Mechanical and structural comparison between primary tumor and lymph node metastasis cells in colorectal cancer

SW480 and SW620 colon carcinoma cell lines derive from primary tumour and lymph-node metastasis of the same patient, respectively. For this reason, these cells represent an ideal system to analyse phenotypic variations associated with the metastatic process. In this study we analysed SW480 and SW620 cytoskeleton remodelling by measuring the cells' mechanics and morphological properties using different microscopic techniques. We observed that different specialized functions of cells, i.e. the capacity to metastasize of elongated cells inside the primary tumour and the ability to intravasate and resist shear forces of the stream of cells derived from lymph node metastasis, are reflected in their mechanical properties. We demonstrated that, together with stiffness and adhesion between the AFM tip and the cell surface, cell shape, actin organization and surface roughness are strictly related and are finely modulated by colorectal cancer cells to better accomplish their specific tasks in cancer growth and invasion.

Regulation of lamellipodia formation and cell invasion by CLIP-170 in invasive human breast cancer cells

Lamellipodia formation necessary for cell invasion is regulated by Rac1. We report here that lamellipodia formation and three-dimensional invasion were significantly promoted by HGF and serum, respectively, in invasive human breast cancer cells. Rac1 formed a complex with CLIP-170, IQGAP1, and kinesin in serum-starved cells, and stimulation of the cells with HGF and serum caused the partial release of IQGAP1 and kinesin from Rac1-CLIP-170 complex. The HGF-induced release of the proteins and promotion of lamellipodia formation were inhibited by an inhibitor of PI3K. Moreover, downregulation of CLIP-170 by siRNA released IQGAP1 and kinesin from Rac1 and promoted lamellipodia formation and invasion, independent of HGF and serum. The results suggest that promotion of lamellipodia formation and invasion by HGF or serum requires PI3K-dependent release of IQGAP1 and kinesin from Rac1-CLIP-170 complex and that CLIP-170 prevents cells from the extracellular stimulus-independent lamellipodia formation and invasion by tethering IQGAP1 and kinesin to Rac1.

Spindle cell carcinoma of the external auditory meatus with intracranial extension: histological, immunohistochemical and electron microscopic evaluation

We present a case of squamous spindle cell carcinoma of the external auditory meatus in a 38-year-old man. The tumour was extended to the inner ear, the temporal bone, the middle cranial fossa and the meningo-cerebral tissue. The surgical intervention of temporo-occipital craniotomy removed most of the neoplasia. At pathologic examination, the tumour showed an undifferentiated spindle cell pattern. Immunohistochemistry with a large antibody panel found a weak positivity only to EMA. The diagnosis was made when the electron microscopy showed rare junctional structures and tonofilaments.

[Analysis of adrenocortical tumors morphology as regards their structure and potential malignancy]

INTRODUCTION

A consequence of diagnosis of adrenocortical carcinoma (ACC) is introduction of pharmacological therapy, precise monitoring of the patients and in some cases re-operation. The aim of the study is to analyse morphology of adrenocortical tumours as regards their malignancy by use of criteria proposed by Weiss.

MATERIAL AND METHODS

110 adrenocortical tumours in 107 patients were analysed (M 27.1%, F 72.9%; age 32 to 77 years, mean 55.2 +/- 9.7). Conn syndrome was diagnosed in 16 patients (14.9%), Cushing syndrome in 12 (11.2%), and virilisation in 3 (2.8%). In 76 patients (71.0%) biochemical tests did not reveal hormonal hyperactivity of the tumour.

RESULTS

In routine histopatological examination ACC was diagnosed in 6 tumours (5.4%), adrenocortical adenoma (ACA) in 92 (83.6%) and adrenocortical hyperplasia in 12 (10.9%). Nuclear grade III or IV was observed in 8 tumours (7.3%), mitotic rate > 5/50 high power fields in 6 (5.4%), atypical mitoses in 5 (4.5%), clear cells constituting < 25% of the tumour in 10 (9.1%), diffuse architecture in 8 (7.3%), necrosis in 16 (14.5%), veins infiltration in 4 (3.6%), sinusoids infiltration in 7 (6.3%), and tumour capsule infiltration in 5 (4.5%). Among ACC tumours 4-9 features of malignancy were present, among ACA--0-3 features. Statistical analysis revealed correlation between number of criteria proposed by Weiss and maximal tumour size (p < 0.05).

CONCLUSION

The structure and cell arrangement in adrenocortical adenoma are heterogeneous. Application of criteria proposed by Weiss in histopathological examination of adrenocortical tumours can be useful in differentiating adrenocortical adenoma from carcinoma.

Novel use of ultrasound-guided surface marking of head and neck tumors invading facial skin

Malignant tumors of deep head and neck structures can invade skin, but the tumor periphery is difficult to assess clinically. The surgeon's dilemma is achieving tumor clearance with safe margins while at the same time minimizing skin loss on the face. We show, in 2 cases involving the face, that high-resolution diagnostic ultrasound was superior to CT scan in demonstrating the periphery of the tumor. The tumor was distinguished from surrounding edema by its lower echogenicity and homogeneous echotexture. The maximum contour of the tumor was marked on the skin surface with ink under ultrasound guidance. The ink marking aided excision and reconstruction planning. Subsequent histology showed the surgical margins were clear of tumor. The patients remained tumor-free for more than 3 years. Ultrasound imaging therefore shows good potential for planning surgical resection with a safe margin and for aiding decisions on donor site and type of flap for reconstruction.

Novel spatiotemporal patterns of epithelial tumor invasion inDrosophila discs large egg chambers

Loss of Discslarge (Dlg) in early Drosophila egg chambers causes invasion of tumor follicle cells from the anterior epithelium, a pattern that resembles developmental border cell migration during mid-oogenesis. Here, we have analyzed novel spatial and temporal patterns of dlg invasion. Even though Dlg is ubiquitously expressed in all follicle cells, invasions are biased at the anterior and posterior termini. The patterns of invasion correlate with both a higher rate of follicle cell proliferation and with a greater frequency of loss of epithelial polarity at the termini compared with central regions of the egg chamber. Nonetheless, the average number of cells that invade per invasion event from terminal vs. central regions is approximately equal. Of interest, patterns of dlg invasion appear to coincide with boundaries established by proto-oncogene signals responsible for anterior-posterior patterning. The Drosophila egg chamber may thus be a useful model for exploring how epithelial tumor invasion might be a neomorphogenetic process organized by signals essential for developmental pattern formation.

