Microvasculature of human colorectal epithelial tumors. An electron microscopic study

High-fat diet causes an imbalance in the colonic serotonergic system promoting adipose tissue enlargement and dysplasia in rats

A high-fat (HF) diet, the serotonergic system and stromal elements have all been implicated in colon carcinogenesis. We investigated whether the colonic serotonergic system could play a main role in the development of colonic dysplasia and stromal reactivity in carcinogen-treated rats under HF diet. For this, dimethylhydrazine-treated rats were fed with standard diet and a HF diet. Fat distribution was quantified by computerized tomography exam, serotonergic activity was analyzed by high-performance liquid chromatography, gene expression, and immunohistochemistry, which along with histopathological technique enabled us to enumerate dysplasia, microvessels density, cell proliferation and COX-2 expression. We found that the HF diet induced an increase in the amount of visceral adipose tissue, even without expressive changes in the average body weight. This was correlated with a loss of serotonergic balance in colon tissue. Moreover, the HF diet promoted dysplasia and microvessel density in association with increased proliferation and COX-2 expression within pericryptal colonic stroma. Our current findings suggest that a HF diet promotes the enlargement of adipose tissue via loss of control in colon serotonergic activity, which enhances colonic dysplasia by supporting microvessel development.

Blood flow resistance in lesion vessels and normal host vessels evaluated by pulsed Doppler ultrasound

Blood flow rate in the microcirculation is proportional to the arteriole-venule pressure difference and inversely proportional to the blood flow resistance (BFR). Generally, the BFR studies to date have focused on using invasive methods and were carried out in non-physiological conditions. Moreover, few studies have been concerned with the relationships of BFR between the tumor vessels and the normal host vessels. The present study investigated the BFR in malignant lesion vessels, benign lesion vessels and normal host vessels in physiological conditions using pulsed Doppler ultrasound as a tool and the thyroid as a model, A total of 133 patients with thyroid nodules were included in the study. The results revealed that most of the BFR parameters were higher in malignant lesion vessels than in benign lesion vessels (P=0.001-0.029), as well as lower in normal host vessels than in malignant or benign lesion vessels (P=0.000-0.017); Low to moderate significant positive correlations of BFR between benign lesion vessels and normal host vessels were also found (r=0.358-0.480, P=0.000 for all). Finally and interestingly, low negative correlations between the malignant nodule sizes and some of the BFR parameters were revealed, though these correlations were not statistically significant (r=-0.205--0.261, P=0.108-0.211). Our results suggested that pulsed Doppler ultrasound could be successfully used to measure BFR in physiological conditions and to reveal the BFR relationship between lesion vessels and normal host vessels, as well as the relationship between the lesion sizes and the BFR.

The vascular network of tumours--what is it not for?

It is becoming almost a dogma that tumours cannot grow beyond 1-2 mm(3) unless they are supported by a rich vascular supply 1. It is true that tumours promote angiogenesis and that highly vascularized carcinomas have, in general, a more aggressive clinical course than carcinomas of low vascularization 23. However, a study of intratumoral angiogenesis reveals that the newly formed vessels are commonly deprived of those structural qualities that would allow them to perform an optimal oxygenation function 3. Thus, most tumours, irrespective of their angiogenic status, behave as if they were 'hypoxic', urging (via angiogenic mediators) for, what would look paradoxical at first sight, more defective angiogenesis. It is hypothesized that tumour cells can grow into solid neoplasms by exploiting the host's pre-existing vessels, without the need for new blood vessel formation. Neovascularization, however, may be important for tumours with an exophytic pattern of growth as these, by their very nature, lose the host's sheltering stroma. Shifting to anaerobic glycolysis and activation of anti-apoptotic pathways are complementary mechanisms for tumour cell survival and growth. Besides, continuous and indiscriminate production of a defective vascular network ensures an increased metastatic potential since the newly formed intratumoral vessels, simulating venular-like spaces, are easily permeable to tumour cells, facilitating metastases.

Differentiation of recurrent rectal cancer and scarring with dynamic MR imaging

The accuracy of dynamic contrast enhanced magnetic resonance (MR) imaging in the differentiation of malignant and benign pelvic lesions during follow-up of patients with treated colorectal tumours was evaluated prospectively. 19 patients (11 men, 8 women; age range 35-70 years; mean 57 years) with suspected local recurrence of colorectal malignancy were evaluated with MR imaging. Dynamic MR imaging with axial Turbo-FLASH gradient echo imaging and bolus injection of contrast medium was performed. Dynamic images, each consisting of one slice in the same location, were acquired at 5, 10, 15, 20 and 30 s, and at 1, 2, 3, 4, 5 and 10 min. The maximum change in signal intensity (Emax), the acceleration rate of the time-intensity curve (TIC) and the ratio of the signal intensity of the lesions to the signal intensity of the iliac artery (SIL/SIA) were used as the enhancement parameters. The TIC and SIL/SIA ratio at 60 s were found to be valuable in the differential diagnosis; Emax had no significance in differentiating benign and malignant lesions. Sensitivity was 83% for each calculated parameter. SIL/SIA has the highest specificity and accuracy among the parameters.

