Characteristics of the Study Population
Clinical and pathological characteristics of the study population are summarized in Table 1 and are presented in supplemental file 1. GATA3 and mammaglobin IHC results were available for 189 and 183 patients, respectively. Only patients with IHC results underwent further analysis. Among 189 female patients with invasive ductal carcinomas diagnosed from 2000 to 2010, the luminal A subtype was most frequent constituting 43.8% of the study population. TNBC was the second most common subtype representing 33.3% of the total number and were purposely overrepresented to improve the study of TNBC in African American women. It is noteworthy that 75% of the TNBCs demonstrated basal-like phenotype, which was determined by cytokeratin 5/6 immunohistochemistry. More than two-thirds of the tumors were stage I and II; however, the tumors tended to be of high grade, with Grade 3 tumors comprising 67.3% of the total in the study population. A summary of the patient clinicopathological features, molecular profiles and IHC expression status can be found in figure 1 which shows expression of GATA3 and mammaglobin primarily in luminal A and luminal B tumors.
Table 1. Clinical and pathological characteristics of study population.
Parameter
|
Category
|
Frequency
|
%
|
Age (years)
|
|
|
|
|
<50
|
57
|
28.2
|
|
≥50
|
145
|
71.8
|
ER status (n=201)
|
|
|
|
|
Positive
|
116
|
57.7
|
|
Negative
|
85
|
42.3
|
PR status
|
|
|
|
|
Positive
|
90
|
47.1
|
|
Negative
|
101
|
52.9
|
HER2 status
|
|
|
|
|
Positive
|
28
|
13.9
|
|
Negative
|
173
|
86.1
|
Subtype*
|
|
|
|
|
Luminal A
|
88
|
43.8
|
|
Luminal B
|
29
|
14.4
|
|
Her2
|
17
|
8.5
|
|
Triple-negative
|
67
|
33.3
|
Pathologic stage (n=197)
|
|
|
|
|
Stage 1
|
62
|
31.5
|
|
Stage 2
|
82
|
41.6
|
|
Stage 3
|
41
|
20.8
|
|
Stage 4
|
12
|
6.1
|
Grade
|
|
|
|
|
Grade I
|
9
|
4.5
|
|
Grade II
|
57
|
28.2
|
|
Grade III
|
136
|
67.3
|
Recurrence
|
|
|
|
|
None
|
136
|
67.3
|
|
Loco-regional
|
11
|
5.4
|
|
Distant
|
21
|
10.4
|
|
Never disease-free
|
18
|
8.9
|
|
Unknown
|
16
|
7.9
|
ER: estrogen receptor; PR: progesterone receptor; HER2: Human Epidermal Growth Factor Receptor 2
Luminal A: ER+ or PR+, HER2-; luminal B: ER+ or PR+, HER2+; triple-negative: ER-, PR-, HER2-; HER2+: ER-, PR-, HER2+
GATA3
Figure 2 demonstrates GATA3 staining intensities where 2a, 2c, 2e, and 2g demonstrate no, weak, moderate, and strong immunoreactivity. 2a shows a TNBC with no GATA3 immunoreactivity (Reactivity score=0, H-score =0). 2c shows weak GATA3 immunoreactivity (Reactivity score = 1, H-score=60) in a luminal A patient. 2e shows moderate diffuse immunoreactivity in a luminal B patient (Reactivity score = 2, H-score=270) and 2g shows strong diffuse immunoreactivity in a luminal A patient (Reactivity score = 3, H-score=300). Figure 3 demonstrates mean H-scores by subtype. GATA3 was expressed in 67.7% (128/189) of all tumors. However, GATA3 had the highest H-score expression in Luminal A (mean=218.88 ± 77.34 SD) and Luminal B (mean=212.12 ± 75.62 SD) tumors, whereas mean GATA3 H-scores were lowest in HER2 (mean=33.82 ± 71.71 SD) overexpressing and TNBCs (mean=33.20 ± 68.56 SD) (ANOVA p<0.001).
