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Updated: Aug 19, 2026

Intracellular Phosphoflow Cytometry of Acute Myeloid Leukemia Patient-Derived Xenotransplants
Published on: June 6, 2025
The oncoprotein I-2PP2A/SET negatively regulates the MEK/ERK pathway and cell proliferation
Chikako Fukukawa1, Hiroshi Shima, Nobuhiro Tanuma
1Division of Biochemical Oncology and Immunology, Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan.
Abstract:
I-2PP2A/SET, the translocation breakpoint-encoded protein expressed in acute undifferentiated leukemia, was identified as an inhibitor of protein phosphatase 2A (PP2A). Induction of exogenous I-2PP2A/SET at a ratio of 1:1 to the endogenous protein resulted in suppression of cell proliferation. In contrast, siRNA-mediated depletion of I-2PP2A/SET resulted in enhanced cell proliferation. Depletion of I-2PP2A/SET was accompanied with a decrease in the number of cells in G1 and an increase in cells in S phase. To examine the mode of action by which I-2PP2A/SET suppresses cell proliferation, we determined the effect of over-expressed I-2PP2A/SET on ERK activation. I-2PP2A/SET suppressed activation of ERK following EGF stimulation but did not affect activation levels of stress kinases, JNK and p38. By contrast, knocking down I-2PP2A/SET by siRNA resulted in enhancement of ERK and MEK activations, suggesting that I-2PP2A/SET negatively regulates MEK/ERK. These data suggest that I-2PP2A/SET negatively regulates cell growth by inhibiting the G1/S transition and inhibiting the MEK/ERK pathway stimulated by external stimuli. These data demonstrate that I-2PP2A/SET potentially functions as a tumor suppressor.
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