Expression of nuclear retinoid receptors in normal, premalignant and malignant gastric tissues determined by in situ hybridization

Retinoids exhibit multiple functions through interaction with nuclear retinoid receptors and have growth-suppressive activity on gastric cancer cells. To better understand the roles of nuclear retinoid receptors during gastric carcinogenesis, we have used in situ hybridization to investigate expression of retinoic acid receptors (RARs) and retinoid x receptors (RXRs) in premalignant and malignant formalin-fixed paraffin-embedded gastric tissues. Histological sections of eight normal, 17 distal normal and nine gastric cancer tissues were hybridized with non-radioactive RNA probes for subtypes of RAR and RXR. Expression of RAR alpha, RAR beta, RAR gamma, RXR alpha and RXR beta was found in most cell types in gastric mucosa tissues from normal individuals as well as in distal normal tissues from cancer patients. Expression of RAR alpha and RAR beta were found in three and seven cancer tissues, respectively, and levels of RXR alpha mRNA were significantly decreased in poorly differentiated cancer tissues. Among the five investigated nuclear retinoid receptors, only expression of RAR alpha mRNA was significantly decreased in intestinal metaplasia, dysplasia and cancer tissues when compared to adjacent normal tissues. In conclusion, normal gastric mucosa expressed both RARs and RXRs, which supports the physiological role of retinoic acid on normal gastric mucosa. The decrease in RAR alpha expression in premalignant and malignant gastric tissues suggests a significant role of RAR alpha during gastric carcinogenesis.

High frequency of cytotoxin-associated gene A in Helicobacter pylori isolated from asymptomatic subjects and peptic ulcer patients in Taiwan

Cytotoxin-associated gene A (CagA), expressed in about 60% of H. pylori isolates in Western countries, may play a role in the pathogenesis of peptic ulcer. In this study, we determined the prevalence and significance of the H. pylori cagA gene and protein expression in Taiwan. Genomic DNA from antrum biopsies and H. pylori isolates were analyzed for cagA using polymerase chain reaction, Southern hybridization, or colony hybridization. CagA seropositivity was analyzed using Helico blots. In addition, Western blotting was performed to detect the CagA protein. About 94% of antrum tissues from both asymptomatic subjects and duodenal ulcer patients and all 76 H. pylori isolates (21 asymptomatic subjects, 39 with duodenal ulcers, 13 with gastric ulcers, 2 with gastric cancers, and 1 with mucosa-associated lymphoid tissue [MALT] lymphoma) were positive for the cagA gene. Moreover 77 out of 78 H. pylori-positive serum and all 27 H. pylori lysates had anti-CagA antibodies or CagA protein, respectively. H. pylori isolated from patients with various upper gastrointestinal diseases in Taiwan contained the cagA gene and expressed CagA protein at high frequencies.

Effects of tamoxifen and retinoic acid on cell growth and c-myc gene expression in human breast and cervical cancer cells

The effects of estradiol, tamoxifen, and retinoic acid on the proliferation of breast and cervical cancer cells were investigated. Estrogen stimulated only MCF-7 cell growth, whereas tamoxifen and retinoic acid inhibited the proliferation of all cells studied. Northern blot analysis indicated that estradiol up-regulates c-myc mRNA level in all cell lines studied regardless of the estrogen receptor status in the cells. On the contrary, tamoxifen inhibits c-myc gene expression in all cell lines studied except in MCF-7 cells where the c-myc transcript was not affected. The inhibitory effect of tamoxifen on c-myc gene expression and cell proliferation in estrogen receptor-negative cells suggest an estrogen receptor-independent mechanism. The results also suggest that different mechanisms are involved in the regulation of cell growth and c-myc gene expression in different cancer cells by estrogen and tamoxifen.

Dexamethasone suppresses apoptosis in a human gastric cancer cell line through modulation of bcl-x gene expression

Treatment of human gastric cancer TMK-1 cells with transcription and translation inhibitors rapidly triggered cell apoptosis. Along with cell apoptosis, the Bcl-xS level was markedly upregulated suggesting a crucial role of this protein in promoting the apoptotic process. In the presence of dexamethasone, however, cell apoptosis was greatly attenuated as demonstrated by DNA histogram shift and DNA fragmentation. Studies using the glucocorticoid receptor antagonist RU486 indicated that attenuation of apoptosis was mediated through glucocorticoid receptors. Dexamethasone not only suppressed the apoptosis-associated upregulation of Bcl-xS but also enhanced the basal level of Bcl-xL in the cells. In addition, bcl-x mRNA stability was significantly extended in the presence of dexamethasone. These results indicate that dexamethasone exerted a protective effect and delayed apoptosis of TMK-1 cells by modulating bcl-x gene expression.

