A cytochemical and immunological study of tumour cells
Initial tumour growth was found to be exponential following intraperitoneal inoculation of 5 x 106 Ehrlich ascites tumour cells into male BALB/c mice. After three days of this pattern the rate of growth became noticeably retarded and after 12 days a plateau phase ensued. The reduced growth rate was shown to be an immediate consequence of an Increase In the duration of the cell cycle, In the fraction of non-cycling tumour cells and in cell loss. Evidence is presented to suggest that during plateau phase of tumour growth the 3O state does not represent a preferential pathway leading to cell death. Repeat tritiated thymidine labelling was used to identify non-cycling cells during the plateau phase of tumour growth and to demonstrate their ability to return to rapid cyclic activity when 'Lebensraum’ was increased. Subsequently individual cell DNA, RNA and protein relative contents were determined miorodensitometrically for non-cycling (Co) and rapidly cycling tumour cells. Reduced protein and RNA levels were found to be a feature of Co tumour cells. Microdensitometric estimation of the DFA profile for the tumour cell population at various stages during tumour growth revealed that an increase in the proportion of heteroploid tumour cells was concomitant with tumour growth, a finding not supported ty chromosome analysis. This factor may be involved in the reduction in tumour growth rate. Following production of anti-Ehrlich ascites tumour antiserum, flow cytofluorimetric and combined immunofluorescent-autoradiographic analyses were carried out. These analyses failed to reveal gross antigenic changes associated with Co phase.
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