| 1. |
- Cerezo-Magaña, Myriam, et al.
(författare)
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Hypoxic induction of exosome uptake through proteoglycan-dependent endocytosis fuels the lipid droplet phenotype in Glioma
- 2021
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Ingår i: Molecular Cancer Research. - : American Association For Cancer Research (AACR). - 1541-7786 .- 1557-3125. ; 19:3, s. 528-540
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Tidskriftsartikel (refereegranskat)abstract
- As an adaptive response to hypoxic stress, aggressive tumors rewire their metabolic phenotype into increased malignant behavior through extracellular lipid scavenging and storage in lipid droplets (LD). However, the underlying mechanisms and potential lipid source retrieved in the hypoxic tumor microenvironment remain poorly understood. Here, we show that exosome-like extracellular vesicles (EV), known as influential messengers in the tumor microenvironment, may also serve anabolic functions by transforming hypoxic, patient-derived human glioblastoma cell lines into the LDþ phenotype. EVs were internalized via a hypoxia-sensitive, endocytic mechanism that fueled LD formation through direct lipid transfer, and independently of fatty acid synthase activity. EVs can enter cells through multiple and yet ill-defined pathways. On a mechanistic level, we found that hypoxia-mediated EV uptake depends on increased heparan sulfate proteoglycan (HSPG) endocytosis that preferentially followed the lipid raft pathway. The functional relevance of HSPG was evidenced by the reversal of EV-mediated LD loading by targeting of HSPG receptor function.
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| 2. |
- Chandran, Vineesh Indira, et al.
(författare)
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Hypoxia Attenuates Trastuzumab Uptake and Trastuzumab-Emtansine (T-DM1) Cytotoxicity through Redistribution of Phosphorylated Caveolin-1
- 2020
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Ingår i: Molecular Cancer Research. - 1541-7786 .- 1557-3125. ; 18:4, s. 644-656
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Tidskriftsartikel (refereegranskat)abstract
- The antibody-drug conjugate trastuzumab-emtansine (T-DM1) offers an additional treatment option for patients with HER2-amplified tumors. However, primary and acquired resistance is a limiting factor in a significant subset of patients. Hypoxia, a hallmark of cancer, regulates the trafficking of several receptor proteins with potential implications for tumor targeting. Here, we have investigated how hypoxic conditions may regulate T-DM1 treatment efficacy in breast cancer. The therapeutic effect of T-DM1 and its metabolites was evaluated in conjunction with biochemical, flow cytometry, and high-resolution imaging studies to elucidate the functional and mechanistic aspects of hypoxic regulation. HER2 and caveolin-1 expression was investigated in a well-annotated breast cancer cohort. Wefind that hypoxia fosters relative resistance to T-DM1 in HER2(+) cells (SKBR3 and BT474). This effect was not a result of deregulated HER2 expression or resistance to emtansine and its metabolites. Instead, we show that hypoxia-induced translocation of caveolin-1 from cytoplasmic vesicles to the plasma membrane contributes to deficient trastuzumab internalization and T-DM1 chemosensitivity. Caveolin-1 depletion mimicked the hypoxic situation, indicating that vesicular caveolin-1 is indispensable for trastuzumab uptake and T-DM1 cytotoxicity. In vitro studies suggested that HER2 and caveolin-1 are not coregulated, which was supported by IHC analysis in patient tumors. We find that phosphorylation-deficient caveolin-1 inhibits trastuzumab internalization and T-DM1 cytotoxicity, suggesting a specific role for caveolin-1 phosphorylation in HER2 trafficking.
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| 3. |
- Chen, Hongxia, et al.
