Mammaglobin a in breast cancer: existence of multiple molecular forms

Identification and characterization of mammaglobin-A epitope in heterogenous breast cancers for enhancing tumor-targeting therapy

Although targeted therapy has been extensively investigated for breast cancers, a molecular target with broad application is currently unavailable due to the high heterogeneity of these cancers. Mammaglobin-A (Mam-A), which is overexpressed in most breast carcinomas, has been proposed as a promising target. However, the lack of specific targeting moieties due to uncertain binding epitopes hampers further translational study. Here, seven potential epitopes of Mam-A were disclosed, and a unique epitope was then identified in most types of breast cancers, despite the genotypic heterogeneity. With phage display technology, the epitope was determined to be N-terminal amino acids 42–51 of Mam-A (N_42–51). Then, the N_42–51 epitope-specific monoclonal antibody, mAb785, was conjugated to poly lactic-co-glycolic acid (PLGA) nanoparticles loaded with therapeutic agents, thereby enhancing the drug uptake and therapeutic efficacy in different genotypes of breast cancers. The computer simulation of the N_42–51 epitope and the mAb785 structures, as well as their interactions, further revealed the specific targeting mechanism of the mAb785-conjugated nanoparticles to breast cancers.

Combined DOG1 and Mammaglobin Immunohistochemistry Is Comparable to ETV6-breakapart Analysis for Differentiating Between Papillary Cystic Variants of Acinic Cell Carcinoma and Mammary Analogue Secretory Carcinoma

BACKGROUND

We investigated the reliability of combined DOG1 and mammaglobin immunohistochemistry compared with ETV6 fluorescence in situ hybridization (FISH) in the assessment of salivary tumors previously diagnosed as acinic cell carcinoma (ACC). Ultrastructural features of cases reclassified as mammary analogue secretory carcinoma (MASC) were assessed by transmission electron microscopy (TEM).

METHODS

Immunohistochemical (IHC) reactivity to DOG1 and mammaglobin was validated against FISH targeting the ETV6 gene in all 14 cases.

RESULTS

Three cases with papillary cystic histomorphology previously diagnosed as ACC were revised to MASC. TEM features of the ETV6 rearrangement-positive MASC cases showed large numbers of secretory granules with extrusion into the intercellular spaces, well-developed endoplasmic reticulum, lipid-laden vacuoles, well-formed microvilli, and large lining cystic spaces.

CONCLUSIONS

Combined DOG1 and mammaglobin immunohistochemistry is comparable to ETV6 -breakapart analysis for differentiating between papillary cystic variants of ACC and MASC.

Mammaglobin 1 promotes breast cancer malignancy and confers sensitivity to anticancer drugs

Mammaglobin 1 (MGB1), a member of the secretoglobin family, is expressed in mammary epithelial tissues and is overexpressed in most mammary carcinomas. Despite the extensive research correlating MGB1 expression profiles to breast cancer pathogenesis and disease outcome, the biological significance of MGB1 in cancer processes is still unclear. We have thus set out to conduct a functional evaluation of the molecular and cellular roles of MGB1 in breast cancer processes leading to disease progression. Using a series of breast cancer cell models with conditional MGB1 expression, we demonstrate that MGB1 promotes cancer cell malignant features. More specifically, loss of MGB1 expression resulted in a decrease of cell proliferation, soft agar spheroid formation, migration, and invasion capacities of breast cancer cells. Concomitantly, we also observed that MGB1 expression activates signaling pathways mediated by MAPK members (p38, JNK, and ERK), the focal adhesion kinase (FAK), matrix metalloproteinases (MMPs) and NFκB. Moreover, MGB1 regulates epithelial to mesenchymal (EMT) features and modulates Snail, Twist and ZEB1 expression levels. Interestingly, we also observed that expression of MGB1 confers breast cancer cell sensitivity to anticancer drug-induced apoptosis. Together, our results support a role for MGB1 in tumor malignancy in exchange for chemosensitivity. These findings provide one of the first descriptive overview of the molecular and cellular roles of MGB1 in breast cancer processes and may offer new insight to the development of therapeutic and prognostic strategies in breast cancer patients. © 2015 Wiley Periodicals, Inc.

ADAM-17 expression in breast cancer correlates with variables of tumor progression

