Impaired expression of proteasome subunits and human leukocyte antigens class I in human colon cancer cells.
OBJECTIVE
The presentation of human leukocyte antigens (HLA) class I requires the coordinated expression of numerous components involved in antigen processing and antigen presentation. Tumor cells may alter the expression of these components to decrease HLA class I expression, allowing them to escape immune surveillance. The aim of this study is to investigate the expressions of these components, including proteasome subunits, and their involvement in the expression of HLA class I in human colon cancer cells.


METHODS
Four human colon cancer cell lines, HCT116, SW403, LoVo and DLD-1, were used to examine the expression of HLA class I by flow cytometry. Reverse transcription-polymerase chain reaction was performed to assess the expression of beta2-microglobulin, heavy chains, transporter subunits, immunoproteasomes subunits and proteasome activator 28 (PA28) subunits.


RESULTS
Human leukocyte antigen class I was expressed highly in HCT116 and SW403 cells and weakly in LoVo cells, but was not expressed in DLD-1 cells. The DLD-1 cells were deficient in the expression of proteasome subunits including low molecular weight polypeptide proteasome subunit 2 (LMP2), multicatalytic endopeptidase complex-like-1 (MECL-1), PA28alpha and PA28beta, whereas other HLA class I-expressing cell lines expressed all components tested. gamma-Interferon (IFN-gamma) treatment of DLD-1 cells restored the expression of LMP2, MECL-1 and PA28beta, but not the expression of HLA class I. Enforced expression of PA28alpha induced the expression of HLA class I in IFN-gamma-treated DLD-1 cells, but not in untreated DLD-1 cells.


CONCLUSIONS
These results suggest that the impaired expression of proteasome subunits is involved in the loss of HLA class I expression in human colon cancer cells.
Miyagi
Takuya
T
Departments of Molecular Therapeutics, Internal Medicine and Therapeutics and General Medicine, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
Tatsumi
Tomohide
T
Takehara
Tetsuo
T
Kanto
Tatsuya
T
Kuzushita
Noriyoshi
N
Sugimoto
Yoshiko
Y
Jinushi
Masahisa
M
Kasahara
Akinori
A
Sasaki
Yutaka
Y
Hori
Masatsugu
M
Hayashi
Norio
N
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000818:Animals; D003110:Colonic Neoplasms / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D005434:Flow Cytometry; D015234:HLA-A Antigens / Q000235:genetics; D015235:HLA-B Antigens / Q000235:genetics; D015236:HLA-C Antigens / Q000235:genetics; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D009124:Muscle Proteins; D046988:Proteasome Endopeptidase Complex; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D014407:Tumor Cells, Cultured; D001613:beta 2-Microglobulin / Q000235:genetics
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters; D015234:HLA-A Antigens; D015235:HLA-B Antigens; D015236:HLA-C Antigens; D015395:Histocompatibility Antigens Class I; D007527:Isoenzymes; D009097:Multienzyme Complexes; D009124:Muscle Proteins; D012333:RNA, Messenger; C073119:TAP1 protein, human; C486171:Tap1 protein, mouse; C489516:Tap2 protein, mouse; D001613:beta 2-Microglobulin; C071692:TAP2 protein, human; D007371:Interferon-gamma; D003546:Cysteine Endopeptidases; C486207:PSME2 protein, human; D046988:Proteasome Endopeptidase Complex