Shedding of membrane vesicles by tumor and endothelial cells

Shedding of membrane vesicles is a vital phenomenon frequently observed in tumor cells and suggested to be involved in several aspects of tumor progression. Our previous studies have shown that human breast tumor cells rapidly shed membrane vesicles containing matrix metalloproteinases (MMPs). In this study we present that human umbilical vein endothelial cells (HUVEC) as well as different tumor cell lines (human ovarian cancer, CABA I and A2780, and hepatocarcinoma cell line, SK-Hep 1) shed vesicles in the extracellular medium. These vesicles carry MMPs and their inhibitors TIMPs. We conclude that tumor and endothelial cells shed MMP-containing vesicles and this may represent a mechanism for regulating focalized proteolytic activity and a way to interact with microenvironment during tumor angiogenesis.

Testing the "Go or Grow" hypothesis in human medulloblastoma cell lines in two and three dimensions

OBJECTIVE

The "Go or Grow" hypothesis proposes that cell division and cell migration are temporally exclusive events and that tumor cells defer cell division to migrate. The purpose of this study was to assess the Go or Grow hypothesis using medulloblastoma cell lines in directional migration and invasion assays in monolayer and three-dimensional cultures.

METHODS

Time-lapse videomicroscopy was used to continually monitor the directional migration, invasion, and mitosis of individual cells. The mitotic activity observed by time-lapse videomicroscopy was compared with staining for the proliferating cell nuclear antigen Ki-67.

RESULTS

A positive correlation exists between the migratory/invasive and mitotic activities of the four medulloblastoma cell lines studied. Within individual cell lines, however, migration and invasion distances are not influenced by the number of cell divisions. Time-lapse videomicroscopy and Ki-67 staining revealed similar trends in mitotic activity between migrating and nonmigrating cells within cell lines. Analysis of cell velocities before, after, and between cell divisions revealed an increase in cell velocity after cell divisions.

CONCLUSION

In the models studied, four medulloblastoma cell lines do not defer cell proliferation for migration across an uncoated surface or invasion of a Type I collagen matrix, contrary to the Go or Grow hypothesis. Migrating and invading cells continue to proliferate and migrate/invade a cell line-dependent distance irrespective of the number of divisions that take place. These findings emphasize the need to evaluate the effect of future therapies on both biological events and, if possible, to identify intracellular signaling proteins that negatively regulate medulloblastoma migration/invasion and proliferation.

Ultrastructurally "invasive" microvilli in an aggressively metastasizing biphasic malignant mesothelioma

The presence of long, slender, often branching microvilli on cell surfaces is a characteristic feature of malignant and benign mesothelial cells. However, these typical microvilli are seen only in better-differentiated lumens within epithelial areas of malignant mesotheliomas. Presented here are the clinical and ultrastructural findings in a biphasic malignant mesothelioma that lacked lumens, but possessed very long microvilli. These invaginated deeply into the cytoplasm of neighboring tumor cells, as well as into the surrounding stromal matrix. The tumor cells had well-formed intercellular desmosomal junctions. The primary tumor was localized to the pleura and invaded the chest wall, but only minimally the lung. Lobectomy demonstrated the presence of metastatic tumor in 2 peribronchial lymph nodes. The disease progressed rapidly and, within 6 months, killed the patient. An autopsy revealed widespread metastases in multiple systemic organs. The authors speculate that the unique ultrastructural features of this case may be a clue to the unusually aggressive course of the neoplasm.

Magnifying endoscopy, stereoscopic microscopy, and the microvascular architecture of superficial esophageal carcinoma

BACKGROUND AND STUDY AIMS

In this study we clarify the microvascular architecture of superficial esophageal carcinoma as observed by ultra-high magnification endoscopy and stereoscopic microscopy with Microfil injection.

PATIENTS AND METHODS

We observed two surgically resected specimens of superficial esophageal cancer under stereoscopic microscopy with Microfil injection. In addition, in the histological investigation, we measured the caliber of the vessels at the surface of the tumor. We carried out ultra-high magnification before treatment in 82 patients with superficial esophageal neoplasms. We classified the depth of tumor penetration of superficial esophageal carcinoma into four categories: m1 to m3 (mucosal cancer) and sm (submucosal cancer).

RESULTS

By observing the normal esophageal mucosa under a stereoscopic microscope and an ultra-high magnification endoscope, we were able to visualize the intrapapillary capillary loops (IPCL). In cancer lesions, we observed characteristic changes in the superficial microvascular architecture according to the depth of tumor invasion. In m1 invasion, there was dilatation of the IPCL; in m2 invasion, there was dilatation and elongation of the IPCL; in m3, there was a mixed appearance of the IPCL and tumor vessels; and in sm invasion, complete replacement by tumor vessels. On the basis of the above criteria, ultra-high magnification endoscopic observation before treatment showed a rate of agreement between histological depth of invasion and magnified appearance of 60/72 cases (83.3 %) for which satisfactory pictures were obtained. The histological investigation showed the caliber of the IPCL of the m1 cancer lesions (12.9 +/- 3.9 microm) to be significantly greater than that of the normal esophageal mucosa (6.9 +/- 1.5 microm) (P < 0.0001).

CONCLUSIONS

Observation of the microvascular architecture of superficial esophageal carcinoma is useful in the diagnosis of the depth of invasion.

The long-term significance of microscopic dural invasion in 354 patients with pituitary adenomas treated with transsphenoidal surgery

OBJECT

Pituitary adenomas are considered benign tumors; however, they may infiltrate surrounding tissues including the dura mater. In this paper the authors analyze the clinical significance of microscopically confirmed dural invasion by comparing a range of variables (age and sex of patients, adenoma type, adenoma size on magnetic resonance [MR] images, remission, residual pituitary disease, recurrence, survival, and disease-free interval after surgery) between patients with noninvasive adenomas and those with invasive ones.

