Abstract 4822: Detection of EBV BamHI W region in surgical cancer specimen is a useful method to evaluate the risk of lymphomagenesis in patient-derived tumor xenografts
Authors: Mukohyama Junko , Iwakiri Dai , Zen Yoh , Mukohara Toru , Minami Hironobu , Kakeji Yoshihiro , Shimono Yohei 
Published: July 2017

Patient-derived tumor xenografts (PDXs) established by xenotransplantation of surgically-resected human cancer specimens are an attractive model to analyze the character of cancer cells within the patient cancer tissues. However, establishment of PDX is occasionally hampered by lymphomagenesis.

Lymphomagenesis in the PDX has been observed in the xenotransplantation of several types of cancers, such as lung, liver, gastric, bladder, breast, prostate, and colorectal cancers. Lymphomagenesis in the PDX is caused by the proliferation of the EBV-infected lymphocytes under insufficient immunosurveillance in the immunodeficient mice. However, it is still difficult to predict lymphomagenesis before xenotransplantation.

In this study, we analyzed the expression of EBV-related genes in the 15 surgical specimens of the consented colorectal cancer (CRC) patients and the PDXs established by their xenotransplantation. The CRC specimens and the established PDX tumors were histologically examined. Then, the specimens were immunohistochemically stained with anti-CD3 and CD20 antibodies. The presence of EBV was histologically evaluated by EBER in situ. The expression levels of EBV-related genes, such as EBNAs, LMP1, EBER, BamHI W region and EBV-associated microRNAs, were evaluated using the genomic DNA and mRNAs prepared from the CRC specimens and the established PDX tumors.

Nine PDXs were established by the xenotransplantation. Histological examination showed that 7 of 9 (78%) PDX recapitulated histopathological characteristics of the patient CRC tissues. However, 2 of 9 (22%) PDXs exhibited the morphological characteristics of EBV-associated human diffuse large B cell lymphoma (DLBCL). Then, we confirmed that lymphoma was formed by clonal proliferation of human B-cell lymphocytes, and strongly positive for EBER. We investigated whether the expression of EBV-related genes in the patient specimen is associated with lymphomagenesis in the PDXs. Expression of EBV genes and RNAs in patient CRC tissues were not clearly associated with lymphomagenesis in the PDXs. BamHI W region is a major internal repeat in EBV genome and the PCR amplification of this region is useful to evaluate the presence and amount of EBV. When the EBV BamHI W region was detectable in the patient specimens, the transplantation of the samples resulted in lymphomagenesis in 2 out of 3 patient cancer specimens. In contrast, when this region was undetectable, no patient cancer specimens resulted in lymphomagenesis (0 out of 7 patient cancer specimens).

These results suggest that the amount and/or presence of EBV itself in the patient cancer specimens is one of the factors that are associated with lymphomagenesis in the PDXs. Therefore, the PCR amplification of EBV BamHI W region is an attractive method to evaluate the risk of lymphomagenesis before xenotransplantation.

Citation Format: Junko Mukohyama, Dai Iwakiri, Yoh Zen, Toru Mukohara, Hironobu Minami, Yoshihiro Kakeji, Yohei Shimono. Detection of EBV BamHI W region in surgical cancer specimen is a useful method to evaluate the risk of lymphomagenesis in patient-derived tumor xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4822. doi:10.1158/1538-7445.AM2017-4822