Microvascular structure of benign and malignant tumors of the colon in humans

Studies of experimental tumors in rodents indicate that there are morphological abnormalities of the tumor microcirculation compared to normal tissues. The aim of this study was to examine the structure of the microvasculature in benign and malignant colonic tumors in humans using microvascular casting techniques. There were 15 adenocarcinomas, four benign sporadic adenomas, and three specimens from patients with familial adenomatous polyposis (FAP). A cast of the microvessels of these tumors was prepared by intraarterial administration of acrylic resin (Mercox) and the cast examined by scanning electron microscopy. Quantitative measures of the microvasculature were obtained from histological sections using stereological techniques in four carcinomas, two sporadic adenomas, and 12 adenomas from patients with FAP. Vascular casts of benign colonic adenomas showed that the microvasculature had a similar organization to normal colon. However, capillaries and venules were elongated and had increased diameters compared to normal. In adenomas greater than 3 mm in diameter, there was an increased density of microvessels in the spaces between tumor cells. Vascular casts of colonic carcinomas were characterized by a disorganized structure and increased density of microvessels. The organization of microvessels within carcinomas had a similar overall pattern to normal colon. However, the increased number and density of microvessels resulted in formation of nodular clusters of capillaries, formation of "sheets" of frequently anastomosing capillaries, or almost complete packing of the interstitial spaces of the tumor by capillaries in places. Most capillaries had a long and tortuous course and numerous capillary sprouts were identified. Tumor microvessels had greater mean diameters than normal. Extravasation of resin from microvessels in carcinomas was frequently seen. The vascular volume of carcinomas (23.1% +/- 12.2), sporadic adenomas (16.3% +/- 3.4), and adenomas > 3 mm diameter in patients with FAP (17.7% +/- 3.0) were significantly greater than in normal colon (11.0% +/- 4.2). This study indicates that there is an increased vascular density in benign and malignant tumors of the colon compared to normal colon. The presence of profusely anastomotic microvessels and frequent capillary sprouts is evidence of active neovascularization and suggests control of tumor growth could be achieved by modifiers of angiogenesis.

Glomeruloid structures as vascular reaction in human gastrointestinal carcinoma

Malignant tumors induce angiogenesis and modulation of microvasculature. Based on histologic and immunohistochemical analysis of human surgical material, we describe here the occurrence of glomeruloid structures in gastrointestinal carcinomas, and compare them with the microvasculature in inflammatory granulation tissue. The glomeruloid structures were composed of clusters of mutually fused capillaries with prominent swelling of endothelial cells and pericytes. They were thought to be specific for glioblastoma of the brain. The glomeruloid structures were observed juxtaposed to carcinoma nests in one-third of gastric carcinoma of intestinal type and colorectal carcinoma in the area of invasive growth beyond the muscularis mucosae. They were not observed in gastric carcinoma of diffuse type, intramucosal carcinoma, or inflammatory granulation tissue. The glomeruloid structures can be regarded as an extreme example of endothelial hyperplastic changes observed in cancer stroma. Our results suggested that glomeruloid structures can occur in carcinomas as vascular reaction, a mechanism different from that in inflammatory granulation tissues.

Differing microvasculature in the two major types of gastric carcinoma: a conventional, ultrastructural and ultrastructural immunolocalization study of von Willebrand factor

The microvasculature of the stroma of human gastric carcinoma was studied by immuno-electron microscopy for factor VIII/von Willebrand factor (vWF) and conventional electron microscopy. In differentiated type (intestinal) gastric carcinoma (9 cases), capillaries were distributed more densely around carcinoma cell nests. vWF was localized in endothelial cells and neighbouring stroma. Ultrastructurally, capillary endothelial cells showed considerable hypertrophic changes with well-developed rough endoplasmic reticulum (rER). vWF was localized in well-developed rER, granules, Weibel-Palade bodies (WPB), in the vascular lumen as clusters, and diffusely deposited in the subendothelium. This indicates that endothelial cells in this group are transformed into a state of active protein production. In undifferentiated type (diffuse) gastric carcinoma (12 cases), capillaries were uniformly distributed and endothelial hypertrophic changes were less remarkable. vWF was localized in WPB, scanty rER and subendothelial matrix. Solid capillary buds were observed in both types; they were composed of a solid strand of endothelial cells without a visible lumen. Our results reveal that the microvasculature in tumour stroma differs significantly according to its histological type.

