Differential expression of adhesion molecules (CD44, ICAM-1 and LFA-3) in cancer cells crown in monolayer or as multicellular spheroids

Multicellular tumor spheroids have been used to examine numerous aspects of tumor biology since they often recreate the in vivo tumor environment much more closely than other models. Since the three-dimensional organization o f cancer cells into spheroids is based upon cell-cell interactions which ap pear dramatically different in spheroids with respect to monolayer cultures , it can be hypothesized that a modulation in the expression of the molecul es which are directly responsible for cell-cell and cell-matrix interaction s, particularly the cell adhesion molecules (CAMs), may be involved. In ord er to test this postulate, the expression of three important CAMs involved in tumor processes (CD44, ICAM-1 and LFA-3) in the human cancer cell lines HT29 (colon adenocarcinoma), A431 (squamous epidermal carcinoma) and A2780 (ovarian carcinoma) grown in monolayer or as multicellular spheroids was co mpared. The results demonstrate that only two of the lines (HT29 and A431) formed spheroids after six days of gyratory culture while A2780 cells did n ot form such structures after up to 8 days of culture. In the two cell line s which did form early phase multicellular spheroids, flow cytometric analy sis revealed that important differences exist between the same cells grown in monolayer and as spheroids in the quantity of expression of CAMs.