Retroviral interleukin 5 gene transfer into interleukin 5‐dependent growing cell lines results in autocrine growth and tumorigenicity

Abstract

Two interleukin 5 (IL5)-specific retroviral expression vectors have been constructed containing the neomycin gene as selectable marker and either the mouse IL5 cDNA region or the rat genomic IL5 gene under the control of the thymidine kinase promoter. High viral titer supernatants derived from the transfected or infected packaging cell line psi 2 were used to infect the two cell lines B13 and T88M whose growth is dependent on exogenous IL 5. Infection resulted in G418 resistance and IL 5-independent growth with a high frequency. Clones were established which secrete between 2 and greater than 1000 U IL5. The proliferation of the IL5 autocrine growing cells could be inhibited by an antibody directed against the IL5 receptor indicating that they grow as a result of the endogenously produced IL5. Regardless of the amount of IL5 they produced, all of the clones were highly tumorigenic in nucle mice. The phenotype of the tumors was indistinguishable from that of the injected cells. T88M or B13 cells infected with a control virus neither produced IL5, nor became factor independent, nor produced tumors. Together, the IL5 gene transfer and expression into IL5-dependent growing cells are in accordance with the "autocrine growth" hypothesis and contrast analogous experiments with IL4.

Eosinophils infiltrating interleukin‐5 gene‐transfected tumors do not suppress tumor growth

“…The mouse IL-5 cDNA fragment was obtained by PCR from the vector pXT.IL-5 [19] as described [20] with primers specific for positions 34 to 51 and 437 to 455 supplemented with Bam HI recognition sites (5' TAG GAT CCT TCA GAG TCA TGA GAA G 3' and 5' GCG GAT CCA GCT CAG CCT CAG CCT T 3') [21]. The 436-bp PCR product was cloned into the Bgl I1 site of the plasmid pLTR in sense (pLTR.IL-5 S) and antisense (pLTR.IL-5 AS) orientation, placing the IL-5 gene 3' of the Moloney murine leukemia virus long terminal repeat [20].…”