Patient-derived tumor immune microenvironments in patient-derived xenografts of lung cancer

Xingxiang Pu,Yungchang Chen,Shuhong Wu,Li Wang,Ran Zhang,Dan Su,Bingliang Fang,Yi Xu,Weimin Mao,Jack A Roth,Stephen G Swisher,Xiaoshan Zhang,Ismail M Meraz,Lin Wu,Apar Pataer,John V Heymach

doi:10.1186/s12967-018-1704-3

Abstract

BackgroundBecause patient-derived xenografts (PDXs) are grown in immunodeficient mouse strains, PDXs are regarded as lacking an immune microenvironment. However, whether patients’ immune cells co-exist in PDXs remains uncharacterized.MethodsWe cultured small pieces of lung PDX tissue in media containing human interleukin-2 and characterized the proliferated lymphocytes by flow cytometric assays with antibodies specific for human immune cell surface markers. Presence of immune cells in PDXs was also determined by immunohistochemical staining.ResultsHuman tumor-infiltrating lymphocytes (TILs) were cultured from nine of 25 PDX samples (36%). The mean time of PDX growth in immunodeficient mice before obtaining TILs in culture was 113 days (range 63–292 days). The TILs detected in PDXs were predominantly human CD8+ T cells, CD4+ T cells, or CD19+ B cells, depending on cases. DNA fingerprint analysis showed that the TILs originated from the same patients as the PDXs. Further analysis of two PDX-derived CD8+ T cells showed that they were PD-1−, CD45RO+, and either CD62L+ or CD62L−, suggesting they were likely memory T cells. Immunohistochemical staining showed that human T cells (CD8+ or CD4+), B cells (CD19+), and macrophages (CD68+) were present in stroma or intraepithelial cancer structures and that human PD-L1 was expressed in stromal cells. Moreover, the patient-derived immune cells in PDX can be passaged to the F2 generation and may migrate to spleens of PDX-bearing mice.ConclusionsPatient-derived immune cells co-exist in early passages of PDXs in some lung cancer PDX models. The CD8+ cells from PDXs were likely memory T cells. These results suggest that PDXs can be used for evaluating the functionality of immune components in tumor microenvironments.

Highlights

Because patient-derived xenografts (PDXs) are grown in immunodeficient mouse strains, Patient-derived xenografts (PDX) are regarded as lacking an immune microenvironment
Thirteen PDXs were in the first passage in mice (F1), and 12 PDXs were in the second passage (F2) when they were acquired for tumor-infiltrating lymphocyte (TIL) culture
Our results demonstrated that patient-derived T cells and/or B cells co-exist in some PDXs and that these immune cells may be passed in early passages of PDXs

Summary

Introduction

Because patient-derived xenografts (PDXs) are grown in immunodeficient mouse strains, PDXs are regarded as lacking an immune microenvironment. Recent progress in immunotherapy with immune checkpoint inhibitors has offered new options for the treatment of lung cancer, a deadly disease that each year causes approximately 155,870 deaths in the United States and 1.6 million deaths worldwide [1, 2]. Clinical studies have shown that immune checkpoint blockade therapy for patients with advanced NSCLC improved survival rates, prolonged duration of response, and reduced treatment-related adverse effects [9]. Strategies to overcome primary resistance to immune checkpoint inhibitors, either through combination therapy or through discovery of new targets to modulate anticancer immunity, are urgently needed so that more lung cancer patients can benefit from immunotherapy. Mouse models with an in vivo “humanized” environment will be desirable for preclinical evaluation of strategies aimed at improving efficacies of immune-modulating drugs

Methods

Results

Discussion

Conclusion