(författare)
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PRL2 Phosphatase Promotes Oncogenic KIT Signaling in Leukemia Cells through Modulating CBL Phosphorylation
- 2024
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Ingår i: Molecular Cancer Research. - 1541-7786. ; 22:1, s. 94-103
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Tidskriftsartikel (refereegranskat)abstract
- Receptor tyrosine kinase KIT is frequently activated in acute myeloid leukemia (AML). While high PRL2 (PTP4A2) expression is correlated with activation of SCF/KIT signaling in AML, the underlying mechanisms are not fully understood. We discovered that inhibition of PRL2 significantly reduces the burden of oncogenic KIT-driven leukemia and extends leukemic mice survival. PRL2 enhances oncogenic KIT signaling in leukemia cells, promoting their proliferation and survival. We found that PRL2 dephosphorylates CBL at tyrosine 371 and inhibits its activity toward KIT, leading to decreased KIT ubiquitination and enhanced AKT and ERK signaling in leukemia cells.
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| 4. |
- Enokido, Takayoshi, et al.
(författare)
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Distinct microRNA Signature and Suppression of ZFP36L1 Define ASCL1-Positive Lung Adenocarcinoma
- 2024
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Ingår i: Molecular Cancer Research. - : American Association For Cancer Research (AACR). - 1541-7786 .- 1557-3125. ; 22:1, s. 29-40
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Tidskriftsartikel (refereegranskat)abstract
- Achaete-scute family bHLH transcription factor 1 (ASCL1) is a master transcription factor involved in neuroendocrine differentiation. ASCL1 is expressed in approximately 10% of lung adenocarcinomas (LUAD) and exerts tumor-promoting effects. Here, we explored miRNA profiles in ASCL1-positive LUADs and identified several miRNAs closely associated with ASCL1 expression, including miR-375, miR-95–3p/miR-95–5p, miR-124–3p, and members of the miR-17~92 family. Similar to small cell lung cancer, Yes1 associated transcriptional regulator (YAP1), a representative miR-375 target gene, was suppressed in ASCL1-positive LUADs. ASCL1 knockdown followed by miRNA profiling in a cell culture model further revealed that ASCL1 positively regulates miR-124–3p and members of the miR-17~92 family. Integrative transcriptomic analyses identified ZFP36 ring finger protein like 1 (ZFP36L1) as a target gene of miR-124–3p, and IHC studies demonstrated that ASCL1-positive LUADs are associated with low ZFP36L1 protein levels. Cell culture studies showed that ectopic ZFP36L1 expression inhibits cell proliferation, survival, and cell-cycle progression. Moreover, ZFP36L1 negatively regulated several genes including E2F transcription factor 1 (E2F1) and snail family transcriptional repressor 1 (SNAI1). In conclusion, our study revealed that suppression of ZFP36L1 via ASCL1-regulated miR-124–3p could modulate gene expression, providing evidence that ASCL1-mediated regulation of miRNAs shapes molecular features of ASCL1-positive LUADs.
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| 5. |
- Pappas, Kyrie, et al.
(författare)
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p53 maintains baseline expression of multiple tumor suppressor genes
- 2017
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Ingår i: Molecular Cancer Research. - 1541-7786. ; 15:8, s. 1051-1062
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Tidskriftsartikel (refereegranskat)abstract
- TP53 is the most commonly mutated tumor suppressor gene and its mutation drives tumorigenesis. Using ChIP-seq for p53 in the absence of acute cell stress, we found that wild-type but not mutant p53 binds and activates numerous tumor suppressor genes, including PTEN, STK11(LKB1), miR-34a, KDM6A(UTX), FOXO1, PHLDA3, and TNFRSF10B through consensus binding sites in enhancers and promoters. Depletion of p53 reduced expression of these target genes, and analysis across 18 tumor types showed that mutation of TP53 associated with reduced expression of many of these genes. Regarding PTEN, p53 activated expression of a luciferase reporter gene containing the p53-consensus site in the PTEN enhancer, and homozygous deletion of this region in cells decreased PTEN expression and increased growth and transformation. These findings show that p53 maintains expression of a team of tumor suppressor genes that may together with the stress-induced targets mediate the ability of p53 to suppress cancer development. p53 mutations selected during tumor initiation and progression, thus, inactivate multiple tumor suppressor genes in parallel, which could account for the high frequency of p53 mutations in cancer.
