Effect of temperature on normal and SV40-transformed human fibroblasts

Laser-induced cell detachment, patterning, and regrowth on gold nanoparticle functionalized surfaces

We report on the selective cell detachment from nanoengineered gold nanoparticle (AuNP) surfaces triggered by laser irradiation, which occurs in a nonthermal manner. The gold nanoparticle-based surfaces reveal good adhesion of NIH3T3 fibroblast cells. Patterning is achieved by lithographic microcontact printing, selective gold nanoparticle deposition, and by laser beam profiling. It is shown that the effectiveness of fibroblast cell detachment depends on the cell age, laser power, and AuNP patterning profile. Heat distribution and temperature rise around gold nanoparticle functionalized surfaces is modeled, revealing low heating of nanoparticles by laser illumination. The nonthermal photochemical mechanism of cell detachment due to production of reactive oxygen species under illumination of gold nanoparticles by green laser light is studied. We also demonstrate that cells migrate from unirradiated areas leading to their reattachment and surface recovery which is important for controlled spatial organization of cells in wound healing and tissue engineering. Research presented in this work is targeted at designing biointerfaces for cell cultures.

Interaction of variable bacterial outer membrane lipoproteins with brain endothelium

Background

Previously we reported that the variable outer membrane lipoprotein Vsp1 from the relapsing fever spirochete Borrelia turicatae disseminates from blood to brain better than the closely related Vsp2 [1]. Here we studied the interaction between Vsp1 and Vsp2 with brain endothelium in more detail.

Methodology/Principal Findings

We compared Vsp1 to Vsp2 using human brain microvascular endothelial cell (HBMEC) association assays with aminoacid radiolabeled Vsp-expressing clones of recombinant Borrelia burgdorferi and lanthanide-labeled purified lipidated Vsp1 (LVsp1) and Vsp2 (LVsp2) and inoculations of the lanthanide-labeled proteins into mice. The results showed that heterologous expression of LVsp1 or LVsp2 in B. burgdorferi increased its association with HBMEC to a similar degree. Purified lanthanide-labeled lipidated Vsp1 (LVsp1) and LVsp2 by themselves were capable of associating with HBMEC. The association of LVsp1 with brain endothelium was time-dependent, saturable, and required the lipidation. The association of Vsp1 with HBMEC was inhibited by incubation at lower temperature or with excess unlabeled LVsp1 or LVsp2 but not with excess rVsp1 or mouse albumin or an anti Vsp1 monoclonal antibody. The association of LVsp2 with HBMEC and its movement from blood to brain parenchyma significantly increased in the presence of LVsp1.

Conclusions/Significance

Variable bacterial outer membrane lipoproteins interact with brain endothelium differently; the lipidation and variable features at the protein dome region are key modulators of this interaction.

Interaction of a neurotropic strain of Borrelia turicatae with the cerebral microcirculation system

Relapsing fever (RF) is a spirochetal infection characterized by relapses of a febrile illness and spirochetemia due to the sequential appearance and disappearance of isogenic serotypes in the blood. The only difference between isogenic serotypes is the variable major outer membrane lipoprotein. In the absence of specific antibody, established serotypes cause persistent infection. Studies in our laboratory indicate that another consequence of serotype switching in RF is a change in neuroinvasiveness. As the next step to elucidate this phenomenon, we studied the interaction of the neurotropic Oz1 strain of the RF agent Borrelia turicatae with the cerebral microcirculation. During persistent infection of antibody-deficient mice, we found that serotype 1 entered the brain in larger numbers and caused more severe cerebral microgliosis than isogenic serotype 2. Microscopic examination revealed binding of B. turicatae to brain microvascular endothelial cells in vivo. In vitro we found that B. turicatae associated with brain microvascular endothelial cells (BMEC) significantly more than with fibroblasts or arachnoidal cells. The binding was completely eliminated by pretreatment of BMEC with proteinase K. Using transwell chambers with BMEC barriers, we found that serotype 1 crossed into the lower compartment significantly better than serotype 2. Heat killing significantly reduced BMEC crossing but not binding. We concluded that the interaction of B. turicatae with the cerebral microcirculation involves both binding and crossing brain microvascular endothelial cells, with significant differences among isogenic serotypes.

Metastatic potential: generic predisposition of the primary tumor or rare, metastatic variants-or both?

Metastasis is a rare event. Does it arise from rare, variant, highly metastatic cells or does a primary tumor progress to a premalignant state from which metastases arise stochastically without further changes in gene expression? Arguments and evidence have been adduced to support either position. A paper in this month's Cancer Cell and other arguments instead suggest models combining features of both.

