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Mucin expression in mucinous carcinoma and other invasive carcinomas of the breast
Cancer Letters 142 (1999) 121±127
Mucin expression in mucinous carcinoma and other invasive carcinomas of the breast Jan-Show Chu a,*, King-Jen Chang b a b
Department of Pathology, Taipei Medical College, 250 Wu-Hsing Street, Taipei, Taiwan Department of Surgery, College of Medicine, National Taiwan University, Taipei, Taiwan
Received 18 December 1998; received in revised form 29 March 1999; accepted 6 April 1999
Abstract To investigate mucin expression in breast cancer, immunohistochemical staining was performed on 30 mucinous carcinomas and 95 non-mucinous invasive carcinomas. MUC2 expression was detected in all mucinous carcinomas, but only in 11.1% of invasive ductal carcinomas, and in none of the invasive lobular carcinomas and medullary carcinomas. MUC1 is often expressed in invasive breast carcinoma, but not in medullary carcinoma. Strong cytoplasmic staining was seen in invasive ductal carcinoma, in contrast to surface membrane staining in mucinous carcinoma and intracytoplasmic vacuole staining in invasive lobular carcinoma. CA19-9 and CA50 expression in more than 25% of tumor cells was seen in 17.2 and 16.0% of invasive ductal carcinomas, respectively, but not in mucinous carcinomas. CA125 and human gastric mucin were rarely expressed in breast cancer, irrespective of histologic type. q 1999 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Breast cancer; Mucin; MUC1; MUC2; Mucinous carcinoma
1. Introduction Mucins are a family of heavily glycosylated, high molecular weight glycoproteins [1]. In humans, nine epithelial mucin genes (MUC 1, 2, 3, 4, 5A/C, 5B, 6, 7, 8) have been cloned [2]. All epithelial mucins produced by these genes contain a variable number of tandem repeats (VNTR) in the core protein. Mucin genes are independently regulated and their expression is organ and cell-type speci®c [3]. Mucins contain many different carbohydrate chains. These variations can occur due to incomplete or blocked synthesis or to neosynthesis. Increased synthesis, secretion, and alterations in glycosylation of mucin * Corresponding author. Tel.: 1 886-2-27361661, ext. 643; fax: 1 886-2-23770054. E-mail address: [email protected] (J.S. Chu)
are believed to play important roles in tumor cells [4,5]. The alterations in glycosylation lead to the appearance of novel structures, such as the epitopes recognized by monoclonal antibody CA50 (CA 50 epitope) and CA19-9 (sialyl Lewis a). MUC1 is an integral part of the cell membrane in normal breast epithelium, and increased MUC1 expression is usually observed in breast cancer [6± 11]. MUC2, a secretory glycoprotein, is present in the small intestine and colon epithelia. Little or no expression of MUC2 is detected in epithelia outside the gastrointestinal tract. Overexpression of MUC2 was often found in colorectal cancer [12,13] and gastric cancer [14], especially in the histologic type, mucinous carcinoma. MUC2 was not often detected in the usual ductal type of breast cancer [15]. The CA125 antigen is a glycoprotein present in most cases of ovarian carcinoma [16]. The gene codes for human
0304-3835/99/$ - see front matter q 1999 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0304-383 5(99)00161-5
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J.-S. Chu, K.-J. Chang / Cancer Letters 142 (1999) 121±127
Table 1 Clinicopathologic characteristics in patients with breast carcinoma Characteristics No. of cases Age (years) Tumor size (cm) ,2 cm 2±5 cm .5 cm Axillary node status Positive Negative Estrogen receptor Positive Negative p53 overexpression Positive Negative p27 expression Low (,30%) High ($30%) a b
Mucinous carcinoma 30 49.9
Invasive ductal carcinoma 81 49.2
7 (24.1%) 18 (62.1%) 4 (13.8%)
7 (8.6%) 52 (63.4%) 23 (28.1%)
7 (25%) 21 (75%)
41 (50.6%) 40 (49.4%)
27 (90%) 3 (10%)
34 (42.0%) 47 (58.0%)
1 (3.3%) 29 (96.7%)
27 (33.3%) 54 (66.7%)
11 (52.4%) a 10 (47.6%) a
51 (77.3%) b 15 (22.7%) b
In total 21 cases were examined. In total 66 cases were examined
