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The proteins of solid lung tumours (15 adenocarcinomas and 10 squamous cell carcinomas) were examined by high resolution two-dimensional electrophoresis (2-DE) and compared with the proteins of adjacent lung tissue which demonstrated no histological evidence of malignant transformation, and with the proteins of other malignant tumours and normal tissues. To investigate tumour cell-specific protein synthesis, we isolated malignant and normal cells enzymatically with collagenase, elastase, and DNase. Tissue and tumour cells were enriched in an additional step on a Percoll gradient. The 2-DE gel patterns derived from entire tissue and enriched tissue cell preparations were compared. No specific differences were found between the 2-DE protein patterns from adenocarcinomas and squamous cell carcinomas of the lung, but three proteins identified on the 2-DE gels appeared to be tumour-associated. Spot A is present in non-neoplastic and neoplastic epithelial tissues. Spot B is pronounced in 2-DE gels of sarcomas, but is also present in preparations of other malignant tissues. Spot C is present in all malignant cell preparations. These three spots were also demonstrated in 2-DE protein patterns from tissue cultures of malignant cell lines. Spot B and spot C were also present in some normal tissues.

We have previously described a monoclonal antibody (BU-1) to 5-bromo-2-deoxyuridine (BrdUrd) that is useful for measurement of cell cycle S-phase. BU-1 hybridoma supernatant reacted with incorporated BrdUrd after the cells had been ethanol fixed; without a requirement for acid or base denaturation. We have found that this reactivity is lost if purified antibody is used, if the culture supernatants are heated, or if a mycoplasma-free hybridoma line is isolated. The supernatant contained endogenous DNase activity that was a result of mycoplasma infection of the cell line. This DNase activity was required for staining the cells with BU-1 in the absence of other denaturation steps. The endogenous DNase could be substituted for by the addition of bovine pancreatic DNase I. The disruption of the double stranded DNA structure with an enzyme rather than with harsh chemical or heat treatments does not affect protein structure or cellular morphology and allows the detection of incorporated BrdUrd of morphologic or antigenic cell subsets. DNase pre-treatment may also be useful for detection of other 'hidden' DNA antigens.

The protein pattern of cerebrospinal fluid (CSF) of 334 patients with various neurological and systemic diseases was investigated by high resolution two-dimensional electrophoresis (2-DE). 2-DE gels of normal CSF contain proteins which are not detectable in 2-DE gels of serum. Disturbances of the blood-brain or blood-CSF barrier, and degenerative diseases of the brain and malignant diseases produce specific changes on 2-DE gels of the CSF. The appearance of 10 spot areas in the light chain region of 2-DE gels seem to be connected with the diagnosis of multiple sclerosis. The sensitivity and the specificity of these spot areas for the diagnosis of multiple sclerosis are described. Proteins within the ten spot areas are immunoglobulin light chains or substances which cross-react very strongly with light chain antibodies as demonstrated by immunoblotting and immunoabsorption.