Selective histocompatibility leukocyte antigen (HLA)-A2 loss caused by aberrant pre-mRNA splicing in 624MEL28 melanoma cells.
Selective histocompatibility leukocyte antigen (HLA)-A2 loss caused by aberrant pre-mRNA splicing in 624MEL28 melanoma cells.
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DOI：
10.1084/jem.190.2.205
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发表时间：
1999-07-19
期刊：
影响因子：
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通讯作者：
Ferrone S
中科院分区：
文献类型：
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作者：
Wang Z;Marincola FM;Rivoltini L;Parmiani G;Ferrone S
组织相容性白细胞抗原（HLA）-A2被用作将几种黑素瘤相关抗原（MAA）衍生的肽呈递给细胞毒性T淋巴细胞（CTL）的限制性元件。HLA-A2抗原在原发性黑色素瘤病变中选择性丢失，在转移瘤中更常见。尽管这种异常对疾病的临床过程和基于T细胞的免疫治疗的结果有潜在的负面影响，但关于这种异常的分子机制的信息很少。因此，在本研究中，我们证明了黑色素瘤细胞624 MEL 28中选择性的HLA-A2抗原丢失是由HLA-A2基因内含子2的5′剪接供体位点的碱基替换导致的HLA-A2前mRNA的剪接缺陷引起的。因此，HLA-A2转录物被剪接成两种异常形式，一种具有外显子2跳跃，另一种具有内含子2保留。后者不被翻译，因为保留内含子中的早期过早终止密码子。相反，具有外显子2跳跃的转录物被翻译成截短的HLA-A2重链而没有α1结构域。这种多肽在体外合成，但在细胞中检测不到，可能是因为相应mRNA的稳态水平低和翻译效率低。这些结果表明，HLA I类基因中的单个突变事件足以导致相应等位基因的丢失。这可能至少部分地解释了黑素瘤细胞中选择性HLA I类等位基因丢失的高频率。我们的结论强调需要利用各种HLA I类等位基因呈现的肽组合实施主动特异性免疫治疗。这种策略可能会抵消选择性HLA I类等位基因丢失的黑色素瘤细胞逃避免疫识别的能力。
Histocompatibility leukocyte antigen (HLA)-A2 is used as a restricting element to present several melanoma-associated antigen (MAA)-derived peptides to cytotoxic T lymphocytes (CTLs). HLA-A2 antigen is selectively lost in primary melanoma lesions and more frequently in metastases. Only scanty information is available about the molecular mechanisms underlying this abnormality, in spite of its potentially negative impact on the clinical course of the disease and on the outcome of T cell–based immunotherapy. Therefore, in this study we have shown that the selective HLA-A2 antigen loss in melanoma cells 624MEL28 is caused by a splicing defect of HLA-A2 pre-mRNA because of a base substitution at the 5′ splice donor site of intron 2 of the HLA-A2 gene. As a result, HLA-A2 transcripts are spliced to two aberrant forms, one with exon 2 skipping and the other with intron 2 retention. The latter is not translated because of an early premature stop codon in the retained intron. In contrast, the transcript with exon 2 skipping is translated to a truncated HLA-A2 heavy chain without the α1 domain. Such a polypeptide is synthesized in vitro but is not detectable in cells, probably because of the low steady state level of the corresponding mRNA and the low translation efficiency. These results indicate that a single mutational event in an HLA class I gene is sufficient for loss of the corresponding allele. This may account, at least in part, for the high frequency of selective HLA class I allele loss in melanoma cells. Our conclusion emphasizes the need to implement active specific immunotherapy with a combination of peptides presented by various HLA class I alleles. This strategy may counteract the ability of melanoma cells with selective HLA class I allele loss to escape from immune recognition.