Peroxisome proliferator-activated receptor δ suppresses the cytotoxicity of CD8+ T cells by inhibiting RelA DNA binding activity.

The molecular mechanisms regulating CD8+ cytotoxic T lymphocytes (CTLs) are not fully understood. Here, we show that the peroxisome proliferator-activated receptor ƍ (PPAR-δ) suppresses CTL cytotoxicity by inhibiting RelA DNA binding. Treatment of ApcMin/+ mice with the PPAR-δ agonist GW501516 reduced the activation of normal and tumor-associated intestinal CD8+ T cells and increased intestinal adenoma burden. PPAR-δ knockout or knockdown in CTLs increased their cytotoxicity against colorectal cancer cells, whereas overexpression of PPAR-δ or agonist treatment decreased it. Correspondingly, perforin, granzyme B, and interferon γ (IFN-γ) protein and mRNA levels were higher in PPAR-δ knockout or knockdown CTLs and lower in PPAR-δ overexpressing or agonist-treated CTLs. Mechanistically, we found that PPAR-δ binds to RelA, interfering with RelA-p50 heterodimer formation in the nucleus, thereby inhibiting its DNA binding in CTLs. Thus, PPAR-δ is a critical regulator of CTL effector function.

Microinvasive intrascleral double continuous suture repair surgery for cyclodialysis clefts.

BACKGROUND: The traditional suturing method for cyclodialysis cleft usually requires an incision in the sclera for direct suturing, resulting in greater damage and a high risk of postoperative complications. The purpose of this work is to propose a newly intrascleral double continuous suture repair technique for the treatment of cyclodialysis clefts. METHODS: Seven patients with cyclodialysis cleft underwent microinvasive intrascleral double continuous suture repair surgery to restore the attachment of the detached ciliary body to the sclera without scleral incision. All operations were performed by the same surgeon. Preoperative and postoperative visual acuity (VA), intraocular pressure (IOP), slit lamp and corneal examination results, ultrasound biomicroscopy (UBM) and optical coherence tomography (OCT) results were recorded. RESULTS: Closure of the cyclodialysis cleft was achieved in 7 eyes and no obvious complications occurred after the operation. Intraocular pressure increased from preoperatively 6.8 ± 1.35 mmHg (range: 4.8-8.0 mmHg) to postoperatively 12.5 ± 4.0 mmHg (range: 8.0-20.0 mmHg) (paired sample T test, P < 0.01). Best-corrected Snellen visual acuity improved from preoperatively range 20/2000-20/63 to range 20/200-20/25 at final follow-up. CONCLUSION: In short, intrascleral double continuous suture repair surgical is safe and effective in treating cyclodialysis cleft, with minimal surgical trauma.

Synthesis, Antifungal Activity, 3D-QSAR and Controlled Release on Hydrotalcite Study of Longifolene-Derived Diphenyl Ether Carboxylic Acid Compounds.

Twenty-two novel longifolene-derived diphenyl ether-carboxylic acid compounds 7a-7v were synthesized from renewable biomass resources longifolene, and their structures were confirmed by FT-IR, 1H NMR, 13C NMR, and HRMS. The preliminary evaluation of in vitro antifungal activity displayed that compound 7b presented inhibition rates of 85.9%, 82.7%, 82.7%, and 81.4% against Alternaria solani, Cercospora arachidicola, Rhizoctonia solani, and Physalospora piricola, respectively, and compound 7l possessed inhibition rates of 80.7%, 80.4%, and 80.3% against R. solani, C. arachidicola, P. piricola, respectively, exhibiting excellent and broad-spectrum antifungal activities. Besides, compounds 7f and 7a showed significant antifungal activities with inhibition rates of 81.2% and 80.7% against A.solani, respectively. Meanwhile, a reasonable and effective 3D-QSAR mode (r2 = 0.996, q2 = 0.572) has been established by the CoMFA method. Furthermore, the drug-loading complexes 7b/MgAl-LDH were prepared and characterized. Their pH-responsive controlled-release behavior was investigated as well. As a result, complex 7b/MgAl-LDH-2 exhibited excellent controlled-releasing performance in the water/ethanol (10:1, v:v) and under a pH of 5.7.

