Liposomes bearing polyethyleneglycol-coupled transferrin with intracellular targeting property to the solid tumors in vivo

PURPOSE

The purpose of this study was to determine the usefulness of transferrin (TF)-pendant-type polyethyleneglycol (PEG)-liposomes (TF-PEG-liposomes), in which TF was covalently linked to the distal terminal of PEG chains on the external surface of PEG-liposomes as a carrier for in vivo cytoplasmic targeting to tumor cells.

METHODS

Small unilamellar TF-PEG-liposomes (100-140 nm in diameter) were prepared from DSPC, CH, DSPE-PEG, and DSPE-PEG-COOH (2:1:0.11:0.021, molar ratio), and were conjugated to TF via the carboxyl residue of DSPE-PEG-COOH. The intracellular targeting ability of TF-PEG-liposomes to tumor cells was examined in vitro and in Colon 26 tumor-bearing mice.

RESULTS

TF-PEG-liposomes, bearing approximately 25 TF molecules per liposome, readily bound to mouse Colon 26 cells in vitro and were internalized by receptor-mediated endocytosis. TF-PEG-liposomes showed a prolonged residence time in the circulation and low RES uptake in Colon 26 tumor-bearing mice, resulting in enhanced extravasation of the liposomes into the solid tumor tissue. Electron microscopic studies in Colon 26 tumor-bearing mice revealed that the extravasated TF-PEG-liposomes were internalized into tumor cells by receptor-mediated endocytosis.

CONCLUSION

TF-PEG-liposomes had the capabilities of specific receptor binding and receptor-mediated endocytosis to target cells after extravasation into solid tumors in vivo. Such liposomes should be useful for in vivo cytoplasmic targeting of chemotherapeutic agents or plasmid DNAs to target cells.

Intercellular junctions, apical differentiation, and infiltrative features in colon cancer: an ultrastructural study. The Colon Cancer Team at IMAS

Changes in the structure and number of cell junctions have been related to the infiltrative and metastatic potential of tumor cells. Apparently, the loss of cell adhesion should be coordinated with significant changes in the apical and basal cell domains. The authors have performed a sequential ultrastructural study of cells in the superficial, middle, and deep regions of well- and moderately differentiated colon adenocarcinomas. This was to investigate the differences in the organization of different membrane domains among tumor cells in the in situ areas, the advancing, infiltrative edge of the tumors, and the infiltrating zones between these two extreme zones. The results of the study suggest that the organization of these domains is not strictly coordinated, and that, for each infiltration level, both a settling and an infiltrating cell population can be found. These findings could explain the fact that apparently well-differentiated tumors are able to seed distant tissues with individual cells, rather than with well-differentiated glandular aggregates that would hardly be able to reach the vessel lumina without significantly modifying their organization.

3D microvascular architecture of pre-cancerous lesions and invasive carcinomas of the colon

Despite the significance of tumour neoangiogenesis and the extensive knowledge on the molecular basis of blood vessel formation currently no quantitative data exist on the 3D microvascular architecture in human primary tumours and their precursor lesions. This prompted us to examine the 3D vascular network of normal colon mucosa, adenomas and invasive carcinomas by means of quantitative microvascular corrosion casting. Fresh hemicolectomy specimens from 20 patients undergoing cancer or polyposis coli surgery were used for corrosion casting, factor VIII and VEGF immunostaining. In addition, immunostaining was done on colorectal tissue from 33 patients with metastatic and non-metastatic carcinomas, polyposis coli and adenomas. This first quantitative analysis of intervessel and interbranching distances, branching angles and vessel diameters in human cancer specimens revealed distinct patterns of the microvascular unit in the tumour centre and periphery. Irrespective of the tumour localization and grading all individual tumours displayed qualitatively and quantitatively the same vascular architecture. This gives further evidence for the existence of a tumour type-specific vascular architecture as recently demonstrated for experimental tumours. Metastatic tumours displayed different vascular architectures only within hot spots, in terms of smaller intervascular distances than in non-metastatic tumours. Pre-cancerous lesions have in part virtually the same vascular architecture like invasive carcinomas. Comparison of VEGF immunostaining also suggests that angiogenesis sets in long before the progress towards invasive phenotypes and that the so-called angiogenic switch is more likely a sequence of events. © 2001 Cancer Research Campaign www.bjcancer.com

A new method for assaying adhesion of cancer cells to the greater omentum and its application for evaluating anti-adhesion activities of chemically synthesized oligosaccharides

A new ex vivo method for assaying adhesion of cancer cells to the greater omentum has been developed using mouse greater omentum and [3H]labelled human gastric and mouse colorectal cancer cells. Since the adhesion rates were found to increase up to 18 h and labelled cells seemed to be stable during the period, the present method could be useful for investigating adhesion of cancer cells to the greater omentum, which must occur at the first step of the peritoneal dissemination. The adhesion of cancer cells to the greater omentum was inhibited by a series of chemically synthesized oligosaccharides and Gal beta1,3[3OMeGal beta1,4GlcNAc beta1,6]alphaBn was found to be the best inhibitor. The anti-tumor effect of this novel tetrasaccharide in vivo was shown in preliminary experiments using Balb/c mice and colon26 cells.

Post-initiation effects of chlorophyllin and indole-3-carbinol in rats given 1,2-dimethylhydrazine or 2-amino-3-methyl- imidazo

Chlorophyllin (CHL) is a water-soluble derivative of chlorophyll, the ubiquitous pigment in green and leafy vegetables, whereas indole-3-carbinol (I3C) is present in cruciferous vegetables such as cabbage, broccoli and cauliflower. In rats initiated with 1,2-dimethylhydrazine (DMH), CHL and I3C reportedly promoted or enhanced the incidence of colon tumors when they were administered after, or during and after the carcinogen exposure, respectively. The same compounds given post-initiation inhibited the formation of colonic aberrant crypts induced by heterocyclic amines, such as 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), but tumor suppression was not examined in the latter studies. In the present investigation, male F344 rats were treated with IQ or DMH during the first 5 weeks of a 1 year study; IQ was given in the diet (0.03%), whereas DMH was administered once a week by s.c. injection (20 mg/kg body wt). Beginning 1 week after the last dose of IQ or DMH until sacrifice, rats received 0.001, 0.01 or 0.1% (w/v) CHL in the drinking water or 0.001, 0.01 or 0.1% I3C in the diet. Compared with controls given carcinogen alone, 0.1% I3C treatment suppressed the multiplicity of IQ-induced colon tumors, and CHL inhibited in a dose-related manner the incidence of IQ-induced liver tumors. However, 0.001% CHL increased significantly the multiplicity of DMH-induced colon tumors while having no effect on the colon tumors induced by IQ. These results indicate that both the choice of carcinogen as well as the dose of the tumor modulator can be important determinants of the events that occur during post-initiation exposure to CHL or I3C. Based on the present findings and data in the literature, it is possible for CHL and I3C to act as tumor promoters or anticarcinogens, depending upon the test species, initiating agent and exposure protocol.

Follicular dendritic cell sarcoma of the colon mimicking stromal tumour

AIMS

Follicular dendritic cell tumours are very rare neoplasms that often occur in lymph nodes. We report here a case in the colon, a hitherto unreported site, in a 37-year-old female. The differentiation from gastrointestinal stromal tumour is emphasized.

METHODS AND RESULTS

The tumour was tan, elastic and solid with surface ulceration. Microscopically, it was composed of oval to spindle tumour cells with syncytial cytoplasm arranged in fascicular and whorled patterns. There were many infiltrating lymphocytes. The histological appearance resembled gastrointestinal stromal tumour, thymoma or meningioma. Distinct from the stromal tumour, the lymph node was also involved by the tumour. Immunohistochemically, the tumour cells were positive for CD21, CD35 and CD68, but negative for cytokeratin, CD34, smooth muscle actin, desmin, S100 protein, epithelial membrane antigen, leukocyte common antigen, HMB-45 and c-kit. In-situ hybridization study was negative for Epstein-Barr virus RNA sequences. Ultrastructurally, the tumour cells possessed cytoplasmic processes joined by desmosomes.