The E-cadherin gene is silenced by CpG methylation in human oral squamous cell carcinomas

Reduction of E-cadherin strongly relates to invasiveness and metastasis in vitro. To clarify CpG methylation around the promoter region of the E-cadherin gene in oral squamous cell carcinoma (SCC), we examined the DNA samples of various human SCC cell lines and primary oral SCC tissues by methylation-specific polymerase chain reaction (MSP). CpG methylation of the E-cadherin gene markedly correlated to the reduction of E-cadherin expression in human oral SCC cell lines. In primary oral SCC tissues, only 1 of 5 preserved E-cadherin-expressing tissues was methylated, whereas methylation was found in 17 (94.4%) of 18 E-cadherin-reduced tissues. Our results suggest that reduction of E-cadherin expression is associated with CpG methylation of the E-cadherin gene promoter. We recently established two cell lines with high and low metastatic potential, UM1 and UM2, from SCC primary tongue tissue of a patient. E-cadherin expression of high-metastatic UM1 was clearly lower than that of low-metastatic UM2, and MSP results showed CpG methylation in the UM1 but not the UM2 cell line. To investigate whether demethylation of CpG methylation of the E-cadherin gene could restore expression and function of E-cadherin, we treated UM1 with the demethylating agent 5-azacytidine (5-aza) and found that E-cadherin expression was indeed restored by demethylation. Moreover, in the demethylated UM1, invasion of the collagen gel was clearly suppressed compared with the untreated UM1. These results suggested that inactivation of E-cadherin expression resulted from CpG methylation of the gene promoter; a correlation between CpG methylation of the E-cadherin gene promoter and invasive potential was also suggested.

Characterization of F3II, a sarcomatoid mammary carcinoma cell line originated from a clonal subpopulation of a mouse adenocarcinoma

We characterized a new mammary tumor cell line, F3II, previously established in vitro from a clonal subpopulation of the BALB/c transplantable mammary adenocarcinoma M3, moderately metastatic to lung. The F3II cell line has been passaged > 50 times. It has grown as elongated cells adherent to the bottom of the flask. Cytogenetic studies showed that F3II cultures were nearly triploid. Tumor cells expressed fibronectin and showed high levels of cell-surface urokinase, a key protease in invasion and metastasis. F3II cells grew as poorly differentiated, spindle-cell carcinoma tumors (sarcomatoid carcinomas) with a prominent local invasiveness, a high angiogenic response, and a 90-100% incidence of lung metastases when inoculated s.c. into syngeneic mice. Ultrastructural and immunocytochemical analysis revealed characteristic features of carcinomas. Our data suggest that F3II is less differentiated and more aggressive than the original tumor line, supporting the notion that mammary carcinomas are heterogeneous neoplasms and contain subpopulations with diverse biologic behavior. The F3II mouse mammary sarcomatoid carcinoma line is a suitable model to examine antiinvasive, antiangiogenic, and antimetastatic agents.

Cell membrane fluidity and adriamycin retention in a tumor progression model of AKR lymphoma

Counteraction of drug resistance is a major challenge in cancer therapy, particularly in advanced stages. The main mechanism of multidrug resistance is related to an increased drug efflux. In the present study we examined the effect of modifying cell membrane lipid fluidity on uptake of adriamycin (ADR) in cells of AKR lymphoma malignancy variants. Modification of cell membrane fluidity, either by lecithin or by lecithin-cholesterol mixtures, induced in a high proportion of cells of all variants a higher capacity to accumulate ADR. The chemosensitizing effect, for lecithin in particular, was proportional to the degree of malignancy of the lymphoma variants. The increased ADR uptake was up to 1.4-fold in the variant of lowest malignancy and up to 5-fold in the one of highest aggressiveness. This tendency correlates with our previous studies and is of particular value since highly-malignant tumors are often drug resistant. The cholesterol-lecithin mixture, induced, however, in part of the variants the appearance of a small subpopulation with very low ADR permeability. Cell membrane rigidification is of value for exposing tumor cell cryptic antigens but may be deleterious when used in conjunction with chemotherapy.

Increased incidence of undifferentiated type of gastric cancer with tumor progression in 912 patients with early gastric cancer and 1245 with advanced gastric cancer

BACKGROUND

There is little information concerning alteration in histologic differentiation with progression of gastric cancers.

METHODS

The authors analyzed data of 912 patients with early gastric cancer and 1245 with advanced gastric cancer. All patients underwent gastric resection. Special focus was placed on the grade of histologic differentiation.

RESULTS

The undifferentiated type was found in 38% of early gastric cancers and 58% of advanced gastric cancers (P < 0.01). The undifferentiated type was found in 37% of gastric cancers limited to the mucosal layer, and increased with tumor progression into the deep layer to account for 65% of the cancers that invaded the gastric serosa. With regard to tumor location, the undifferentiated type in the gastric body or other locations was more common in patients with advanced gastric cancer (P < 0.01).

CONCLUSIONS

One explanation for the histologic predominance of the undifferentiated type in advanced gastric cancer is that in some gastric cancers, the predominant histologic type may be altered from the differentiated to the undifferentiated type with progression of the tumor.

