Methionine-producing tumor micro(be) environment fuels growth of solid tumors

BACKGROUND

Recent studies have uncovered the near-ubiquitous presence of microbes in solid tumors of diverse origins. Previous literature has shown the impact of specific bacterial species on the progression of cancer. We propose that local microbial dysbiosis enables certain cancer phenotypes through provisioning of essential metabolites directly to tumor cells.

METHODS

16S rDNA sequencing of 75 patient lung samples revealed the lung tumor microbiome specifically enriched for bacteria capable of producing methionine. Wild-type (WT) and methionine auxotrophic (metA mutant) E. coli cells were used to condition cell culture media and the proliferation of lung adenocarcinoma (LUAD) cells were measured using SYTO60 staining. Further, colony forming assay, Annexin V Staining, BrdU, AlamarBlue, western blot, qPCR, LINE microarray and subcutaneous injection with methionine modulated feed were used to analyze cellular proliferation, cell-cycle, cell death, methylation potential, and xenograft formation under methionine restriction. Moreover, C14-labeled glucose was used to illustrate the interplay between tumor cells and bacteria.

RESULTS/DISCUSSION

Our results show bacteria found locally within the tumor microenvironment are enriched for methionine synthetic pathways, while having reduced S-adenosylmethionine metabolizing pathways. As methionine is one of nine essential amino acids that mammals are unable to synthesize de novo, we investigated a potentially novel function for the microbiome, supplying essential nutrients, such as methionine, to cancer cells. We demonstrate that LUAD cells can utilize methionine generated by bacteria to rescue phenotypes that would otherwise be inhibited due to nutrient restriction. In addition to this, with WT and metA mutant E. coli, we saw a selective advantage for bacteria with an intact methionine synthetic pathway to survive under the conditions induced by LUAD cells. These results would suggest that there is a potential bi-directional cross-talk between the local microbiome and adjacent tumor cells. In this study, we focused on methionine as one of the critical molecules, but we also hypothesize that additional bacterial metabolites may also be utilized by LUAD. Indeed, our radiolabeling data suggest that other biomolecules are shared between cancer cells and bacteria. Thus, modulating the local microbiome may have an indirect effect on tumor development, progression, and metastasis.

Evaluation of 2-deoxy-2-[18F]fluoro glucaric acid (FGA) as a potential PET tracer for tumor necrosis

In this study, [18F]FGA was obtained by a one-step oxidation of [18F]FDG using sodium hypochlorite. The conversion from [18F]FDG to [18F]FGA was confirmed by HPLC to be over 95% using the optimal condition. A549-luciferase NSCLC xenografted mice was used for in vivo PET imaging. Prior to either saline or cisplatin treatment, there was no significant difference on tumor uptake of [18F]FGA in all mice, with an average uptake of (0.21 ± 0.16) %ID/g. After treatment, tumor uptake of [18F]FGA was not changed significantly for saline-treated mice, whereas the tumor uptake of [18F]FGA drastically increased for cisplatin-treated mice, with an average uptake of (1.63 ± 0.16) %ID/g. The ratio of tumor uptake between cisplatin-treated vs. saline-treated mice was 7.8 ± 0.2 within one week of treatment. PET imaging results were consistent with ex vivo biodistribution data. BLI showed significant light intensity suppression after treatment, indicating necrosis. Our data indicate that [18F]FGA uptake was related to tumor necrosis. [18F]FGA PET/CT imaging might be a useful tool to monitor treatment response to chemotherapy by imaging tumor necrosis.

Physical structure of constitutional isomers influences antiproliferation activity of thiosemicarbazone-alkylthiocarbamate copper complexes

A series of hybrid thiosemicarbazone-alkylthiocarbamate copper complexes with similar electronic environments but distinct physical structures have been prepared, characterized, and evaluated for antiproliferation activity. The complexes include the constitutional isomers (1-phenylpropane-1-imine-(O-ethylthiocarbamato)-2-one-(N-methylthiosemicarbazonato))copper(II) (CuL1) and (1-phenylpropane-1-one-(N-methylthiosemicarbazonato)-2-imine-(O-ethylthiocarbamato))copper(II) (CuL2) along with (1-propane-1-imine-(O-ethylthiocarbamato)-2-one-(N-methylthiosemicarbazonato))copper(II) (CuL3). Complexes CuL1 and CuL2 differ in the positions of the pendent thiosemicarbazone (TSC) and alkylthiocarbamate (ATC) moieties on the 1-phenylpropane backbone. Complex CuL3 employs a propane backbone with the TSC in the 2-position as in CuL1. The isomer pair CuL1 and CuL2 have equivalent electronic environments with indistinguishable CuII/I potentials (E1/2 = -0.86 V vs. ferrocenium/ferrocene) and electron paramagnetic resonance (EPR) spectra (g∥ = 2.26, g⊥ = 2.08). The electronic structure of CuL3 has a similar E1/2 of -0.84 V and identical EPR parameters to CuL1, 2. Single crystal X-ray diffraction studies confirm a consistent donor environment with no substantial variation in the CuN or CuS bond distances and angles between the complexes. The antiproliferation activities of the CuL1-3 were evaluated against the lung adenocarcinoma cell line (A549) and nonmalignant lung fibroblast cell line (IMR-90) using the MTT assay. CuL1 had the highest A549 activity (A549EC50 = 0.065 μM) and selectivity (IMR-90EC50/A549EC50 = 20). The constitutional isomer CuL2 displayed decreased A549 activity (0.18 μM) and selectivity (10.6). The complex CuL3 displayed activity (0.009 μM) similar to CuL1 but with a lack of selectivity (1.0). Cellular copper loading determined by ICP-MS was consistent with the activity and selectivity trends. The complexes CuL1-3 did not induce reactive oxygen species (ROS) generation.

UBQLN Family Members Regulate MYC in Lung Adenocarcinoma Cells

The ubiquilin family (UBQLN) of proteins consists of five closely related members (UBQLN1, UBQLN2, UBQLN3, UBQLN4, and UBQLNL) that have a high degree of similarity at the level of both amino acid and domain structure. The role of UBQLN1 and UBQLN2 in regulating processes involved in cancer progression and tumorigenesis is still not completely understood. MYC is an oncogene and is well known to play important roles in cancer progression and metastasis. Herein, we show that the loss of UBQLN1 and UBQLN2 causes increased cell viability, cell proliferation, cell migration, clonogenic potential, and cell cycle progression, which is associated with increased MYC expression. UBQLN1 and UBQLN2 interact with phosphorylated MYC and facilitate its degradation. The overexpression of UBQLN1 reverses the increased expression of MYC following the loss of UBQLN2. Further, we present evidence that decreasing MYC levels back to baseline can reverse phenotypes driven by the loss of UBQLN1 or UBQLN2. Finally, we show that loss of UBQLN1 drives tumorigenesis and lung metastasis in mice which are associated with an increase in the expression of MYC, proteins involved in cell cycle progression, and EMT. Taken together, our results suggest for the first time a novel role of UBQLN1 and UBQLN2 in regulating MYC in lung adenocarcinoma cells.

Mutant and curli-producing E. coli enhance the disease phenotype in a hSOD1-G93A mouse model of ALS

The gut microbiome is a potential non-genetic contributing factor for Amyotrophic Lateral Sclerosis. Differences in gut microbial communities have been detected between ALS subjects and healthy controls, including an increase in Escherichia coli in ALS subjects. E. coli and other gram-negative bacteria produce curli proteins, which are functional bacterial amyloids. We examined whether long-term curli overexposure in the gut can exacerbate the development and progression of ALS. We utilized the slow-developing hSOD1-G93A mouse model of ALS with their C57BL/6J WT littermate controls, including males and females, with a total of 91 animals. These mice were on a normal chow diet and fed curli-producing or curli-nonproducing (mutant) E. coli in applesauce (vehicle) 3 times/week, from 1 through 7 months of age. Male hSOD1 mice demonstrated gradual slowing in running speed month 4 onwards, while females exhibited no signs of locomotive impairment even at 7 months of age. Around the same time, male hSOD1 mice showed a gradual increase in frequency of peripheral CD19⁺ B cells. Among the male hSOD1 group, chronic gut exposure to curli-producing E. coli led to significant shifts in α- and β-diversities. Curli-exposed males showed suppression of immune responses in circulation, but an increase in markers of inflammation, autophagy and protein turnover in skeletal muscle. Some of these markers were also changed in mutant E. coli-exposed mice, including astrogliosis in the brainstem and demyelination in the lumbar spinal cord. Overall, chronic overexposure to a commensal bacteria like E. coli led to distant organ pathology in our model, without the presence of a leaky gut at 6 months. Mechanisms underlying gut-distant organ communication are of tremendous interest to all disciplines.

