PIM kinase inhibition decreases tumor initiating cell phenotype in hepatoblastoma

Objective:We previously demonstrated that PIM3 promoted tumorigenesis in a human hepatoblastoma (HB) cell line, HuH6. Tumor initiating cells (TICs) are a subpopulation of cells responsible for tumor resistance and recurrence.... [ view full abstract ]

Objective:

We previously demonstrated that PIM3 promoted tumorigenesis in a human hepatoblastoma (HB) cell line, HuH6. Tumor initiating cells (TICs) are a subpopulation of cells responsible for tumor resistance and recurrence. We hypothesized that CD133 is a marker for TICs in HB and that PIM3 inhibition would decrease the TIC phenotype.

Methods:

Cells were separated by CD133 expression using magnetic beads. Sphere-forming ability in vitro and tumor initiating capacity in mice were assessed using limiting dilution analysis. PIM3 expression was determined by immunoblotting in HuH6 cells and a human HB patient-derived xenograft (PDX), COA67, and by immunohistochemistry in the COA67 parent tumor. Following treatment with a PIM inhibitor, AZD1208, CD133 expression was determined by immunoblotting. Proliferation was assessed using CellTiter 96â. c² and t-tests were used with p£0.05 significant.

Results:

CD133-enriched cells exhibited increased sphere formation versus CD133-depleted cells (p<0.001). Three weeks after injection, 8/14 mice bore tumors in the CD133-enriched group compared to 2/14 mice in the CD133-depleted group (p<0.05). PIM3 was expressed in HuH6 and COA67 cells and the COA67 parent tumor. Treatment with AZD1208 significantly decreased CD133 expression and proliferation in both CD133-enriched and CD133-depleted populations. AZD1208 treatment significantly decreased sphere formation in HuH6 CD133-enriched cells, COA67 CD133-enriched cells, and COA67 CD133-depleted cells (p£0.01).

Conclusion:

CD133 is a marker for TICs in HB. PIM inhibition in HuH6 and COA67 PDX HB cells decreased the frequency and proliferation of TICs. These data suggest that PIM inhibition warrants further exploration as a novel therapy for HB.