The influence of local tissue environment on epithelial basement membrane continuity in colorectal carcinomas

For colorectal carcinomas, there is evidence that marked discontinuity of the epithelial basement membrane (EBM) is associated with higher malignant potential. Since the metastatic process appears to be selective, more discontinuous EBMs might be expected in secondary rather than in primary tumours. To test this prediction, we examined a series of 60 cases of colorectal carcinoma for which samples of lymph-node or liver metastases were available. Sections were immunocytochemically stained for laminin, and the continuity of tumour EBM was then assessed by observational rating as well as by detailed morphometric analysis for a sample of cases. Contrary to the above prediction, we find that EBMs tend to be more continuous in secondary tumours than in corresponding primary tumours. These results could be explained by the possibility that local tissue environmental factors have a major influence on EBM continuity. Supporting evidence comes from our previous observation that EBM is very discontinuous at the advancing edge of primary colorectal carcinomas, where the tumour is adjacent to collagen-I-deficient stroma. Further evidence from the present study is that the EBM is extremely discontinuous at the interface between metastases and specialised parechymal tissue, but more continuous at the interface between metastases and stromal connective tissue. Since basement membranes affect the differentiation and behaviour of adjacent cells, these findings suggest that host tissue may influence invasive activity through their effects on EBM continuity.

DNA fingerprinting of renal cell carcinoma with special reference to tumor heterogeneity

Genomic alterations in renal cell carcinoma were investigated by DNA fingerprinting using the simple repetitive oligonucleotide probe (CAC)s. Nine of ten tumors showed somatic changes in the fingerprint pattern compared with constitutional DNA. The most consistent changes were deletions and/or decrease in intensity of a band. When using two or three samples from different parts within the tumor, up to three different cell clones could be detected. These results indicate that DNA fingerprinting analysis can be a useful technique for the study of genomic alterations and tumor heterogeneity in renal cell carcinoma.

Enhanced invasiveness and metastatic potential of epithelial cell lines cultured in the presence of dimethyl sulphoxide

Several passage cycles of poorly metastatic malignant epithelial cells through immunosuppressed mice failed to induce enhanced metastasis-forming ability of cells derived from either the primary subcutaneous tumours or the resultant lung metastases. In vitro treatment of cultured malignant cells with dimethyl sulphoxide (DMSO) induced a reversible change in phenotype towards increased invasiveness but did not significantly increase metastasis formation. A cloned-cell line from a spontaneous in vitro transformant in the presence of DMSO was highly invasive and highly metastatic. In vitro treatment of cultured cells with 2% (v/v) DMSO produced alterations in morphology with decreased growth rate of all cell lines and decreased anchorage-independent colony formation in several malignant cell lines. All in vitro and in vivo effects were reversible following both short- and long-term (1 year) culture of cells in the presence of DMSO, suggesting epigenetic effects. These data support the concept of independent genetic controls for the invasiveness of tumours and the ability to form metastases.

Metastasis and angiogenesis

The relationship of angiogenesis, the growth of new blood vessels, to the process of tumour metastasis is examined. While the occurrence of angiogenesis generally is a necessary prerequisite for the formation of secondary tumours its presence is not a guarantee that cancer dissemination will occur. Novel approaches to antimetastatic therapy, using the newly formed vascular bed of tumours as the target, have produced successful results in experimental animals though such approaches have yet to be undertaken in the clinic.

Gastric cancer heterogeneity

This study was carried out on 222 samples from 37 gastric carcinomas to assess the incidence of multiple stem lines in primary tumors and metastasis as reflected by multiple DNA stem lines and their relationship to epidermal growth factor (EGF) receptor expression, histologic grade, tumor size, and degree of wall infiltration. Fifteen primary tumors (40.5%) were homogeneously diploid/peridiploid whereas 22 (59.5%) were aneuploid. In the lymph node metastasis, seven patients (29.2%) had an homogeneous diploid/peridiploid pattern in all metastatic lymph nodes. On the other hand, 17 (70.8%) had at least one aneuploid peak in the lymph node metastasis. DNA content heterogeneity was seen in 12 (33%) of primary tumors whereas 14 (66.6%) of 21 patients had multiple cell clones in the metastasis. Therefore, 12 patients had a metastatic clone which was not observed in the primary tumor. DNA content heterogeneity was seen even in tumors with submucosal invasion suggesting that this phenomenon is also present at earlier stages. No correlation between the histologic grade and the DNA distribution was observed. Furthermore, histologic heterogeneity was independent of DNA content heterogeneity. The EGF receptor expression was observed in six of the 23 patients in whom this analysis was done. The EGF receptor expression was constant in all samples which were studied and even samples with a different DNA content and histologic grade were stables for the EGF receptor expression.

Cellular interactions determining the production of collagenase by a rat mammary carcinoma cell line

The cellular interactions regulating the production of collagenase by a cell line derived from a spontaneously arising rat mammary carcinoma have been studied. The cell line, BC1, was grown permanently under defined serum-free conditions, so that the poorly characterized and variable effects of serum on collagenase expression were avoided. Two stable subpopulations of cells present in BC1 cultures were defined as epithelioid cells ("E-cells") and myoepithelioid cells ("M-cells"). These subpopulations differed in their morphology, pattern of growth and susceptibility to detachment from culture vessels by trypsin. Seven clones of M-cells and 7 clones of E-cells, obtained by the limiting dilution technique, were used to determine the cellular source of collagenase and the interactions which led to its expression. M-cells displayed an absolute dependence on a soluble factor produced by E-cells for their survival in vitro. The presence of both cellular types in culture was necessary for collagenase secretion to occur, E-cells being the major source of enzyme in mixed cultures. A soluble factor produced by M-cells was largely, if not completely, responsible for the induction of collagenase secretion by E-cells. Clones representative of both subpopulations were tumorigenic in syngeneic host animals. These results suggest that the phenotypic diversity which occurs within populations of neoplastic cells may give rise to subpopulations of cells which display a more aggressive phenotype in coexistence than in isolation.

