Polymorphonuclear leukocyte-induced detachment of cultured epidermal carcinoma cells from the substratum

In an in vitro study, intended to develop tumoricidal therapy with the use of human leukocyte, an interesting phenomenon was found. Normal human polymorphonuclear leukocytes (PMN) plated on a cell line established from malignant trichilemmal cyst (DJM-1), a kind of squamous cell carcinoma, in a serum-free media and incubated for 48 h induced the detachment of DJM-1. The detachment was more extensive as the number of PMN increased. The detachment rate was 97.0% when the number of PMN and DJM-1 in a well was in a ratio 2.4:1 and the viability of detached DJM-1 was 96.5%. Two kinds of proteinase inhibitors, especially the inhibitor of neutrophil elastase, fetal bovine serum, and monoclonal anti-laminin antibody inhibited the detachment significantly. Furthermore, when PMN were seeded in a chamber with a filter membrane bottom to prevent direct contact with DJM-1, DJM-1 detachment decreased to 14.2%. In view of these results, the following mechanism was postulated. Activated by their adhesion to DJM-1, especially between laminin receptor on PMN and laminin on DJM-1, PMN secreted proteinases, resulting in DJM-1 detachment. This phenomenon might be an expression of cytotoxicity of PMN to cancer cells, because cultured cancer cells of epithelium origin such as DJM-1 can grow only after they are firmly attached to the substratum. This phenomenon, in turn, may explain the final step in the induction of epidermal-dermal separation in subepidermal bullous diseases with PMN infiltration such as bullous pemphigoid and dermatitis herpetiformis if we could regard DJM-1 as normal keratinocyte.