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Growth inhibition and apoptosis due to restoration of E2A activity in T cell acute lymphoblastic leukemia cells.

Park ST, Nolan GP, Sun XH - J. Exp. Med. (1999)

Bottom Line: The activation model suggests that Tal1 as heterodimers with the E2A transcription factor activates the expression of oncogenes.The inhibition model postulates that Tal1 interferes with the tumor-suppressing function of E2A.In the Jurkat T cell line, originally derived from a patient with T-ALL, Tal1 is complexed with E2A proteins and the transcriptional activity of E2A is very low.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, New York University Medical Center, New York 10016, USA.

ABSTRACT
Two models have been proposed for the molecular mechanism by which the Tal1 oncogene causes T cell acute lymphoblastic leukemia (T-ALL). The activation model suggests that Tal1 as heterodimers with the E2A transcription factor activates the expression of oncogenes. The inhibition model postulates that Tal1 interferes with the tumor-suppressing function of E2A. In the Jurkat T cell line, originally derived from a patient with T-ALL, Tal1 is complexed with E2A proteins and the transcriptional activity of E2A is very low. When E2A activity was restored by expressing an E2A-Tal1 fusion protein, E-T/2, the Jurkat cells underwent growth arrest and subsequently apoptosis, thus supporting the inhibition model and suggesting that E2A loss may contribute to leukemic progression.

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No effect on the growth rate of S194 and PD31 cells by  E-T/2. (A) Growth curves. On day 0 (24 h after sorting), S194 and PD31  infected cells were plated at densities of 3 × 105 and 5 × 105 cells/ml, respectively in media containing 5% FCS. Viable cells were counted daily  using a hemacytometer after trypan blue exclusion of the dead cells. The  data is representative of several experiments. (B) Western blot using anti-E47 antibodies. Total cell extracts were prepared from S194 and PD31  cells infected with the indicated retrovirus. The E-T/2 and endogenous  E2A proteins are indicated by the arrows. A degradation product of E-T/2  in PD31 cells is marked by an asterisk.
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Figure 3: No effect on the growth rate of S194 and PD31 cells by E-T/2. (A) Growth curves. On day 0 (24 h after sorting), S194 and PD31 infected cells were plated at densities of 3 × 105 and 5 × 105 cells/ml, respectively in media containing 5% FCS. Viable cells were counted daily using a hemacytometer after trypan blue exclusion of the dead cells. The data is representative of several experiments. (B) Western blot using anti-E47 antibodies. Total cell extracts were prepared from S194 and PD31 cells infected with the indicated retrovirus. The E-T/2 and endogenous E2A proteins are indicated by the arrows. A degradation product of E-T/2 in PD31 cells is marked by an asterisk.

Mentions: Growth rate analyses were set up using vector- and E-T/2–infected cells. As shown in Fig. 2, cells infected with E-T/2 were severely impaired in their ability to proliferate when cultured in 1, 5, or 15% FCS. This impairment was most pronounced at the lowest serum concentration. By day 5, cells infected with E-T/2 had started to level off in their growth. In contrast, cells infected with the control virus continued to proliferate. By day 7, the number of cells in the E-T/2 infection had actually decreased to a level lower than the initial starting point. Significant inhibition of growth was also observed in cells cultured in the presence of 5 and 15% FCS. The doubling times for E-T/2 cells cultured under these conditions were increased by twofold compared with control cells. To exclude the possibility that the decrease in growth rate of Jurkat/E cells was due to nonspecific toxicities of the E-T/2 protein, negative controls were performed by using two murine B cell lines, S194 (plasmacytoma) and PD31 (Abelson virus-transformed pre-B cell). After these cells were infected with the E-T/2 and MIGR1 viruses, they were sorted for GFP fluorescence and their growth rates were monitored. As shown in Fig. 3, expression of E-T/2 in these two cell lines did not appear to have any effect on their growth rates.