Glycosphingolipids in lectin-resistant variants of mouse Lewis lung carcinoma cells

Neutral glycolipids and gangliosides from murine Lewis lung carcinoma cell line LL2 and its lectin-resistant variants, differing in metastatic properties, were studied by fast-atom-bombardment mass spectrometry (FAB-MS), exoglycosidase treatment and an immunostaining procedure. The neutral glycolipids identified in all cell lines studied included CMH, CDH, CTH, asialo GM2, globoside and a glycolipid with a preliminary structure of Hex-Hexl-4HexNAc-Hex-Hex-Cer. The major gangliosides were GM3, GM2, GM1 and GD1a. No qualitative differences in glycosphingolipid expression were found between the metastatic cell lines (LL2 and LL2AAA) and the weakly metastatic variants (LL25, LL28, LL230 and LL2RCA II). Some quantitative differences were observed between the cell lines, e.g., in the level of ganglioside-bound sialic acid, which was not apparently correlated with the metastatic capacities.

Inhibition of metastatic potential by fucosidase: an NMR study identifies a cell surface metastasis marker

NMR spectroscopy is able to detect subtle changes to the surface chemistry of cells. We have previously shown that high-resolution 1H NMR methods can identify tumor cells with the capacity to metastasize, and we now report that the long T2 relaxation value (500-800 ms) observed in metastatic rat mammary adenocarcinoma cells is removed by treatment with fucosidase. Two-dimensional scalar-correlated NMR (COSY) spectra of fucosidase-treated cells show that a cross peak, consistent with scalar coupling between the methyl and methine groups on fucose and usually associated with malignancy and metastatic ability, is absent. Metastases were observed in only two out of ten rats injected subcutaneously with enzyme-treated cells compared to eight out of ten with untreated cells. NMR studies on isolated cellular lipids identified the long T2 relaxation value only in the ganglioside fraction. This fraction accounts for 51% of the total 14C-labelled fucose incorporated into the cells. We propose that fucogangliosides are an indicator of metastatic potential in rats. The observation that a cell surface metastasis marker has an NMR signal with a characteristically long relaxation value has important consequences for the future use of magnetic resonance imaging and spectroscopy in the cancer clinic.

DNA distribution pattern of the so-called severe dysplasias and small carcinomas of the colon and rectum and its possible significance in the tumor progression

The DNA distribution pattern was determined by cytofluorometry in 25 cases of colorectal small carcinoma and the so-called severe dysplasia. The colorectal carcinoma and "severe dysplasia" consisted of four principal stemlines as to DNA ploidy: diploidy, aneuploidy, and their respective polyploidies. These patterns appeared in various combinations in individual neoplasms. DNA distribution of the severe dysplasia was diploid-predominant (11 cases) or aneuploid-predominant (three cases), usually showing mosaicism in various degrees with respective first order polyploidy. Similar DNA distribution patterns also were found in submucosally invasive small carcinomas. The neoplastic cell populations of a higher polyploidy (second or third order), however, occurred only in the submucosally invasive carcinomas (three cases) regardless of their basic ploidy. The mitotic index tended to be higher in the aneuploid-predominant tumors than in the diploid-predominant tumors. In the current observation, there was no significant correlation between the DNA distribution pattern and histologic type of the "dysplasia" or carcinoma. We found that most of the so-called severe dysplasias of the colon and rectum already gained definitive characteristic of carcinoma in the DNA pattern, i.e., ploidy heterogeneity. Therefore, they can be identified as intramucosal carcinomas, distinct from the normal epithelia and adenomas of the colon and rectum.

B16 melanoma in hairless mice: a model for thermographic research

Little is understood concerning the mechanism of tumor-induced thermographic abnormalities observed in man. An ideal animal model is lacking. In an effort to create such a model we have worked with hairless mice, subcutaneously inoculated with B16 melanoma cells. This report documents the progress of that work and the subsequent development of a totally satisfactory system for the study of such tumors in a hairless animal.

