Regulation of interleukin‐6 expression in the lymphoma cell line OCI‐LY3

Previously we described a cell line OCI‐LY3 derived from a patient with non‐Hodgkin's lymphoma. The cell line produced interleukin‐6 (IL‐6) mRNA and protein and demonstrated an autocrine pattern of growth for IL‐6. Southern blot analysis of the IL‐6 gene did not reveal any rearrangement. To determine whether the production of IL‐6 by OCI‐LY3 was due to subtle changes in the promoter of IL‐6 or due to the expression of trans‐acting factors chloramphenicol acetyltransferase (CAT) reporter constructs containing from ‐1, 180 to + 13 to ‐112 to + 13 of a normal IL‐6 gene were elecroporated into the cell line. When these constructs are transferred into unstimulated fibroblasts, no CAT activity is seen; however, CAT activity is induced when the cells are stimulated with either IL‐1α, lipopolysaccharide (LPS), or cyclic adenosine monophosphate (cAMP) analogues. When the cell line OCI‐LY3 was transfected with these constructs, CAT activity was observed; it was not necessary to stimulate the cells with exogenous factors to observe this activity. No CAT activity was observed in a second lymphoma cell line, OCI‐LY13.1, that does not produce IL‐6. These results suggest that the constitutive production of IL‐6 by the cell line OCI‐LY3 is due to the presence of trans‐acting factors that stimulate the expression of IL‐6 and not due to a cis‐acting mutation of the IL‐6 promoter.