Table 5.

Examples of genetic variants that modify colorectal cancer and/or polyp risk^a

Gene	Symbol	Locus	Ref	Associations and effects on colon cancer and polyp risk
adenomatous polyposis coli	APC I1307K	5q21	84, 87	Moderate risk for adenomas
	APC D1822V			Increases colon adenoma risk in smokers
	APC T1493T			Modifies presentation of FAP
colorectal associated cancer 1	CRAC1/HMPS	15q13.3	63, 64	Associated with some cases of hyperplastic polyposis and there are probable environmental modifier(s)
cyclin D1	CCND1 P241P	11q13.3	91	Causes younger age on onset in Lynch syndrome; but decreased risk in sporadic cases with exposure to estrogen
cytochrome P450 family 24 subfamily A	CYP24A1	20q13.2	92	Associated with increased site-specific CRC risk, with possible ethnicity influence.
cytochrome P450 family 24 subfamily B	CYP24B1	20q13.2	92	Alters proximal CRC risk when associated with UV-spectrum sun exposure
glutathione S-transferase mu 1	GSTM1	1p13.3	83	Modifies presentation of Lynch syndrome, Ethnic and smoking factors modulate population risk in null allele carriers.
glutathione S-transferase theta 1	GSTT1	22q11.23	83	Modifies presentation of Lynch syndrome, Ethnic and smoking factors modulate population risk in null allele carriers.
glutathione S-transferase Pi	Gstp1 (mouse)		73	Modifies adenoma number and age-of-onset in Min mice
hemochromatosis protein	HFE	6p22.2	82	Modifies presentation of Lynch syndrome
insulin-like growth factor 1A	IGF-1	12q23.2	81	Modifies presentation of Lynch syndrome, possibly interacting with diabetes
insulin-like growth factor binding protein-3	IGFBP-3	7p12.3	76	Modifies colon cancer risk interacting with diabetes
N-acetyltransferase 1	NAT1	8p22	84	Modifies presentation of FAP and affects sporadic cancer risk in association with certain certain environmental factors
N-acetyltransferase 2	NAT2	8p22	84	Modifies presentation of FAP and affects sporadic cancer risk in association with certain certain environmental factors
ornithine decarboxylase 1	ODC	2p16.3	97	Modifies adenoma risk interacting with NSAID use
selenoprotein P	SEPP1	5p12	95, 96	Modifies adenoma risk interacting with certain dietary factors and smoking
thioredoxin reductase 1	TXNRD1	12q23.3	95	Modifies adenoma risk interacting with certain dietary factors and smoking
transcription factor 7-like 2 isoform 2	TCF7L2	10q25	74, 75	Modifies CRC risk, possibly in association with diabetes
transforming growth factor, beta receptor I	TGFBR1	9q22.33	77, 78	Modifies CRC risk in high risk families, and in Min mice.
tumor protein 53	TP53	17p13.1	90	Causes Li Fraumeni syndrome; certain alleles also modify sporadic site-specific colon cancer risk in a gender-dependent manner

^aThe data in this table and paper refer to recent research studies, which require further study to justify clinical application.