METHODS

Between 1992 and 1997 dural specimens were obtained in 354 patients with pituitary adenomas who underwent transsphenoidal surgery performed by the senior author (E.R.L.). Dural specimens were examined using routine histological methods and assessed for invasion by pituitary adenoma tissue. The dura was invaded by the pituitary adenoma in 161 patients (45.5%), and in 192 patients (54.5%) no evidence of dural invasion was found. Dural invasion was present significantly more frequently in the repeated surgery group (69%, 55 patients) than in the primary transsphenoidal surgery group (41%, 291 patients). The mean age of patients undergoing primary transsphenoidal surgery was significantly older in cases of invasive adenomas (50 years) compared with cases of noninvasive adenomas (43 years), and these age differences also correlated with adenoma size. Women tend to develop clinically evident, smaller adenomas at a younger age than men. Of the patients with pituitary adenomas that were 20 mm or smaller, 117 (76%) of 154 were women, whereas of the patients with adenomas that were larger than 20 mm, 74 (54%) of 137 were men. The frequency of dural invasion increased with increasing size of the pituitary adenoma as measured on MR images. In 291 patients who underwent primary pituitary surgery, the frequency of dural invasion according to adenoma size was 24% (< or = 10 mm), 35% (> 10 to < or = 20 mm), 55% (> 20 to < or = 40 mm), and 70% (> 40 mm). In patients who underwent primary transsphenoidal surgery, dural invasion was present in more than 50% of those with nonfunctioning adenomas and in 30 to 35% of patients with endocrinologically active adenomas. The mean diameter of the gonadotrophic adenomas and null-cell adenomas was significantly larger than that of each of the endocrinologically active adenomas. In 58 (20%) of 291 patients who underwent primary pituitary surgery there was residual pituitary disease postsurgery, and 20% of this subset of patients showed clinical improvement to such an extent that no further management was recommended. After pituitary surgery, residual tumor tissue was demonstrable significantly more frequently in patients with invasive adenomas than in those with noninvasive adenomas. Recurrences after initial remission (cure) of pituitary disease occurred in 18 (8.8%) of 205 patients between 2 and 79 months after primary pituitary surgery (median 25 months). The recurrence rate was not related to dural invasion in a consistent or significant fashion. Seven patients died between 14 and 79 months after pituitary surgery and all had invasive adenomas identified on gross observation at surgery and on microscopy. The survival rate was slightly but significantly decreased for patients with invasive adenomas (91%) compared with patients with noninvasive adenomas (100%) at 6 years postsurgery.

CONCLUSIONS

The principal significance of dural invasion by pituitary adenoma is the persistence of tumor tissue after transsphenoidal surgery (incomplete adenomectomy; 20% in primary pituitary tumor resections). The increase in adenoma size with time and the concurrent development of dural invasion are the major factors that determine an incomplete adenomectomy. When the adenoma remains restricted to the sellar compartment or shows only moderate suprasellar extension, dural invasion may not yet have developed and conditions for complete selective adenomectomy are improved.

Light and electron microscopy of the pagetoid spread of germ cell carcinoma in the rete testis: morphologic evidence suggestive of field effect as a mechanism of tumor spread

The purpose of this study is to investigate the mechanism of tumor spread in the pagetoid spread of germ cell tumors in the rete testis (PSRT). Twenty consecutive cases of germ cell tumor of the testis (9 seminomas, 3 embryonal carcinomas, and 8 teratocarcinomas) were retrieved to identify the cases with PSRT. The areas of pagetoid spread were examined by the serial sectioning of the entire thickness of the tissue block. Available fresh tissue was submitted for electron microscopic study. Ten cases were associated with PSRT and had focal or extensive areas of intratubular germ cell neoplasia (IGCN) in the proximity of the tumor and the rete testis (RT). In the remaining 10 cases, 6 were associated with IGCN distant from the RT and the last 4 were not associated with IGCN. Seminiferous tubules with IGCN were seen connecting with the RT with pagetoid spread. Isolated single intraepithelial tumor cells also were identified at the periphery of the areas with PSRT. Electron microscopic study of the RT of 4 cases with PSRT (2 seminomas, 1 embryonal carcinoma, and 1 teratocarcinoma) revealed desmosome-type junctions between tumor cells with RT epithelial cells. Direct tumor expansion and cell motility as mechanisms of tumor spread in PSRT does not explain the presence of isolated cells and desmosome-type junctions of the tumor cells as demonstrated in this study. The authors believe that the field effect plays an important part in the pathogenesis of this pagetoid spread in the RT. It is likely that this field effect is induced by the germ cell tumor and is operated through the immature germ cells or undifferentiated epithelial cells in the RT adjacent to the tumor cells.

Critical steps in hematogenous metastasis: an overview

Metastasis is responsible for most cancer deaths. A better understanding of the process provides opportunities to develop new treatments to prevent metastasis. This article summarizes findings from experimental in vivo videomicroscopy and quantitative studies on metastatic inefficiency, which indicate that early steps in hematogenous metastasis may be quite efficient, but that regulation of cancer cell growth in secondary sites determines metastatic outcome. The authors have identified three key stages of this growth regulation: survival of a subset of single cells, proliferation of a subset of these cells to form preangiogenic micrometastases, and persistence of growth of a subset of these to form vascularized metastases. Formation of clinically relevant metastases is determined by the proportion of cells that proceeds successfully through each stage, and surviving single cells and preangiogenic micrometastases both represent possible sources of tumor dormancy.

Vascular channel formation by human melanoma cells in vivo and in vitro: vasculogenic mimicry

Tissue sections from aggressive human intraocular (uveal) and metastatic cutaneous melanomas generally lack evidence of significant necrosis and contain patterned networks of interconnected loops of extracellular matrix. The matrix that forms these loops or networks may be solid or hollow. Red blood cells have been detected within the hollow channel components of this patterned matrix histologically, and these vascular channel networks have been detected in human tumors angiographically. Endothelial cells were not identified within these matrix-embedded channels by light microscopy, by transmission electron microscopy, or by using an immunohistochemical panel of endothelial cell markers (Factor VIII-related antigen, Ulex, CD31, CD34, and KDR[Flk-1]). Highly invasive primary and metastatic human melanoma cells formed patterned solid and hollow matrix channels (seen in tissue sections of aggressive primary and metastatic human melanomas) in three-dimensional cultures containing Matrigel or dilute Type I collagen, without endothelial cells or fibroblasts. These tumor cell-generated patterned channels conducted dye, highlighting looping patterns visualized angiographically in human tumors. Neither normal melanocytes nor poorly invasive melanoma cells generated these patterned channels in vitro under identical culture conditions, even after the addition of conditioned medium from metastatic pattern-forming melanoma cells, soluble growth factors, or regimes of hypoxia. Highly invasive and metastatic human melanoma cells, but not poorly invasive melanoma cells, contracted and remodeled floating hydrated gels, providing a biomechanical explanation for the generation of microvessels in vitro. cDNA microarray analysis of highly invasive versus poorly invasive melanoma tumor cells confirmed a genetic reversion to a pluripotent embryonic-like genotype in the highly aggressive melanoma cells. These observations strongly suggest that aggressive melanoma cells may generate vascular channels that facilitate tumor perfusion independent of tumor angiogenesis.