High value-added application of natural forest product α-pinene: design, synthesis and 3D-QSAR study of novel α-campholenic aldehyde-based 4-methyl-1,2,4-triazole-thioether compounds with significant herbicidal activity.

For exploring novel natural product-derived herbicides, 16 novel α-campholenic aldehyde-based 4-methyl-1,2,4-triazole-thioether compounds were designed, synthesized, and characterized by FT-IR, 1H NMR, 13C NMR, ESI-MS and elemental analysis. The preliminary bioassay showed that, at 100 µg/mL, most of the target compounds displayed significant inhibition activity against root-growth of rape(Brassica campestris L.), with inhibition rates of 85.0%～98.2%(A-class activity level), much better than that of the positive control flumioxazin. In addition, an effective and reasonable 3D-QSAR model was established by CoMFA method in SYBYL-X 2.1.1 software. It was found that, the steric field was the major factor towards the herbicidal activity of the target compounds against B. campestris L., and the introduction of bulky groups into m- and p-position of the benzene ring was favourable to increase the herbicidal activity. This kind of title compounds deserved further study as potential leading compounds for the discovery and development of novel herbicidal agents.

Primary Brainstem Lymphoma: A Population-Based Study.

Background: Primary brainstem lymphoma (PBSL) is rare and malignant. An understanding of this disease is lacking. We aimed to characterize clinical features, estimate survival, and explore survival-related factors of PBSL. Methods: Patients with a histological diagnosis of primary lymphoma in the brainstem (C71.7) from 1975 to 2016 were retrieved from the Surveillance, Epidemiology, and End Results (SEER) program. Log-rank tests and univariate and multivariate Cox proportional hazard analyses were used to identify survival-related factors. Results: PBSL constituted 2.7% of brainstem malignancies. The median age of the PBSL patients was 59.5 years. Diffuse large B cell lymphoma (n = 49, 84.5%) was the most prevalent histology among the 58 cases with reported specific lymphoma subtype. The majority of PBSLs were localized (n = 46, 52.3%), at low Ann Arbor Stage (I/II, n = 63, 70.5%), and presented as a single primary (n = 71, 80.7%). Chemotherapy was applied in 50 (56.8%) cases. Three-year overall survival (OS) and disease-specific survival (DSS) rates were 42.7% and 53.5%, respectively. Multivariate analyses showed that independent predictive/prognostic factors for OS were age (P = 0.004), tumor number (P = 0.029), and chemotherapy (P = 0.001); DSS-related factors only included age (P = 0.014) and chemotherapy (P = 0.008). Conclusions: We estimated survival rates for PBSL patients. Factors associated with OS and DSS were also identified. Our findings addressed the importance of chemotherapy in treating PBSL patients.

The COX-2-PGE2 Pathway Promotes Tumor Evasion in Colorectal Adenomas.

The mechanisms underlying the regulation of a checkpoint receptor, PD-1, in tumor-infiltrating immune cells during the development of colorectal cancer are not fully understood. Here we demonstrate that COX-2-derived PGE2, an inflammatory mediator and tumor promoter, induces PD-1 expression by enhancing NFκB's binding to the PD-1 promoter via an EP4-PI3K-Akt signaling pathway in both CD8+ T cells and macrophages. Moreover, PGE2 suppresses CD8+ T-cell proliferation and cytotoxicity against tumor cells and impairs macrophage phagocytosis of cancer cells via an EP4-PI3K-Akt-NFκB-PD-1 signaling pathway. In contrast, inhibiting the COX-2-PGE2-EP4 pathway increases intestinal CD8+ T-cell activation and proliferation and enhances intestinal macrophage phagocytosis of carcinoma cells accompanied by reduction of PD-1 expression in intestinal CD8+ T cells and macrophages in ApcMin/+ mice. PD-1 expression correlates well with COX-2 levels in human colorectal cancer specimens. Both elevated PD-1 and COX-2 are associated with poorer overall survival in patients with colorectal cancer. Our results uncover a novel role of PGE2 in tumor immune evasion. They may provide the rationale for developing new therapeutic approaches to subvert this process by targeting immune checkpoint pathways using EP4 antagonists. In addition, our findings reveal a novel mechanism explaining how NSAIDs reduce colorectal cancer risk by suppressing tumor immune evasion. PREVENTION RELEVANCE: These findings provide a potential explanation underlying the chemopreventive effect of NSAIDs on reducing colorectal cancer incidence during premalignancy and provide a rationale for developing EP4 antagonists for colorectal cancer prevention and treatment. Simply targeting PGE2 signaling alone may be efficacious in colorectal cancer prevention and treatment, avoiding side effects associated with NSAIDs.

