Fig. 8: Decoy peptide DMp39 targets DLAT-mediated MTHFD2 acetylation and increases tumor chemosensitivity in vitro and in vivo.
a The structure of MTHFD2. K44 containing α-helix in MTHFD2, is marked in purple. The amino acid sequence of DMp39 is shown at the top. b HPLC-based in vitro serum stability assay of DMp39. DMp39 (0.2 mg) was incubated for indicated times with pre-warmed 50% serum and applied to HPLC. The remaining DMp39 is shown by the heights of the respective elution peaks. c Cells were treated with the indicated concentrations of DMp39 before detection of MTHFD2 K44 acetylation. d, e Effect of DMp39 on cisplatin sensitivity. DMp39 (20 μM) and cisplatin (2 or 5 μg/ml) were administered for 48 h. MTHFD2 acetylation, apoptotic cell death, and cell viability were determined. f Organ toxicity of the cisplatin and cy7-DMp39 combination in mice. Mice were injected with 0.1 mg/kg DMp39 and 5 mg/kg cisplatin from 7 days post xenograft 2 times/week for 22 days. The positive control group was administered 10 mg/kg/day of cisplatin for 3 consecutive days. Liver, kidney, and spleen toxicity were assessed by serum alanine aminotransferase, cystatin C, and spleen index (spleen weight (mg)/body weight (g) x 10), respectively. g Efficacy test of Cy7-DMp39 in vivo. Cy7 or cy7-DMp39 and cisplatin were administered as described in (f), and fluorescence was imaged and quantified in mice with KB-3-1cisR-derived xenograft tumors (g; left) and with lung cancer patient-derived xenograft tumors (g; right). MTHFD2 and Ac-K44 MTHFD2 levels in tumors were assessed by co-immunoprecipitation of MTHFD2. Effect of DMp39, cisplatin, and the combination on tumor growth (h, k) and weight (i, l) in KB-3-1cisR and lung cancer PDX tumor-bearing mice. Representative images of the tumors at the endpoint are presented in (h) and (k). Ac-K44 MTHFD2, MT-CO2, and DLAT levels in both xenograft mouse tumors were assessed by IHC staining (j, m). Scale bars in (h) and (k) represent 10 mm and 25 μm in (j) and (m). Results are presented as mean ± SEM for (h, k) and mean ± SD for the rest. n = 3 per group for (e, f), n = 6 for (g) left, n = 5 for (g) right, n = 6 for (h–j), and n = 5 for (k–m). P values were obtained by one-way ANOVA. Source data are provided as a Source Data file.