Simultaneous in vitro drug sensitivity testing on tumors from different sites in the same patient

A human tumor cloning assay was used to analyze drug sensitivity profiles for 99 pairs of tumor samples taken simultaneously from the same patient. These pairs included two areas of the same primary (12 pairs), primary tumor versus metastasis (29 pairs), and metastasis versus metastasis (45 pairs). In addition, to assess variability in the culture and sensitivity techniques, 13 specimens were divided equally and processed twice. One hundred fourteen evaluable drug sensitivity tests were performed on the specimen pairs. Drug sensitivity profiles for the same specimen processed twice demonstrated good agreement (P = 0.03). Sensitivity profiles from two different areas of the same primary were also quite similar (P = 0.002). However, when one sampled a primary tumor and its metastasis for drug sensitivity testing, the agreement (in terms of percent survival) was poor (P = 0.84). Agreement was also poor for drug sensitivity profiles of one metastasis versus another metastasis (P = 0.39). This heterogeneity in drug sensitivity profiles of primary versus metastasis and of metastasis versus metastasis could account for some of the false positives and false negatives noted in clinical correlation trials with the cloning assay. It may also have implications for adjuvant treatment programs where chemosensitivity of the primary tumor can be determined, but will probably not be predictive for chemosensitivity of the micrometastases.

Biology of metastasis

The acquisition by tumor cells of the ability to metastasize is the critical event in the clinical course of most human neoplastic disease. While metastasis plays a pivotal role in the ultimate success of failure of therapy, it is in fact a result of a more insidious malignant process termed tumor progression. It is the progression of tumors from a less to a more malignant phenotype that results in tumor heterogeneity and the selection of cells with a more malignant (metastatic) phenotype. The development of metastases is thus integrally related to the mechanisms of tumor progression, which in turn is likely due to the instability of the tumor cell genome. The authors' thesis is that metastatic tumor cells are a selected population derived from a heterogeneous parent tumor which contains many clones with different phenotypes. This discussion will, therefore, address the role of tumor genomic instability as a basis for the selection of metastatic cells.

Phenotypic heterogeneity of a tumor-associated antigen in adenocarcinomas of the colon and their metastases as demonstrated by monoclonal antibody B72.3

To determine the potential antigenic heterogeneity which might exist between a primary colon carcinoma lesion and its metastases, we stained the formalin and Zenker's fixed paraffin-embedded tissues from the resection specimens of 12 patients with Duke's Stage C adenocarcinoma of the colon with monoclonal antibody (MAb) B72.3. This MAb previously has been shown to react with a high molecular weight tumor-associated glycoprotein (termed TAG-72), which is selectively expressed in adenocarcinomas versus normal adult tissue. Five to 90% of malignant cells from all primary lesions stained with MAb B72.3 in paraffin-embedded tissue. A significantly diminished percentage of cells stained from the metastases in lymph nodes and distant sites. Pearson correlation coefficients showed that the antigenic expression of the metastasis in the lymph node was a better indicator of the antigenic expression of the metastasis in the distal site than was the primary lesion in the colon. These findings suggest that the effective use of monoclonal antibodies for diagnostic imaging or therapeutic purposes may require the evaluation of the antigenic expression in regional node metastases rather than that of the primary lesion.

Evaluation of drug efficacy in vitro using human small cell carcinoma of the lung spheroids

Five human small cell carcinoma of the lung (SCCL) cell lines selected from 25 established cultures were grown as three-dimensional spheroid tumor models in either spinner culture or in static, agar-coated multiwells. Volume doubling times for the cell lines were approximately 4.5 days. Decreases in spheroid volumes after exposure to a variety of chemotherapeutic agents were used as indicators of drug activity. To further quantify cell killing in SCCL spheroids by chemotherapeutic agents 24 hours after exposure to drugs, a technique was employed that measured maximum levels of incorporation of 125IUdR after continuous labeling for 48 hours. The results of the use of this assay report for SCCL spheroid responses to various concentrations of doxorubicin hydrochloride, cytosine arabinoside, mechlorethamine hydrochloride, cisplatin, or etoposide. Some evidence for an intertumor heterogeneous response to chemotherapy is presented for some of the drugs tested. This assay was also used to characterize a potentiated cell kill when etoposide is combined with cisplatin and to identify activity by a new compound, diazoacetylcholine iodide (DACI), which was synthesized as an agent targeted for SCCL cells.

DNA content in renal cell carcinoma with reference to tumor heterogeneity

DNA content was successfully determined by flow cytometry in 196 tissue samples from 25 renal cell carcinomas. Twelve tumors (48%) were homogeneously diploid/near-diploid, whereas 11 tumors were aneuploid and 2 tumors were polyploid. Cell clones with different DNA content were found in 11 tumors demonstrating a considerable heterogeneity in the non-diploid tumors; 9 of these 11 heterogeneous tumors contained both aneuploid and diploid cell clones. Tumor samples morphologically classified as grade 1 and 2 were 98% diploid and grade 4 samples were 78% aneuploid. No correlation between DNA distribution and morphologic grade was found for grade 3 tumor samples. Tumor proliferation rate, as determined by the fraction of cells in S-phase, was significantly higher in aneuploid samples compared to normal kidney tissue samples and diploid tumor samples.

Surgical intervention and metastasis

Recent findings, briefly summarized here, show that the dissemination of neoplastic cells is an early and continuing process; that individual tumor cells in a malignant tumor possess differing metastatic capacities; and that metastases can arise from specific subpopulations of tumor cells. These findings have considerable implications for the understanding and treatment of systemic malignancies. The underlying cause for the finding that surgical removal of the primary local tumor is often followed by considerably enhanced outgrowth of established micrometastases is not yet understood. The trauma and stress associated with surgical intervention does not of itself seem to constitute a major tumor-promoting component. More likely candidates responsible for enhanced outgrowth of metastases after surgery are the removal of the growth-inhibitory restraint that the primary tumor exerts on disseminated neoplastic cells.