gastric mucin (MUC6) are highly expressed in the stomach and gallbladder [17]. Breast cancer is a heterogeneous disease regarding morphology, invasive behavior, metastatic capacity, hormone receptor expression and clinical outcome. Mucinous carcinoma is a speci®c histologic type of breast cancer characterized by abundant extracellular mucin. The reported frequency of mucinous carcinoma of the breast is about 1±6% [18,19]. It is generally thought that the tumor occurs in elderly women and has a better prognosis than the usual ductal type of breast cancer [20,21]. For evaluating the mucin expression between mucinous and non-mucinous invasive breast cancer, we performed immunohistochemical staining using a panel of monoclonal antibodies and the result showed that mucinous carcinoma has a distinct pattern of mucin expression from other invasive breast carcinomas. 2. Materials and methods Data on patients who had primary mucinous carci-
noma of the breast were found in the records of the Department of Pathology at the National Taiwan University Hospital from 1978 to 1995. The tumors were histologically veri®ed as mucinous carcinomas when nearly all the tumor cells were ¯oating in abundant extracellular mucin. In total, there were 30 mucinous carcinomas. Ninety-®ve non-mucinous carcinomas (81 invasive ductal carcinomas, 6 invasive lobular carcinomas and 8 medullary carcinomas) were chosen randomly for comparison. Invasive ductal carcinoma was graded using the Scarff± Bloom±Richardson system [22]. For immunohistochemical analysis, 4-mm thick paraf®n sections were stained using the streptavidin± biotin±peroxidase complex method. Sections were incubated with monoclonal antibodies against MUC1, MUC-2, CA19-9, CA50, CA125 and HGL-45M1 (Novocastra Laboratories Ltd., UK). As negative controls, sections were stained as above but with PBS substituted for the primary antibody. The immunoreactivity was semi-quantitatively assessed by the percentage of positive tumor cells (0, 1±10, 11±25, 26±50, 51±75 and .75%). The predominant staining pattern was recorded as cytoplasmic, surface membrane, or intracytoplasmic vacuole. Evaluations of estrogen receptor (ER), progesterone receptor (PR) and p53 proteins were performed on paraf®n sections as described previously [23]. Immunohistochemical staining of p27 was performed on paraf®n-embedded sections using monoclonal anti-p27 (Transduction Laboratories, Lexington, KY). The percentage of tumor cells expressing p27 was recorded as the ratio of positive cells to the total 300 nuclei counted. p27 expression was classi®ed as being high ($30%) and low (,30%). Associations between mucin expression and other tumor characteristics were calculated using Chisquare or Fisher's exact tests. A two-tailed P , 0:05 was declared as statistically signi®cant. All calculations were performed using the SPSS statistical program (SPSS Inc. Chicago, IL) on a personal computer. 3. Results The clinicopathologic characteristics of 30 mucinous carcinomas and 81 invasive ductal carcinomas
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123
Table 2 Expression of MUC1, MUC2, CA19-9 and CA50 in (A) 30 mucinous carcinomas and (B) in 81 invasive ductal carcinomas of the breast % of Positive cells Mucinous carcinoma Negative ,10% 10±25% 26±50% 51±75% .75% Invasive ductal carcinoma Negative ,10% 10±25% 26±50% 51±75% .75%
MUC1 (%)
MUC2 (%)
CA19-9 (%)
CA50 (%)
1 (3.3) 3 (10) 5 (16.7) 4 (13.3) 12 (40) 5 (16.6)
0 3 (10) 8 (26.7) 6 (20) 11 (36.7) 2 (6.6)
26 (86.7) 2 (6.7) 2 (6.7) 0 0 0
27 (90) 3 (10) 0 0 0 0
7 (8.6) 9 (11.1) 9 (11.1) 5 (6.2) 19 (23.5) 32 (39.5)
72 (88.9) 7 (8.6) 2 (2.5) 0 0 0
50 (61.7) 13 (16.1) 4 (4.9) 1 (1.2) 3 (3.7) 10 (12.3)
51 (63.0) 15 (18.5) 2 (2.5) 2 (2.5) 4 (4.9) 7 (8.6)
of the breast are listed in Table 1. Mucinous carcinoma had a higher frequency of positive ER, high p27 expression and a lower frequency of axillary node metastasis and p53 overexpression than invasive ductal carcinoma. In normal breast tissue, MUC1, CA19-9 and CA50 expression occurred in the apical cell membrane of
epithelial cells, but MUC2, CA125 and human gastric mucin did not. The expression of mucin varied greatly in breast cancer (Table 2). Most invasive ductal carcinomas (Fig. 1) and mucinous carcinomas displayed MUC1 expression, but the staining pattern was different. MUC1 expression was predominantly seen in the surface membrane of tumor cells in mucinous
Fig. 1. Immunohistochemical staining of MUC1 expression revealed strong cytoplasmic staining in invasive ductal carcinoma (200 £ ).