CONCLUSIONS

This entity should be considered in the list of differential diagnoses for gastrointestinal stromal tumour. The lymph node metastasis and immunohistochemical features are of value for identification of this rare neoplasm.

In vivo and in vitro interactions between human colon carcinoma cells and hepatic stellate cells

Stromal reaction is important for the growth of cancer both in primary and metastatic sites. To demonstrate this reaction during the hepatic metastasis of human colon carcinoma, we histologically investigated alterations to the distribution and phenotype of hepatic stellate cells (HSCs), the only mesenchymal cells in the liver parenchyma, using a nude mouse model. Intrasplenically injected colon carcinoma LM-H3 cells migrated into the space of Disse and underwent proliferation, in close association with hepatocytes and HSCs, at 2 days. At 14 days, HSCs were accumulated around the tumor mass and expressed alpha-smooth muscle actin, a marker for HSC activation. We next investigated in vitro the growth factors involved in the interactions between LM-H3 cells and HSCs. Conditioned medium of rat HSCs which underwent culture-induced activation contained platelet-derived growth factor (PDGF)-AB, hepatocyte growth factor (HGF) and transforming growth factor (TGF)-beta, and could augment LM-H3-cell proliferation and migration. Neutralizing antibodies against PDGF-AA and PDGF-BB and those against PDGF-BB and HGF inhibited proliferation and migration, respectively, of LM-H3 cells, whereas antibody against TGF-beta had no effect. LM-H3 cells expressed PDGF receptors-alpha and -beta and c-met. Conditioned medium of LM-H3 cells contained PDGF-AB, and could enhance HSC proliferation and migration. This augmenting effect was suppressed by treatment with anti-PDGF-AB antibody. The present study has demonstrated that bidirectional interactions involving PDGF and HGF take place in vitro between colon carcinoma cells and HSCs, raising the possibility that similar interactions might be involved in the stromal reaction during hepatic metastasis.

Ultrastructure of early phase hepatic metastasis of human colon carcinoma cells with special reference to desmosomal junctions with hepatocytes

To demonstrate ultrastructural events in the early phase of hepatic metastasis of human colon carcinoma, we intrasplenically injected a highly metastasizable, human colon carcinoma cell line LM-H3 (1 x 10(6) cells) into nude mice, and electron microscopically investigated the hepatic metastasis. At 24 h, tumor cells adhered to the endothelial wall of terminal portal venules and periportal sinusoids. At 48-72 h, after extravasation, they deeply invaded the hepatic cell plate and the interstitial tissue of the portal tract, in which they underwent proliferation and made the metastatic foci. Tumor cells were linked with each other or with surrounding hepatocytes by desmosomes. Desmosomes were maintained during the mitosis. When invading tumor cells were exposed to the bile canaliculi, they generated microvilli on the surface. Microvilli were also formed at the luminal surface of intracytoplasmic inclusions. In the interstitial tissue of the portal tract, tumor cells were closely associated with fibroblasts. However, no junctional specializations were seen between them. The present study demonstrated that human colon carcinoma cell line LM-H3 formed desmosomes with hepatocytes soon after invasion of the hepatic cell plate, suggesting the regulatory role of an interaction with hepatocytes in the growth of metastatic foci within the liver parenchyma.

Autophagic and apoptotic types of programmed cell death exhibit different fates of cytoskeletal filaments

Programmed cell death comprises several subtypes, as revealed by electron microscopy. Apoptosis or type I programmed cell death is characterized by condensation of cytoplasm and preservation of organelles, essentially without autophagic degradation. Autophagic cell death or type II programmed cell death exhibits extensive autophagic degradation of Golgi apparatus, polyribosomes and endoplasmatic reticulum, which precedes nuclear destruction. In the present study, we analysed the fate of cytokeratin and F-actin during autophagic cell death in the human mammary carcinoma cell line MCF-7 because recent studies suggest that an intact cytoskeleton is necessary for autophagocytosis. Programmed cell death was induced by 10(-)(6) M tamoxifen. For quantitative light microscopic analysis, autophagic vacuoles were visualized by monodansyl cadaverin, which stains autophagic vacuoles as distinct dot-like structures. In control cultures, the number of monodansylcadaverin-positive cells did not exceed 2%. Tamoxifen induced a dramatic increase 2–4 days after treatment to a maximum of 60% monodansylcadaverin-positive cells between days 5 and 7. Cell death, as indicated by nuclear condensation, increased more gradually to about 18% of all cells on day 7. In cells with pyknotic nuclei cytokeratin appeared disassembled but retained its immunoreactivity; actin was still polymerized to filaments, as demonstrated by its reaction with phalloidin. Western blot analysis showed no significant cleavage of the monomeric cytokeratin fraction. For comparison, apoptotic or type I cell death was studied using the human colon cancer cell HT29/HI1 treated with the tyrosine kinase inhibitor tyrphostin A25 as a model. Cleavage of cytokeratin was already detectable in early morphological stages of apoptosis. F-actin was found to depolymerize; its globular form could be detected by antibodies; western blot analysis revealed no products of proteolytic cleavage. In conclusion, in our model of apoptosis, early stages are associated with depolymerization of actin and degradation of intermediate filaments. In contrast, during autophagic cell death intermediate and microfilaments are redistributed, but largely preserved, even beyond the stage of nuclear collapse. The present data support the concept that autophagic cell death is a separate entity of programmed cell death that is distinctly different from apoptosis.

RhoA function in lamellae formation and migration is regulated by the alpha6beta4 integrin and cAMP metabolism

Clone A colon carcinoma cells develop fan-shaped lamellae and exhibit random migration when plated on laminin, processes that depend on the ligation of the alpha6beta4 integrin. Here, we report that expression of a dominant negative RhoA (N19RhoA) in clone A cells inhibited alpha6beta4-dependent membrane ruffling, lamellae formation, and migration. In contrast, expression of a dominant negative Rac (N17Rac1) had no effect on these processes. Using the Rhotekin binding assay to assess RhoA activation, we observed that engagement of alpha6beta4 by either antibody-mediated clustering or laminin attachment resulted in a two- to threefold increase in RhoA activation, compared with cells maintained in suspension or plated on collagen. Antibody-mediated clustering of beta1 integrins, however, actually suppressed Rho A activation. The alpha6beta4-mediated interaction of clone A cells with laminin promoted the translocation of RhoA from the cytosol to membrane ruffles at the edges of lamellae and promoted its colocalization with beta1 integrins, as assessed by immunofluorescence microscopy. In addition, RhoA translocation was blocked by inhibiting phosphodiesterase activity and enhanced by inhibiting the activity of cAMP-dependent protein kinase. Together, these results establish a specific integrin-mediated pathway of RhoA activation that is regulated by cAMP and that functions in lamellae formation and migration.

Structural studies of initial lymphatics adjacent to gastric and colonic malignant neoplasms

Invasion and metastases are the main causes of death from cancer, and prognosis is best correlated with invasion of malignant cells into initial lymphatics and dissemination to regional lymph nodes. Using both light and transmission electron microscopy, we examined human gastric and colonic cancers and their relation to initial lymphatics. Invasion of malignant tumor cells into the initial lymphatics was characterized by interdigitating and overlapping endothelium giving way to open junctions as lymphatic endothelial cells were apparently dissolved and destroyed. Cytoplasmic vesicles, mitochondria, and rough endoplasmic reticulum were qualitatively increased as demonstrated by image analysis.

