Colonic cell proliferation in two different ethnic groups with contrasting incidence of colon cancer: is there a difference in carcinogenesis?

Most studies on colorectal carcinogenesis suggest a field defect, preceding overt development of cancer. The low incidence of adenomatous polyps in the African population, however, suggests that there may be an alternative route for cancer development. The aim of the study was to discover if the difference in incidence of colorectal cancer in Africans compared with the white population is reflected in a different pattern of cell proliferation. Histological normal mucosa from 30 patients (15 white South African (W), 15 South African Africans (A)) with confirmed colon cancer were examined. Proliferating cells were detected using the Ki-67 antigen. In addition, cell proliferation data were obtained, from 30 age matched controls (15 Africans, 15 white South Africans), without colorectal disease. The African controls were significantly younger (mean (SD) (A: 42 (20), W: 66 (13), p < 0.05)) than the white controls. The second control group had a significantly higher mean (SD) total labelling index (W: 11 (3), A: 6 (4), p < 0.05). In addition the proliferative pattern of the white group without evidence of colorectal cancer showed a comparatively large amount of dividing cells in compartment 2, compared with African controls (mean (SD) (W: 21 (8), A: 9 (8), p < 0.05)). Mucosa from Africans with cancer showed a proliferative pattern with the same increased total labelling index (A: 15 (5), W: 16 (6), p = NS, phase II proliferative lesion) and an even more pronounced upward expansion (phase I proliferative lesion) compared with white cancer patients. This suggests that the mechanism of colorectal carcinogenesis is similar in Africans and the white population. The lack of clinical evidence of the adenoma-carcinoma sequence, and the incidence of cancer at a comparatively young age in Africans may be explained by the fact that colorectal cancer in this ethnic group behaves more aggressively and that adenomatous polyps are rapidly converted into overt cancer before detection.

Amplification and expression of the TGF-alpha, EGF receptor and c-myc genes in four human oesophageal squamous cell carcinoma lines.

We have previously shown that four human oesophageal squamous cell carcinoma (SCC) cell lines secrete significant quantities of transforming growth factor alpha (TGF-alpha) in vitro. Three of these lines are known to produce supernumerary low-affinity epidermal growth factor receptors (EGF-Rs). Using an 125I-EGF competitive binding assay and Scatchard analysis, we show that the fourth also overproduces low-affinity receptors. According to slot blot DNA analyses, the secretion of high levels of TGF-alpha is not associated with amplification of the TGF-alpha gene, and hyperproduction of the EGF-R is correlated with receptor gene amplification. Western blot analyses show that the c-Myc protein is overexpressed in two of the cell lines; and Southern and Northern blot analyses indicate that this overexpression occurs independently of c-myc gene amplification. Our results are consistent with an autocrine role for TGF-alpha and EGF-R in oesophageal carcinogenesis and support the possibility that c-myc overexpression may be required for the in vivo tumourigenicity of cells that produce high levels of TGF-alpha and the EGF-R.

Case report: radiotherapy--an effective treatment for vaginal verrucous carcinoma.

Vaginal carcinoma makes up 1%-2% of all gynaecological tumours. Verrucous carcinoma of the vagina is even more rare--only 16 cases are reported in the scientific literature. A case of a complete regression after 60 Gy fractionated radiotherapy by a tumour 12 cm3 in size is reported. Most authors are of the opinion that radiotherapy causes anaplastic transformation of verrucous carcinoma. The minority view, that anaplastic transformation does not occur, is correct and is supported by our clinical and radiological data. The conflicting literature on vaginal verrucous carcinoma (VVC) is reviewed with reference to verrucous carcinoma at other sites.

In vitro secretion of transforming growth factor alpha (TGF-alpha): a comparison of the A431 cell line with three human oesophageal squamous cell carcinoma lines.

Transforming growth factor alpha (TGF-alpha) is a single chain polypeptide which exists in a variety of forms differing in molecular weight. These forms are variously present in normal and neoplastic cells. Of particular interest are TGF-alpha's well-known mitogenic properties. The transition from a normal to a neoplastic cellular state results from signalling defects that may depend upon, inter alia, abnormal levels of expression and secretion of TGF-alpha. It is known that the secretion of TGF-alpha may be enhanced appreciably by agents such as phorbol 12-myristate 13-acetate (PMA), serum factors and epidermal growth factor (EGF). Here, we compare the efficacy of these three agents in the elevation of TGF-alpha secretion in the well studied A431 cell line with their previously undocumented efficacy in certain interesting, but little known, human oesophageal squamous cell carcinoma (SCC) lines.

Paraneoplastic paralysis in a patient with malignant fibrous histiocytoma.

A patient presented with lower limb paralysis and a large malignant fibrous histiocytoma (MFH) on her back. Metastatic disease to the spine was excluded and the diagnosis of paraneoplastic paralysis was made. This may be the first described case of a neuromyopathic paraneoplastic syndrome in malignant fibrous histiocytoma. Tissue culture and electron microscopy assisted in establishing the diagnosis of the tumour. A hitherto unrecognised endocrine factor may account for the hypokalaemia which was a feature in this patient.

Quantitation of autoantibodies to cytokeratins in sera from patients with squamous cell carcinoma of the oesophagus.

