Abstract
Establishment of patient-derived tumor xenografts (PDXs) is hampered by lymphomagenesis mostly caused by the latently-infected Epstein-Barr virus (EBV) contained in patient cancer tissues. However, the character of patient tissues that result in lymphomagenesis after xenotransplantation is not elucidated. In this study, we analyzed the patient colorectal cancer (CRC) tissues and the PDXs established by their xenotransplantation. We found that 2 of 9 (22%) PDX tumors were EBV-associated human diffuse large B cell lymphoma which was formed by clonal proliferation of human B-cell lymphocytes, were strongly positive for EBER-ISH, and were classified as type III latency. Expression of EBV genes and RNAs, such as EBNAs, LMP1, EBER and EBV-associated microRNAs in patient CRC tissues were unlikely to be associated with lymphomagenesis in PDXs. In contrast, the positive PCR-based amplification of BamHI W region, a major internal repeat in EBV genome, in the patient CRC tissues was correlated with lymphomagenesis in PDXs. These results suggest that the detection of the EBV BamHI W region in the patient surgical specimens will be an effective way to predict the risk of lymphomagenesis in PDXs before xenotransplantation.
Highlights
Patient-derived tumor xenografts (PDXs) are established by xenotransplantation of surgically resected human cancer specimens into immunodeficient mice, such as a nonobese diabetic/severe combined immunodeficientcy (NOD/SCID) mouse which is deficient in both innate and adaptive immunities, and an NOD/ SCID/IL-2rgnull (NSG) mouse which further lacks NK cell activity
These results suggest that the detection of the Epstein-Barr virus (EBV) BamHI W region in the patient surgical specimens will be an effective way to predict the risk of lymphomagenesis in patient-derived tumor xenografts (PDXs) before xenotransplantation
The expression levels of these miRNAs were extremely high in the diffuse large B-cell lymphoma (DLBCL) PDXs (Supplementary Figure S3), but were low www.impactjournals.com/oncotarget or hardly detectable in the patient colorectal cancer (CRC) specimen of KUC11 in which the amplification of the EBV BamHI W region was weak (Figure 5, Supplementary Figure S3). These miRNAs were detectable in the patient specimen of KUC4 in which higher amplification of the EBV BamHI W region and the expression of EBNA genes were observed (Figure 5A, Supplementary Figures S2A and S3). These results suggest that the detection of EBV BamHI W region from the CRC surgical specimens with p-EBV-BW PCR will be an effective way to evaluate the risk of lymphomagenesis before xenotransplantation
Summary
Patient-derived tumor xenografts (PDXs) are established by xenotransplantation of surgically resected human cancer specimens into immunodeficient mice, such as a nonobese diabetic/severe combined immunodeficientcy (NOD/SCID) mouse which is deficient in both innate and adaptive immunities, and an NOD/ SCID/IL-2rgnull (NSG) mouse which further lacks NK cell activity. It is reported that the engraftment of human cancer specimens into an immunodeficient mouse unexpectedly resulted in the formation of lymphoma instead of their corresponding cancers, such as lung, liver, gastric, bladder, breast and prostate cancers [6,7,8,9,10]. The incidence of lymphomagenesis among the established PDXs differ widely depending on the cancer types; for example, 1/30 PDXs (3.3 %) in colorectal cancer (CRC), 11/21 (56%) PDXs derived from 16 patients in liver cancer, and 8/10 PDXs (80%) in prostate cancer [7, 8, 10]. Pathological analyses of 26 lymphoma PDXs revealed that 23 PDXs were EpsteinBarr virus (EBV)-associated human B cell lymphoma, and the remaining 3 PDXs were lymphoma of mouse origin [8]
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