Impairment of peroxisomal biogenesis in human colon carcinoma

Peroxisomes and the activities of their enzymes have been reported to be significantly reduced in various types of tumors including the colon carcinoma. Therefore, the present study was designed to investigate the gene expression of several peroxisomal proteins in human colon carcinoma and additionally those of the peroxisome proliferator activated receptor alpha (PPARalpha) and PEX5, a receptor protein involved in the import of most peroxisomal matrix proteins. Samples from adenocarcinomas and adjacent normal colon were analyzed by immunohistochemistry and western blotting. The mRNA content was assessed by a novel sensitive dot blot RNase protection assay and northern blotting. By immunohistochemistry, peroxisomes were distinctly visualized in normal colonocytes but were not detected in colon carcinoma cells. The protein levels of catalase (CAT), acyl-CoA oxidase as well as the 22 and 70 kDa peroxisomal membrane proteins (PMP22 and PMP70) were all significantly decreased in carcinomas. The corresponding mRNAs for CAT and PMP70, however, were unchanged. In contrast, the mRNA of PEX5 was significantly increased. The expression of PPARalpha was not altered in tumors, neither at protein nor mRNA levels. These observations show that the reduction of peroxisomes and their proteins in colon carcinoma is not due to a generalized reduction of transcription of their genes. It seems more likely that this phenomenon is regulated at a post-transcriptional or translational level. Alternatively, and more likely, an impairment of the biogenesis of the organelle could account for the paucity of peroxisomes in colon carcinoma.

Prognostic value of nuclear morphometry in colorectal cancer

PURPOSE

In many types of cancer, certain morphometric characteristic of tumor cells correlate with patient survival. Our observations suggested that the survival of patients with colorectal carcinomas is negatively correlated with tumor-cell nucleus size.

METHODS

We investigated relationships between postsurgery survival and nucleus morphometrics in 90 patients who had undergone resection for a colorectal tumor. The nucleus-size variables considered were maximum diameter, minimum diameter, perimeter, area, and form factor (means for 100 nuclei from each patient were used in all cases).

RESULTS

Our results confirmed that patients with large maximum nucleus diameter (where large = greater than the first quartile) have significantly worse survival than patients with smaller maximum nucleus diameter (mean survival, 28 vs. 43 months). Similar results were obtained for the other nucleus-size variables. Stepwise Cox regression analysis was then performed, with postsurgery survival time as the dependent variable and the following candidate independent variables: age, gender, Dukes class, degree of histologic differentiation, the various nucleus-size variables, and relative frequencies of different nucleus shapes (spherical, oval, cylindrical, fusiform, and irregular). The variables selected for the prognostic model were Dukes class, relative frequency of irregular nuclei, and maximum nucleus diameter.

CONCLUSIONS

These findings indicated that nucleus size and shape are useful predictors of survival. Even if Dukes class is known, consideration of nucleus size and shape significantly improves prediction of survival.

[The standardized techniques for preparing samples used in pathologic diagnostic transmission electron microscopy]

Transmission electron microscopy (TEM) has been used widespreadly in the field of diagnostic pathology. Based on the practical domestic condition and aimed at fully satisfying the needs of the pathologic diagnostic TEM, a set of standardized techniques were established for preparing different kinds of samples. The techniques included the preparation and storage of fixatives and embedding media, the requirement of sampling, the 5 h and 24 h embedding procedures for fresh specimens, the embedding procedure for suspension specimens and specimens collected from fine needle aspiration biopsy, as well as the procedures for preparing samples taken from paraffin embedded blocks or paraffin sections. In practical use, we found that the advantage of these techniques was that the ultrastructures of the tissues and cells were well preserved and they perfectly met the needs for diagnosis of tumors, kidney diseases, et al. The main points of the standardized techniques have been discussed in detail in this paper.

[Malignant stromal tumor of the transverse colon. Case report]

OBJECTIVE

Case report of a malignant stromal tumor of the transverse colon.

BACKGROUND

Colon sarcomas are rare; the most frequent presentation is the leiomyosarcoma. Forty five cases of malignant stromal tumor have been reported in the international literature. The histogenesis of these mesenchymatous neoplasms is determined by ultrastructural analysis and immunohistochemical stains, nevertheless when special techniques are negative and there is uncertainty related to the cellular differentiation line (smooth muscle, neural or undifferentiated) it is preferable to call them stromal tumors of gastrointestinal tract.

METHOD

A 46 year old patient with the diagnosis of malignant stromal tumor of transverse colon and the prescribed treatment was reported.

RESULTS

A case of a patient with the diagnosis of malignant stromal tumor in transverse colon is presented, who had as the main clinical features abdominal pain, transanal hemorrhage and finally intestinal occlusion. He was submitted to exploratory laparotomy finding a transverse colon intussusception, which was treated with an extended right hemicolectomy and a post surgical satisfactory recovery. Follow-up to three years hasn't found tumoral activity.

CONCLUSIONS

Stromal tumors are rare in colon, treatment is a wide surgical resection with curative or palliative purposes.

Differentiation of a colon cancer cell line on a reconstituted basement membrane in vitro

Basement membrane, a thin extracellular matrix, functions as a tissue stabilizer that promotes tissue integrity and differentiated phenotype. We studied a human colon cancer cell line, SNU 61, to evaluate its ability to differentiate on basement membrane. Cells were cultured on plastic, reconstituted basement membrane (Matrigel) or polyhydroxyethyl methacrylate (poly HEMA) for 72 h and evaluated by light and electron microscopy. On Matrigel, the cells showed gland formation with highly polarized cells containing basal nuclei and well developed brush border microvilli on the luminal surface. Apoptosis was noted mainly at the luminal side. On electron microscopic examination, numerous long microvilli, abundant cytoplasmic organelles and intercellular junctions were noted in the Matrigel-cultured cells. Intermediate cytoskeletons were scattered in the cytoplasm and existed on the axes of microvilli. Junctional complexes and desmosomes were frequently formed along intercellular spaces. The cells cultured on poly HEMA, on the other hand, were poorly differentiated and contained a few glandular structures with small lumens. Brush border microvilli, characteristic of enterocytic differentiation, were few in number and were developed on the basal surface. Intermediate filaments and microtubules were fewer than in the Matrigel-cultured cells. Carcinoembryonic antigen was expressed on the luminal surface of the Matrigel-cultured cells and in the cytoplasm of the poly HEMA cultured cells. CD44 stained the basolateral surface in the Matrigel-cultured cells, but the basal side was not stained in the poly HEMA cultured cells. These results are consistent with the different localization of microvilli in the Matrigel and in the poly HEMA cultured cells. Our observations suggest that human colon cancer cells on basement membrane can undergo glandular differentiation and that extracellular matrix is an important factor in morphogenesis.

Sodium butyrate induces retinoblastoma protein dephosphorylation, p16 expression and growth arrest of colon cancer cells

Sodium butyrate causes alteration of colon cancer cell morphology and biology towards that of a more differentiated phenotype. The retinoblastoma gene encodes a nuclear phosphoprotein (pRb) present in a wide range of human cancer cell lines including colon cancer cell lines. pRB is synthesized throughout the cell cycle and phosphorylated in a phase specific manner: the predominant proteins in G0/G1 are the unphosphorylated species (110 kD) whereas phosphorylated pRb (112-114 kD) are in S and G2. 110 kD pRb binds transcription factors and prevents transcription of responsive genes such as the gene for thymidine kinase, which are expressed in late G1. The precise mechanisms controlling cell arrest are unknown, but recent data suggest that cyclin-dependent kinase inhibitors such as p16 may play a role. The aim of the present study was to assess the effect of sodium butyrate on cell cycle staging, thymidine kinase activity, phosphorylation of the pRb protein and expression of p16. We show that sodium butyrate treatment induces differentiation of LS174T colon cancer cells, inhibits thymidine kinase activity concomitantly with induction of pRb dephosphorylation, p16 transcription and cell cycle arrest at G0/G1. Initial dephosphorylation was observed 24 h after treatment of LS174T cells with sodium butyrate, whereas complete shift to the dephosphorylated form was observed 3 days after treatment. Induction of pRb dephosphorylation by sodium butyrate preceded inhibition of growth and the specific cell cycle arrest. RNase protection assay with a p16 specific riboprobe showed undetectable levels in proliferating cells to several fold increase in differentiated colonocytes. In conclusion, the results provide evidence for a specific cellular mechanism of butyrate induced growth arrest and differentiation of a colon cancer cell line.