Lung cancer-kidney cross talk induces kidney injury, interstitial fibrosis, and enhances cisplatin-induced nephrotoxicity

Patients with cancer represent a unique patient population with increased susceptibility to kidney disease. Drug-induced acute kidney injury (AKI) in patients with cancer is a common problem. Cisplatin is a highly effective treatment used in many solid-organ cancers and causes AKI in 30% of patients, increasing the risk of chronic kidney disease development. Most preclinical cisplatin toxicity studies have been completed in mice without cancer. We believe that the physiology of patients with cancer is not adequately represented in preclinical models, and the objective of this study was to determine how lung cancer will alter the nephrotoxicity of cisplatin. A genetically engineered mouse model and a syngeneic xenograft model of lung cancer were used. Mice were divided into the following four groups: 1) noncancer/vehicle, 2) noncancer/cisplatin, 3) cancer/vehicle, and 4) cancer/cisplatin. Mice were administered cisplatin via intraperitoneal injection once a week for 4 wk. Animals were euthanized 72 h following their final cisplatin injection. Mice with lung cancer had increased renal toxicity, injury, and fibrosis following repeated low doses of cisplatin. In addition, lung cancer alone induced kidney injury and fibrosis in the kidney before cisplatin treatment. In conclusion, this is the first study that we are aware of that assesses the impact of cancer on the kidney in conjunction with the nephrotoxicity of cisplatin. We believe that cancer is providing the first hit to the kidney and the subsequent damage from repeated doses of cisplatin becomes unsurmountable, leading to AKI and progression to chronic kidney disease.NEW & NOTEWORTHY Patients with cancer have impaired kidney function and increased susceptibility to nephrotoxic agents. Cisplatin is a commonly used chemotherapeutic with nephrotoxicity as the dose-limiting side effect. Cisplatin nephrotoxicity is almost exclusively studied in mice without cancer. Our current preclinical models do not adequately represent the complexity of patients with cancer. This study demonstrates increased renal toxicity, injury, and fibrosis in mice with lung cancer, which is exacerbated with cisplatin treatment. These results highlight the necessity of using preclinical models that more accurately capture the altered physiology of patients with cancer treated with cisplatin.

Pharmacological inhibitors of autophagy have opposite effects in acute and chronic cisplatin-induced kidney injury

The nephrotoxicity of cisplatin remains a major hurdle in the field of oncology. Thirty percent of patients treated with cisplatin develop acute kidney injury, and all patients are at risk for long-term impacts on kidney function. There are currently no Federal Drug Administration-approved agents to prevent or treat cisplatin-induced kidney injury. The dosing regimen used in preclinical models of nephrotoxicity may impact the success of therapeutic candidates in clinical trials. Here, we demonstrated that pharmacological inhibitors of autophagy have opposite effects when used as interventions in two different models of cisplatin-induced kidney injury. Eight-week-old male C57BL/6 mice were treated with either one dose of 20 mg/kg cisplatin or weekly doses of 9 mg/kg cisplatin for 4 wk or until body weight loss exceeded 30%. Concurrently, mice were administered multiple doses of 60 mg/kg chloroquine or 15 mg/kg 3-methyladenine attempting to globally inhibit autophagy. Mice that received a single high dose of cisplatin had worsened kidney function, inflammation, and cell death with the addition of chloroquine. 3-Methlyadenine did not impact the development of acute kidney injury in this model. In contrast, mice that received repeated low doses of cisplatin showed improved kidney function, reduced inflammation, and reduced fibrosis when treated with either chloroquine or 3-methyladenine. This study highlights how therapeutic candidates can have drastically different effects on the development of cisplatin-induced kidney injury depending on the dosing model used. This emphasizes the importance of choosing the appropriate model of injury for preclinical studies.NEW & NOTEWORTHY This study examined how inhibition of autophagy has opposite effects on the development of acute and chronic kidney injury. Autophagy inhibition exacerbated the development of acute kidney injury following a single high dose of cisplatin but prevented the development of injury and fibrosis following repeated low doses of cisplatin.

Neutral ceramidase deficiency protects against cisplatin-induced acute kidney injury

Cisplatin is a commonly used chemotherapeutic for the treatment of many solid organ cancers; however, its effectiveness is limited by the development of acute kidney injury (AKI) in 30% of patients. AKI is driven by proximal tubule cell death, leading to rapid decline in renal function. It has previously been shown that sphingolipid metabolism plays a role in regulating many of the biological processes involved in cisplatin-induced AKI. For example, neutral ceramidase (nCDase) is an enzyme responsible for converting ceramide into sphingosine, which is then phosphorylated to become sphingosine-1-phosphate, and our lab previously demonstrated that nCDase knockout (nCDase-/-) in mouse embryonic fibroblasts led to resistance to nutrient and energy deprivation-induced cell death via upregulation of autophagic flux. In this study, we further characterized the role of nCDase in AKI by demonstrating that nCDase-/- mice are resistant to cisplatin-induced AKI. nCDase-/- mice display improved kidney function, reduced injury and structural damage, lower rates of apoptosis, and less ER stress compared to wild-type mice following cisplatin treatment. Although the mechanism of protection is still unknown, we propose that it could be mediated by increased autophagy, as chloroquine treatment resensitized nCDase-/- mice to AKI development. Taken together, we conclude that nCDase may represent a novel target to prevent cisplatin-induced nephrotoxicity.

Towards a molecular understanding of the overlapping and distinct roles of UBQLN1 and UBQLN2 in lung cancer progression and metastasis

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The Ubiquilin family of proteins (UBQLN) consists of five related proteins (UBQLN1-4 and UBQLNL).

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Herein, we showed that loss of UBQLN1 and/or UBQLN2 induces cellular processes involved in tumor progression and metastasis, including proliferation, clonogenic potential and migration in lung adenocarcinoma cells.

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Molecular, biochemical and RNAseq analyses in multiple cellular systems, identified overlapping and distinct gene sets and pathways that were altered following loss of UBQLN1 and/or UBQLN2.

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The present study, provide evidence that UBQLN1 and UBQLN2 perform similar, but distinct molecular functions in a variety of cell types.

The Ubiquilin family of proteins (UBQLN) consists of five related proteins (UBQLN1-4 and UBQLNL) that all contain ubiquitin-like (UBL) and ubiquitin-associated (UBA) domains. UBQLN1 and UBQLN2 are the most closely related and have been the most well-studied, however their biochemical, biological and cellular functions are still not well understood. Previous studies from our lab reported that loss of UBQLN1 or UBQLN2 induces epithelial mesenchymal transition (EMT) in lung adenocarcinoma cells. Herein, we showed that loss of UBQLN1 and/or UBQLN2 induces cellular processes involved in tumor progression and metastasis, including proliferation, clonogenic potential and migration in lung adenocarcinoma cells. In fact, following simultaneous loss of both UBQLN1 and UBQLN2 many of these processes were further enhanced. To understand the molecular mechanisms by which UBQLN1 and UBQLN2 loss could be additive, we performed molecular, biochemical and RNAseq analyses in multiple cellular systems. We identified overlapping and distinct gene sets and pathways that were altered following loss of UBQLN1 and/or UBQLN2. We have also begun to define cell type specific gene regulation of UBQLN1 and UBQLN2, as well as understand how loss of either gene can alter differentiation of normal cells. The data presented here demonstrate that UBQLN1 and UBQLN2 perform similar, but distinct molecular functions in a variety of cell types.

F4/80hi Resident Macrophages Contribute to Cisplatin-Induced Renal Fibrosis

Background

Cisplatin-induced kidney injury remains a major obstacle in utilizing cisplatin as a chemotherapeutic for solid-organ cancers. Thirty percent of patients treated with cisplatin develop acute kidney injury (AKI), and even patients who do not develop AKI are at risk for long-term declines in kidney function and development of chronic kidney disease (CKD). Modeling cisplatin-induced kidney injury in mice has revealed that repeated low doses of cisplatin lead to development of kidney fibrosis. This model can be used to examine AKI-to-CKD transition processes. Macrophages play a role in some of these processes, including immune response, wound healing, and tissue remodeling. Depleting macrophage populations in the kidney reduced fibrosis development in other models of renal fibrosis.

Methods

We used either C57BL/6 mice with a Ccr2 genetic knockout or liposome encapsulated clodronate (Clodrosome) to deplete macrophage populations during repeated 9 mg/kg cisplatin treatments. We assessed how immune cell populations were altered in the blood and kidney of these mice and how these alterations affected development of renal fibrosis and kidney injury.

Results

We found that Clodrosome treatment decreased collagen deposition, myofibroblast accumulation, and inflammatory cytokine production, whereas Ccr2 genetic knockout had no effect on these markers after cisplatin treatment. Additionally, Ccr2^-/- mice had decreased levels of F4/80^lo infiltrating macrophages in the kidney after cisplatin treatments, but Clodrosome treatment depleted F4/80^hi resident and CD206⁺ M2 macrophages.

Conclusions

These data suggest that Clodrosome depletion of F4/80^hi and M2 macrophages in the kidney attenuates development of renal fibrosis after repeated low doses of cisplatin.