Specialized surface protrusions of invasive cells, invadopodia and lamellipodia, have differential MT1-MMP, MMP-2, and TIMP-2 localization

Surface protrusions, invadopodia, and analogous lamellipodia at the leading edge of an invasive cell, which make contact with the underlying extracellular matrix (ECM), are the main motor for cellular locomotion and invasion. Previous studies have demonstrated that invadopodia, but not lamellipodia, are sites of ECM degradation on the cell surface. Such degradative activity is in part due to the localization of latent matrix metalloproteinase-2 (MMP-2) and membrane type-1 MMP (MT1-MMP) to invadopodia, where MMP activation occurs. Although lamellipodia exhibit similar structure and mobility to invadopodia, lamellipodia, by virtue of their location at the cellular periphery, are readily accessible to the soluble tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) and blood-borne inhibitors. We show here that TIMP-2 co-localizes with MT1-MMP and MMP-2 at lamellipodia but not with that of invadopodia. Thus, the MMP-TIMP localization at lamellipodia may be a key mechanism for the regulation of MMP activation on the cell surface, which in turn governs expression of the cell-invasive phenotype.

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.

Vascular invasion of O-1N, hamster squamous cell carcinoma with high potential of lymph node metastasis: ultrastructural comparison between lymphatics and blood vessels

The ultrastructural modes of lymphatic and blood vessel invasions were studied comparatively in hamsters with squamous cell carcinoma (O-1N) that had a high potential for lymph node metastasis. The endothelial injury, which was caused by mechanical stretching with the growth of O-1N, was the initial and characteristic feature common to both vascular invasions. Tumor cell nests penetrating the lymphatic lumen through disrupted endothelial cells still maintained their volume and continuity to the underlying tumor cell nests. In contrast, pronounced microthrombotic and neutrophilic reactions occurred at the site of blood vessel penetration. Within the lymphatic lumen, large clusters of O-1N cells were kept longer in spite of lymphocytic and macrophagic reactions. In blood vessels, clusters of tumor cells that had passed through dense fibrin layers were reduced in size and further disintegrated into smaller pieces by neutrophils. In conclusion, lymphatic invasion is a mechanical process, and smooth and direct invasion of large tumor cell nests into lymphatic vessels is responsible for causing more prompt and frequent lymph node metastasis in O-1N than a hematogenous type.

Morphological changes in the basement membrane during progression from non-invasive to invasive rat bladder cancer induced by N-butyl-N-(4-hydoxybutyl) nitrosamine

OBJECTIVE

To investigate the ultrastructural changes in the basement membrane (BM) in the rat model of bladder cancer when progressing from non-invasive to invasive disease.

MATERIALS AND METHODS

N-butyl-N-(4-hydoxybutyl) nitrosamine (BBN) was administered to 50 rats (7 weeks old) in their drinking water (0.05% BBN) for 28 weeks. At between 20 and 28 weeks, 10 rats were killed every 2 weeks and morphological changes of the BM were investigated by transmission electron microscopy and histological changes by light microscopy.

RESULTS

At between 20 and 28 weeks, the transitional cell carcinoma (TCC) of the rat bladder induced by BBN progressed from non-invasive (stage Ta) to invasive (stage T1-2) disease. Focal thinning and discontinuity of the BM occurred in five of 26 rats with non-invasive TCC and in all 24 rats with invasive TCC.

CONCLUSIONS

Stage Ta bladder cancer in the rat model may be associated with degradative changes in the BM and can be divided into two types, Ta1 where there is no degradation of the BM and Ta2, where the BM is degraded.

Inactivation of retinoblastoma family proteins by SV40 T antigen results in creation of a hepatocyte growth factor/scatter factor autocrine loop associated with an epithelial-fibroblastoid conversion and invasiveness

SV40 T antigen (LT) is an oncoprotein that inactivates nuclear regulators such as retinoblastoma (RB) family proteins and p53. We recently reported that in Madin-Darby canine kidney (MDCK) epithelial cells the binding of LT to RB family proteins results in a massive apoptosis and a concomitant down-regulation of c-myc. Here, we show that LT causes loss of epithelial differentiation and induces invasiveness. MDCK cells expressing wild-type LT, but not mutants unable to bind RB, exhibit a fibroblast-like morphology, show a strong down-regulation of the vHNF1 transcription factor and acquire invasive properties. The stable retransformation of MDCK(LT) with a RB and/or c-myc-expressing vector restores the expression of epithelial characteristics. Our data therefore suggest an important role for RB and c-myc in modulating the epithelial phenotype both during normal tissue development and in invasive processes. In addition, when grown in collagen gels, the MDCK(LT) cells form branching tubules, and their conditioned media produce the scattering of monolayer cultured MDCK cells. These last properties are reminiscent of those induced by hepatocyte growth factor/scatter factor (HGF/SF). Moreover, the HGF/SF protein was detected by Western blotting in the MDCK(LT)-conditioned medium. The production of HGF/SF is specifically induced by LT-RB inactivation, because Ras transformation of MDCK cells fails to induce the production of this factor. These results demonstrate that inactivation of RB family proteins in these cells is at the origin of a HGF/SF autocrine loop.

Structure of the initial lymphatics of the human urinary bladder with invasive urothelial tumors

The ability of urothelial tumors of the urinary bladder to metastasize via the lymphatic circulation and the extent of metastatic involvement of regional lymph nodes is an important parameter in the staging and prognosis of these neoplasms. Accordingly, we examined the site and morphology of initial lymphatic vessels in the mucosa of the human urinary bladder in patients with invasive transitional cell carcinoma. Lymphatics in the papillary tumoral mass was also examined. Endoscopic transurethral biopsies from the urinary bladder of 120 patients with invasive transitional cell papillary carcinoma were utilized for this study. Biopsy from the uninvolved lateral wall of the same patient was utilized as a control. On histopathology of biopsies of neoplastic tissues, initial lymph vessels were seen in the deeper region of the mucosa but not in the subepithelial layer nor in the stroma of the tumoral papillae. The latter were often associated with arteriolar and venular vessels. When edema and inflammation occurred in peritumoral regions, lymphatics showed a dilated lumen, non-indented wall with dissociated perivascular collagen and elastic fibers. Tumoral permeation or embolization of lymphatics was seen in 12% of patients with invasive tumors, and these lymphatic vessels did not display significant morphologic changes. The absence of initial lymphatics in the stroma of tumoral papillae and in infiltrated subepithelial regions of the urinary bladder may explain the absence of lymph node metastasis in early-stage invasive urothelial tumors.

