Characterization of four new gastric cancer cell lines

Heterogeneous Cellular Response of Primary and Metastatic Human Gastric Adenocarcinoma Cell Lines to Magnoflorine and Its Additive Interaction with Docetaxel

Gastric cancer is the most common cancer and remains the leading cause of cancer death worldwide. In this study, the anticancer action of magnoflorine isolated via counter-current chromatography from the methanolic extract of Berberis vulgaris root against gastric cancer in models of primary ACC-201 and AGS and metastatic MKN-74 and NCI-N87 cell lines was analyzed. Cell viability and proliferation were tested through the use of MTT and BrdU tests, respectively. Cell cycle progression and apoptosis were evaluated using flow cytometry. The interaction of magnoflorine and docetaxel has been examined through isobolographic analysis. Moreover, potential toxicity was verified in zebrafish in an in vivo model. Gastric cancer cell lines revealed different responses to magnoflorine treatment with regard to viability/proliferation, apoptosis induction and cell cycle inhibition without any undesirable changes in the development of larval zebrafish at the tested concentrations. What is more, magnoflorine in combination with docetaxel produced an additive pharmacological interaction in all studied gastric cancer cell lines, which may suggest a complementary mechanism of action of both compounds. Taken together, these findings provide a foundation for the possibility of magnoflorine as a potential therapeutic approach for gastric cancer and merits further investigation, which may pave the way for clinical uses of magnoflorine.

The CAIX inhibitor SLC-0111 exerts anti-cancer activity on gastric cancer cell lines and resensitizes resistant cells to 5-Fluorouracil, taxane-derived, and platinum-based drugs

Gastric cancer (GC) is the fifth most frequent malignancy and the fourth leading cause of worldwide cancer-related death. Despite the usage of multimodal perioperative chemotherapy (pCT), GC progressively gains chemoresistance, thereby, the identification of suitable targets to overcome drug resistance is fundamental. Amongst the potential biomarkers, carbonic anhydrase IX (CAIX) - associated with a poor prognosis of several solid cancers - has gained the most attention. In a cohort of GC patients who received perioperative FLOT (i.e., Leucovorin, 5-Fluouracil, Docetaxel, and Oxaliplatin) or FOLFOX (i.e., Leucovorin, 5-Fluouracil, and Oxaliplatin), non-responder patients showed an increased expression of tumor CAIX compared to responder group. Moreover, GC cell lines induced to be resistant to 5-Fluouracil, Paclitaxel, Cisplatin, or the combination of 5-Fluorouracil, Oxaliplatin, and Docetaxel, overexpressed CAIX compared to the control. Accordingly, CAIX-high-expressing GC cells showed increased therapy resistance compared to low-expressing cells. Notably, SLC0111 significantly improved the therapy response of both wild-type and resistant GC cells. Overall, these data suggest a correlation between CAIX and GC drug resistance highlighting the potential of SLC-0111 in re-sensitizing GC cells to pCT.

Antiproliferative and antimetabolic effects behind the anticancer property of fermented wheat germ extract

BACKGROUND

Fermented wheat germ extract (FWGE) sold under the trade name Avemar exhibits anticancer activity in vitro and in vivo. Its mechanisms of action are divided into antiproliferative and antimetabolic effects. Its influcence on cancer cell metabolism needs further investigation. One objective of this study, therefore, was to further elucidate the antimetabolic action of FWGE. The anticancer compound 2,6-dimethoxy-1,4-benzoquinone (DMBQ) is the major bioactive compound in FWGE and is probably responsible for its anticancer activity. The second objective of this study was to compare the antiproliferative properties in vitro of FWGE and the DMBQ compound.

METHODS

The IC50 values of FWGE were determined for nine human cancer cell lines after 24 h of culture. The DMBQ compound was used at a concentration of 24 μmol/l, which is equal to the molar concentration of DMBQ in FWGE. Cell viability, cell cycle, cellular redox state, glucose consumption, lactic acid production, cellular ATP levels, and the NADH/NAD(+) ratio were measured.

RESULTS

The mean IC50 value of FWGE for the nine human cancer cell lines tested was 10 mg/ml. Both FWGE (10 mg/ml) and the DMBQ compound (24 μmol/l) induced massive cell damage within 24 h after starting treatment, with changes in the cellular redox state secondary to formation of intracellular reactive oxygen species. Unlike the DMBQ compound, which was only cytotoxic, FWGE exhibited cytostatic and growth delay effects in addition to cytotoxicity. Both cytostatic and growth delay effects were linked to impaired glucose utilization which influenced the cell cycle, cellular ATP levels, and the NADH/NAD(+) ratio. The growth delay effect in response to FWGE treatment led to induction of autophagy.