The ADAMs are a family of membrane proteins possessing a disintegrin and metalloprotease domain. One of their main functions is shedding of membrane proteins. The aim of this study was to test the hypothesis that ADAM-17 (also known as tumor necrosis factor-alpha converting enzyme) is involved in breast cancer progression. Overexpression of ADAM-17 in MCF-7 breast cancer cells increased in vitro invasion and proliferation, whereas down-regulation of ADAM-17 expression in MDA-MB-435 cells decreased invasion and proliferation. At both mRNA and protein levels, ADAM-17 expression was significantly up-regulated in breast cancer compared with normal breast tissue. Using Western blotting, ADAM-17 protein in breast cancer was shown to exist in two forms migrating with approximate molecular masses of 100 and 120 kDa. Based on their known molecular mass, these bands were taken to represent the active and precursor forms of ADAM-17, respectively. The proportion of active to total ADAM-17 increased progressively from normal breast tissue to primary breast cancer to lymph node metastases (P = 0.017, Kruskal-Wallis test). In primary cancers, the active form was expressed more frequently in node-positive compared with node-negative tumors (P = 0.034, chi(2) test). Furthermore, in primary carcinomas, both forms of ADAM-17 correlated significantly (Spearman correlation analysis) with levels of urokinase plasminogen activator (precursor form: r = 0.246, P = 0.032, n = 83 and active form: r = 0.428, P = 0.0001, n = 83) and proliferating cell nuclear antigen (precursor form: r = 0.524, P < 0.0001, n = 73 and active form: r = 0.365, P = 0.002, n = 73). Our results support the hypothesis that ADAM-17 is involved in breast cancer progression.

Lipophilin B: A gene preferentially expressed in breast tissue and upregulated in breast cancer

Lipophilin B (LPB), which is also known as BU101, is a secretoglobin which exists in vivo as a complex with the mammary-specific protein, mammaglobin A (MGA). The aim of our study was to investigate the expression of LPB in a panel of breast and nonbreast tissues and compare its expression with that of MGA. Using RT-PCR, LPB mRNA was detected in 16/25 (64%) of normal breast specimens, 23/30 (77%) of fibroadenomas, 102/156 (65%) of primary breast cancers and in 8/36 (22%) nonbreast tissues. Levels of expression of LPB mRNA were significantly higher in breast cancers compared to both normal breast tissues (p = 0.02) and nonbreast tissue (p < 0.001). In the primary breast cancers, expression of LPB mRNA was positively correlated with the estrogen receptor (p = 0.045) but inversely related to both tumor grade (p < 0.001) and proliferation rates (p = 0.0345). Compared to MGA, expression of LPB was more sensitive but less specific for breast cancer. Using Western blotting, LPB migrated with an approximate molecular mass of 7-8 kDa, the expected molecular mass of free LPB. Immunohistochemical analysis of breast cancers showed that LPB expression was predominantly confined to the cytoplasm of tumor cells. We conclude that expression of LPB is preferentially but not exclusively restricted to breast tissue. Since LPB was expressed relatively specifically in breast tissue and was significantly upregulated in breast carcinomas, it is a promising candidate biomarker for breast cancer.

Expression analysis of mammaglobin A (SCGB2A2) and lipophilin B (SCGB1D2) in more than 300 human tumors and matching normal tissues reveals their co-expression in gynecologic malignancies

Background

Mammaglobin A (SCGB2A2) and lipophilin B (SCGB1D2), two members of the secretoglobin superfamily, are known to be co-expressed in breast cancer, where their proteins form a covalent complex. Based on the relatively high tissue-specific expression pattern, it has been proposed that the mammaglobin A protein and/or its complex with lipophilin B could be used in breast cancer diagnosis and treatment. In view of these clinical implications, the aim of the present study was to analyze the expression of both genes in a large panel of human solid tumors (n = 309), corresponding normal tissues (n = 309) and cell lines (n = 11), in order to evaluate their tissue specific expression and co-expression pattern.

Methods

For gene and protein expression analyses, northern blot, dot blot hybridization of matched tumor/normal arrays (cancer profiling arrays), quantitative RT-PCR, non-radioisotopic RNA in situ hybridization and immunohistochemistry were used.

Results

Cancer profiling array data demonstrated that mammaglobin A and lipophilin B expression is not restricted to normal and malignant breast tissue. Both genes were abundantly expressed in tumors of the female genital tract, i.e. endometrial, ovarian and cervical cancer. In these four tissues the expression pattern of mammaglobin A and lipophilin B was highly concordant, with both genes being down-, up- or not regulated in the same tissue samples. In breast tissue, mammaglobin A expression was down-regulated in 49% and up-regulated in 12% of breast tumor specimens compared with matching normal tissues, while lipophilin B was down-regulated in 59% and up-regulated in 3% of cases. In endometrial tissue, expression of mammaglobin A and lipophilin B was clearly up-regulated in tumors (47% and 49% respectively). Both genes exhibited down-regulation in 22% of endometrial tumors. The only exceptions to this concordance of mammaglobin A/lipophilin B expression were normal and malignant tissues of prostate and kidney, where only lipophilin B was abundantly expressed and mammaglobin A was entirely absent. RNA in situ hybridization and immunohistochemistry confirmed expression of mammaglobin A on a cellular level in endometrial and cervical cancer and their corresponding normal tissues.

Conclusion

Altogether, these data suggest that expression of mammaglobin A and lipophilin B might be controlled in different tissues by the same regulatory transcriptional mechanisms. Diagnostic assays based on mammaglobin A expression and/or the mammaglobin A/lipophilin B complex appear to be less specific for breast cancer, but with a broader spectrum of potential applications, which includes gynecologic malignancies.