The retinoid derivant ECPIRM selectively exhibited anti-proliferation effects in cutaneous T-Cell lymphoma via ITK-mediated signaling pathway.

Background: The treatment of Cutaneous T-cell lymphoma (CTCL) met huge challenges because of the heterogeneity and the scarcity of targeted drugs. ECPIRM derived from isotretinoin exhibited strong anti-proliferation effects in Hut78 and MJ cells rather than Myla cells. However, there was no data regarding the potential target of ECPIRM for its selective activity.

Objectives: To investigate the potential target of ECPIRM for its selective anti-proliferation activity.

Methods: We evaluated the cell viability of CTCL cells after ECPIRM treatment, and detected the effects of ECPIRM on the biomarker genes of CTCL. Subsequently, the mRNA and protein level of Interleukin-2-inducible T-cell kinase (ITK) was determined. Then the induction of apoptosis triggered by ITK inhibitor BMS-509744 and ITK siRNAs were detected, and the docking of ECPIRM interacted with ITK and the effects of ECPIRM on ITK-mediated signaling pathway were analyzed. Finally, we evaluated the anti-growth activity of ECPIRM in Hut78-xenografted nude mice, and the relative expression of cleaved caspase-3, ITK, p-ERK and p-Akt were determined.

Results: ITK was highly expressed in Hut78 and MJ cells rather than Myla cells, and targeted inhibition of ITK triggered cell apoptosis. ECPIRM efficiently bound the hydrophobic active pocket of ITK, and significantly inhibited ITK-mediated signaling pathway. In addition, ECPIRM suppressed tumor growth in Hut78-xenografted model, and upregulated the expression of cleaved caspase 3 and inhibited the expression of ITK, p-ERK and p-Akt in tumor tissues, which was consistent with in vitro study.

Conclusion: ECPIRM might provide a novel strategy for CTCL by inhibiting ITK-mediated signaling pathway.