Diverse expression patterns of mucin 2 in colorectal cancer indicates its mechanism related to the intestinal mucosal barrier

Table 1 Comparison of mucin 2 expression in normal and cancer tissues of patients with colorectal cancer (cases)

Group	MUC2 expression		χ2	P value
	Low	High
Normal tissues	21	79	14.028	< 0.011
Cancer tissues	46	54

¹Indicates that the difference was statistically significant, which confirmed that the expression difference of mucin 2 (MUC2) in normal tissues and cancer tissues was statistically significant, and the high expression rate of MUC2 in cancer tissues was lower than that in normal tissues. MUC2: Mucin 2.

Table 2 Relationship between expression of mucin 2 and clinicopathological parameters in patients with colorectal cancer, n (%)

Clinicopathological parameter	n (%)	MUC2 expression		χ2	P value
		Low, n (%)	High, n (%)
Age, yr
≤ 60	48	22 (45.8)	26 (54.2)	0.001	0.974
> 60	52	24 (46.2)	28 (53.8)
Gender
Male	52	23 (44.2)	29 (55.8)	0.137	0.712
Female	48	23 (47.9)	25 (52.1)
Tumor location
Rectum and anus	48	21 (43.8)	27 (56.3)	0.188	0.664
Colon	52	25 (48.1)	27 (51.9)
TNM stage
I-II	57	17 (29.8)	40 (70.2)	13.963	< 0.01
III	43	29 (67.4)	14 (32.6)
Maximum tumor diameter
< 5 cm	49	23 (46.9)	26 (53.1)	0.034	0.854
≥ 5 cm	51	23 (45.1)	28 (54.9)
Depth of invasion
Non-immersed serosa	22	8 (36.4)	14 (63.6)	1.054	0.304
Immersed serosa	78	38 (48.7)	40 (51.3)
Degree of differentiation
High-moderate	93	42 (45.2)	51 (54.8)	F1	0.700
Low	7	4 (57.1)	3 (42.9)
Tumor type
Mucinous adenocarcinoma	13	5 (38.5)	8 (61.5)	0.342	0.559
Non-mucinous adenocarcinoma	87	41 (47.1)	46 (52.9)
Lymph node metastasis
No	56	17 (30.4)	39 (69.6)	12.538	< 0.01
Yes	44	29 (65.9)	15 (34.1)

¹Fisher exact test was used when the expected frequency was less than 1. Due to the small number of patients with stage I, in order to reduce bias, we combined the stage I with stage II patients for analysis. Similarly, there was only one patient with highly differentiated colorectal cancer, so the patient was combined with patients with moderately differentiated disease. It can be seen from the above table that the expression of mucin 2 is correlated with tumor-node-metastasis stage and lymph node metastasis in colorectal cancer patients. MUC2: Mucin 2; TNM: Tumor-node-metastasis.

Table 3 Comparison of serum levels of diamine oxide, D-lactate, and mucin 2 between colorectal cancer patients and normal control (mean ± SD)

Group	n (%)	DAO (pg/mL)	D-LAC (μg/L)	MUC2 (ng/L)
Normal control	20	158.21 ± 15.98	973.69 ± 128.08	305.98 ± 31.50
CRC	66	185.40 ± 25.49	1216.93 ± 204.20	364.58 ± 48.30
P value		< 0.01	< 0.01	< 0.01

There were 66 cases of colorectal cancer (CRC) and 20 cases of normal controls. Serum levels of mucin 2, diamine oxide, D-lactate in CRC patients were higher than those in the normal control group. MUC2: Mucin 2; DAO: Diamine oxide; D-LAC: D-lactate; CRC: Colorectal cancer.

Table 4 Relationship between serum levels of mucin 2, diamine oxide, and D-lactate in patients with colorectal cancer (cases)

MUC2	DAO		D-LAC
	Low	High	Low	High
Low	15	8	16	7
High	17	26	15	28
χ2	3.957		7.236
P value	0.047		0.007

The measured mucin 2 (MUC2) level of P95 in the normal population was taken as the normal reference range, and those beyond P95 were regarded as increased, otherwise as decreased. Based on this, colorectal cancer patients were divided into groups with high and low levels of MUC2. Similarly, the number of cases in diamine oxide (DAO) and D-lactate (D-LAC) groups with high and low levels could be obtained. Serum MUC2 levels were positively correlated with DAO and D-LAC levels. Low: Low serum level; High: High serum level; MUC2: Mucin 2; DAO: Diamine oxide; D-LAC: D-lactate.

Table 5 Relationship between serum levels of mucin 2 and clinicopathological parameters in patients with colorectal cancer, n (%)

Clinicopathological parameter	n (%)	Serum MUC2 expression		χ2	P value
		Low, n (%)	High, n (%)
Age, yr
≤ 60	30	11 (36.7)	19 (63.3)	0.080	0.777
> 60	36	12 (33.3)	24 (66.7)
Gender
Male	38	12 (31.6)	26 (68.4)	0.422	0.516
Female	28	11 (39.3)	17 (60.7)
Tumor location
Rectum and anus	24	10 (47.1)	14 (58.3)	0.772	0.380
Colon	42	13 (31.0)	29 (65.2)
TNM stage
I-II	36	16 (44.4)	20 (55.6)	6.687	0.033
III	21	7 (33.3)	14 (66.7)
IV	9	0 (0.0)	9 (100.0)
Maximum tumor diameter
< 5 cm	33	12 (36.4)	21 (63.6)	0.067	0.796
≥ 5 cm	33	11 (33.3)	22 (66.7)
Depth of invasion
Non-immersed serosa	12	5 (41.7)	7 (58.3)	0.300	0.584
Immersed serosa	54	18 (33.3)	36 (66.7)
Degree of differentiation
High-moderate	60	21 (38.3)	39 (61.7)	F1	1.000
Low	6	2 (33.3)	4 (66.7)
Tumor type
Mucinous adenocarcinoma	14	8 (57.1)	6 (42.9)	21.241	< 0.01
Non-mucinous adenocarcinoma	52	15 (32.7)	37 (67.3)
Lymph node metastasis
No	36	16 (44.4)	20 (55.6)	3.212	0.073
Yes	30	7 (23.3)	23 (76.7)
Distant metastasis
No	57	23 (40.4)	34 (59.6)	F1	0.022
Yes	9	0 (0.0)	9 (100.0)

¹Fisher exact test was used when the expected frequency was less than 1. Due to the small number of patients with stage I, in order to reduce bias, we combined the stage I with stage II patients for analysis. Similarly, there was only one patients with highly differentiated colorectal cancer, so this patient was combined with the patients with moderately differentiated disease. Serum levels of mucin 2 was correlated with tumor-node-metastasis stage, tumor type, and distant metastasis in colorectal cancer patients. MUC2: Mucin 2; TNM: Tumor-node-metastasis.