Detection of alphafetoprotein-expressing cells in the blood of patients with hepatoma and hepatitis

The presence of tumour cells in the blood circulation may predict disease recurrence and metastasis. We have evaluated the specificity and sensitivity of detecting hepatoma cells in blood using nested polymerase chain reaction with primers specific for the alphafetoprotein (AFP) gene. The nested polymerase chain reaction amplified a 270-base pair AFP DNA fragment from cDNA of Hep 3B hepatoma cells. In a reconstitution experiment, AFP mRNA was detected from peripheral mononuclear cells isolated from 10 ml of blood containing as few as ten Hep 3B cells. Peripheral mononuclear cells from the blood of 20 hepatoma patients were analysed, and 19 patients showed positive AFP mRNA expression. Seven of 13 samples from hepatitis patients also showed positive AFP mRNA expression. All five paired samples of peripheral blood or umbilical cord blood from pregnant mothers and their babies, respectively, showed positive AFP expression. None of 22 control samples was positive. The presence of AFP mRNA in the blood of hepatitis or hepatoma patients suggests the presence of circulating hepatoma cells or hepatocytes in the circulation. The high incidence of AFP mRNA in the blood of hepatoma patients supports the notion of early haematogenous spreading of the disease.

All-trans retinoic acid decreases susceptibility of a gastric cancer cell line to lymphokine-activated killer cytotoxicity

All-trans retinoic acid (RA) was previously shown to regulate the growth of gastric cancer cells derived from the cell line SC-M1. This study was designed to investigate the effect of RA on the sensitivity of SC-M1 cells to lymphokine-activated killer (LAK) activity. RA at the concentration range of 0.001-10 microM was shown to induce SC-M1 cells to exhibit resistance to LAK activity in a dose-dependent manner. A kinetics study indicated that a significantly increased resistance was detected after 2 days of co-culturing SC-M1 cells with RA and reached a maximum after 6 days of culture. Similar results were obtained from two other cancer cell lines: promyelocytic leukaemia HL-60 and hepatic cancer Hep 3B. A binding assay demonstrated that the binding efficacy between target SC-M1 cells and effector LAK cells was not altered by RA. Flow cytometric analyses revealed that RA exhibited no effect on the expression of cell surface molecules, including HLA class I and class II antigens, intercellular adhesion molecule-1 and -2, and lymphocyte function antigen-3. Cell cycle analysis revealed that culture of SC-M1 cells with RA resulted in an increase in G0/G1 phase and a decrease in S phase, accompanied by a decrease in cyclin A and cyclin B1 mRNA as determined by Northern blot analysis. Additionally, RA was shown to enhance the expression of retinoic acid receptor alpha (RAR alpha) in SC-M1 cells, and to have no effect on the expression of RARbeta or RARgamma. Taken together, these results indicate that RA can significantly increase gastric cancer cells SC-M1 to resist LAK cytotoxicity by means of a cytostatic effect through a mechanism relating to cell cycle regulation. The prevailing ideas, such as a decrease in effector to target cell binding, a reduced MHC class I antigen expression or an altered RARbeta expression, are not involved.

In vitro and in vivo growth inhibition of SC-M1 gastric cancer cells by retinoic acid

Retinoids are differentiating agents that have been used successfully for the treatment of acute promyelocytic leukemia. When combined with interferons, they are active in preventing second malignancies in patients with head and neck cancer. Our previous studies have demonstrated cytostatic effects of alltrans-retinoic acid (tRA) on SC-M1 gastric cancer cells in vitro. The activity of tRA and 13-cis-retinoic acid (cRA) on SC-M1 cells was compared both in vitro and in vivo in this study. Measurement of total cellular DNA was used to determine cell growth in vitro. The effect of retinoic acid on tumor growth was evaluated by implanting sustained release tRA or cRA pellets into athymic nude mice. The results showed that tRA was more potent than cRA in suppressing the growth of SC-M1 gastric cancer cells in vitro. Both tRA and cRA were effective in suppressing the growth of SC-M1 tumors in athymic nude mice. No change in the differentiation status and cell cycle phase distribution in excised tumors was observed. Side effects such as bone fractures and weight loss were observed in mice of both treatment groups. The results suggest that retinoic acid may provide therapeutic advantages for the treatment of gastric cancer.

Tamoxifen inhibits hepatoma cell growth through an estrogen receptor independent mechanism

BACKGROUND/AIMS

Tamoxifen has previously been shown to prolong the survival of patients with advanced stages of hepatocellular carcinoma and it has been suggested that it inhibits the growth of hepatoma cells through an estrogen receptor-dependent mechanism. We have studied the effects of the synthetic estrogen, mestranol, and the antiestrogen, tamoxifen, on the growth regulation of hepatoma cells in vitro.