Deletion of arylamine N-acetyltransferase 1 in MDA-MB-231 human breast cancer cells reduces primary and secondary tumor growth in vivo with no significant effects on metastasis

Arylamine N-acetyltransferase 1 (NAT1) is frequently upregulated in breast cancer. Previous studies showed that inhibition or depletion of NAT1 in breast cancer cells diminishes anchorage-independent growth in culture, suggesting that NAT1 contributes to breast cancer growth and metastasis. To further investigate the contribution of NAT1 to growth and cell invasive/migratory behavior, we subjected parental and NAT1 knockout (KO) breast cancer cell lines (MDA-MB-231, MCF-7, and ZR-75-1) to multiple assays. The rate of cell growth in suspension was not consistently decreased in NAT1 KO cells across the cell lines tested. Similarly, cell migration and invasion assays failed to produce reproducible differences between the parental and NAT1 KO cells. To overcome the limitations of in vitro assays, we tested parental and NAT1 KO cells in vivo in a xenograft model by injecting cells into the flank of immunocompromised mice. NAT1 KO MDA-MB-231 cells produced primary tumors smaller than those formed by parental cells, which was contributed by an increased rate of apoptosis in KO cells. The frequency of lung metastasis, however, was not altered in NAT1 KO cells. When the primary tumors of the parental and NAT1 KO cells were allowed to grow to a pre-determined size or delivered directly via tail vein, the number and size of metastatic foci in the lung did not differ between the parental and NAT1 KO cells. In conclusion, NAT1 contributes to primary and secondary tumor growth in vivo in MDA-MB-231 breast cancer cells but does not appear to affect its metastatic potential.

UBR-box containing protein, UBR5, is over-expressed in human lung adenocarcinoma and is a potential therapeutic target

Background

N-end rule ubiquitination pathway is known to be disrupted in many diseases, including cancer. UBR5, an E3 ubiquitin ligase, is mutated and/or overexpressed in human lung cancer cells suggesting its pathological role in cancer.

Methods

We determined expression of UBR5 protein in multiple lung cancer cell lines and human patient samples. Using immunoprecipitation followed by mass spectrometry we determined the UBR5 interacting proteins. The impact of loss of UBR5 for lung adenocarcinoma cell lines was analyzed using cell viability, clonogenic assays and in vivo xenograft models in nude mice. Additional Western blot analysis was performed to assess the loss of UBR5 on downstream signaling. Statistical analysis was done by one-way ANOVA for in vitro studies and Wilcoxon paired t-test for in vivo tumor volumes.

Results

We show variability of UBR5 expression levels in lung adenocarcinoma cell lines and in primary human patient samples. To gain better insight into the role that UBR5 may play in lung cancer progression we performed unbiased interactome analyses for UBR5. Data indicate that UBR5 has a wide range of interacting protein partners that are known to be involved in critical cellular processes such as DNA damage, proliferation and cell cycle regulation. We have demonstrated that shRNA-mediated loss of UBR5 decreases cell viability and clonogenic potential of lung adenocarcinoma cell lines. In addition, we found decreased levels of activated AKT signaling after the loss of UBR5 in lung adenocarcinoma cell lines using multiple means of UBR5 knockdown/knockout. Furthermore, we demonstrated that loss of UBR5 in lung adenocarcinoma cells results in significant reduction of tumor volume in nude mice.

Conclusions

These findings demonstrate that deregulation of the N-end rule ubiquitination pathway plays a crucial role in the etiology of some human cancers, and blocking this pathway via UBR5-specific inhibitors, may represent a unique therapeutic target for human cancers.

C57BL/6 mice require a higher dose of cisplatin to induce renal fibrosis and CCL2 correlates with cisplatin-induced kidney injury

C57BL/6 mice are one of the most commonly used mouse strains in research, especially in kidney injury studies. However, C57BL/6 mice are resistant to chronic kidney disease-associated pathologies, particularly the development of glomerulosclerosis and interstitial fibrosis. Our laboratory and others developed a more clinically relevant dosing regimen of cisplatin (7 mg/kg cisplatin once a week for 4 wk and mice euthanized at day 24) that leads to the development of progressive kidney fibrosis in FVB/n mice. However, we found that treating C57BL/6 mice with this same dosing regimen does not result in kidney fibrosis. In this study, we demonstrated that increasing the dose of cisplatin to 9 mg/kg once a week for 4 wk is sufficient to consistently induce fibrosis in C57BL/6 mice while maintaining animal survival. In addition, we present that cohorts of C57BL/6 mice purchased from Jackson 1 yr apart and mice bred in-house display variability in renal outcomes following repeated low-dose cisplatin treatment. Indepth analyses of this intra-animal variability revealed C-C motif chemokine ligand 2 as a marker of cisplatin-induced kidney injury through correlation studies. In addition, significant immune cell infiltration was observed in the kidney after four doses of 9 mg/kg cisplatin, contrary to what has been previously reported. These results indicate that multiple strains of mice can be used with our repeated low-dose cisplatin model with dose optimization. Results also indicate that littermate control mice should be used with this model to account for population variability.

Ubiquilin proteins regulate EGFR levels and activity in lung adenocarcinoma cells

Ubiquilin (UBQLN) proteins are involved in diverse cellular processes like endoplasmic reticulum-associated degradation, autophagy, apoptosis, and epithelial-to-mesenchymal transition. UBQLNs interact with a variety of substrates, including cell surface receptors, transcription factor regulators, proteasomal machinery proteins, and transmembrane proteins. In addition, previous work from our lab shows that UBQLN1 interacts with insulin-like growth factor receptor family members (IGF1R, IGF2R, and INSR) and this interaction regulates the activity and proteostasis of IGFR family members. We wondered whether UBQLN proteins could also bind and regulate additional receptor tyrosine kinases. Thus, we investigated a link between UBQLN and the oncogene epidermal growth factor receptor (EGFR) in lung adenocarcinoma cells. Loss of UBQLN1 occurs at high frequency in human lung cancer patient samples and we have shown that the loss of UBQLN1 is capable of altering processes involved in cell proliferation, migration, invasion, and epithelial-to-mesenchymal transition in lung adenocarcinoma cell lines. Here, we present data that loss of UBQLN1 resulted in increased turnover of total EGFR while increasing the relative amount of phosphorylated EGFR in lung adenocarcinoma cells, especially in the presence of its ligand EGF. Furthermore, the loss of UBQLN1 led to a more invasive cell phenotype as manifested by increased proliferation, migration, and speed of movement of these lung adenocarcinoma cells. Taken together, UBQLN1 regulates the expression and stability of EGFR in lung cancer cells.

Perturbation of Methionine/S-adenosylmethionine Metabolism as a Novel Vulnerability in MLL Rearranged Leukemia

Leukemias bearing mixed lineage leukemia (MLL) rearrangement (MLL-R) resulting in expression of oncogenic MLL fusion proteins (MLL-FPs) represent an especially aggressive disease subtype with the worst overall prognoses and chemotherapeutic response. MLL-R leukemias are uniquely dependent on the epigenetic function of the H3K79 methyltransferase DOT1L, which is misdirected by MLL-FPs activating gene expression, driving transformation and leukemogenesis. Given the functional necessity of these leukemias to maintain adequate methylation potential allowing aberrant activating histone methylation to proceed, driving leukemic gene expression, we investigated perturbation of methionine (Met)/S-adenosylmethionine (SAM) metabolism as a novel therapeutic paradigm for MLL-R leukemia. Disruption of Met/SAM metabolism, by either methionine deprivation or pharmacologic inhibition of downstream metabolism, reduced overall cellular methylation potential, reduced relative cell numbers, and induced apoptosis selectively in established MLL-AF4 cell lines or MLL-AF6-expressing patient blasts but not in BCR-ABL-driven K562 cells. Global histone methylation dynamics were altered, with a profound loss of requisite H3K79 methylation, indicating inhibition of DOT1L function. Relative occupancy of the repressive H3K27me3 modification was increased at the DOT1L promoter in MLL-R cells, and DOT1L mRNA and protein expression was reduced. Finally, pharmacologic inhibition of Met/SAM metabolism significantly prolonged survival in an advanced, clinically relevant patient–derived MLL-R leukemia xenograft model, in combination with cytotoxic induction chemotherapy. Our findings provide support for further investigation into the development of highly specific allosteric inhibitors of enzymatic mediators of Met/SAM metabolism or dietary manipulation of methionine levels. Such inhibitors may lead to enhanced treatment outcomes for MLL-R leukemia, along with cytotoxic chemotherapy or DOT1L inhibitors.

