Merkel cell polyomavirus-infected Merkel cell carcinoma cells require expression of viral T antigens.
Merkel cell carcinoma (MCC) is the most aggressive skin cancer. Recently, it was demonstrated that human Merkel cell polyomavirus (MCV) is clonally integrated in approximately 80% of MCC tumors. However, direct evidence for whether oncogenic viral proteins are needed for the maintenance of MCC cells is still missing. To address this question, we knocked down MCV T-antigen (TA) expression in MCV-positive MCC cell lines using three different short hairpin RNA (shRNA)-expressing vectors targeting exon 1 of the TAs. The MCC cell lines used include three newly generated MCV-infected cell lines and one MCV-negative cell line from MCC tumors. Notably, all MCV-positive MCC cell lines underwent growth arrest and/or cell death upon TA knockdown, whereas the proliferation of MCV-negative cell lines remained unaffected. Despite an increase in the number of annexin V-positive, 7-amino-actinomycin D (7-AAD)-negative cells upon TA knockdown, activation of caspases or changes in the expression and phosphorylation of Bcl-2 family members were not consistently detected after TA suppression. Our study provides the first direct experimental evidence that TA expression is necessary for the maintenance of MCV-positive MCC and that MCV is the infectious cause of MCV-positive MCC.
Houben
Roland
R
Molecular Virology Program, University of Pittsburgh Cancer Institute, 5117 Centre Ave., Pittsburgh, PA 15213, USA.
Shuda
Masahiro
M
Weinkam
Rita
R
Schrama
David
D
Feng
Huichen
H
Chang
Yuan
Y
Moore
Patrick S
PS
Becker
Jürgen C
JC
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics / Q000378:metabolism*; D015266:Carcinoma, Merkel Cell / Q000473:pathology / Q000821:virology*; D002453:Cell Cycle / Q000502:physiology; D045744:Cell Line, Tumor; D002470:Cell Survival; D005260:Female; D055785:Gene Knockdown Techniques; D006801:Humans; D008297:Male; D008875:Middle Aged; D011120:Polyomavirus / Q000276:immunology* / Q000378:metabolism; D027601:Polyomavirus Infections / Q000378:metabolism / Q000473:pathology / Q000821:virology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology / Q000821:virology*
D000952:Antigens, Polyomavirus Transforming; D019253:Proto-Oncogene Proteins c-bcl-2
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