CONCLUSIONS

FWGE and the DMBQ compound both induced oxidative stress-promoted cytotoxicity. In addition, FWGE exhibited cytostatic and growth delay effects associated with impaired glucose utilization which led to autophagy, a possible previously unknown mechanism behind the influence of FWGE on cancer cell metabolism.

Long-term High Fat Ketogenic Diet Promotes Renal Tumor Growth in a Rat Model of Tuberous Sclerosis

Nutritional imbalance underlies many disease processes but can be very beneficial in certain cases; for instance, the antiepileptic action of a high fat and low carbohydrate ketogenic diet. Besides this therapeutic feature it is not clear how this abundant fat supply may affect homeostasis, leading to side effects. A ketogenic diet is used as anti-seizure therapy i.a. in tuberous sclerosis patients, but its impact on concomitant tumor growth is not known. To examine this we have evaluated the growth of renal lesions in Eker rats (Tsc2+/−) subjected to a ketogenic diet for 4, 6 and 8 months. In spite of existing opinions about the anticancer actions of a ketogenic diet, we have shown that this anti-seizure therapy, especially in its long term usage, leads to excessive tumor growth. Prolonged feeding of a ketogenic diet promotes the growth of renal tumors by recruiting ERK1/2 and mTOR which are associated with the accumulation of oleic acid and the overproduction of growth hormone. Simultaneously, we observed that Nrf2, p53 and 8-oxoguanine glycosylase α dependent antitumor mechanisms were launched by the ketogenic diet. However, the pro-cancerous mechanisms finally took the ascendency by boosting tumor growth.

TKTL1 expression in human malign and benign cell lines

Background

Overexpression of transketolase-like 1 protein TKTL1 in cancer cells has been reported to correlate with enhanced glycolysis and lactic acid production. Furthermore, enhanced TKTL1 expression was put into context with resistance to chemotherapy and ionizing radiation. Here, a panel of human malign and benign cells, which cover a broad range of chemotherapy and radiation resistance as well as reliance on glucose metabolism, was analyzed in vitro for TKTL1 expression.

Methods

17 malign and three benign cell lines were characterized according to their expression of TKTL1 on the protein level with three commercially available anti-TKTL1 antibodies utilizing immunohistochemistry and Western blot, as well as on mRNA level with three published primer pairs for RT-qPCR. Furthermore, sensitivities to paclitaxel, cisplatin and ionizing radiation were assessed in cell survival assays. Glucose consumption and lactate production were quantified as surrogates for the “Warburg effect”.

Results

Considerable amounts of tktl1 mRNA and TKTL1 protein were detected only upon stable transfection of the human embryonic kidney cell line HEK293 with an expression plasmid for human TKTL1. Beyond that, weak expression of endogenous tktl1 mRNA was measured in the cell lines JAR and U251. Western blot analysis of JAR and U251 cells did not detect TKTL1 at the expected size of 65 kDa with all three antibodies specific for TKTL1 protein and immunohistochemical staining was observed with antibody JFC12T10 only. All other cell lines tested here revealed expression of tktl1 mRNA below detection limits and were negative for TKTL1 protein. However, in all cell lines including TKTL1-negative HEK293-control cells, antibody JFC12T10 detected multiple proteins with different molecular weights. Importantly, JAR and U251 did neither demonstrate an outstanding production of lactic acid nor increased resistance against chemotherapeutics or to ionizing radiation, respectively.

Conclusion

Using RT-qPCR and three different antibodies we observed only exceptional occurrence of TKTL1 in a panel of malignant human cell lines in vitro. The presence of TKTL1 was unrelated to either the rate of glucose consumption/lactic acid production or resistance against chemo- and radiotherapy.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-15-2) contains supplementary material, which is available to authorized users.

Targeting Chk2 improves gastric cancer chemotherapy by impairing DNA damage repair

Our results demonstrate that the addition of cisplatin after paclitaxel-induced mitotic arrest was more effective than individual treatment on gastric adenocarcinoma cells (MKN45). However, the treatment did not induce benefits in cells derived from lymph node metastasis (ST2957). Time-lapse microscopy revealed that cell death was caused by mitotic catastrophe and apoptosis induction, as the use of the caspase inhibitor z-VAD-fmk decreased cell death. We propose that the molecular mechanism mediating this cell fate is a slippage suffered by these cells, given that our Western blot (WB) analysis revealed premature cyclin B degradation. This resulted in the cell exiting from mitosis without undergoing DNA damage repair, as demonstrated by the strong phosphorylation of H2AX. A comet assay indicated that DNA repair was impaired, and Western blotting showed that the Chk2 protein was degraded after sequential treatment (paclitaxel-cisplatin). Based on these results, the modulation of cell death during mitosis may be an effective strategy for gastric cancer therapy.