Ultrastructural analysis of the adjacent epithelium of oral squamous cell carcinoma

Fifteen biopsies of the immediate adjacent epithelium of oral squamous cell carcinoma were examined under light and electron microscopy. Light microscopic examination of one micron thick sections revealed that the majority of lesions (67%) had hyperplastic or mildly dysplastic epithelium while the remaining (33%) had moderate to severe dysplasia. Ultrastructural observations showed that all these lesions had subcellular alterations similar to those seen in frank malignant oral tissue, particularly in the lower half of the epithelium. Important ultrastructural changes observed included bizarre nuclei of basal and lower spinal cells, enlarged and multiple nucleoli, presence of interchromatin and perichromatin granules, loss of desmosomes and marked spongiosis as well as disturbed cellular maturation sequences in the keratinocytes evidenced by abnormal and irregular distribution of maturation markers such as keratohyalin granules and tonofilaments. The present study thus shows the value of electron microscopy in the detection of malignant changes in the adjacent epithelium of oral squamous cell carcinoma.

The role of basement membrane in colorectal cancer invasion and liver metastasis

BACKGROUND

Basement membrane (BM) is a specialized extracellular matrix component that plays a key role in tumor invasion and metastasis.

METHODS

Immunohistochemical staining for two major components of BM, type IV collagen (C IV), and laminin (LN), utilizing avidin-biotin-peroxidase complex detection to examine 182 primary colorectal cancers (pT2 or greater) and 20 liver metastases.

RESULTS

The distribution of C IV was the same as of LN in colorectal cancer tissue, and in normal tissue. Both C IV and LN staining were more frequently positive in the superficial zone but infrequently in the deep zone of the primary tumor. BM preservation, C IV and LN staining in both the superficial and deep zones, was seen in 18.7% of the subjects. The rate of BM preservation significantly decreased with increasing histologic grade (P < 0.01). No correlation was observed between pT number and BM preservation. The rate of BM preservation in cases of liver metastasis was 84.4%, significantly higher than the rate in cases without liver metastasis (P < 0.001). BM was observed even at the advancing front of tumor invasion and was preserved in 95.0% of the liver metastases.

CONCLUSIONS

BM is a functional substance that appears to accompany cancer rather than function as a structural barrier against cancer invasion and liver metastasis.

Can chromatin texture predict structural karyotypic changes in diploid cells from thyroid cold nodules?

To assess the effect of a single chromosomal translocation on the nuclear phenotype of human cells, seven diploid adenomas and five diploid carcinomas of the thyroid gland were studied using quantitative nuclear morphometry. Four adenomas and three carcinomas were cytogenetically normal, whereas three adenomas and two carcinomas had a unique chromosomal translocation. A densitometric parameter discriminated adenomas from carcinomas (skewness of the optical density histogram, SODH), and tumours with and without chromosomal translocation (standard deviation of the optical density, SDODH). These results demonstrate that single chromosomal structural rearrangements produce quantifiable alterations of nuclear organisation, but that other nuclear features which do not express an aneuploid DNA content or an abnormal karyotype differentially characterise benign and malignant conditions.

Glycocalyceal bodies in a human rectal carcinoma cell line and their interstitial collagenolytic activities

In co-cultivation on a membrane of connective tissue matrix (CTM) obtained from human dura mater, human adenocarcinoma cells (RCM-1) degraded CTM. Morphologically, the destruction of CTM was associated with the shedding of membrane vesicles from the cells. Transmission electron microscopy, using ruthenium red (RR), showed that the shed vesicles were composed of various-sized membrane bound vesicles (MV). A large majority were small glycocalyceal bodies (G-bodies) measuring 20-120 nm in diameter, composed of an amorphous matrix of moderate electron-density surrounded by an RR-positive, trilaminar membrane. G-bodies were separated from medium-sized and large MVs by ultracentrifugation. Ultrastructural observation of the isolated collagen fibrils from CTM co-cultured with RCM-1 cells, showed G-bodies attached to degraded collagen fibrils with characteristic transverse notches along their axes. The lesions occurred as microerosions in the apolar region between the e and d bands of collagen fibrils. Collagenolytic activity in serum-free RCM-1 conditioned medium was localized in the G-body and MV fractions (80% and 20% of the total activity, respectively, when tested against 3H-labeled type I collagen). No activity was detected in the supernatant. The activity in G-bodies was also confirmed by ultrastructural analysis using reconstituted native type I collagen fibrils. The results suggest that RCM-1 cells release interstitial collagenase as a component of G-bodies which facilitates local breakdown of connective tissue during the process of invasion.

Assessment of invasion in breast lesions using antibodies to basement membrane components and myoepithelial cells

This paper describes immunostaining of consecutive sections from 15 cases of fibrocystic change of the breast (including 2 examples of intraductal papilloma), 4 ductal carcinomas-in-situ and 17 invasive carcinomas (4 tubular, 1 papillary, 2 lobular and 10 infiltrating ductal, NOS) with antisera to components of the basement membrane (BM), type IV collagen and laminin, and with the muscle antibodies actin and muscle-specific actin. A simple digestion technique was developed to improve the clarity of BM staining with these antibodies. The BM stains facilitated identification of small invasive foci through breaks in the BM in 2 of the cases which had been reported as pure intraductal carcinoma. Tubular carcinomas were surrounded by abnormal, fragmented, and focally discontinuous BM, a feature which could be used to distinguish this well-differentiated breast carcinoma sub-type from sclerosing adenosis, in which individual acini were invariably surrounded by a continuous BM. BM staining emphasized the fibrovascular core of intraductal papillomas, whereas the BM layer was absent in intraductal, cytologically malignant, papillary projections. Similarly, myoepithelial cells, stained with antisera to muscle actins, were identified in a continuous layer surrounding benign epithelial proliferations. These immunohistochemical staining techniques may thus assist the diagnostic histopathologist in differentiating between benign epithelial proliferations of the breast and well-differentiated invasive breast carcinoma, and in identifying foci of microinvasive carcinoma.