Following the dichotomization of H-scores, the frequency of positive and negative expression of GATA3 was determined for clinicopathological characteristics. GATA3 expression showed statistically significant association with a lower grade (p<0.001), ER positivity (p<0.001), or PR positivity (p<0.001) (Table 2). GATA3 was expressed in 97% and 98% and 58% of ER, PR, and HER2 positive tumors, respectively (Table 2). Among the molecular breast cancer subtypes, GATA3 was expressed in 98%, 96%, 35%, and 23% of Luminal A, Luminal B, HER2 overexpressing and TNBC subtypes, respectively, and was found to be associated with the luminal subtype (p<0.001).
Table 2. Summary of staining results for GATA3 and mammaglobin and their association with molecular and clinicopathological features.
|
|
GATA3 Expression
|
|
Mammaglobin Expression
|
|
|
|
|
No or Low Expression
|
High Expression
|
|
No or Low Expression
|
High Expression
|
|
|
|
n=61
|
%
|
n=128
|
%
|
p value
|
n=79
|
%
|
n=104
|
%
|
p value
|
Estrogen Receptor
|
|
|
|
|
|
|
|
|
|
|
|
|
Negative
|
58
|
73%
|
21
|
27%
|
|
39
|
50%
|
39
|
50%
|
|
|
Positive
|
3
|
3%
|
107
|
97%
|
<0.001
|
40
|
38%
|
65
|
62%
|
0.07
|
Progesterone Receptor
|
|
|
|
|
|
|
|
|
104
|
|
|
|
Negative
|
59
|
61%
|
38
|
39%
|
|
48
|
50%
|
48
|
50%
|
|
|
Positive
|
2
|
2%
|
90
|
98%
|
<0.001
|
31
|
36%
|
56
|
64%
|
0.022
|
HER2
|
|
|
|
|
|
|
|
|
|
|
|
|
Negative
|
50
|
31%
|
113
|
69%
|
|
67
|
43%
|
90
|
57%
|
|
|
Positive
|
11
|
42%
|
15
|
58%
|
0.17
|
12
|
46%
|
14
|
54%
|
0.45
|
Subtype
|
|
|
|
|
|
|
|
|
|
|
|
|
Luminal A
|
2
|
2%
|
83
|
98%
|
|
30
|
38%
|
50
|
63%
|
|
|
Luminal B
|
1
|
4%
|
25
|
96%
|
|
11
|
42%
|
15
|
58%
|
|
|
HER2 overexpressing
|
11
|
65%
|
6
|
35%
|
|
7
|
41%
|
10
|
59%
|
|
|
Triple Negative
|
47
|
77%
|
14
|
23%
|
<0.001
|
31
|
52%
|
29
|
48%
|
0.415
|
Triple Negative Status*
|
|
|
|
|
|
|
|
|
|
|
|
|
Non-Triple Negative
|
12
|
10%
|
114
|
91%
|
|
48
|
40%
|
73
|
60%
|
|
|
Triple Negative
|
48
|
77%
|
14
|
23%
|
<0.001
|
31
|
51%
|
30
|
49%
|
0.1
|
Luminal Status
|
|
|
|
|
|
|
|
|
|
|
|
|
Non-Luminal
|
58
|
74%
|
20
|
26%
|
|
38
|
49%
|
39
|
51%
|
|
|
Luminal
|
3
|
3%
|
108
|
97%
|
<0.001
|
41
|
39%
|
65
|
61%
|
0.09
|
Grade
|
|
|
|
|
|
|
|
|
|
|
|
|
Grade I + II
|
5
|
0%
|
57
|
92%
|
|
20
|
32%
|
42
|
68%
|
|
|
Grade III
|
56
|
44%
|
71
|
56%
|
<0.001
|
61
|
48%
|
67
|
52%
|
0.031
|
Stage*
|
|
|
|
|
|
|
|
|
|
|
|
|
Stage 1
|
19
|
32%
|
40
|
68%
|
|
18
|
33%
|
36
|
67%
|
|
|
Stage 2
|
22
|
29%
|
53
|
71%
|
|
38
|
51%
|
37
|
49%
|
|
|
Stage 3
|
14
|
36%
|
25
|
64%
|
|
16
|
41%
|
23
|
59%
|
|
|
Stage 4
|
6
|
50%
|
6
|
50%
|
0.534
|
5
|
42%
|
7
|
58%
|
0.478
|
*Missing Data not included
IHC expression of GATA3 was not associated with overall survival or disease-free survival (Figure 4). However, after grouping all luminal subtypes with GATA3 positive tumors and comparing them non-luminal and GATA3 negative tumors, there was a marginal significance with overall survival (4A, log rank p=0.073); mean months survival for the luminal and GATA3 positives was 142.55 months compared to 89.15 months. However, there was no association with recurrence-free survival (4B, log rank p=0.19)