METHODS

Cells were maintained under fully estrogenized conditions and were deprived of estrogen shortly before conducting experiments.

RESULTS

In the human hepatoma cell line Hep 3B, tamoxifen inhibited cell growth in a concentration and time-dependent manner with effective concentrations ranging from 0.1 microM to 10 microM. Mestranol inhibited cell growth at a concentration of 10 microM and had an additive effect with tamoxifen on growth inhibition. Expression of estrogen receptors in hepatoma cells was not detected by enzyme immunoassay, Northern blot analysis or reporter gene expression assay. Furthermore, the introduction of estrogen receptors into Hep 3B cells did not alter the effect of tamoxifen and mestranol on cell growth.

CONCLUSIONS

This study suggests that tamoxifen inhibits the growth of Hep 3B hepatoma cells through an estrogen receptor-independent mechanism.

An estrogen-independent MCF-7 breast cancer cell line which contains a novel 80-kilodalton estrogen receptor-related protein

Long-term growth of estrogen-responsive human breast cancer cell lines in estrogen-free media leads inevitably to the development of estrogen-independent growth. We have identified and characterized a unique subclone of the MCF-7 human breast cancer cell line, named MCF-7:2A, which grows maximally in the absence of endogenous estrogens but whose growth is inhibited by the antiestrogens 4-hydroxytamoxifen and ICI 164,384. The MCF-7:2A cells express high levels of estrogen receptor (ER; 477 fmol/mg protein), which can be reduced by growth in 10 nM 17 beta-estradiol (201 fmol/mg protein). Basal progesterone receptor synthesis is very low in the 2A cells (< 1 fmol/mg protein) but can be dramatically increased by 10 nM 17 beta-estradiol (384 fmol/mg protein). Clearly, the pathways that control growth and estrogen-regulated genes such as the progesterone receptor are now dissociated in these cells. MCF-7:2A cells also possess two unique characteristics. First, the MCF-7:2A cells constitutively activate an ER-responsive luciferase reporter construct in the absence of any estrogens, and this activation can be blocked by either 4-hydroxytamoxifen or ICI 164,384. This constitutive activity is not observed in the parental MCF-7 cells. Second, they express an 80-kDa protein that cross-reacts with three distinct antibodies to the ER. The MCF-7:2A cells were subjected to an additional round of limiting dilution subcloning, and 10 independent clones were all shown to express both the 66- and 80-kDa ERs as observed in the MCF-7:2A line. This confirms that both ERs are being expressed in each cell and are not the result of a mixed population of cells. While numerous ER variants have been reported previously, no ER has until now been described that is larger than the wild-type 66-kDa ER. The MCF-7:2A cells provide a unique model to use in the study of ER action and the development of estrogen-independent growth in human breast cancer cells.

Differential expression of the human metastasis adhesion molecule CD44V in normal and carcinomatous stomach mucosa of Chinese subjects

BACKGROUND

CD44 is a cell surface adhesion molecule involved in cell-cell and cell-matrix interactions. Tumor cells transfected to overexpress the isoform CD44V readily gain access to lymph nodes and form distant metastases.

METHODS

Monoclonal antibodies directed at epitopes common to known CD44 isoforms were used to investigate CD44V expression in 30 normal gastric mucosa tissues, 64 different gastric adenocarcinomas, 20 metastatic adenocarcinoma lymph nodes and 4 established gastric carcinoma cell lines. In addition, CD44V gene expression in six gastric adenocarcinoma tissues and four gastric cancer cell lines were investigated by northern blotting.

RESULTS

Immunohistochemistry screening of 30 subjects with normal gastric mucosa did not reveal expression of CD44 variants. Areas of intestinal metaplasia, a precancerous lesion, were stained with antibodies against either V5- or V6-containing isoforms of CD44. Tubular and signet-ring cell types of adenocarcinoma were strongly positive for epitopes encoded by CD44 variants containing exons V5 (41/49 and 10/10, respectively). Some tubular type adenocarcinomas (15/49) also expressed CD44 variants containing the V6 epitope. Tumor differentiation was closely related to CD44 V5 expression (P < 0.001). In addition, 18 of 20 gastric adenocarcinomas metastatic to lymph nodes expressed the V5 epitope of CD44 and 4 of 20 expressed the V6 epitope. Analysis of four established gastric adenocarcinoma cell lines revealed that two had moderate to strong expression of exons V5 and V6 of CD44. An antibody directed against CD44 variants containing exons V8 to V10 strongly stained all gastric adenocarcinoma cell lines. Northern blotting demonstrated that all four tumor cell lines and six gastric carcinoma mucosa tissues expressed CD44V.

CONCLUSIONS

Generation of CD44 splice variants may be closely linked with gastric carcinoma tumorigenesis and differentiation. In addition, expression of CD44 variants containing exons V5 and V6 may be used as an indicator of evolving gastric cancer.