Characterization of the heterogeneity of R3327 rat prostatic tumors derived from single-cell clones

Prostatic adenocarcinoma is characterized by cellular diversity, which is well demonstrated in the Dunning R3327 rat prostatic adenocarcinoma. This heterogeneity may arise from epigenetic influences, ie, cellular adaptation or selection, and/or from genetic changes. To investigate the question of genetic instability, four tissue culture cell lines were derived from single cells isolated from the uncloned late (UCL) passage of the Dunning R3327H prostate cell culture. Each of these clonally derived tissue cultures was injected into castrated and intact young adult male rats for tumor production. Uncloned early (UCE) and UCL passage tissue cultures were also propagated as solid tumors. Tumors and the cultures from which they were derived were examined for evidence of phenotypic and genetic changes using morphological and cytometric methods. Transmission and scanning electron microscopy revealed only slight differences among the cell cultures. A single population of diploid cells was demonstrated in each of the cell cultures by propidium iodide staining and subsequent flow cytometric measurement of DNA content/nucleus. Tumors of unicellular as well as multicellular origin exhibited extreme heterogeneity of histological features, both among animals as well as within a single tumor. Tumors were surveyed and tissue types were characterized and cataloged. Clone 3 was generally better differentiated than the others; tumors from castrated animals were better differentiated than those from intact animals. Flow cytometry revealed multiple hyperdiploid cell populations that were variable from one sample to another. We concluded that changes in genotype as well as phenotype occurred in the tumors derived from single cells. Some of these changes may have occurred in the cells while still in culture.

Monoclonal antibodies to breast cancer-associated antigens as potential reagents in the management of breast cancer

Monoclonal antibodies reactive with the surface of human breast carcinoma cells have been generated and characterized. The immunogens used were membrane-enriched fractions of metastatic carcinoma lesions. The various monoclonals were shown to react with previously known as well as with novel tumor-associated antigens (TAAs). The most specific of the latter group is monoclonal B72.3, which is reactive with a 220,000 to 400,000 high-molecular-weight glycoprotein complex found in 50% of human mammary carcinomas and 80% of human colon carcinomas. Monoclonal antibody B6.2, which recognizes a 90,000-d glycoprotein, was radiolabeled and shown to efficiently localize human carcinoma transplants in athymic mice via gamma imaging without the use of second antibody or background subtraction manipulations. F(ab')2 and Fab' fragments were shown to be more efficient for tumor localization than intact immunoglobulin. Whereas the phenomenon of antigenic heterogeneity of tumor cell populations has long been known to exist, this phenomenon was also shown to manifest itself as antigenic modulation, in which specific TAAs can modulate their expression on the cell surface concurrent with different phases of the cell cycle. A phenomenon known as antigen evolution, in which a specific cloned tumor cell population can gradually drift in antigenic phenotype, has also been demonstrated. Recombinant interferon has been employed to (1) enhance the expression of specific TAAs on the surface of tumor cells already expressing the antigen; and (2) induce the expression of specific TAAs on the surface of carcinoma cells not previously expressing the antigen. The clinical implications of such phenomena in gamma scanning for the detection of tumor masses and for tumor immunotherapy are discussed. Methods for circumvention of problems inherent in the clinical use of monoclonal antibodies are also addressed.

Stable quantitative differences of antigen expression in human melanoma cells isolated by flow cytometric cell sorting

The stability of expression of a membrane antigen on human FME melanoma cells was investigated by means of flow cytometric cell sorting and analysis. The melanoma-associated 250 kd antigen was strongly expressed on all cells, as recognized by binding of the monoclonal antibody 9.2.27. By flow cytometric cell sorting, cells of high and low antigen expression were isolated, and the difference in antigen expression between the two populations was examined as a function of time in culture. Immediately after sorting, the median fluorescence intensities of the two populations differed by a factor of 2.7. After the first few days in culture, much of the range in antigen expression of the parent population was regenerated. However, a lasting difference in antigen expression was established, corresponding to 50% higher density of antigen on the cells sorted for high fluorescence intensity, compared to those sorted for low intensity. After trypsin treatment, which removed the antigen from the cell surface, normal antigen expression was regained after 2-3 days in culture, with the same difference between the two populations as before the trypsin treatment. The stability of the established difference in antigen expression between the two sorted subpopulations indicates that expression of this antigen is a precisely controlled, heritable characteristic of the FME melanoma cells.

