Antisense oligodeoxynucleotide inhibition of δ protein kinase C expression accelerates induced differentiation of murine erythroleukaemia cells

The potential regulatory role of δ protein kinase C (δPKC) in murine erythroleukaemia cell differentiation was studied by using antisense oligodeoxynucleotides targeting the translation initiation region of mouse δPKC mRNA. Cell treatment with antisense oligonucleotides, at a concentration of 20 μM, followed by hexamethylenebisacetamide induction, produced a specific 2-fold increase in the differentiation rate of both slowly and rapidly differentiating murine erythroleukaemia cell clones. Cell permeabilization by a cationic lipid resulted in a decrease of one order of magnitude in the amounts of antisense oligonucleotides necessary to elicit the maximal response, and accelerated the kinetics of the stimulatory effect. These changes in murine erythroleukaemia cell differentiation rates, observed in both cell clones, were associated with 60% and 50% decreases, respectively, in δPKC immunoreactive protein in slowly and rapidly differentiating cells. The present results indicate strongly that basal levels of δPKC in murine erythroleukaemia cells are essential in regulating the initial differentiation rate of these cells in response to chemical induction, and provide further evidence that this PKC isoform plays a fundamental role in maintaining the undifferentiated phenotype of murine erythroleukaemia cells.