Analysis of IL6‑protein complexes in chondrosarcoma

  • Authors:
    • Karina Galoian
    • Shihua Luo
    • Parthik Patel
  • View Affiliations

  • Published online on: November 10, 2017     https://doi.org/10.3892/br.2017.1016
  • Pages: 91-98
Metrics: HTML 0 views | PDF 0 views     Cited By (CrossRef): 0 citations

Abstract

Cytokines produced in the tumour microenvironment serve important roles in cancer pathogenesis or in the supression of disease progression. Metastatic chondrosarcoma is a cancer of the cartilage, and our group previously reported from a human ELISA assay that interleukin 6 (IL6) expression in JJ012 chondrosarcoma cells was 86‑fold lower than that in C28 chondrocytes, indicating its role as an anti‑inflammatory and anti‑tumorigenic factor. Additionally, to the best of our knowledge, the study was the first to demonstrate downregulation of IL6 in a human chondrosarcoma cell line. To fully elucidate the effect of this IL6 downregulation, it is important to identify protein complexes and components that bind IL6 and potentially affect its gene expression directly or indirectly. To investigate IL6‑protein interactions leading to these differences in IL6 expression, the current study performed a gel retardation electrophoretic mobility shift assay (EMSA), followed by 2D gel phoresis, in‑gel trypsin digestion and proteomic mass spectral analysis. The results indicated a presence of ubiquitination enzymes in C28 chondrocytes, while none were identified in JJ012 chondrosarcoma cells. While it seems counterintuitive, it may be that the absence of ubiquitination of certain factors leads to the downregulation of IL6 expression in human chondrosarcoma. Therefore, dysregulated ubiquitination may be among the possible mechanisms for the markedly reduced IL6 expression in chondrosarcoma.

Introduction

Chronic inflammation and cytokines serve important roles in cancer. Cytokines are secreted proteins that are involved in immune response, cell communications and, depending on cellular context, may be anti or pro-tumorigenic (1). Chondrosarcoma is a cancer of the cartilage with systemic involvement. It is a common primary bone malignancy, accounting for 25% of bone sarcomas (2). Tumors typically develop in the pelvis, long bones and spine, as well as the larynx, head and neck (3). More aggressive forms of chondrosarcoma are characterized by early metastasis, and the metastasis rate of primary chondrosarcoma may reach 42%, and up to 86% in patients with local recurrence (4).

Chondrosarcoma does not typically respond to conventional therapies such as chemotherapy and radiation, which necessitates the identification of novel alternative therapies (27). The etiological factors and molecular pathways leading to the transformation of mesenchymal cells into sarcoma cells are unknown; therefore, understanding of the involvement of certain cytokines in failed differentiation programs leading to cancer or lost tumor suppressive functions is critical and of current interest (1). A previous study by our group reported from a human ELISA assay that the expression of interleukin 6 (IL6) in JJ012 chondrosarcoma cells was 86-fold lower than that in C28 chondrocytes, indicating it to be an anti-inflammatory and antitumorigenic factor (7). Furthermore, downregulation of IL6 has been reported for a number of tumor types, including undifferentiated thyroid carcinoma and thyroid cancer (810). To investigate IL6-protein interactions leading to these differences in IL6 expression, the present study assessed IL6 complexes in JJ012 and C28 cells through nuclear extraction and an electrophoretic mobility shift assay (EMSA), followed by 2D gel phoresis, in-gel trypsin digestion (11) and proteomic mass spectrometry (MS) analysis.

Materials and methods

Cell culture

Complete growth medium for human JJ012 chondrosarcoma cells were obtained from the laboratory of Dr Joel Block (Rush University Medical Centre, Chicago, IL, USA) and for C28 chondrocytes from the laboratory of Dr Sean Scully (University of Miami, Miami, FL, USA) comprised of the following: Dulbecco's modified Eagle's medium supplemented with F12, 10% fetal bovine serum (Thermo Fisher Scientific, Inc., Waltham, MA, USA), 25 µg/ml ascorbic acid, 100 ng/ml insulin, 100 nM hydrocortisone and 1% penicillin/streptomycin (Sigma-Aldrich; Merck KGaA, Darmstadt, Germany). Cultures were incubated for 24 h in a humidified 5% CO2 incubator at 37°C.