Organelle rearrangement and cell volume changes during squeezing invasion of peritoneal elastic lamina by targeted murine breast carcinoma cells

Murine breast cancer cell lines were developed to selectively invade the peritoneum while they proliferated in ascites form in the abdominal cavity. In a dominant form of invasion, tumor cells showed special affinity for elastin fibers and squeezed through narrow gaps in the elastic fiber meshwork of the stroma. Even in fixed tissue, such cells could be recognized as being in the process of invasive migration because of their dumbbell shape. This appearance was similar to that of diapedetic blood cells traversing bone marrow sinus endothelium. Three-dimensional STERECON graphics reconstruction from serial thick sections of 44 such cells was carried out. The reconstructions showed that, in mid-penetration, the cells spread extensively over the exterior surface of the elastic fiber meshwork. The cell surface contact of these forward projections was mainly with the elastic fiber outer coat of microfibrils, but small areas of the cell surface also fused directly to inner-core elastin. The morphological rearrangement of the cytoskeleton was minimal in both types of attachment areas. The location of these forward facing attachments is consistent with mechanisms for pulling the invasive cell through the gap. Lamellopodia formation and clustering of cytoplasmic organelles occurred more commonly at the forward-facing part of the cell. Morphometry of the reconstructions showed that a contraction of the whole cell occurred during the squeezing/migration process suggestive of an additional pushing process. However, our invasive cell lines showed marked differences in the degree of cell shrinkage. The process of adhesion and squeezing of tumor cells through elastin meshworks in vivo is clearly a complex phenomenon. Changes in cell surface activity appear to play a significant role in establishing the necessary 'foothold' component of invasion and, possibly, in the generation of tractive force as well.

Karyometric marker features in fine needle aspirates of follicular adenoma of the thyroid

Karyometric measurements were performed on fine needle aspirates of clearly identifiable adenomatous areas and adjacent normal-appearing areas in the surgical specimens from ten patients with follicular adenomas of the thyroid. Similar measurements were made on aspirates from nine patients free of thyroid disease. A total of 95 karyometric features were evaluated for each nucleus. Analysis of variance of optical density values did not show a significant difference between the three types of nuclei. Discriminant analysis selected seven karyometric features that produced a statistically highly significant separation of adenoma nuclei from control nuclei. A similar analysis selected six features that produced a statistically highly significant discrimination of normal-appearing nuclei from control nuclei. The validity of these markers for distinguishing control nuclei from adenoma nuclei and normal-appearing nuclei adjacent to adenomas was demonstrated by analysis in further training and test sets. These findings parallel those previously demonstrated for invasive and microinvasive follicular carcinomas of the thyroid.

Expression of anionic sites on tumour cells at different stages of tissue invasion in vivo: a comparative study by X-ray microanalysis

Quantification of colloidal iron hydroxide (CIH) labelling by X-ray microanalysis was used to investigate anionic sites at the surface of Ehrlich carcinoma cells from different locations in the mouse host. Individual tumour cells from peritoneal ascites suspensions (pre-invasion stage) varied up to threefold in their ability to bind CIH and a similar degree of intra-tumour heterogeneity was observed in different experimental animals. Pretreatment of the cells with neuraminidase confirmed that binding was at least partly due to surface sialic acid. Invasive cells isolated from mesenteric tumour nodules were also heterogeneous with regard to the availability of surface anionic sites, as were tumour cells adhering to the surface of the mesentery; however, in both these populations CIH binding was significantly greater on average than for free ascites tumour cells. The results suggest that surface anionic sites are determinants of the invasiveness of malignant cells in vivo, and that both the number and topography of these sites may be important in modulating tumour cell behaviour.

Mouse L cells expressing human prourokinase-type plasminogen activator: effects on extracellular matrix degradation and invasion

A cosmid (cos pUK0322) harboring the complete human urokinase-type plasminogen activator (u-PA) gene and Geneticin resistance as a selectable marker was isolated from a human genomic library and characterized. After transfection of cos pUK0322 into mouse L cells and selection, several plasminogen activator (PA)-expressing clones were obtained and one (LuPA) was chosen for additional study. The PA expressed was identical to human pro-u-PA in enzymatic, electrophoretic, and antigenic properties. The expression of PA was stable over 50 population doublings. The regulation of the transfected gene was studied by treatment of the cells with various hormones and other effectors. Expression of PA activity was inhibited fivefold by dexamethasone and stimulated two- to threefold by agonists of the adenylate cyclase dependent pathway of signal transduction, such as dibutyryl cyclic AMP and cholera and pertussis toxins. The modulation of PA activity was associated with corresponding changes in mRNA steady-state levels. The phenotypic changes associated with pro-u-PA expression were analyzed in vitro by degradation of 3H-labeled extracellular matrix (ECM), invasion of a matrigel basement membrane analogue, and by light and electron microscopy. LuPA cells and reference HT-1080 fibrosarcoma cells, in contrast to control Lneo cells transfected with the neomycin resistance gene, degraded the ECM and invaded the matrigel basement membrane. Matrix degradation correlated with the modulation of pro-u-PA gene expression as it was inhibited by dexamethasone and promoted by dibutyryl cyclic AMP. Inhibition of PA or plasmin using anti-u-PA IgG or aprotinin prevented ECM degradation and invasion. These results demonstrate that u-PA expression alone is sufficient to confer to a cell an experimental invasive phenotype.

The flavonoid tangeretin inhibits invasion of MO4 mouse cells into embryonic chick heart in vitro

Tangeretin, a flavonoid from citrus plants, was found to inhibit the invasion of MO4 cells (Kirsten murine sarcoma virus transformed fetal mouse cells) into embryonic chick heart fragments in vitro. The flavonoid appeared to be chemically stable in tissue culture medium, and the anti-invasive effect was reversible on omission of the molecule from the medium. Unlike (+)-catechin, another anti-invasive flavonoid, tangeretin bound poorly to extracellular matrix. It did not alter fucosylated surface glycopeptides of MO4 cells. Tangeretin seemed not to act as a microtubule inhibitor, as immunocytochemistry revealed no disturbance of the cytoplasmic microtubule complex. However, at anti-invasive concentrations of tangeretin, cell proliferation and thymidine incorporation appeared to be inhibited. When cultured on an artificial substrate, treated MO4 cells were less elongated, covered a larger surface area and exhibited a slower directional migration than untreated cells. From the decrease in ATP content in MO4 cells after tangeretin treatment, we deduce that this flavonoid inhibits a number of intracellular processes, which leads to an inhibition of cell motility and hence of invasion.