Computational/experimental evaluation of liver metastasis post hepatic injury: interactions with macrophages and transitional ECM

The complex interactions between subclinical changes to hepatic extracellular matrix (ECM) in response to injury and tumor-associated macrophage microenvironmental cues facilitating metastatic cell seeding remain poorly understood. This study implements a combined computational modeling and experimental approach to evaluate tumor growth following hepatic injury, focusing on ECM remodeling and interactions with local macrophages. Experiments were performed to determine ECM density and macrophage-associated cytokine levels. Effects of ECM remodeling along with macrophage polarization on tumor growth were evaluated via computational modeling. For primary or metastatic cells in co-culture with macrophages, TNF-α levels were 5× higher with M1 vs. M2 macrophages. Metastatic cell co-culture exhibited 10× higher TNF-α induction than with primary tumor cells. Although TGFβ1 induction was similar between both co-cultures, levels were slightly higher with primary cells in the presence of M1. Simulated metastatic tumors exhibited decreased growth compared to primary tumors, due to high local M1-induced cytotoxicity, even in a highly vascularized microenvironment. Experimental analysis combined with computational modeling may provide insight into interactions between ECM remodeling, macrophage polarization, and liver tumor growth.

De novo synthesis of serine and glycine fuels purine nucleotide biosynthesis in human lung cancer tissues

Nucleotide synthesis is essential to proliferating cells, but the preferred precursors for de novo biosynthesis are not defined in human cancer tissues. We have employed multiplexed stable isotope-resolved metabolomics to track the metabolism of [¹³C₆]glucose, D₂-glycine, [¹³C₂]glycine, and D₃-serine into purine nucleotides in freshly resected cancerous and matched noncancerous lung tissues from nonsmall cell lung cancer (NSCLC) patients, and we compared the metabolism with established NSCLC PC9 and A549 cell lines in vitro Surprisingly, [¹³C₆]glucose was the best carbon source for purine synthesis in human NSCLC tissues, in contrast to the noncancerous lung tissues from the same patient, which showed lower mitotic indices and MYC expression. We also observed that D₃-Ser was preferentially incorporated into purine rings over D₂-glycine in both tissues and cell lines. MYC suppression attenuated [¹³C₆]glucose, D₃-serine, and [¹³C₂]glycine incorporation into purines and reduced proliferation in PC9 but not in A549 cells. Using detailed kinetic modeling, we showed that the preferred use of glucose as a carbon source for purine ring synthesis in NSCLC tissues involves cytoplasmic activation/compartmentation of the glucose-to-serine pathway and enhanced reversed one-carbon fluxes that attenuate exogenous serine incorporation into purines. Our findings also indicate that the substrate for de novo nucleotide synthesis differs profoundly between cancer cell lines and fresh human lung cancer tissues; the latter preferred glucose to exogenous serine or glycine but not the former. This distinction in substrate utilization in purine synthesis in human cancer tissues should be considered when targeting one-carbon metabolism for cancer therapy.

Solution structure and functional investigation of human guanylate kinase reveals allosteric networking and a crucial role for the enzyme in cancer

Human guanylate kinase (hGMPK) is the only known enzyme responsible for cellular GDP production, making it essential for cellular viability and proliferation. Moreover, hGMPK has been assigned a critical role in metabolic activation of antiviral and antineoplastic nucleoside-analog prodrugs. Given that hGMPK is indispensable for producing the nucleotide building blocks of DNA, RNA, and cGMP and that cancer cells possess elevated GTP levels, it is surprising that a detailed structural and functional characterization of hGMPK is lacking. Here, we present the first high-resolution structure of hGMPK in the apo form, determined with NMR spectroscopy. The structure revealed that hGMPK consists of three distinct regions designated as the LID, GMP-binding (GMP-BD), and CORE domains and is in an open configuration that is nucleotide binding-competent. We also demonstrate that nonsynonymous single-nucleotide variants (nsSNVs) of the hGMPK CORE domain distant from the nucleotide-binding site of this domain modulate enzymatic activity without significantly affecting hGMPK's structure. Finally, we show that knocking down the hGMPK gene in lung adenocarcinoma cell lines decreases cellular viability, proliferation, and clonogenic potential while not altering the proliferation of immortalized, noncancerous human peripheral airway cells. Taken together, our results provide an important step toward establishing hGMPK as a potential biomolecular target, from both an orthosteric (ligand-binding sites) and allosteric (location of CORE domain-located nsSNVs) standpoint.

Moderate aging does not exacerbate cisplatin-induced kidney injury or fibrosis despite altered inflammatory cytokine expression and immune cell infiltration

Aging is a risk factor for certain forms of kidney injury due to normal physiological changes, but the role of aging in cisplatin-induced kidney injury is not well defined in humans or animal models of the disease. To improve on current knowledge in this field, we treated 8- and 40-wk-old FVB/n mice with one high dose of cisplatin as a model of acute kidney injury or with repeated low doses of cisplatin (7 mg/kg cisplatin once a week for 4 wk) as a clinically relevant model of chronic kidney disease to determine if aging exacerbates cisplatin-induced kidney injury. Levels of acute kidney injury were comparable in 8- and 40-wk-old mice. In 40-wk-old mice, fibrotic markers were elevated basally, but treatment with cisplatin did not exacerbate fibrosis. We concluded that this may be the result of a decreased inflammatory response in 40-wk-old cisplatin-treated mice compared with 8-wk-old mice. Despite a decreased inflammatory response, the level of immune cell infiltration was greater in 40-wk-old cisplatin-treated mice than 8-wk-old mice. Our data highlight the importance of examining age as a risk factor for cisplatin-induced kidney injury.

Comparative utility of NRG and NRGS mice for the study of normal hematopoiesis, leukemogenesis, and therapeutic response

Cell-line-derived xenografts (CDXs) or patient-derived xenografts (PDXs) in immune-deficient mice have revolutionized our understanding of normal and malignant human hematopoiesis. Transgenic approaches further improved in vivo hematological research, allowing the development of human-cytokine-producing mice, which show superior human cell engraftment. The most popular mouse strains used in research, the NOG (NOD.Cg-Prkdc^scid Il2rγ^tm1Sug/Jic) and the NSG (NOD/SCID-IL2Rγ^-/-, NOD.Cg-Prkdc^scidIl2rγ^tm1Wjl/SzJ) mouse, and their human-cytokine-producing (interleukin-3, granulocyte-macrophage colony-stimulating factor, and stem cell factor) counterparts (huNOG and NSGS), rely partly on a mutation in the DNA repair protein PRKDC, causing a severe combined immune deficiency (SCID) phenotype and rendering the mice less tolerant to DNA-damaging therapeutics, thereby limiting their usefulness in the investigation of novel acute myeloid leukemia (AML) therapeutics. NRG (NOD/RAG1/2^-/-IL2Rγ^-/-) mice show equivalent immune ablation through a defective recombination activation gene (RAG), leaving DNA damage repair intact, and human-cytokine-producing NRGS (NRG-SGM3) mice were generated, improving myeloid engraftment. Our findings indicate that unconditioned NRG and NRGS mice can harbor established AML CDXs and can tolerate aggressive induction chemotherapy at higher doses than NSG mice without overt toxicity. However, unconditioned NRGS mice developed less clinically relevant disease, with CDXs forming solid tumors throughout the body, whereas unconditioned NRG mice were incapable of efficiently supporting PDX or human hematopoietic stem cell engraftment. These findings emphasize the contextually dependent utility of each of these powerful new strains in the study of normal and malignant human hematopoiesis. Therefore, the choice of mouse strain cannot be random, but must be based on the experimental outcomes and questions to be addressed.

The Antiarrhythmic Drug, Amiodarone, Decreases AKT Activity and Sensitizes Human Acute Myeloid Leukemia Cells to Apoptosis by ABT-263

BACKGROUND

Successful treatment of leukemia requires new medications to combat drug resistance, but the development of novel therapies is an arduous and risky endeavor. Repurposing currently approved drugs or those already in clinical development to treat other indications is a more practical approach. Moreover, combinatorial therapeutics are often more efficacious than single agent therapeutics because the former can simultaneously target multiple pathways that mitigate tumor aggressiveness and induce cancer cell death.

MATERIAL AND METHODS

In this study, we combined the class III antiarrhythmic agent amiodarone and the BH3 mimetic ABT-263 based on data from a prior drug screen to assess the degree of apoptotic induction in 2 human leukemia cell lines.

RESULTS

The combination yielded statistically significant increases in apoptosis in both cell lines by downregulating AKT activity and increasing cleaved caspase-3.

CONCLUSIONS

Overall, our findings suggest that combining K⁺ channel blockers with prosurvival Bcl-2 family inhibitors is a promising therapeutic approach in treating leukemia.

