ABSTRACT
The ability of cultured cell lines to form colonies in soft agar has long been considered an important correlate of tumorigenicity. The significance of the ability of primary human tumor cells to grow in an anchorage-independent manner is more controversial. The human tumor cloning assay has been extensively used by my laboratory to explore the possible influence of host cells on tumor colony proliferation. The definitive biochemical identity of the colony-stimulating activity in the MO-CM that enhanced SW-13 growth remains unknown. However, it is likely the activity was due to either II-1 or fibroblast growth factor, or combinations thereof. These factors may play a role in regulating growth or clonogenic cells in vivo.
