Arrigo Benedetto

Prostaglandin A1 induces differentiation in friend erythroleukemia cells

The effect of different prostaglandins and prostaglandin-metabolites on the growth and differentiation of Friend erythroleukemia cells (FLC) was evaluated. The prostaglandin-metabolites, thromboxane B2 and 6-keto PGF1 alpha, were completely inactive, while PGE1 inhibited slightly and PGF2 alpha stimulated the replication of FLC. PGA1 was found to be the most active compound. It profoundly inhibited the replication of both DMSO-treated and undifferentiated FLC. Most importantly, PGA1 alone induced differentiation in FLC, stimulating hemoglobin production over a five-day period. PGA1-stimulated differentiation was completely suppressed by the addition of 10(-6)M hydrocortisone. Finally, treatment of DMSO-differentiated cells with PGA1 (but no DMSO) prevented the return to the undifferentiated state.

Hydrocortisone inhibits DMSO — induced differentiation of friend erythroleukemia cells☆

Abstract Hydrocortisone (10 −6 – 10 −7 M) completely inhibited the production of hemoglobin by DMSO- and DMF-treated Friend erythroleukemia cells (FLC) in vitro without affecting either cell replication or general protein synthesis. Only 11, 17-dihydroxycorticosteroids were effective in inhibiting this expression of differentiation. Addition of hydrocortisone as late as 48 hours after the addition of DMSO (at a time at which cells were committed to differentiation) still resulted in significant inhibition of hemoglobin synthesis. Although the mechanism of this action is unknown, since it was not reversed by the addition of arachidonic acid nor a number of prostaglandins, it appears to be unrelated to the ability of corticosteroids to inhibit endogenous prostaglandin synthesis.

Wheat germ agglutinin-binding protein changes in highly malignant Friend leukemia cells metastasizing to the liver.

We have used binding of radioactive lectins (i.e. Concanavalin A (ConA), Wheat Germ Agglutinin (WGA) andRicinus communis agglutinin I (RCAI)) to membrane glycoproteins separated in SDS gel electrophoresis, to detect specific carbohydrate changes in plasma membrane proteins ofin vivo passaged Friend erythroleukemia cells (FLC). These cells are highly metastatic to the liver, whereas the originalin vitro passaged tumor cells do not metastasize. Marked qualitative differences in the high molecular weight region of the gels (100–200 kD) were observed between the WGA binding glycoproteins of metastaticin vivo passaged FLC and nonmetastaticin vitro passaged FLC. Furthermore, the binding of WGA to plasma membrane proteins ofin vivo passaged FLC was much greater than the binding of WGA to plasma membrane proteins ofin vitro passaged FLC. Lectin binding experiments after sialic acid removal byin situ mild acid hydrolysis of FLC glycoproteins indicated that an increased sialylation of the 120 and 145 kD glycoproteins was responsible for the increased WGA reactivity ofin vivo passaged FLC plasma membranes. Besides the increased sialylation, other changes in glycosylation of the 100–200 kD glycoproteins ofin vivo passaged FLC were observed: (1) qualitative differences between the WGA binding patterns of the two cell types were restored after treatment of the gels with mild acid and subsequent Smith degradation; (2) after chemical removal of sialic acid residues from the gels, qualitative differences in the RCA binding patterns to the glycoproteins of the two cell types were apparent.

Sendai virus replication in Friend erythroleukemia cells. I. Acutely and persistently infected cells become resistant to virus-induced lysis

Friend leukemia cells (FLC) are susceptible to infection by Sendai virus, a member of the paramyxovirus group. FLC constitute a most suitable model to study virus-host cell interactions, because they grow in suspension (thus avoiding the use of trypsin), and provide an easy way of deriving single-cell clones. When FLC are infected with Sendai virus at high m.o.i., a direct, extensive lysis of the cells ensues, whereas lower doses of virus result in a cytocidal infection whose lethality depends mainly on the virus used, standard or defective interfering egg-grown Sendai virus (EGSV), and on the multiplicity of infection (m.o.i). At later times after infection, FLC become resistant to the Sendai induced lysis (SIL). The SIL resistance can be maintained in single-cell clones that had survived the first infection. The maintenance of the resistant phenotype of the clones requires the serial subcultivation of the cells in the presence of activated EGSV. The mechanisms that presumably regulate the appearance of SIL resistance in Sendai infected FLC are discussed.