED) of human ERα+ breast cancer cell lines, an established model of sustained treatment with and acquired resistance to aromatase inhibitors (AIs), in combination with Bcl-2/Bcl-xL inhibition (ABT-263), finding that ABT-263 induced only limited tumor cell killing in LTED-selected cells in culture and in vivo. Interestingly, expression and activity of the Bcl-2-related factor Mcl-1 was increased in LTED cells. Genetic Mcl-1 ablation induced apoptosis in LTED-selected cells, and potently increased their sensitivity to ABT-263. Increased expression and activity of Mcl-1 was similarly seen in clinical breast tumor specimens treated with AI + the selective estrogen receptor downregulator fulvestrant. Delivery of Mcl-1 siRNA loaded into polymeric nanoparticles (MCL1 si-NPs) decreased Mcl-1 expression in LTED-selected and fulvestrant-treated cells, increasing tumor cell death and blocking tumor cell growth. These findings suggest that Mcl-1 upregulation in response to anti-estrogen treatment enhances tumor cell survival, decreasing response to therapeutic treatments. Therefore, strategies blocking Mcl-1 expression or activity used in combination with endocrine therapies would enhance tumor cell death.

Abstract 4713: Deubiquitination and stabilization of programmed cell death-ligand 1 by CSN5

Abstract Chronic inflammation in cancer is often associated with disease aggressiveness. Pro-inflammatory cytokines produced in the tumor microenvironment lead to eradication of antitumor immunity and enhanced tumor cell survival. In the current study, we identified TNFα as a major factor triggering cancer cell immunosuppression against T cell surveillance via stabilization of programmed cell death-ligand 1 (PD-L1). We demonstrated that COP9 signalosome 5 (CSN5), induced by NF-κB p65, is required for TNFα-mediated PD-L1 stabilization in cancer cells. CSN5 inhibits the ubiquitination and degradation of PD-L1. The role of CSN5 in modulating PD-L1 stabilization prompted us to use CSN5 inhibitor, curcumin, to show that it could destabilize PD-L1. Curcumin reduced CSN5 activity to attenuate TNFα-mediated PD-L1 stabilization and enhanced anti-tumor immunity. Preclinical data demonstrated inhibition of CSN5 sensitized cancer cells to anti-CTLA4 therapy, suggesting CSN5 inhibitor may be a useful adjuvant to enhance immune-based therapies. Note: This abstract was not presented at the meeting. Citation Format: Seung-Oe Lim, Chia-Wei Li, Mien-Chie Hung. Deubiquitination and stabilization of programmed cell death-ligand 1 by CSN5 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4713. doi:10.1158/1538-7445.AM2017-4713

ID2 promotes survival of glioblastoma cells during metabolic stress by regulating mitochondrial function

Tumor cells proliferate in cellular environments characterized by a lack of optimal tissue organization resulting oftentimes in compromised cellular metabolism affecting nutrition, respiration, and energetics. The response of tumor cells to adverse environmental conditions is a key feature affecting their pathogenicity. We found that inhibitor of DNA binding 2 (ID2) expression levels significantly correlate with the ability of glioblastoma (GBM)-derived cell lines to survive glucose deprivation. ID2 suppressed mitochondrial oxidative respiration and mitochondrial ATP production by regulating the function of mitochondrial electron transport chain (mETC) complexes, resulting in reduced superoxide and reactive oxygen species (ROS) production from mitochondria. ID2 suppression of ROS production reduced mitochondrial damage and enhanced tumor cell survival during glucose deprivation. Bioinformatics analysis of GBM gene expression data from The Cancer Genome Atlas (TCGA) database revealed that expression of ID2 mRNA is unique among ID gene family members in correlating with the expression of nuclear genes involved in mitochondrial energy metabolism and assembly of mETC. Our data indicate that the expression level of ID2 in GBM cells can predict the sensitivity of GBM-derived tumor cells to decreased glucose levels. Low levels of ID2 expression in human GBM tissues may identify a clinical group in which metabolic targeting of glycolytic pathways can be expected to have the greatest therapeutic efficacy.

Microfluidic isolation of platelet-covered circulating tumor cells.

The interplay between platelets and tumor cells is known to play important roles in metastasis by enhancing tumor cell survival, tumor-vascular interactions, and escape from immune surveillance. However, platelet-covered circulating tumor cells (CTC) are extremely difficult to isolate due to masking or downregulation of surface epitopes. Here we describe a microfluidic platform that takes advantage of the satellite platelets on the surface of these "stealth" CTCs as a ubiquitous surface marker for isolation. Compared to conventional CTC enrichment techniques which rely on known surface markers expressed by tumor cells, platelet-targeted isolation is generally applicable to CTCs of both epithelial and mesenchymal phenotypes. Our approach first depletes unbound, free platelets by means of hydrodynamic size-based sorting, followed by immunoaffinity-based capture of platelet-covered CTCs using a herringbone micromixing device. This method enabled the reliable isolation of CTCs from 66% of lung and 60% of breast cancer (both epithelial) patient samples, as well as in 83% of melanoma (mesenchymal) samples. Interestingly, we observed special populations of CTCs that were extensively covered by platelets, as well as CTC-leukocyte clusters. Because these cloaked CTCs often escape conventional positive and negative isolation mechanisms, further characterization of these cells may uncover important yet overlooked biological information in blood-borne metastasis and cancer immunology.

VHL missense mutations in the p53 binding domain show different effects on p53 signaling and HIFα degradation in clear cell renal cell carcinoma.

Clear cell Renal Cell Carcinoma (ccRCC) formation is connected to functional loss of the von Hippel-Lindau (VHL) gene. Recent data identified its gene product, pVHL, as a multifunctional adaptor protein which interacts with HIFα subunits but also with the tumor suppressor p53. p53 is hardly expressed and rarely mutated in most ccRCC. We showed that low and absent p53 expression correlated with the severity of VHL mutations in 262 analyzed ccRCC tissues. In contrast to nonsense and frameshift mutations which abrogate virtually all pVHL functions, missense mutations may rather influence one or few functions. Therefore, we focused on four VHL missense mutations, which affect the overlapping pVHL binding sites of p53 and Elongin C, by investigating their impact on HIFα degradation, p53 expression and signaling, as well as on cellular behavior using ccRCC cell lines and tissues. TP53 mRNA and its effector targets p21, Bax and Noxa, were altered both in engineered cell lines and in tumor tissues which carried the same missense mutations. Two of these mutations were not able to degrade HIFα whereas the remaining two mutations led to HIFα downregulation, suggesting the latter are p53 binding site-specific. The selected VHL missense mutations further enhanced tumor cell survival, but had no effects on cell proliferation. Whereas Sunitinib was able to efficiently reduce cell proliferation, Camptothecin was additionally able to increase apoptotic activity of the tumor cells. It is concluded that systematic characterization of the VHL mutation status may help optimizing targeted therapy for patients with metastatic ccRCC.