The extent of proliferative and apoptotic activity in intraductal and invasive ductal breast carcinomas detected by Ki-67 labeling and terminal deoxynucleotidyl transferase-mediated digoxigenin-11-dUTP nick end labeling

BACKGROUND: The balance among cell proliferation, cell differentiation, and cell death determines the cell number in a population as well as the size or even the stage of a tumor. Thus, to improve our understanding of the pathogenesis of neoplasms, it is important to investigate the regulation of both cell proliferation and cell death. METHODS: This study examined the occurrence of apoptosis and proliferative capacity in 46 breast carcinomas: 20 intraductal carcinomas (ductal carcinomas in situ [DCIS]) and 26 infiltrative ductal carcinomas (IDC). Terminal deoxynucleotidyl transferase-mediated digoxigenin-11-dUTP nick end labeling (TUNEL) and immunostaining with the Ki-67 antibody were used in the examination. A ladder of DNA fragments induced by apoptosis was demonstrated by means of DNA agarose gel electrophoresis in 10 of the available TUNEL positive and negative samples. RESULTS: The results were correlated with p53, bcl-2, estrogen receptor (ER), and progesterone receptor (PR) protein expression, which would suggest association with apoptosis by immunohistochemistry. The apoptosis and proliferation of each cancer were expressed as the number of tumor cells undergoing apoptosis and proliferation per 1000 tumor cells. The extent of apoptosis was more frequently observed in DCIS than in IDC (21.9+/-6.8 vs. 4.0+/-0.9, P < 0.001), and the proliferation activity was significantly higher in IDC than in DCIS (16.8+/-6.5 vs. 3.5+/-0.8, P < 0.006). Apoptosis associated with MIB-1 positive cells and TUNEL labeling was significantly higher in IDC than in DCIS (3.26 vs. 0.42, P=0.001). In DCIS, apoptosis was correlated with p53 (r=0.663, P=0.005), and p53 had a reverse correlation with bcl-2 (r=0.620, P= 0.018). Moreover, bcl-2 expression was associated with ER (P=0.028) and PR (P= 0.005) expression in both DCIS and IDC. CONCLUSIONS: The results of this study show that a higher degree of apoptosis and lower proliferation activity in intraductal carcinoma result in a steady-state, self-renewing condition in which net growth of the tumor is rare. The results also indicate that apoptosis was altered by the expression of p53, bcl-2, ER, and PR.     

Gestational squamous cell carcinoma of the breast: an unusual mammary tumor associated with aggressive clinical course

We report two cases of squamous carcinoma of the breast detected during the gestational period. One woman was post-partum and lactating; one was in the first trimester of pregnancy. The lesions were clinically palpable, multifocal, and measured more than 5 cm in their largest dimension; both had a cystic appearance. They were treated with radical mastectomy. One patient received pre-operatory chemotherapy. Histologically, the tumors were poorly differentiated squamous cell carcinomas. No areas of ordinary duct differentiation were seen. Lymph nodes contained metastatic squamous carcinoma in both cases. Tumor cells were negative for estrogen and progesterone receptors. Also, they expressed a high proliferative index and several markers of tumor progression, including cErb-B2, p53 protein, bcl-2, and epidermal growth factor receptor. One patient died of tumor 5 months following breast surgery and had extensive metastases proven at autopsy. The other patient had evidence of pulmonary metastases: following cisplatin therapy, she underwent clinical remission. This study shows that squamous carcinoma of the breast may occur in pregnant or lactating women: it appears clinically distinguishable from the non-gestational type that is usually associated with a better prognosis and occurs in peri- or postmenopausal women.     

Paraneoplastic demyelinating disorder in the brain of a patient with seminoma

OBJECTIVE: To evaluate the estrogen and progesterone receptor status of glassy cell carcinoma of the cervix to assess the possible implications of hormone replacement therapy in these patients. METHODS: The estrogen and progesterone receptor status of 13 glassy cell carcinomas was evaluated by immunohistochemistry using commercial monoclonal antibodies and a streptavidin-biotin detection system. RESULTS: No immunohistochemically detectable estrogen or progesterone receptor protein was present in tumor cells, although both receptors were identified in the adjacent normal cervical tissue. CONCLUSION: The absence of estrogen and progesterone receptors in glassy cell carcinoma suggests that this tumor would not be hormonally responsive and that these patients can be safely treated with hormone replacement therapy. Further studies are indicated to confirm this observation.     

