Polymorphisms in base excision repair genes: Breast cancer risk and individual radiosensitivity

Table 1 List of meta-analyses on X-ray repair cross-complementing group 1 single nucleotide polymorphisms and haplotypes and risk of breast cancer

Ref.	XRCC1 SNPs	Number of studies analysed	Result
Huang et al[17]	Arg399Gln	37	The 399Gln variant allele is associated with an increased risk of BC
	Arg194Trp	18
	Arg280His	8
Li et al[18]	Arg399Gln	40	The recessive effect of the 399Gln variant allele increases the risk of BC (significant only in Asians)
	Arg194Trp	21
	Arg280His	9
Wu et al[19]	Arg399Gln	44	This SNP is associated with increased BC risk in Asians and Africans
Saadat et al[20]	Arg399Gln	36	This SNP is associated with increased BC risk in Asians
Yi et al[13]	Arg399Gln	54	This SNP is associated with increased risk of BC in Asians and Indians
	XRCC1 haplotypes
Saadat[21]	Arg399Gln	10	The Arg194-Gln399 haplotype is associated with increased BC risk in Asians
	Arg194Trp

XRCC1: X-ray repair cross-complementing group 1; SNP: Single nucleotide polymorphism; BC: Breast cancer; Arg: Arginine; Gln: Glutamine; His: Histidine; Trp: Tryptophan.

Table 2 List of meta-analyses on 8-oxoguanine DNA glycosylase 1, apurinic/apyrimidinic endonuclease 1 and poly (ADP-ribose) polymerase-1 single nucleotide polymorphism and risk of breast cancer

Ref.	BER gene	SNPs	Number of studies analysed	Result
Yuan et al[27]	OGG1	Ser326Cys	10	This SNP is significantly associated with a protective effect against BC in European subjects (additive and dominant model)
Ding et al[28]	OGG1	Ser326Cys	4	There was a lack of association between this SNP and BC risk in a European population
Gu et al[29]	OGG1	Ser326Cys	11	There was a lack of association between this SNP and BC risk
Wei et al[33]	OGG1	Ser326Cys	12	This SNP did not have a significant effect on BC
Wu et al[35]	PARP-1 (ADPRT)	Val762Ala	6	There was no association between this SNP and BC (all genetic models)
Wu et al[35]	APE1	Asp148Glu	5	There was no association between this SNP and BC (all genetic models)

OGG1: 8-oxoguanine DNA glycosylase 1; APE1: Apurinic/apyrimidinic endonuclease 1; PARP-1: Poly (ADP-ribose) polymerase-1; SNP: Single nucleotide polymorphism; BC: Breast cancer; BER: Base excision repair; Ser: Serine; Cys: Cysteine; Val: Valine; Ala: Alanine; Asp: Aspartic acid; Glu: Glutamic acid; ADPRT: ADP ribosyl transferase.

Table 3 Association between X-ray repair cross-complementing group 1 single nucleotide polymorphisms and radiotherapy-induced side effects in breast cancer patients

Ref.	XRCC1 SNPs	Number of studies analysed	Result
Xie et al[38]	Arg399Gln	8	The 399Gln variant allele is associated with a higher risk of RT-induced toxicity (only in some subgroups of BC patients)
	Arg194Trp	6	No predictive value was found for this SNP
	-77 T > C	4	No predictive value was found for this SNP
	Arg280His	4	The 280His variant allele is protective against RT-induced toxicity (in BC patients treated with RT only)

XRCC1: X-ray repair cross-complementing group 1; SNP: Single nucleotide polymorphism; RT: Radiotherapy; BC: Breast cancer; Arg: Arginine; Gln: Glutamine; Trp: Tryptophan; His: Histidine; T: Thymine; C: Cytosine.