Isolated extracellular matrix-based three-dimensional in vitro models to study orthotopically cancer cell infiltration and invasion

An initial event in colon cancer progression is the migration of epithelial cells through the basement membrane (BM) and the invasion of the colon submucosa, where tumour cells enter blood and lymph vessels to spread throughout the body. To interrupt this process would mean the prevention of metastasis. In order to investigate tumour cell invasion orthotopically in the human system, we established novel in vitro models which mimic normal human colon tissue (colon reproductions, CoRes) and primary colon carcinomas (artificial tumours, ArTs). These models are based on the isolated extracellular matrix (iECM) of the respective human tissues. Two isolation methods were established, the Digestion Method and the Lysis Method neither of which destroyed the characteristic architecture of the ECM found in the original tissues. BM components, i.e. laminin, fibronectin and collagen IV, were detectable in the iECM isolated with the Lysis Method but not those isolated with the Digestion Method. Scanning electron microscopic analysis of the normal colon iECM demonstrated that even if the BM was missing, the luminal surface consisted of densely packed ECM filaments which do not allow cell infiltration without degradation of the iECM. Furthermore, we demonstrated that iECM can be separately supplemented with different cell types, i.e. colorectal carcinoma cells, normal fibroblasts and immune cells at any desired concentration, combination and localisation. Therefore, these models could be used to determine the role of the BM and of the tumour cell/normal cell crosstalk in the infiltration process of human colorectal carcinoma cells.

De novo synthesis of arginine and ornithine from citrulline in human colon carcinoma cells: metabolic fate of L-ornithine

In human colon carcinoma cells (HT-29 cells), L-arginine is the common precursor of L-ornithine which generates polyamines strictly necessary for cellular growth, and nitric oxide which has a strong antiproliferative activity. We show here that proliferative HT-29 cells possess the capacity for de novo synthesis of L-arginine from L-citrulline, but not from L-ornithine. L-Ornithine is apparently not an L-arginine precursor due to the absence of any detectable ornithine carbamoyltransferase activity. In contrast, the newly synthesized L-arginine was competent for urea and thus L-ornithine production in a context of a high putrescine production in the ornithine decarboxylase pathway and a low degradation of this polyamine in the diamine oxidase pathway. However, cells grown in an arginine-free culture medium containing added L-citrulline were unable to reach confluency. Furthermore, the low amount of nitric oxide produced from L-arginine by these cells was apparently not involved in the control of cell growth since inhibition of nitric oxide synthase activity was without effect. On the other hand, the capacity of more differentiated and less proliferative HT-29 cells for de novo L-arginine synthesis from L-citrulline was increased. It is concluded that L-citrulline is a precursor of L-arginine and L-ornithine in proliferative HT-29 cells and that the metabolic fate of L-ornithine in these cells is mainly devoted to polyamine synthesis. The similarity between differentiated HT-29 cells and the enterocytes of newborn animals in terms of L-arginine metabolism is finally discussed.

Differential Hsp70 plasma-membrane expression on primary human tumors and metastases in mice with severe combined immunodeficiency

To study the role of cell-surface expression of a tumor-selective heat-shock protein 70 (Hsp70) in vivo, the colon-carcinoma cell line CX2, and the clonal sub-lines CX+ and CX-, which differ in Hsp70 cell-surface expression, but not in MHC and adhesion-molecule expression, were implanted into immunodeficient SCID/beige mice by s.c., i.p., i.v. and orthotopic (o.t.) inoculation. On day 18 after s.c. injection, all animals developed s.c. tumors, ranging in size from 2.5 to 3 cm2. Phenotypic characterization of single-cell suspensions generated from freshly isolated tumor material revealed that the pattern of cell-surface expression is identical to that of the injected tumor cells from cell culture. Comparable results were obtained following i.p. inoculation of CX+ and CX- cells. Macroscopic and microscopic evaluation of lymph nodes, lung, liver and spleen at autopsy of tumor-bearing mice showed no tumor burden except the primary tumor, following s.c. or i.p. injection. After i.v. inoculation of CX+ and of CX- cells, weak tumor growth was observed in lung and liver, the Hsp70 cell-surface-expression pattern on these tumors being identical to that of the injected cells. However, o.t. injection of colon-carcinoma cell lines CX+ and CX- into the cecum resulted in tumor growth at the injection site and in spread of distant metastases in lung, liver and spleen. Most interestingly, and in contrast to the primary colon carcinomas, metastases of CX+ and of CX- tumor cells both revealed strong Hsp70 plasma-membrane expression, although the total amount of cytoplasmic Hsp70 was comparable.

Lung adenocarcinomas metastatic to the brain with and without ultrastructural evidence of rootlets: an electron microscopic and immunohistochemical study using cytokeratins 7 and 20 and villin

Adenocarcinomas metastatic to brain from lung or colon may pose differentiation difficulties. Ultrastructurally, both may have brush borders with rootlets. This study examines the ultrastructural morphology and immunohistochemical expression of villin (associated with rootlets), cytokeratin 7 (present in lung adenocarcinomas), and cytokeratin 20 (present in colon adenocarcinomas) in 19 formalin-fixed sequential surgical biopsies of lung adenocarcinomas metastatic to brain as compared to 13 colonic adenocarcinoma metastases. Of lung tumor metastases, mucinous differentiation with rootlets was most common [6/19(32%)]. All colon tumor metastases were cytokeratin 7(-), 20(+), and profusely villin(+). Well-formed rootlets were seen. All lung metastases were cytokeratin 7(+) and 20(-). 5/6(83%) lung metastases with rootlets were focally villin(+). 12/13(95%) without rootlets were villin(-). Rootlets are extremely common in lung adenocarcinoma metastatic to brain. Villin immunoreactivity closely correlates with rootlets. Its distribution is a useful adjunct to cytokeratin 7 and 20 in differentiation of lung versus colon adenocarcinomas metastatic to the brain.

Scanning electron microscopy of aberrant crypt foci in human colorectal mucosa

BACKGROUND

Aberrant crypt foci (ACF) are clusters of morphologically altered crypts which can be observed by light or stereomicroscopy on the mucosal surface of the colon after staining with methylene-blue. They probably represent one of the earliest events in human colorectal carcinogenesis. The main purpose of the present study was to observe the surface features of aberrant and normal colonic crypts in humans using scanning electron microscopy (SEM) in order to find and measure differences between aberrant and normal.

MATERIALS AND METHODS

Fifteen mucosal specimens containing ACF and 8 with normal mucosa taken from patients operated on for colon cancer were observed under a scanning electron microscope.

RESULTS

By SEM ACF were easily observed on the mucosal surface, because they showed a well defined border and were elevated on the mucosal surface. Under higher magnification luminal openings of aberrant crypts had a larger overall average diameter than normal (37.6 microns +/- 13.5, mean +/- SD, vs 15.9 microns +/- 4.9, P = 0.001), though when crypt multiplicity of ACF (number of crypts per ACF) was higher, the diameter of luminal openings tended to be smaller and similar to those of normal crypts, with weak negative correlation between crypt multiplicity of ACF and mean diameter of aberrant luminal openings (r = 0.27). Finally, the mucosal surface among aberrant crypts was flattened because of a loss of microvilli. in conclusion, scanning electron microscopy allows a better definition of the topological features of aberrant crypt foci than light or stereomicroscopy.