Triggering receptor expressed on myeloid cells-1 (TREM-1) expression on gastric epithelium: implication for a role of TREM-1 in Helicobacter pylori infection

In Helicobacter pylori gastritis gastric epithelium plays a central role in the innate immunity to H. pylori. However, epithelial receptors interacting with H. pylori have been poorly characterized so far. Recently a new triggering receptor expressed on myeloid cells-1 (TREM-1) has been identified on human neutrophils and monocytes. On these cells TREM-1 triggers innate immunity by stimulating the secretion of interleukin (IL)-8 and tumour necrosis factor (TNF)-alpha and thus amplifies bacterial-induced inflammation. In this study expression and function of TREM-1 in gastric epithelium exposed to H. pylori has been investigated. TREM-1 mRNA and protein were expressed on gastric epithelial cell lines as demonstrated by reverse transcription-polymerase chain reaction (RT-PCR) and fluorescence activated cell sorter analysis. Gastric epithelial TREM-1 expression was up-regulated directly by H. pylori and was independent of epithelial IL-8 induced by H. pylori. Immunohistochemistry and tissue RT-PCR demonstrated significantly stronger TREM-1 expression in H. pylori gastritis compared with the non-inflamed gastric mucosa supporting in vivo that epithelial TREM-1 is up-regulated during H. pylori infection. Stimulation of gastric epithelial TREM-1 receptor resulted in IL-8 up-regulation on mRNA and protein level, as shown by real-time PCR and immunoassay. This is the first study localizing TREM-1 on gastric epithelium. Functional data suggest that TREM-1 expressed on gastric epithelium amplifies inflammation of the underlying gastric mucosa by up-regulation of IL-8.

Growth of human gastric cancer cells in nude mice is delayed by a ketogenic diet supplemented with omega-3 fatty acids and medium-chain triglycerides

BACKGROUND

Among the most prominent metabolic alterations in cancer cells are the increase in glucose consumption and the conversion of glucose to lactic acid via the reduction of pyruvate even in the presence of oxygen. This phenomenon, known as aerobic glycolysis or the Warburg effect, may provide a rationale for therapeutic strategies that inhibit tumour growth by administration of a ketogenic diet with average protein but low in carbohydrates and high in fat enriched with omega-3 fatty acids and medium-chain triglycerides (MCT).

METHODS

Twenty-four female NMRI nude mice were injected subcutaneously with tumour cells of the gastric adenocarcinoma cell line 23132/87. The animals were then randomly split into two feeding groups and fed either a ketogenic diet (KD group; n = 12) or a standard diet (SD group; n = 12) ad libitum. Experiments were ended upon attainment of the target tumor volume of 600 mm3 to 700 mm3. The two diets were compared based on tumour growth and survival time (interval between tumour cell injection and attainment of target tumour volume).

RESULTS

The ketogenic diet was well accepted by the KD mice. The tumour growth in the KD group was significantly delayed compared to that in the SD group. Tumours in the KD group reached the target tumour volume at 34.2 +/- 8.5 days versus only 23.3 +/- 3.9 days in the SD group. After day 20, tumours in the KD group grew faster although the differences in mean tumour growth continued significantly. Importantly, they revealed significantly larger necrotic areas than tumours of the SD group and the areas with vital tumour cells appear to have had fewer vessels than tumours of the SD group. Viable tumour cells in the border zone surrounding the necrotic areas of tumours of both groups exhibited a glycolytic phenotype with expression of glucose transporter-1 and transketolase-like 1 enzyme.

CONCLUSION

Application of an unrestricted ketogenic diet enriched with omega-3 fatty acids and MCT delayed tumour growth in a mouse xenograft model. Further studies are needed to address the impact of this diet on other tumour-relevant functions such as invasive growth and metastasis.