Differential expression of the human metastasis adhesion molecule CD44V in normal and carcinomatous stomach mucosa of Chinese subjects

BACKGROUND

CD44 is a cell surface adhesion molecule involved in cell-cell and cell-matrix interactions. Tumor cells transfected to overexpress the isoform CD44V readily gain access to lymph nodes and form distant metastases.

METHODS

Monoclonal antibodies directed at epitopes common to known CD44 isoforms were used to investigate CD44V expression in 30 normal gastric mucosa tissues, 64 different gastric adenocarcinomas, 20 metastatic adenocarcinoma lymph nodes and 4 established gastric carcinoma cell lines. In addition, CD44V gene expression in six gastric adenocarcinoma tissues and four gastric cancer cell lines were investigated by northern blotting.

RESULTS

Immunohistochemistry screening of 30 subjects with normal gastric mucosa did not reveal expression of CD44 variants. Areas of intestinal metaplasia, a precancerous lesion, were stained with antibodies against either V5- or V6-containing isoforms of CD44. Tubular and signet-ring cell types of adenocarcinoma were strongly positive for epitopes encoded by CD44 variants containing exons V5 (41/49 and 10/10, respectively). Some tubular type adenocarcinomas (15/49) also expressed CD44 variants containing the V6 epitope. Tumor differentiation was closely related to CD44 V5 expression (P < 0.001). In addition, 18 of 20 gastric adenocarcinomas metastatic to lymph nodes expressed the V5 epitope of CD44 and 4 of 20 expressed the V6 epitope. Analysis of four established gastric adenocarcinoma cell lines revealed that two had moderate to strong expression of exons V5 and V6 of CD44. An antibody directed against CD44 variants containing exons V8 to V10 strongly stained all gastric adenocarcinoma cell lines. Northern blotting demonstrated that all four tumor cell lines and six gastric carcinoma mucosa tissues expressed CD44V.

CONCLUSIONS

Generation of CD44 splice variants may be closely linked with gastric carcinoma tumorigenesis and differentiation. In addition, expression of CD44 variants containing exons V5 and V6 may be used as an indicator of evolving gastric cancer.

Establishment and characterization of TSGH9201, a human gastric carcinoma cell line that is growth inhibited by epidermal growth factor

A human signet ring gastric carcinoma cell line TSGH9201 was established in vitro. The cells grew in vitro as a monolayer with polygonal morphology and had a population doubling time of 34 hours. The cells secreted tumor markers CEA and CA 125. They were, however, not tumorigenic in athymic nude mice. Karyotypic analysis demonstrated a near tetraploidy with a modal chromosome number of 98. Northern blotting and immunocytochemical analysis revealed the expression of both transforming growth factor alpha and high levels of epidermal growth factor receptor. Cell growth was inhibited by the epidermal growth factor in vitro. The cell line may be a useful tool to study autocrine growth regulation through the epidermal growth factor receptor.

Growth regulation by all-trans-retinoic acid and retinoic acid receptor messenger ribonucleic acids expression in gastric cancer cells

Retinoic acid has been recognised as a pivotal compound in cell differentiation, proliferation and malignant transformation. We investigated the effects of all-trans-retinoic acid on cell growth and the expression of retinoid nuclear receptor mRNAs in gastric cancer cells in vitro. Cell growth was quantified by measuring total cellular DNA. The growth of two of the five gastric cancer cell lines tested (SC-M1 and TSGH9201) was inhibited by all-trans-retinoic acid at concentrations ranging from 1 x 10(-8) M to 1 x 10(-6) M. Growth inhibition was associated with G0/G1 phase arrest as determined by flow cytometric analysis. Northern blot analysis showed that all five cell lines expressed mRNA for retinoic acid receptors alpha and retinoic x receptor alpha and beta. Retinoic acid receptor beta mRNA was only expressed in TSGH9201 and TMK-1 gastric cancer cell lines. Two RAR gamma mRNA transcripts (3.2 and 3.0 kb) were detected in SC-M1 and TSGH9201 cells. RA-resistant cells had markedly decreased levels of the 3.2 kb RAR gamma transcript. All-trans-retinoic acid had a cytostatic effect on the growth of some gastric cancer cells, which may be associated with the expression of retinoic acid receptors.

[The dynamic changes in glutathione peroxidase activity and malondialdehyde level in experimental traumatic cataract in rabbit]

Glutathione peroxidase activity (GSH-PX) and malondialdehyde (MDA) level of experimental traumatic cataract in rabbit were determined at various intervals after needling. GSH-PX activities decreased in the lens after perforated trauma from 8 hours to 21 days, meanwhile the MDA level increased markedly. The results demonstrate that free radicals are involved in the formation of traumatic cataract.