Nuclear extraction and EMSA, and SDS-PAGE and IL6 oligonucleotide forward and reverse sequence synthesis

These procedures were performed as described in our recent study (7).

2D gel electrophoresis and in-gel trypsin digestion

The procedures were performed according to previously described methods (11) with slight modifications.

For the 2D gel electrophoresis (modified 2D EMSA), a gel shift EMSA kit (cat. no. 37341) from Active Motif, Inc. (Carlsbad, CA, USA) was used. The procedures from steps 1 to 5 as detailed in the EMSA kit manual were performed according to manufacturer's instructions. From step 6, gel transfer was performed to polyvinylidene difluoride membranes. For blot extraction, the membrane was divided into eight vertical slices and soaked twice in 1 ml extraction buffer (50 mM Tris-HCL, pH 9, 50 mM dithiothreitol and 0.5% Tween-20) for 2 h at room temperature with gentle shaking. The detergent was then removed using a Pierce Detergent spin column from Thermo Fisher Scientific, Inc. (cat. no. 87779), as instructed by the column manufacturer. The proteins in the extract were concentrated using Amicon Ultra 2 Centrifugal Filters with 10 kDa cut-off (cat. no. UGC501008; EMD Millipore, Billerica, MA, USA). The concentrated proteins were separated by SDS-PAGE as described previously (7).

For in-gel trypsin digestion, gel bands from the SDS PAGE were vertically cut into ten equal slices (1×1 mm). The gel pieces were dehydrated with acetonitrile (ACN) (Sigma-Aldrich; Merck KGaA), dried for 30 min and vacuumed for 10 min at 20°C, reduced in 150 µl 10 mM dithiothreitol in 100 mM ACN at 56°C for 1 h, and then alkylated with 50 mM iodoacetamide (Sigma-Aldrich; Merck KGaA) in 100 mM ACN at room temperature for 1 h in the dark. Following these washing and dehydration steps, the gel cubes were digested in 30 µl trypsin (20 ng/µl in 25 mM ACN) at 37°C overnight. The trypsin-digested peptides were subsequently extracted with 40 µl 5% trifluroacetic acid (Pierce; Thermo Fisher Scientific, Inc.) in 50% ACN for 1 h at room temperature. Finally, two rounds of drying by speed vacuum for 1 h at 45°C and resuspension in 20 µl 0.1% trifluoriacetic acid were performed, followed by MS analysis.

Proteomic MS

Digestion mixtures were loaded onto a reversed-phase fused-silica capillary emitter column [75 µm inner diameter × 15 cm, packed with Acclaim PepMap RSLC C18, 2 µm, 100 Å (Thermo Fisher Scientific, Inc.)] connected to a precolumn [Acclaim PepMap 100, 75 µm × 2 cm, packed with nanoviper C18, 3 µm, 100 Å (Thermo Fisher Scientific, Inc.)]. For ultra high performance liquid chromatography (UHPLC), the column and precolumn were connected in-line to an Easy Nano LC 1000 UHPLC system (Thermo Fisher Scientific, Inc.) and were equilibrated and washed with water [Optima LC/MS Grade (W6-1) from Fisher Chemical; Thermo Fisher Scientific, Inc.]. Solvent A and solvent B were water and ACN [Fisher Chemical Optima LC/MS Grade (A955-1L); Thermo Fisher Scientific, Inc.] respectively. The peptides were gradient-eluted following application of solvent B from 2 to 98% at a flow of 350 nl/min for 1 h at 20°C, eluting 300 µl at a maximum pressure of 980 bar. Following elution, the samples were resuspended in 2% ACN, and analyzed with a Q Exactive Orbitrap Mass Spectrometer (Thermo Fisher Scientific, Inc.). The column was fixed to a Nanospray Flex ion source from Thermo Fisher Scientific, Inc. Sheath, auxiliary and sweep gas were set to zero, and the run was in positive mode. The mass spectrometer was operated in data-dependent mode, with an automatic gain control target of 1e6 for full MS and 2e5 for data dependent-MS/MS. The isolation window was fixed to 1.3 m/z with a normalized collision energy of 28 eV. Bioinformatics analysis was performed using Thermo Proteome Discoverer v1.4 (Thermo Fisher Scientific, Inc.). Data were processed against Homo sapiens data in the Uniprot database (http://uniprot.org), allowing two missed cleavages, 10 ppm as a precursor mass tolerance and 0.02 Da for fragment mass tolerance.

