Insulin dependence of murine lymphoid T‐cell leukemia

Abstract

The in vitro proliferation of the spontaneous lymphoid T-cell leukemia designated LB was enhanced by physiological, intermediate and supraphysiological concentrations of insulin. The enhancing effect was observed in both serum-free medium (SFM) and medium containing low concentrations of serum. Guinea-pig anti-insulin serum, but not guinea-pig normal serum, inhibited the proliferation of LB cells incubated either in medium containing serum alone or in medium containing serum and supplemented with insulin. This finding suggests that LB cells use serum insulin as a growth factor. Insulin-like growth factors I (IGF-I) and II (IGF-II) failed to stimulate an appreciable proliferation in LB cells, whereas in the same experiment insulin markedly enhanced the proliferation of this lymphoid leukemia. Furthermore, the concentration of unlabelled insulin required to displace 50% of 125I-insulin bound to LB cells was 3 orders of magnitude lower than the concentration of IGF-I required to achieve the same displacement. Our findings indicate that interaction of insulin with its own receptor, and not with IGF-I receptor, triggers the proliferation of LB cells. Radio-receptor assays revealed that LB cells express approximately 3,200 molecules of high affinity (Kd = 10(-9) M) insulin receptor per cell. None of 7 other tumor cell lines tested responded to insulin. The proliferation of insulin-stimulated LB cells was also inhibited with tyrphostin, a tyrosine kinase blocker analogous to tyrosine, which perhaps blocks the tyrosine kinase activity of the insulin receptor beta-chain.

Mitogenic properties of insulin and insulin analogues mediated by the insulin receptor

“…The cell proliferation was blocked by anti-insulin antibodies. In a previous characterization, the cells were shown to bind 125 I-insulin and to contain around 3200 high affinity insulin binding sites [28]. Furthermore, insulin deficiency generated by a low energy diet or streptozotocin-induced insulin-dependent diabetes produced resistance to lymphoma growth in mice [29], demonstrating insulin dependence in vivo.…”

“…This very invasive tumour [25], initially qualified as a lymphoid T-cell leukemia, arose spontaneously in a 6-month-old BALB/c mouse in the animal colony of the Academia Nacional de Medicina in Buenos Aires [26,27]. It was noticed that the cells grew much better in medium containing insulin than in medium lacking it [28]. Thymidine incorporation into LB cells (as well as cell number) was markedly stimulated over a wide range of insulin concentrations (including low physiological), but produced only a negligible response to IGF-I and none to IGF-II [28].…”

“…It was noticed that the cells grew much better in medium containing insulin than in medium lacking it [28]. Thymidine incorporation into LB cells (as well as cell number) was markedly stimulated over a wide range of insulin concentrations (including low physiological), but produced only a negligible response to IGF-I and none to IGF-II [28]. The cell proliferation was blocked by anti-insulin antibodies.…”

Insulin receptor and cancer

“…The most studied of these analogs, AspB10, was shown to enhance cell proliferation (Ish-Shalom et al 1997, De Meyts & Shymko 2000 and development of mammary tumors in mice (Drejer 1992). Further evidence that insulin induces growth and other biological effects through the IR have been obtained in various neoplastic cells, which express IRs but non-functional IGF1R levels, such as human myosarcoma cells SKUT1 , colon cancer cells (LoVo; Jones et al 2006), and murine T-cell lymphoma cell line (LB cells; Pillemer et al 1992, Sharon et al 1993.…”

Logical analysis of timing-dependent receptor signalling specificity: application to the insulin receptor metabolic and mitogenic signalling pathways

“…Although the predominant signalling mode of the insulin receptor is for metabolic function, there are examples of cell lines with modified specificity of insulin receptor signalling. The growth of the LB strain of T-cell lymphoma cells is strongly stimulated by insulin, and since these cells lack insulin-like growth factor I receptors [19], mitogenic signalling is presumed to occur via the insulin receptor [19,20]. These cells evidently have an insulin receptor signalling pathway which is biased toward mitogenic activation, implying that a site of selectivity for metabolic versus mitogenic signalling exists somewhere in the chain of signalling events, and that the LB cells may possess a mutation or mutations that are responsible for this altered selectivity.…”