Non-invasive fecal metabonomic detection of colorectal cancer

Figures & data

Figure 1. Fecal metabonomic profile of CRC patients and healthy subjects. (A) Typical GC/TOFMS chromatograms of fecal specimens from a CRC patient and a healthy subject (Hl). (B) PCA model 2 differentiating CRC patients from healthy subjects (Hl). (C) OPLS-DA model 2 differentiating CRC patients from healthy subjects (Hl). (D) Validation plot of OPLS-DA model 2.

Table 1. Performance statistics of models 1 (all samples included) and 2 (fecal samples containing blood beyond 1 mg Hb/g stool excluded)

Model	No of samples included	Unsupervised PCA			Supervised OPLS-DA
		R^2X (cum)	Q^2 (cum)	Clustering of QC samples	R^2X (cum)	R^2Y (cum)	Q^2 (cum)	AUC of ROC^a	Permutation testing^b
									N (Q^2 permuted > Q^2 original)^c	y intercept^d
1	CRC (n = 11), Hl (n = 10)	0.212	0.139	Yes	0.373	0.995	0.215	1	17	Negative
2	CRC (n = 8), Hl (n = 10)	0.222	0.138	Yes	0.407	0.996	0.35	1	2	Negative

^a ROC analysis was performed using the cross-validated predicted Y-values. Corresponding AUCs were determined. ^bPermutation testing was performed on the parent PLS-DA models that contained the same number of components. ^cNumber of permuted classifications with Q² values exceeding that on the actual classification of samples. ^dy intercept of the regression line fitted among the Q² values.

Table 2. Fecal and tissue marker metabolites characterizing CRC

Fecal marker metabolites differentiating CRC patients and healthy subjects
Metabolite identity	Fold change^a	S.I.^b	R.I.^c
Nicotinic acid	0.25	91	1269.3
Fructose ^d	0.26/0.27	84/82	1928.4/1937.8
Linoleic acid	0.31	92	2200.9
Tissue marker metabolites differentiating CRC tumor and matched normal mucosae
Metabolite identity	Fold change^e	S.I.^b	R.I.^c
Glucose	0.10	88	1940.0
Galactose	0.11	78	1894.9
3-phosphoglycerate	0.32	82	1824.2
Citric acid	0.35	85	1843.7
Uracil	4.06	90	1328.6
Uridine	3.21	60	2445.2
Inosine	0.46	82	2583.4
Proline	2.12	88	1155.9
Creatinine	0.49	87	1558.3

^a Fold change less than 1 indicates lower level in the feces of CRC patients compared with healthy subjects; ^bS.I.: Similarity Index (the percentage by which the mass spectrum of the analyte matches that in the library); ^cR.I.: Retention Index of the derivatized metabolites; ^dDerivatized metabolites were present as multiple peaks in the chromatogram; ^eFold change more than 1 indicates higher level in the tumor tissue compared with matched normal mucosae; fold change less than 1 indicates lower level in the tumor tissue compared with matched normal mucosae.

Figure 2. Tissue metabonomic profile of tumor tissue and matched normal mucosae. (A) PCA scores plot discriminating CRC tumor (T) from matched normal mucosae (M). (B) OPLS-DA scores plot discriminating CRC tumor (T) from matched normal mucosae (M). (C) Validation plot of OPLS-DA model.

Table 3. Clinical characteristics of CRC patients and healthy subjects

Characteristics	CRC patients (n = 11)	Healthy subjects (n = 10)	P value
Age, years
Mean	64.5	57.4	0.090^a
Range	56–80	48–79
Sex, no. (%)
Male	7 (63.6)	4 (40.0)	0.395^b
Female	4 (36.4)	6 (60.0)
Tumor site, no. (%)
Sigmoid	2 (18.2)
Rectosigmoid	2 (18.2)
Rectum	7 (63.6)
Dukes’ stage no. (%)
B	6 (54.5)
C	5 (45.5)
Grade
Well differentiated	1 (9.1)
Moderately differentiated	10 (90.9)

^aIndependent samples t test; ^bFisher exact test.