Results

MS analysis of IL6-protein complexes

Tables I and II list the proteins complexed with IL6 identified by proteomic MS analysis in C28 chondrocytes and JJ012 chondrosarcoma cells, respectively. A population of ubiquitination enzymes (<2%) were detected in C28 chondrocytes, while none were expressed in JJ012 chondrosarcoma cells. Among these enzymes were enzymes of ubiquitination machinery, namely E3 ubiquitin ligases, including E3 ubiquitin-protein ligase SH3 domain-containing ring finger 1, E3 ubiquitin-protein ligase ring finger protein 169 and E3 SUMO-protein ligase Ran-binding protein 2, as well as ubiquitin carboxyl-terminal hydrolase 33 (USP33).

Table I.

Mass spectrometry analysis of proteins complexed with IL6 in human C28 chondrocytes.

Table I.

Mass spectrometry analysis of proteins complexed with IL6 in human C28 chondrocytes.

Protein nameAccession no.
Ubiquitin carboxyl-terminal hydrolase 33 (fragment)OS=Homo sapiens GN=USP33 PE=1 SV=7 - [E9PP47_HUMAN]
Ubiquitin-60S ribosomal protein L40OS=Homo sapiens GN=UBA52 PE=1 SV=2 - [RL40_HUMAN]
Sterile alpha motif domain containing 11 splice variant ASV43OS=Homo sapiens GN=SAMD11 PE=2 SV=1 - [I7G293_HUMAN]
Dapper homolog 1 (fragment)OS=Homo sapiens GN=DACT1 PE=1 SV=1 - [C9JGV7_HUMAN]
Sarcoma antigen NY-SAR-29 (fragment)OS=Homo sapiens PE=2 SV=1 - [Q86WF2_HUMAN]
TBC1 domain family member 15 (fragment)OS=Homo sapiens GN=TBC1D15 PE=1 SV=1 - [F8VV61_HUMAN]
cDNA FLJ61508, moderately similar to ATP-binding cassette sub-family B member 6, mitochondrialOS=Homo sapiens PE=2 [B4E055_HUMAN]
Beta chimaerin isoform B2-CHNdel ex2-8,11–12OS=Homo sapiens GN=CHN2 PE=2 SV=1 - [B3VCF8_HUMAN]
40S ribosomal protein S14OS=Homo sapiens GN=RPS14 PE=1 SV=3 - [RS14_HUMAN]
TenascinOS=Homo sapiens GN=TNC PE=1 SV=1 - [F5H7V9_HUMAN]
Polypeptide N-acetylgalactosaminyltransferase 7 (fragment)OS=Homo sapiens GN=GALNT7 PE=2 SV=1 - [Q68VJ4_HUMAN]
DnaJ homolog subfamily B member 11 (fragment)OS=Homo sapiens GN=DNAJB11 PE=1 SV=7 - [H7C2Y5_HUMAN]
Profilaggrin (fragment)OS=Homo sapiens PE=4 SV=1 - [Q01212_HUMAN]
60S ribosomal protein L27aOS=Homo sapiens GN=RPL27A PE=1 SV=2 - [RL27A_HUMAN]
Protein FAM117BOS=Homo sapiens GN=FAM117B PE=1 SV=2 - [F117B_HUMAN]
Heterogeneous nuclear ribonucleoprotein K (fragment)OS=Homo sapiens GN=HNRNPK PE=1 SV=1 - [Q5T6W2_HUMAN]
Neuropilin 2OS=Homo sapiens GN=NRP2 PE=2 SV=1 - [B7ZL68_HUMAN]
Tubulin alpha-8 chain (fragment)OS=Homo sapiens GN=TUBA8 PE=1 SV=1 - [C9J2C0_HUMAN]
KAT8 regulatory NSL complex subunit 1OS=Homo sapiens GN=KANSL1 PE=1 SV=1 - [A0A0G2JQF5_HUMAN]