Growth inhibition and apoptosis due to restoration of E2A activity in T cell acute lymphoblastic leukemia cells.

Park ST, Nolan GP, Sun XH - J. Exp. Med. (1999)

No effect on the growth rate of S194 and PD31 cells by  E-T/2. (A) Growth curves. On day 0 (24 h after sorting), S194 and PD31  infected cells were plated at densities of 3 × 105 and 5 × 105 cells/ml, respectively in media containing 5% FCS. Viable cells were counted daily  using a hemacytometer after trypan blue exclusion of the dead cells. The  data is representative of several experiments. (B) Western blot using anti-E47 antibodies. Total cell extracts were prepared from S194 and PD31  cells infected with the indicated retrovirus. The E-T/2 and endogenous  E2A proteins are indicated by the arrows. A degradation product of E-T/2  in PD31 cells is marked by an asterisk.
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Related In: Results  -  Collection

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Figure 3: No effect on the growth rate of S194 and PD31 cells by E-T/2. (A) Growth curves. On day 0 (24 h after sorting), S194 and PD31 infected cells were plated at densities of 3 × 105 and 5 × 105 cells/ml, respectively in media containing 5% FCS. Viable cells were counted daily using a hemacytometer after trypan blue exclusion of the dead cells. The data is representative of several experiments. (B) Western blot using anti-E47 antibodies. Total cell extracts were prepared from S194 and PD31 cells infected with the indicated retrovirus. The E-T/2 and endogenous E2A proteins are indicated by the arrows. A degradation product of E-T/2 in PD31 cells is marked by an asterisk.
Mentions: Growth rate analyses were set up using vector- and E-T/2–infected cells. As shown in Fig. 2, cells infected with E-T/2 were severely impaired in their ability to proliferate when cultured in 1, 5, or 15% FCS. This impairment was most pronounced at the lowest serum concentration. By day 5, cells infected with E-T/2 had started to level off in their growth. In contrast, cells infected with the control virus continued to proliferate. By day 7, the number of cells in the E-T/2 infection had actually decreased to a level lower than the initial starting point. Significant inhibition of growth was also observed in cells cultured in the presence of 5 and 15% FCS. The doubling times for E-T/2 cells cultured under these conditions were increased by twofold compared with control cells. To exclude the possibility that the decrease in growth rate of Jurkat/E cells was due to nonspecific toxicities of the E-T/2 protein, negative controls were performed by using two murine B cell lines, S194 (plasmacytoma) and PD31 (Abelson virus-transformed pre-B cell). After these cells were infected with the E-T/2 and MIGR1 viruses, they were sorted for GFP fluorescence and their growth rates were monitored. As shown in Fig. 3, expression of E-T/2 in these two cell lines did not appear to have any effect on their growth rates.

Bottom Line: The activation model suggests that Tal1 as heterodimers with the E2A transcription factor activates the expression of oncogenes.The inhibition model postulates that Tal1 interferes with the tumor-suppressing function of E2A.In the Jurkat T cell line, originally derived from a patient with T-ALL, Tal1 is complexed with E2A proteins and the transcriptional activity of E2A is very low.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, New York University Medical Center, New York 10016, USA.

ABSTRACT
Two models have been proposed for the molecular mechanism by which the Tal1 oncogene causes T cell acute lymphoblastic leukemia (T-ALL). The activation model suggests that Tal1 as heterodimers with the E2A transcription factor activates the expression of oncogenes. The inhibition model postulates that Tal1 interferes with the tumor-suppressing function of E2A. In the Jurkat T cell line, originally derived from a patient with T-ALL, Tal1 is complexed with E2A proteins and the transcriptional activity of E2A is very low. When E2A activity was restored by expressing an E2A-Tal1 fusion protein, E-T/2, the Jurkat cells underwent growth arrest and subsequently apoptosis, thus supporting the inhibition model and suggesting that E2A loss may contribute to leukemic progression.

Show MeSH
Related in: MedlinePlus