Fatty acid synthase expression in endometrial carcinoma: correlation with cell proliferation and hormone receptors

BACKGROUND: Fatty acid synthase (FAS), a biosynthetic enzyme, normally functions in the liver to convert dietary carbohydrate to fat, but it is minimally expressed in most other normal adult tissues. FAS is expressed at markedly elevated levels in subsets of human breast, ovarian, and prostate carcinomas that are associated with poor prognoses. During the menstrual cycle, the expression of FAS in the human endometrium is closely linked to the expression of the proliferation antigen Ki-67, estrogen receptor (ER), and progesterone receptor (PR). METHODS: This study reports the expression patterns of these antigens in 35 endometrial carcinomas as determined by immunohistochemical analysis. RESULTS: All cases demonstrated a close direct correlation between FAS and Ki-67 expression. Average FAS expression levels were correlated with tumor grade. Twenty-five carcinomas that were positive for ER and PR showed close correlation in expression of FAS, Ki-67, and hormone receptors. Individual tumors displayed varying degrees of heterogeneity of expression. A few well-differentiated carcinomas showed very low expression of all four antigens, similar to the antigenic profile of secretory endometrium. Nine high grade carcinomas that were negative for ER and PR also showed close correlation in expression of FAS and Ki-67 with uniformly high expression. CONCLUSIONS: These data suggest the following hypothesis: In hormone-dependent endometrial cells, FAS expression is part of the estrogen-driven cellular response that leads to proliferation; however, its linkage to proliferation is such that FAS expression is maintained in proliferating cells in endometrial carcinomas that acquire hormone independence. The use of these four antibodies as a panel may increase the diagnostic utility of ER and PR immunohistochemistry for tumor classification and prediction of the responsiveness of tumors to hormonal therapy.     

Molecular modeling of the transmembrane segment of Na+-K+-ATPase. A pentagonal model]

Retrograde differentiation (or dedifferentiation) has recently been proposed as a pathogenetic mechanism involved also in various renal diseases. Here we studied whether evidence of these mechanisms can be found in the kidneys of patients with congenital nephrotic syndrome of the Finnish type (CNF). These patients show isolated massive proteinuria but no primary symptoms from any other organ systems. For the analysis we used antibody markers of early (fibronectin, stem cell factor, Wilms' tumor gene product, cytokeratin) and later (laminin, midgestation and kidney, heparin binding growth-associated molecule) stages of nephron differentiation as well as for apoptosis (acridine orange staining), rescue from apoptosis (anti-Bcl-2 antibodies) and cell proliferation (antibodies to proliferating cell nuclear antigen). In the peritubular spaces atypically organized areas were found which appeared positive with markers of low stages of differentiation, but neither abnormal cell proliferation nor activation of the apoptotic pathway could be detected. As morphologic signs of abnormal tissue organization, we found clusters of tightly compacted and large glomeruli corresponding to the size of two to three normal glomeruli. However, all individual glomerular cell compartments (mesangial, endothelial, visceral epithelial cells) appeared balanced in relative cell numbers. Together these results may indicate abnormal early mesenchymoepithelial tissue interaction leading to excessive and poorly organized formation of glomeruli. This could be causally related also to the serious functional immaturity of CNF kidneys presented as isolated proteinuria.     

Insulin-like growth factor-I expression in normal and diseased endometrium

While the role of steroid hormones in the regulation of endometrial proliferation and differentiation is well established, the effects of growth factors and their receptors in normal and neoplastic endometrium remain a matter of debate. Previous studies have documented the positive effects of insulin-like growth factor-I (IGF-I) on epithelial cell proliferation and the active production of this growth factor in endometrial tissues. In view of decreased expression of transforming growth factor-beta1 (TGF-beta1), an antagonist of IGF-I, in endometrial carcinoma, we investigated the expression of IGF-I, at both the mRNA and protein levels, and the immunoreactivity for type I IGF-I receptor in 30 formalin-fixed, paraffin-embedded tissue samples of normal and neoplastic endometrium, in order to possibly clarify the role of IGF-I in endometrial proliferation and differentiation. Our results demonstrate a reduced expression of IGF-I mRNA in endometrial carcinomas compared with non-neoplastic tissues, despite equivalent immunohistochemical expression of IGF-I and IGF-I receptor. Our data suggest that IGF-I and its corresponding receptor may not be directly involved in endometrial cancer cell proliferation and differentiation in vivo, though other components of the IGF-I system (e.g., IGF binding proteins) may affect endometrial malignant transformation and tumor progression.     