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| 6. |
- Phung, Bengt, et al.
(författare)
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KITD816V induces SRC-mediated tyrosine phosphorylation of MITF and altered transcription program in melanoma
- 2017
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Ingår i: Molecular Cancer Research. - 1541-7786. ; 15:9, s. 1265-1274
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Tidskriftsartikel (refereegranskat)abstract
- The oncogenic D816V mutation of the KIT receptor is well characterized in systemic mastocytosis and acute myeloid leukemia. Although KITD816V has been found in melanoma, its function and involvement in this malignancy is not understood. Here we show that KITD816V induces tyrosine phosphorylation of MITF through a triple protein complex formation between KIT, MITF, and SRC family kinases. In turn, phosphorylated MITF activates target genes that are involved in melanoma proliferation, cellcycle progression, suppression of senescence, survival, and invasion. By blocking the triple protein complex formation, thus preventing MITF phosphorylation, the cells became hypersensitive to SRC inhibitors. We have therefore delineated a mechanism behind the oncogenic effects of KITD816V in melanoma and provided a rationale for the heightened SRC inhibitor sensitivity in KITD816V transformed cells. Implications: This study demonstrates that an oncogenic tyrosine kinase mutant, KITD816V, can alter the transcriptional program of the transcription factor MITF in melanoma.
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| 7. |
- Adolphe, Christelle, et al.
(författare)
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SOX9 Defines Distinct Populations of Cells in SHH Medulloblastoma but Is Not Required for Math1-Driven Tumor Formation
- 2021
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Ingår i: Molecular Cancer Research. - : American Association For Cancer Research (AACR). - 1541-7786 .- 1557-3125. ; 19:11, s. 1831-1839
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Tidskriftsartikel (refereegranskat)abstract
- Medulloblastoma is the most common malignant pediatric brain tumor and there is an urgent need for molecularly targeted and subgroup-specific therapies. The stem cell factor SOX9, has been proposed as a potential therapeutic target for the treatment of Sonic Hedgehog medulloblastoma (SHH-MB) subgroup tumors, given its role as a downstream target of Hedgehog signaling and in functionally promoting SHH-MB metastasis and treatment resistance. However, the functional requirement for SOX9 in the genesis of medulloblastoma remains to be determined. Here we report a previously undocumented level of SOX9 expression exclusively in proliferating granule cell precursors ( GCP) of the postnatal mouse cerebellum, which function as the medulloblastoma-initiating cells of SHH-MBs. Wild-type GCPs express comparatively lower levels of SOX9 than neural stem cells and mature astroglia and SOX9(low) GCP-like tumor cells constitute the bulk of both infant (Math1Cre: Ptch1(lox/lox)) and adult (Ptch1(LacZ/+)) SHH-MB mouse models. Human medulloblastoma single-cell RNA data analyses reveal three distinct SOX9 populations present in SHH-MB and noticeably absent in other medulloblastoma subgroups: SOX9(+)MATH1(+) (GCP), SOX9(+)GFAP(+) (astrocytes) and SOX9(+)MATH1(+)GFAP(+) (potential tumor-derived astrocytes). To functionally address whether SOX9 is required as a downstream effector of Hedgehog signaling in medulloblastoma tumor cells, we ablated Sox9 using a Math1Cre model system. Surprisingly, targeted ablation of Sox9 in GCPs (Math1Cre:Sox9(lox/lox)) revealed no overt phenotype and loss of Sox9 in SHH-MB (Math1Cre:Ptch1(lox/lox);Sox9(lox/lox)) does not affect tumor formation.
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| 8. |
- Aesoy, R., et al.
