Table 1.

Summary of DDR-associated genes, how they can be epigenetically regulated and their involvement in drug response.

Gene	Symbol	Summary	Reference Number
O6-Methylguanine-DNA Methyltransferase	MGMT	Methylated associated with increased sensitivity to temozolomide. Enhancer region associated with increased expression and resistance to temozolomide.	[1,3,5,6,26]
Breast Cancer type 1 susceptibility protein	BRCA1	Methylated associated with sensitivity to PARPi/platinum and loss of H3K27ac at enhancer regions.	[7,8,11,12,27,35]
Breast Cancer type 2 susceptibility protein	BRCA2	Deficiency causes chromatin conformation changes and increased sensitivity to PARPi/platinum.	[7,8,11,12,28]
MutL Homolog 1	MLH1	Unmethylated associated with temozolomide/platinum resistance and loss of MMR.	[15,16,17,31]
FA Complementation Group F	FANCF	Methylation associated with sensitivity to platinum, unmethylated associated with platinum resistance.	[24,25]
FA Complementation Group A	FANCA	Germline mutation associated with increased sensitivity to DNA damaging agents.	[36]
DNA Repair Protein RAD51 homolog 1	RAD51	High expression associated with platinum resistance.	[37]
X-ray Repair Cross Complementing 2	XRCC2	Low expression associated with sensitivity to PARPi.	[38]
X-ray Repair Cross Complementing 3	XRCC3	Low expression associated with sensitivity to PARPi.	[38]
DNA Polymerase Delta 4	POLD4	Low expression associated with sensitivity to PARPi/platinum.	[39]
RAD51 Paralog C	RAD51C	Reversion mutations associated with increased resistance to PARPi.	[52]
RAD51 Paralog D	RAD51D	Reversion mutations associated with increased resistance to PARPi.	[52]
Euchromatic Histone Lysine Methyltransferase 2	EHMT2	Maintains repressive H3K9 methylation marks. Recruits HR-associated factors, Inhibition of EHMT2 promotes DNA damage.	[58,59,63,64,66]
Enhancer of Zeste Homolog 2	EZH2	Maintains repressive H3K27 methylation marks. Controls expression of multiple DDR-associated genes. Inhibition of EZH2 sensitises cells to PARPi.	[58,59,60,61,66]