Putative EGF-like and EMI domain-containing protein 1OS=Homo sapiens GN=EGFEM1P PE=5 SV=1 - [EGFEM_HUMAN]
CDNA FLJ25460 fis, clone TST09046OS=Homo sapiens GN=hCG_2004368 PE=2 SV=1 - [Q96LI4_HUMAN]
Ribosomal protein S6 kinase alpha-5OS=Homo sapiens GN=RPS6KA5 PE=1 SV=1 - [KS6A5_HUMAN]
60S ribosomal protein L7a (fragment)OS=Homo sapiens GN=RPL7A PE=1 SV=1 - [Q5T8U3_HUMAN]
Serine/threonine-protein kinase 35OS=Homo sapiens GN=STK35 PE=1 SV=2 - [STK35_HUMAN]
cDNA FLJ45139 fis, clone BRAWH3039623OS=Homo sapiens PE=2 SV=1 - [Q6ZSX8_HUMAN]
Elongation factor 1-alpha 1OS=Homo sapiens GN=EEF1A1 PE=1 SV=1 - [EF1A1_HUMAN]
E3 ubiquitin-protein ligase SH3RF1OS=Homo sapiens GN=SH3RF1 PE=1 SV=2 - [SH3R1_HUMAN]
Keratin, type II cytoskeletal 1 PE=1 SV=6 - Solute carrier family 45 member 4OS=Homo sapiens GN=KRT1 [K2C1_HUMAN]
OS=Homo sapiens GN=SLC45A4 PE=1 SV=2 - [S45A4_HUMAN]
Dolichyl-diphosphooligosaccharide-protein glycosyltransferase subunit 1OS=Homo sapiens PE=2 SV=1 - [B4DNJ5_HUMAN]
WD repeat-containing protein 87OS=Homo sapiens GN=WDR87 PE=1 SV=2 - [E7ESW6_HUMAN]
Prolow-density lipoprotein receptor-related protein 1OS=Homo sapiens GN=LRP1 PE=1 SV=2 - [LRP1_HUMAN]
78 kDa glucose-regulated proteinOS=Homo sapiens GN=HSPA5 PE=1 SV=2 - [GRP78_HUMAN]
cDNA FLJ46818 fis, clone TRACH3038399, highly similar to eukaryotic translation initiation factor 2-alpha kinase 3(EC 2.7.11.1) [B3KY45_HUMAN]
E3 SUMO-protein ligase RanBP2OS=Homo sapiens GN=RANBP2 PE=1 SV=2 - [RBP2_HUMAN]
Interferon receptor 1 isoform 4OS=Homo sapiens PE=2 SV=1 - [A0A0U1SHW4_HUMAN]
cDNA FLJ16282 fis, clone NT2RI3005416, highly similar to F-box only protein 18 (EC 3.6.1.-)OS=Homo sapiens PE=2 SV=1 - [B3KV95_HUMAN]
VinculinOS=Homo sapiens GN=VCL PE=1 SV=4 - [VINC_HUMAN]
Chymotrypsinogen BOS=Homo sapiens GN=CTRB1 PE=2 SV=1 - [CTRB1_HUMAN]
MAP7 domain-containing protein 3 (fragment)OS=Homo sapiens GN=MAP7D3 PE=1 SV=1 - [A0A0A0MRP0_HUMAN]
Enolase 4OS=Homo sapiens GN=ENO4 PE=4 SV=1 - [A6NI74_HUMAN]
Myozenin-2OS=Homo sapiens GN=MYOZ2 PE=1 SV=1 - [MYOZ2_HUMAN]
Docking protein 6OS=Homo sapiens GN=DOK6 PE=1 SV=1 - [DOK6_HUMAN]
Collagen alpha-1(XIV) chainOS=Homo sapiens GN=COL14A1 PE=1 SV=3 - [COEA1_HUMAN]
Zinc finger protein 605OS=Homo sapiens GN=ZNF605 PE=2 SV=1 - [ZN605_HUMAN]
E3 ubiquitin-protein ligase RNF169OS=Homo sapiens GN=RNF169 PE=1 SV=2 - [RN169_HUMAN]
Keratin, type I cytoskeletal 9OS=Homo sapiens GN=KRT9 PE=1 SV=3 - [K1C9_HUMAN]
ATP synthase subunit alpha, mitochondrialOS=Homo sapiens GN=ATP5A1 PE=1 SV=1 - [ATPA_HUMAN]

Table II.

