RNA binding protein Lin28B promotes chronic myeloid leukemia blast crisis by transcriptionally upregulating miR-181d.

The blast crisis (BC) of chronic myeloid leukemia (CML) has poor efficacy against existing treatments and extremely short survival. However, the molecular mechanism of CML-chronic phase (CP) transformation to CML-BC is not yet fully understood. Here, we show that Lin28B, a RNA binding protein, acted as an activator enhancing the transformation to CML-BC by mediating excessive cell proliferation. The level of Lin28B expression was apparently elevated in CML-BC patients compared with newly diagnosed CML-CP patients. The overexpression of Lin28B promoted the proliferation of leukemia cells. Mechanistically, we identified Lin28B as a DNA binding protein by binding to the promoter region of miR-181d and upregulating its expression, which inhibited the expression of Programmed cell death 4 (PDCD4) by binding to the PDCD4 3'UTR region, thereby enhancing the proliferation of CML cells. Overall, the "Lin28B-miR-181d-PDCD4" regulatory axis promoted CML blast crisis. Implications: Our findings highlight the oncogenic role of Lin28B in CML blast crisis, acting as a DNA binding protein which transcriptionally upregulates miR-181d expression.