Net1 and Myeov: computationally identified mediators of gastric cancer

Gastric adenocarcinoma (GA) is a significant cause of mortality worldwide. The molecular mechanisms of GA remain poorly characterised. Our aim was to characterise the functional activity of the computationally identified genes, NET 1 and MYEOV in GA. Digital Differential Display was used to identify genes altered expression in GA-derived EST libraries. mRNA levels of a subset of genes were quantitated by qPCR in a panel of cell lines and tumour tissue. The effect of pro- and anti-inflammatory stimuli on gene expression was investigated. Cell proliferation and invasion were measured using in an in-vitro GA model following inhibition of expression using siRNA. In all, 23 genes not previously reported in association with GA were identified. Two genes, Net1 and Myeov, were selected for further analysis and increased expression was detected in GA tissue compared to paired normal tissue using quantitative PCR. siRNA-mediated downregulation of Net1 and Myeov resulted in decreased proliferation and invasion of gastric cancer cells in vitro. These functional studies highlight a putative role for NET1 and Myeov in the development and progression of gastric cancer. These genes may provide important targets for intervention in GA, evidenced by their role in promoting invasion and proliferation, key phenotypic hallmarks of cancer cells.

Conventional cytogenetic characterization of a new cell line, ACP01, established from a primary human gastric tumor

Gastric cancer is the second most frequent type of neoplasia and also the second most important cause of death in the world. Virtually all the established cell lines of gastric neoplasia were developed in Asian countries, and western countries have contributed very little to this area. In the present study we describe the establishment of the cell line ACP01 and characterize it cytogenetically by means of in vitro immortalization. Cells were transformed from an intestinal-type gastric adenocarcinoma (T4N2M0) originating from a 48-year-old male patient. This is the first gastric adenocarcinoma cell line established in Brazil. The most powerful application of the cell line ACP01 is in the assessment of cytotoxicity. Solid tumor cell lines from different origins have been treated with several conventional and investigational anticancer drugs. The ACP01 cell line is triploid, grows as a single, non-organized layer, similar to fibroblasts, with focus formation, heterogeneous division, and a cell cycle of approximately 40 h. Chromosome 8 trisomy, present in 60% of the cells, was the most frequent cytogenetic alteration. These data lead us to propose a multifactorial triggering of gastric cancer which evolves over multiple stages involving progressive genetic changes and clonal expansion.

Histone-deacetylase inhibitors induce the cathelicidin LL-37 in gastrointestinal cells

Histone-deacetylase (HDAC) -inhibitors enhance acetylation of core proteins and this is linked to formation of transcriptionally active chromatin in various cells. In this study, the effect of HDAC inhibitors (butyrate, trichostatin A (TSA)) on the expression of the cathelicidin LL-37 in colon, gastric and hepatocellular cells was investigated.

METHODS

LL-37 expression was assessed in colon, gastric and hepatocellular cancer cells after treatment with HDAC-inhibitors. In parallel, histone H4 and HMGN2, a non-histone protein, acetylation was evaluated. In addition, the intracellular signalling pathway MEK-ERK was explored.

RESULTS

In contrast to normal colon epithelial cells, gastrointestinal cancer cells lacked LL-37 expression. LL-37 was induced following treatment with HDAC-inhibitors in all investigated cell lines. This induction was time-dependent in butyrate-treated cells while TSA exerted a transient effect. Induction of LL-37 by butyrate was paralleled by acetylation of the histone H4 and the non-histone HMGN2. Again, TSA resulted in transient acetylation. Furthermore, inhibition of MEK-ERK blocked HDAC inhibitor-induced LL-37 expression in colonic and gastric cells.

CONCLUSIONS

We have previously shown that butyrate induces LL-37 in colon epithelial cells. In the present study, we demonstrate that cathelicidin expression is modulated by HDAC-inhibitors in various gastrointestinal cells including gastric and hepatocellular cells. This is paralleled by changes in the acetylation of distinct core proteins suggesting a common regulatory mechanism of cathelicidin LL-37 regulation in these cells.

Detection of disseminated tumor cells in nude mice with human gastric cancer

Disseminated tumor cells (DTC) are a potential contributor to relapse of cancer. In the present study we developed a model for induction of disseminated tumor cells in nude mice, which can aid in the search for therapeutic approaches as well as improve our understanding of metastasizing gastric cancer. To detect DTC in blood and bone marrow we established a modified animal model of orthotopic transplantation. Two groups of nude mice were used for xenotransplantation of gastric cancer specimens. In group I tumor specimens originating from a gastric adenocarcinoma cell line were transplanted onto the stomach; in group II they were transplanted subcutaneously into both axillaries. Tumor growth, metastases and presence of DTC were compared in both groups. For detection of DTC a nested reverse transcriptase polymerase chain reaction (RT-PCR) for human cytokeratin (CK)-20 was performed on blood and bone marrow of all mice. Tumor growth occurred in both groups (9/10 animals in group I, 10/10 in group II) within 14 weeks. Only animals in group I developed local invasive tumor growth, stenosis of the stomach and distant metastases. Tumors in animals of group II grew with local displacement only and developed no metastases. There were no signals of CK-20 detected in the blood in both groups. In group I, 5 of 9 animals had positive signals of human CK-20 in their bone marrow as a sign of DTC. In group II no DTC were detected in bone marrow. We conclude that orthotopic transplantation is a prerequisite for the development of DTC and metastasizing tumor growth in this modified gastric cancer model.

