Fig. 6

Hierarchical clustering analysis and VIP score plots of PLS-DA of 22 metabolites in 120 samples from 20 patients with cT3 and cT4 stage tumors. a Hierarchical clustering analysis of 22 metabolites in 120 samples from 20 patients with cT3- and cT4-stage tumors. Metabolite levels were used to color code individual samples from blue (low concentration) to purple (high concentration). Tree clusters and shorter Euclidean distances indicate greater similarities between samples or metabolites. The red, green, and blue colors of the top bars represent groups 1, 2, and 3, and the other colors represent groups 4, 5, and 6. b The VIP score plots of PLS-DA in positive ion mode. c The VIP score plots of PLS-DA in negative ion mode. The vertical coordinate represents the M/Z of each metabolite, and the horizontal coordinate is the weight value of each metabolite. It can be seen from the score plot that there are 3 metabolites in the positive ion mode and 4 in the negative ion mode. PLS-DA: partial least squares discriminant analysis