Characterization of an Mtbp Hypomorphic Allele in a Diethylnitrosamine-Induced Liver Carcinogenesis Model

SIMPLE SUMMARY: The MDM2 binding protein MTBP is implicated in various cellular functions and cancer-related processes, which vary depending on the cellular context and its localization within the cell. Moreover, the in vivo physiological function of MTBP remains unclear. To overcome embryonic lethality due to complete deletion of the Mtbp gene in mice, we created mice with an Mtbp hypomorphic allele (Mtbp(H)) that expresses Mtbp protein at approximately 30% of the wild-type level. In a carcinogen-induced liver cancer model, Mtbp(H/−) mice showed worse overall survival than wild-type mice. MEFs generated from the Mtbp(H/−) mice displayed an increased nuclear localization of p-Erk1/2 protein and enhanced migratory potential. Thus, the newly generated Mtbp(H/−) mice and MEFs can be used to study the in vivo physiological function of Mtbp and validate its diverse functions observed in human cells. ABSTRACT: MTBP is implicated in cell cycle progression, DNA replication, and cancer metastasis. However, the function of MTBP remains enigmatic and is dependent on cellular contexts and its cellular localization. To understand the in vivo physiological role of MTBP, it is important to generate Mtbp knockout mice. However, complete deletion of the Mtbp gene in mice results in early embryonic lethality, while its heterozygous deletion shows modest biological phenotypes, including enhanced cancer metastasis. To overcome this and better characterize the in vivo physiological function of MTBP, we, for the first time, generated mice that carry an Mtbp hypomorphic allele (Mtbp(H)) in which Mtbp protein is expressed at approximately 30% of that in the wild-type allele. We treated wild-type, Mtbp(+/−), and Mtbp(H/−) mice with a liver carcinogen, diethylnitrosamine (DEN), and found that the Mtbp(H/−) mice showed worse overall survival when compared to the wild-type mice. Consistent with previous reports using human liver cancer cells, mouse embryonic fibroblasts (MEFs) from the Mtbp(H/−) mice showed an increase in the nuclear localization of p-Erk1/2 and migratory potential. Thus, Mtbp(H/−) mice and cells from Mtbp(H/−) mice are valuable to understand the in vivo physiological role of Mtbp and validate the diverse functions of MTBP that have been observed in human cells.