Subclinical kidney injury induced by repeated cisplatin administration results in progressive chronic kidney disease

Cisplatin is used to treat many solid cancers, but its dose-limiting side effect is nephrotoxicity, causing acute kidney injury in 30% of patients. Previously, we have developed a mouse model that better recapitulates the cisplatin dosing regimen humans receive and found that repeated dosing of cisplatin induces interstitial renal fibrosis. Chronic kidney disease is progressive and is characterized by chronic inflammation, worsening interstitial fibrosis, development of glomerulosclerosis, and endothelial dysfunction. To determine if damage caused by repeated cisplatin dosing results in bona fide chronic kidney disease, mice were treated with our repeated dosing regimen and then aged for 6 mo. These mice had progressive, chronic inflammation and worsened interstitial fibrosis compared with mice euthanized after day 24. Mice aged for 6 mo developed glomerular pathologies, and endothelial dysfunction was persistent. Mice treated with only two doses of cisplatin had little inflammation or kidney damage. Thus repeated dosing of cisplatin causes long-term effects that are characteristic of chronic kidney disease. This translational mouse model of cisplatin injury may better represent the 70% of patients that do not develop clinical acute kidney injury and can be used to identify both biomarkers for early injury, as well as novel therapeutic targets for the prevention of cisplatin-induced chronic kidney disease.

Inhibiting glucosylceramide synthase exacerbates cisplatin-induced acute kidney injury

Acute kidney injury (AKI), resulting from chemotherapeutic agents such as cisplatin, remains an obstacle in the treatment of cancer. Cisplatin-induced AKI involves apoptotic and necrotic cell death, pathways regulated by sphingolipids such as ceramide and glucosylceramide. Results from this study indicate that C57BL/6J mice treated with cisplatin had increased ceramide and hexosylceramide levels in the renal cortex 72 h following cisplatin treatment. Pretreatment of mice with inhibitors of acid sphingomyelinase and de novo ceramide synthesis (amitriptyline and myriocin, respectively) prevented accumulation of ceramides and hexosylceramide in the renal cortex and protected from cisplatin-induced AKI. To determine the role of ceramide metabolism to hexosylceramides in kidney injury, we treated mice with a potent and highly specific inhibitor of glucosylceramide synthase, the enzyme responsible for catalyzing the glycosylation of ceramides to form glucosylceramides. Inhibition of glucosylceramide synthase attenuated the accumulation of the hexosylceramides and exacerbated ceramide accumulation in the renal cortex following treatment of mice with cisplatin. Increasing ceramides and decreasing glucosylceramides in the renal cortex sensitized mice to cisplatin-induced AKI according to markers of kidney function, kidney injury, inflammation, cell stress, and apoptosis. Under conditions of high ceramide generation, data suggest that metabolism of ceramides to glucosylceramides buffers kidney ceramides and helps attenuate kidney injury.-Dupre, T. V., M. A. Doll, P. P. Shah, C. N. Sharp, D. Siow, J. Megyesi, J. Shayman, A. Bielawska, J. Bielawski, L. J. Beverly, M. Hernandez-Corbacho, C. J. Clarke, A. J. Snider, R. G. Schnellmann, L. M. Obeid, Y. A. Hannun, and L. J. Siskind. Inhibiting glucosylceramide synthase exacerbates cisplatin-induced acute kidney injury. J. Lipid Res 2017. 58: 1439-1452.

The STI and UBA Domains of UBQLN1 Are Critical Determinants of Substrate Interaction and Proteostasis

There are five Ubiquilin proteins (UBQLN1-4, UBQLN-L), which are evolutionarily conserved and structurally similar. UBQLN proteins have three functional domains: N-terminal ubiquitin-like domain (UBL), C-terminal ubiquitin-associated domain (UBA), and STI chaperone-like regions in the middle. Alterations in UBQLN1 gene have been detected in a variety of disorders ranging from Alzheimer's disease to cancer. UBQLN1 has been largely studied in neurodegenerative disorders in the context of protein quality control. Several studies have hypothesized that the UBA domain of UBQLN1 binds to poly-ubiquitin chains of substrate and shuttles it to the proteasome via its UBL domain for degradation. UBQLN1 either facilitates degradation (Ataxin3, EPS15) or stabilizes (PSEN1/2, BCLb) substrates it binds to. The signal that determines this fate is unknown and there is conflicting data to support the existing working model of UBQLN1. Using BCLb as a model substrate, we characterized UBQLN1-substrate interaction. We identified the first two STI domains of UBQLN1 as critical for binding to BCLb. Interaction of UBQLN1 with BCLb is independent of ubiquitination of BCLb, but interaction with ubiquitin via UBA domain is required for stabilization of BCLb. Similarly, we showed that UBQLN1 interacts with IGF1R and ESYT2 through the STI domains and stabilizes these proteins through its UBA domain. Interactions that are not dependent on STI domains, for example, UBL mediated interaction with PSMD4 and BAG6, do not appear to be stabilized by UBQLN1. We conclude that fate of substrates that UBQLN1 associates with, is interaction domain specific. J. Cell. Biochem. 118: 2261-2270, 2017. © 2017 Wiley Periodicals, Inc.

Common cytotoxic chemotherapeutics induce epithelial-mesenchymal transition (EMT) downstream of ER stress

Endoplasmic reticulum (ER) in eukaryotes is a main organelle involved in a wide variety of functions including calcium storage, lipid biosynthesis, protein folding and protein transport. Disruption of ER homeostasis leads to ER stress and activation of the unfolded protein response (UPR). We and others have previously found that ER stress induces EMT in different cellular systems. Induction of ER stress with chemical modulators of ER homeostasis was sufficient to activate an EMT-like state in all cellular systems tested. Here, we provide evidence for the first time demonstrating that ER stress induces EMT that is neither cancer cell specific nor cell-type specific. In addition, we observed that chemotherapeutic drugs commonly used to treat patients also activate ER stress that is concomitant with activation of an EMT-like state. Interestingly, we find that following removal of ER stress, partial EMT characteristics still persist indicating that ER stress induced EMT is a long-term effect. Induction of mesenchymal characteristics, following chemotherapeutics treatment may be involved in providing cancer stemness and invasiveness in the cellular system. Interestingly, we find that mice treated with cisplatin have elevated level of ER stress and EMT markers in multiple tissues including lung, liver and kidneys. Furthermore, increased ER stress, as demonstrated by increased Bip, Chop, PDI, Ero1α and IRE1, and EMT, as demonstrated by increased Vimentin and Snail, is a hallmark of primary lung adenocarcinoma samples from patients. These observations have potential clinical relevance because overexpression of ER stress and EMT markers might contribute to chemoresistance and poor survival of lung adenocarcinoma patients.

MIR155 Regulation of Ubiquilin1 and Ubiquilin2: Implications in Cellular Protection and Tumorigenesis

Ubiquilin (UBQLN) proteins are adaptors thought to link ubiquitinated proteins to the proteasome. However, our lab has recently reported a previously unappreciated role for loss of UBQLN in lung cancer progression. In fact, UBQLN genes are lost in over 50% of lung cancer samples examined. However, a reason for the loss of UBQLN has not been proposed, nor has a selective pressure that could lead to deletion of UBQLN been reported. Diesel Exhaust Particles (DEP) are a major concern in the large cities of developing nations and DEP exposed populations are at an increased risk of developing a number of illnesses, including lung cancer. A connection between DEP and UBQLN has never been examined. In the present study, we determined the effect of DEP on lung cell lines and were interested to determine if UBQLN proteins could potentially play a protective role following treatment with DEP. Interestingly, we found that DEP treated cells have increased expression of UBQLN proteins. In fact, over-expression of UBQLN was capable of protecting cells from DEP toxicity. To investigate the mechanism by which DEP leads to increased UBQLN protein levels, we identified and interrogated microRNAs that were predicted to regulate UBQLN mRNA. We found that DEP decreases the oncogenic microRNA, MIR155. Further, we showed that MIR155 regulates the mRNA of UBQLN1 and UBQLN2 in cells, such that increased MIR155 expression increased cell invasion, migration, wound formation and clonogenicity in UBQLN-loss dependent manner. This is the first report of an environmental carcinogen regulating expression of UBQLN proteins. We show that exposure of cells to DEP causes an increase in UBQLN levels and that MIR155 regulates mRNA of UBQLN. Thus, we propose that DEP-induced repression of MIR155 leads to increased UBQLN levels, which in turn may be a selective pressure on lung cells to lose UBQLN1.

Sphingolipids and mitochondrial apoptosis

The sphingolipid family of lipids modulate several cellular processes, including proliferation, cell cycle regulation, inflammatory signaling pathways, and cell death. Several members of the sphingolipid pathway have opposing functions and thus imbalances in sphingolipid metabolism result in deregulated cellular processes, which cause or contribute to diseases and disorders in humans. A key cellular process regulated by sphingolipids is apoptosis, or programmed cell death. Sphingolipids play an important role in both extrinsic and intrinsic apoptotic pathways depending on the stimuli, cell type and cellular response to the stress. During mitochondrial-mediated apoptosis, multiple pathways converge on mitochondria and induce mitochondrial outer membrane permeabilization (MOMP). MOMP results in the release of intermembrane space proteins such as cytochrome c and Apaf1 into the cytosol where they activate the caspases and DNases that execute cell death. The precise molecular components of the pore(s) responsible for MOMP are unknown, but sphingolipids are thought to play a role. Here, we review evidence for a role of sphingolipids in the induction of mitochondrial-mediated apoptosis with a focus on potential underlying molecular mechanisms by which altered sphingolipid metabolism indirectly or directly induce MOMP. Data available on these mechanisms is reviewed, and the focus and limitations of previous and current studies are discussed to present important unanswered questions and potential future directions.

