Lysosomal lipid peroxidation regulates tumor immunity
Monika Bhardwaj, Jennifer J. Lee, Amanda M. Versace, Sandra L. Harper, Aaron R. Goldman, Mary Ann S. Crissey, Vaibhav Jain, Mahendra Pal Singh, Megane Vernon, Andrew E. Aplin, Seokwoo Lee, Masao Morita, Jeffrey D. Winkler, Qin Liu, David W. Speicher, Ravi K. Amaravadi
Monika Bhardwaj, Jennifer J. Lee, Amanda M. Versace, Sandra L. Harper, Aaron R. Goldman, Mary Ann S. Crissey, Vaibhav Jain, Mahendra Pal Singh, Megane Vernon, Andrew E. Aplin, Seokwoo Lee, Masao Morita, Jeffrey D. Winkler, Qin Liu, David W. Speicher, Ravi K. Amaravadi
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Research Article Oncology

Lysosomal lipid peroxidation regulates tumor immunity

Abstract

Lysosomal inhibition elicited by palmitoyl-protein thioesterase 1 (PPT1) inhibitors such as DC661 can produce cell death, but the mechanism for this is not completely understood. Programmed cell death pathways (autophagy, apoptosis, necroptosis, ferroptosis, and pyroptosis) were not required to achieve the cytotoxic effect of DC661. Inhibition of cathepsins, or iron or calcium chelation, did not rescue DC661-induced cytotoxicity. PPT1 inhibition induced lysosomal lipid peroxidation (LLP), which led to lysosomal membrane permeabilization and cell death that could be reversed by the antioxidant N-acetylcysteine (NAC) but not by other lipid peroxidation antioxidants. The lysosomal cysteine transporter MFSD12 was required for intralysosomal transport of NAC and rescue of LLP. PPT1 inhibition produced cell-intrinsic immunogenicity with surface expression of calreticulin that could only be reversed with NAC. DC661-treated cells primed naive T cells and enhanced T cell–mediated toxicity. Mice vaccinated with DC661-treated cells engendered adaptive immunity and tumor rejection in “immune hot” tumors but not in “immune cold” tumors. These findings demonstrate that LLP drives lysosomal cell death, a unique immunogenic form of cell death, pointing the way to rational combinations of immunotherapy and lysosomal inhibition that can be tested in clinical trials.

Authors

Monika Bhardwaj, Jennifer J. Lee, Amanda M. Versace, Sandra L. Harper, Aaron R. Goldman, Mary Ann S. Crissey, Vaibhav Jain, Mahendra Pal Singh, Megane Vernon, Andrew E. Aplin, Seokwoo Lee, Masao Morita, Jeffrey D. Winkler, Qin Liu, David W. Speicher, Ravi K. Amaravadi

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Figure 9

Inoculation of DC661-treated cells produces tumor rejection in specific contexts.

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Inoculation of DC661-treated cells produces tumor rejection in specific ...
(A) Schema of tumor vaccination model. (B–E) Cells were treated with DMSO or DC661 for 36 hours and then s.c. injected (1.8 × 105 B16F10 cells, 1.5 × 106 MC38 cells, or 3.0 × 106 CT26 cells per mouse) into the left flank of immunocompetent syngeneic C57BL/6J, BALB/c mice, or immunodeficient NOD/SCID mice. Freeze-thawed (F/T) DMSO-treated cells were used as control. One week later, all mice were rechallenged and s.c. injected with live untreated cells (3 × 104 B16F10 cells, 2 × 105 MC38 cells, or 5 × 105 CT26 cells per mouse) into the right flank of corresponding vaccinated mice. Dot plot of final tumor volumes for each individual mouse in each treatment group shown. n = 4–10 per group. (F) Illustration of DC661-induced lysosomal lipid peroxidation and immunogenic cell death.