Paradoxical regulation of estrogen-dependent growth factor gene expression in estrogen receptor (ER)-negative human breast cancer cells stably expressing ER

We have previously demonstrated that transfection of estrogen receptor (ER)-negative human breast cancer MDA-MB-231 (clone 10A) cells with a sense constitutive wildtype ER expression vector regains hormonal responsiveness (Jiang and Jordan, J. Natl. Cancer Inst., 84 (1992) 580-591). We have therefore undertaken studies using stable transfectant S30 cells to determine the function of ER in the regulation of the levels of growth factor mRNAs, an event believed to be mediated via the ER and is important for the paracrine and autocrine regulation of breast cancer cell proliferation. Northern blot analysis demonstrated that 17 beta-estradiol (E2) increased the level of TGF alpha mRNA and decreased the level of TGF beta 2 mRNA. TGF beta 1 and TGF beta 3 mRNA levels were not affected by ER in S30 cells. The addition of anti-estrogen ICI 164,384 blocked the regulation of the mRNA levels of TGF alpha and TGF beta 2 by E2. The expression of these growth factor mRNAs was not affected by E2 or ICI 164,384 in the parental MDA-MB-231 10A and antisense ER transfectant AS23 cells. We demonstrated that the expression of ER in previously ER-negative human breast cancer cells can restore the regulation of growth factor mRNA expression by E2. An increase in TGF alpha and a decrease in TGF beta 2 is associated with an increase in growth of hormone responsive cells. Paradoxically the transfected cells have decreased growth in response to estrogen. Furthermore, these data suggest that other factors in addition to ER are required for TGF beta 1 and TGF beta 3 gene regulation by E2.

Inherited abnormalities in platelet organelles and platelet formation and associated altered expression of low molecular weight guanosine triphosphate-binding proteins in the mouse pigment mutant gunmetal

Gunmetal (gm/gm) is a recessively inherited mouse pigment dilution mutant that has high mortality and poor reproductive rates. In these studies, several hematologic defects were found associated with the mutation, including prolonged bleeding times, together with thrombocytopenia and increased platelet size. A unique feature is the presence of simultaneous abnormalities in two platelet organelles, dense granules and alpha-granules. The dense granule component serotonin is present at about half the normal concentration, as are visible dense granules. Three alpha-granule components (fibrinogen, platelet factor 4, and von Willebrand factor) are also significantly reduced. Thus, in several respects the gunmetal mutant resembles the human gray platelet syndrome. A novel abnormality in expression of low molecular weight guanosine triphosphate (GTP)-binding proteins occurs in platelets of gunmetal. In Western blot assays, two additional GTP-binding proteins of 28.5 and 25 Kd were detected. The abnormal expression of GTP-binding proteins is, like the hematologic defects, genetically recessive and is tissue specific. Liver, kidney, brain, spleen, macrophages, and neutrophils have normal GTP-binding protein expression. The additional GTP-binding proteins are soluble. The data indicate that platelet formation and platelet organelle biogenesis are under common genetic control and that abnormal regulation of GTP-binding proteins may affect one or both processes.

Modified polyvinyl alcohol-benzoporphyrin derivative conjugates as phototoxic agents

Photosensitizing and biodistribution characteristics of a photosensitizer (benzoporphyrin derivative, monoacid ring A; BPD) conjugated to a macromolecule (modified polyvinyl alcohol; M-PVA, molecular weight = 10,000) were tested in vitro and in vivo. Modified PVA was loaded with BPD at molar ratios 1:12, 1:25, 1:50, 1:75 and 1:100. Most of the work was carried out with a conjugate having a 1:25 molar ratio. In vitro photosensitization was tested using A549 (human lung carcinoma), A432 (human epidermoid carcinoma) and P815 (mastocytoma of DBA/2 mice) cell lines. Photosensitization of M1 (rhabdomyosarcoma of DBA/2 mice) tumors was tested in an in vivo/in vitro assay, in which tumor-bearing mice were injected intravenously with free or conjugated 3H-BPD and 3 h later light activation of tumor cells was carried out in vitro. Biodistribution studies were carried out using M1 tumor-bearing DBA/2 mice and 3H-BPD either free or conjugated to M-PVA. The results of these studies showed that the conjugation of BPD to M-PVA resulted in the formation of a macromolecular photosensitizer that retained full photosensitizing activity of the photosensitizer molecules and at the same time gained new characteristics, advantageous for photodynamic treatment, especially in vivo. In vitro M-PVA-BPD conjugates were at least as efficient in photosensitization of tumor cells as an equivalent number of free BPD molecules, both in the presence and in the absence of serum. Although the biodistribution was in general comparable to free BPD, the conjugate (1:25) reached slightly higher levels in the blood, kidney, lung and spleen, and lower levels in the liver, brain, skin and muscle in comparison with free BPD.(ABSTRACT TRUNCATED AT 250 WORDS)