Synthesis, Antifungal Activity and 3D-QSAR Study of Novel Anisaldehyde-Derived Amide-Thiourea Compounds.

Succinate dehydrogenase (SDH) is an important target enzyme for designing agricultural chemical fungicides. In order to explore novel natural product-based antifungal agents, twenty-one unreported anisaldehyde-derived amide-thiourea compounds were designed and synthesized using the principle of active splicing, and structurally confirmed by 1 H-NMR, 13 C-NMR, ESI-MS, FT-IR, and element analysis. In vitro antifungal activity of the target compounds was evaluated by the agar dilution method. The results showed that some target compounds exhibited better or comparable antifungal activity than that of the commercial fungicide chlorothalonil, in which compounds 5c, 5o, and 5r displayed excellent antifungal activity of 92.6 %, 92.6 % and 99.1 % against P. piricola, respectively, better than that of the positive control. In addition, 3D-QSAR analysis was carried out by the CoMFA method to reveal the relationship between the structures of the target compounds and their inhibitory activities. The simulative binding mode of the target compounds and SDH was also studied by molecular docking.

Clinical characteristics and outcomes of primary intracranial alveolar soft-part sarcoma: A case report.

BACKGROUND: Primary intracranial alveolar soft-part sarcoma (PIASPS) is a rare malignancy. We aimed to investigate the clinical profiles and outcomes for PIASPS. CASE SUMMARY: We firstly reported five consecutive cases from our institute. Then, the cases from previous studies were pooled and analyzed to delineate the characteristics of this disease. Our cohort included two males and three females. The median age was 21-years-old (range: 8-54-years-old). All the patients received surgical treatment. Gross total resection (GTR), radiotherapy, and chemotherapy were administered in 3 patients, 4 patients, and 1 patient, respectively. After a median follow-up of 36 mo, tumor progression was noticed in 4 patients; and 3 patients died of the disease. Pooled data (n = 14) contained 5 males and 9 females with a median age of 19 years. The log-rank tests showed that GTR (P = 0.011) could prolong progression-free survival, and radiotherapy (P < 0.001) resulted in longer overall survival. CONCLUSION: Patients with PIASPS suffer from poor outcomes. Surgical treatment is the first choice, and GTR should be achieved when the tumor is feasible. Patients with PIASPS benefit from radiotherapy, which should be considered as a part of treatment therapies.

Synthesis of Myrtenal-Based Nanocellulose/Diacylhydrazine Complexes with Antifungal Activity for Plant Protection.

In search of novel bioactive compounds with excellent and broad-spectrum antifungal activity and nanopesticides with sustained releasing property, a series of novel myrtenal-based diacylhydrazines were designed, synthesized, and characterized. The preliminary bioassay showed that myrtenal-based 2-picolinyl hydrazide exhibited better or comparable antifungal activity than that of the commercial fungicides boscalid and chlorothalonil against the tested fungi. Furthermore, myrtenal-based nanocellulose was designed as a nanopesticide carrier and prepared from two biomass materials, bleached bagasse pulp and turpentine oil. Drug-loading capacities (LCs) of these carriers and sustained releasing properties of corresponding complexes were also evaluated, and the results indicated that the esterification reaction in the different solvents would affect the micromorphology of carriers, which was the important influential factor for loading or releasing drugs. To our delight, complex VIII-3 (LC = 0.32, total releasing amount/time = 99.8%/168 h) showed a macroporous framework with the drug evenly distributed across the opening network and staged drug-releasing performance that deserved further study as a nanopesticide.