Exogenous thrombospondin stimulates the proliferation of non-thrombospondin-producing cells

The effects of thrombospondin (TSP) on the proliferation of two different human carcinoma cell lines (KIM-1 and CW-2) were investigated. The characterization of these two carcinoma cells by immunohistochemistry using anti-TSP antibody and anti-TSP-receptor antibody showed that the KIM-1 had TSP-receptors and TSP, while the CW-2 had only TSP-receptors. The addition of exogenous TSP (10 or 20 microg/ml) to culture medium stimulated the cell proliferation of CW-2 but not that of KIM-1. The cell count for CW-2 was increased dosage-dependently from 10.3 0.6x104/ml at zero TSP concentration to 12.9 0.6x104/ml at 10 microg/ml TSP concentration and to 14.7 0. 4x104/ml at 20 microg/ml TSP (each p<0.0001). In conclusion, though TSP promoted the proliferation of non-TSP-producing cells, it did not promote proliferation of TSP-producing cells. Therefore, it is predicted that TSP was already at saturated activity concentration in the TSP-producing cell line (KIM-1).

A comparative study of nucleolar organizer region, proliferating cell nuclear antigen and epidermal growth factor receptor staining in colon tumours

Several studies have reported that proliferating cell nuclear antigen (PCNA), nucleolar organizer regions (NOR) and epidermal growth factor receptor (EGF-R) are cellular proliferation parameters in malignant tumours. However, the correlation of EGF-R with PCNA and NOR has not been reported in colon tumours. To clarify this, we investigated the correlation of the expression of EGF-R with PCNA and NOR in colonic epithelial tumours. Using immunohistochemical staining and one-step silver staining techniques, the expressions of EGF-R-, PCNA- and NOR-associated protein were studied in paraffin sections from five normal mucosae, 10 adenomas with mild atypia, 16 adenomas with moderate atypia, 32 adenomas with severe atypia including carcinoma in situ and 47 with invasive colon carcinomas. Significant differences were found among the respective degrees of atypia in Ag-NOR counts, PCNA labelling index (LI), and the expression of EGF-R. However, there were no significant differences among the Ag-NOR counts of the severe atypia and invasive carcinoma. There was a significant positive correlation between Ag-NOR counts and PCNA LI (P < 0.001). The Ag-NOR counts and PCNA LI in EGF-R-positive cases were higher than in EGF-R-negative cases (P < 0.001). These results indicate that each of the parameters increased significantly with the increase in atypia and the progression of cancer. Epidermal growth factor receptor provokes an exacerbation of protein synthesis and the cell cycle in colonic epithelial tumours.

New isolation technique to study apoptosis in human intestinal epithelial cells

Intestinal epithelial cells derive from stem cells at the base of the crypt and migrate along the crypt-lumen axis. Their life is terminated as they reach the luminal surface where they detach and are shed. Intestinal epithelial cells show evidence of apoptosis in the region of shedding, and cell death is thought to resemble a form of apoptosis called detachment-induced cell death, or anoikis. Human intestinal epithelial cells die rapidly in vitro due to loss of anchorage during isolation, making primary culture of these cells a goal that has not yet been reached. However, the molecular mechanisms underlying this process of anoikis are largely unknown. In this study, a novel protocol for the rapid, temperature-controlled isolation of highly purified human colonic epithelial cells from surgical specimens is described. Using this method, early molecular events of anoikis in nontransformed epithelial cells were studied. Intestinal epithelial cells were isolated at the beginning of the apoptotic cascade, before the activation of caspase 3 family members and cleavage of poly(ADP-ribose) polymerase and DNA fragmentation. Elucidating the molecular mechanisms of detachment-induced cell death may facilitate the establishment of long-term primary cultures of human intestinal epithelial cells and enhance our understanding of homeostasis in the intestinal epithelium.

Recombinant immunocytokines targeting the mouse transferrin receptor: construction and biological activities

Localized cytokine therapies with recombinant monoclonal antibody-cytokine fusion proteins, designated immunocytokines, have become of increasing interest for tumor immunotherapy, since they direct immunomodulatory cytokines into the tumor microenvironment. To investigate their mechanisms of action in a variety of syngeneic tumor models, recombinant mouse cytokines IL2 and GM-CSF were engineered as fusion proteins to the carboxyl terminus of a chimeric rat/mouse antitransferrin receptor antibody, ch17217 and expressed in stable-transfected Chinese hamster ovary cells. The recombinant immunocytokines were readily purified by affinity chromatography and their binding characteristics were identical to those shown for the ch17217 antibody. The IL2 immunocytokine had an activity similar to recombinant mouse IL2, whereas the GM-CSF immunocytokine had enhanced cytokine activity relative to recombinant mouse GM-CSF. The clearance rates of ch17217 and the GM-CSF and IL2 immunocytokines were relatively similar with elimination phases (t1/2alpha) of 1.8 h and distribution phases (t1/2beta) of 83, 88, and 91 h, respectively. Both immunocytokines demonstrated effective antitumor activity by suppressing the growth of hepatic metastases of mouse neuroblastoma and pulmonary metastases of mouse colon carcinoma in syngeneic A/J and BALB/c mice, respectively. These results indicate that biologically effective IL2 and GM-CSF immunocytokines combine the targeting ability of an antitransferrin receptor monoclonal antibody with the immunomodulatory functions of each cytokine. Because of the universal expression of the transferrin receptor on mouse tumor cell lines, these constructs should prove useful to determine their efficacy in a wide variety of syngeneic mouse tumor models and to perform detailed studies of their modes of action.

Imaging surface and submembranous structures with the atomic force microscope: a study on living cancer cells, fibroblasts and macrophages

Atomic force microscopy (AFM) has been used to image a wide variety of cells. Fixed and dried-coated, wet-fixed or living cells were investigated. The major advantage of AFM over SEM is the avoidance of vacuum and electrons, whereas imaging can be done at environmental pressure and in aqueous conditions. Evidence of the successful application of AFM in biological imaging is provided by comparing results of AFM with SEM and/or TEM. In this study, we investigated surface and submembranous structures of living and glutaraldehyde-fixed colon carcinoma cells, skin fibroblasts and liver macrophages by AFM. Special attention was paid to the correct conditions for the acquisition of images of the surface of these cells, because quality SEM examinations have already been abundantly presented. AFM imaging of living cells revealed specific structures, such as the cytoskeleton, which were not observed by SEM. Membrane structures, such as ruffles, lamellipodia, microspikes and microvilli, could only clearly be observed after fixing the cells with 0.1% glutaraldehyde. AFM images of living cells were comparable to SEM images of fixed, dried and coated cells, but contained a number of artefacts due to tip-sample interaction. In addition, AFM imaging allowed the visualization of cytoplasmic submembranous structures without the necessity for further preparative steps, allowing us: (i) to follow cytoskeletal changes in fibroblasts under the influence of the microfilament disrupting agent latrunculin A; (ii) to study particle phagocytosis in macrophages. Therefore, in spite of the slow image acquisition of the AFM, the instrument can be used for high-resolution real-time studies of dynamic changes in submembranous structures.

Heterogeneous induction of apoptosis in colon cancer cells by wild-type p53 gene transfection

To examine the effects of wild-type (wt)-p53 gene transfer on cancer cell growth and apoptosis induction, we transduced human wt-p53 cDNA into three colon cancer cell lines either with or without a mutation of the p53 gene using the HVJ-cationic liposome method. Wt-p53 gene transfer, thus, induced an apparent growth arrest in all cell lines, but its enhancement of the apoptotic rate varied (from about 4 to 70 times). The simultaneous doxorubicin treatment was able to enhance growth arrest and the apoptosis induction rate. These findings suggest that wt-p53 gene transfer using HVJ-cationic liposomes seems to be a potentially effective therapeutic strategy, however wt-p53 gene transfer still appears to be more effective in combination with other cytotoxic treatments.

