OBJECTIVES: Hematopoietic stroma promotes resistance to immune control by APO2L/TRAIL in multiple myeloma (MM) cells in part by increasing synthesis of the anti-apoptotic protein c-FLIP. Here, we tested whether bortezomib can reverse the APO2L/TRAIL environmental mediated-immune resistance (EM-IR). MATERIAL AND METHODS: MM cell lines (RPMI 8226 and U266) and CD138+ patient's MM cells were directly adhered to HS5 stroma exposed to HS5 or bone marrow stroma of patients with MM released soluble factors in a transwell system. Cells were treated with either APO2L/TRAIL (10 ng/mL), bortezomib (10 nm) or both. RESULTS: Pretreatment with bortezomib effectively overcomes APO2L/TRAIL apoptosis resistance in myeloma cell lines and in CD138+ cells while directly adhered or in transwell assay. Bortezomib was not cytotoxic to HS5 stroma cells and only altered monocyte chemotactic protein-2-3 and IL-10 levels in the stroma-myeloma milieu. Factors released by HS5 stroma increased expression of c-FLIP, induced STAT-3 and ERK phosphorylation and reduced DR4 receptor expression in MM cells. HS5 stroma-released factor(s) induced NF-kappaB activation after 20 h exposure in association with an enhanced c-FLIP transcription. Bortezomib effectively reduced c-FLIP protein expression without affecting other proteins. Bortezomib also increased DR4 and DR5 expression in the presence of stroma. CONCLUSIONS: These findings provide the rationale to combine bortezomib and APO2L/TRAIL to disrupt the influence of the stroma microenvironment on MM cells.
OBJECTIVES: Hematopoietic stroma promotes resistance to immune control by APO2L/TRAIL in multiple myeloma (MM) cells in part by increasing synthesis of the anti-apoptotic protein c-FLIP. Here, we tested whether bortezomib can reverse the APO2L/TRAIL environmental mediated-immune resistance (EM-IR). MATERIAL AND METHODS: MM cell lines (RPMI 8226 and U266) and CD138+ patient's MM cells were directly adhered to HS5 stroma exposed to HS5 or bone marrow stroma of patients with MM released soluble factors in a transwell system. Cells were treated with either APO2L/TRAIL (10 ng/mL), bortezomib (10 nm) or both. RESULTS: Pretreatment with bortezomib effectively overcomes APO2L/TRAIL apoptosis resistance in myeloma cell lines and in CD138+ cells while directly adhered or in transwell assay. Bortezomib was not cytotoxic to HS5 stroma cells and only altered monocyte chemotactic protein-2-3 and IL-10 levels in the stroma-myeloma milieu. Factors released by HS5 stroma increased expression of c-FLIP, induced STAT-3 and ERK phosphorylation and reduced DR4 receptor expression in MM cells. HS5 stroma-released factor(s) induced NF-kappaB activation after 20 h exposure in association with an enhanced c-FLIP transcription. Bortezomib effectively reduced c-FLIP protein expression without affecting other proteins. Bortezomib also increased DR4 and DR5 expression in the presence of stroma. CONCLUSIONS: These findings provide the rationale to combine bortezomib and APO2L/TRAIL to disrupt the influence of the stroma microenvironment on MM cells.
Authors: Robert O'Connor; Melissa G Ooi; Justine Meiller; Jana Jakubikova; Steffen Klippel; Jake Delmore; Paul Richardson; Kenneth Anderson; Martin Clynes; Constantine S Mitsiades; Peter O'Gorman Journal: Cancer Chemother Pharmacol Date: 2013-04-16 Impact factor: 3.333
Authors: Alessandro Natoni; Mark R E Coyne; Alan Jacobsen; Michael D Rainey; Gemma O'Brien; Sandra Healy; Alessia Montagnoli; Jürgen Moll; Michael O'Dwyer; Corrado Santocanale Journal: Cancers (Basel) Date: 2013-07-24 Impact factor: 6.639