A model to describe how a point mutation of the estrogen receptor alters the structure-function relationship of antiestrogens

The antiestrogen tamoxifen [(Z)-1(p-beta-dimethylamino-ethoxyphenyl)-1,2- diphenylbut-1-ene] is an effective anticancer agent for the treatment of hormone responsive breast cancer. Previous studies have demonstrated that a point mutation in the estrogen receptor (ER) resulted in an alteration of the pharmacology of 4-hydroxytamoxifen, the active metabolite of tamoxifen (Jiang et al, Mol Endocrinol 6:2167-2174, 1992). We have extended our studies to evaluate the effect of a point mutation, a Val substitution for Gly at amino acid 400 in the ligand binding domain of ER, on the pharmacology of other antiestrogens in ER stable transfectants derived from the ER-negative breast cancer cell line MDA-MB-231 CL10A. The compounds were tested with or without estradiol-17 beta (E2) for their effects on cell growth in cells expressing the wild type ER (S30) or the mutant ER (ML alpha 2H) or in control antisense ER transfectant AS23 which does not express ER protein. MCF-7 cells, which express the wild type ER, were also used as a control. The growth of AS23 cells was not affected by any of the compounds at a concentration of 1 microM. E2 stimulated the growth of MCF-7 cells but inhibited the growth of ER transfectants S30 and ML alpha 2H. The ML alpha 2H cells were about 10 to 100-fold less sensitive to E2 and antiestrogens than S30 and MCF-7 cells. Keoxifene, an antiestrogen with a high affinity for the ER, maintained antiestrogenic activities in both ER transfectants and MCF-7 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Point mutation of estrogen receptor (ER) in the ligand-binding domain changes the pharmacology of antiestrogens in ER-negative breast cancer cells stably expressing complementary DNAs for ER

The antiestrogen tamoxifen is used in the treatment of hormone-responsive breast cancer. However, therapeutic failure has frequently been observed in both patients and animal models after long term treatment. We have studied the effect of a point mutation that leads to the substitution of Val for Gly at codon 400 in the ligand-binding domain of the estrogen receptor (ER) on estrogenic and antiestrogenic activities of 4-hydroxytamoxifen (4-OHT) and its derivatives. Stable ER transfectants derived from MDA-MB-231 CL10A, an ER-negative breast cancer cell line, have been used in these studies. 4-OHT and its fixed ring derivatives showed more estrogen-like activity in ER transfectants than in MCF-7, an ER-positive breast cancer cell line. In this study, 4-OHT was a partial agonist of cell growth in the transfectant S30 cells, which express the wild-type ER. However, it was a full agonist in the mutant ER transfectant ML alpha 2H, which expressed ER with Val at codon 400. The increased estrogenic activity of 4-OHT in ML alpha 2H cells was not due to the preferential isomerization of trans 4-OHT to cis 4-OHT, since the nonisomerizable fixed ring trans 4-OHT was a partial agonist for cell growth in S30 cells and was a full agonist in ML alpha 2H cells. Transient transfection using a reporter plasmid containing an estrogen response element demonstrated that fixed ring trans 4-OHT had estrogenic activity in ML alpha 2H cells.(ABSTRACT TRUNCATED AT 250 WORDS)

An estrogen receptor positive MCF-7 clone that is resistant to antiestrogens and estradiol

The antiestrogen tamoxifen has been successfully used to control estrogen receptor (ER) and progesterone receptor positive breast cancer. However, the development of antiestrogen resistance is frequently observed in patients following long term treatment. We have studied the development of antiestrogen resistance in vitro and established an antiestrogen resistant variant of MCF-7 cells (clone 5C) after long term culture in estrogen free medium. The growth of clone 5C cells was not altered by either estradiol-17 beta or the antiestrogens 4-hydroxytamoxifen and ICI 164,384. Estrogen-stimulated progesterone receptor and reporter gene expression were markedly reduced in 5C cells compared to wild type MCF-7 cells. Only minor alteration in the levels of ER and no alteration in the affinity of ER for ligand were found in 5C cells. No mutation of ER cDNA in 5C cells was detected by polymerase chain reaction and DNA sequencing. This study demonstrates that change(s) in ER-mediated gene expression rather than the amino acid sequence of the ER itself may be associated with the development of at least one form of antiestrogen resistance.

Growth regulation of estrogen receptor-negative breast cancer cells transfected with complementary DNAs for estrogen receptor

BACKGROUND

The growth of estrogen receptor (ER)-positive breast cancer cells is hormonally regulated, but the majority of breast cancers are ER negative and unresponsive to hormonal therapy.