Mutant APC promotes tumor immune evasion via PD-L1 in colorectal cancer.

PD-L1 expression is elevated in various human cancers, including colorectal cancer. High levels of PD-L1 expressed on tumor epithelial cells are one of the potential mechanisms by which tumor cells become resistant to immune attack. However, PD-L1 regulation in tumor cells is not fully understood. Here we demonstrate that mutations in the adenomatous polyposis coli (APC) gene lead to colonic epithelial cell resistance to CD8+ T cell cytotoxicity by induction of PD-L1 expression. Mechanistically, this occurs as a result of the ß-catenin/TCF4 complex binding to the PD-L1 promoter, leading to increased transcription. Our findings not only reveal a novel mechanism by which APC mutations induce tumor immune evasion via an immune checkpoint pathway but also pave the way for developing ß-catenin or TCF4 inhibitors as possible new options for immune checkpoint inhibition.

Melatonin reverses nasopharyngeal carcinoma cisplatin chemoresistance by inhibiting the Wnt/ß-catenin signaling pathway.

Cisplatin (DDP)-based concurrent chemo-radiotherapy is a standard approach to treat locoregionally advanced nasopharyngeal carcinoma (NPC). However, many patients eventually develop recurrence and/or distant metastasis due to chemoresistance. In this study, we aimed to elucidate the effects of melatonin on DDP chemoresistance in NPC cell lines in vitro and vivo, and we explored potential chemoresistance mechanisms. We found that DDP chemoresistance in NPC cells is mediated through the Wnt/ß-catenin signaling pathway. Melatonin not only reversed DDP chemoresistance, but also enhanced DDP antitumor activity by suppressing the nuclear translocation of ß-catenin, and reducing expression of Wnt/ß-catenin response genes in NPC cells. In vivo, combined treatment with DDP and melatonin reduced tumor burden to a greater extent than single drug-treatments in an orthotopic xenograft mouse model. Our findings provide novel evidence that melatonin inhibits the Wnt/ß-catenin pathway in NPC, and suggest that melatonin could be applied in combination with DDP to treat NPC.

microRNA-9-5p alleviates blood-brain barrier damage and neuroinflammation after traumatic brain injury.

The level of microRNA-9-5p (miRNA-9-5p) in brain tissues is significantly changed after traumatic brain injury (TBI). However, the effect of miRNA-9-5p for brain function in TBI has not been elucidated. In this study, a controlled cortical impact model was used to induce TBI in Sprague-Dawley rats, and an oxygen glucose deprivation model was used to mimic the pathological state in vitro. Brain microvascular endothelial cells (BMECs) and astrocytes were extracted from immature Sprague-Dawley rats and cocultured to reconstruct blood-brain barrier (BBB) in vitro. The results show that the level of miRNA-9-5p was significantly increased in brain tissues after TBI, and up-regulation of miRNA9-5p contributed to the recovery of neurological function. Up-regulation of miRNA-9-5p with miRNA agomir may significantly alleviate apoptosis, neuroinflammation, and BBB damage in rats after TBI. Moreover, a dual luciferase reporter assay confirmed that miRNA-9-5p is a post-transcriptional modulator of Ptch-1. In in vitro experiments, the results confirmed that up-regulation of miRNA-9-5p with miRNA mimic alleviates cellular apoptosis, inflammatory response, and BBB damage mainly by inhibiting Ptch-1. In addition, we found that the activation of Hedgehog pathway was accompanied by inhibition of NF-κB/MMP-9 pathway in the BMECs treated with miRNA-9-5p mimic. Taken together, these results indicate that up-regulation of miRNA-9-5p alleviates BBB damage and neuroinflammatory responses by activating the Hedgehog pathway and inhibiting NF-κB/MMP-9 pathway, which promotes the recovery of neurological function after TBI.

Prostaglandin E2 Induces miR675-5p to Promote Colorectal Tumor Metastasis via Modulation of p53 Expression.

