Effects of Imatinib and Rapamycin on the mTOR/S6 Signal Transduction Pathway in CD33⁺ Cell of CML

Objective: To evaluate the changes of the mTOR/S6 signal transduction pathway of CD33⁺ cell in chronic myeloid leukemia (CML), and the effect of imatinib and rapamycin on it. Since the RAPA could influenced the immunity of T cell, the changes of expression of IFN-γ in CD3⁺, CD3⁺CD8⁻ and CD3⁺CD8⁺T cell was evaluated after treating with RAPA.

Methods: By flow cytometry, the contents of p-mTOR and p-S6 in CD33⁺ cells were detected in the new diagnosed CML, CML treated with imatinib or hydroxycarbamide and interferon (HU+IFN), CML resisted imatinib, and normal control, or after treated with RAPA in vitro, respectively. Then expression of IFN-γ in CD3⁺, CD3⁺CD8⁻ and CD3⁺CD8⁺T cell in patients with higher levels of p-mTOR/p-S6 was measured after RAPA.

Results:

1. The contents of p-mTOR and p-S6 in CD33⁺ cell in the primary CML were higher than that in the normal control m(9.53±7.87)%vs(2.43±2.54)% GP<0.05] [(7.64±3.17)%vs(1.21±1.44)%; P<0.05], could be reduced by RAPA in vitro [(9.53±7. 87)%vs(3.64±3.29)%, p<0.05], [(7.64±3.17)%vs(1.85±2.51)%; P<0.05].

2. The contents of p-mTOR in CD33⁺ cell in the patients treated with imatinib were higher than that of the group with HU+IFN [(10.61±13.70)%vs(3.67±4.59)%; P<0.05], could be reduced by RAPA [(10.61±13.70)%vs(3.86±8.99)% GP<0.05]. p-mTOR in CD33⁺ cell exceeded the 95% confidence interval of primary CML in 25.7% of patients treated with imatinib, and it was reduced by RAPA [(29.89±14.89)%vs(8.26±15.45)% GP<0.05]. There were no difference in the contents of p-mTOR in CD33⁺ cell between HU+IFN group and the primary CML [(3.67±4.59)%vs(9.53±7.87)%, P<0.05].

3. Compared to the primary CML, the contents of p-S6 in CD33⁺ cell of the patients treated with imatinib was not significant different [(7.64±3.17)%%vs(19.65±30.19) GP>0.05], while it was lower in the patients treated with HU+IFN [(7.64±3.17)%%vs(2.95±2.70) GP<0.05]. p-S6 in CD33⁺ cell exceeded the 95% confidence interval of primary CML in 25.7% of patients treated with imatinib, and it was reduced by RAPA [(44.48±19.43)%vs(10.53±12.39)%, P<0.05].

4. RAPA did not influence the expression of IFN-γ in CD3⁺, CD3⁺CD8⁻ and CD3⁺CD8⁺T cell in patients with higher levels of p-mTOR/p-S6 [(24.69±10.86)%vs(24.32±12.08)% GP>0.05], [(18.79±8.72)%vs(17.0±6.53)% GP>0.05], [(31.59±12.86)%vs(30.45±14.99)% GP>0.05].

5. p-mTOR and p-S6 in CD33⁺ cell exceeded the 95% confidence interval of the primary CML group were found in 2 cases (20%) in imatinib resistant group, and could be reduced by RAPA in vitro.

RAPA did not influence the expression of IFN-γ in CD3⁺, CD3⁺CD8⁻ and CD3⁺CD8⁺T cell in these 2 patients.

Conclusion:

1. The mTOR/S6 signal transduction pathway in CD33⁺ cell was activated in primary CML patients, and could be blocked by RAPA.

2. In some patients treated with imatinib, the mTOR/S6 signal transduction pathway in CD33⁺ cell increased, also could be blocked by RAPA.

3. In minority of patients resistant to imatinib, the mTOR/S6 signal transduction pathway in CD33⁺ cell was activated, and it might participate the resistance to imatinib.

RAPA could block it. RAPA did not impact on the immunity of T cell of patients with CML.