The results showed that C10 regulated the expression of Bax, c-Myc, Bcl-2, P38/AMPK and ERK 1/2, activated the expression of Caspase-3, -8, and PARP at the protein level in the apoptosis pathway of the two leukemia cell types, and inhibited the expression of erythroleukemia carcinogene Fli-1 in the human erythroleukemia cell line HEL.
In contrast, expression of Spi‑1/PU.1 in a Fli‑1 producing erythroleukemia cell line in which fli‑1 is activated, resulted in increased proliferation through activation of growth promoting proteins MAPK, AKT, cMYC and JAK2.
Aberrant expression of Fli-1 also underlies a number of virally induced leukemias, including Friend virus-induced erythroleukemia and various types of human cancers, and it is the target of chromosomal translocations in childhood Ewing's sarcoma.
These results suggest, for the first time, an essential role for continuous Fli-1 overexpression in the maintenance and survival of the malignant phenotype in murine and human erythroleukemias.
The Ets transcription factor, Fli-1, has been shown to play a pivotal role in the induction and progression of Friend Murine Leukemia Virus (F-MuLV)-induced erythroleukemia, with its overexpression leading to erythroblast survival, proliferation, and inhibition of terminal differentiation.
Retroviral insertional activation of Fli-1 and Spi-1/PU.1, as well as loss of tumour suppressor genes such as p53 or p45 NFE2 have been shown to be critical for the induction and progression of Friend virus-induced erythroleukemias.
Rearrangement of the FLI-1 locus and ensuing overexpression of FLI-1 protein is an early event in Friend murine leukemia virus (F-MuLV)-induced erythroleukemia.
PU.1 was identified as a target of insertional activation in the majority of tumors induced by the murine Spleen Focus Forming virus (SFFV), while fli-1 proved to be the target of Friend murine leukemia virus (F-MuLV) in F-MuLV induced erythroleukemia, as well as that of the 10A1 and Graffi viruses.
Indeed, the etiology of a number of virally induced leukemias, including Friend virus-induced erythroleukemia, has been associated with Fli-1 overexpression.
We further suggest that deregulated synthesis of Fli-1 may trigger a common mechanism contributing to erythroleukemia induced by either SFFV or F-MuLV.
Furthermore, the data suggest an indirect interaction between Fli-1 and RAR alpha mediated by a 'bridging' factor(s) present in nuclear extracts from RM10 erythroleukemia cells.
Activation of the Fli-1 gene by either chromosomal translocation or viral insertion leads to Ewing's sarcoma in humans and erythroleukemia in mice, respectively.
The Fli-1 gene was found to be rearranged in 75% of the erythroleukemias induced by Friend murine leukemia virus (F-MuLV), suggesting that it could play a key role in cellular transformation.
Fli-1 is not rearranged or activated in the erythroleukemias induced by SFFV, and similarly Spi-1 is not rearranged or activated in the leukemic cell clones induced by F-MuLV.
Mouse Fli-1 was shown to be involved in 75% erythroleukemias induced by Friend murine leukemia virus suggesting the possibility that Fli-1 may play a critical role in cellular transformation.