Direct transfer of a foreign MHC gene into human melanoma alters T cell receptor Vβ usage by tumor-infiltrating lymphocytes
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The direct introduction of foreign genes into tumors shows promise as a therapeutic modality to enhance tumor immunogenicity. Hence, melanoma nodules were directly injected with a vector encoding an allogeneic MHC class I molecule, HLA-B7. Tumor-infiltrating lymphocytes (TIL) were isolated from cutaneous melanoma biopsies before and after HLA-B7 gene transfer. TIL were expanded in interleukin-2 (IL-2) by standard techniques for approximately 4 weeks, then analyzed for T cell receptor Vβ usage by quantitative reverse transcriptase polymerase chain reaction (RT-PCR). Prior to gene transfer, TIL Vβ usage was found to be highly restricted, the only one to four Vβ families being expressed and one or two of these families representing more than 90% of the repertoire. As anticipated, TIL Vβ usage varied among patients expressing different HLA types. However, Vβ13 was over-represented in that six of eight patients utilized Vβ13 as a dominant family, regardless of HLA type. Following HLA-B7 gene transfer, TIL Vβ usage was markedly altered: (1) Vβ families that dominated following gene transfer differed from the Vβ families utilized by TIL prior to treatment, and (2) introduction of the HLA-B7 gene resulted in a more diverse repertoire with an increase in the number of Vβ families represented. In two patients, TIL were evaluated before treatment and from multiple, distinct melanoma nodules following gene transfer. In these two patients, a comparison was made between TIL Vβ profiles obtained after treatment from nodules that had been injected with the HLA-B7 gene or left untreated. Interestingly, the Vβ repertoires of TIL from uninjected nodules following gene transfer were similar to that of TIL from injected nodules, rather than pretreatment TIL. These data demonstrate a direct immunological effect of foreign MHC gene transfer into human melanoma, and suggest that local expression of an allogeneic MHC molecule generates systemic alterations in the antitumor immune response.
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