The FABP12/PPARγ pathway promotes metastatic transformation by inducing epithelial‐to‐mesenchymal transition and lipid‐derived energy production in prostate cancer cells

Early stage localized prostate cancer (PCa) has an excellent prognosis; however, patient survival drops dramatically when PCa metastasizes. The molecular mechanisms underlying PCa metastasis are complex and remain unclear. Here, we examine the role of a new member of the fatty acid‐binding protein (FABP) family, FABP12, in PCa progression. FABP12 is preferentially amplified and/or overexpressed in metastatic compared to primary tumors from both PCa patients and xenograft animal models. We show that FABP12 concurrently triggers metastatic phenotypes (induced epithelial‐to‐mesenchymal transition (EMT) leading to increased cell motility and invasion) and lipid bioenergetics (increased fatty acid uptake and accumulation, increased ATP production from fatty acid β‐oxidation) in PCa cells, supporting increased reliance on fatty acids for energy production. Mechanistically, we show that FABP12 is a driver of PPARγ activation which, in turn, regulates FABP12''s role in lipid metabolism and PCa progression. Our results point to a novel role for a FABP‐PPAR pathway in promoting PCa metastasis through induction of EMT and lipid bioenergetics.

Abbreviations

AR

androgen receptor

ATP

adenosine triphosphate

CN

copy number

CPT1

carnitine palmitoyltransferase I

CS

citrate synthase

EMT

epithelial–mesenchymal transition

ET

electron transfer‐state

FABP

fatty acid‐binding protein

LD

lipid droplet

OA

oleic acid

PCa

prostate cancer

PPAR

peroxisome proliferator‐activated receptor

PPRE

peroxisome proliferator‐activated receptor response element

TZD

thiazolidinediones

     

Constitutive activation of integrin αvβ3 contributes to anoikis resistance of ovarian cancer cells

Epithelial ovarian cancer involves the shedding of single tumor cells or spheroids from the primary tumor into ascites, followed by their survival, and transit to the sites of metastatic colonization within the peritoneal cavity. During their flotation, anchorage‐dependent epithelial‐type tumor cells gain anoikis resistance, implicating integrins, including αvß3. In this study, we explored anoikis escape, cisplatin resistance, and prosurvival signaling as a function of the αvß3 transmembrane conformational activation state in cells suspended in ascites. A high‐affinity and constitutively signaling‐competent αvß3 variant, which harbored unclasped transmembrane domains, was found to confer delayed anoikis onset, enhanced cisplatin resistance, and reduced cell proliferation in ascites or 3D‐hydrogels, involving p27^kip upregulation. Moreover, it promoted EGF‐R expression and activation, prosurvival signaling, implicating FAK, src, and PKB/Akt. This led to the induction of the anti‐apoptotic factors Bcl‐2 and survivin suppressing caspase activation, compared to a signaling‐incapable αvß3 variant displaying firmly associated transmembrane domains. Dissecting the mechanistic players for αvß3‐dependent survival and peritoneal metastasis of ascitic ovarian cancer spheroids is of paramount importance to target their anchorage independence by reversing anoikis resistance and blocking αvß3‐triggered prosurvival signaling.

Abbreviations

CLSM

confocal laser scanning microscopy

ECM

extracellular matrix

EGF‐R

epidermal growth factor receptor

EOC

epithelial ovarian cancer

FAK

focal adhesion kinase

FIGO

Fédération Internationale de Gynécologie et d''Obstétrique

GAPDH

glyceraldehyde 3‐phosphate dehydrogenase)

GpA

glycophorin A

IMD

integrin‐mediated death

MAPK

mitogen‐activated protein kinases

PI

propidium iodide

RGD

Arg‐Gly‐Asp

TMD

transmembrane domain

     

SIK2 represses AKT/GSK3β/β‐catenin signaling and suppresses gastric cancer by inhibiting autophagic degradation of protein phosphatases

