Reovirus therapy stimulates endoplasmic reticular stress, NOXA induction, and augments bortezomib-mediated apoptosis in multiple myeloma

Abstract

Oncolytic virotherapy with reovirus has demonstrated anti-cancer activity and minimal toxicity in clinical trials, but the mechanisms underlying these effects have not been fully elucidated. Reolysin, a proprietary formulation of reovirus for cancer therapy, stimulated selective viral replication and apoptosis in multiple myeloma (MM) cells. Reolysin-mediated apoptosis was associated with an induction of endoplasmic reticular (ER) stress-related gene expression, swelling of the endoplasmic reticulum, increases in intracellular calcium levels and a strong induction of the Bcl-2 homology 3 (BH3)-only pro-apoptotic protein NOXA. Knockdown of NOXA expression by short hairpin RNA significantly reduced the pro-apoptotic effects of Reolysin. We next showed that co-administration of Reolysin and bortezomib resulted in the dual accumulation of viral and ubiquitinated proteins, which led to enhanced ER stress, NOXA induction and apoptosis. Importantly, the combination of reovirus infection and proteasomal inhibition significantly decreased tumor burden in a xenograft and syngeneic bone disease model of MM without exhibiting adverse side effects. Our study establishes ER stress stimulation and NOXA induction as novel mediators of reovirus-induced apoptosis. Furthermore, reovirus infection can be used as a promising approach to augment the anti-myeloma activity of bortezomib by promoting additional stress to the endoplasmic reticulum of MM cells.

Expression pattern and transcriptional regulatory mechanism of noxa gene in grass carp (Ctenopharyngodon idella)

“…The cytochome c was released into cytosol and then leaded to cell apoptosis [14,15]. In mammalians, Noxa protein plays an important role in apoptosis induced by mammalian reovirus [16,17]. In zebrafish, Noxa protein was a key mediator of apoptosis in both embryogenesis and adult [18,19].…”

Reovirus as a successful ex vivo purging modality for multiple myeloma

“…In addition to the common N-ras and K-ras mutations that are frequently found in MM, many other diverse cancer-promoting signaling pathways such as the MEK/ERK, PI3K/Akt, mTOR/p70S6-kinase and NF-kB pathways have been identified 20 that may promote reovirus lytic infection, thus enhancing the range of potential treatable patients. In susceptible cancers, reovirus is thought to take advantage of these activated neoplastic signaling pathways in a p53-independent/-dependent manner and engage in NF-kB activation/trafficking, autocrine release of the TNF-related apoptosis-inducing ligand and activation of endoplasmic reticular stress (reviewed by Thirukkumaran et al 21 and Kelly et al 22 ).…”

Endoplasmic Reticulum Stress and the Unfolded Protein Response: Targeting the Achilles Heel of Multiple Myeloma

“…It has been proposed that Reolysin has a potential in targeting multiple myeloma cells as reovirus replication may promote ER stress-induced apoptosis via the accumulation of viral proteins (67). Indeed, Reolysin was shown to have antimyeloma activity in cell lines, in ex vivo patient tumor specimens, and in in vivo mouse models of multiple myeloma (67,68). Furthermore, Reolysin induced NOXA-mediated apoptosis in multiple myeloma cells and significantly increased the antimyeloma activity of bortezomib (67).…”

“…Indeed, Reolysin was shown to have antimyeloma activity in cell lines, in ex vivo patient tumor specimens, and in in vivo mouse models of multiple myeloma (67,68). Furthermore, Reolysin induced NOXA-mediated apoptosis in multiple myeloma cells and significantly increased the antimyeloma activity of bortezomib (67). Interestingly, Reolysin induced ER stress in multiple myeloma cells as determined by increased XBP1 splicing, ER swelling, and increased intracellular calcium levels (Table 1; ref.…”

“…The reovirus-based therapeutic Reolysin is well tolerated in clinical trials for several cancers and showed potent anticancer activity (66). It has been proposed that Reolysin has a potential in targeting multiple myeloma cells as reovirus replication may promote ER stress-induced apoptosis via the accumulation of viral proteins (67). Indeed, Reolysin was shown to have antimyeloma activity in cell lines, in ex vivo patient tumor specimens, and in in vivo mouse models of multiple myeloma (67,68).…”