Intestinal plasmacytoma in an African hedgehog

A 3-yr-old male African hedgehog (Atelerix albiventris) had anorexia and weight loss for 1 wk before its death. The colon and mesocolon were diffusely infiltrated by a neoplastic proliferation of round cells with plasmacytoid features. A diagnosis of intestinal plasmacytoma was made and confirmed by electron microscopy. No other organs appeared to be affected. This is the first description of intestinal plasmacytoma in a hedgehog.

Atypical microtubule organization in undifferentiated human colon cancer cells

We previously reported that undifferentiated colonic cancer HT-29 cells, unlike the differentiated ones, exhibit unusual organelle distributions and atypical vesicle trafficking patterns, which are microtubule-independent and microfilament-dependent. In the present study, we have analyzed the microtubule network in both phenotypes, using confocal microscopy, and determined the expression levels of some microtubule-associated proteins by quantitative immunoblotting. Differentiated cells exhibited the microtubular organization of polarized epithelial cells. Non-polarized undifferentiated cells presented an atypical microtubule organization as microtubules were localized mainly at the cell 'top'. Immunoblot analysis indicated the absence or low content of several structural and motor microtubule-associated proteins in undifferentiated cells, compared to differentiated cells. This may explain in part their atypical microtubular organization. This study agrees with a crucial role for microfilaments in the intracellular organization of undifferentiated HT-29 cancer cells, while differentiated HT-29 cells exhibit intracellular organization similar to that of normal enterocytic cells, although they are also tumoral.

Ultrastructure of hepatic metastases from a colon leiomyosarcoma

The electron microscopic examination of biopsies from liver metastases of a colon leiomyosarcoma showed the existence of alterations not previously reported in primary tumors of that kind. Those abnormalities included proliferation of lysosomal structures as multivesicular bodies, myelin-like figures, lipofuscin granules and autophagic vacuoles, along with mitochondrial changes as concentric and vesiculated cristae, and presence of dense granules and elongated inclusions. This study suggests that, in this tumor and host tissue, the so-called invasive phenotype, which is supposed to form the metastases, could have a distinct morphological picture at the ultrastructural level.

The microtubule-stabilizing agent discodermolide competitively inhibits the binding of paclitaxel (Taxol) to tubulin polymers, enhances tubulin nucleation reactions more potently than paclitaxel, and inhibits the growth of paclitaxel-resistant cells

The lactone-bearing polyhydroxylated alkatetraene (+)-discodermolide, which was isolated from the sponge Discodermia dissoluta, induces the polymerization of purified tubulin with and without microtubule-associated proteins or GTP, and the polymers formed are stable to cold and calcium. These effects are similar to those of paclitaxel (Taxol), but discodermolide is more potent. We confirmed that these properties represent hypernucleation phenomena; we obtained lower tubulin critical concentrations and shorter polymers with discodermolide than paclitaxel under a variety of reaction conditions. Furthermore, we demonstrated that discodermolide is a competitive inhibitor with [3H]paclitaxel in binding to tubulin polymer, with an apparent Ki value of 0.4 microM. Multidrug-resistant human colon and ovarian carcinoma cells overexpressing P-glycoprotein, which are 900- and 2800-fold resistant to paclitaxel, respectively, relative to the parental lines, retained significant sensitivity to discodermolide (25- and 89-fold more resistant relative to the parental lines). Ovarian carcinoma cells that are 20-30-fold more resistant to paclitaxel than the parental line on the basis of expression of altered beta-tubulin polypeptides retained nearly complete sensitivity to discodermolide. The effects of discodermolide on the reorganization of the microtubules of Potorous tridactylis kidney epithelial cells were examined at different times. Intracellular microtubules were reorganized into bundles in interphase cells much more rapidly after discodermolide treatment compared with paclitaxel treatment. A variety of spindle aberrations were observed after treatment with both drugs. The proportions of the different types of aberration were different for the two drugs and changed with the length of drug treatment.

Immunodetection of epithelial mucin (MUC1, MUC3) and mucin-associated glycotopes (TF, Tn, and sialosyl-Tn) in benign and malignant lesions of colonic epithelium: apolar localization corresponds to malignant transformation

Epithelial mucins are present at the apical membranes of gastrointestinal epithelial cells or in their secretions. In this study, we examined the occurrence of peptide epitopes of the mucins MUC1 and MUC3 and of three mucin-associated glycotopes (TF, Tn, and s-Tn) in a series of colorectal tissue samples (normal colon, adenomas with different grades of dysplasia, carcinoma in situ, and invasive carcinomas). A new monoclonal antibody to a conformation-dependent peptide epitope of MUC1 was employed, which does not react with the fully glycosylated mucin as found in normal gastrointestinal mucosa. We found that adenomas acquired the ability to expose Tn, s-Tn, TF and MUC1 epitopes, and this correlated with increasing malignant potential. The secretory mucin, MUC3, revealed a different pattern: it was detectable in all sections, with maximum expression in adenomas and decrease in carcinomas. Most importantly, normal mucosa and benign lesions showed supra-nuclear and/or apical distribution of these antigens, but malignant lesions and lesions with a very high risk of malignancy revealed diffuse cytoplasmic and basolateral membrane localization. The immunohistological response to a combination of MUC1-related antibodies may assist in assessing the malignant potential and status of lesions of the colon.

Postoperative delirium easily develops in patients with intramitochondrial inclusion bodies in colonic neurons

Patients whose colons were resected for carcinoma were studied in order to determine the relationship between clinical findings-which included development of postoperative delirium- and intramitochondrial inclusion bodies (MI) in the neurons in the colon. Twenty-three patients had MI and 24 patients did not. Preoperative dementia was present in 9 (39.1%) of the 23 patients with MI, and in 7 (29.2%) of the 24 without it. Postoperative delirium developed in 13 (56.3%) of the 23 with MI, and in 5 (20.8%) of the 24 without it (p < 0.05). Excluding preoperative dementia, postoperative delirium developed in 5 (35.7%) of the 14 with MI, and in none of the 17 without it. Changes in the neurons in the colon were not related to dementia. The changes may have been related to the functions of the central nervous system, because patients with MI were likely to develop postoperative delirium.

The AgNoR count in ulcerative colitis with and without dysplasia

The numbers of specific intranuclear AgNOR silver precipitates (AgNORs) and their relation to the Inflammatory Bowel Disease-Dysplasia Morphology Study Group's classification were studied in 134 colonscopic biopsy specimens of ulcerative colitis (UC) with and without dysplastic findings from 73 patients with active and inactive disease. In addition, 40 cases of colonic adenocarcinomas and 22 normal colonic mucosae were also assessed for comparison with the one-step silver staining AgNOR technique. Statistical comparison of the mean AgNOR number revealed a highly significant inter-class difference (P < 0.001) between UC without dysplasia and UC with dysplasia as well as between active and inactive UC. On the contrary, the AgNORs count did not separate colonic adenocarcinomas from UC with dysplasia either high or low grade nor these three classes from the group of UC with indefinite dysplasia. The quantitative evaluation of epithelial changes occurring in UC by the AgNOR method may help to establish the clinical management of colitis patients, in addition to qualitative morphological criteria.