Mammaglobin
Figure 2 demonstrates mammaglobin staining intensities where 2b, 2d, 2e, and 2h demonstrate no, weak, moderate, and strong immunoreactivity. 2b shows a HER2 overexpressing subtype patients with no mammaglobin immunoreactivity (Reactivity score=0, H-score =0). 2d shows weak mammaglobin immunoreactivity (Reactivity score = 1, H-score=60) in a luminal A patient. 2f shows moderate immunoreactivity in a luminal B patient (Reactivity score = 2, H-score=270) and 2h shows strong immunoreactivity in a TNBC patient (Reactivity score = 3, H-score=300). Mammaglobin was expressed in 56.8% (104/183). Mean mammaglobin H-scores were 102.06 (±110.62 SD), 78.92 (±106.55 SD), 69.82 (± 101.71), and 53.53 (±78.40 SD) for the luminal A, luminal B, HER2+, and TNBC subtypes, respectively (ANOVA p=0.23).
Mammaglobin expression was also significantly associated with a lower grade (p=0.031), ER positivity (p=0.07), or PR positivity (p=0.022). The frequency of positive and negative expression of mammaglobin was determined for clinicopathological characteristics. Mammaglobin was expressed in 62%, 64%, and 54% of ER, PR, and HER2 positive tumors, respectively (Table 2). Positive mammaglobin expression was found in 63%, 58%, 59%, and 48% of Luminal A, Luminal B, HER2 overexpressing and TNBC subtypes, respectively, and was found to be associated with the non-TNBC subtype (p<0.043). IHC expression of mammaglobin was not associated with overall survival or disease-free survival even after grouping the luminal subtypes with mammaglobin positive tumors and comparing to non-luminals= subtypes with negative mammaglobin expression (Figure 4C, D).
GATA3 and Mammaglobin co-expression
There was a significant correlation between GATA3 and mammaglobin expression (Pearson correlation= 0.17; p=0.022). Therefore, the sensitivity of GATA3 and mammaglobin by subtype were analyzed alone and in combination. GATA3 could detect 97% of luminal tumors and 23% of TNBCs (Table 3). However, mammaglobin had 64% sensitivity in luminal tumors. Co-expression of both markers decreased the overall detection sensitivity of luminal tumors from 97% to 86%. The expression of at least one marker was found in 43% (34/80) of TNBCs. However, co-expression of GATA3 and mammaglobin reduced the sensitivity of detecting TNBCs to 7%. In fact, 76% of TNBCs were GATA3 and mammaglobin negative.
Table 3. Combined expression of GATA3 and mammaglobin in luminal and triple negative breast tumors from African American women.
|
Luminal Tumors
|
Triple negative tumors
|
|
+
|
-
|
Sensitivity
|
+
|
-
|
Sensitivity
|
GATA3 positive
|
108
|
3
|
97%
|
14
|
48
|
23%
|
Mammaglobin positive
|
70
|
40
|
64%
|
30
|
33
|
48%
|
GATA3 negative and mammaglobin negative
|
1
|
28
|
3%
|
22
|
7
|
76%
|
GATA3 positive and mammaglobin positive
|
63
|
10
|
86%
|
5
|
68
|
7%
|
Either GATA3 or mammaglobin positive
|
42
|
39
|
52%
|
34
|
46
|
43%
|