Sera drawn from healthy individuals, patients with squamous cell carcinoma (SCC) of the oesophagus and patients with mild active oesophagitis were examined for autoantibodies to cytoskeletal proteins extracted from the normal oesophageal keratinocyte or from 2 carcinoma cell lines, each of the latter have a simple cytoskeleton. Using a radioimmunoassay with normal oesophageal cytokeratins as bound antigen, 86 normal, 76 SCC and 14 oesophagitis sera were compared. No significant difference in autoantibody titre was found. When the bound antigen was changed to one containing predominantly simple epithelial cytokeratins a significant increase (32% P less than 0.001) was noted in the SCC category only. Western blots using simple epithelial cell extracts as antigen revealed autoantibodies to cytokeratins 8, 18 and 19 as well as to one other unidentified protein in most SCC sera, and in some normal sera. Antibodies to cytokeratin 18 predominated. Normal and SCC sera were applied using indirect immunofluorescent techniques to normal oesophageal keratinocytes, SNO oesophageal SCC cells and HeLa cells grown in vitro. Autoantibodies to oesophageal cytokeratins were, with few exceptions, barely detectable. Strong reactions were noted against SNO and HeLa cytoskeletal components, but also against nuclear membrane and nucleolar determinants. These experiments suggest that raised levels of autoantibodies to certain cytoskeletal and nuclear determinants may be a feature of oesophageal cancer.

Cross-contamination of human esophageal squamous carcinoma cell lines detected by DNA fingerprint analysis.

DNA "fingerprint" analysis has recently become known as a valuable technique for positive identification of any given individual. The chances for mistaken identity have been estimated to be 10(-6) for close siblings or as little as 10(-23) for randomly selected individuals. This methodology thus represents a significant improvement over previously established identification tests using protein or enzyme analysis techniques and has already found application in forensic medicine. One of the chief problems in tissue culture studies is the question of the unequivocal identity of the cultured cells used and the very real possibility of their being contaminated by cells of a similar morphological appearance. We report here the application of the DNA "fingerprint" technique to the genotypic analysis of cultured human squamous carcinoma cells. The results show that a number of lines, designation HCu, have become cross-contaminated. Lines SNO, HCu 10, and HCu 13 are genetically distinct, however lines HCu 10, 18, 33, 37, and 39 are genetically identical and are in fact subcultures of the same cells. In addition, a myocardial line known as Girardi is shown to be identical to HeLa cells. The introduction of this technique to tissue culture laboratories could therefore prevent contaminated cultures from being disseminated or used in research studies.

Cell proliferation kinetics of epidermis and sebaceous glands in relation to chalone action.

Median S-phase lengths of pinna epidermis and sebaceous glands, and of epithelia from the oesophagus and under surface of the tongue of Albino Swiss S mice were estimated by the percentage labelled mitoses method (PLM). The 18.4 and 18,8 hr for the median length of S-phase for pinna epidermis and sebaceous glands respectively made it possible for these two tissues to be used experimentally for testing tissue specificity in chalone assay experiments. The 10.0 and 11.5 hr for oesophagus ang tongue epithelium respectively made experimental design for chalone assay difficult when pinna epidermis was the target tissue. The results of the Labelling Index measured each hour throughout a 24-hr period showed no distinct single peaked diurnal rhythm for pinna epidermis and sebaceous glands. Instead a circadian rhythm with several small peaks occurred which would be expected if an S-phase of approximately 18 hr was imposed on the diurnal rhythm. This indicates that there may be very little change in the rate of DNA synthesis. The results are given for the assay in vivo of purified epidermal G1 and G2 chalones, and the 72--81% ethanol precipitate of pig skin from which they could be isolated. These experiments were performed over a time period which took into account the diurnal rhythm of activity of the mice as well as the S-phase lengths. Extrapolating the results with time of action of the chalone shows that the G1 chalone acts at the point of entry into DNA synthesis and that the S-phase length was approximately 17 hr for both the pinna epidermis and sebaceous glands. This may be a more correct value since the PLM method overestimates the median S-phase length as it is known that in pinna skin the [3H]TdR is available to the tissues for 2 hr and true flash labelling does not take place. The previous reports that epidermal G1 chalone acts some hours prior to entry into S-phase resulted from experiments on back skin where the S-phase is shorter and there is a pronounced diurnal rhythm which could mask the chalone effect. The epidermal G2 chalone had no effect on DNA synthesis even at different times in the circadian rhythm. Thus the circadian rhythms and S-phase lengths of the test tissues need to be considered when experiments are performed with chalones. Ideally, the target tissues selected for cell line specificity tests should have the same cell kinetics for the easier and more accurate assessment and interpretation of results. When the tissues have markedly different cell kinetics, experimental procedures and results need to be evaluated accordingly. The point of action of G1 chalone can only be assessed if the effect is measured over the peak of incorporation of [3H]TdR into DNA. The results of the effects of skin extracts are analysed in relation to changes in the availability of [3H]TdR for the incorporation into DNA and to the possibility of there being two distinct populations of proliferating cells.

A simple method for measuring DNA synthesis in epidermis and sebaceous glands and its application in chalone assays.

Liquid scintillation counting and autoradiography were used to measure DNA synthesis (3H-TdR uptake and incorporation) by the epidermis and the sebaceous glands in mouse pinna skin. Using this approach it has been possible to show that a chalone-like inhibitor of DNA synthesis acts rapidly to restrict the flow of epidermal G1 cells into S-phase. The point of action within the cell cycle is probably at the G1-S phase 'boundary'. The technique described is sufficiently sensitive to be used for measuring small alterations in DNA synthesis in short-term experiments and for long-term experiments in which the size of the progenitor cell population is altered by systemic or topical administration of compounds influencing DNA synthesis.

Chalone regulation of the epidermal cell cycle.

Purified epidermal G2 chalone does not inhibit DNA synthesis or influx of S-phase cells and is therefore cell cycle phase-specific, inhibiting only the flow of cells into M-phase.