REEVALUATION BY IMAGE-ANALYSIS OF THE EFFECTS OF FIBROBLASTS, FIBRONECTIN OR LAMININ UPON COLONY FORMATION IN MOUSE LUNGS BY B16 MELANOMA-CELLS

A recently described personal method based on image analysis of histol ogical sections was used in order to quantify lung colony formation by B16 melanoma cells injected intravenously into the mouse. These tumor cells were preincubated in vitro either with fibronectin (FN), lamini n (LN) or fibroblasts (FB), which are implicated in the process of inv asion and metastasis. Thanks to this method, a more accurate analysis of lung colonies (section area and number) formed by tumor cells was r ealized. By image analysis, we show that when FB were mixed with B16 c ells, a drastic increase of tumor sections number and area was induced . LN increased the tumor sections area, but not their number. No effec t of FN on B16 cells was observed. LN and FN promoted tumor anchorage in the depth of the lungs while FB reduced the latter. These facts cou ld explain the contradictory results obtained by simply counting macro scopically superficial lung colonies. When cultured in vitro, these B1 6 melanoma cells did not produce any type of IV collagenase, either al one or in the presence of LN or FN, but in cocultures (B16 with 3T3) a nd in fibroblasts cultures, this enzyme was present. This could explai n, among other factors, why the rate of invasiveness exerted by B16 ce lls is higher when the latter are coinjected with FB.