Loss of neutral ceramidase protects cells from nutrient- and energy -deprivation-induced cell death

Sphingolipids are a family of lipids that regulate the cell cycle, differentiation and cell death. Sphingolipids are known to play a role in the induction of apoptosis, but a role for these lipids in necroptosis is largely unknown. Necroptosis is a programmed form of cell death that, unlike apoptosis, does not require ATP. Necroptosis can be induced under a variety of conditions, including nutrient deprivation and plays a major role in ischaemia/reperfusion injury to organs. Sphingolipids play a role in ischaemia/reperfusion injury in several organs. Thus, we hypothesized that sphingolipids mediate nutrient-deprivation-induced necroptosis. To address this, we utilized mouse embryonic fibroblast (MEFs) treated with 2-deoxyglucose (2DG) and antimycin A (AA) to inhibit glycolysis and mitochondrial electron transport. 2DG/AA treatment of MEFs induced necroptosis as it was receptor- interacting protein (RIP)-1/3 kinase-dependent and caspase-independent. Ceramides, sphingosine (Sph) and sphingosine 1-phosphate (S1P) were increased following 2DG/AA treatment. Cells lacking neutral ceramidase (nCDase(-/-)) were protected from 2DG/AA. Although nCDase(-/-) cells generated ceramides following 2DG/AA treatment, they did not generate Sph or S1P. This protection was stimulus-independent as nCDase(-/-) cells were also protected from endoplasmic reticulum (ER) stressors [tunicamycin (TN) or thapsigargin (TG)]. nCDase(-/-) MEFs had higher autophagic flux and mitophagy than wild-type (WT) MEFs and inhibition of autophagy sensitized them to necroptosis. These data indicate that loss of nCDase protects cells from nutrient- deprivation-induced necroptosis via autophagy, and clearance of damaged mitochondria. Results suggest that nCDase is a mediator of necroptosis and might be a novel therapeutic target for protection from ischaemic injury.

Murine Stem Cell-Based Retrovirus Production for Marking Primary Mouse Mammary Cells for Metastasis Studies

Since the introduction of retroviral vector technology, permanent genetic marking of cells has considerably contributed to the understanding of different physiological and disease processes in vivo. Recent marking strategies aim to elucidate the contribution of cells on the clonal level, and the advent of fluorescent proteins has opened new avenues for the in vivo analysis of gene-marked cells. Gene-modified cells are easily identifiable (e.g., via the introduced fluorescent protein) within whole organ structures, allowing one to measure the contribution of transduced cells to malignant outgrowth. In our laboratory, we use the tetracycline-inducible system to study oncogene cooperation in metastatic progression. We use bicistronic retroviruses expressing the tetracycline transactivator (tTA) and the candidate gene (MIT-gene) or the tTA alone (MIT-Rx) to infect primary mammary cells from mice harboring tetracycline-inducible transgenes. This allows for constitutive expression of the candidate gene and tTA-dependent expression of the inducible oncogene. We also use MIG-based vectors, which allow for constitutive expression of the candidate gene and a green fluorescent protein. Here we describe how to produce retroviral particles carrying both MIT- and MIG-based vectors. Because of the fragility of the retroviral envelope, we do not attempt to concentrate the virus, and we directly use packaging cell media to infect primary epithelial cells (either normal or tumor). Infected cells can be transplanted into recipient mice to investigate metastatic colonization.

Glucose availability and glycolytic metabolism dictate glycosphingolipid levels

Cancer therapeutics has seen an emergence and re-emergence of two metabolic fields in recent years, those of bioactive sphingolipids and glycolytic metabolism. Anaerobic glycolysis and its implications in cancer have been at the forefront of cancer research for over 90 years. More recently, the role of sphingolipids in cancer cell metabolism has gained recognition, notably ceramide's essential role in programmed cell death and the role of the glucosylceramide synthase (GCS) in chemotherapeutic resistance. Despite this knowledge, a direct link between these two fields has yet to be definitively drawn. Herein, we show that in a model of highly glycolytic cells, generation of the glycosphingolipid (GSL) glucosylceramide (GlcCer) by GCS was elevated in response to increased glucose availability, while glucose deprivation diminished GSL levels. This effect was likely substrate dependent, independent of both GCS levels and activity. Conversely, leukemia cells with elevated GSLs showed a significant change in GCS activity, but no change in glucose uptake or GCS expression. In a leukemia cell line with elevated GlcCer, treatment with inhibitors of glycolysis or the pentose phosphate pathway (PPP) significantly decreased GlcCer levels. When combined with pre-clinical inhibitor ABT-263, this effect was augmented and production of pro-apoptotic sphingolipid ceramide increased. Taken together, we have shown that there exists a definitive link between glucose metabolism and GSL production, laying the groundwork for connecting two distinct yet essential metabolic fields in cancer research. Furthermore, we have proposed a novel combination therapeutic option targeting two metabolic vulnerabilities for the treatment of leukemia.

Repeated administration of low-dose cisplatin in mice induces fibrosis

Cisplatin, a chemotherapeutic used for the treatment of solid cancers, has nephrotoxic side effects leading to acute kidney injury (AKI). Cisplatin cannot be given to patients that have comorbidities that predispose them to an increased risk for AKI. Even without these comorbidities, 30% of patients administered cisplatin will develop kidney injury, requiring the oncologist to withhold or reduce the next dose, leading to a less effective therapeutic regimen. Although recovery can occur after one episode of cisplatin-induced AKI, longitudinal studies have indicated that multiple episodes of AKI lead to the development of chronic kidney disease, an irreversible disease with no current treatment. The standard mouse model of cisplatin-induced AKI consists of one high dose of cisplatin (>20 mg/kg) that is lethal to the animal 3 days later. This model does not accurately reflect the dosing regimen patients receive nor does it allow for the long-term study of kidney function and biology. We have developed a repeated dosing model whereby cisplatin is given once a week for 4 wk. Comparison of the repeated dosing model with the standard dosing model demonstrated that inflammatory cytokines and chemokines were induced in the repeated dosing model, but levels of cell death were lower in the repeated dosing model. The repeated dosing model had increased levels of fibrotic markers (fibronectin, transforming growth factor-β, and α-smooth muscle actin) and interstitial fibrosis. These data indicate that the repeated dosing model can be used to study the AKI to chronic kidney disease progression as well as the mechanisms of this progression.

Suramin protects from cisplatin-induced acute kidney injury

Cisplatin, a commonly used cancer chemotherapeutic, has a dose-limiting side effect of nephrotoxicity. Approximately 30% of patients administered cisplatin suffer from kidney injury, and there are limited treatment options for the treatment of cisplatin-induced kidney injury. Suramin, which is Federal Drug Administration-approved for the treatment of trypanosomiasis, improves kidney function after various forms of kidney injury in rodent models. We hypothesized that suramin would attenuate cisplatin-induced kidney injury. Suramin treatment before cisplatin administration reduced cisplatin-induced decreases in kidney function and injury. Furthermore, suramin attenuated cisplatin-induced expression of inflammatory cytokines and chemokines, endoplasmic reticulum stress, and apoptosis in the kidney cortex. Treatment of mice with suramin 24 h after cisplatin also improved kidney function, suggesting that the mechanism of protection is not by inhibition of tubular cisplatin uptake or its metabolism to nephrotoxic species. If suramin is to be used in the context of cancer, then it cannot prevent cisplatin-induced cytotoxicity of cancer cells. Suramin did not alter the dose-response curve of cisplatin in lung adenocarcinoma cells in vitro. In addition, suramin pretreatment of mice harboring lung adenocarcinomas did not alter the initial cytotoxic effects of cisplatin (DNA damage and apoptosis) on tumor cells. These results provide evidence that suramin has potential as a renoprotective agent for the treatment/prevention of cisplatin-induced acute kidney injury and justify future long-term preclinical studies using cotreatment of suramin and cisplatin in mouse models of cancer.

The PIM family of oncoproteins: small kinases with huge implications in myeloid leukemogenesis and as therapeutic targets

PIM kinases are a family of serine/threonine kinases involved in cell survival and proliferation. There is significant structural similarity between the three PIM kinases (PIM1, PIM2 and PIM3) and few amino acid differences. Although, several studies have specifically monitored the role of PIM1 in tumorigenesis, much less is known about PIM2 and PIM3. Therefore, in this study we have used in vitro cell culture models and in vivo bone marrow infection/transplantation to assess the comparative signaling and oncogenic potential of each of the three PIM kinases. All three PIM kinases were able to protect FL5.12 cells from IL-3 withdrawal induced death. Interestingly, the downstream signaling cascades were indistinguishable between the three kinases. Transplantation of murine bone marrow co-expressing MYC and PIM1, PIM2 or PIM3 caused rapid and uniformly lethal myeloid leukemia. De-induction of MYC 18 days following transplantation significantly increased the survival of mice, even with continual expression of PIM kinases. Alternatively, mice treated at the pre-leukemic stage with a PIM kinase inhibitor increased the lifespan of the mice, even with continual expression of the MYC transgene. These data demonstrate the role of PIM kinases in driving myeloid leukemia, and as candidate molecules for therapy against human malignancies.

