Fig. 2: Low BMI promote tumor growth via ghrelin activated neuronal NPY.

A Pearson correlation between BMI and plasma ghrelin levels in cancer-free subjects (n = 97) using a publicly available dataset (two-tailed; 95% CI shaded). B Left: Schematic of in vivo metastasis assay. Female C57BL/6 mice (5-6 weeks) were fed with a standard diet and administered ghrelin (0.05 mg/kg; i.p.; 5 shots) for 10 days before CMT167 cells injection (5 × 10⁴; i.c.). In vivo (middle) and ex vivo (right) BLI quantification of brain metastasis in control (n = 5) and ghrelin-treated normal BMI mice (n = 6) [two-way ANOVA with Tukey’s test (in vivo); unpaired two-tailed t-test (ex vivo)]. C Relative GHSR expression in human brain cells (HMC3, UC1, primary neurons) and lung cancer cell lines (PC9BrM, H2030BrM, CMT167) by qRT-PCR, normalized to β-Actin (n = 3 independent experiments, unpaired two-tailed t-test). D Colony formation of H2030BrM cells treated with or without CM from indicated brain cells (n = 3 independent experiments, unpaired two-tailed t-test). E MTS (left) and colony (right) assays of H2030BrM cells treated with or without CM from ghrelin-treated primary neurons (0.01 nM-0.25 nM; n = 3 independent experiments, two-way ANOVA with Tukey’s test). F Strategy to identify low BMI-specific brain secretory factors using GTEx and HPA database (n = 382). G qRT-PCR of indicated genes in primary neurons treated with or without rGhrelin (0.25 nM, 12 h, normalized to β-Actin; n = 3 independent experiments, unpaired two-tailed t-test). H Expression of Npy, Gh1 and Prl in brains of normal and low-BMI mice (Fig. 1D) by qRT-PCR (normalized to β-Actin; n = 3 independent experiments, unpaired two-tailed t-test). I NPY protein levels in CM from untreated and ghrelin-treated (0.25 nM) neurons by ELISA (n = 3 independent experiments, unpaired two-tailed t-test). J, K MTS and colony assays of H2030BrM cells treated with rNPY [10–100 nM, short-term (J); 100 nM, long-term (K)]; (J: n = 3 independent experiments, two-way ANOVA with Tukey’s test; K: n = 3 independent experiments, unpaired two-tailed t-test). L Dot plot (left) and quantification (right) of BrdU-based cell cycle analysis of H2030BrM cells treated with or without rNPY (100 nM; n = 3 independent experiments, unpaired two-tailed t-test). M Western blot (upper) and ImageJ quantification (lower) of GHSR signaling proteins in neurons treated with or without rGhrelin (0.01-0.25 nM, 24 h; normalized to GAPDH; n = 3 independent experiments, unpaired two-tailed t-test). All data are mean ± S.E.M. Source data are provided as a Source Data file.