Salt‐inducible kinase 2 (SIK2) is an important regulator in various intracellular signaling pathways related to apoptosis, tumorigenesis and metastasis. However, the involvement of SIK2 in gastric tumorigenesis and the functional linkage with gastric cancer (GC) progression remain to be defined. Here, we report that SIK2 was significantly downregulated in human GC tissues, and reduced SIK2 expression was associated with poor prognosis of patients. Overexpression of SIK2 suppressed the migration and invasion of GC cells, whereas knockdown of SIK2 enhanced cell migratory and invasive capability as well as metastatic potential. These changes in the malignant phenotype resulted from the ability of SIK2 to suppress epithelial–mesenchymal transition via inhibition of AKT/GSK3β/β‐catenin signaling. The inhibitory effect of SIK2 on AKT/GSK3β/β‐catenin signaling was mediated primarily through inactivation of AKT, due to its enhanced dephosphorylation by the upregulated protein phosphatases PHLPP2 and PP2A. The upregulation of PHLPP2 and PP2A was attributable to SIK2 phosphorylation and activation of mTORC1, which inhibited autophagic degradation of these two phosphatases. These results suggest that SIK2 acts as a tumor suppressor in GC and may serve as a novel prognostic biomarker and therapeutic target for this tumor.

Abbreviations

AMPK

AMP‐activated protein kinase

Co‐IP

co‐immunoprecipitation

EMT

epithelial–mesenchymal transition

GAPDH

glyceraldehyde‐3‐phosphate dehydrogenase

GC

gastric cancer

GEO

Gene Expression Omnibus

H&E

hematoxylin and eosin

IHC

immunohistochemistry

mTOR

mechanistic target of rapamycin

NC

negative control

PHLPP

PH domain leucine‐rich repeat protein phosphatase

PP2A

protein phosphatase 2A

qRT‐PCR

quantitative real‐time polymerase chain reaction

SIK2

salt‐inducible kinase 2

TCF/LEF

T cell factor/lymphoid enhancer‐binding factor

TCGA

The Cancer Genome Atlas

     

Downregulation of miR‐326 and its host gene β‐arrestin1 induces pro‐survival activity of E2F1 and promotes medulloblastoma growth

Persistent mortality rates of medulloblastoma (MB) and severe side effects of the current therapies require the definition of the molecular mechanisms that contribute to tumor progression. Using cultured MB cancer stem cells and xenograft tumors generated in mice, we show that low expression of miR‐326 and its host gene β‐arrestin1 (ARRB1) promotes tumor growth enhancing the E2F1 pro‐survival function. Our models revealed that miR‐326 and ARRB1 are controlled by a bivalent domain, since the H3K27me3 repressive mark is found at their regulatory region together with the activation‐associated H3K4me3 mark. High levels of EZH2, a feature of MB, are responsible for the presence of H3K27me3. Ectopic expression of miR‐326 and ARRB1 provides hints into how their low levels regulate E2F1 activity. MiR‐326 targets E2F1 mRNA, thereby reducing its protein levels; ARRB1, triggering E2F1 acetylation, reverses its function into pro‐apoptotic activity. Similar to miR‐326 and ARRB1 overexpression, we also show that EZH2 inhibition restores miR‐326/ARRB1 expression, limiting E2F1 pro‐proliferative activity. Our results reveal a new regulatory molecular axis critical for MB progression.

Abbreviations

ARRB1

β‐arrestin1

BTC

bulk tumor cell

CSCs

cancer stem cells

EZH2

enhancer of zeste homolog 2

GCP

granule cell progenitors

MB

medulloblastoma

OFC

oncosphere‐forming cell

     

TGFβ promotes YAP‐dependent AXL induction in mesenchymal‐type lung cancer cells

The acquisition of chemoresistance remains a major cause of cancer mortality due to the limited accessibility of targeted or immune therapies. However, given that severe alterations of molecular features during epithelial‐to‐mesenchymal transition (EMT) lead to acquired chemoresistance, emerging studies have focused on identifying targetable drivers associated with acquired chemoresistance. Particularly, AXL, a key receptor tyrosine kinase that confers resistance against targets and chemotherapeutics, is highly expressed in mesenchymal cancer cells. However, the underlying mechanism of AXL induction in mesenchymal cancer cells is poorly understood. Our study revealed that the YAP signature, which was highly enriched in mesenchymal‐type lung cancer, was closely correlated to AXL expression in 181 lung cancer cell lines. Moreover, using isogenic lung cancer cell pairs, we also found that doxorubicin treatment induced YAP nuclear translocation in mesenchymal‐type lung cancer cells to induce AXL expression. Additionally, the concurrent activation of TGFβ signaling coordinated YAP‐dependent AXL expression through SMAD4. These data suggest that crosstalk between YAP and the TGFβ/SMAD axis upon treatment with chemotherapeutics might be a promising target to improve chemosensitivity in mesenchymal‐type lung cancer.

