Sa1280 Adult-Onset Autoimmune Enteropathy: An European Single Center Experience

Enteropathy-associated T-cell lymphoma (EATL) is a rare intestinal lymphoma that arises from intraepithelial lymphocytes.Clinical outcome of patients with EATL is very poor, due to chemotherapy-resistance and high relapse rates.Therefore, new therapeutic options for EATL are urgently needed.Many studies in other types of lymphoma have shown that inhibition of apoptosis may cause chemotherapy-resistance and that restoration of defective apoptosis can induce cell death in these lymphomas.Preliminary data in EATL samples have demonstrated an increased expression of a fraction of NF-κB target genes, suggesting upregulation of NF-κB activity in EATL tumor cells.The proteasome inhibitor bortezomib inhibits NF-κB activity and can induce apoptosis via upregulation of the pro-apoptotic BH3only protein Noxa.In the present study, we evaluated if the intrinsic apoptosis pathway is disrupted in EATL and if bortezomib can restore apoptosis in cultured EATL cells.Lasercapture microdissection was applied to 19 frozen EATL samples to obtain purified tumor cells for RNA isolation.Intraepithelial lymphocytes (IEL) of healthy controls were obtained from fresh duodenal biopsies and isolated by FACS cell sorting.RT-MLPA analysis revealed that expression of the pro-apoptotic BH3-only gene Noxa was significantly downregulated in EATL cells compared to healthy donor IEL.Treatment with bortezomib resulted in induction of apoptosis in all EATL samples tested.The lethal dose (LD50) varied between 5 nM and 15 nM after 36 and 48 hours of incubation.Bortezomib-induced cell death in EATL cells was caspase-9 mediated.mRNA and protein expression analyses showed upregulation of Noxa after incubation with bortezomib.Downregulation of Noxa using siRNA analysis decreased bortezomib-induced apoptosis in EATL cells.In conclusion, our study showed that bortezomib induces apoptosis by upregulation of Noxa in EATL cells.Therefore, bortezomib should be considered as a potential drug in the treatment of patients with EATL to improve their prognosis.