Mass spectrometry analysis of proteins complexed with IL6 in human JJ012 chondrosarcoma cells.

Table II.

Mass spectrometry analysis of proteins complexed with IL6 in human JJ012 chondrosarcoma cells.

Protein nameAccession no.
Nephronectin (fragment)OS=Homo sapiens GN=NPNT PE=4 SV=1 - [H0YA60_HUMAN]
Keratin-associated protein 19-1OS=Homo sapiens GN=KRTAP19-1 PE=2 SV=2 - [KR191_HUMAN]
Ubiquitin-60S ribosomal protein L40OS=Homo sapiens GN=UBA52 PE=1 SV=2 - [RL40_HUMAN]
Epithelial cell-transforming sequence 2 oncogene-like (fragment)OS=Homo sapiens GN=ECT2L PE=4 SV=1 - [B7ZBI6_HUMAN]
Sodium/potassium-transporting ATPase subunit beta-3OS=Homo sapiens GN=ATP1B3 PE=1 SV=1 - [C9J6S2_HUMAN]
TBC1 domain family member 15 (fragment)OS=Homo sapiens GN=TBC1D15 PE=1 SV=1 - [F8VV61_HUMAN]
cDNA FLJ61508, moderately similar to ATP-binding cassette sub-family B member 6, mitochondrialOS=Homo sapiens PE=2 SV=1 [B4E055_HUMAN]
ATP-binding cassette sub-family B member 8, mitochondrialOS=Homo sapiens GN=ABCB8 PE=4 SV=1 - [F8WC43_HUMAN]
Heterogeneous nuclear ribonucleoprotein C-like 2OS=Homo sapiens GN=HNRNPCL2 PE=4 SV=1 - [A0A0G2JNQ3_HUMAN]
Putative EGF-like and EMI domain-containing protein 1OS=Homo sapiens GN=EGFEM1P PE=5 SV=1 - [EGFEM_HUMAN]
cDNA FLJ13888 fis, clone THYRO1001584OS=Homo sapiens PE=2 SV=1 - [Q9H880_HUMAN]
Phospholysine phosphohistidine inorganic pyrophosphate phosphataseOS=Homo sapiens GN=LHPP PE=1 SV=2 - [LHPP_HUMAN]
Uncharacterized protein (fragment)OS=Homo sapiens PE=4 SV=2 - [H7C1N6_HUMAN]
40S ribosomal protein S14OS=Homo sapiens GN=RPS14 PE=1 SV=3 - [RS14_HUMAN]
Chromosome 5 open reading frame 4, isoform CRA_aOS=Homo sapiens GN=C5orf4 PE=2 SV=1 - [Q9UHK3_HUMAN]
60S ribosomal protein L21OS=Homo sapiens GN=RPL21 PE=1 SV=1 - [G3V1B3_HUMAN]
S100P binding protein isoform 2OS=Homo sapiens GN=S100PBP PE=2 SV=1 - [A0A0S2Z5S2_HUMAN]
cDNA FLJ26027 fis, clone PNC04328, highly similar to Homo sapiens translocase of outer mitochondrial membrane 34(TOMM340) [Q6ZPD_HUMAN]
cDNA FLJ56407, highly similar to SLIT-ROBO Rho GTPase-activating protein 2OS=Homo sapiens PE=2 SV=1 - [B4DFE5_HUMAN]
60S ribosomal protein L27aOS=Homo sapiens GN=RPL27A PE=1 SV=2 - [RL27A_HUMAN]
Dolichyl-diphosphooligosaccharide-protein glycosyltransferase subunit 1OS=Homo sapiens PE=2 SV=1 - [B4DL99_HUMAN]