Abbreviations

AUC

area under the curve

AXL

AXL receptor tyrosine kinase

BCL2

B‐cell lymphoma 2

CTD2

cancer target discovery and development

CTGF

connective tissue growth factor

DEG

differentially expressed genes

DOXO

doxorubicin

EMT

epithelial–mesenchymal transition

Eto

etoposide

FDA

Food and Drug Administration

ITGB3

integrin beta‐3

MAPK

mitogen‐activated protein kinase

MMP2

matrix metalloproteinase‐2

MMP9

matrix metalloproteinase‐9

mRNA

messenger RNA

NF‐κB

nuclear factor kappa‐light‐chain‐enhancer of activated B cells

SBE

SMAD binding element

SERPINE1

serpin family E member 1

siRNA

small interfering RNA

ssGSEA

single‐sample gene set enrichment analysis

TCGA

The Cancer Genome Atlas

TGFβ

transforming growth factor beta

YAP

Yes‐associated protein

YAP8SA

mutants of inhibitory phosphorylation site at eight serine to Alanine of YAP

ZEB1

zinc finger E‐box binding homeobox 1

ZEB2

zinc finger E‐box‐binding homeobox 2

     

Long noncoding RNA LINC01578 drives colon cancer metastasis through a positive feedback loop with the NF‐κB/YY1 axis

Metastasis accounts for poor prognosis of cancers and related deaths. Accumulating evidence has shown that long noncoding RNAs (lncRNAs) play critical roles in several types of cancer. However, which lncRNAs contribute to metastasis of colon cancer is still largely unknown. In this study, we found that lncRNA LINC01578 was correlated with metastasis and poor prognosis of colon cancer. LINC01578 was upregulated in colon cancer, associated with metastasis, advanced clinical stages, poor overall survival, disease‐specific survival, and disease‐free survival. Gain‐of‐function and loss‐of‐function assays revealed that LINC01578 enhanced colon cancer cell viability and mobility in vitro and colon cancer liver metastasis in vivo. Mechanistically, nuclear factor kappa B (NF‐κB) and Yin Yang 1 (YY1) directly bound to the LINC01578 promoter, enhanced its activity, and activated LINC01578 expression. LINC01578 was shown to be a chromatin‐bound lncRNA, which directly bound NFKBIB promoter. Furthermore, LINC01578 interacted with and recruited EZH2 to NFKBIB promoter and further repressed NFKBIB expression, thereby activating NF‐κB signaling. Through activation of NF‐κB, LINC01578 further upregulated YY1 expression. Through activation of the NF‐κB/YY1 axis, LINC01578 in turn enhanced its own promoter activity, suggesting that LINC01578 and NF‐κB/YY1 formed a positive feedback loop. Blocking NF‐κB signaling abolished the oncogenic roles of LINC01578 in colon cancer. Furthermore, the expression levels of LINC01578, NFKBIB, and YY1 were correlated in clinical tissues. Collectively, this study demonstrated that LINC01578 promoted colon cancer metastasis via forming a positive feedback loop with NF‐κB/YY1 and suggested that LINC01578 represents a potential prognostic biomarker and therapeutic target for colon cancer metastasis.

Abbreviations

ChIP

chromatin immunoprecipitation

ChIRP

chromatin isolation by RNA purification

COAD

colon adenocarcinoma

CPAT

Coding‐Potential Assessment Tool

CPC

coding potential calculator

DFS

disease‐free survival

DSS

disease‐specific survival

EdU

5‐ethynyl‐2''‐deoxyuridine

H&E

hematoxylin and eosin

HR

hazard ratio

IHC

immunohistochemistry

IKK

IκB kinase

IκB

inhibitory κB

lncRNAs

long noncoding RNAs

NC

negative control

NCBI

National Center for Biotechnology Information

NF‐κB

nuclear factor kappa B

qRT‐PCR

quantitative real‐time polymerase chain reaction

RIP

RNA immunoprecipitation

RPISeq

RNA‐Protein Interaction Prediction

TCGA

The Cancer Genome Atlas

TNF

tumor necrosis factor

TUNEL

TdT‐mediated dUTP Nick‐End Labeling

YY1

Yin Yang 1

     

