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.

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.

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.

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.

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.

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

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 F4/80lo infiltrating macrophages in the kidney after cisplatin treatments, but Clodrosome treatment depleted F4/80hi resident and CD206+ M2 macrophages. Conclusions: These data suggest that Clodrosome depletion of F4/80hi and M2 macrophages in the kidney attenuates development of renal fibrosis after repeated low doses of cisplatin.