Neuropilin 2OS=Homo sapiens GN=NRP2 PE=2 SV=1 - [B7ZL68_HUMAN]
60S ribosomal protein L31OS=Homo sapiens GN=RPL31 PE=1 SV=1 - [RL31_HUMAN]
Protein spinster homolog 2OS=Homo sapiens GN=SPNS2 PE=1 SV=2 - [SPNS2_HUMAN]
V-type proton ATPase proteolipid subunitOS=Homo sapiens GN=ATP6V0C PE=1 SV=1 - [H3BNI4_HUMAN]
cDNA FLJ78084, highly similar to Homo sapiens cell division cycle associated 8, mRNAOS=Homo sapiens PE=2 SV=1 - [A8K7A2_HUMAN]
Protein PMF1-BGLAPOS=Homo sapiens GN=PMF1-BGLAP PE=4 SV=1 - [A0A087WT04_HUMAN]
Nuclear factor of-activated T-cells, cytoplasmic 4 (fragment)OS=Homo sapiens GN=NFATC4 PE=1 SV=7 - [G3V5H0_HUMAN]
Scavenger receptor class F member 1OS=Homo sapiens GN=SCARF1 PE=1 SV=1 - [A0A0A0MR54_HUMAN]
m7GpppN-mRNA hydrolase (fragment)OS=Homo sapiens GN=DCP2 PE=1 SV=2 - [H0Y9T5_HUMAN]
Heterogeneous nuclear ribonucleoprotein K (fragment)OS=Homo sapiens GN=HNRNPK PE=1 SV=1 - [Q5T6W2_HUMAN]
60S ribosomal protein L7a (fragment)OS=Homo sapiens GN=RPL7A PE=1 SV=1 - [Q5T8U3_HUMAN]
Elongation factor 1-alpha 1OS=Homo sapiens GN=EEF1A1 PE=1 SV=1 - [EF1A1_HUMAN]
78 kDa glucose-regulated proteinOS=Homo sapiens GN=HSPA5 PE=1 SV=2 - [GRP78_HUMAN]
Zinc finger protein 90 homologOS=Homo sapiens GN=ZFP90 PE=1 SV=2 - [ZFP90_HUMAN]
Putative uncharacterized protein PCYOX1 (fragment)OS=Homo sapiens GN=PCYOX1 PE=4 SV=1 - [Q584P1_HUMAN]
G-protein-signaling modulator 1OS=Homo sapiens GN=GPSM1 PE=1 SV=2 - [GPSM1_HUMAN]
VinculinOS=Homo sapiens GN=VCL PE=1 SV=4 - [VINC_HUMAN]
DNA repair protein REV1OS=Homo sapiens GN=REV1 PE=2 SV=1 - [A1L461_HUMAN]
CDNA FLJ25612 fis, clone STM01228OS=Homo sapiens PE=2 SV=1 - [Q8N1H3_HUMAN]
Zinc finger protein 92 homologOS=Homo sapiens GN=ZFP92 PE=2 SV=3 - [ZFP92_HUMAN]
Leucine-rich repeat-containing protein 59OS=Homo sapiens GN=LRRC59 PE=1 SV=1 - [LRC59_HUMAN]
KN motif and ankyrin repeat domain-containing protein 2OS=Homo sapiens GN=KANK2 PE=1 SV=1 - [KANK2_HUMAN]
Retrotransposon-derived protein PEG10OS=Homo sapiens GN=PEG10 PE=1 SV=1 - [A0A087WZG9_HUMAN]
Fibrillin-1OS=Homo sapiens GN=FBN1 PE=1 SV=3 - [FBN1_HUMAN]
Anthrax toxin receptor 2OS=Homo sapiens GN=ANTXR2 PE=1 SV=1 - [J3KPY9_HUMAN]
ATP synthase subunit alpha, mitochondrialOS=Homo sapiens GN=ATP5A1 PE=1 SV=1 - [ATPA_HUMAN]
