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- Title
Induction of EL<sub>4</sub> cell resistance to syngeneic macrophage-mediated lysis by protein kinase <em>C</em> ligands; effects of cultured TPA-treated target cell and protein phosphorylation.
- Authors
Essani, N.; Fishman, M.
- Abstract
Pretreatment of EL4 cells with 12-O-tetradecanoyl phorbol- 13-acetate (TPA) for 30 mm renders them resistant to lysis by activated macrophages (Mø). This resistance was augmented two to three-fold when TPA-trated EL4 cells were incubated for 2-6 hr prior to co-culture with Mø. Preincubation of TPA-treated cells for 24 hr could result in 100% resistance. In this paper we show that an endogenous ligand for protein kinase C, oleolyl-2-acetate glycerol (OAG), was capable of inducing tumour cell resistance to Mø kill and, similar to the effects seen with TPA, OAG did not affect the selective binding of tumour cells to activated Mø. Another important observation on the mechanism of TPA induction of tumour cell resistance was that once the target cells were progranuned to die after a minimal contact with activated Mø of 4-6 hr, TPA treatment was ineffective in altering the percent lysis 20 hr later. To investigate whether any possible correlation exists between TPA-induced protein phosphorylation and acquisition of resistance, EL4 cells were labelled with 32P and treated simultaneously with TPA, and cellular proteins were resolved by two adimensional gel electrophoresis. Eight polypeptides (MW 24,000-70,000, p1 48-61) showed consistent increased phosphorylation as a result of WA treatment. One-minute exposure with TPA resulted in enhanced phosphorylation of only four peptides (MW 39,000, 58,000, 63,000, 70,000) while all eight polypeptides showed increased phosphorylation by 10 mm.
- Subjects
MACROPHAGES; PROTEIN kinases; LIGANDS (Biochemistry); PHOSPHORYLATION; PHORBOLS; CANCER cells
- Publication
Immunology, 1988, Vol 65, Issue 2, p165
- ISSN
0019-2805
- Publication type
Article