Pre-operative radio-chemotherapy enhances apoptotic cell death in oral squamous cell carcinoma

The effect of pre-operative radio-chemotherapy (RCT) has been examined in a total of 15 oral squamous cell carcinomas (SCCs), in terms of apoptosis (cell loss) and proliferation. All the patients received pre-operative radiation at a dosage of 30 or 40 Gy, as well as anticancer agents including tagaful (FT), 5-fluorouracil (5-FU), bleomycin (BLM) and peplomycin (PEP). Surgical specimens were obtained before and after RCT, and serial sections were prepared for immunohistochemistry for p53 oncoprotein and Ki-67 antigen, as well as for terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL). TUNEL indices (TI; percentage of TUNEL-positive cells in the tumor cells) before and after RCT were 1.2+/-1.1 and 4.7+/-2.9 in the nine well-differentiated oral SCCs, and 1.0+/-0.7 and 3.9+/-2.1 in the six poorly differentiated SCCs, respectively. Similarly, Ki-67 indices (KI; percentage of Ki-67 antigen-positive cells in tumor cells) before and after RCT were 31.1+/-14.2 and 15.8+/-11.1 in the former, and 37.1+/-7.8 and 8.7+/- 13.4 in the latter, respectively. Thus, pre-operative RCT enhanced apoptotic cell death and abated proliferative activity significantly (P<0.05), regardless of histological differentiation. Enhancement of apoptosis was more prominent in the group treated with FT or 5-FU than with BLM or PEP. Oral SCC with >20% of nuclear p53-positive tumor cells was noted in six cases. Enhanced TI and abadement of KI did not differ among the p53-positive and -negative tumors.     

Distribution of surviving tumor cells after chemoradiotherapy in tongue and floor of mouth carcinomas

BACKGROUND: Conservative surgery according to the clinical response to induction therapy is applied in breast carcinomas but not yet in head and neck carcinomas. The possibility of conservative surgery after induction therapy for preservation of function was examined. METHODS: Forty-three tongue and 15 floor of mouth carcinomas that had received induction therapy and tumor resection were submitted for a comparative investigation on the clinical effect of induction therapy and cancer cell degeneration, which was examined in semiserial specimens from the bread-loaf sections of the excised materials, and a classification of the surviving tumor cell distribution in the tissue was proposed. The distribution was divided into four patterns according to the dispersion and volume of the remaining tumor cells (pattern I, no surviving tumor cells; pattern IIA, viable tumor cells in the central superficial region of the original tumor tissue; pattern IIB, viable cells in the superficial portion, but distributed widely; pattern III, massive tumor cell nests in the deep portion, but centrally localized; pattern IVA, sporadical viable cell islands, but not in the periphery; and pattern IVB, diffuse viable cells scattered throughout the original tumor tissue). RESULTS: The original tumor size did not affect the remaining viable tumor cell distribution pattern, but sporadic distribution patterns (patterns IVA and IVB) were observed in most of the T4 cases. In many cases, especially in tumors of the nondiffuse invasion type (invasion of grade 1 and 2), the tumor remission rate was inversely correlated with the dispersion of the viable tumor cells. However, some cases of grade 3 and 4 invasion exhibited sporadical surviving tumor cells even though a high tumor remission rate was obtained. These tumors, especially those located on the floor of the mouth, recurred with high frequency. CONCLUSIONS: Conservative surgery can be applied to nondiffuse invasion cases, according to the tumor remission rate. In T3 and T4 cases exhibiting grade 3 or 4 invasion, conservative surgery is ill-advised, even if more than 90% tumor remission is obtained.     

Expression of p21WAF1 predicts outcome of esophageal cancer patients treated by surgery alone or by combined therapy modalities

The p21WAF1 protein is an important regulator of the cell cycle. Its expression and prognostic significance were investigated immunohistochemically in samples of normal esophageal squamous epithelium (n = 10), severe squamous cell dysplasia (n = 20), carcinoma in situ (n = 14), permanent esophageal squamous cell carcinoma cell lines (n = 3), and invasive squamous cell carcinomas treated either by potentially curative resection (n = 172) or by combined modality therapy (radiochemotherapy +/- surgery; n = 38). Whereas p21WAF1 expression in the normal epithelium was restricted to a few cells adjacent to the basal cell layer, p21WAF1 overexpression was frequently found in preneoplasias and invasive carcinomas. Expression of p21WAF1 in invasive carcinomas was not correlated with tumor differentiation, pT category, or pN category. Among carcinomas treated by potential curative resection, univariate (P = 0.0025) and multivariate (P = 0.0081) survival analysis showed significant correlation of strong p21WAF1 expression (> or =50% p21WAF1-positive tumor cells) with poor overall survival. Univariate survival analysis (P = 0.0006) revealed the same prognostic influence in the group of patients treated by combined modality therapy. We conclude that overexpression of p21WAF1 protein is a frequent event in preneoplasias and neoplasias of the esophagus. Immunohistochemical examination of p21WAF1 expression may provide important prognostic information for decision-making in the treatment of patients with esophageal cancer.     

