SAMHD1 inhibits epithelial cell transformation in vitro and affects leukemia development in xenograft mice

Abstract

Sterile alpha motif and HD domain-containing protein 1 (SAMHD1) is a mammalian dNTP hydrolase (dNTPase) and functions as a negative regulator in the efficacy of cytarabine treatment of acute myeloid leukemia (AML). We have reported that SAMHD1 knockout (KO) increased the activity of phosphoinositide 3-kinase (PI3K) in AML-derived THP-1 cells and attenuated their ability to form subcutaneous tumors in xenografted immunodeficient mice. However, the functional significance of SAMHD1 in controlling AML leukemogenesis remains unclear. Previous studies show that in vitro transformation of Madin-Darby canine kidney (MDCK) epithelial cells by the Jaagsiekte sheep retrovirus (JSRV) envelope protein requires activation of the PI3K/Akt oncogenic signaling pathway. Using this cell transformation model, we demonstrated that ectopic expression of wild-type human SAMHD1 or a dNTPase-defective SAMHD1 mutant (HD/AA) significantly inhibited MDCK cell transformation, but did not affect cell proliferation. To visualize and quantify THP-1 cell growth and metastasis in xenografted immunodeficient mice, we generated luciferase-expressing stable SAMHD1 KO THP-1 cells and control THP-1 cells, which were injected intravenously into immunodeficient mice. Bioluminescence imaging and quantification analysis of xenografted mice revealed that SAMHD1 KO cell-derived tumors had similar growth and metastatic potential compared with control cells at 35 days post-injection. However, mice xenografted with SAMHD1 KO cells showed greater survival compared with mice injected with control cells. Our data suggest that exogenous SAMHD1 expression suppresses in vitro cell transformation independently of its dNTPase activity, and that endogenous SAMHD1 affects AML tumorigenicity and disease progression in vivo.

Evolved Resistance to Placental Invasion Secondarily Confers Increased Survival in Melanoma Patients

“…All top five genes, with the possible exception of ENPP4 with no previous report on its role on metastasis, have been reported to be anti-metastatic in different cancer types. NR1H3 is a nuclear receptor component and an anti-invasive gene for bladder cancer [ 23 ]; PARP12 has been reported to suppress hepatocellular carcinoma metastasis [ 24 ]; SAMHD1 is yet another suppressor of epithelial transformation [ 25 ]; PSMB9 is a key metastasis suppressor for breast cancer [ 26 ]. We tested these leading edge genes for their effect on the survival of human melanoma patients.…”

Mouse model recapitulates the phenotypic heterogeneity of human adult T-cell leukemia/lymphoma in bone

“…ATL-ED cells were selected for bioluminescent imaging to monitor in vivo growth and spread. The pCDH-LTR-1-luc-EF1α-copGFP lentiviral vector was described previously [28]. Briefly, HEK293T cells were transfected with LTR-1-luc lentiviral vector plus DNA vectors encoding HIV Gag/Pol and VSV-G in 10-cm dishes using Lipofectamine®2000 reagent according to manufacturer's instructions.…”