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J.-S. Chu, K.-J. Chang / Cancer Letters 142 (1999) 121±127
Table 3 Associations between MUC1 expression and tumor characteristics Characteristics
Tumor size (cm) ,2.0 cm 2±5 cm .5.0 cm Histologic grade Grade I Grade II Grade III Axillary node status Positive Negative Lymphatic invasion Positive Negative Estrogen receptor Positive Negative Progesterone receptor Positive Negative p53 overexpression Positive Negative
No. of cases
.75% MUC1 expression (% of cases)
P value
7 52 22
3 (42.9) 24 (46.2) 5 (22.7)
.0.1
13 45 23
11 (84.6) 18 (40.0) 3 (13.0)
,0.0001
41 40
20 (48.8) 12 (30.0)
0.083
20 61
9 (45.0) 23 (37.7)
.0.1
34 47
20 (58.8) 12 (25.5)
0.0024
36 45
20 (55.6) 12 (26.7)
0.0082
27 54
6 (22.2) 26 (48.1)
0.024
carcinoma, in contrast to strong cytoplasmic expression in invasive ductal carcinoma. With MUC1 expression in over 50% of the tumor cells, 8 of 12 well-differentiated invasive ductal carcinomas had a strong surface membrane staining pattern compared with 14 of 39 in moderate and poorly differentiated ones. MUC1 expression occurred in 4 of 6 invasive lobular carcinomas, two of them expressed MUC1 in more than 50% of the tumor cells and the predominant pattern was as intracytoplasmic vacuoles. MUC1 did not often express in medullary carcinomas. In 4 medullary carcinomas with MUC1 expression, 3 of them expressed MUC1 in less than 25% of the tumor cells with a predominantly cytoplasmic pattern. Associations between MUC1 expression and other tumor characteristics in 81 invasive ductal carcinomas are listed in Table 3. Tumors with MUC1 expression in greater than 75% of tumor cells signi®cantly correlated with low histologic tumor grade (P , 0:0001), positive ER (P , 0:003), positive PR (P , 0:009), and absence of p53 protein overexpression (P ,
0.03). No signi®cant association was found between MUC1 expression and tumor size, axillary node metastases, or lymphatic invasion. MUC2 expression was detected in all 30 mucinous carcinomas (Fig. 2) and only in 9 of 81 (11.1%) invasive ductal carcinomas (Table 2). All the positive cases exhibited a cytoplasmic staining. Furthermore, the percentage of positively stained tumor cells in invasive ductal carcinoma was usually limited. None of the invasive lobular carcinomas and medullary carcinomas displayed MUC2 expression. CA19-9 and CA50 expression in greater than 25% of tumor cells was seen in 17.2% and 16.0% of invasive ductal carcinoma, respectively, but not in mucinous carcinoma. The expressions of CA19-9 and CA50 were not associated with any tumor characteristics of invasive ductal carcinoma (data not shown). CA125 and human gastric mucin were rarely expressed in a limited number of tumor cells. 4. Discussion We found a very high frequency of strong MUC2 expression in mucinous carcinoma compared with other histologic types of invasive breast carcinoma. Strong expression of MUC2 was observed in 72% of the mucinous but only in 21% of non-mucinous colonic carcinoma [12]. The MUC2 expression occurs in the premalignant stage and remains a characteristic property of the mucinous phenotype of colon tumors. The mechanisms of MUC2 overexpression in mucinous carcinomas are not known. Triggering the signal transduction pathway can induce the overexpression of MUC2 in colon adenocarcinoma cells in an in vitro study [24]. MUC2, mRNA and protein levels were signi®cantly higher in a cell line derived from colorectal mucinous carcinoma compared with a cell line derived from a moderately differentiated colorectal adenocarcinoma [25]. In addition, biologic studies showed that mucinous carcinoma cells have a greater degree of invasiveness, but less liver colonizing activity [25]. The ®ndings suggests that mucinous carcinoma cells progress by local invasion rather than distal metastasis. This may explain the low frequency of axillary node metastasis found in mucinous carcinoma. A hypothesis regarding the mucinous pathway of
J.-S. Chu, K.-J. Chang / Cancer Letters 142 (1999) 121±127
125
Fig. 2. Immunohistochemical staining of MUC2 expression revealed strong cytoplasmic staining in mucinous carcinoma (200 £ ).
