AG 494

AG 494 is a potent and selective inhibitor of EGFR with IC50 value of 0.7 μM.

The epidermal growth factor receptor (EGFR) is the cell-surface receptor for epidermal growth factor and plays an important role in tumor invasion and cancer cell proliferation.

AG 494 is a potent and selective EGFR inhibitor. AG 494 inhibited autophosphorylation of EGFR and HER-2 with IC50 values of 1.1 and 39 μM, respectively. In DHER-14 cells, AG 494 inhibited Cdk2 activation and EGF-dependent DNA synthesis [1]. AG494 arrested cells at late G1 and S phase and inhibited the activation of Cdk2 by phosphorylating tyrosine 15 on Cdk2 [2]. Epidermal growth factor (EGF) increased (bone morphogenetic protein) BMP9-induced osteogenic markers of mesenchymal stem cells (MSCs), which was inhibited by AG-494 in a time- and dose-dependent way [3]. In human prostate (DU145) and lung (A549) cancer cell lines, AG494 reversibly and significantly inhibited autocrine growth in a dose-dependent way. Also, AG494 induced cell apoptosis in both cell lines and arrested cell growth in the G1 phase [4].

References:
[1].  Osherov N, Levitzki A. Tyrphostin AG 494 blocks Cdk2 activation. FEBS Lett, 1997, 410(2-3): 187-190.
[2].  Kleinberger-Doron N, Shelah N, Capone R, et al. Inhibition of Cdk2 activation by selected tyrphostins causes cell cycle arrest at late G1 and S phase. Exp Cell Res, 1998, 241(2): 340-351.
[3].  Liu X, Qin J, Luo Q, et al. Cross-talk between EGF and BMP9 signalling pathways regulates the osteogenic differentiation of mesenchymal stem cells. J Cell Mol Med, 2013, 17(9): 1160-1172.
[4].  Bojko A1, Reichert K, Adamczyk A, et al. The effect of tyrphostins AG494 and AG1478 on the autocrine growth regulation of A549 and DU145 cells. Folia Histochem Cytobiol, 2012, 50(2): 186-195.

Tyrphostin AG 494 blocks Cdk2 activation.[Pubmed:9237626]

FEBS Lett. 1997 Jun 30;410(2-3):187-90.

We have previously shown that the EGFR kinase selective tyrphostin AG 494 fails to inhibit EGFR kinase in intact cells. Yet, AG 494 proved to inhibit EGF- or serum-induced cell proliferation (Osherov et al., J. Biol. Chem. 268 (1993) 11134-11142). In this preliminary communication we show that AG 494 as well as its close analogs AG 490 and AG 555 block Cdk2 activation. In contrast, AG 1478, a more selective EGFR kinase blocker which is also active as EGFR kinase blocker in intact cells, fails to do so. AG 494 exerts its full inhibitory activity on Cdk2 activation even when added 20 h subsequent to EGF addition when Cdk2 activation is maximal. The inhibitory activity on Cdk2 activation parallels its DNA synthesis inhibitory activity, strongly suggesting that its target is one of the molecular mechanisms involved in Cdk2 activation. AG 494 and its analogs may become useful lead compounds for the development of drugs aimed at the cell cycle machinery.

Cross-talk between the calcium-sensing receptor and the epidermal growth factor receptor in Rat-1 fibroblasts.[Pubmed:15950968]

Exp Cell Res. 2005 Aug 15;308(2):439-45.

