| First Author | Wang SF | Year | 2008 |
| Journal | Blood | Volume | 111 |
| Issue | 5 | Pages | 2878-86 |
| PubMed ID | 18180377 | Mgi Jnum | J:131580 |
| Mgi Id | MGI:3773983 | Doi | 10.1182/blood-2007-07-103119 |
| Citation | Wang SF, et al. (2008) Development of Notch-dependent T-cell leukemia by deregulated Rap1 signaling. Blood 111(5):2878-86 |
| abstractText | SPA-1 (signal-induced proliferation associated gene-1) functions as a suppressor of myeloid leukemia by negatively regulating Rap1 signaling in hematopoietic progenitor cells (HPCs). Herein, we showed that transplantation of HPCs expressing farnesylated C3G (C3G-F), a Rap1 guanine nucleotide exchange factor, resulted in a marked expansion of thymocytes bearing unique phenotypes (CD4/CD8 double positive [DP] CD3(-) TCRbeta(-)) in irradiated recipients. SPA-1(-/-) HPCs expressing C3G-F caused a more extensive expansion of DP thymocytes, resulting in lethal T-cell acute lymphoblastic leukemia (T-ALL) with massive invasion of clonal T-cell blasts into vital organs. The C3G-F(+) blastic thymocytes exhibited constitutive Rap1 activation and markedly enhanced expression of Notch1, 3 as well as the target genes, Hes1, pTalpha, and c-Myc. All the T-ALL cell lines from C3G-F(+) SPA-1(-/-) HPC recipients expressed high levels of Notch1 with characteristic mutations resulting in the C-terminal truncation. This proliferation was inhibited completely in the presence of a gamma-secretase inhibitor. Transplantation of Rag2(-/-) SPA-1(-/-) HPCs expressing C3G-F also resulted in a marked expansion and transformation of DP thymocytes. The results suggested that deregulated constitutive Rap1 activation caused abnormal expansion of DP thymocytes, bypassing the pre-T-cell receptor and eventually leading to Notch1 mutations and Notch-dependent T-ALL. |