BAP1 suppresses prostate cancer progression by deubiquitinating and stabilizing PTEN

Deubiquitinase BAP1 is an important tumor suppressor in several malignancies, but its functions and critical substrates in prostate cancer (PCa) remain unclear. Here, we report that the mRNA and protein expression levels of BAP1 are downregulated in clinical PCa specimens. BAP1 can physically bind to and deubiquitinate PTEN, which inhibits the ubiquitination‐mediated degradation of PTEN and thus stabilizes PTEN protein. Ectopically expressed BAP1 in PCa cells increases PTEN protein level and subsequently inhibits the AKT signaling pathway, thus suppressing PCa progression. Conversely, knockdown of BAP1 in PCa cells leads to the decrease in PTEN protein level and the activation of the Akt signaling pathway, therefore promoting malignant transformation and cancer metastasis. However, these can be reversed by the re‐expression of PTEN. More importantly, we found that BAP1 protein level positively correlates with PTEN in a substantial fraction of human cancers. These findings demonstrate that BAP1 is an important deubiquitinase of PTEN for its stability and the BAP1‐PTEN signaling axis plays a crucial role in tumor suppression.

Abbreviations

BAP1

the BRCA1‐associated protein 1

DUBs

deubiquitinases

GEO

Gene Expression Omnibus

IP

immunoprecipitation

KEGG

the Kyoto Encyclopedia of Genes and Genomes

PCa

prostate cancer

PTEN

phosphatase and tensin homolog deleted on chromosome 10

qRT–PCR

quantitative real‐time polymerase chain reaction

TCGA

the Cancer Genome Atlas

USP

the ubiquitin–proteasome system

VM

vasculogenic mimicry

     

The KRAS/Lin28B axis maintains stemness of pancreatic cancer cells via the let‐7i/TET3 pathway

Increasing evidence demonstrates that Lin28B plays critical roles in numerous biological processes including cell proliferation and stemness maintenance. However, the molecular mechanisms underlying Lin28B nuclear translocation remain poorly understood. Here, we found for the first time that KRAS promoted Lin28B nuclear translocation through PKCβ, which directly bound to and phosphorylated Lin28B at S243. Firstly, we observed that Lin28B was upregulated in pancreatic cancer, contributing to cellular migration and proliferation. Furthermore, nuclear Lin28B upregulated TET3 messenger RNA and protein levels by blocking the production of mature let‐7i. Subsequently, increased TET3 expression could also promote the expression of Lin28B, thereby forming a Lin28B/let‐7i/TET3 feedback loop. Our results suggest that the KRAS/Lin28B axis drives the let‐7i/TET3 pathway to maintain the stemness of pancreatic cancer cells. These findings illuminate the distinct mechanism of Lin28B nuclear translocation and its important roles in KRAS‐driven pancreatic cancer, and have important implications for development of novel therapeutic strategies for this cancer.

Abbreviations

CCK‐8

cell counting kit‐8

CSC

cancer stem cells

IP

immunoprecipitation

MUT

mutant type

NLS

nuclear localization signal

PC

pancreatic cancer

PCSC

pancreatic cancer stem cells

PKC

protein kinase C

WT

wild‐type

     

Downregulation of Glutamine Synthetase,not glutaminolysis,is responsible for glutamine addiction in Notch1‐driven acute lymphoblastic leukemia

