Demonstration of site-specific tumour growth by a 50% end point assay.

Tumour growth arising after injection of cell suspensions derived from four commonly used experimental tumours has been examined both in lung tissue and at the SC site. From tumour incidence data TD-50 values were computed for growth at the two sites and compared statistically. It was observed that Mc7 and Sp24 cell suspensions grew better in lung tissue than at the SC site, whereas the converse was true for Walker 256 cell suspensions. It would appear that immunogenicity, cell size, capacity to elicit platelet aggregation and immediate arrest patterns in lung tissue are individually inadequate to explain why certain tumour cells exhibit a potential for growth in lung tissue greater or less than at the SC site.