carcinogenesis has been proposed [26]. All mucinous carcinomas in different organs (colon, breast, ovary and pancreas) have similar morphology and genetic alterations. In these tumors, the frequency of p53 overexpression is lower and the frequency of Ki-ras mutations is higher than in the corresponding nonmucinous tumors of the same organs. In addition, overexpression or ectopic expression of MUC2 has been described as the common property of mucinous carcinomas in different organs [27]. We also found that mucinous carcinomas of the breast had a high frequency of positive ER, negative p53 protein overexpression and high p27 expression. All the phenotypes of mucinous carcinomas favor a better clinical outcome. MUC1 expression is clearly increased in most breast carcinomas. Because of loss of polarization in the tumor cells, MUC1 is also found in the basolateral plasma membrane or in the cytoplasm. The overexpression of MUC1 leads to a decrease in cell-to-cell and cell-to-matrix contacts, causing inhibition of cancer cell killing by cytotoxic T lymphocytes. Furthermore, MUC1 expression might play a role in metastasis by inhibiting adhesion of the tumor cells and in escaping from the immune surveillance. We
found that MUC1 expression of invasive ductal carcinoma correlated signi®cantly with tumor grade and the proportion of cells showing surface membrane staining was higher in well-differentiated tumors. The staining pattern of MUC1 expression in welldifferentiated invasive ductal carcinomas is similar to that seen in normal breast epithelium and mucinous carcinomas. The correlation of MUC1 expression with histologic grade has been reported in several studies [6,8,10]. Because of the high grade morphology of tumor cells, medullary carcinoma rarely expressed MUC1 strongly. The intracytoplasmic vacuole staining pattern of MUC1 in invasive lobular carcinoma represents the intracytoplasmic lumen often present in the tumor cells demonstrated by mucicarmine staining or electron microscopy [28,29]. We also found that MUC1 expression correlated with ER/PR expression, and p53 overexpression. Well-differentiated invasive ductal carcinoma is associated with positive ER/PR, and the absence of p53 overexpression. The associations between MUC1 and ER/PR and p53 expression may be linked to tumor differentiation. Immunoreactivity for CA19-9 is present in a variety of adenocarcinomas and transitional cell carci-
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nomas [30]. It has been shown that CA19-9 was detected in 6±38% of breast cancers [30±32]. CA50 antigen, initially characterized in colon tumors, has been subsequently demonstrated in several human cancers, including breast cancer. CA19-9 and CA50 expression of breast cancer was not related to other clinicopathological characteristics, as shown previously [33]. The biological signi®cance of CA19-9 and CA50 remain to be clari®ed. CA125 is a glycoprotein present in ovarian cancer and some adenocarcinomas from many other sites [6]. Immunoreactivity for CA125 was seen in 13±24% of breast cancers in a limited number of cases examined [20,32]. Our results showed that CA125 and human gastric mucin were rarely expressed in different histologic types of breast cancer. Neither of them seemed to possess signi®cant roles in the development of breast cancer. However, it may be helpful in excluding breast cancer as the primary site when a metastatic adenocarcinoma, displaying CA125 and human gastric mucin expression, occurs.