Transcription of sonic hedgehog, a potential factor for gastric morphogenesis and gastric mucosa maintenance, is up-regulated in acidic conditions

Gastric body mucosa atrophy predisposes one to gastric cancer. Disturbances in the gastric differentiation process might play a role in the evolution of gastric atrophy. Sonic hedgehog (Shh) has recently been implicated as a crucial factor in gastric organogenesis and gland differentiation. In this study we investigated the expression of key factors in the Shh pathway, namely Shh and its receptor Patched (Ptc), in normal and pathologic stomach mucosa. Furthermore, the potential role of pH for Shh dysregulation was analyzed. Ten gastric biopsy specimens each from normal gastric mucosa, chronic nonatrophic gastritis, atrophic gastritis, and gastric cancer were included. Expression of Shh and Ptc was analyzed by immunohistochemistry. In normal body mucosa and in nonatrophic body gastritis, Shh was strongly expressed in parietal cells. Ptc was also expressed in gastric chief cells. Shh expression was almost completely lost in atrophic gastritis and in gastric cancer and absent in intestinal metaplasia. Ptc was markedly reduced in atrophy and only weakly positive in intestinal metaplasia and gastric cancer. In in vitro experiments, gastric cancer cell line 23132 was found positive for Shh. In long-term culture as well as in culture conditions with low pH, transcription of Shh in 23132 was significantly increased in quantitative reverse transcription PCR analyses. We concluded that the decreased expression of the Shh pathway in atrophic gastritis and gastric cancer might reflect altered differentiation processes within the gastric unit and contributes to the development of gastric atrophy. The increase of gastric pH might play a role in the development of gastric mucosa atrophy via reduction of Shh transcription.

CD97, but not its closely related EGF-TM7 family member EMR2, is expressed on gastric, pancreatic, and esophageal carcinomas

CD97 expression is related closely to the dedifferentiation and tumor stage in thyroid carcinomas. We systematically examined the role of CD97 and its closest relative, EMR2, in normal and malignant gastric, esophageal, and pancreatic tissue. The normal tissues were EMR2-, whereas CD97 was expressed slightly in the parietal cells of gastric mucosa and in exocrine pancreatic cells. Interestingly, intralobular and interlobular pancreatic ducts were CD97+. All tumors were EMR2-. CD97 was expressed by 44 of 50 gastric, 14 of 18 pancreatic, and 10 of 13 esophageal carcinomas. Of the 44 gastric cancers, 27 showed disseminated or scattered tumor cells at the invasion front with stronger CD97 expression than tumor cells located in solid tumor formations. There was no correlation between CD97 levels in the tumors or soluble CD97 in the serum samples and the clinicopathologic features of the patients. Taken together, significant numbers of gastric, esophageal, and pancreatic carcinomas are CD97+, whereas its homolog, EMR2, does not have any role in such tumors.

Loss of heterozygosity and promoter methylation, but not mutation, may underlie loss of TFF1 in gastric carcinoma

It has been advanced that the trefoil factor (TFF) 1 gene is a candidate tumor-suppressor gene and may be involved in the development and/or progression of human gastric cancer. We aimed to clarify the putative role of TFF1 in gastric carcinogenesis. Ninety gastric carcinomas and eight gastric carcinoma-derived cell lines were screened for TFF1 mutations; subsets of the primary tumors and of the cell lines were subjected to loss of heterozygosity (LOH), immunohistochemistry, and promoter methylation analyses. TFF1 mutations were not detected in any of 90 gastric carcinomas. Eight (28%) of 28 informative cases displayed LOH at the TFF1 locus and absence of TFF1 staining by immunohistochemistry. These results indicate a frequent loss of TFF1 expression in gastric carcinomas through a mutation-independent mechanism. Extensive TFF1 promoter methylation was observed in nonexpressing gastric carcinoma-derived cell lines and tissues. Expressing cell lines, as well as normal gastric mucosa, presented little or no methylation of the promoter. Gastric carcinoma DNA presented de novo methylation of the promoter. These results point to the involvement of promoter methylation in the shutting down of TFF1. We conclude that TFF1 point mutations seem to be a rare event in gastric carcinogenesis. The loss of expression of TFF1 in a proportion of gastric carcinomas may be explained by LOH and methylation of the TFF1 promoter region. Our results further support the role of TFF1 inactivation in gastric carcinogenesis, in agreement with the results obtained in the Tff1-knockout mice model.

