Estrogen receptor alpha gene amplification in breast cancer: 25 years of debate

Table 1 Published studies testing interrelations of estrogen receptor alpha gene (ESR1) amplification with estrogen receptor alpha protein expression over cases, studies are separated for test results by correlation or association and no correlation or association found

	Ref.	Patients (n)	ESR1 CNI (%)	ERα-negative CNI (%)	Method for CNI detection
Correlation or association found
1	Nembrot et al[1]	22	27.3	0	Western blot
2	Holst et al[24]	1652	36.1	1.3	FISH
3	Tomita et al[25]	133	33.8	0	FISH
4	Moelans et al[28]	135	8.1	27.3	MLPA
5	Tsiambas et al[50]	60	21.6	-	FISH
6	Dunbier et al[95]	44	20.5	0	Gene chip
7	Laenkholm et al[96]	220	42.4	8.8	FISH
8	Singer et al[41]	394	47.5	1	FISH
9	Lin et al[67]	150	12.7	5.9	FISH
10	Pentheroudakis et al[97]	1010	58.8	12.5	FISH
11	Li et al[93]	219	-	-	Gene chip
12	Soysal et al[3]	58	15.5	0	FISH
No correlation or association not found
1	Watts et al[30]	37	2.7	0	Western blot
2	Reis-Filho et al[34]	70	11.4	25	Gene chip
3	Vincent-Salomon et al[35]	341	0.9	66.70%	Gene chip
4	Moelans et al[125]	39	Approximately 20	-	MLPA
5	Ooi et al[39]	51	5.9	0	FISH/MLPA
6	Markiewicz et al[99]	281	11.7	66.7	qPCR
7	Chen et al[2]	301	8.6	46.2	FISH

Studies are separated with regard to correlation or association and no correlation or association. Frequency of ESR1 copy number increase (CNI), size (n) of study cohort, and proportions of ERα negative (ERα-) tumors in cases with ESR1 CNI, as available. MLPA: Multiplex ligation-dependent probe amplification; FISH: Fluorescence in situ hybridization; qPCR: Quantitative polymerase chain reaction.