Ultrastructural study on the invasion of the basal lamina of retinal inner limiting membrane by esophageal carcinoma cells

Esophageal carcinoma cells EC/CUHK1 were allowed to interact with the basal lamina of the inner limiting membrane of the retina in vitro. Both scanning and transmission electron microscopy revealed that tumour cells first attached to the basal lamina with filopodia and subsequently invaded into the ganglion cell layer of the retina. In addition, transmission electron microscopic studies demonstrated that tumour cells induced mechanical distortion as well as dissolution of the basal lamina.

Scanning electron microscopic study of invasiveness between normal and neoplastic cells and fibroblasts in monolayer culture

Normal cells are non-invasive except for a few cell types such as leukocytes and macrophages, while neoplastic cells are active in both migration and invasion. In the present investigation, the confrontations of normal rat hepatocytes, lung macrophages and B16 melanoma cells with monolayers of fibroblasts grown on collagen gel have been studied. When monolayers of fibroblasts were confronted with melanoma cells, there was obvious retraction of the fibroblasts. When hepatocytes or macrophages were seeded onto monolayers of fibroblasts, infiltration always occurred at intercellular contacts and no retraction of fibroblasts was seen. Therefore it would appear that normal and neoplastic cells penetrate into monolayers of fibroblasts by different mechanisms.

Invasiveness in primary intracranial tumors: Part 2. Studies with scanning electron microscopy of cell surface alterations associated with invasiveness

We previously described an experimental model for the production of invasive and noninvasive astrocytic series tumors and a semiquantitative assessment of their invasiveness. The tumors are produced by intracerebral inoculation of simian virus 40-transformed cells from four different brain regions. Cells of cerebral cortex and brain stem derivation produced invasive tumors; tumors of cerebral cortex derivation were more invasive and became increasingly invasive with alternate in vivo and in vitro passage. Cells of cerebellar hemisphere and vermis derivation produced primarily noninvasive tumors. This report describes the surface configuration of these tumor cells in culture at or near confluence as visualized with scanning electron microscopy. Normal cells form a multilayered base of flat, overlapping cells with few excrescences and indistinct borders and have only rare dividing or giant cells attached. Invasive tumor cells from a monolayer base of extremely flat and spread out cells almost devoid of excrescences, with few dividing or giant cells attached. Cells of cerebral cortex derivation additionally have numerous microvilli and ruffles at points of intercellular contact and become covered with microvilli after passage. These features were retained after cloning by dilution plating, but not after cloning by growth in soft agar. Our primarily noninvasive cells form a multilayered base of rounded cells covered with various excrescences and numerous attached dividing and giant cells. These surface features seem to be related to intercellular and cell-substrate adherence. The configuration of the invasive cells is consistent with increased cell-substrate adherence, substrate-dependent inhibition of locomotion, and decreased intercellular adherence among the more invasive cells. The configuration of our primarily noninvasive cells is consistent with decreased cell-substrate adherence and unrestricted multilayered growth. Thus, it seems that invasiveness is expressed at the cell surface and is related to disturbances in adherence balance rather than in cell proliferation.

The invasive edge: invasion in colorectal cancer

Primary human colorectal carcinomas which had already metastasized to the draining lymph nodes have been studied by transmission electron microscopy and tissue culture. The invasive edges were identified by examining mirror-image blocks for light and electron microscopy. In the invasive edge there are single cells and small clusters of cells which have ultrastructural features suggestive of active cell movement; clusters of cells are found in the lymphatic trunks and in the subcapsular sinus of draining lymph nodes. Small clusters of cells survive in short-term culture; some of these cells are actively motile. These findings support the view that there is a sub-population of motile and invasive cells at the edge of human colorectal cancers.

Invasion of reconstituted basement membrane matrix by metastatic human tumor cells

A gel-like reconstituted basement membrane matrix containing type IV collagen, laminin, entactin, nidogen, and heparan sulfate proteoglycan was used to examine the invasive properties of human HT1080 fibrosarcoma cells. Within several hours after seeding, the tumor cells initiated a random migration, leaving behind channels etched in the surface of the matrix. Eventually the channels became interconnected into a complex network. As the tumor cells proliferated, the channels became filled until the surrounding matrix was gradually dissolved. Cells then migrated outward, forming the typical disorganized cell monolayer normally observed when fibrosarcoma cells are cultured on plastic surfaces. In contrast to the fibrosarcoma cells, normal skin fibroblasts, while able to attach to the matrix, exhibited minimal migration, tracking, and invasion during the same time period. When tumor cells were seeded onto thick layers of matrix, the cells ultimately invaded downward into the matrix, leaving behind open tunnels. At the front of the invading cells, long irregular pseudopodia projected in the direction of movement. Electron microscopy demonstrated these filopodial and lamellopodial projections to directly extend into the surrounding matrix, with focal clearing of the matrix in the immediate vicinity of these invading pseudopodia. Thus, tumor cell invasion of extracellular matrices, including basal lamina, may proceed by the formation of specialized pseudopodia that not only form adhesion contacts with the matrix but also provide an efficient mechanism for the focal hydrolysis of the matrix at the site of directed cell movement.

Mechanisms of tumor invasion: evidence from in vivo observations

The major mechanisms of tumor invasion in vivo are discussed in the present review. A special emphasis is placed on tumor dedifferentiation which has proved to be of paramount importance for the invasion process. Based on in vivo observations obtained from various human and animal tumors a concept for the mechanism of tumor invasion is proposed which mainly comprises the following basic events: the first and essential step in tumor invasion is the tumor dedifferentiation and dissociation at the invasion front. This apparently temporary and reversible process mobilizes the tumor cells out of the main tumor bulk and enables them to invade the host tissue by active locomotion. This mechanism is essentially supported by an interstitial edema in the host tissue adjacent to the tumor periphery, which causes an 'opening and widening' of the host intercellular spaces. Enzymatic changes in the micromilieu of the extracellular matrix may contribute to this process. The tumor cell proliferation completes the invasion process in so far, as the invading tumor cells are still able to proliferate, leading this way to expanding tumor cell nests in the host tissue which have the potency to redifferentiate. The expansive growth of these tumor cell nests results in a progressive atrophy of the host tissue, mainly caused by an increasing compression and a competitive withdrawal of oxygen and other nutrients by the tumor cells. The overall picture of tumor invasion can therefore be considered as a repetitive cycle of active tumor cell locomotion followed by focal tumor cell proliferation in the host tissue.

