Lisa M.J. Lee

The fate of human malignant melanoma cells transplanted into zebrafish embryos: assessment of migration and cell division in the absence of tumor formation.

Certain aggressive melanoma cell lines exhibit a dedifferentiated phenotype, expressing genes that are characteristic of various cell types including endothelial, neural, and stem cells. Moreover, we have shown that aggressive melanoma cells can participate in neovascularization in vivo and vasculogenic mimicry in vitro, demonstrating that these cells respond to microenvironmental cues and manifest developmental plasticity. To explore this plasticity further, we transplanted human metastatic melanoma cells into zebrafish blastula‐stage embryos and monitored their behavior post‐transplantation. The data show that human metastatic melanoma cells placed in the zebrafish embryo survive, exhibit motility, and divide. The melanoma cells do not form tumors nor integrate into host organs, but instead become scattered throughout the embryo in interstitial spaces, reflecting the dedifferentiated state of the cancer cells. In contrast to the fate of melanoma cells, human melanocytes transplanted into zebrafish embryos most frequently become distributed to their normal microenvironment of the skin, revealing that the zebrafish embryo contains possible homing cues that can be interpreted by normal human cells. Finally, we show that within the zebrafish embryo, metastatic melanoma cells retain their dedifferentiated phenotype. These results demonstrate the utility of the zebrafish embryonic model for the study of tumor cell plasticity and suggest that this experimental paradigm can be a powerful one in which to investigate tumor‐microenvironment interactions. Developmental Dynamics 233:1560–1570, 2005.

ER-α36, a novel isoform of ER-α66, is commonly over-expressed in apocrine and adenoid cystic carcinomas of the breast

Background ER-α36 is a novel 36 kDa isoform of the full-length oestrogen receptor alpha (ER-α66). ER-α36 primarily localises to the cytoplasm and the plasma membrane, and responds to membrane-initiated oestrogen and antioestrogen signalling pathways. Aim To examine the expression of ER-α36 in apocrine and adenoid cystic carcinoma of the breast, both of which are consistently ER-α66 negative and currently lack effective targeted therapeutic options. Methods 19 pure apocrine carcinomas (17 invasive and two in-situ carcinomas) and 11 adenoid cystic carcinomas of the breast were evaluated for ER-α36 expression, along with expressions of ER-α66, progesterone receptor (PR) and androgen receptor (AR) using immunohistochemical methods. Results All pure apocrine carcinomas showed a characteristic steroid receptor expression profile (ER-α66 and PR negative, AR strongly positive). ER-α36 expression was detected in 18/19 pure apocrine carcinomas (94.7%, 95% CI 75.1 to 98.7) in predominantly membranous and cytoplasmic distribution. When positive, pure apocrine carcinomas uniformly (100% of cells) expressed ER-α36. All adenoid cystic carcinomas were uniformly negative for all three classic steroid receptors, but ER-α36 was detected in 8/11 cases (72.7%, 95% CI 42.8 to 90) with the similar sub-cellular pattern of expression as in the pure apocrine carcinomas. When positive, adenoid cystic carcinomas expressed ER-α36 in the majority of cells (average 76%). Conclusion ER-α36, a novel isoform of ER-α66, is frequently over-expressed in apocrine and adenoid cystic carcinomas of the breast. These results indicate a potential for a novel targeted treatment in these cancers.

Adenoid cystic carcinomas of the breast have low Topo IIα expression but frequently overexpress EGFR protein without EGFR gene amplification

Adenoid cystic carcinoma of the breast is a rare subtype of breast cancer with basal-like features. Published studies on breast adenoid cystic carcinoma are limited, resulting in relatively scarce information on the value of predictive tumor markers. We studied 20 primary cases of adenoid cystic carcinoma of the breast for expression of estrogen receptor, progesterone receptor, androgen receptor, epidermal growth factor receptor, HER-2/neu, and topoisomerase IIα using immunohistochemistry and fluorescent in situ hybridization methods. Estrogen and progesterone receptor expression were detected in 1 case each. All tumors were uniformly negative for Her-2/neu expression. Androgen receptor and topoisomerase IIα expression were weakly positive in three cases and 7 cases, respectively. Epidermal growth factor receptor overexpression was detected in 13 cases (65% of all cases). Amplification of TOP2A or HER-2/neu gene was not detected in any of the cases. Our study shows that the majority of adenoid cystic carcinomas of the breast do not overexpress Her-2/neu, topoisomerase IIα, or estrogen receptor, and thus, they are unlikely to respond to therapies targeting these proteins. However, these tumors frequently over-express epidermal growth factor receptor, indicating a potential benefit from anti-epidermal growth factor receptor therapy for patients with advanced adenoid cystic carcinomas of the breast.

Pure apocrine carcinomas of the breast express ER-alpha 36, a novel alternatively spliced variant of human estrogen receptor-alpha (ER-alpha 66).

CTRC-AACR San Antonio Breast Cancer Symposium: 2008 Abstracts Abstract #4035 Background: Pure apocrine carcinomas (PACs) are defined as tumors composed entirely of epithelium showing apocrine differentiation (large cells with prominent eosinophilic, flocculent cytoplasm with sharply defined borders and large nucleus with prominent macronucleolus). PACs do not express classic estrogen receptor alpha (ER-α66) or progesterone receptor (PR) but consistently over-expresses androgen receptor (AR). We have investigated expression of a novel alternatively spliced variant of ER-α66, named ER-α36, which we recently identified and cloned (Wang ZY et al, PNAS 2006;103: 9063) and demonstrated that it mediates membrane initiated steroid signaling (MISS). MISS is dependent on ER interaction with receptor tyrosine kinases, and we hence investigated co-expression of ER-α36 with EGFR and HER2 in PACs. Methods: 17 patients with breast PAC were studied for expression of ER-α66, PR, AR, HER-2, EGFR and ER-α36 using immunohistochemical methods. ER-α36-specific antibody was custom-made by the Alpha Diagnostic International (San Antonio, TX) against the unique 20 amino acids at the C-terminal of the ER-a36; other antibodies were from commercially available sources. Mammary carcinoma cell line (MDA-MB-231) that lacks expression of ER-α66 but expresses ER-α36 and EGFR, was used as a positive control. Results: All tumors showed characteristic steroid receptor expression profile of apocrine carcinomas (ERα66 and PR negative; AR strongly positive). ERα36 expression was detected in 16/17 cases (94%) in membranous and cytoplasmic distribution. Co-expression of ER-α36 with either one of the tyrosine kinase receptors (HER2 or EGFR) was detected in 16 cases (100% of ER-α36 positive PACs). In an experimental model (MDA-MB-231 cells), 17β-estradiol (E2) strongly induced rapid phosphorylation of the MAPK/ERK1/2, but had only a weak effect in ER-α36 siRNA knock-down MDA-MB-231 cells. Conclusion: Despite the lack of classic full length ER-alpha expression (ER-α66) in PACs, a novel alternatively splice variant (ER-α36) is commonly expressed in this aggressive tumor type. This receptor variant is capable of strong E2 signal transduction and responsible for an increased cell growth. This non-genomic estrogen signaling probably involves membranous interaction between a tyrosine kinase receptor (EGFR or HER2) and ER-α36, resulting in activation of mitogen activated protein kinase pathway. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 4035.