(författare)
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An autocrine VEGF/VEGFR2 and p38 signaling loop confers resistance to 4-hydroxytamoxifen in MCF-7 breast cancer cells
- 2008
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Ingår i: Molecular Cancer Research. - 1541-7786 .- 1557-3125. ; 6:10, s. 1630-1638
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Tidskriftsartikel (refereegranskat)abstract
- Tamoxifen, a partial estrogen receptor antagonist, is part of the standard treatment of both primary and advanced breast cancers. However, significant proportions of breast cancers are either de novo resistant or develop tamoxifen resistance during the course of treatment through mechanisms which have been only partly characterized. We have previously found that high vascular endothelial growth factor (VEGF) or VEGF receptor 2 (VEGFR2) expression and concomitant high p38 mitogen-activated protein kinase activity within breast cancers predict a poor outcome for tamoxifen-treated patients. Here, we have molecularly dissected how VEGF/VEGFR2 and p38 are linked, and contribute to tamoxifen resistance within breast cancer using a MCF-7 BC cell model with different 4-hydroxytamoxifen (4-OHT) responsiveness. We report that MCF-7 breast cancer cell lines with tamoxifen resistance have increased secretion of VEGF and increased signaling through VEGFR2 compared with parental MCF-7 cells. 4-OHT treatment caused the ablation of VEGF secretion in parental MCF-7 cells, whereas in the tamoxifen-resistant subline, a VEGF/ VEGFR2 signaling loop was still evident upon treatment. Increased basal levels of total and phosphorylated p38 were observed in tamoxifen-resistant cells. Pharmacologic inhibition of p38 reduced the proliferation of both tamoxifen-responsive and tamoxifen-resistant cells and showed an additive growth-inhibitory effect in combination with 4-OHT. A connection between VEGF/ VEGFR2 and p38 signaling was identified by VEGF and VEGFR2 knockdown, which equally reduced both the total and the active forms of p38 in tamoxifen-resistant cells. Taken together, our results suggest that decreased sensitivityto 4-OHT is caused by a death-protecting VEGF/VEGFR2 and p38 growth factor loop in breast cancer cells. Inhibition of these signaling pathways may be beneficial to overcome tamoxifen resistance. Copyright © 2008 American Association for Cancer Research.
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| 9. |
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| 10. |
- Canter, B. S., et al.
(författare)
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Radium-223-Induced Bystander Effects Cause DNA Damage and Apoptosis in Disseminated Tumor Cells in Bone Marrow
- 2021
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Ingår i: Molecular Cancer Research. - 1541-7786. ; 19:10, s. 1739-1750
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Tidskriftsartikel (refereegranskat)abstract
- Radiation-induced bystander effects have been implicated in contributing to the growth delay of disseminated tumor cells (DTC) caused by (RaCl2)-Ra-223, an alpha particle-emitting radiopharmaceutical. To understand how 223RaCl(2) affects the growth, we have quantified biological changes caused by direct effects of radiation and bystander effects caused by the emitted radiations on DTC and osteocytes. Characterizing these effects contribute to understanding the efficacy of alpha particle-emitting radiopharmaceuticals and guide expansion of their use clinically. MDA-MB-231 or MCF-7 human breast cancer cells were inoculated intratibially into nude mice that were previously injected intravenously with 50 or 600 kBq/kg (RaCl2)-Ra-223. At 1-day and 3-days postinoculation, tibiae were harvested and examined for DNA damage (g-H2AX foci) and apoptosis in osteocytes and cancer cells located within and beyond the range (70 mm) of alpha particles emitted from the bone surface. Irradiated and bystander MDA-MB-231 and MCF-7 cells harbored DNA damage. Bystander MDA-MB-231 cells expressed DNA damage at both treatment levels while bystander MCF-7 cells required the higher administered activity. Osteocytes also had DNA damage regardless of inoculated cancer cell line. The extent of DNA damage was quantified by increases in low (1-2 foci), medium (3-5 foci), and high (5thorn foci) damage. MDA-MB-231 but not MCF-7 bystander cells showed increases in apoptosis in (RaCl2)-Ra-223-treated animals, as did irradiated osteocytes. In summary, radiation-induced bystander effects contribute to DTC cytotoxicity caused by (RaCl2)-Ra-223.
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