Ubiquilin1 represses migration and epithelial-to-mesenchymal transition of human non-small cell lung cancer cells

Ubiquilin1 (UBQLN1) is a ubiquitin-like domain and a ubiquitin-associated domain containing protein that has been reported to be involved in shuttling proteins to the proteasome, especially during endoplasmic reticulum-associated protein degradation (ERAD). Thus, UBQLN1 function has been shown to be critical for combating a number of neurological disorders caused by protein aggregation, such as Amyotrophic lateral sclerosis (ALS), Alzheimer’s disease and Huntington’s disease. A role for UBQLN1 in regulating processes involved in tumorigenesis has not been demonstrated. Herein, we show that loss of UBQLN1 causes increased cell migration and invasion, actin cytoskeleton reorganization and induction of epithelial mesenchymal transition (EMT). Loss of UBQLN1 results in a significant decrease in the expression of epithelial markers including E-cadherin and claudin1, whereas expression of mesenchymal markers including Vimentin, Snail and ZEB1 are significantly elevated. Interestingly, we found that ZEB1 is required for induction of mesenchymal-like properties following loss of UBQLN1 and ZEB1 is capable of repressing expression of UBQLN1, suggesting a physiological, reciprocal regulation of EMT by UBQLN1 and ZEB1. Further, we find evidence for a role for UBQLN2 in also regulating EMT and cell migration. These observations have potential clinical relevance because the UBQLN1 gene is lost and under-expressed in a large percentage of human cancer cell lines and primary human lung cancer samples and recurrent mutations in both all five Ubiquilin family members have been identified in human lung cancers. Taken together, our results suggest for the first time a role for Ubiquilin family members in cancer biology.

Abstract A05: Ubiquilin1 represses migration and epithelial to mesenchymal transition of human non-small cell lung cancer cells

Ubiquilin1 (UBQLN1) is a ubiquitin-like domain and a ubiquitin-associated domain containing protein that has been reported to be involved in shuttling proteins to the proteasome, especially during endoplasmic reticulum-associated protein degradation (ERAD). Thus, UBQLN1 function has been shown to be critical for combating a number of neurological disorders caused by protein aggregation, such as Amyotrophic lateral sclerosis (ALS), Alzheimer's disease and Huntington's disease. A role for UBQLN1 in regulating processes involved in tumorigenesis has not been demonstrated. Herein, we show that loss of UBQLN1 causes increased cell migration and invasion, actin cytoskeleton reorganization and induction of epithelial mesenchymal transition (EMT). Loss of UBQLN1 results in a significant decrease in the expression of epithelial markers including E-cadherin and claudin1, whereas expression of mesenchymal markers including Vimentin, Snail and ZEB1 are significantly elevated. Interestingly, we found that ZEB1 is required for induction of mesenchymal-like properties following loss of UBQLN1 and ZEB1 is capable of repressing expression of UBQLN1, suggesting a physiological, reciprocal regulation of EMT by UBQLN1 and ZEB1. Furthermore, we observed that loss of UBQLN1 sensitizes lung cancer cells to treatment with cytotoxic drugs. These observations have potential clinical relevance because the UBQLN1 gene is lost and under-expressed in a large percentage of human cancer cell lines and primary human lung cancer samples. Taken together, our results suggest for the first time a role of UBQLN1 in the regulation of EMT and a potential role in cancer biology and in predictive cancer therapeutics.

Citation Format: Parag P. Shah, William W. Lockwood, Kumar Saurabh, Zimple Kurlawala, Sabine Waigel, Wolfgang Zacharias, Levi J. Beverly. Ubiquilin1 represses migration and epithelial to mesenchymal transition of human non-small cell lung cancer cells. [abstract]. In: Proceedings of the AACR-IASLC Joint Conference on Molecular Origins of Lung Cancer; 2014 Jan 6-9; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2014;20(2Suppl):Abstract nr A05.

Dissecting the in vivo leukemogenic potency of BCLxl

Overexpression of anti-apoptotic members of the BCL2 family has been found in all types of cancer. A member of the family, BCLxl (B-cell lymphoma extra-large), is known to be associated with the progression of leukemogenesis. In the present study, we focused on understanding the domains of BCLxl responsible for in vivo oncogenic potency. To this end, we utilized engineered BCLxl proteins with alternative transmembrane domains (TM) or chimeric BCLxl proteins containing domains from a less potent BCL2-like protein, BCLb. As expected, mice receiving MYC-only expressing bone marrow develop leukemia by 100 days, whereas co-expression of MYC with wild-type BCLxl led to aggressive myeloid leukemia with an average latency of ~25 days. Interestingly, mice injected with bone marrow co-expressing MYC and BCLxl targeted specifically to either mitochondria or ER also succumbed to leukemia with an average latency of ~25 days. Further, our study was extended to examine the role of the BH4 domain in driving potent leukemogenesis. Mice injected with bone marrow co-expressing MYC and BCLb succumb to leukemia in an average of ~55 days, but interestingly a BCLxl protein containing only the loop region of BCLb drove MYC-induced leukemogenesis with the same latency as wild-type BCLxl. These data suggest that the localization of exogenous BCLxl to either mitochondria or ER is not a steadfast dictator of in vivo oncogenic potency. Further, our findings suggest that the loop domain of BCLb and BCLxl is not responsible for dictating the in vivo leukemogeneic potency. This study provides further mechanistic details into the biochemical functions of BCLxl.

Targeting IRAK1 as a therapeutic approach for myelodysplastic syndrome

Myelodysplastic syndromes (MDSs) arise from a defective hematopoietic stem/progenitor cell. Consequently, there is an urgent need to develop targeted therapies capable of eliminating the MDS-initiating clones. We identified that IRAK1, an immune-modulating kinase, is overexpressed and hyperactivated in MDSs. MDS clones treated with a small molecule IRAK1 inhibitor (IRAK1/4-Inh) exhibited impaired expansion and increased apoptosis, which coincided with TRAF6/NF-κB inhibition. Suppression of IRAK1, either by RNAi or with IRAK1/4-Inh, is detrimental to MDS cells, while sparing normal CD34(+) cells. Based on an integrative gene expression analysis, we combined IRAK1 and BCL2 inhibitors and found that cotreatment more effectively eliminated MDS clones. In summary, these findings implicate IRAK1 as a drugable target in MDSs.

The novel ubiquitin ligase complex, SCF(Fbxw4), interacts with the COP9 signalosome in an F-box dependent manner, is mutated, lost and under-expressed in human cancers

Identification of novel proteins that can potentially contribute to carcinogenesis is a requisite venture. Herein, we report the first biochemical characterization of the novel F-box and WD40 containing protein, FBXW4. We have identified interacting protein partners and demonstrated that FBXW4 is part of a ubiquitin ligase complex. Furthermore, the Fbxw4 locus is a common site of proviral insertion in a variety of retroviral insertional mutagenesis murine cancer models and Fbxw4 mRNA is highly expressed in the involuting murine mammary gland. To begin to characterize the biochemical function of Fbxw4, we used proteomic analysis to demonstrate that Fbxw4 interacts with Skp1 (SKP1), Cullin1 (CUL1), Ring-box1 (RBX1) and all components of the COP9 signalosome. All of these interactions are dependent on an intact F-box domain of Fbxw4. Furthermore, Fbxw4 is capable of interacting with ubiquitinated proteins within cells in an F-box dependent manner. Finally, we demonstrate that FBXW4 is mutated, lost and under-expressed in a variety of human cancer cell lines and clinical patient samples. Importantly, expression of FBXW4 correlates with survival of patients with non-small cell lung cancer. Taken together, we suggest that FBXW4 may be a novel tumor suppressor that regulates important cellular processes.

Regulation of anti-apoptotic BCL2-proteins by non-canonical interactions: the next step forward or two steps back?

All aspects of cellular biology affect the process of regulated cell death, or apoptosis, and disruption of this process is a causative event in many diseases. Therefore, a comprehensive understanding of all pathways that regulate apoptosis would increase our knowledge of basic cellular functions, as well as the etiologies of many diseases. In turn, we may be able to use this knowledge to better treat patients with diseases, including cancer. Although the basic signaling pathway that regulates apoptosis has been known for over 10 years, we still have much to learn about the upstream signaling components that can directly regulate the core apoptosis machinery. The focus of this review will be to direct attention to non-canonical regulators of the BCL2-family of proteins, especially our void of understanding of such interactions, and the controversy that surrounds some such interactions.

