Research Impact: B-NDG Mice Used to Identify Lipid Transport Mechanism Driving T Cell Leukemogenesis

Research Impact: B-NDG Mice Used to Identify Lipid Transport Mechanism Driving T Cell Leukemogenesis

By John Charpentier, Ph.D.
September 29, 2022

A recent study featuring Biocytogen mice identifies a non-vesicular lipid transport mechanism required for T cell leukemogenesis. Wenbing Zhong and colleagues at Jinan University in Guangzhou, China report that a lipid binding protein called ORP4L, which is expressed in adult T cell leukemia (ATL) cells but not normal T cells, is critical for cell deterioration and oncogenesis.

Altered Lipid Metabolism: A Hallmark of Cancer

Dysregulation of lipid metabolism and altered membrane phosphoinositide dynamics have long been recognized as cellular hallmarks of cancer. In recent decades, much research has focused on how such changes contribute to reprogramming of intracellular signaling and energetic states and the evolution of malignancy. Hyperactivation of the PI3K/AKT/mTOR pathway, a master regulator of cell growth, metabolism, and proliferation, has been implicated in a wide variety of cancers, including leukemias. To sustain signaling through this pathway, cells require regular replenishment of a lipid precursor, phosphatidylinositol 4-phosphate (PI(4)P), at the plasma membrane. But how exactly pro-leukemic and leukemic T cells do this at rates sufficient to sustain their astonishing growth rates has thus far been unclear.

A Lipid Transport Link to Oncogenic Signaling

A graphical abstract of the paper, showing how expression of ORP4L enables non-vesicular transport of PI(4)P to the plasma membrane.
In the absence of stimulation and ORP4L expression, PI(4)P is not shuttled to the plasma membrane and signaling through the PI3K-AKT-mTOR axis cannot be sustained (left). In the presence of stimulation and/or ORP4L expression, ORP4L heterodimerizes with OSBP to shuttle PI(4)P to the plasma membrane. There it enables pro-growth signaling through PI3K-AKT-mTOR, which contributes to leukemic transformation.

For Zhong and his collaborators, the key was in understanding the activity of a lipid binding protein, ORP4L. In a series of in vitro experiments, they discovered that both PI(4)P and another lipid binding protein, OSBP, are transported from the Golgi apparatus to the plasma membrane following stimulation of T cells genetically engineered to express ORP4L. They then showed that OSBP heterodimerizes with ORP4L to shuttle PI(4)P between the Golgi apparatus and plasma membrane, supplying the precursor compound needed to maintain hyperactive PI3K/AKT/mTOR signaling.

Next, the team demonstrated that ORP4L-OSBP-mediated PI(4)P plasma membrane delivery drives T cell deterioration and transformation in cell and animal models. They first transfected non-leukemic T cells with lentivirus encoding either wild-type ORP4L protein or a binding-incompetent variant, ORP4L△OSBP. After 16 weeks of culture, cells expressing wild-type ORP4L exhibited cellular phenotypes consistent with ATL, including high expression of Foxp3 and CCR4, IL-2-independent proliferation, and hyperactivation of the PI3K/AKT/mTOR pathway. Those expressing the version of ORP4L incapable of binding its OSBP partner, by contrast, died rapidly.

ORP4L Promotes Leukemogenesis in Immunodeficient Mice

To test whether the ORP4L-OSBP heterodimer performed the same function in vivo, Zhong and his colleagues turned to Biocytogen. Transplantation of ORP4L-expressing T cells into our highly immunodeficient B-NDG mice resulted in leukemic phenotypes and death of the mice within eight weeks. B-NDG mice transplanted with ORP4L△OSBP-expressing T cells, however, survived—powerful supporting evidence that ORP4L enables PI(4)P transport in vivo as well. Finally, when the team deleted ORP4L in transplanted ORP4L knock-in cells using a doxycycline-inducible CRISPR/Cas9 system, they observed significantly reduced tumor engraftment and prolonged survival, further evidence that ORP4L is critical component of a non-vesicular lipid transport mechanism required for T cell leukemogenesis.

Biocytogen’s parental B-NDG strain and its dozens of derivative strains are setting a new standard for highly immunodeficient mouse models. B-NDG mice are exclusively distributed by Envigo. Learn more about derived B-NDG strains, including humanized B-NDG mice here. You can check out more research publications featuring our mice here.

Citation: Zhong W, Lin W, Yang Y, et al. An acquired phosphatidylinositol 4-phosphate transport initiates T-cell deterioration and leukemogenesis. Nat Comms. 2022;13(1):4390. doi:10.1038/s41467-022-32104-7

Related blog: Development History of Immunodeficient Mice and Their Research Applications


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