Invasive activities of metastasizing and nonmetastasizing tumor cell variants in vitro

Pieces of the endothelium of the aorta of BDX rats were confronted with two syngeneic-tumor-cell variants. While the AS variant is non-metastasizing, the ASML cells metastasize spontaneously via the lymphatic vessels. By means of scanning-electron microscopy the adhesion phenomena and the various stages of invasive activity of the non-metastasizing variant (AS) as well as the retraction of the endothelial cells depending on the time of confrontation were studied. Though the metastasizing variant (ASML) adhered firmly to the endothelium, we found neither signs of invasive activity of these tumor cells nor retraction phenomena of the endothelial cells. Aggregates of AS- and clusters of ASML-cells, respectively, behaved in exactly the same way as single cells: while the ASML-clusters remained inactive, the AS-aggregates exhibited invasive activities. Those cells which were in intimate contact with the endothelium started to leave the aggregate, thereby forming a foot-like layer beneath the rest of the aggregate; these cells began to invade.

Invasion in vitro. Methods of analysis

To understand the mechanisms of tumour invasion a number of in vitro assays have been developed, in which test cells (invasive or non-invasive) have been confronted with normal cells or tissues (the host) and cultured in various ways. We will discuss here the methods by which invasion can be judged in such assays. Histology is the method that is used successfully by pathologists for the evaluation of tumour invasiveness in vivo. The major difficulty is that the relationship between the non-invasive counterpart and the host tissue is not known in vitro or in vivo. Some authors have attempted to quantify invasion on histologic sections, but a generally accepted method is not yet available. The potential contribution of time lapse cinematography to the study of the kinetic aspects of invasion is obvious. Optical systems which overcome the relative lack of transparency of three-dimensional tissues, however, do not exist. Electron microscopy has contributed by providing details about the interactions between invasive cells on the one hand and normal cells as well as intercellular matrices on the other hand. Subpopulations of highly invasive and metastatic cells were collected after repeated migration through normal tissues in two-compartment assays. Attempts to evaluate the cytotoxic effect of invasive cells confronting radiolabelled cells or tissues have produced equivocal results. In contrast, measurements of radioactivity in the medium of labelled substrata have demonstrated the lytic effect of invasive cells on the extracellular matrix. It is concluded that further search for better methods to analyze and quantitate invasion is needed. So far, corroborative analysis by various methods seems to be the best policy.

Vinblastine, Vincristine and Vindesine: anti-invasive effect on MO4 mouse fibrosarcoma cells in vitro

Inhibition of the invasiveness of MO4 mouse fibrosarcoma cells by the vinca alkaloid, vinblastine (VLB), vincristine (VCR) and vindesine (VDS), has been examined in vitro. At doses between 0.006 microgram/ml (minimal effect) and 0.1 microgram/ml (complete inhibition) these drugs interfered with the invasion of MO4 cells from an aggregate confronting a fragment of embryonic chick heart in three-dimensional culture. We have also examined the effect of these drugs on the following activities of MO4 cells: growth, directional migration and assembly of the cytoplasmic microtubule complex. Growth and directional migration were affected by the same doses of vinca alkaloids as invasion. In contrast with the vinca alkaloids, 5-fluorouracil at 1 microgram/ml inhibited growth but allowed directional migration and invasion. At a dose of 0.3 microgram/ml VLB, VCR and VDS interfered with the assembly of cytoplasmic microtubules, as visible after immunocytochemical staining with tubulin antiserum. Ultrastructural analysis demonstrated that inhibition of invasion in three-dimensional culture corresponds with abolishment of the cytoplasmic microtubule complex. Anti-invasive concentrations of VLB, VCR and VDS represent clinically achievable plasma concentrations. We concluded that the anti-invasive effect of the vinca alkaloids may contribute to their antitumor activity.

Melanoma. An ultrastructural study of the host inflammatory and vascular responses

Electron microscopic studies of 4 surgically excised human primary superficial spreading melanomas of the skin were done with special emphasis on the host inflammatory and vascular responses to tumor. Host cells participating in the inflammatory response included numerous small lymphocytes, activated macrophages, and mast cells. Some mast cells had lost local portions of granule content, but complete degranulation of mast cells was not seen. Activated macrophages had avidly ingested melanin granules and cellular debris and often were close to dying tumor cells. Lymphocytes, many displaying motile forms, were actively invading the epidermis; formed perivascular cuffs around damaged vessels; and were in intimate contact with living, damaged, and dead melanoma cells. Basophils, eosinophils, and neutrophils were absent from inflammatory infiltrates. Changes of the microvasculature included focal endothelial necrosis and hypertrophy as well as basal lamina changes indicative of repeated episodes of endothelial injury, necrosis and regeneration. These findings are discussed in relationship to a number of recent studies of the immunologically-mediated inflammatory responses to contact allergy, graft rejection, and syngeneic tumor rejection, in man and animals.

Mammary-carcinoma cells in mouse liver: infiltration of liver tissue and interaction with Kupffer cells

Interactions between TA3 mammary-carcinoma cells and liver cells were studied with the electron microscope in mouse livers that had been perfused with a defined medium containing the tumour cells. Infiltration of liver tissue by the TA3 cells proceeded in the following steps. First, numerous small protrusions were extended through endothelial cells and into hepatocytes. Next, some cells had larger processes deeply indenting hepatocytes. Finally a few tumour cells became located outside the blood vessels. Two variant cell lines, TA3/Ha and TA3/St, differing in cell coat and surface charge, did not differ in the extent of infiltration. TA3/Ha cells were often encircled by thin processes of liver macrophages (Kupffer cells). Encircled cells were initially intact, but later some of them degenerated. These observations suggest that TA3/Ha cells were phagocytized by the Kupffer cells. Encirclement appeared to be inhibited after only 30 min, when many cells were still partly surrounded. Encirclement of TA3/St was much less frequent. After injection of tumour cells intra-portally in vivo, similar results were obtained, which demonstrated the validity of the perfused liver model. TA3/Ha cells formed much fewer tumour nodules in the liver than TA3/St cells.

Ultrastructural study of liver sinusoids of mice during invasion by leukemic myelocytes

Results of an ultrastructural study of liver of RF mice during invasion by leukemic myelocytes were reported. In early stages of infiltration, leukemia cells adhered to the endothelial cells of the sinusoidal wall; gaps 1-4 mu in diameter then developed in the endothelium, and leukemia cells passed through the gaps to enter the extravascular space. Other sinusoids became occluded by leukemic myelocytes, the endotheilium disintegrated, and the occluding cells thus became extravascular. In late stages of infiltration, when leukemia cells migrated back into the sinusoids, the endothelium was continuous and leukemia cells passed through temporary pores located within endothelial cells.