Anticancer effect of Epigallocatechin-3-gallate on cutaneous T cell lymphoma cells

Cutaneous T-cell lymphoma (CTCL) is a rare and heterogeneous group of extranodal non-Hodgkin lymphomas for which effective treatments are limited. Since previous studies demonstrated that Epigallocatechin-3-gallate (EGCG), the most bioactive polyphenol in green tea, exerts broad anticancer effects on various tumors, we investigated the effects of EGCG on CTCL cells. Our analyses revealed that EGCG significantly inhibited the proliferation of CTCL cells in a dose-dependent and cell density-dependent manner, exhibiting a much higher sensitivity of CTCL cells in comparison to controls (peripheral blood lymphocytes (PBL) and fibroblasts). To explore the way of cell death, different inhibitors of apoptosis, ferroptosis and necroptosis were applied in combination with EGCG. The EGCG-induced cell death in CTCL cells is characterized by swelling and membrane rupture and lack of DNA degradation. By using the iron chelator deferoxamine (DFO), EGCG-induced cell death was significantly inhibited, while inhibitors of apoptosis, necroptosis, and ferroptosis had no effect, hence, not allowing us to pinpoint the effect to a specific cell death mechanism. However, by measuring ROS levels and applying the ROS scavenger N-Acetylcysteine (NAC) we revealed that EGCG treatment significantly elevated ROS levels and induced double-strand DNA breaks in CTCL cells, which were rescued by NAC and DFO. As 67 kDa laminin receptor (67LR) is considered as a cell surface receptor for EGCG, 67LR involvement was tested via RPSA shRNAs and the laminin receptor inhibitor NSC47924. We could confirm increased sensitivity to EGCG of A549 cells transduced with RPSA. However, while the RPSA-targeting shRNAs did reduce mRNA expression it could not change protein levels. But the RPSA inhibitor reduced EGCG-induced cell death in CTCL cells. Finally, RNA-sequencing was used to identify key characteristics of differentially expressed genes and pathways regulated by EGCG in Hut78 CTCL cells. The transcriptomic analysis showed that EGCG influenced cell death-related gene profiles, which were restored by NAC treatment. GSEA analysis revealed enrichment for pathways associated with redox homeostasis, cytoskeleton and cell cycle. Our results demonstrate the strong effects of EGCG inducing cell death in CTCL, which is mediated by ROS and DNA double-strand breaks. Even though the specific death modality remains up to now unclear, these findings suggest that EGCG is a promising drug candidate for development and further evaluation of innovative anti-cancer therapeutics in CTCL.