[10]
Acknowledgements
[13]
This study was supported by the National Science Council, Taiwan. (grant no. 87-2314-B-002-320).
[14]
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Mucin expression in mucinous carcinoma and other invasive carcinomas of the breast Jan-Show Chu a,*, King-Jen Chang b a b
Department of Pathology, Taipei Medical College, 250 Wu-Hsing Street, Taipei, Taiwan Department of Surgery, College of Medicine, National Taiwan University, Taipei, Taiwan
Received 18 December 1998; received in revised form 29 March 1999; accepted 6 April 1999
Abstract To investigate mucin expression in breast cancer, immunohistochemical staining was performed on 30 mucinous carcinomas and 95 non-mucinous invasive carcinomas. MUC2 expression was detected in all mucinous carcinomas, but only in 11.1% of invasive ductal carcinomas, and in none of the invasive lobular carcinomas and medullary carcinomas. MUC1 is often expressed in invasive breast carcinoma, but not in medullary carcinoma. Strong cytoplasmic staining was seen in invasive ductal carcinoma, in contrast to surface membrane staining in mucinous carcinoma and intracytoplasmic vacuole staining in invasive lobular carcinoma. CA19-9 and CA50 expression in more than 25% of tumor cells was seen in 17.2 and 16.0% of invasive ductal carcinomas, respectively, but not in mucinous carcinomas. CA125 and human gastric mucin were rarely expressed in breast cancer, irrespective of histologic type. q 1999 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Breast cancer; Mucin; MUC1; MUC2; Mucinous carcinoma
1. Introduction Mucins are a family of heavily glycosylated, high molecular weight glycoproteins [1]. In humans, nine epithelial mucin genes (MUC 1, 2, 3, 4, 5A/C, 5B, 6, 7, 8) have been cloned [2]. All epithelial mucins produced by these genes contain a variable number of tandem repeats (VNTR) in the core protein. Mucin genes are independently regulated and their expression is organ and cell-type speci®c [3]. Mucins contain many different carbohydrate chains. These variations can occur due to incomplete or blocked synthesis or to neosynthesis. Increased synthesis, secretion, and alterations in glycosylation of mucin * Corresponding author. Tel.: 1 886-2-27361661, ext. 643; fax: 1 886-2-23770054. E-mail address: [email protected] (J.S. Chu)
are believed to play important roles in tumor cells [4,5]. The alterations in glycosylation lead to the appearance of novel structures, such as the epitopes recognized by monoclonal antibody CA50 (CA 50 epitope) and CA19-9 (sialyl Lewis a). MUC1 is an integral part of the cell membrane in normal breast epithelium, and increased MUC1 expression is usually observed in breast cancer [6± 11]. MUC2, a secretory glycoprotein, is present in the small intestine and colon epithelia. Little or no expression of MUC2 is detected in epithelia outside the gastrointestinal tract. Overexpression of MUC2 was often found in colorectal cancer [12,13] and gastric cancer [14], especially in the histologic type, mucinous carcinoma. MUC2 was not often detected in the usual ductal type of breast cancer [15]. The CA125 antigen is a glycoprotein present in most cases of ovarian carcinoma [16]. The gene codes for human
0304-3835/99/$ - see front matter q 1999 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0304-383 5(99)00161-5
122
J.-S. Chu, K.-J. Chang / Cancer Letters 142 (1999) 121±127
Table 1 Clinicopathologic characteristics in patients with breast carcinoma Characteristics No. of cases Age (years) Tumor size (cm) ,2 cm 2±5 cm .5 cm Axillary node status Positive Negative Estrogen receptor Positive Negative p53 overexpression Positive Negative p27 expression Low (,30%) High ($30%) a b
Mucinous carcinoma 30 49.9
Invasive ductal carcinoma 81 49.2
7 (24.1%) 18 (62.1%) 4 (13.8%)
7 (8.6%) 52 (63.4%) 23 (28.1%)
7 (25%) 21 (75%)
41 (50.6%) 40 (49.4%)
27 (90%) 3 (10%)
34 (42.0%) 47 (58.0%)
1 (3.3%) 29 (96.7%)
27 (33.3%) 54 (66.7%)
11 (52.4%) a 10 (47.6%) a
51 (77.3%) b 15 (22.7%) b
In total 21 cases were examined. In total 66 cases were examined
