In:
The Journal of Immunology, The American Association of Immunologists, Vol. 167, No. 1 ( 2001-07-01), p. 98-106
Abstract:
In melanoma cell lines, two different patterns of MHC class II expression have been described, either an IFN γ-inducible expression of HLA-DR and HLA-DP, with a faint or null expression of HLA-DQ, resembling that described for melanocytes, or a constitutive expression, i.e., IFN-γ independent, of all three HLA-D isotypes. As this latter phenotype has been associated with a more rapid progression of melanoma tumors, we have analyzed in different melanoma cell lines the molecular mechanisms leading to this abnormal pattern of MHC class II expression. In agreement with the evidence of a coordinate transcription of the HLA-D genes in these cell lines, we have shown the constitutive expression of CIITA (class II transactivator) transcripts, CIITA being known as the master switch of MHC class II expression. Unexpectedly, these transcripts initiate from promoter III of the CIITA gene, a promoter that is mainly used constitutively in B lymphocytes. This expression was further shown to occur through factor(s) acting on the enhancer located upstream of CIITA promoter III, which was previously described in epithelioid cells as an IFN-γ-response sequence. The hypothesis of a general abnormality of the IFN-γ transduction pathway was dismissed. Constitutive transcription of CIITA from promoter III having been observed in unrelated melanoma cell lines, we propose the hypothesis that this phenomenon might not be a random event, but could be linked to the neoplasic state of the melanoma cells.
Type of Medium:
Online Resource
ISSN:
0022-1767
,
1550-6606
DOI:
10.4049/jimmunol.167.1.98
Language:
English
Publisher:
The American Association of Immunologists
Publication Date:
2001
detail.hit.zdb_id:
1475085-5
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