Progression of mammary adenocarcinomas as reflected by nuclear DNA content

In 18 breast cancer patients the DNA histograms observed in the primary tumor at the date of diagnosis were compared with those found in the corresponding local and distant metastases at autopsy up to more than 12 yr later. All patients, except one, exhibited the same type of DNA histogram in both the primary tumor and its metastases. In one patient the DNA histogram changed from an euploid type in the primary breast carcinoma to an aneuploid type in the metastases. The results are interpreted as indicating that mammary adenocarcinoma in general exhibit a high degree of stability of the nuclear DNA content during the history of the disease. It is suggested that in breast cancer progression of the tumor disease is more likely due to a net increase and/or dissemination of tumor cells exhibiting similar genetic properties and malignancy potential than to a progressive dedifferentiation and increase of malignancy of the tumor cells.

Characterization of in vitro immunoselected variants from a highly metastatic murine tumor for alterations in malignant behavior in vivo

A new Ly-6.2- antigen-loss variant (called L61 -M1) of the highly metastatic DBA/2 mouse (Ly-6.2+) MDAY-D2 tumor has been obtained by means of a monoclonal anti-Ly-6.2 antibody in an in vitro immunoselection technique. Whereas L61 -M1 grew poorly when inoculated subcutaneously into the syngeneic host, it grew and metastasized in a similar way to the parental MDAY-D2 tumor when inoculated into immunosuppressed, athymic nude mice. L61 -M1 as well as another Ly-6.2- variant of the same MDAY-D2 tumor (called L61 ) which is poorly metastatic in the syngeneic host salvaged exogenous fucose into glycoproteins and glycolipids at rates 5.5 and 7.8 times that of the parental MDAY-D2 line. In contrast, the Ly-6.2- variants exhibited a 50-70% decrease in the incorporation of exogenous mannose into glycoproteins and glycolipids. L61 -M1 and L61 also exhibited alterations in the structures of the oligosaccharide moieties linked to the cell surface glycoproteins and/or glycolipids. Thus, the in vitro immunoselection technique can be used to obtain a panel of variants with stable phenotypic alterations in their growth and metastatic capacities. Such mutants may, like previously described lectin-resistant mutants, be useful in studying the contribution of cell surface glycoproteins and glycolipids to tumorigenicity and metastasis.

Successful immunotherapy in a murine metastasizing fibrosarcoma model

Antigenic differences were demonstrated between the primary murine fibrosarcoma and its metastases. Immunization with irradiated primary tumor cells (TC) protected C57B1/6J mice against subsequent challenge with those cells, but not against challenge with cells from pulmonary metastases (PMC). Mice immunized with irradiated PMC were protected from challenge with those cells, but not against challenge with TC. Mice with fibrosarcomas produced by the injection of 5 X 10(3) cells from the primary tumor were treated by resection of the tumor-bearing limb (Amp), Amp plus cyclophosphamide (Amp + Cy), Amp plus primary TC (Amp + TC), Amp plus primary TC and from its metastatic variant (Amp + TC + PMC), and with combinations of the last two groups with Cy. Although Amp + Cy improved survival, no animal lived 100 days and metastases increased as compared to controls. Immunotherapy significantly improved survival and decreased pulmonary metastases. Antigen combinations from primary and metastatic tumors resulted in significantly better survival than did a single preparation only from TC. Chemotherapy did not enhance the results obtained with immunotherapy and surgery. Immunity conferred in long-term survivors was permanent.

Cell surface molecules and tumor metastasis. Regulation of metastatic phenotypic diversity

Metastatic tumor cells are characterized by quantitative alterations in cell surface and other properties that confer to these cells their abilities to invade, disseminate, implant, survive and grow at secondary sites. Metastasis is also determined by a variety of host factors that prevent, allow or even stimulate metastatic processes. The emergence of diversified cell subpopulations in malignant tumors insures that some cells will ultimately become highly metastatic, resulting in tumor progression towards characteristics which are the most favorable for survival and growth. Unknown mechanisms appear to stimulate and then to control phenotypic diversification of tumor cell subpopulations. These mechanisms may be altered by genetic (mutational) and/or epigenetic (non-mutational) modifications that individually influence cells within a malignant neoplasm.

Cell surface properties of high- and low-metastatic cell lines selected from a spontaneous mouse lung carcinoma

The surface oligosaccharide residues, glycoproteins and sialyl components of CMT64 lung carcinoma cells and high-metastatic sublines CMT167 and CMT181 have been studied in culture. (1) The total cellular sialic acid content did not differ appreciably between the three lines. However, the accessibility of surface sialyl groups, measured by metabolic incorporation of [3H]NAcmannosamine followed by neuraminidase hydrolysis, was decreased from 42% in CMT64 to 25% hydrolyzed in CMT181. (2) The major plasma membrane glycoproteins of the lines were radiolabelled by lactoperoxidase iodination, metabolic incorporation of [3H]fucose or labelling in the terminal sialyl residues by the NaIO4-NaB[3H]4 method and the labelled glycoproteins were analyzed by two-dimensional gel electrophoresis. Each labelling technique identified a complex pattern of glycoproteins including a prominently labelled group of high-molecular-weight acidic sialoglycoproteins: GP200/4.9-5.1 (apparent molecular weight X 10(-3)/pl of iodoprotein); GP150/5.1-5.6; GP130/5.0-5.6; GP110/5.0; GP100/4.8 and GP100/5.0-5.4. (3) The neuraminidase-susceptible glycoproteins on CMT64 and CMT181 were identified in the isoelectric focusing separation of the two-dimensional gel separation by the charge difference caused by desialylation. The glycoproteins most susceptible to neuraminidase were the high-molecular-weight acidic glycoproteins which showed marked charge heterogeneity: GP150/5.1-5.6, GP130/5.0-5.6; GP100/5.0-5.4 and GP100/4.8. (4) Using these procedures we did not detect modifications between CMT181 and CMT64 and we conclude that the cultured cells of the sublines do not display marked surface glycoprotein alterations that reflect their enhanced spontaneous metastatic potential.