Immunocytochemical analysis of cell lines derived from solid tumors

Antibodies recognizing tissue-specific antigens are widely used to identify the histological origin of tumors. Here we tested the fidelity of selected tissue markers on all 167 solid tumor-derived continuous cell lines in the DSMZ cell lines bank. Most lines had an intermediate filament content consistent with the tumor type from which they were derived. Thus, 93% of all carcinoma cell lines expressed keratin filaments. With certain antibodies, some subclassification was possible. For example, the CK7 keratin 7 antibody can differentiate between colon and pancreas-derived carcinoma cell lines. Cell lines derived from non-carcinomas, in general, did not express keratin but were vimentin-positive. Four of 10 glioma/astrocytoma cell lines expressed GFAP, five of six neuroblastoma cell lines expressed neurofilaments, and the TE-671 rhabdomyosarcoma cell line expressed desmin. When other tissue markers were tested, 12/16 melanoma-derived cell lines expressed HMB-45, while PSA, CA125, and thyroglobulin were less useful. These results demonstrate that cell lines retain some but not all markers typical of the original tumor type and identify certain markers useful in characterizing the histological origin of cell lines. Our data question the identity of some cell lines submitted to the bank in the past. The immunoprofiles of 167 solid tumor-derived and 131 hematopoetic cell lines can be found at www.dsmz.de.

Regulation of the new coexpressed CD55 (decay-accelerating factor) receptor on stomach carcinoma cells involved in antibody SC-1-induced apoptosis

The human monoclonal antibody SC-1 was isolated from a patient with a diffuse-type adenocarcinoma of the stomach using somatic cell hybridization. The immunoglobulin (Ig)M antibody reacts specifically with diffuse- (70%) and intestinal-type (25%) gastric adenocarcinoma and induces apoptosis in vitro and in vivo. When used in clinical trials with stomach carcinoma patients, significant apoptotic and regressive effects in primary tumors have been observed with the antibody SC-1. The SC-1 receptor is a new 82 kd membrane-bound isoform of glycosylphosphatidylinositol (GPI)-linked CD55 (decay-accelerating factor, DAF). CD55 is known to protect cells from lysis through autologous complement and is coexpressed with the ubiquitously distributed 70 kd isoform. The SC-1-specific CD55 isoform is up-regulated shortly after antibody binding, followed by an internalization of the antibody/receptor-complex, whereas the membranous expression of wild-type CD55 remains unchanged. The apoptotic process is marked by cleavage of cytokeratin 18, indicating the involvement of caspase-6 in the apoptotic process. In contrast to other apoptotic pathways, a cleavage of poly(ADP-ribose)polymerase (PARP) is not observed. The expression of the cell-cycle regulator c-myc becomes up-regulated, whereas expression of topoisomerase IIalpha is down-regulated. Induction of apoptosis leads to an increase in the internal Ca(2+) concentration, which is not necessary for the apoptotic process but for the transport of newly synthesized SC-1-specific CD55 isoform to the membrane.

Transcription of cytokeratins 8, 18, and 19 in bone marrow and limited expression of cytokeratins 7 and 20 by carcinoma cells: inherent limitations for RT-PCR in the detection of isolated tumor cells

The suitability of "real-time" quantitative reverse transcriptase polymerase chain reaction (RT-PCR) for the detection of isolated carcinoma cells in bone marrow was investigated by evaluating the expression of cytokeratin (CK)7, CK8, CK18, CK19, and CK20 in 17 gastrointestinal cancer cell lines, 64 control bone marrow specimens from noncancer patients, and 30 bone marrow specimens from patients with gastric or colorectal cancer. RT-PCR products for CK8 and CK18 were detected in all cancer cell lines, but only 16, 5, and 11 cell lines provided evidence for CK19, CK7, and CK20 transcription. Variable numbers of bone marrow specimens from noncancer patients demonstrated background transcription of CK8 (78.1%), CK18 (95.3%), CK19 (35.9%), CK20 (29.6%), and CK7 (16.7%). Maximal background transcription for CK8, CK18, and CK19 ranged from 52.2 to 56.1 copies/10(3) copies glyceraldehyde-3-phosphate dehydrogenase (GAPDH), the corresponding values of 0.06 and 0.76 copies for CK7 and CK20 being distinctly lower. When maximal background values were used as a threshold value to define positivity in tumor cell dilution experiments, sensitivity levels of one tumor cell in 10(4) bone marrow cells were determined for CK7 and CK20 RT-PCR assays. Maximal background expression values of the different CKs as obtained in the control series were exceeded once (CK20), twice (CK18 and CK19), and 18 times (CK7) in bone marrow specimens from cancer patients, with none of these specimens exceeding the maximal background expression value of CK8. We conclude that RT-PCR for CK8, CK18, and CK19 cannot be recommended for the detection of isolated tumor cells in bone marrow of cancer patients. On the other side, the limited number of gastric and colorectal cancer cell lines expressing CK7 and CK20 indicates that assay sensitivity for these CKs might be limited because of their selective expression by carcinoma cells.