ADAM9 proteinOS=Homo sapiens GN=ADAM9 PE=1 SV=1 - [A0AVL1_HUMAN]
cDNA FLJ50932, highly similar to Zinc finger protein basonuclin-1OS=Homo sapiens PE=2 SV=1 - [B7Z885_HUMAN]
Vigilin (fragment)OS=Homo sapiens GN=HDLBP PE=1 SV=1 - [H7BZC3_HUMAN]
Alpha-protein kinase 1OS=Homo sapiens GN=ALPK1 PE=2 SV=3 - [ALPK1_HUMAN]
Neuroblast differentiation-associated protein AHNAKOS=Homo sapiens GN=AHNAK PE=1 SV=2 - [AHNK_HUMAN]
Zinc finger protein ZFP69OS=Homo sapiens GN=ZFP69 PE=2 SV=2 - [ZFP69_HUMAN]
DNA polymerase epsilon catalytic subunit AOS=Homo sapiens GN=POLE PE=1 SV=5 - [DPOE1_HUMAN]
cDNA FLJ58382, highly similar to Zinc finger protein 8OS=Homo sapiens PE=2 SV=1 - [B4DSF4_HUMAN]
Chymotrypsinogen BOS=Homo sapiens GN=CTRB1 PE=2 SV=1 - [CTRB1_HUMAN]
Probable ATP-dependent RNA helicase DDX46OS=Homo sapiens GN=DDX46 PE=1 SV=2 - [DDX46_HUMAN]
cDNA FLJ54652, highly similar to Homo sapiens podocan (PODN), mRNAOS=Homo sapiens PE=2 SV=1 - [B4DUY6_HUMAN]
Myozenin-2OS=Homo sapiens GN=MYOZ2 PE=1 SV=1 - [MYOZ2_HUMAN]
Thyroid adenoma-associated proteinOS=Homo sapiens GN=THADA PE=1 SV=1 - [THADA_HUMAN]
CLIP-associating protein 2OS=Homo sapiens GN=CLASP2 PE=1 SV=1 - [E7ERI8_HUMAN]
Calcium/calmodulin-dependent protein kinase II alphaOS=Homo sapiens GN=CAMK2A PE=2 SV=1 - [Q8IWE0_HUMAN]
Zinc finger protein 605OS=Homo sapiens GN=ZNF605 PE=2 SV=1 - [ZN605_HUMAN]
Far upstream element-binding protein 2OS=Homo sapiens GN=KHSRP PE=1 SV=4 - [FUBP2_HUMAN]
Putative uncharacterized protein XRCC5 (fragment)OS=Homo sapiens GN=XRCC5 PE=4 SV=1 - [Q53T09_HUMAN]
Probable threonine-tRNA ligase 2, cytoplasmicOS=Homo sapiens GN=TARSL2 PE=1 SV=1 - [SYTC2_HUMAN]
Translation initiation factor IF-2, mitochondrialOS=Homo sapiens GN=MTIF2 PE=1 SV=2 - [IF2M_HUMAN]
DystoninOS=Homo sapiens GN=DST PE=1 SV=1 - [F8W9J4_HUMAN]
cDNA FLJ76304, highly similar to Homo sapiens ADAM metallopeptidase with thrombospondin type 1 motif, 4 (ADAMTS4), mRNAOS=Homo sapiens [A8K6A8_HUMAN]
Polycystic kidney disease protein 1-like 1OS=Homo sapiens GN=PKD1L1 PE=1 SV=1 - [PK1L1_HUMAN]
Centrosomal protein KIAA1731OS=Homo sapiens GN=KIAA1731 PE=2 SV=4 - [K1731_HUMAN]
Ankyrin-3OS=Homo sapiens GN=ANK3 PE=1 SV=3 - [ANK3_HUMAN]
ATP2B2 variant protein (fragment)OS=Homo sapiens GN=ATP2B2 variant protein PE=2 SV=1 - [Q4LE63_HUMAN]