The cancer growth suppressor gene mda-7 selectively induces apoptosis in human breast cancer cells and inhibits tumor growth in nude mice

A differentiation induction subtraction hybridization strategy is being used to identify and clone genes involved in growth control and terminal differentiation in human cancer cells. This scheme identified melanoma differentiation associated gene-7 (mda-7), whose expression is up-regulated as a consequence of terminal differentiation in human melanoma cells. Forced expression of mda-7 is growth inhibitory toward diverse human tumor cells. The present studies elucidate the mechanism by which mda-7 selectively suppresses the growth of human breast cancer cells and the consequence of ectopic expression of mda-7 on human breast tumor formation in vivo in nude mice. Infection of wild-type, mutant, and null p53 human breast cancer cells with a recombinant type 5 adenovirus expressing mda-7, Ad.mda-7 S, inhibited growth and induced programmed cell death (apoptosis). Induction of apoptosis correlated with an increase in BAX protein, an established inducer of programmed cell death, and an increase in the ratio of BAX to BCL-2, an established inhibitor of apoptosis. Infection of breast carcinoma cells with Ad.mda-7 S before injection into nude mice inhibited tumor development. In contrast, ectopic expression of mda-7 did not significantly alter cell cycle kinetics, growth rate, or survival in normal human mammary epithelial cells. These data suggest that mda-7 induces its selective anticancer properties in human breast carcinoma cells by promoting apoptosis that occurs independent of p53 status. On the basis of its selective anticancer inhibitory activity and its direct antitumor effects, mda-7 may represent a new class of cancer suppressor genes that could prove useful for the targeted therapy of human cancer.     

Expression of galectins in head and neck squamous cell carcinoma

BACKGROUND: Galectins are carbohydrate-binding proteins thought to be important for cell growth and differentiation, whose expression is altered in some tumors with aggressive phenotype. Our objective was to evaluate the expression of galectins in head and neck squamous cell carcinoma (HNSCC). METHODS: Fourteen HNSCC cell lines and four primary tumor specimens were evaluated using immunoblotting, and immunohistochemical analysis was performed on 35 primary HNSCCs. RESULTS: Galectin-1 and galectin-3 were expressed in most HNSCC cell lines and primary tumor specimens. Galectin-1 was detected in the basal layer of normal adjacent mucosa, in connective tissue stroma, and at the periphery of invasive tumor islands. Galectin-3 localized to superficial mucosal layers, and adjacent to keratin pearls in invasive carcinoma. CONCLUSIONS: Galectins are manifested in HNSCC tumors and are localized to the cell surface, where they may participate in cellular interactions. The expression pattern of galectins appears to be associated with degree of squamous differentiation, suggesting a potential role for galectins as biologic and differentiation markers in HNSCC.     