gastric mucin (MUC6) are highly expressed in the stomach and gallbladder [17]. Breast cancer is a heterogeneous disease regarding morphology, invasive behavior, metastatic capacity, hormone receptor expression and clinical outcome. Mucinous carcinoma is a speci®c histologic type of breast cancer characterized by abundant extracellular mucin. The reported frequency of mucinous carcinoma of the breast is about 1±6% [18,19]. It is generally thought that the tumor occurs in elderly women and has a better prognosis than the usual ductal type of breast cancer [20,21]. For evaluating the mucin expression between mucinous and non-mucinous invasive breast cancer, we performed immunohistochemical staining using a panel of monoclonal antibodies and the result showed that mucinous carcinoma has a distinct pattern of mucin expression from other invasive breast carcinomas. 2. Materials and methods Data on patients who had primary mucinous carci-
noma of the breast were found in the records of the Department of Pathology at the National Taiwan University Hospital from 1978 to 1995. The tumors were histologically veri®ed as mucinous carcinomas when nearly all the tumor cells were ¯oating in abundant extracellular mucin. In total, there were 30 mucinous carcinomas. Ninety-®ve non-mucinous carcinomas (81 invasive ductal carcinomas, 6 invasive lobular carcinomas and 8 medullary carcinomas) were chosen randomly for comparison. Invasive ductal carcinoma was graded using the Scarff± Bloom±Richardson system [22]. For immunohistochemical analysis, 4-mm thick paraf®n sections were stained using the streptavidin± biotin±peroxidase complex method. Sections were incubated with monoclonal antibodies against MUC1, MUC-2, CA19-9, CA50, CA125 and HGL-45M1 (Novocastra Laboratories Ltd., UK). As negative controls, sections were stained as above but with PBS substituted for the primary antibody. The immunoreactivity was semi-quantitatively assessed by the percentage of positive tumor cells (0, 1±10, 11±25, 26±50, 51±75 and .75%). The predominant staining pattern was recorded as cytoplasmic, surface membrane, or intracytoplasmic vacuole. Evaluations of estrogen receptor (ER), progesterone receptor (PR) and p53 proteins were performed on paraf®n sections as described previously [23]. Immunohistochemical staining of p27 was performed on paraf®n-embedded sections using monoclonal anti-p27 (Transduction Laboratories, Lexington, KY). The percentage of tumor cells expressing p27 was recorded as the ratio of positive cells to the total 300 nuclei counted. p27 expression was classi®ed as being high ($30%) and low (,30%). Associations between mucin expression and other tumor characteristics were calculated using Chisquare or Fisher's exact tests. A two-tailed P , 0:05 was declared as statistically signi®cant. All calculations were performed using the SPSS statistical program (SPSS Inc. Chicago, IL) on a personal computer. 3. Results The clinicopathologic characteristics of 30 mucinous carcinomas and 81 invasive ductal carcinomas
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Table 2 Expression of MUC1, MUC2, CA19-9 and CA50 in (A) 30 mucinous carcinomas and (B) in 81 invasive ductal carcinomas of the breast % of Positive cells Mucinous carcinoma Negative ,10% 10±25% 26±50% 51±75% .75% Invasive ductal carcinoma Negative ,10% 10±25% 26±50% 51±75% .75%
MUC1 (%)
MUC2 (%)
CA19-9 (%)
CA50 (%)
1 (3.3) 3 (10) 5 (16.7) 4 (13.3) 12 (40) 5 (16.6)
0 3 (10) 8 (26.7) 6 (20) 11 (36.7) 2 (6.6)
26 (86.7) 2 (6.7) 2 (6.7) 0 0 0
27 (90) 3 (10) 0 0 0 0
7 (8.6) 9 (11.1) 9 (11.1) 5 (6.2) 19 (23.5) 32 (39.5)
72 (88.9) 7 (8.6) 2 (2.5) 0 0 0
50 (61.7) 13 (16.1) 4 (4.9) 1 (1.2) 3 (3.7) 10 (12.3)
51 (63.0) 15 (18.5) 2 (2.5) 2 (2.5) 4 (4.9) 7 (8.6)
of the breast are listed in Table 1. Mucinous carcinoma had a higher frequency of positive ER, high p27 expression and a lower frequency of axillary node metastasis and p53 overexpression than invasive ductal carcinoma. In normal breast tissue, MUC1, CA19-9 and CA50 expression occurred in the apical cell membrane of
epithelial cells, but MUC2, CA125 and human gastric mucin did not. The expression of mucin varied greatly in breast cancer (Table 2). Most invasive ductal carcinomas (Fig. 1) and mucinous carcinomas displayed MUC1 expression, but the staining pattern was different. MUC1 expression was predominantly seen in the surface membrane of tumor cells in mucinous
Fig. 1. Immunohistochemical staining of MUC1 expression revealed strong cytoplasmic staining in invasive ductal carcinoma (200 £ ).