The cellular receptor Notch1 is a central regulator of T‐cell development, and as a consequence, Notch1 pathway appears upregulated in > 65% of the cases of T‐cell acute lymphoblastic leukemia (T‐ALL). However, strategies targeting Notch1 signaling render only modest results in the clinic due to treatment resistance and severe side effects. While many investigations reported the different aspects of tumor cell growth and leukemia progression controlled by Notch1, less is known regarding the modifications of cellular metabolism induced by Notch1 upregulation in T‐ALL. Previously, glutaminolysis inhibition has been proposed to synergize with anti‐Notch therapies in T‐ALL models. In this work, we report that Notch1 upregulation in T‐ALL induced a change in the metabolism of the important amino acid glutamine, preventing glutamine synthesis through the downregulation of glutamine synthetase (GS). Downregulation of GS was responsible for glutamine addiction in Notch1‐driven T‐ALL both in vitro and in vivo. Our results also confirmed an increase in glutaminolysis mediated by Notch1. Increased glutaminolysis resulted in the activation of the mammalian target of rapamycin complex 1 (mTORC1) pathway, a central controller of cell growth. However, glutaminolysis did not play any role in Notch1‐induced glutamine addiction. Finally, the combined treatment targeting mTORC1 and limiting glutamine availability had a synergistic effect to induce apoptosis and to prevent Notch1‐driven leukemia progression. Our results placed glutamine limitation and mTORC1 inhibition as a potential therapy against Notch1‐driven leukemia.

Abbreviations

7‐AAD

7‐Aminoactinomycin D

BPTES

bis‐2‐(5‐phenylacetamido‐1,2,4‐thiadiazol‐2‐yl)ethyl sulfide

DON

diazo‐5‐oxo‐L‐norleucine

ECAR

extracellular acidification rate

GDH

glutamate dehydrogenase

GLS

glutaminase

GS

glutamine synthetase

GSI

γ‐secretase inhibitor

MSO

L‐methionine sulfoximine

mTORC1

mammalian target of rapamycin complex 1

NICD

Notch intracellular domain

PI

propidium iodide

RAP

rapamycin

T‐ALL

T‐cell acute lymphoblastic leukemia

TCA

tricarboxylic acid

αKG

α‐ketoglutarate

     

CDH6‐activated αIIbβ3 crosstalks with α2β1 to trigger cellular adhesion and invasion in metastatic ovarian and renal cancers

Cadherin 6 (CDH6) is significantly overexpressed in advanced ovarian and renal cancers. However, the role of CDH6 in cancer metastasis is largely unclear. Here, we investigated the impact of CDH6 expression on integrin‐mediated metastatic progression. CDH6 preferentially bound to αIIbβ3 integrin, a platelet receptor scarcely expressed in cancer cells, and this interaction was mediated through the cadherin Arginine–glycine–aspartic acid (RGD) motif. Furthermore, CDH6 and CDH17 were found to interact with α2β1 in αIIbβ3^low cells. Transient silencing of CDH6, ITGA2B, or ITGB3 genes caused a significant loss of proliferation, adhesion, invasion, and lung colonization through the downregulation of SRC, FAK, AKT, and ERK signaling. In ovarian and renal cancer cells, integrin αIIbβ3 activation appears to be a prerequisite for proper α2β1 activation. Interaction of αIIbβ3 with CDH6, and subsequent αIIbβ3 activation, promoted activation of α2β1 and cell adhesion in ovarian and renal cancer cells. Additionally, monoclonal antibodies specific to the cadherin RGD motif and clinically approved αIIbβ3 inhibitors could block pro‐metastatic activity in ovarian and renal tumors. In summary, the interaction between CDH6 and αIIbβ3 regulates α2β1‐mediated adhesion and invasion of ovarian and renal cancer metastatic cells and constitutes a therapeutic target of broad potential for treating metastatic progression.     

TRIP13 promotes metastasis of colorectal cancer regardless of p53 and microsatellite instability status

Overexpression of TRIP13, a member of the AAA‐ATPase family, is linked with various cancers, but its role in metastasis is unknown in colorectal cancer (CRC). In the current study, we investigated the role TRIP13 in experimental metastasis and its involvement in regulation of WNT/β‐catenin and EGFR signaling pathways. Evaluation of formalin‐fixed paraffin‐embedded (FFPE) and frozen tissues of adenomas and CRCs, along with their corresponding normal samples, showed that TRIP13 was gradually increased in its phenotypic expression from adenoma to carcinoma and that its overexpression in CRCs was independent of patient''s gender, age, race/ethnicity, pathologic stage, and p53 and microsatellite instability (MSI) status. Moreover, liver metastases of CRCs showed TRIP13 overexpression as compared to matched adjacent liver tissues, indicating the biological relevance of TRIP13 in CRC progression and metastasis. TRIP13 knockdown impeded colony formation, invasion, motility, and spheroid‐forming capacity of CRC cells irrespective of their p53 and MSI status. Furthermore, xenograft studies demonstrated high expression of TRIP13 contributed to tumor growth and metastasis. Depletion of TRIP13 in CRC cells decreased metastasis and it was independent of the p53 and MSI status. Furthermore, TRIP13 interacted with a tyrosine kinase, FGFR4; this interaction could be essential for activation of the EGFR‐AKT pathway. In addition, we demonstrated the involvement of TRIP13 in the Wnt signaling pathway and in the epithelial–mesenchymal transition. Cell‐based assays revealed that miR‐192 and PNPT1 regulate TRIP13 expression in CRC. Additionally, RNA sequencing of CRC cells with TRIP13 knockdown identified COL6A3, TREM2, SHC3, and KLK7 as downstream targets that may have functional relevance in TRIP13‐mediated tumor growth and metastasis. In summary, our results demonstrated that TRIP13 promotes tumor growth and metastasis regardless of p53 and MSI status, and indicated that it is a target for therapy of CRC.

