Establishment of hormone-dependent and hormone-independent carcinoma cell lines with different metastatic potentials from spontaneous mammary tumors in aged Wistar rats

Rat Models of Hormone Receptor-Positive Breast Cancer

Hormone receptor-positive (HR+) breast cancer (BC) is the most common type of breast cancer among women worldwide, accounting for 70-80% of all invasive cases. Patients with HR+ BC are commonly treated with endocrine therapy, but intrinsic or acquired resistance is a frequent problem, making HR+ BC a focal point of intense research. Despite this, the malignancy still lacks adequate in vitro and in vivo models for the study of its initiation and progression as well as response and resistance to endocrine therapy. No mouse models that fully mimic the human disease are available, however rat mammary tumor models pose a promising alternative to overcome this limitation. Compared to mice, rats are more similar to humans in terms of mammary gland architecture, ductal origin of neoplastic lesions and hormone dependency status. Moreover, rats can develop spontaneous or induced mammary tumors that resemble human HR+ BC. To date, six different types of rat models of HR+ BC have been established. These include the spontaneous, carcinogen-induced, transplantation, hormone-induced, radiation-induced and genetically engineered rat mammary tumor models. Each model has distinct advantages, disadvantages and utility for studying HR+ BC. This review provides a comprehensive overview of all published models to date.

Establishment and characterization of a human colonic mucinous carcinoma cell line with predominant goblet-cell differentiation from liver metastasis

Many human colorectal adenocarcinoma cell lines have been developed. However, differentiated type colorectal cancer cell lines, particularly, the goblet-cell differentiated type, are scarce. In the present study a novel colorectal adenocarcinoma cell line (designated as COLM-6) with predominant goblet-cell differentiation was established from the rectal mucinous adenocarcinoma of a Japanese woman. COLM-6 cells grow in a typical epithelial monolayer in culture. They expressed epidermal growth factor (EGF) receptor and HER2 on their surface and accordingly, their growth was significantly stimulated by EGF, transforming growth factor (TGF)-alpha and heregulin. COLM-6 cells form tumor with typical mucinous adenocarcinomatous appearance in nude mice. Immunohistochemical analysis of these subcutaneous tumors demonstrated that COLM-6 cells strongly express MUC2 as a goblet-cell marker and Cdx2 in the nucleus. Some weakly express villin and carbonic anhydrase 1 as a columnar absorptive-cell marker as well. They were also positive for adenomatous polyposis coli (APC) cytoplasmically and expressed beta-catenin in their cytoplasm and cell membrane without nuclear accumulation. These results indicate that COLM-6 cell line has unique characteristics and may provide a useful tool to study the mechanism of growth and differentiation of colonic epithelium as well as the biological behavior of colorectal mucinous adenocarcinoma.

Establishment and characterization of three novel human gastric cancer cell lines with differentiated intestinal phenotype derived from liver metastasis

Gastric cancers with liver metastasis are fatal diseases with rapid progression and poor patient outcome. To date, however, the molecular basis of their growth and metastasis remains essentially unknown, largely because of the presence of few available gastric cancer cell lines established from liver metastasis. In the present study, we developed two novel cultured cell lines (designated GLM-1 and GLM-2) and one transplantable line in nude mice (designated GLM-3) derived from liver metastasis of gastric cancer patients. These GLM cell lines share unique biological features such as differentiation, growth and metastasis. They form moderately differentiated tumors with CD10 positive and MUC2 negative intestinal absorptive phenotype when injected into nude mice. Their growth is stimulated by EGF and TGF-alpha in vitro like other gastric cancer cell lines. However, GLM cells differ from conventional gastric cancer cell lines in their high apoptotic rate, even in the absence of apoptosis inducing stimuli as revealed by Caspase3/7 assay and the TUNEL method. This apoptosis is further enhanced by phosphatidylinositol 3-kinase (PI3K) inhibitor (LY294002), but not by MEK1/2 inhibitor (U0126), indicating the strong dependency of their survival on PI3K/Akt pathway rather than MAPK pathway, the major downstream signaling pathways of EGFR. GLM-1 cells can metastasize to the liver after intrasplenic injection, and GLM-3 cells have spontaneous lung metastatic potential after subcutaneous transplantation, respectively. These results indicate that the GLM series are the first cell lines reflecting the intestinal-type differentiated adenocarcinoma, a major subtype of gastric cancer with liver metastasis. Therefore, they would be excellent models for understanding the mechanism of metastatic growth and the development of a new molecular targeting therapy for gastric cancer with liver metastasis.

Regulation of urokinase plasminogen activator (uPA) activity by E-cadherin and hormones in mammary epithelial cells

Urokinase plasminogen activator (uPA) is involved in proteolysis of extracellular matrix during development and tumor cell invasion. In the present study, we examined the regulation of uPA in hormone-responsive, noninvasive mammary epithelial cells by using fibrinolytic and caseinolytic enzyme activity assays. Urokinase PA expression was activated after contact with fibrin and initiation of cell-cell interactions that were mediated by E-cadherin. Fibrinolysis occurred in zones surrounding cellular aggregates. Stromal matrix proteins that disrupted aggregation or anti-E-cadherin antibodies that inhibited cellular compaction inhibited fibrinolysis perhaps by increasing cell-matrix adhesion or preventing E-cadherin signaling, respectively. Aggregation required the presence of divalent cations and was inhibited by serum and ethylene diaminetetraacetic acid, whereas serine protease inhibitors reduced uPA activity without affecting aggregation. Inhibitors of PA (type 2; PAI-2) and a specific antisense uPA oligonucleotide also reduced enzymatic activity, suggesting that fibrinolysis depends on translational regulation of uPA. In addition, the activation of plasmin from plasminogen was inhibited by anti-E-cadherin antibodies and PAI-2, consistent with a role for uPA. The data also support a role for transcriptional regulation of uPA activity because treatment of cells with progesterone, hydrocortisone, or dexamethasone inhibited uPA activation on fibrin without affecting cellular aggregation. Estradiol and insulin did not alter, whereas human chorionic gonadotropin and prolactin increased uPA activity. The expression of the 55-kDa uPA activity was consistent with specific hormone action and correlated with protein expression by immunoblotting. Therefore, the alteration of downstream signaling events by hormones may affect uPA production. These results indicate that uPA is an enzyme that may be important in the degradation of extracellular matrix during development and that specific E-cadherin interactions and hormones can regulate its activity. Investigation of the regulation of uPA in these cells may be useful in understanding and manipulating mammary gland remodeling. J. Cell. Physiol. 181:1-13, 1999. Published 1999 Wiley-Liss, Inc.

