Phorbol Ester Receptors and the Induction of Differentiation in the Human T Lymphoblastic Cell Line MOLT-3

Abstract

To examine the mechanism of induction of differentiation in the human malignant T-lymphoblastic cell line, MOLT-3, by 12-O-tetradecanoylphorbol-13-acetate (TPA), the role of receptors for phorbol esters was investigated. Binding of [20–³H]-phorbol-12,13-dibutyrate to TPA-resistant subclones derived from MOLT-3 was less than50 % of that of the parental MOLT-3. Scatchard analysis showed that the concentration of phorbol ester receptors in a TPA-resistant subclone was about 50% of that in the parental MOLT-3, but affinities of binding were similar, indicating that more than a certain number of phorbol ester receptors is required to induce differentiation by TPA in this human T cell line.

Activation of protein kinase C induces differentiation in the human T-lymphoblastic cell line MOLT-3

“…These results indicated that the TPA-resistant subclones were not induced to differentiate by TPA and remained immature. In previous work, we found that the amount of phorbol ester binding to TPA-resistant subclones from MOLT-3 was about half that of the parental MOLT-3, presumably due to a low concentration of receptors for phorbol esters, as assayed by Scatchard analysis (Mayumi et al, 1988). Thus, we concluded that the number of receptors for phorbol esters played an important role in the induction of differentiation in MOLT-3 cells by TPA.…”

“…A similar result is shown in Figure 2, where the baseline of PKC activity without TPA is also lower in the TPA-resistant subclone ROI than in the parental MOLT-3. These results may reflect a decrease in number of phorbol ester receptors in TPA-resistant subclones of MOLT-3, as already noted (Mayumi et al, 1988). Phorbol esters with tumour-promoting activity cause a translocation of PKC from the cytosol to the membrane fraction in various cell systems (Kraft et al, 1982;Kraft & Anderson, 1983;Shoji et al, 1987) including human mature T-ells (Isakov et al, 1987;Manger et al, 1987).…”

“…With respect to the phorbol ester receptors, there is also a difference between MOLT-3 and HL-60. The down regulation of phorbol ester receptors by TPA was seen both in TPA-resistant cells and in the parental MOLT-3 (Mayumi et al, 1988), whereas it was not observed in TPA-resistant cells from HL-60 (Solanki et al, 1981). The down regulation of phorbol ester receptors was observed within 15min after stimulation with TPA (Mayumi et al, 1988).…”

“…Using MOLT-3 and its subclones resistant to TPA induction, we also found that the receptors for phorbol ester play an important role at the initial process of induction of cell differentiation (Mayumi et al, 1988). Our main interest has been whether activation of PKC mediates the signals for differentiation as it does in the process of stimulation or proliferation in various cell systems (Kaibuchi et al, 1983;Kajikawa et al, 1983;Malaisse et al, 1983;Rozengurt et al, 1984), including human mature T-lymphocytes (Isakov et al, 1987;Manger et al, 1987).…”

“…Kraft et al (1982) and Kraft and Anderson (1983) demonstrated that TPA caused a translocation of PKC from the cytosol to the membrane in intact cells and these data were supported by other investigators (Shoji et al, 1987). Homma et al (1986) (ROI,R02,R03,R04 and R05) resistant to the growth inhibition effect by TPA were obtained from colonies formed in 0.8% methylcellulose containing 16nM TPA and 15% fetal calf serum (FCS), as described (Mayumi et al, 1988). These cells were maintained in RPMI 1640 medium supplemented with 10% FCS, 100mgl-1 streptomycin and 100Uml1-penicillin.…”