Bone Marrow-Derived Cells Exhibiting Lung Epithelial Cell Characteristics Are Enriched In Vivo Using Methylguanine DNA Methyltransferase-Mediated Drug Resistance

Abstract

Previous studies have suggested that donor bone marrow-derived cells can differentiate into lung epithelial cells at low frequency. We investigated whether we could enrich the number of donor-derived hematopoietic cells that have type II pneumocyte characteristics by overexpression of the drug resistance gene methylguanine DNA methyltransferase (MGMT). MGMT encodes O(6)-alkylguanine DNA alkyltransferase (AGT), a drug resistance protein for DNA damage induced by N,N'-bis(2-chloroethyl)-N-nitrosourea (BCNU), and the mutant P140K MGMT confers resistance to BCNU and the AGT inactivator O(6)-benzylguanine (BG). For this study, we used two MGMT selection models: one in which donor cells had a strong selection advantage because the recipient lung lacked MGMT expression, and another in which drug resistance was conferred by gene transfer of P140K MGMT. In both models, we saw an increase in the total number of donor-derived cells in the lung after BCNU treatment. Analysis of single-cell suspensions from 28 mice showed donor-derived cells with characteristics of type II pneumocytes, determined by surfactant protein C (SP-C) expression. Furthermore, an increase in the percentage of donor-derived SP-C cells was noted after BCNU or BG and BCNU treatment. This study demonstrates that bone marrow cells expressing MGMT can engraft in the lung and convert into cells expressing the type II pneumocyte protein SP-C. Furthermore, these cells can be enriched in response to alkylating agent-mediated lung injury. These results suggest that expression of MGMT could enhance the capacity of bone marrow-derived cells to repopulate lung epithelium, and when used in combination with a gene of interest, MGMT could have therapeutic applications.