Down-regulation of laminin-5 in breast carcinoma cells

BACKGROUND: Laminin-5 (ln-5), a large heterotrimeric glycoprotein consisting of an alpha 3, beta 3, and gamma 2 chain, is a component of epithelial cell basement membranes that functions as a ligand of the alpha 3 beta 1 and alpha 6 beta 4 integrins to regulate cell adhesion, migration, and morphogenesis. The ln-5 chains show tissue-specific patterns of regulation in tumors derived from different tissues. For example, ln-5 is often up-regulated in gliomas, gastric carcinomas, and squamous carcinomas and down-regulated in prostate and basal cell carcinomas. Ln-5 expression patterns may represent useful tumor markers and help to elucidate the role of ln-5 in tumor progression in different tissue types. MATERIALS AND METHODS: We have studied ln-5 expression patterns in the breast. mRNA levels were examined in tumor and normal breast epithelial cell lines, tissue samples, and immunomagnetically sorted primary cultures using differential display, Northern blotting, and hybridization arrays. Protein levels were examined by immunoprecipitation. Gene integrity was assessed by Southern blotting of representative cell types. RESULTS: Ln-5 alpha 3, beta 3, and gamma 2 mRNA expression was found to be markedly down-regulated in a panel of breast tumor cell lines when compared with normal breast epithelial cells. Ln-5 mRNA was expressed at relatively high levels in MCF-10A immortal normal breast epithelial cells, long-term cultures of normal breast cells, and sorted primary cultures of normal breast luminal epithelial and myoepithelial cells. Reduced, but detectable, levels of ln-5 tended to be expressed in cell lines derived from early-stage breast tumors, whereas expression was generally not detected in cell lines derived from later-stage tumors. In breast tumor tissue specimens, expression of ln alpha 3 and beta 3 mRNAs tended to be reduced relative to levels observed in adjacent nontumor tissue, whereas in gamma 2 levels were elevated in specimens with increased amounts of myoepithelial cells. These ln-5 expression changes could not be attributed to large-scale mutations or gene rearrangements. Ln-5 protein levels were found to reflect mRNA levels in representative cell lines. At senescence, a growth state believed to suppress tumorigenesis, expression of all three ln-5 mRNAs was up-regulated. CONCLUSION: The down-regulation of ln-5 mRNA expression in breast tumors cells provides a new molecular marker and suggests that ln-5 functions to control tumor progression in the breast.     

Angiogenesis and apoptosis are cellular parameters of neoplastic progression in transgenic mouse models of tumorigenesis

The epidemiology and histopathology of human cancers and studies of animal models of tumorigenesis have led to a widely-accepted notion that multiple genetic and epigenetic changes have to accrue for the successful development of a malignant phenotype. Tumor growth and expansion requires an ability not only to proliferate, but also to down-modulate cell death (apoptosis) and activate angiogenesis to produce a tumor neovasculature. This review will describe the interplay between apoptosis and proliferation, as well as the characteristics of the angiogenic phenotype in two transgenic mouse models of multi-step tumorigenesis, namely, pancreatic islet cell carcinomas and squamous cell carcinomas of the skin.     

Inhibition of human squamous cell carcinoma growth in vivo by epidermal growth factor receptor antisense RNA transcribed from the U6 promoter

BACKGROUND: Squamous cell carcinomas of the head and neck (SCCHN), unlike normal mucosal squamous epithelial cells, overexpress epidermal growth factor receptor (EGFR) messenger RNA and protein. EGFR protein is required to sustain the proliferation of SCCHN cells in vitro. To determine whether EGFR expression contributes to tumor growth, we investigated the effect of suppressing EGFR expression in tumor xenografts through in situ expression of antisense oligonucleotides. METHODS: Intratumoral cationic liposome-mediated gene transfer was used to deliver plasmids capable of expressing sense or antisense EGFR sequences into human head and neck tumors, which were grown as subcutaneous xenografts in nude mice. The oligonucleotides were expressed under the control of the U6 RNA promoter. RESULTS: Direct inoculation of the EGFR antisense (but not the corresponding sense) plasmid construct into established SCCHN xenografts resulted in inhibition of tumor growth, suppression of EGFR protein expression, and an increased rate of apoptosis (programmed cell death). Sustained antitumor effects were observed for up to 2 weeks after the treatments were discontinued. CONCLUSION: These results suggest that interference with EGFR expression, using an antisense-based gene therapy approach, may be an effective means of treating EGFR-overexpressing tumors, including SCCHN.     

Estrogens, progestogens, normal breast cell proliferation, and breast cancer risk

Epidemiologic studies suggest that ovarian hormones contribute to the development of breast cancer at all stages. Early menopause and premenopausal obesity reduces the risk while postmenopausal obesity and menopausal estrogen replacement therapy increases the risk. Combined oral contraceptives and Depo-Provera do not reduce the risk. It appears that estrogens and progestogens act through and with proto-oncogenes and growth factors to affect breast cell proliferation and breast cancer etiology. Animal studies suggest that estrogen causes interlobular ductal cell division and progesterone causes increased terminal duct lobular unit cell division in the luteal phase. Most breast carcinomas originate from terminal duct lobular unit cells. During pregnancy, these cells fully multiply. Their reproduction is also increased during the luteal phase. Yet, there is considerable interpersonal variation. No studies examining breast cell division have compared cell division rates with serum hormone concentrations, however. The peak of mitosis occurs about 3 days before breast cell death in the late luteal and very early follicular phases. Other research suggests that breast stem cell proliferation is linked to breast cancer development. Endocrine therapy reduces mitotic activity, indicating the estrogen and progesterone receptor content of breast cancers. Hormone-dependent breast cancer cell lines are all estrogen-dependent. Progesterone can block the estrogen-dependent cell lines which act like endometrial cells. The results of the various breast cell proliferation studies in relation to breast cancer are unclear and research identifying a molecular explanation would help in understanding the different findings.     

