Effects of human papillomavirus type 16 E7 protein on the growth of cervical carcinoma cells and immuno-escape through the TGF-beta1 signaling pathway.
OBJECTIVE
E7 is regarded as one of the main oncoproteins of high-risk human papillomaviruses (HPVs). It may affect the transforming growth factor beta 1 (TGF-beta1) signaling pathway. In this study, the relationship between HPV-16 infection and the functions of three critical factors of the TGF-beta1/Smads pathway was explored to assess the possible role of E7 in the development of cervical cancer.


METHODS
The expression of E7, TGF-beta1, TbetaR-II and Smad4 was detected by immunohistochemistry in paraffin-embedded cervical samples, and by RT-PCR and Western blotting in cervical cancer cell lines. The effect of TGF-beta1 on the growth of cervical cancer cells were tested by methyl thiazolyl tetrazolium (MTT), and the effects of HPV-16 E7 protein on normal and malignant cervical cells were investigated by flow cytometry.


RESULTS
During the progression from benign to malignant lesions, the expression levels of TGF-beta1 and Smad4 increased significantly in cervical carcinoma tissues. The expression of TGF-beta1 was positively correlated with E7 expression. In vitro experiments showed that TGF-beta1 could not inhibit the proliferation of several cervical carcinoma cell lines in long-term regulation, but could inhibit immunologic reactions of peripheral blood mononuclear cells (PBMCs). Blocking E7 expression could lower the expression level of TGF-beta1 and induce cells to enter apoptosis.


CONCLUSIONS
Our data indicate that HPV-16 E7 protein plays an important role during the development of cervical cancer by immuno-inhibition and stimulation of tumor cell proliferation through the TGF-beta1/Smads signaling pathway.
Xu
Qian
Q
Department of Obstetrics and Gynecology, Tongji Hospital, Tongji Medical School, Huazhong University of Science and Technology, 1095 Jiefang Ave., Wuhan, Hubei 430030, P R China.
Wang
Shixuan
S
Xi
Ling
L
Wu
Sufang
S
Chen
Gang
G
Zhao
Yun
Y
Wu
Ying
Y
Ma
Ding
D
D048708:Cell Growth Processes; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006367:HeLa Cells; D052162:Human papillomavirus 16 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D007376:Interleukin-2 / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000276:immunology / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000235:genetics; D009856:Oncogene Proteins, Viral / Q000096:biosynthesis* / Q000235:genetics; D050725:Papillomavirus E7 Proteins; D030361:Papillomavirus Infections / Q000150:complications / Q000235:genetics / Q000378:metabolism* / Q000821:virology; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000096:biosynthesis; D015398:Signal Transduction; D051901:Smad4 Protein / Q000096:biosynthesis; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics; D053773:Transforming Growth Factor beta1; D002583:Uterine Cervical Neoplasms / Q000276:immunology / Q000378:metabolism* / Q000473:pathology / Q000821:virology; D002578:Uterine Cervical Dysplasia / Q000276:immunology / Q000378:metabolism* / Q000473:pathology / Q000821:virology
D007376:Interleukin-2; D016376:Oligonucleotides, Antisense; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D012333:RNA, Messenger; D018125:Receptors, Transforming Growth Factor beta; C497796:SMAD4 protein, human; D051901:Smad4 Protein; C508960:TGFB1 protein, human; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; C059731:oncogene protein E7, Human papillomavirus type 16; D007371:Interferon-gamma; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II