BACKGROUND & AIMS: Prostaglandin E2 (PGE2) promotes colorectal tumor formation and progression by unknown mechanisms. We sought to identify microRNAs (miRNAs) that might mediate the effects of PGE2 on colorectal cancer (CRC) development. METHODS: We incubated LS174T colorectal cancer cells with PGE2 or without (control) and used miRNA-sequencing technology to compare expression patterns of miRNAs. We knocked down levels of specific miRNAs or proteins in cells using small interfering RNAs or genome editing. Cells were analyzed by immunoblot, quantitative polymerase chain reaction, chromosome immunoprecipitation, cell invasion, and luciferase reporter assays; we measured gene expression, binding activity, cell migration and invasion, and transcriptional activity of transcription factors. NOD-scidIL-2Rg-/- mice were given injections of LS174T cells, and growth of primary tumors and numbers of liver and lung metastases were quantified and analyzed by histology. We used public databases to identify correlations in gene expression pattern with patient outcomes. RESULTS: We identified miRNA 675-5p (miR675-5p) as the miRNA most highly up-regulated by incubation of colorectal cancer cells with PGE2. PGE2 increased expression of miR675-5p by activating expression of Myc, via activation of protein kinase B, also known as (AKT), nuclear factor κB, and ß-catenin. PGE2 increased the invasive activities of cultured CRC cells. LS174T cells incubated with PGE2 formed more liver and lung metastases in mice than control LS174T cells. We identified a 3' untranslated region in the TP53 messenger RNA that bound miR675-5p; binding resulted in loss of the p53 protein. Expression of miR675-5p or its precursor RNA, H19, correlated with expression of cyclooxygenase-1 and cyclooxygenase-2 and shorter survival times of patients with CRC. CONCLUSIONS: We found that treatment of mice with PGE2 increased CRC cells invasive activity and ability to form liver and lung metastases. PGE2 down-regulates expression of p53 by increasing expression of miR675-5p, which binds to and prevents translation of TP53 messenger RNA. These findings provide insight into the mechanisms by which PGE2 promotes tumor development and progression. Strategies to target PGE2 might be developed for treatment of CRC.

Intramedullary Schwannoma of Cervical Spinal Cord Presenting Inconspicuous Enhancement with Gadolinium.

BACKGROUND: Intramedullary schwannomas of the spinal cord are extremely rare. Most previous studies are case reports, which have found that intramedullary schwannomas could be homogeneous or asymmetrically enhanced with gadolinium. However, intramedullary schwannomas with minimal enhancement have not been reported. CASE DESCRIPTION: This article describes a 34-year-old patient who presented with nonradiative neck pain, progressive weakness of the left limbs, and sensory deficit of both lower extremities. Preoperative examinations such as magnetic resonance imaging (MRI) were performed, and the patient underwent surgical treatment. MRI showed that the lesion presented unsharp enhancement with gadolinium on T1-weighted images. Histopathologic findings were consistent with the diagnosis of schwannoma. CONCLUSIONS: We report a case of intramedullary schwannoma that presented inconspicuous enhancement with gadolinium. MRI is useful but cannot be used to differentiate schwannomas from other intramedullary spinal tumours. Surgical resection is the most vital factor for the treatment of intramedullary schwannoma.

Bcl-2 and Bcl-xL mediate resistance to receptor tyrosine kinase-targeted therapy in lung and gastric cancer.

Promising clinical efficacy has been observed with receptor tyrosine kinase inhibitors (TKIs) particularly in lung and gastric cancers with mutations or amplifications in the targeted receptor tyrosine kinases (RTKs). However, the efficacy and the duration of the response to these inhibitors are limited by the emergence of drug resistance. Here, we report treatment of RTK-dependent lung and gastric cancer cell lines with TKIs increased protein levels of Bcl-2 and Bcl-xL. The combination of the Bcl-2 and Bcl-xL inhibitor ABT-263 and TKIs was superior to TKIs alone in reducing cell viability and capacity of resistant colony formation. Furthermore, resistant cells established with exposure of RTK-dependent cells to increasing concentrations of TKIs also express higher levels of Bcl-2 or Bcl-xL compared with their parental cells. The combination of inhibitors of PI3K/AKT, MEK/ERK, and Bcl-2/Bcl-xL effectively reduced the viability of resistant cells and inhibited tumor size in a xenograft model derived from resistant cells by inducing apoptosis. Our results define a generalizable resistance mechanism to TKIs and rationalize inhibition of Bcl-2 and Bcl-xL as a strategy to augment responses and blunt acquired resistance to TKIs in lung and gastric cancer.