Increase in homotypic aggregation of metastatic Morris hepatoma cells after fusion with membranes from non-metastatic cells

Three types of Morris hepatoma: 7288C, 5123tc, and 9618A were assessed for their ability to grow and produce metastases in the lungs of male buffalo rats. Hepatoma 7288 formed metastatic growths more rapidly than 5123, while 9618 did not form metastatic growths in the lung at all. Cells from the same three hepatomas were then assessed for their ability to aggregate homotypically in vitro. This was used as a measure of potential for detachment from the site of primary growth in vivo, one of the critical steps in metastasis. The results were that 9618 aggregated more effectively than 5123 and 7288 did not aggregate homotypically. Thus, the ability to metastasize and the ability to aggregate homotypically were inversely related in these three tumors, with the most metastatic tumor, 7288, hardly aggregating at all. Was the ability of hepatoma 9618 to aggregate homotypically and the inability of hepatoma 7288 to do so a characteristic of the plasma membrane? Plasma membranes either from the tumor which aggregated best, 9618, or from the liver of non-tumorous neonatal buffalo rats were fused into the surface of the 7288 cells. Either fusion conferred the ability to aggregate on the previously non-aggregating metastatic hepatoma cells. In contrast, fusion of plasma membranes from hepatoma 7288 into 9618 cells failed to affect their ability to aggregate homotypically. The aggregation-conferring effect required actual fusion of the donor membrane, was dependent on the amount of membrane fused and was sensitive to treatment of the donor plasma membranes with trypsin. The results are interpreted as suggesting the presence of homotypic aggregation materials, probably proteins, in the plasma membranes of non-metastatic cells. These may be reduced or absent in the membrane of the highly metastatic hepatomas.

The use of cell fusion to analyse factors involved in tumour cell metastasis

Cell fusion has been used to study some of the factors involved in the process of metastasis. Highly metastatic rat mammary adenocarcinoma cells were fused with various non-metastatic cells and the hybrid clones isolated. These were then tested for their metastatic potential either by injecting the cells intravenously and measuring lung colony formation or by injecting the cells subcutaneously and measuring their ability to form lymphatic metastases. With most hybrid clones tested, the metastatic potential was either inhibited or greatly suppressed; thus this phenotype is a recessive characteristic. We also monitored the hybrid cells' ability to produce plasminogen activator (PA) a serine proteinase thought to be involved in the formation of metastatic lung foci. Whilst the highly metastatic parent cells produced large quantities of PA, none could be detected in the non-metastatic lines. Although the hybrid clones produced little PA activity this could not be correlated with their decreased metastatic potential in that one clone, after extensive in vitro culture, reverted to a more metastatic line without a concomitant increase in PA activity. The suppressed PA activity may be due to the presence of an inhibitor that is spontaneously produced by the hybrid cells.

Isopycnic density-gradient centrifugation: a separation parameter which improves flow cytometric measurements on heterogeneous tumors

The analytic and prognostic value of flow cytometric measurements can generally be improved by preseparation of cells. The present data demonstrate clearly the distinct character of bands obtained in density-gradient separation. Density-gradient centrifugation in Percoll after extensive Ca2+ + Mg2+ elimination helps to resolve more detail in flow cytometric measurements (e.g., additional DNA stem lines in human tumors) and can be used in studies of tumor heterogeneity. The significance of investigations of tumor heterogeneity is demonstrated by the different reactivity of subpopulations of the experimental murine tumor S 180 to vincristine.

Mechanisms of neoplastic transformation

This paper introduces a series of invited essays on current controversies in basic cancer research. The initial group of essays focuses on the detection and interpretation of molecular and cellular changes suspected to be of importance in the cause and pathogenesis of cancer. There are two formats: (i) differing viewpoints are presented in parallel, or (ii) the author(s) evaluate a hypothesis in light of available data. Each type of paper aims to critically evaluate current hypotheses and supporting data, while avoiding pronouncements on validity. Recent advances in molecular biology now permit us to consider genes as chemical entities. Individual genes can be isolated, cloned to produce multiple copies, sequenced, and assayed for biological function. This new molecular technology is being applied to fundamental questions in cancer research. The controversies resulting from these pioneering studies are the topics of the initial papers in this series. Forthcoming essays will concern the mechanism(s) of tumor promotion; a search for cancer genes by DNA transfection; the role of DNA rearrangements as initiating events in carcinogenesis; the O6 position of guanine as a critical target of carcinogens; and metals as mutagens and carcinogens.