PURPOSE AND METHODS

To test whether hormonal control over replication can be re-established in ER-negative cells, we transfected ER-negative MDA-MB-231 (clone 10A) cells with sense and antisense constitutive ER expression vectors containing the gene for either wild-type or mutant ER linked to the gene for neomycin resistance aminoglycoside phosphotransferase (neo). A Northern blot analysis was done on total RNA from eight of the 10 transfectant clones produced to detect messenger RNA coding for ER and neo, and a Western blot analysis was done on protein extracted from the cells of one mutant and two wild-type ER sense transfectant clones to determine the molecular weight of the ER in transfectants. Levels of ER in transfectants were measured both by enzyme immunoassay and by ligand-binding methods. To ascertain whether the ER in wild-type and mutant sense transfectants was functional, we tested the effects of 17 beta-estradiol (E2) and/or an antiestrogen, ICI 164,384, on 1) ER-activated gene regulation (by transient transfection of these cells a second time with a reporter plasmid containing an estrogen response element linked to the chloramphenicol acetyl transferase [CAT] gene), 2) induction of progesterone receptor, 3) DNA replication, and 4) cell cycle kinetics.

RESULTS

Messenger RNA coding for ER and for neo was detectable in both sense and antisense transfectant clones. Sense transfectants (both mutant and wild-type) expressed ER protein with a molecular weight similar to that found in ER-positive control cells. By the ligand-binding method high levels of ER were detected in both wild-type and mutant transfectants, although by the enzyme immunoassay method lower levels were detected in mutant transfectants. ER from both wild-type and mutant sense transfectants appeared functional, since E2 stimulated the expression of reporter-linked CAT and of progesterone receptor in these transfectants. E2 inhibited DNA replication in wild-type sense transfectants at a concentration of 10(-10) M and mutant sense transfectants at a concentration of 10(-8) M, and ICI 164,384 blocked this effect.

CONCLUSION

ER-negative breast cancer cells stably transfected with either a mutant or wild-type ER gene regain hormonal responsiveness; however, E2 inhibits rather than stimulates cell growth.

IMPLICATION

Reactivation of quiescent ER may provide a novel therapeutic approach for controlling ER-negative breast cancers.

Photodynamic killing of human squamous cell carcinoma cells using a monoclonal antibody-photosensitizer conjugate

We have developed procedures in which the photosensitizer benzoporphyrin derivative monoacid ring A (BPD) can be covalently linked to carrier molecules of modified polyvinyl alcohol (PVA) to produce water-soluble PVA-BPD conjugates with a molecular mass in the range of 30 kd. These carriers can subsequently be covalently linked to monoclonal antibodies (MoAbs) using heterobifunctional linking agents. We describe here such a conjugate in which the MoAb (5E8) has specificity for a glycoprotein detected on human squamous cell carcinomas of the lung. We provide evidence that the conjugates produced were covalently linked and retained both their photosensitizing and antigen-binding activities. We show further that the MoAb-PVA-BPD conjugate, in the presence of 10% fetal calf serum, exhibited highly enhanced phototoxic killing of the target cell line (A549) over that exhibited by free BPD or a control MoAb-PVA-BPD conjugate. These results demonstrate, therefore, both the selectivity and specificity of this MoAb conjugate.

Inhibition of tamoxifen-stimulated growth of an MCF-7 tumor variant in athymic mice by novel steroidal antiestrogens

This investigation examines the tamoxifen (TAM)-dependent growth in vivo of an MCF-7 tumor variant, MCF-7TAM, previously reported in this journal (M. M. Gottardis and V. C. Jordan, Cancer Res., 48: 5183-5187, 1988). Ovariectomized athymic mice were implanted with 1-mm3 pieces of MCF-7TAM and were treated with Silastic capsules of varying sizes containing TAM to demonstrate dose-dependent growth over a 10-wk experiment. TAM was necessary to maintain tumor growth. Animals whose capsules were removed at 6 wk showed complete tumor stasis after 20 wk of observation. Removal of TAM after 11 wk caused the rate of tumor growth to decrease compared with TAM-treated animals. Tumor areas were significantly different (P less than 0.03) at Wk 20. The growth of TAM-stimulated tumor, MCF-7TAM, was inhibited by the novel steroidal antiestrogens, ICI 164,384 and RU 39,411. TAM-stimulated growth (0.5-cm Silastic capsule) was maintained at control levels by 8 wk of treatment with ICI 164,384 (1 mg s.c. every other day). ICI 164,384 alone had no stimulatory activity. At the same dose, RU 39,411 inhibited TAM-stimulated growth of MCF-7TAM, although not to control levels. RU 39,411 was slightly stimulatory when administered alone. The growth of MCF-7TAM was stimulated by either TAM or 17 beta-estradiol. The antiestrogen, RU 39,411, effectively inhibited estradiol-stimulated tumor growth. Overall, these studies confirm and extend the previous observation on TAM-stimulated growth of breast cancer cells in vivo and demonstrate the possibility of developing novel antiestrogens to prevent this form of drug resistance should it occur in the clinic.

