Environmental modulation of alpha(v), alpha(2) and beta(1) integrin subunit expression in human oesophageal squamous cell carcinomas.

Integrins are cell adhesion molecules pivotal in regulating normal cell behaviour. Ectopic expression of integrins, characteristic of transformed cells, is instrumental in differentiation, proliferation, apoptosis, angiogenesis, matrix degradation and migration. Oesophageal squamous cell carcinoma (SCC) has a propensity to metastasize and hence an extremely poor prognosis. It is shown here that oesophageal SCCs express alpha(v)strongly and that normal oesophageal tissue does not express alpha(v). This makes alpha(v)a significant indicator of the transformed phenotype. alpha(2)and beta(1)integrin subunits are down-regulated in oesophageal SCCs compared to normal oesophagus. Dominance of the alpha(2)beta(1)heterodimer is symptomatic of potential loss of other beta(1)binding integrins in oesophageal SCCs. These results suggest a decrease in rigid cell adhesion possibly increasing migratory potential, whilst simultaneously permitting the adhesion and migration of SCC cells on a large repertoire of ligands due to de novo alpha(v)expression.

Chloroquine-resistant isolates of Plasmodium falciparum with alternative CG2 omega repeat length polymorphisms.

A particular polymorphism in the cg2 gene has previously been linked to chloroquine resistance in reference isolates of Plasmodium falciparum. To assess the association of this polymorphism with chloroquine resistance in field specimens of P. falciparum, we analyzed the omega repeat region of the cg2 gene in 47 isolates of P. falciparum collected in the Ingwavuma District of northern KwaZulu-Natal, South Africa. Polymerase chain reaction (PCR) primers, which were designed to amplify the region of DNA surrounding the omega repeat, were used to obtain omega repeat PCR products from the field isolates. The PCR product for each isolate varied in length, depending on the number of cg2 omega repeats for that isolate. We found that several in vivo and in vitro chloroquine-resistant isolates of P. falciparum did not have the expected 16 omega repeats. These results suggest that the link between the cg2 polymorphism and chloroquine resistance identified previously may not apply in all malarious areas.

Cytopathogenicity of clinical and environmental Acanthamoeba isolates for two mammalian cell lines.

The cytopathic effect (CPE) of southern African, British, and an Asian strain of Acanthamoeba was assessed using a system developed around 2 different mammalian cell (MC) lines. The time taken by the amebae to destroy cell cultures completely was shown to be dependent largely on the size of the amebic inoculum and the cell type. This highlights the need to assess carefully the behavior of cell lines prior to using them for cytopathic testing. Assays performed with conditioned medium collected from both MCs and amebic cells indicated that mechanical destruction may have been primarily responsible for the CPE. Furthermore, not all strains of Acanthamoeba lose cytopathogenicity after being passaged in axenic culture for extended periods. The use of MC cultures was shown to be an accurate, rapid, and repeatable means of assaying the CPE of strains of Acanthamoeba.

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.

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.