Analysis of ROR1 Protein Expression in Mice with Reconstituted Human Immune System Components.

Carol S Leung

doi:10.1155/2018/2480931

Abstract

Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an oncofetal antigen expressed on multiple tumors and has no significant expression on normal human tissues. ROR1 is highly upregulated in chronic lymphocytic leukemia (CLL) B cells. NOD-scid IL2rg−/− (NSG) mice engrafted with human CD34+ hematopoietic progenitor cells (huNSG) achieved multilineage human immune cell reconstitution including B cells, T cells, NK cells, and DCs. Like the CLL patients, huNSG mice have abnormally high percentage of CD5-expressing B cells in the periphery. In light of this, we aim to determine whether ROR1 is expressed on huNSG B cells. Using flow cytometry analysis, we found that ROR1 was highly expressed in a proportion of bone marrow, spleen, and blood B cells, which were mostly immature B cells. Transplantation of the oncogene TCL-1-transduced CD34+ cells in neonatal NSG mice did not increase the frequency of ROR1-expressing B cells, but the mouse with the highest engraftment of transduced cells developed a tumor-like lump consisting of a high percentage of ROR1-expressing B cells. This study highlights the potential use of huNSG mice to study B cell malignant diseases and to evaluate immunotherapeutics targeting ROR1.

Highlights

Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an oncofetal antigen expressed in a number of malignancies
Most of the huNSG mice achieved a frequency of more than 50% of human CD45+ cells in total leukocytes after 3 months of reconstitution, with engraftment of CD19+ B cells, CD3+ T cells, and NKp46+ natural killer (NK) cells (Figure 1)
In line with other findings [15, 20], our huNSG mice were reconstituted with all major subsets of immune cells after neonatal hematopoietic progenitor cell transplantation. huNSG mice have a high frequency of CD19+ B cells in the periphery, and over 50% of these B cells express the CD5 antigen [21]

Summary

Introduction

Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an oncofetal antigen expressed in a number of malignancies. The overexpression of ROR1 in malignancy was first identified on chronic lymphocytic leukemia (CLL) B cells [1] and was subsequently found in many other hematological malignancies [2,3,4] and solid tumors [5]. As ROR1 has expression on tumor cells but not on normal human tissues except at low levels in adipose tissues, parathyroid, pancreatic islet cells, and some regions of the gastrointestinal tract [8], this makes it an attractive antigen target for cancer therapy. A number of ROR1-specific monoclonal antibodies and chimeric antigen receptor (CAR) T cells have been developed and are under testing [9, 10]. A preclinical small animal model is currently lacking to evaluate ROR1-targeted immunotherapies

Objectives

Methods

Results

Conclusion