Tissue expression of Sialyl Tn antigen in gynecologic tumors

OBJECTIVES: To investigate tissue expression of Sialyl Tn antigen (STN) in gynecologic tumors, and to compare with its appearance in blood circulation. METHODS: Surgical specimens were obtained from 24 patients with malignant gynecologic diseases, including 7 ovarian cancers, 13 cervical cancers, 3 endometrial cancers, and 1 vulval cancer. Control tissues were also obtained at surgery from 28 patients with benign tumors of the ovary or uterus. RESULTS: Anti-STN monoclonal antibody (TKH-2) positively identified 6 (86%) of 7 ovarian cancers, 11 (85%) of 13 cervical squamous-cell carcinomas, but none of 3 endometrial cancers. None of the 28 benign tissues, including 11 ovarian benign tumors, showed positive immunostaining for STN, except 1 with an ovarian chocolate cyst which showed weak staining for STN. No expression was found in normal squamous epithelium distant from the lesion. Serum STN antigen was positive in 4 of 7 ovarian cancers (cutoff = 39 U/ml), but only in 2 of 13 cervical cancers, and none in the 3 endometrial cancers. CONCLUSIONS: These findings indicate different behaviors in the appearance of STN in tumor tissue and blood circulation, and also suggest the possible applicability of STN to immunohistochemical diagnosis of squamous-cell carcinomas.     

Down-regulated expression of transforming growth factor beta 1 mRNA in endometrial carcinoma

Transforming growth factor beta1 (TGF-beta1) is a potent modulator of cell proliferation in vitro, and recent studies have demonstrated its overexpression in several different tumours; nevertheless, the molecular mechanisms of TGF-beta1 action on cell growth and differentiation have not been fully elucidated. To clarify the role of TGF-beta and its receptor in human endometrial proliferation and differentiation, TGF-beta1 expression at both the mRNA and protein levels has been evaluated by using Northern blotting and immunohistochemistry, in both normal (atrophic, proliferative and secretory) and neoplastic (adenocarcinoma) endometrial samples. This study demonstrates that TGF-beta1 mRNA expression is dramatically reduced in endometrial carcinomas with respect to non-neoplastic tissues, whereas the immunohistochemical expression of TGF-beta1 is enhanced in the epithelial component of endometrial carcinomas compared with non-neoplastic tissues. These data suggest that TGF-beta1 acts as a paracrine regulator of endometrial cell proliferation and that it may contribute to the carcinogenic mechanisms of endometrial carcinoma.     

Establishment and characterization of six new human endometrial adenocarcinoma cell lines

The endometrial carcinoma cell lines EC-MZ-1, 2, 3, 5, 9, and 11 were established between 1986 and 1990. Four cell cultures were started from endometrial tissue, one from ascites, and one from a lymph node metastasis. Lines have to date been subcultured up to 180 times and the doubling time varies between 26 hr and 3 weeks. Immunocytochemically the coexpression of cytokeratin (predominantly simple-epithelial cytokeratin polypeptides) and vimentin intermediate filaments was detectable in all cell lines, but three lines (EC-MZ-5, 9, 11) expressed vimentin only at low level. By transmission electron microscopy the tumor cells exhibited features of epithelial differentiation. After subcutaneous transplantation into nude mice three lines (EC-MZ-1, 2, 5) produced slow-growing tumors. The histological classification of these tumors ranged from moderately differentiated adenocarcinoma to undifferentiated carcinoma and closely corresponded to the original tumor. Even after long-term in vitro culture, without any addition of estrogens to the culture medium, the moderately differentiated receptor-positive cell line (EC-MZ-2) retained its morphological differentiation. The cells were propagated without estrogens in the culture medium. The estrogen and progesterone receptor levels of cultured cells were determined. Three lines (EC-MZ-1, 2, 3) were positive for the progesterone receptor in low passage number only, the other cell lines were negative for both receptors. The transplantable lines were investigated for hormonal receptor expression in ovariectomized nude mice. In the moderately differentiated cell line (EC-MZ-2) we observed an enhanced expression of the estrogen receptor under optimal stimulation of the nude mouse with estradiol benzoate. There was no effect on the expression of the progesterone receptor.