Formation of spheroid structures in a human colon carcinoma cell line involves a complex series of intercellular rearrangements

The structural remodelling of tissues that occurs in vivo during animal morphogenesis can often prove difficult to study. Here we investigate the organizational processes of the LIM 1863 colon carcinoma cell line as it transforms from a single-cell stage into multicellular spherical structures called 'organoids'. The organoids can be dissociated into a viable single-cell suspension when cultured in calcium-depleted medium, and then induced to reform the organoid structure by the readdition of calcium. Previous studies have shown that initial cell attachment under these conditions is characterized by a novel mechanism of cell engulfment termed 'clutching'. This investigation reveals the subsequent appearance of junctional complexes between groups of 'clutched' cells prior to lumen formation, and the ultimate 'declutching' of entrapped cells as a means of cell rearrangement. Intact actin filaments but not microtubules were required for the initial clutching events, while inhibition of microtubule polymerization resulted in aberrant apical protein polarization, but did not affect the development of a luminal space within the spheroids. Single cells exhibited pools of intracellular microvilli contained in vacuolar apical compartments, which were resistant to the effects of cytoskeleton-disrupting drugs. However, these structures did not seem to be responsible for the swift development of the luminal surface observed in these cells. Two other cell lines, MDCK and DU 4475, were found to exhibit similar clutching conformations when induced to form three-dimensional structures, suggesting that this may be a widespread mechanism of cell rearrangement that reflects the process of organ morphogenesis in vivo.

Cytotoxic effect of cytokines on murine colon carcinoma cells involves TNF-mediated apoptosis

We have studied the cytotoxic effect of TNF-alpha on C-26 murine colon carcinoma cells in vitro. Treatment with TNF-alpha alone did not result in any demonstrable cytotoxicity. However, when combined with IFN-gamma, the cytotoxic effect of TNF-alpha was enhanced in a dose-dependent manner. An agonistic TNF-R1 specific antibody and recombinant human TNF-alpha both exerted a cytotoxic effect when combined with IFN-gamma, suggesting that the cytotoxicity was mediated through the TNF-R1. The cytotoxicity was associated with production of nitric oxide without any direct involvement in the cytotoxic effect. At the ultrastructural level, treated cells displayed a typical apoptotic morphology which was not accompanied by internucleosomal cleavage of DNA as shown by conventional electrophoresis.

Mutation analysis of coding sequences of the entire transforming growth factor beta type II receptor gene in sporadic human colon cancer using genomic DNA and intron primers

Mutations in the transforming growth factor beta type II receptor (TGFbeta RII) gene have been detected in several human cancers exhibiting microsatellite instability. To extend analyses of this gene, we previously investigated the exon-intron organization of the TGFbeta RII gene and defined seven exons and flanking intron sequences. In this study, we further determined the nucleotide sequences surrounding these seven exons and designed eight sets of intron-based primers to examine the entire coding region of the TGFbeta RII gene. Using these primers, we screened genomic DNA sequences from 30 sporadic colorectal cancers for mutations of the TGFbeta RII gene. TGFbeta RII mutations were detected in two of 30 tumors and both displayed microsatellite instability. One had a deletion in a polyadenine tract in exon 3 and the other had a point mutation in the kinase domain located in exon 7. There were no mutations in exons 1, 2, 4, 5 and 6. These results further implicate the polyadenine tract and kinase domain as mutational hotspots in the TGFbeta RII gene in cells with genomic instability and suggest that TGFbeta RII gene mutations occur rarely in cells lacking genomic instability.

Antiproliferative activity in vitro and in vivo of the spicamycin analogue KRN5500 with altered glycoprotein expression in vitro

The spicamycin analogue KRN5500 (NSC 650426; SPA) is derived from Streptomyces alanosinicus. The unique structure contains a purine, an aminoheptose sugar, glycine, and a tetradecadiene fatty acid. SPA potently inhibits the growth of certain human tumor cell lines in vitro (IC50 for growth <100 nM) and displays marked activity in vivo in Colo 205 colon carcinoma xenografts. Selective inhibition of labeled precursor incorporation was not evident at 1 or 4 h of exposure to the drug, but at 8 h, [3H] leucine incorporation was inhibited by approximately 40% at or below the IC50 for cell growth. Because of the structural similarity of SPA to inhibitors of glycoprotein processing, we examined the effect of SPA on indicators of glycoprotein synthesis and processing in HL60TB promyelocytic leukemia and Colo 205 colon carcinoma cells. Brief periods of exposure ( approximately 30 min) to SPA at the IC50 for growth increased incorporation of [3H]mannose. When examined by Western blotting after prolonged (40-48 h) incubation with lectins that target mannose-containing carbohydrates, Galanthus nivalis agglutinin and concanavalin A, a qualitative change in the pattern of mannose-containing glycoproteins was observed in HL60TB cells. Significant changes in the pattern of surface glycoprotein expression in intact cells were demonstrated by flow cytometry using fluorescence-labeled lectins. An increase in the number of cells binding G. nivalis agglutinin (indicating terminal mannose) was noted, but a decrease in the amount of lectin bound per cell was noted for wheat germ agglutinin (detecting sialic acid and terminal beta-N-acetyl glucosamine residues). Electron microscopy revealed loss of microvilli, and the Golgi apparatus appeared inflated. Our findings, therefore, raise the possibility that cells exposed to SPA have altered glycoprotein processing after exposure to low concentrations of drug, prior to the occurrence of overt cytotoxicity. These effects are consistent with a prominent early effect of SPA on the enzymatic machinery or organelles important for proper glycoprotein processing and emphasize the novelty of this agent's likely mechanism of action.

PTHrP and the PTH/PTHrP receptor are co-expressed in human breast and colon tumours

Using RNA extracted from human tumour samples removed during surgery, we have analysed expression of mRNA for parathyroid hormone-related protein (PTHrP) and for the PTH/PTHrP receptor by RT-PCR in a panel of human breast and colon tumours. All but 1 of 18 breast tumour samples expressed PTHrP, whereas receptor expression was detected in 11 of these. Expression of the PTH/PTHrP receptor was found in three out of four metastatic lesions, including one sample in which no receptor was detected in the primary tumour. PTHrP expression was also detected in five colon tumours, and receptor expression detected in two of these. These results demonstrate that PTHrP and the PTHrP receptor are also co-expressed in breast tumours in vivo and provide further evidence that PTHrP may be an important autocrine/paracrine growth factor in breast cancer.

Small cell undifferentiated carcinoma of the colon associated with hepatocellular carcinoma in an immunodeficient patient

Small cell undifferentiated carcinoma (oat cell carcinoma) is a malignant epithelial neoplasm with neuroendocrine features. It can appear as a primary tumor in many organs besides the lung, including the colon. We report a case of primary small cell undifferentiated carcinoma of the left colon with omental metastases in a 23-year-old man with a history of X-linked hyper-IgM syndrome. The patient had a simultaneous primary hepatocellular carcinoma. A literature review of this rare colonic malignancy is presented together with a discussion of the possible relationship of this tumor with hepatic malignancy and immunodeficiency.

Enhancement of radiation dose to the nucleus by vesicular internalization of iodine-125-labeled A33 monoclonal antibody

In radioimmunotherapy, the emission characteristics of the radioisotope is critical in determining the radiation dose to the tumor compared to normal organs. If antibodies internalize and transport low-energy electron emitting isotopes close to the tumor cell nucleus, an improved therapeutic advantage is achieved.

METHODS

Using fluorescent microscopy, we studied the subcellular distribution of an internalizing antibody, A33, which detects a restricted determinant on colon cancer cells. We developed a physical model to assess the dose deposited on the nucleus by electrons emitted from radiolabeled A33 accumulated inside vesicles. This model is based on the energy-range relationship of electrons in water. Similarly, another model was developed to calculate the radiation dose to the nucleus from electrons emitted from extracellular space. The percentage of A33 bound to membrane and internalized was determined in vitro at various time points. Cytotoxicity experiments were performed with 125I- and 131I-labeled A33 at various concentrations and specific activities.