Abbreviations

CIN

chromosomal instability

CRC

colorectal cancer

EMT

epithelial–mesenchymal transition

FFPE

formalin‐fixed, paraffin‐embedded

LEF

lymphoid enhancer factor

MS

microsatellite

MSI

microsatellite instable

MSS

microsatellite stable

NSG

NOD/SCID/IL2γ receptor‐null

NT

nontargeting

SAC

spindle assembly checkpoint

TCF

T‐cell factor

TRIP13

thyroid hormone receptor interactor 13

UAB

University of Alabama at Birmingham

     

Circulating tumor cell detection and single‐cell analysis using an integrated workflow based on ChimeraX®‐i120 Platform: A prospective study

Circulating tumor cell (CTC) analysis holds great potential to be a noninvasive solution for clinical cancer management. A complete workflow that combined CTC detection and single‐cell molecular analysis is required. We developed the ChimeraX^®‐i120 platform to facilitate negative enrichment, immunofluorescent labeling, and machine learning‐based identification of CTCs. Analytical performances were evaluated, and a total of 477 participants were enrolled to validate the clinical feasibility of ChimeraX^®‐i120 CTC detection. We analyzed copy number alteration profiles of isolated single cells. The ChimeraX^®‐i120 platform had high sensitivity, accuracy, and reproducibility for CTC detection. In clinical samples, an average value of > 60% CTC‐positive rate was found for five cancer types (i.e., liver, biliary duct, breast, colorectal, and lung), while CTCs were rarely identified in blood from healthy donors. In hepatocellular carcinoma patients treated with curative resection, CTC status was significantly associated with tumor characteristics, prognosis, and treatment response (all P < 0.05). Single‐cell sequencing analysis revealed that heterogeneous genomic alteration patterns resided in different cells, patients, and cancers. Our results suggest that the use of this ChimeraX^®‐i120 platform and the integrated workflow has validity as a tool for CTC detection and downstream genomic profiling in the clinical setting.

Abbreviations

ADABOOST

AdaBoost classification trees

AFP

alpha‐fetoprotein

AUC

areas under the curve

BC

breast cancer

BCLC

barcelona clinic liver cancer

BHL

benign hepatic lesion

CCD

charge‐coupled device

CHB

chronic hepatitis B

CK

cytokeratin

CNA

copy number alteration

CNLC

Chinese staging for liver cancer

CRC

colorectal cancer

CTC

circulating tumor cell

CTM

circulating tumor microemboli

CV

coefficient of variation

DAPI

4’,6‐diamidine‐2’‐phenylindole dihydrochloride

EpCAM

epithelial cell adhesion molecule

FPR

false‐positive rate

GBM

stochastic gradient boosting

HCC

hepatocellular carcinoma

HD

healthy donor

ICC

intrahepatic cholangiocarcinoma

LC

liver cirrhosis

LCA

lung cancer

LOD

limit of detection

PBS

phosphate‐buffered saline

PCR

polymerase chain reaction

RF

random forest

ROC

receiver operating characteristic

SVM

support vector machines

TCGA

The Cancer Genome Atlas

TPR

true‐positive rate

TTR

time to recurrence

WBC

white blood cell

WGA

whole‐genome amplification

WGS

whole‐genome sequencing

XGB

extreme gradient boosting

     

