Biological properties of the human colonic adenocarcinoma cell line SW 620 grown as a xenograft in the athymic mouse

Abstract

The biological and cell kinetic properties of the poorly differentiated human colonic adenocarcinoma cell line SW 620 grown as xenografts in BALB/c athymic mice are described. The SW 620 cells consistently produced tumors when inoculated i.v., i.p., and s.c. The lowest cell inoculum requirements were seen i.p. where 10(7) cells produced a 100% incidence. Intravenous inocula (10(5) to 10(8) cells) produced microscopic lung colonies within 30 days, becoming macroscopic nodules after 60 days. Subcutaneous tumors exhibited a marked Révész effect, using a thromboplastic brain extract which increased both tumor incidence and growth rate. All SW 620 xenografts presented a poorly differentiated morphology with extensive necrotic foci. No metastatic involvement was noted in any murine tissues. No demonstrable levels of carcinoembryonic antigen were present in the sera of animals bearing s.c. xenografts greater than 5.0 cu cm. Early SW 620 xenografts (0.3 to 0.6 cu cm) exhibited a characteristically human cell kinetic profile (Tc congruent to 34 to 43 hr; Ts congruent to 22 hr), with a growth fraction of 30.5% as measured by the primer-available DNA polymerase-index and a high cell loss factor (45%). Among late xenografts (1.1 to 1.6 cu cm), the kinetic events noted were an increase in the Tc, cell loss and, unexpectedly, an increase in the primer-available DNA polymerase index. A colony formation assay was established with the use of mechanical mincing plus collagenase (150 IU/ml; 37 degrees; 30 min), which produced a mean plating efficiency of 33.6 +/- 7.2% (S.E.) for s.c. xenografts (range, 14.6 to 51.0%). The SW 620 xenograft model possesses the biological and cell kinetic profile of many human colonic adenocarcinomas in situ. These properties, coupled with the capacity for large-scale xenograft production, should provide a clinically relevant model for the screening of potential antitumor agents and procedures.