Hypomethylation of an exon I estrogen receptor CpG island in spontaneous and carcinogen-induced mammary tumorigenesis in the rat

Loss of methylation at a CpG island in exon I of the rat ER gene was observed in 48% of the spontaneous mammary tumors in old female Wistar rats and 22% of the contralateral normal mammary tissues. The majority of the methylation losses were total. Similarly, 50% of 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumors in young Sprague-Dawley rats exhibited a partial or total loss of methylation at this site, while all normal mammary tissues in young rats were fully methylated. Loss of ER methylation also increased with age in normal mammary tissues of tumor-free rats approaching 12.5% in middle-aged and 43% in old rats. In addition, 66% of mammary glands obtained from young rats that are subsequently at an increased risk to develop breast cancer due to manipulation of in utero dietary fat intake, exhibited methylation loss while no methylation changes were observed in rats at no increased risk for breast cancer. Therefore, the loss of ER methylation is more extensive in mammary glands of rats at high than low breast cancer risk, in old than young, and in mammary tumors than in normal tissues. The data suggest that hypomethylation of a growth-associated ER gene may be a common event in mammary tumorigenesis in the rat and may be of predictive value as a marker of increased breast cancer risk in aged individuals.

Establishment and characterization of three androgen-independent, metastatic carcinoma cell lines from 3,2'-dimethyl-4-aminobiphenyl-induced prostatic tumors in F344 rats

Three stable carcinoma cell lines, designated PLS10, PLS20 and PLS30, have been established from 3,2'-dimethyl-4aminobiphenyl plus testosterone-induced carcinomas in the dorsolateral prostate of male F344 rats. The cells are keratin-positive and grow as typical epithelial monolayers in culture. When injected into intact male nude mice, PLS10 and PLS30 cells form well-differentiated adenocarcinomas with abundant connective tissue stroma, while PLS20 cells give rise to poorly differentiated adenocarcinomas. Growth of all PLS cell lines in nude mice is not affected by castration and the cells are immunohistochemically negative for androgen receptors. Tumor growth rates in nude mice were found to be PLS20 > PLS10 > PLS30, with significant in vitro stimulation by insulin/transferrin, but not epidermal growth factor, dexamethasone or basic fibroblast growth factor. Spontaneous lung metastases were observed in all cases. However, skeletal invasion including bone is essentially observed only with the PLS20 tumors. Gelatin zymography showed predominant secretion of the active form of gelatinase B (Mr 92,000 type IV collagenase) by all the cell lines. Karyotype analysis revealed PLS10, PLS30 and PLS20 to be diploid, hyperdiploid and hypertetraploid, respectively. The results demonstrate that the three PLS cell lines are androgen-independent and metastatic in common, but have different histology, growth potential and invasiveness. They may therefore be useful models for understanding progression and metastasis of human prostatic carcinomas.

Anti-invasion drugs

Most of the pharmaceuticals in clinical practice today for treatment of breast and other cancers are cytotoxic or cytostatic inhibitors of tumor growth. While this type of drug has found its place, along with surgery and radiotherapy, in treatment of disease, the breast cancer death rate has not decreased. This appears to be the result of rising incidence, resistance to therapy, and metastasis of the disease. Since distant metastasis (usually indicated by lymph node involvement) of breast cancer is related only indirectly to tumor size, it would appear that a concerted effort should be made to discover drugs which directly interfere with this complex process. Metastasis appears to depend upon tumor cell motility, dedifferentiation, local invasion, and angiogenesis. Significant progress has been recently made in the creation of new animal models of metastasis and in identifying several new drugs which may be suitable for clinical inhibition of this process. This article reviews current findings on anti-invasion/metastasis drugs with a focus on breast cancer.

Establishment and characterization of high- and low-lung-metastatic cell lines derived from murine colon adenocarcinoma 26 tumor line

We established and characterized high- (LuM1) and low-lung-metastatic (NM11) cell lines derived from murine colon adenocarcinoma 26 tumor line. LuM1 cell line was established as a clonal cell line from a cultured cell mixture derived from a lung-metastatic nodule after 7 sequential subcutaneous transplantations of lung-metastatic tumors in the abdominal wall of BALB/c mice. NM11 cell line was established from a cultured cell mixture derived from a subcutaneous transplant of murine colon adenocarcinoma 26 tumor cells. LuM1 cells showed marked spontaneous lung metastases, but NM11 cells rarely did. High invasive potential of LuM1 cells was revealed by in vitro invasion assay using Matrigel reconstituted membranes. Rapid retraction was observed in monolayers of human umbilical vein endothelial cells and bovine aortic endothelial cells when LuM1 cells were added on the monolayers. Gelatin zymography and immunochemical examinations with monoclonal antibodies against gelatinase B (Mr 95,000 type IV collagenase) showed secretion of large amounts of the gelatinase by LuM1 cells.