Gene transfer preferentially selects MHC class I positive tumour cells and enhances tumour immunogenicity

Abstract

The modulated expression of MHC class I on tumour tissue is well documented. Although the effect of MHC class I expression on the tumorigenicity and immunogenicity of MHC class I negative tumour cell lines has been rigorously studied, less is known about the validity of gene transfer and selection in cell lines with a mixed MHC class I phenotype. To address this issue we identified a C26 cell subline that consists of distinct populations of MHC class I (H-2D/K) positive and negative cells. Transient transfection experiments using liposome-based transfer showed a lower transgene expression in MHC class I negative cells. In addition, MHC class I negative cells were more sensitive to antibiotic selection. This led to the generation of fully MHC class I positive cell lines. In contrast to C26 cells, all transfectants were rejected in vivo and induced protection against the parental tumour cells in rechallenge experiments. Tumour cell specificity of the immune response was demonstrated in in vitro cytokine secretion and cytotoxicity assays. Transfectants expressing CD40 ligand and hygromycin phosphotransferase were not more immunogenic than cells expressing hygromycin resistance alone. We suggest that the MHC class I positive phenotype of the C26 transfectants had a bearing on their immunogenicity, because selected MHC class I positive cells were more immunogenic than parental C26 cells and could induce specific anti-tumour immune responses. These data demonstrate that the generation of tumour cell transfectants can lead to the selection of subpopulations that show an altered phenotype compared to the parental cell line and display altered immunogenicity independent of selection marker genes or other immune modulatory genes. Our results show the importance of monitoring gene transfer in the whole tumour cell population, especially for the evaluation of in vivo therapies targeted to heterogeneous tumour cell populations.

Features of the immune proteasome expression in ascite Zajdela hepatoma after implantation into Brattleboro rats with the hereditary defect of arginine-vasopressin synthesis

“…Lack of MHC class I molecules on tumor cells is the signal to NK cells for the destruction of these cells [25]. The microenviron ment in which the tumor develops also facilitates the selection of certain tumor sublines characterized by an individual set of mutations [26,27]. Increased activity of NK cells in Brattleboro rats [13] may lead to the destruction of tumor cell clones which do not carry MHC class I molecules.…”

Desenvolvimento de modelos murinos de linfoma T para investigar o impacto da expressão gênica ectópica no comportamento in vivo de linhagens celulares tumorais.

“…decisão pelo uso da construção retroviral foi por permitir a integração do DNA plasmidial no genoma da célula hospedeira, expressão contínua da proteína de interesse na célula-alvo e devido à baixa imunogenicidade causada pelas proteínas retrovirais in vivo (Mulligan, 1993). (Townsend e Bodmer, 1989;Ljunggren e Karre, 1990;Hacker, et al, 2006;Zamai, et al, 2007). Além disso, observou-se através da análise de quando inoculadas células RMA.Egfp, os animais apresentaram paralisia da região posterior do corpo, de forma ascendente, progressiva e irreversível, acompanhada de perda de peso.…”