Differential expression of apoptosis receptors on diffuse and intestinal type stomach carcinoma

BACKGROUND

Intestinal and diffuse adenocarcinomas of the stomach differ in phenotypic properties, morphology, and growth behavior. Apoptosis (programmed cell death) is induced via specific cell-surface receptors (SC-1, Fas/APO-1/CD95) and coregulated by intracellular molecules (bcl-2, p53, etc.); the success of apoptotic processes is dependent on the expression of these signals. Differences in the expression of specific apoptosis receptors and intracellular-related signals might help to explain the molecular pathogenesis of these two types of stomach adenocarcinoma.

METHODS

Immunohistochemical studies were performed on frozen sections of tumor tissue using human monoclonal antibody SC-1 and murine monoclonal antibodies Fas and p53, followed by peroxidase-coupled second antibodies. To determine binding of SC-1 and Fas antibodies to stomach carcinoma cells on the molecular level, Western blot analysis was performed with cell extract preparations from stomach carcinoma cells. To investigate functional apoptotic activity, MTT assays were performed with SC-1 and Fas antibodies on stomach carcinoma cells.

RESULTS

On frozen sections intestinal type stomach carcinoma cells demonstrate little or no expression of SC-1 and Fas receptors (4 of 17 and 1 of 17, respectively). Diffuse type stomach carcinoma cells show just the opposite: greater than 50% express SC-1 and Fas at a high level (15 of 30 and 22 of 30, respectively). Normal stomach mucosa is negative with both antibodies. Expression of p53 is positively correlated with intestinal type carcinomas (11 of 17) but not with diffuse type (5 of 30). In functional studies MTT assay) the SC-1 and Fas antibodies react with stomach carcinoma by inducing apoptosis and inhibiting growth. On Western blot analysis of extracts from stomach carcinoma cells, SC-1 detects a protein of 50 kilodalton (kD) and Fas proteins of approximately 30, 45, and 60 kD.

CONCLUSIONS

These data indicate that gastric carcinoma cells of the intestinal and diffuse type differ in their expression of the apoptotic receptors SC-1 and Fas and the tumor suppressor gene product p53. These new data on phenotypic differences support the hypothesis that these two types of stomach carcinoma do not only differ in morphology, growth pattern, and risk factors but also in genetic pathways.

Differential expression of apoptosis receptors on diffuse and intestinal type stomach carcinoma

BACKGROUND

Intestinal and diffuse adenocarcinomas of the stomach differ in phenotypic properties, morphology, and growth behavior. Apoptosis (programmed cell death) is induced via specific cell-surface receptors (SC-1, Fas/APO-1/CD95) and coregulated by intracellular molecules (bcl-2, p53, etc.); the success of apoptotic processes is dependent on the expression of these signals. Differences in the expression of specific apoptosis receptors and intracellular-related signals might help to explain the molecular pathogenesis of these two types of stomach adenocarcinoma.

METHODS

Immunohistochemical studies were performed on frozen sections of tumor tissue using human monoclonal antibody SC-1 and murine monoclonal antibodies Fas and p53, followed by peroxidase-coupled second antibodies. To determine binding of SC-1 and Fas antibodies to stomach carcinoma cells on the molecular level, Western blot analysis was performed with cell extract preparations from stomach carcinoma cells. To investigate functional apoptotic activity, MTT assays were performed with SC-1 and Fas antibodies on stomach carcinoma cells.