Protective murine monoclonal antibodies to tetanus toxin

Monoclonal antibodies against tetanus toxin were generated by fusion of mouse NS-1 myeloma cells with spleen cells from BALB/C mice immunized with tetanus toxoid. Twenty seven hybridomas against tetanus toxin were obtained. Six hybridoma clones, designated as 1A6B12, 1H7D9, 3A8G9, 3A9F2, 3F9H9, 4A6D11 were selected for further studies. All of them were IgG1, k chain and bound specifically to tetanus toxin and toxoid. All six clones were injected intraperitoneally into pristane-primed BALB/C mice. Antibodies with titer up to 10(6) were obtained in the ascites. Results obtained from in vivo neutralization test showed that 1A6B12, 3A8G9, 3F9H9, 4A6D11 mAbs did have neutralizing activities against tetanus toxin. Monoclonal antibody 4A6D11 had the strongest neutralizing activity. 4A6D11 were purified from ascites by DEAE-52 ion exchange chromatography. Comparing to U.S.A. standard antitetanus toxin antiserum, 50 micrograms purified 4A6D11 mAb had 1 international unit neutralizing activity. The purified 4A6D11 mAb was also coupled to cyanogen bromide-activated sepharose to make an affinity column. Pure tetanus toxin can be obtained by passing crude tetanus toxin through this column and eluting the adsorbed toxin with 4M urea. Large scale purified tetanus toxin could be obtained by this method.

A cytotoxic monoclonal antibody produced from a human urinary bladder carcinoma cell line (TSGH-8301)

A mouse monoclonal antibody, designated 1G3.10, directed against a human urinary bladder cancer cell line TSGH-8301 was generated using the conventional hybridoma technique. It was of the IgG3 subclass with a restricted specificity to bladder cancer and several epithelial cancers, as detected on a panel of various cell lines and tissues by radioimmunoassay and indirect immunofluorescence methods. It also exhibited a strong binding activity to human group A red blood cells, as demonstrated in hemagglutination and absorption tests. Radioimmunoprecipitation and thin-layer chromatography revealed that the antigens recognized by the antibody are a mixture of glycopeptides (M.W. 30, 54, and 108 KD) and glycolipid (retardation factor 0.67-0.83). From a fluorescence activated cell sorter (FACS) study, direct killing of tumor cells by the antibody at a concentration of more than 10 micrograms/ml was observed. This antibody could also mediate both antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) in vitro when tested in a 4-hr 51Cr-release test. These results suggest that the monoclonal antibody 1G3.10 may provide an agent for further immunodiagnosis and the treatment of human bladder cancer.

Reappearance of persistent normal sinus rhythm in a patient with the sick sinus syndrome following cardiac pacing for 10.5 years

A patient with symptomatic sick sinus syndrome which manifested as a brady-tachy syndrome, was admitted to our institute in 1969. Following cardiac pacing for 10.5 years, the brady-tachy syndrome disappeared and normal sinus rhythm was restored. Her stable normal sinus rate has persisted up to the present, 2.5 years after termination of pacing.

Electrophysiological studies on the nucleus isthmi of the lizards Gekko gekko and Shinisaurus crocodilurus

This report studies visual responses of the isthmic units in Gekko gekko and Shinisaurus crocodilurus using extracellular recording and cobalt sulfide marking techniques. Our results indicate that: (i) the nucleus isthmi pars magnocellularis (Imc) is a visual center; (ii) there are luxotonic units in Imc; (iii) Imc units respond vigorously to moving contrast targets, of which 35% units burst only at the moment when targets are moving into and out of their receptive fields, none react to either tactile or auditory stimulation; (iv) there exist binocular units in Imc; and (v) visual field is topographically projected onto Imc.

Neuroanatomy and electrophysiology of the lacertilian nucleus isthmi

Horseradish peroxidase (HRP) tracings showed a bidirectional connection between the optic tectum (OT) and the ipsilateral nucleus isthmi (NI) pars magnocellularis (Imc) in nocturnal Gekko gekko and diurnal Shinisaurus crocodilurus. We found that, in addition to a direct neuronal pathway, there is an indirect pathway from OT to Imc via the nucleus profundus mesencephali (NPM). The morphology of cells in OT, NPM and NI was studied. Visual units extracellularly recorded from NI were located within Imc based on cobalt sulphide markings. They responded to moving contrast targets, without reacting to tactile and auditory stimulation. HRP and Golgi-Cox studies showed that Imc is a nucleus independent of its parvocellular partner, Ipc.