EBP2, a novel NPM‐ALK‐interacting protein in the nucleolus,contributes to the proliferation of ALCL cells by regulating tumor suppressor p53

The oncogenic fusion protein nucleophosmin‐anaplastic lymphoma kinase (NPM‐ALK), found in anaplastic large‐cell lymphoma (ALCL), localizes to the cytosol, nucleoplasm, and nucleolus. However, the relationship between its localization and transforming activity remains unclear. We herein demonstrated that NPM‐ALK localized to the nucleolus by binding to nucleophosmin 1 (NPM1), a nucleolar protein that exhibits shuttling activity between the nucleolus and cytoplasm, in a manner that was dependent on its kinase activity. In the nucleolus, NPM‐ALK interacted with Epstein–Barr virus nuclear antigen 1‐binding protein 2 (EBP2), which is involved in rRNA biosynthesis. Moreover, enforced expression of NPM‐ALK induced tyrosine phosphorylation of EBP2. Knockdown of EBP2 promoted the activation of the tumor suppressor p53, leading to G₀/G₁‐phase cell cycle arrest in Ba/F3 cells transformed by NPM‐ALK and ALCL patient‐derived Ki‐JK cells, but not ALCL patient‐derived SUDH‐L1 cells harboring p53 gene mutation. In Ba/F3 cells transformed by NPM‐ALK and Ki‐JK cells, p53 activation induced by knockdown of EBP2 was significantly inhibited by Akt inhibitor GDC‐0068, mTORC1 inhibitor rapamycin, and knockdown of Raptor, an essential component of mTORC1. These results suggest that the knockdown of EBP2 triggered p53 activation through the Akt‐mTORC1 pathway in NPM‐ALK‐positive cells. Collectively, the present results revealed the critical repressive mechanism of p53 activity by EBP2 and provide a novel therapeutic strategy for the treatment of ALCL.

Abbreviations

ALCL

anaplastic large‐cell lymphoma

EBP2

EBNA1‐binding protein 2

IMT

inflammatory myofibroblastic tumors

mTOR

mechanistic target of rapamycin

mTORC1

mTOR complex 1

NoLS

nucleolar localization signal

NPM1

nucleophosmin 1

NPM‐ALK

nucleophosmin‐anaplastic lymphoma kinase

NSCLC

non‐small cell lung cancer

TPM3

tropomyosin 3

     

Autophagy activation and SREBP‐1 induction contribute to fatty acid metabolic reprogramming by leptin in breast cancer cells

Leptin, a hormone predominantly derived from adipose tissue, is well known to induce growth of breast cancer cells. However, its underlying mechanisms remain unclear. In this study, we examined the role of reprogramming of lipid metabolism and autophagy in leptin‐induced growth of breast cancer cells. Herein, leptin induced significant increase in fatty acid oxidation‐dependent ATP production in estrogen receptor‐positive breast cancer cells. Furthermore, leptin induced both free fatty acid release and intracellular lipid accumulation, indicating a multifaceted effect of leptin in fatty acid metabolism. These findings were further validated in an MCF‐7 tumor xenograft mouse model. Importantly, all the aforementioned metabolic effects of leptin were mediated via autophagy activation. In addition, SREBP‐1 induction driven by autophagy and fatty acid synthase induction, which is mediated by SREBP‐1, plays crucial roles in leptin‐stimulated metabolic reprogramming and are required for growth of breast cancer cell, suggesting a pivotal contribution of fatty acid metabolic reprogramming to tumor growth by leptin. Taken together, these results highlighted a crucial role of autophagy in leptin‐induced cancer cell‐specific metabolism, which is mediated, at least in part, via SREBP‐1 induction.

Abbreviations

2‐DG

2‐deoxyglucose

3‐MA

3‐methyladenine

ACC‐1

acetyl‐CoA carboxylase 1

ACLY

ATP citrate lyase

ER

estrogen receptor

FADS1

fatty acid desaturase 1

FADS2

fatty acid desaturase 2

FAO

fatty acid oxidation

FAS

fatty acid synthesis

FASN

fatty acid synthase

FFA

free fatty acid

IHC

immunohistochemistry

SCD‐1

stearoyl‐CoA desaturase‐1

SREBP‐1

sterol regulatory element‐binding protein 1