Effect of Preserving the Pituitary Stalk During Resection of Craniopharyngioma in Children on the Diabetes Insipidus and Relapse Rates and Long-Term Outcomes.

OBJECTIVE: The objective of this study was to investigate the effect of preserving an infiltrated pituitary stalk during the resection of craniopharyngioma of pituitary stalk origin on postoperative outcomes and thus provide a theoretical basis for microsurgical treatment and prognosis. METHODS: We screened the clinical data of all 103 pediatric patients with craniopharyngioma undergoing surgical treatment at our department between January 2006 and January 2013 and conducted a retrospective analysis of 82 patients with craniopharyngioma originating in the pituitary stalk. The patients were followed up from 12 months to 8 years. We analyzed the effect of preserving the pituitary stalk on the early and persistent diabetes insipidus rates, postoperative relapse rate, and mortality. RESULTS: In the total resection group (n = 67), the early and persistent diabetes insipidus rates were significantly lower in the 46 patients (68.7%) with a pituitary stalk than in those whose pituitary stalk was removed (P < 0.05); no significant difference was observed in the relapse rate between the 2 subgroups (P > 0.05). In the subtotal resection group (n = 15), a significant difference was observed in the early and persistent diabetes insipidus rates (P < 0.05), but no significant difference was observed in the relapse rate between the patients with a pituitary stalk and those whose pituitary stalk was removed (P > 0.05). CONCLUSIONS: For children with craniopharyngioma of pituitary stalk origin, preserving the pituitary stalk has a significant effect on the early and persistent diabetes insipidus rates. When intraoperative exploration showed excessive adhesion between the tumor and pituitary stalk, we opted to preserve the pituitary stalk, which significantly reduced the early and persistent postoperative diabetes insipidus rates, without significantly increasing the relapse or mortality rate.

CXCL1 Is Critical for Premetastatic Niche Formation and Metastasis in Colorectal Cancer.

Emerging evidence suggests that the primary tumor influences the development of supportive metastatic microenvironments, referred to as premetastatic niches, in certain distant organs before arrival of metastatic cells. However, the mechanisms underlying the contributions of the primary tumor to premetastatic niche formation are not fully understood. Here, we demonstrate that colorectal carcinoma cells secrete VEGFA, which stimulates tumor-associated macrophages to produce CXCL1 in the primary tumor. Elevation of CXCL1 in premetastatic liver tissue recruited CXCR2-positive myeloid-derived suppressor cells (MDSC) to form a premetastatic niche that ultimately promoted liver metastases. Importantly, premetastatic liver-infiltrating MDSCs induced tumor cell survival without involvement of innate or adaptive immune responses. Our study provides the first evidence that primary malignant cell-secreted VEGFA stimulates tumor-associated macrophages to produce CXCL1, which recruits CXCR2-positive MDSCs to form a premetastatic niche to promote liver metastases. Our findings not only shed light on how the tumor microenvironment contributes to premetastatic niche formation at distant sites, but they also provide comprehensive insights into how MDSCs are recruited to other organs where they contribute to metastatic spread of disease. Moreover, our work also provides a rationale for development of CXCR2 antagonists to inhibit or prevent metastatic spread of disease. Cancer Res; 77(13); 3655-65. ©2017 AACR.

[Effects of serum starvation on cell cycle synchronization in primary human umbilical vein endothelial cells].