Effect of polarity and differentiation on antibody localization in multicellular tumour spheroid and xenograft models and its potential importance for in vivo immunotargeting

Two monoclonal antibodies (MAbs) AUAI and HMFGI recognize antigens located on different membrane domains of polarized epithelial cells. We have assessed the accessibility of these antigens in multicellular tumour spheroids produced in culture using a well-polarized (HRA-19) and a non-polarized cell line (LoVo) of human large-bowel carcinoma origin. Multicellular spheroids of HRA-19 cells develop polarity, so that the membrane which is in contact with the culture medium (apical) becomes antigenically distinct from the membrane facing the centre of the spheroids (basolateral). This was confirmed by immunostaining sections of spheroids with 2 MAbs, AUAI and HMFGI. AUAI recognizes an antigen located exclusively on the basolateral membranes of polarized epithelial cells, and stained only internal membranes in spheroid sections. Conversely HMFGI, which recognizes an antigen located on the apical membranes, stained only the periphery of the spheroids. These 2MAbs were then radiolabelled with 125I and incubated with live spheroids for 4 hr at 37 degrees C. Autoradiographs of spheroid sections showed a marked difference between the 2 MAbs. 125I-HMFGI-radioantibody localized exclusively on the spheroid surface in a pattern identical to the in vitro immunostaining pattern, while 125I-AUAI radioantibody showed no binding in spite of the uniform presence of antigen on all tumour cells basolaterally. This appeared to be the result of the inaccessibility of basolateral antigenic sites in well-polarized epithelial cells because of the tight junctions connecting these cells at their apical surfaces. In contrast to the HRA-19 cell line LoVo, spheroids do not develop polarity; as a result, when stained with AUAI, variable antigenic expression all over the cell surface was seen. Autoradiographs of these spheroids showed 125I-AUAI binding with a penetration to a depth of about 1-3 cells, while HMFGI which shows no reactivity with this cell line in vitro, did not bind. This phenomenon was further investigated in xenografts of the HRA-19 cell line. It was shown that in a well-differentiated adenocarcinoma where the tumour cells forming acini are arranged in a polarized fashion, the luminal antigenic sites may be inaccessible to the injected MAb. The striking differences in binding of MAbs on polarized and unpolarized tumours indicate the importance of cell polarization and exact location of antigenic sites for in vivo immunotargeting.

Microvascular changes in the stroma of human colorectal carcinomas: ultrastructural histochemical study

Ultrastructural histochemical studies were performed using Ulex europaeus agglutinin-I lectin (UEA-I) and anti-endothelial monoclonal antibody BMA 120 in order to morphologically characterize the microvasculature of human colorectal carcinomas. In the normal mucosa, UEA-I and BMA 120 were bound to luminal plasma membrane of endothelial cells, usually continuously. Capillaries in the stroma of invasive adenocarcinomas showed remarkable structural changes such as swelling of endothelial cells with well-developed cell organelles and narrowing of the lumen. Reaction products for UEA-I and BMA 120 were both observed along the luminal plasma membrane of endothelial cells, usually discontinuously, partially retaining the features of normal capillaries. Furthermore, we have confirmed an occurrence of solid capillary buds composed of a strand of large endothelial cells with a trace of lumen. They showed almost no reactivity to UEA-I and BMA 120. Conventional electron microscopy revealed that they were present frequently in invasive carcinomas, but infrequently in intramucosal carcinomas and inflammatory lesions. Our results suggest that the stroma of invasive colorectal carcinomas abounds in immature capillaries and their precursors, which may indicate active tumor-induced angiogenesis.

The vascular pattern of basal cell tumors: light microscopy and scanning electron microscopic study on vascular corrosion casts

Light microscopy of hematoxylin-eosin stained tissue sections and scanning electron microscopy (SEM) of vascular corrosion casts were used to study the blood vascular system of human basal cell tumors. Concerning the gross angioarchitecture there is a very close correlation between the histological appearance and the findings obtained from vascular corrosion casts, when evaluated in a SEM. The tumor cell beds are enveloped by basket-like capillary plexus. The tumors are traversed over long distances by superficially running, teleangiectatic, but flattened capillaries. These compressed vessels are squeezed between tumor cell cords and epidermis. In vascular corrosion casts of human basal cell tumors the vascular system exhibits three different features. Blind-ending vascular casts; Four different causes for blind-ending cast structures are pointed out and discussed. Incomplete filling of the vascular system; compression of tumor vessels; new proliferating capillary sprouts; broken cast endings. Variations in vessel caliber and extravasation of the injection resin. Most of the variation in vessel calibers are thought to be caused by dilation of the weakened endothelial walls, but some of them presumably represent new projecting vascular swellings. Circumscribed leakage of the injected resin could be attributed to regions of advanced connective tissue degeneration and endothelial lysis. Flattened cast structures; The addition of tissues during tumor growth results in an increase of tissue pressure. Thus many tumor vessels get displaced, compressed, and flattened and vascular occlusions will occur. However, it must be stressed that much caution is needed in assessing the nature of the vascular cast structures of basal cell tumors.