ABSTRACT
Chromosomal rearrangements involving the mixed-lineage leukemia (MLL1) gene are common in a unique group of acute leukemias, with more than 100 fusion partners in this malignancy alone. However, do these fusions occur or have a role in solid tumors? We performed extensive network analyses of MLL1-fusion partners in patient datasets, revealing that multiple MLL1-fusion partners exhibited significant interactions with the androgen-receptor signaling pathway. Further exploration of tumor sequence data from TCGA predicts the presence of MLL1 fusions with truncated SET domain in prostate tumors. To investigate the physiological relevance of MLL1 fusions in solid tumors, we engineered a truncated version of MLL1 by fusing it with one of its known fusion partners, ZC3H13, to use as a model system. Functional characterization with cell-based assays revealed that MLL1-ZC3H13 fusion induced chromosomal instability, affected mitotic progression, and enhanced tumorsphere formation. The MLL1-ZC3H13 chimera consistently increased the expression of a cancer stem cell marker (CD44); in addition, we detected potential collateral lethality between DOT1L and MLL1 fusions. Our work reveals that MLL1 fusions are likely prevalent in solid tumors and exhibit a potential pro-tumorigenic role.
Subject(s)
Cell Cycle Proteins/genetics , Chromosomal Instability/genetics , Myeloid-Lymphoid Leukemia Protein/genetics , Oncogene Fusion , Oncogene Proteins, Fusion/genetics , Recombinant Fusion Proteins/genetics , Base Sequence , Biomarkers, Tumor/metabolism , Carcinogenesis/metabolism , Carcinogenesis/pathology , Clone Cells , Gene Regulatory Networks , HCT116 Cells , Humans , Models, Biological , Myeloid-Lymphoid Leukemia Protein/metabolism , Nuclear Proteins , Oncogene Proteins, Fusion/metabolism , Phenotype , RNA-Binding Proteins , Recombinant Fusion Proteins/metabolismABSTRACT
BACKGROUND: Adoptive transfer of CD8(+) T-cells specific for tumor-antigens is an attractive strategy for anti-tumor therapy. In the present study, the subsets TA and TB were used to represent the population of CD8(+) T cells generated by culturing the respective cells with irradiated dendritic cells (DCs) pulsed with ovalbumin (OVA) protein and transfected with adenoviral vector constructs as described. METHODS: Naïve OVA specific CD8(+) T cells were isolated from the spleen of OVA-specific T-cell receptor transgenic OTI mice. The subsets TA and TB were then generated by in vitro activating the population of CD8(+) T cells with OVA-pulsed DCs transfected with IL-6-expressing adenoviral vector (AdVIL-6 ) or the control vector (AdVNull ). To assess their in vivo immunotherapeutic effects, TA - or TB -cells were intravenously transferred into C57BL/6 mice bearing EG7 thymoma (6-8 mm in diameter). RESULTS: TA -cells displayed a higher level of expression of CD62 l, IL-7R, FasL, perforin and CCR6, and also exhibited more potent in vitro cytotoxicity to OVA-expressing EG7 thymoma cells via perforin- and Fas/FasL-mediated apoptosis than TB -cells. CD8(+) T-cell survival was kinetically analyzed in C57BL/6 mice transferred with TA - or TB -cells by flow cytometry. We found that the adoptively transferred TA -cells had prolonged survival and enhanced T-cell memory development compared to TB -cells. In addition, TA -, but not TB -cells were able to eradicate well-established EG7 thymomas in all eight tumor-bearing mice. CONCLUSIONS: Our data suggest that AdVIL-6 -transfected DC-stimulated CD8(+) T cells with potent cytotoxicity and survival advantage may serve as an effective adoptive CD8(+) T-cell immunotherapy strategy for anti-tumor treatment.