Active Notch1 confers a transformed phenotype to primary human melanocytes

The importance of mitogen-activated protein kinase signaling in melanoma is underscored by the prevalence of activating mutations in N-Ras and B-Raf, yet clinical development of inhibitors of this pathway has been largely ineffective, suggesting that alternative oncogenes may also promote melanoma. Notch is an interesting candidate that has only been correlated with melanoma development and progression; a thorough assessment of tumor-initiating effects of activated Notch on human melanocytes would clarify the mounting correlative evidence and perhaps identify a novel target for an otherwise untreatable disease. Analysis of a substantial panel of cell lines and patient lesions showed that Notch activity is significantly higher in melanomas than their nontransformed counterparts. The use of a constitutively active, truncated Notch transgene construct (N(IC)) was exploited to determine if Notch activation is a "driving" event in melanocytic transformation or instead a "passenger" event associated with melanoma progression. N(IC)-infected melanocytes displayed increased proliferative capacity and biological features more reminiscent of melanoma, such as dysregulated cell adhesion and migration. Gene expression analyses supported these observations and aided in the identification of MCAM, an adhesion molecule associated with acquisition of the malignant phenotype, as a direct target of Notch transactivation. N(IC)-positive melanocytes grew at clonal density, proliferated in limiting media conditions, and also exhibited anchorage-independent growth, suggesting that Notch alone is a transforming oncogene in human melanocytes, a phenomenon not previously described for any melanoma oncogene. This new information yields valuable insight into the basic epidemiology of melanoma and launches a realm of possibilities for drug intervention in this deadly disease.

Seeding and propagation of untransformed mouse mammary cells in the lung

The acquisition of metastatic ability by tumor cells is considered a late event in the evolution of malignant tumors. We report that untransformed mouse mammary cells that have been engineered to express the inducible oncogenic transgenes MYC and Kras(D12), or polyoma middle T, and introduced into the systemic circulation of a mouse can bypass transformation at the primary site and develop into metastatic pulmonary lesions upon immediate or delayed oncogene induction. Therefore, previously untransformed mammary cells may establish residence in the lung once they have entered the bloodstream and may assume malignant growth upon oncogene activation. Mammary cells lacking oncogenic transgenes displayed a similar capacity for long-term residence in the lungs but did not form ectopic tumors.

Notch1 co-opts lymphoid enhancer factor 1 for survival of murine T-cell lymphomas

Oncogenic Notch1 mutations are found in most T-lineage acute lymphoblastic leukemias in humans and T-cell lymphomas in mice. However, the mechanism by which Notch1 promotes transformation or maintains malignant cell survival has not been determined fully. Here, we report that expression of the transcription factor lymphoid enhancer factor 1 (Lef1) is Notch dependent in murine T-cell lymphomas in vitro and in vivo, and that the intracellular domain of Notch1 (ICN1) is present at the Lef1 promoter. Lef1 expression is not Notch dependent in primary T-cell progenitors, but Lef1 mRNA is increased by ectopic expression of ICN1 in these cells. We show that Lef1 is required for survival of T-cell lymphoma lines, and that ectopic expression of Lef1 delays lymphoma cell death in the absence of Notch signaling, indicating that Lef1 is an important Notch target in these cells. Therefore, Notch1 co-opts Lef1 during the process of transformation to maintain survival of T-cell lymphomas.

Expression of JAGGED1 in T-lymphocytes results in thymic involution by inducing apoptosis of thymic stromal epithelial cells

Proper development of the thymus and differentiation of T-lymphocytes requires cell-cell interactions between the developing T-lymphocytes and the thymic epithelia. The Delta/Serrate/Lag-2 (DSL)/Notch signal-transduction pathway is known to govern cell fate decisions required for proper development through direct cell-cell interactions. The functional consequences of specific DSL/Notch interactions during the development of a complex organ, such as the thymus, have not been thoroughly elucidated, however. In order to examine the role of DSL proteins during thymus development and T-lymphocyte differentiation, we targeted expression of JAGGED1 in T-lymphocyte progenitors via the control of the proximal lck promoter. Here, we report that expression of JAGGED1 in T cells causes premature involution of the thymus by directing thymic epithelial cells to undergo an apoptotic program. Adoptive transfer of JAGGED1 transgenic bone marrow into non-transgenic mice revealed that JAGGED1 expression on T cells does not alter T-cell differentiation, but is directly responsible for involution of the thymus. We propose that the phenotype of the lck-JAGGED1 transgenic mice is a direct result of specific DSL/Notch interactions and improper cell-to-cell signaling.

Suppression of p53 by Notch in lymphomagenesis: implications for initiation and regression

Aberrant Notch signaling contributes to more than half of all human T-cell leukemias, and accumulating evidence indicates Notch involvement in other human neoplasms. We developed a tetracycline-inducible mouse model (Top-Notch(ic)) to examine the genetic interactions underlying the development of Notch-induced neoplastic disease. Using this model, we show that Notch suppresses p53 in lymphomagenesis through repression of the ARF-mdm2-p53 tumor surveillance network. Attenuation of Notch expression resulted in a dramatic increase in p53 levels that led to tumor regression by an apoptotic program. This shows that continued Notch activity is required to maintain the disease state. However, all tumors relapsed with rapid kinetics, most of which, by reactivation of Notch expression. Furthermore, by directly inhibiting the mdm2-p53 interaction by using either ionizing radiation or the novel small molecule therapeutic Nutlin, p53 can be activated and cause tumor cell death, even in the presence of sustained Notch activity. Therefore, it is the suppression of p53 that provides the Achilles heel for Notch-induced tumors, as activation of p53 in the presence of Notch signaling drives tumor regression. Our study provides proof-of-principle for the rational targeting of therapeutics against the mdm2-p53 pathway in Notch-induced neoplasms. Furthermore, we propose that suppression of p53 by Notch is a key mechanism underlying the initiation of T-cell lymphoma.

Endothelial expression of constitutively active Notch4 elicits reversible arteriovenous malformations in adult mice

Direct communication between arteries and veins without intervening capillary beds is the primary pathology of arteriovenous malformations (AVMs). Although Notch signaling is implicated in embryonic arteriovenous (AV) differentiation, its function in the adult mammalian vasculature has not been established due to the embryonic lethality that often occurs in both gain- and loss-of-function mutants. We expressed a constitutively active Notch4, int3, in the adult mouse endothelium by using the tetracycline-repressible system to suppress int3 during embryogenesis. int3 caused profound blood vessel enlargement and AV shunting, which are hallmarks of AVM, and led to lethality within weeks of its expression. Vessel enlargement, a manifestation of AVM, occurred in an apparently tissue-specific fashion; the liver, uterus, and skin were affected. int3-mediated vascular defects were accompanied by arterialization, including ectopic venous expression of ephrinB2, increased smooth muscle cells, and up-regulation of endogenous Notch signaling. Remarkably, the defective vessels and illness were reversed upon repression of int3 expression. Finally, endothelial expression of a constitutively active Notch1 induced similar hepatic vascular lesions. Our results provide gain-of-function evidence that Notch signaling in the adult endothelium is sufficient to render arterial characteristics and lead to AVMs.

Targeting promiscuous signaling pathways in cancer: another Notch in the bedpost

The chromosomal translocation t(7;9)(q34;q34.3) in human T-cell acute lymphoblastic leukemia results in the constitutive activation of Notch (Nic). Reported mutations in Ikaros cause the loss of DNA-binding, which in turn leads to a loss of repressive activity. Recently, these two mutations have been shown to cooperate in leukemogenesis. The current model proposes that the combination of the loss of Ikaros activity and the gain of constitutive Notch activity disrupts the normal balance between repression and activation at common regulatory elements. Furthermore, the model is extended to suggest that multiple transcription factors coordinate transcriptional repression and activation through these common regulatory elements. In leukemogenesis, the breakdown of this coordinate regulation underlies one of the pathophysiological mechanisms. Finally, using Notch as a template, potential points of interdiction by designer therapeutics are discussed.

Perturbation of Ikaros isoform selection by MLV integration is a cooperative event in Notch(IC)-induced T cell leukemogenesis

The chromosomal translocation t(7;9)(q34;q34.3) in human T cell acute lymphoblastic leukemia (T-ALL) results in the aberrant expression of the intracellular domain of Notch (N(ic)). Consistent with the current multistep model for tumorigenesis, mice that express N(ic) in T cell progenitors develop a T-ALL-like disease with a lengthened latency. Proviral insertional mutagenesis greatly accelerated the onset of leukemia in N(ic) transgenic mice. We demonstrate that the Ikaros (Ik) locus is a common target of proviral integration in N(ic) transgenic mice, which results in the loss of Ik DNA binding activity through altered isoform expression. We propose that cooperative leukemogenesis occurs in cells that have constitutive N(ic) and altered Ik isoform expression because genes normally repressed by Ik become activated by N(ic)/CSL.