Ectopic expression of TC-PTP partially rescues loss of MYC expression. (A) Doxycycline-induced repression of the MYC transgene results in cell-cycle arrest followed by cell death. FLL-44 cells were treated with 5 μg/mL doxycycline, and changes to total cellular DNA content were tracked by propidium iodide staining. Representative plots are shown; n = 4. (B) Western blot analysis of ectopic TC-PTP expression. FLL-44 cells were transduced with either empty vector pMIG or pMIG-TC-PTP. Transduced and sorted cells were either left untreated or treated for 48 hours with doxycycline to repress the MYC transgene, after which the cells were lysed with 1% TX-100 and lysates were analyzed by Western blot with anti-Myc, anti–TC-PTP (6F3), anti–human TC-PTP (CF4-1D), and anti–β-actin. Blots were stripped in between each Western blot. (C) Ectopic TC-PTP expression is positively selected for following the repression of MYC overexpression. Transduced FLL-44 cells were treated with 5 μg/mL doxycycline, to turn off expression of the MYC transgene, or an equal volume of PBS vehicle as a control. The frequency of GFP⁺ cells was tracked by FACS analysis, and is presented as the ratio of doxycycline-treated to vehicle-treated cells for each set of transductions. Error bars represent SE; n = 4 or more experiments. (D) Ectopic TC-PTP expression promotes limited proliferation in the absence of the MYC transgene. Proliferation was monitored by cell counting in transduced and sorted FLL-44 cells. Results are normalized to cell counts at 0 hours; n = 4.