RESULTS

A33 accumulates in cytoplasmic vesicles (40% of total bound) which transport the activity close to the nucleus. This increases the radiation dose to the cancer cell nucleus by a factor of 3 compared to the average dose calculated based on the assumption of a uniform distribution on the cell membrane. The cytoplasm of antigen-negative normal cells shields the nucleus from the electrons emitted from extracellular 125I. This shielding is 30 times less for 131I. Cytotoxicity data show 10% cell survival with 10 microCi/ml of 125I-A33, but 90% survival with up to 100 micro/Ci/ml of 125I-A33 in the presence of a blocking dose of 100-fold excess of cold A33. Similar experiments with 131I showed cytotoxicity in both cases.

CONCLUSIONS

The results of the cytotoxicity experiment are in agreement with the physical model and suggest a basis for improved tumor-to-marrow radiation dose by clinical use of 125I-A33.

Subcellular localization of docosahexaenoic acid and arachidonic acid omega-hydroxylation activity in the brain, liver and colonic adenocarcinoma

A homogenate of rat brain, rat liver or human colonic well differentiated adenocarcinoma was prepared in 250 mM sucrose isoosmolaric buffer (pH 7.6) and fractionated by differential centrifugation at 10(3), 10(4) and 10(5) g. Each precipitate or supernatant was incubated with NADPH and docosahexaenoic acid or arachidonic acid as a substrate for 30 min at 37 degrees c under aerobic conditions. omega-Hydroxydocosahexaenoic acid or omega-hydroxyeicosatetraenoic acid from an incubation mixture was detected by reversed-phase high-performance liquid chromatography-thermospray mass spectrometry with selected-ion monitoring. omega-Hydroxy polyunsaturated fatty acids were characterized by high intensity of the molecular ion (MH+) although common hydroxy polyunsaturated fatty acids were characterized by high intensity of the MH+ -H2O ion. For the rat brain, omega-hydroxylation activity (the amount of omega-hydroxy product produced in 30 min) was concentrated to a 10(3) g precipitate although the specific activity (the activity per 1 mg of protein) in the 10(3) g precipitate did not indicate superiority over other fractions. However, the specific activity of the rat brain increased on addition of a 10(4) or 10(5) g precipitate. For the rat liver, although omega-hydroxylation activity was concentrated to a 10(3) g precipitate, the specific activity was concentrated to a 10(5) g precipitate and the subcellular localization differed from that of rat brain. In the human colonic well differentiated adenocarcinoma, although omega-hydroxylation activity was relatively high in the 10(3) g supernatant, the specific activity was relatively high in the 10(3) g precipitates. These results suggest that there is a difference regarding subcellular localization of the omega-hydroxylation activity depending on the species of the organs.

Diallyl disulfide induces apoptosis of human colon tumor cells

The present studies compared the effects of various oil-soluble compounds containing allyl and disulfide groups on the proliferation of cultured human colon tumor cells (HCT-15). Diallyl disulfide (DADS) was more effective in inhibiting the growth of HCT-15 cells than isomolar concentrations of S-allyl cysteine, dipropyl disulfide (DPDS), allyl chloride, allyl glycidyl ether and allyl alcohol. These studies clearly demonstrate the importance of both the diallyl and the disulfide groups in DADS. Treatment of HCT-15 cells with 100 microM DADS increased the intracellular calcium levels by 40%, while DPDS caused only a 12% increase in intracellular calcium. Exposure to 100 microM DADS or more, but not DPDS, caused the cells to undergo apoptosis as determined by morphological changes and DNA fragmentation. A positive correlation (r=0.944) was found between DADS-induced DNA fragmentation and its ability to increase intracellular free calcium levels. The widespread effectiveness of DADS was evident by its ability to inhibit the growth of human colon (HCT-15), skin (SK MEL-2) and lung (A549) tumor cell lines.

Co-localization of suramin and serum albumin in lysosomes of suramin-treated human colon cancer cells

Suramin is a polysulfonated compound currently under investigation for the treatment of various types of cancer. Pharmacokinetic studies from clinical trials in humans have shown that most of the circulating drug is associated with serum albumin. The objective of the present study was to investigate the intracellular localization of suramin and serum albumin in human colon cancer cells (HT-29-D4) upon suramin treatment. For this purpose, combined gold labeling and autoradiographic methods were performed on HT-29-D4 cells grown in serum free medium containing both [3H]suramin and colloidal gold-albumin. These morphological experiments demonstrated for the first time that suramin and serum albumin were co-localized in the same cellular compartment (i.e. the lysosomal system) of the suramin-treated HT-29-D4 cells. The albumin-directed targeting of suramin in lysosomes may allow the drug to inhibit the activity of several lysosomal hydrolases, resulting in a lysosomal storage disorder.

Development of colonic and pancreatic endocrine tumours in mice expressing a glucagon-SV40 T antigen transgene

We report the histological, immunohistochemical and ultrastructural changes in mice containing a chimeric glucagon-simian virus 40 T antigen (SV40Tag) gene. Transgene expression was detected in endocrine cells of pancreas, small and large intestine. Hyperplasia of glucagon-containing cells developed in pancreas and large bowel by gestational day 19. In large bowel, hyperplastic cells increased in number postnatally and invasive carcinomas were identified at 4 weeks; several animals had lymph node metastases. In contrast, no pathology was detected in the small bowel in any of the transgenic mice. Colonic tumours expressed SV40Tag, proglucagon-derived peptides and peptide YY (PYY); scattered cells contained cholecystokinin or glycoprotein hormone alpha-subunit. Somatostatin or serotonin was also detected in some tumours. By electron microscopy, the colonic tumours retained features of endocrine differentiation, but secretory granules were smaller than those of non-tumorous intestinal glucagon-producing L cells. In postnatal pancreas, atypical cells containing SV40Tag and glucagon were initially clustered at the periphery of islets; this atypical hyperplasia progressed to neoplasia by 11-12 weeks. Some neoplastic pancreatic cells contained glucagon, PYY or vasoactive intestinal peptide immunopositivity, but most were negative for all peptides; they contained immunoreactivity for tyrosine hydroxylase and by electron microscopy, pancreatic tumour cells had neuronal features. Pancreatic polypeptide was not detected in the non-tumorous islets of transgenic animals. This line of transgenic mice provides a model for the analysis of endocrine tumour progression in the gut and pancreas.

Hypoxic tumor cell death and modulation of endothelial adhesion molecules in the regression of granulocyte colony-stimulating factor-transduced tumors

C-26 colon adenocarcinoma cells transduced with the granulocyte colony-stimulating factor (G-CSF) gene form large tumors when injected into sublethally irradiated mice. These tumors regress when leukocyte function is reconstituted. Electron microscopy and immunocytochemical analysis of regressing C-26/G-CSF nodules indicates that tumor destruction is due mainly to hypoxia resulting from the functional loss of tumor vasculature and is only marginally due to direct cytolysis. Desegregation of basal lamina, cell swelling, and loss of junctions characterized the vessels within regressing tumors. Tumor cells were necrotic or filled with lipid vacuoles regardless of the distance from nearby vessels. Damage of tumor vasculature was dependent on the infiltrating leukocytes and the cytotoxic cytokines they produced. Locally produced interleukin-1 and tumor necrosis factor-alpha (TNF-alpha) induced vascular cellular adhesion molecule-1 (VCAM-1) and E-selectin on tumor vessels. Treatment with monoclonal antibodies to interferon-gamma (IFN-gamma) or TNF-alpha blocked tumor regression by inhibiting VCAM-1 and E-selectin expression on tumor-associated endothelial cells resulting in a reduced number of infiltrating leukocytes. Thus, C-26/G-CSF tumor regression presents features typical of hemorrhagic necrosis that occurs through the cytokines produced by infiltrating leukocytes in response to G-CSF.