IN VITRO PROLIFERATION OF MOUSE LYMPHOBLASTOID CELL LINES: GROWTH MODULATION BY VARIOUS POPULATIONS OF ADHERENT CELLS

The in vitro growth pattern of a number of mouse lymphoblastoid tumour cell lines was modified in the presence of adherent cell layers from various sources. The AVRij-1 and ST-4b cell lines exhibited a concentration—dependent growth pattern, i.e., they would only grow well when seeded at high starting cell concentrations. Better growth of these cells from low cell concentrations was observed in the presence of adherent cell layers from syngeneic or allogeneic bone marrow. Adherent cell layers derived from mouse spleen and pleural or peritoneal cavity could also promote the growth of the above tumour cells, but in a narrower range of cell concentrations and to a lower extent. Moreover, confluent adherent layers from the pleural and peritoneal cavities completely inhibited the growth of AVRij-1 and ST-4b cells, while adherent cell layers from the bone marrow did not inhibit growth at any cell concentration tested. The in vitro growth of concentration—independent cell lines was also affected by the presence of adherent cells from the bone marrow. Under syngeneic conditions, a slight increase in the growth of the ‘null’ or pre-B lymphoma cell line ABLS-8.1 was observed. On the other hand, the growth of tumour cells expressing more differentiated properties, such as the thymus T lymphoma tumour cell line ST-1.3 and the plasma cell tumour MPC-11.45.6.2.4, was inhibited in the presence of syngeneic bone marrow derived adherent cell layers. This inhibition was more pronounced under allogeneic conditions. Growth inhibition was also observed when concentration—independent cell lines were co-cultured with adherent cells from the pleural and peritoneal cavities. Thus, adherent cell layers from non-haemopoietic sources inhibited the growth of all cell lines tested. On the other hand, adherent cells from the bone marrow had a differential effect on growth of lymphoblastoid tumour cell lines. This depended on the in vitro growth properties of each tumour cell line and on some additional specific tumour cell properties. The latter could relate to the differentiation stage characterizing each tumour cell line. The culture method described here may serve as a model system for studies on interaction of leukaemic cell and the haemopoietic microenvironment.