Down-regulation of HLA class I antigen in human papillomavirus type 16 E7 expressing HaCaT cells: correlate with TAP-1 expression.
OBJECTIVE
High-risk human papillomaviruses (HPVs) are the major causative agents of cervical cancer, and the E6 and E7 genes encode the major HPV oncoproteins. The E7 protein of high-risk HPV types disturbs cell cycle control and down-regulates components of the antigen presentation pathway, suggesting a role for E7 in tumor immune evasion. We previously reported that HPV-16 E7 expression and down-regulation of HLA class I was highly correlated in cervical lesions. This study was aimed to determine whether HPV-16 E7 oncoprotein could down-regulate surface HLA class I antigen in HPV-16 E7-transfected cells, and whether it had correlation with the expression of the transporter associated with antigen processing (TAP).


METHODS
The HPV-16 E7 open reading frame was transfected into HaCaT cells. After G418 selection, resistant colonies were individually picked and expanded into clonal cell lines. Using the fluoresence-activated cell sorting analysis, the levels of cell surface HLA class I antigen and intracellular TAP-1 and TAP-2 expressions were detected.


RESULTS
Compared with the empty vector control, a statistical significant decrease of approximately 50% in cell surface HLA class I expression was observed in HPV-16 E7 expressing HaCaT cells (P < 0.001). Moreover, the expression of HPV-16 E7 in HaCaT cells resulted in decreased expression of TAP-1 that was essential for HLA class I expression at the cell surface, a statistical significant decrease of approximately 40% compared with that with the empty vector control (P < 0.001).


CONCLUSIONS
Our finding demonstrates that HPV-16 E7 down-regulates surface HLA class I antigen, which in part correlates with the decrease of TAP-1.
Department of Clinical Laboratory, Chinese Ministry of Education and Chinese Ministry of Health, Qilu Hospital, Shandong University, Jinan, China.
Wei
W
Li
Xiao-Mei
XM
Deng
Chuan-Xin
CX
Wang
Xiao
X
Zhang
Gui-Xi
GX
Zheng
Jian
J
Zhang
Jin-Bo
JB
Feng
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D002460:Cell Line; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D016366:Open Reading Frames; D050725:Papillomavirus E7 Proteins / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D000071450:ATP Binding Cassette Transporter, Subfamily B, Member 3; D018528:ATP-Binding Cassette Transporters; D015395:Histocompatibility Antigens Class I; D050725:Papillomavirus E7 Proteins; C073119:TAP1 protein, human; C059731:oncogene protein E7, Human papillomavirus type 16; C071692:TAP2 protein, human