Abstract 6175: 1-Palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol ameliorates chemoradiation-induced oral mucositis in a mouse model by regulating necroptosis

Background: Currently, no approved drug exist to treat oral mucositis (OM) in patients receiving chemoradiation for the treatment of head and neck cancer. To address this limitation, we examined the therapeutic effect of 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG), which is an immune resolution accelerator that can effectively modulate the neutrophil recruitment, against chemoradiation-induced oral mucositis (CRIOM) in a murine model. Additionally, we investigated whether necroptosis is involved in the pathogenesis of CRIOM in a murine model and the therapeutic effect of PLAG against the disease. Methods: To investigate the improved effect of PLAG on CRIOM, we established the CRIOM-bearing BALB/c mouse model using concurrent treatments of 5-fluorouracil (100 mg/kg, i.p.) and X-radiation (20 Gy) on the heads and necks of mice. Phosphate buffer saline or PLAG (100 and 250 mg/kg, p.o.) was administered daily. The body weights of mice were observed daily and on Day 9, the mice were sacrificed for extracting their tongues for further tissue analyses. The histopathological grading of OM was analyzed in the collected tongues. Human keratinocytes (HaCaT) were utilized to identify the mechanism of PLAG on regulating the necroptosis signals. Results: On Day 9, chemoradiotherapy-treated (ChemoRT) mice had tongue ulcerations and experienced significant weight loss (Day 0: 26.18 ± 1.41 g; Day 9: 19.44 ± 3.26 g). They also had elevated serum macrophage inhibitory protein 2 (MIP-2) (control: 5.57 ± 3.49 pg/ml; ChemoRT: 130.14 ± 114.54 pg/ml) and interleukin (IL)-6 (control: 198.25 ± 16.91 pg/ml; ChemoRT: 467.25 ± 108.12 pg/ml) levels. ChemoRT-treated mice who received PLAG exhibited no weight loss (Day 0: 25.78 ± 1.04 g; Day 9: 26.46 ± 1.68 g) and had lower serum MIP-2 (4.42 ± 4.04 pg/ ml) and IL-6 (205.75 ± 30.41 pg/ml) levels than ChemoRT-treated mice without the PLAG treatment. Tongue tissues of mice who received PLAG also displayed lower phosphorylation levels of necroptotic signaling proteins (RIPK1/3 and MLKL). Chemoradiation induced the release of damaged-associated molecular patterns (DAMPs), which activates the necroptosis signaling pathway if not promptly eliminated intracellularly in HaCaT cells. PLAG promoted the effective removal of DAMPs, thereby downregulating the activation of necroptosis signaling pathway. Conclusion: On day 9, the tongues of mice-treated with chemoradiotherapy activated the necroptosis signaling pathway. As a result, cells from oral mucosa released DAMPs and pro-inflammatory cytokines to induce neutrophil migration to the inflamed oral epithelium. PLAG ameliorated the degree of OM by terminating the necroptosis signaling pathway. These data suggest that PLAG may be a useful therapeutic agent for the treatment of CRIOM. Citation Format: Solji Choi, Su-Hyun Shin, Sun Young Yoon, Ji Sun Park, Ki-Young Sohn, Jae Wha Kim. 1-Palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol ameliorates chemoradiation-induced oral mucositis in a mouse model by regulating necroptosis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6175.