The calcium-sensing receptor (CaR) is a G-protein-coupled receptor that is activated by extracellular calcium (Cao2+). Rat-1 fibroblasts have been shown to proliferate and increase ERK activity in response to elevation of [Ca2+]o, and these responses are dependent on functional CaR expression. In this report, we examined the role of cross-talk between the CaR and the epidermal growth factor receptor (EGFR) in mediating these responses in Rat-1 cells. This report shows that AG1478, a specific inhibitor of the EGFR kinase, significantly inhibits the increase in proliferation induced by elevated Cao2+. Furthermore, we show that AG1478 acts downstream or separately from G protein subunit activation of phospholipase C. AG1478 significantly inhibits Cao2+-stimulated ERK phosphorylation and in vitro kinase activity. A similar inhibition of ERK phosphorylation was observed in response to the inhibitor AG494. In addition, treatment with inhibitors of metalloproteases involved in shedding of membrane anchored EGF family ligands substantially inhibited the increase in ERK activation in response to elevated Cao2+. This is consistent with the known expression of TGFalpha by Rat-1 cells. These results indicate that EGFR transactivation is an important component of the CaR-mediated response to increased Cao2+ in Rat-1 fibroblasts and most likely involves CaR-mediated induction of regulated proteolysis and ligand shedding.

Tyrphostins that suppress the growth of human papilloma virus 16-immortalized human keratinocytes.[Pubmed:10454524]

J Pharmacol Exp Ther. 1999 Sep;290(3):1442-57.

Human papilloma virus 16 (HPV16) is considered to be the causative agent for cervical cancer, which ranks second to breast cancer in women's malignancies. In an attempt to develop drugs that inhibit the malignant transformation of HPV16-immortalized epithelial cells, we examined the effect of tyrphostins on such cells. We examined the effect of tyrphostins from four different families on the growth of HPV16-immortalized human keratinocytes (HF-1) cells. We found that they alter their cell cycle distribution, their morphology, and induce cell death by apoptosis. The effects of tyrphostins on HF-1 cells are different from their effects on normal keratinocytes. Growth suppression by AG555 and AG1478 is accompanied by 30% apoptosis in HF-1 cells, but this is not observed in normal keratinocytes. Tyrphostin treatment produces distinctive morphological changes in HF-1 cells and in normal keratinocytes; however, the culture organization of normal keratinocytes is less disrupted. These differential effects of the tyrphostins on HPV16-immortalized keratinocytes compared with their effects on normal keratinocytes suggests that these compounds are suitable candidates for the treatment of papilloma. Previous and present results indicate that group 1 tyrphostins, which inhibit Cdk2 activation, and group 2 tyrphostins, represented by AG1478, a potent epidermal growth factor receptor kinase inhibitor, induce cell cycle arrest; and, in the case of HF-1 cells, apoptosis and differentiation. Cells accumulate in the G(1) phase of the cell cycle at the expense of S and G(2) + M. These compounds block the growth of normal keratinocytes without inducing apoptosis or differentiation, causing them to accumulate in G(1). AG17, which belongs to group 4, exerts its antiproliferative effect mainly by increasing the fractions of cells in G(1) with a concomitant decrease in the fraction of cells in S and G(2) + M.

Tyrphostins. 2. Heterocyclic and alpha-substituted benzylidenemalononitrile tyrphostins as potent inhibitors of EGF receptor and ErbB2/neu tyrosine kinases.[Pubmed:1676428]

J Med Chem. 1991 Jun;34(6):1896-907.

We have previously described a novel series of low molecular weight protein tyrosine kinase inhibitors which we named tyrphostins. The characteristic active pharmacophore of these compounds was the hydroxy-cis-benzylidenemalononitrile moiety. In this article we describe three novel groups of tyrphostins: (i) one group has the phenolic moiety of the cis-benzylidenemalononitrile replaced either with other substituted benzenes or with heteroaromatic rings, (ii) another is a series of conformationally constrained derivatives of hydroxy-cis-benzylidenemalononitriles in which the malononitrile moiety is fixed relative to the aromatic ring, and (iii) two groups of compounds in which the position trans to the benzenemalononitrile has been substituted by ketones and amides. Among the novel tyrphostins examined we found inhibitors which discriminate between the highly homologous EGF receptor kinase (HER1) and ErbB2/neu kinase (HER2). These findings may lead to selective tyrosine kinase blockers for the treatment of diseases in which ErbB2/neu is involved.