OBJECTIVE: To investigate the optimal starvation conditions of human umbilical vein endothelial cells (HUVECs) and establish a highly efficient and stable method for separating HUVECs. METHODS: HUVECs harvested from human umbilical cords by digestion with 0.1% collagenase II for 15 min were cultured in endothelial culture medium (ECM) containing 5% fetal bovine serum (FBS), 1% endothelial cell growth factor (ECGS) and 1% penicillin/streptomycin solution(P/S) at 37 degrees celsius; in 5% CO2. The cells were observed for cell morphology under an inverted microscope and identified with immunofluorescence assay. The purity of HUVECs was detected using flow cytometry (FCM). The cell cycles of HUVECs cultured in the presence of 0, 0.1%, 0.5%, and 1% FBS for 0, 6, 12, 18, and 24 h were analyzed with flow cytometry. RESULTS: s The purity of HUVECs harvested by digestion with 0.1% collagenase II reached 99.67%. The primary HUVECs showed a cobblestone or volute appearance in vitro. Immunocytochemistry showed that HUVECs highly expressed VIII-related antigen. Cell culture in the presence of different concentrations of FBS for 6 h resulted in 70% G0/G1 phase cells, which increased to 80%-90% at 12 h of cell culture, and further to around 95% at 18 and 24 h. CONCLUSION: Digestion with 0.1% collagenase II can obtain high-purity primary HUVECs. Culturing HUVECs in serum-free medium for 12 h can result in a high purity (over 80%) of G0/G1 phase cells.

Pim1 kinase regulates c-Kit gene translation.

BACKGROUND: Receptor tyrosine kinase, c-Kit (CD117) plays a pivotal role in the maintenance and expansion of hematopoietic stem/progenitor cells (HSPCs). Additionally, over-expression and/or mutational activation of c-Kit have been implicated in numerous malignant diseases including acute myeloid leukemia. However, the translational regulation of c-Kit expression remains largely unknown. METHODS AND RESULTS: We demonstrated that loss of Pim1 led to specific down-regulation of c-Kit expression in HSPCs of Pim1-/- mice and Pim1-/-2-/-3-/- triple knockout (TKO) mice, and resulted in attenuated ERK and STAT3 signaling in response to stimulation with stem cell factor. Transduction of c-Kit restored the defects in colony forming capacity seen in HSPCs from Pim1-/- and TKO mice. Pharmacologic inhibition and genetic modification studies using human megakaryoblastic leukemia cells confirmed the regulation of c-Kit expression by Pim1 kinase: i.e., Pim1-specific shRNA knockdown down-regulated the expression of c-Kit whereas overexpression of Pim1 up-regulated the expression of c-Kit. Mechanistically, inhibition or knockout of Pim1 kinase did not affect the transcription of c-Kit gene. Pim1 kinase enhanced c-Kit 35S methionine labeling and increased the incorporation of c-Kit mRNAs into the polysomes and monosomes, demonstrating that Pim1 kinase regulates c-Kit expression at the translational level. CONCLUSIONS: Our study provides the first evidence that Pim1 regulates c-Kit gene translation and has important implications in hematopoietic stem cell transplantation and cancer treatment.

Activation of Pim Kinases Is Sufficient to Promote Resistance to MET Small-Molecule Inhibitors.

Mesenchymal-epithelial transition (MET) blockade offers a new targeted therapy particularly in those cancers with MET amplification. However, the efficacy and the duration of the response to MET inhibitors are limited by the emergence of drug resistance. Here, we report that resistance to small-molecule inhibitors of MET can arise from increased expression of the prosurvival Pim protein kinases. This resistance mechanism was documented in non-small cell lung cancer and gastric cancer cells with MET amplification. Inhibition of Pim kinases enhanced cell death triggered by short-term treatment with MET inhibitors. Pim kinases control the translation of antiapoptotic protein Bcl-2 at an internal ribosome entry site and this mechanism was identified as the basis for Pim-mediated resistance to MET inhibitors. Protein synthesis was increased in drug-resistant cells, secondary to a Pim-mediated increase in cap-independent translation. In cells rendered drug resistant by chronic treatment with MET inhibitors, genetic or pharmacologic inhibition of Pim kinases was sufficient to restore sensitivity in vitro and in vivo. Taken together, our results rationalize Pim inhibition as a strategy to augment responses and blunt acquired resistance to MET inhibitors in cancer.