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Table 3 Associations between MUC1 expression and tumor characteristics Characteristics
Tumor size (cm) ,2.0 cm 2±5 cm .5.0 cm Histologic grade Grade I Grade II Grade III Axillary node status Positive Negative Lymphatic invasion Positive Negative Estrogen receptor Positive Negative Progesterone receptor Positive Negative p53 overexpression Positive Negative
No. of cases
.75% MUC1 expression (% of cases)
P value
7 52 22
3 (42.9) 24 (46.2) 5 (22.7)
.0.1
13 45 23
11 (84.6) 18 (40.0) 3 (13.0)
,0.0001
41 40
20 (48.8) 12 (30.0)
0.083
20 61
9 (45.0) 23 (37.7)
.0.1
34 47
20 (58.8) 12 (25.5)
0.0024
36 45
20 (55.6) 12 (26.7)
0.0082
27 54
6 (22.2) 26 (48.1)
0.024
carcinoma, in contrast to strong cytoplasmic expression in invasive ductal carcinoma. With MUC1 expression in over 50% of the tumor cells, 8 of 12 well-differentiated invasive ductal carcinomas had a strong surface membrane staining pattern compared with 14 of 39 in moderate and poorly differentiated ones. MUC1 expression occurred in 4 of 6 invasive lobular carcinomas, two of them expressed MUC1 in more than 50% of the tumor cells and the predominant pattern was as intracytoplasmic vacuoles. MUC1 did not often express in medullary carcinomas. In 4 medullary carcinomas with MUC1 expression, 3 of them expressed MUC1 in less than 25% of the tumor cells with a predominantly cytoplasmic pattern. Associations between MUC1 expression and other tumor characteristics in 81 invasive ductal carcinomas are listed in Table 3. Tumors with MUC1 expression in greater than 75% of tumor cells signi®cantly correlated with low histologic tumor grade (P , 0:0001), positive ER (P , 0:003), positive PR (P , 0:009), and absence of p53 protein overexpression (P ,
0.03). No signi®cant association was found between MUC1 expression and tumor size, axillary node metastases, or lymphatic invasion. MUC2 expression was detected in all 30 mucinous carcinomas (Fig. 2) and only in 9 of 81 (11.1%) invasive ductal carcinomas (Table 2). All the positive cases exhibited a cytoplasmic staining. Furthermore, the percentage of positively stained tumor cells in invasive ductal carcinoma was usually limited. None of the invasive lobular carcinomas and medullary carcinomas displayed MUC2 expression. CA19-9 and CA50 expression in greater than 25% of tumor cells was seen in 17.2% and 16.0% of invasive ductal carcinoma, respectively, but not in mucinous carcinoma. The expressions of CA19-9 and CA50 were not associated with any tumor characteristics of invasive ductal carcinoma (data not shown). CA125 and human gastric mucin were rarely expressed in a limited number of tumor cells. 4. Discussion We found a very high frequency of strong MUC2 expression in mucinous carcinoma compared with other histologic types of invasive breast carcinoma. Strong expression of MUC2 was observed in 72% of the mucinous but only in 21% of non-mucinous colonic carcinoma [12]. The MUC2 expression occurs in the premalignant stage and remains a characteristic property of the mucinous phenotype of colon tumors. The mechanisms of MUC2 overexpression in mucinous carcinomas are not known. Triggering the signal transduction pathway can induce the overexpression of MUC2 in colon adenocarcinoma cells in an in vitro study [24]. MUC2, mRNA and protein levels were signi®cantly higher in a cell line derived from colorectal mucinous carcinoma compared with a cell line derived from a moderately differentiated colorectal adenocarcinoma [25]. In addition, biologic studies showed that mucinous carcinoma cells have a greater degree of invasiveness, but less liver colonizing activity [25]. The ®ndings suggests that mucinous carcinoma cells progress by local invasion rather than distal metastasis. This may explain the low frequency of axillary node metastasis found in mucinous carcinoma. A hypothesis regarding the mucinous pathway of
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Fig. 2. Immunohistochemical staining of MUC2 expression revealed strong cytoplasmic staining in mucinous carcinoma (200 £ ).
