Heat shock and HSP70 regulate 5-FU-mediated caspase-1 activation in myeloid-derived suppressor cells and tumor growth in mice

Abstract

BackgroundWe have previously shown that 5-fluorouracil (5-FU) selectively kills myeloid-derived suppressor cells (MDSCs) and activates NLRP3 (NOD-leucine rich repeat and pyrin containing protein 3) inflammasome. NLRP3 activation leads to caspase-1 activation and production of IL-1β, which in turn favors secondary tumor growth. We decided to explore the effects of either a heat shock (HS) or the deficiency in heat shock protein (HSP) 70, previously shown to respectively inhibit or increase NLRP3 inflammasome activation in macrophages.MethodsCaspase-1 activation was detected in vitro in MSC-2 cells by western blot and in vivo or ex vivo in tumor and/or splenic MDSCs by flow cytometry. The effects of HS, HSP70 deficiency and anakinra (an IL-1 inhibitor) on tumor growth and mice survival were studied in C57BL/6 WT orHsp70−/−tumor-bearing mice. Finally, Th17 polarization was evaluated by qPCR (Il17a, Rorc) and angiogenic markers by qPCR (Pecam1, Eng) and immunohistochemistry (ERG).ResultsHS inhibits 5-FU-mediated caspase-1 activation in vitro and in vivo without affecting its cytotoxicity on MDSCs. Moreover, it enhances the antitumor effect of 5-FU treatment and favors mice survival. Interestingly, it is associated to a decreased Th17 and angiogenesis markers in tumors. IL-1β injection is able to bypass HS+5-FU antitumor effects. In contrast, inHsp70−/−MDSCs, 5-FU-mediated caspase-1 activation is increased in vivo and in vitro without effect on 5-FU cytotoxicity. InHsp70−/−mice, the antitumor effect of 5-FU was impeded, with an increased Th17 and angiogenesis markers in tumors. Finally, the effects of 5-FU on tumor growth can be restored by inhibiting IL-1β, using anakinra.ConclusionThis study provides evidence on the role of HSP70 in tuning 5-FU antitumor effect and suggests that HS can be used to improve 5-FU anticancer effect.

Targeting myeloid-derived suppressor cells to attenuate vasculogenic mimicry and synergistically enhance the anti-tumor effect of PD-1 inhibitor

“…In addition to DOX, previous study has found that 5-FU has an inhibitory effect on MDSCs (Pilot et al, 2020;Vincent et al, 2010). In the present study, we found that the inhibitory effect of DOX was comparable with that of 5-FU.…”

Interleukin-1β and Cancer

“…We previously showed that HSP70 can inhibit NLRP3 inflammasome [ 232 , 233 ]. The importance of IL-1β in tumor escape from 5-FU treatment was strengthened, with the confirmation that HSP70 deficiency in mice leads to high caspase-1 activation in MDSCs, subsequent angiogenesis, and rapid tumor growth, whereas hyperthermia (which increases HSP70 expression) inhibits these events and slows down tumor growth [ 234 ].…”

“…Finally, we proposed hyperthermia as a new modulator of the NLRP3 inflammasome [ 232 ]. It can block caspase-1 activation in MDSCs, and subsequent angiogenesis and rapid tumor growth in mice [ 234 ]. Although hyperthermia is already used in specific treatment protocols, further studies are required to demonstrate its efficiency in humans.…”

Association Between TRPC6 Channel and NLRP3 Inflammasome Activities in Kidney Tissue of Children With Henoch-Schönlein Purpura Nephritis

“…Combined with the results of this study, it is not di cult to see that TRPC6 plays an important role in the progression of glomerular disease, and taking measures against it will greatly help the diagnosis and prevention of kidney disease. NLRP3 in ammasome is one of the members of the intracellular in ammatory protein complex family, which is composed of NLRP3 protein, adaptor ASC (an apoptosis-related speck-like protein containing CARD domain) and Caspase-1 precursor 9 . In normal cells, these protein complexes exist in an inactive form.…”