RESULTS

On frozen sections intestinal type stomach carcinoma cells demonstrate little or no expression of SC-1 and Fas receptors (4 of 17 and 1 of 17, respectively). Diffuse type stomach carcinoma cells show just the opposite: greater than 50% express SC-1 and Fas at a high level (15 of 30 and 22 of 30, respectively). Normal stomach mucosa is negative with both antibodies. Expression of p53 is positively correlated with intestinal type carcinomas (11 of 17) but not with diffuse type (5 of 30). In functional studies MTT assay) the SC-1 and Fas antibodies react with stomach carcinoma by inducing apoptosis and inhibiting growth. On Western blot analysis of extracts from stomach carcinoma cells, SC-1 detects a protein of 50 kilodalton (kD) and Fas proteins of approximately 30, 45, and 60 kD.

CONCLUSIONS

These data indicate that gastric carcinoma cells of the intestinal and diffuse type differ in their expression of the apoptotic receptors SC-1 and Fas and the tumor suppressor gene product p53. These new data on phenotypic differences support the hypothesis that these two types of stomach carcinoma do not only differ in morphology, growth pattern, and risk factors but also in genetic pathways.

Apoptosis of stomach carcinoma cells induced by a human monoclonal antibody

BACKGROUND

Although stomach carcinoma is estimated to be one of the most frequent cancers worldwide, still little is known about the immunity of patients with stomach cancer. Humoral tumor immunity has been studied by isolating B cells of patients with cancer to characterize the activity of such antibodies on tumor cells. Apoptosis, programmed cell death, explains the suicide of cells by fragmentation of DNA, cell shrinkage and dilation of endoplasmatic reticulum, followed by cell fragmentation and formation of membrane vesicles called apoptotic bodies. Apoptosis serves to remove unwanted, damaged, or dangerous, e.g., precancerous cells.

METHODS

The human monoclonal antibody SC-1 was isolated from a patient with a signet ring cell carcinoma of the stomach by fusion of spleen lymphocytes to the heteromyeloma SPM4-0. The antibody was tested for growth-inhibiting effects in vitro in soft agar assays, in 3-H thymidine uptake experiments, and in a mitochondrial enzymatic activity assay. In vivo intraperitoneal tumor growth was investigated in nu-nu mice.

RESULTS

The immunoglobulin M (lambda) antibody identifies a molecule with a molecular weight of approximately 49 kilodaltons in stomach carcinoma cells. No reactivity was observed with carcinomas of other origins, melanomas, lymphomas, or normal tissue. When tested in vitro, the antibody inhibited tumor cell growth in cell culture and soft agar. In vivo growth of stomach carcinoma cells in nu-nu mice was reduced when the antibody was injected after the tumor cells. Ultrastructural and functional studies revealed that the SC-1 antibody induced apoptosis of tumor cells.

CONCLUSION

The human monoclonal antibody SC-1 described here inhibited growth of stomach carcinoma cells in vitro and in vivo by inducing apoptosis, and may, therefore, be valuable for treating patients with stomach carcinoma.

Human monoclonal antibodies from stomach carcinoma patients react with Helicobacter pylori and stimulate stomach cancer cells in vitro

BACKGROUND

In recent studies, an increased incidence of gastric adenocarcinomas was observed in patients with Helicobacter pylori infection. However, the extent to which this coincidence is caused by immunologic mechanisms is unknown.

METHODS

Two human monoclonal antibodies (MoAbs) from patients with stomach carcinoma and H. pylori-associated gastritis were isolated and established by fusion of spleen cells with the heteromyeloma HAB-1. The reactivity of these human MoAbs was investigated in functional adhesion assays and on Western blots of tissue, tumor cell, and bacterial extracts. Their stimulation and proliferation were tested by the MTT test and 3-H-thymidine incorporation tests.

RESULTS

The two monoclonal immunoglobulin-M antibodies, 103/51 and 105/79, inhibited adhesion of tumor cells. On bacterial extracts antibody 103/51 identified protein bands of 55 kilodaltons (kd) and 80 kd, and in tumor cell extracts, a specific protein of approximately about 110 kd and 140 kd. Antibody 105/79 identified a 55 kd protein in bacterial extracts and a 110 kd protein in tumor extracts. In addition, in the 3-H-thymidine incorporation and MTT assay the antibodies showed a stimulatory and growth-enhancing effect on tumor cells in vitro. A similar activity was observed in sera from patients with gastric carcinoma, indicating a physiologic role of such antibodies in vivo.

CONCLUSION

The human monoclonal antibodies described here react with H. pylori and cross-react with and stimulate gastric carcinoma cells. It is possible that the production of these antibodies is primarily stimulated by bacterial antigens which cause chronic gastritis and that they might be indirectly responsible for the recently described higher incidence of gastric cancer because of the simultaneous reaction and stimulation of tumor cells they cause.