carcinogenesis has been proposed [26]. All mucinous carcinomas in different organs (colon, breast, ovary and pancreas) have similar morphology and genetic alterations. In these tumors, the frequency of p53 overexpression is lower and the frequency of Ki-ras mutations is higher than in the corresponding nonmucinous tumors of the same organs. In addition, overexpression or ectopic expression of MUC2 has been described as the common property of mucinous carcinomas in different organs [27]. We also found that mucinous carcinomas of the breast had a high frequency of positive ER, negative p53 protein overexpression and high p27 expression. All the phenotypes of mucinous carcinomas favor a better clinical outcome. MUC1 expression is clearly increased in most breast carcinomas. Because of loss of polarization in the tumor cells, MUC1 is also found in the basolateral plasma membrane or in the cytoplasm. The overexpression of MUC1 leads to a decrease in cell-to-cell and cell-to-matrix contacts, causing inhibition of cancer cell killing by cytotoxic T lymphocytes. Furthermore, MUC1 expression might play a role in metastasis by inhibiting adhesion of the tumor cells and in escaping from the immune surveillance. We
found that MUC1 expression of invasive ductal carcinoma correlated signi®cantly with tumor grade and the proportion of cells showing surface membrane staining was higher in well-differentiated tumors. The staining pattern of MUC1 expression in welldifferentiated invasive ductal carcinomas is similar to that seen in normal breast epithelium and mucinous carcinomas. The correlation of MUC1 expression with histologic grade has been reported in several studies [6,8,10]. Because of the high grade morphology of tumor cells, medullary carcinoma rarely expressed MUC1 strongly. The intracytoplasmic vacuole staining pattern of MUC1 in invasive lobular carcinoma represents the intracytoplasmic lumen often present in the tumor cells demonstrated by mucicarmine staining or electron microscopy [28,29]. We also found that MUC1 expression correlated with ER/PR expression, and p53 overexpression. Well-differentiated invasive ductal carcinoma is associated with positive ER/PR, and the absence of p53 overexpression. The associations between MUC1 and ER/PR and p53 expression may be linked to tumor differentiation. Immunoreactivity for CA19-9 is present in a variety of adenocarcinomas and transitional cell carci-
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nomas [30]. It has been shown that CA19-9 was detected in 6±38% of breast cancers [30±32]. CA50 antigen, initially characterized in colon tumors, has been subsequently demonstrated in several human cancers, including breast cancer. CA19-9 and CA50 expression of breast cancer was not related to other clinicopathological characteristics, as shown previously [33]. The biological signi®cance of CA19-9 and CA50 remain to be clari®ed. CA125 is a glycoprotein present in ovarian cancer and some adenocarcinomas from many other sites [6]. Immunoreactivity for CA125 was seen in 13±24% of breast cancers in a limited number of cases examined [20,32]. Our results showed that CA125 and human gastric mucin were rarely expressed in different histologic types of breast cancer. Neither of them seemed to possess signi®cant roles in the development of breast cancer. However, it may be helpful in excluding breast cancer as the primary site when a metastatic adenocarcinoma, displaying CA125 and human gastric mucin expression, occurs.
[10]
Acknowledgements
[13]
This study was supported by the National Science Council, Taiwan. (grant no. 87-2314-B-002-320).
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