Discussion

Downregulation of IL6 expression has been observed in different tumors and is disease specific, though the cause remains unknown. Previous identification of significant downregulation of IL6 in human JJ012 chondrosarcoma cells compared with C28 chondrocytes prompted the current investigation into the mechanisms of this downregulation. In chondrosarcoma, IL6 may serve as an anti-inflammatory and anti-tumorigenic factor, based on our previous data that IL6 was downregulated by 86-fold in human chondrosarcoma compared with human C28 chondrocytes (7), indicating the possibility of a program in tumor cells with the ability to repress IL6 expression.

In the present study, a gel shift assay indicated the presence of IL6-protein complexes in C28 chondrocytes and JJ012 chondrosarcoma cells (data not shown), because we previously demonstrated (7). 2D gel electrophoresis and in-gel trypsin digestion of IL6 bands were subsequently performed to identify the IL6-protein complexes and the mechanisms involved in C28 and JJ012 cells by MS. The MS analysis detected presence of E3 ubiquitin protein ligases and USP33 hydrolase complexed with IL6 in C28 chondrocytes. Although this ligase machinery comprised a small percentage of the total proteins identified, which were overlapping between the C28 and JJ012 groups or unidentified proteins in general, this result is noteworthy, as no ubiquitination enzymes were identified in JJ012 human chondrosarcoma cells. While there is substantial data on the antitumorigenic effect of IL6 in other tumors, including undifferentiated thyroid carcinoma, thyroid cancer and bladder carcinoma (710,12), to the best of our knowledge, this is the first report on the potential antitumorigenic and anti-inflammatory role of IL6 in a human chondrosarcoma cell line.

It appeared inconsistent that ubiquitination machinery was prevalent in C28 cells and lacking in JJ012 cells, considering that ubiquitination generally targets proteins to proteosomal degradation, and that our previous results indicated significant downregulation of IL6 in JJ012 cells compared with C28 chondrocytes (5). However, it is possible that the absence of ubiquitination of certain unknown factors, to be determined in future studies, in JJ012 cells may lead to this downregulation of IL6.

Future in vivo experiments utilizing IL6 overexpression or knockdown in xenografts models may aid to elucidate the mechanisms of IL6 in human chondrosarcoma cells, and verify its antitumorigenic property and involvement in the process of differentiation. Following confirmation of the potential anti-proliferative function of IL6 in vivo, the next challenge will be ‘targeting the absence’ design experiments to investigate why there is downregulation of ubiquitination in chondrosarcoma, as well as the underlying mechanisms involved in this phenomena. A key approach will be to pursue studies on the posttranscriptional regulation of E3 ubiquitin ligase by miRNAs.

In conclusion, dysregulated ubiquitination may be a possible mechanism by which tumors exhibit the ability to repress IL6 expression. It is established that the microenvironments of cells, tissues and organs define gene expression. It has been demonstrated that IL6 is markedly downregulated in human chondrosarcoma cells compared with normal chondrocytes. This complies with the potential tumorigenicity and anti-inflammatory function of IL6 in chondrosarcoma. Therefore, identification of the mechanisms leading to IL6 downregulation may be important from a theoretical perspective and also for clinical practice, particularly regarding possible gene therapy applications.

Acknowledgements

The authors are thankful to Professor Sanjoy K. Bhattacharya and Ms. Maria del Carmen Piqueras from the Ophthalmology Mass Spectrometry shared instrument Core Facility of the University of Miami. The funding for mass spectrometry was provided by the National Eye Institute Ophtalmology Core Facility (grant no. P30EY14801; principal investigator Dr Vittorio Porciatti) and an unrestricted grant from Research to Prevent Blindness to the University of Miami. The study was also supported in part by the Ratcliffe Foundation of the Miami Center of Orthopedic Research and Education.

References

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January 2018
Volume 8 Issue 1

Print ISSN: 2049-9434
Online ISSN:2049-9442

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Copy and paste a formatted citation
APA
Galoian, K., Luo, S., & Patel, P. (2018). Analysis of IL6‑protein complexes in chondrosarcoma. Biomedical Reports, 8, 91-98. https://doi.org/10.3892/br.2017.1016
MLA
Galoian, K., Luo, S., Patel, P."Analysis of IL6‑protein complexes in chondrosarcoma". Biomedical Reports 8.1 (2018): 91-98.
Chicago
Galoian, K., Luo, S., Patel, P."Analysis of IL6‑protein complexes in chondrosarcoma". Biomedical Reports 8, no. 1 (2018): 91-98. https://doi.org/10.3892/br.2017.1016