When epidermal growth factor and its relatives bind the ErbB family of receptors, they trigger a rich network of signalling pathways, culminating in responses ranging from cell division to death, motility to adhesion. The network is often dysregulated in cancer and lends credence to the mantra that molecular understanding yields clinical benefit: over 25,000 women with breast cancer have now been treated with trastuzumab (Herceptin), a recombinant antibody designed to block the receptor ErbB2. Likewise, small-molecule enzyme inhibitors and monoclonal antibodies to ErbB1 are in advanced phases of clinical testing. What can this pathway teach us about translating basic science into clinical use?

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Untangling the ErbB signalling network

The specificities of 28 commercially available compounds reported to be relatively selective inhibitors of particular serine/threonine-specific protein kinases have been examined against a large panel of protein kinases. The compounds KT 5720, Rottlerin and quercetin were found to inhibit many protein kinases, sometimes much more potently than their presumed targets, and conclusions drawn from their use in cell-based experiments are likely to be erroneous. Ro 318220 and related bisindoylmaleimides, as well as H89, HA1077 and Y 27632, were more selective inhibitors, but still inhibited two or more protein kinases with similar potency. LY 294002 was found to inhibit casein kinase-2 with similar potency to phosphoinositide (phosphatidylinositol) 3-kinase. The compounds with the most impressive selectivity profiles were KN62, PD 98059, U0126, PD 184352, rapamycin, wortmannin, SB 203580 and SB 202190. U0126 and PD 184352, like PD 98059, were found to block the mitogen-activated protein kinase (MAPK) cascade in cell-based assays by preventing the activation of MAPK kinase (MKK1), and not by inhibiting MKK1 activity directly. Apart from rapamycin and PD 184352, even the most selective inhibitors affected at least one additional protein kinase. Our results demonstrate that the specificities of protein kinase inhibitors cannot be assessed simply by studying their effect on kinases that are closely related in primary structure. We propose guidelines for the use of protein kinase inhibitors in cell-based assays.

/pdf/specificity-and-mechanism-of-action-of-some-commonly-used-2r15uc4rwj.pdf

Specificity and mechanism of action of some commonly used protein kinase inhibitors

Mitogen-activated protein (MAP) kinases comprise a family of ubiquitous proline-directed, protein-serine/threonine kinases, which participate in signal transduction pathways that control intracellular events including acute responses to hormones and major developmental changes in organisms. MAP kinases lie in protein kinase cascades. This review discusses the regulation and functions of mammalian MAP kinases. Nonenzymatic mechanisms that impact MAP kinase functions and findings from gene disruption studies are highlighted. Particular emphasis is on ERK1/2.

/pdf/mitogen-activated-protein-map-kinase-pathways-regulation-and-3nsauvepr2.pdf

Mitogen-activated protein (MAP) kinase pathways: regulation and physiological functions.

PD 098059 Is a Specific Inhibitor of the Activation of Mitogen-activated Protein Kinase Kinase in Vitro and in Vivo

Functional expression cloning of nanog, a pluripotency sustaining factor in embryonic stem cells

Treatment of cells with a variety of growth factors triggers a phosphorylation cascade that leads to activation of mitogen-activated protein kinases (MAPKs, also called extracellular signal-regulated kinases, or ERKs). We have identified a synthetic inhibitor of the MAPK pathway. PD 098059 [2-(2'-amino-3'-methoxyphenyl)-oxanaphthalen-4-one] selectively inhibited the MAPK-activating enzyme, MAPK/ERK kinase (MEK), without significant inhibitory activity of MAPK itself. Inhibition of MEK by PD 098059 prevented activation of MAPK and subsequent phosphorylation of MAPK substrates both in vitro and in intact cells. Moreover, PD 098059 inhibited stimulation of cell growth and reversed the phenotype of ras-transformed BALB 3T3 mouse fibroblasts and rat kidney cells. These results indicate that the MAPK pathway is essential for growth and maintenance of the ras-transformed phenotype. Further, PD 098059 is an invaluable tool that will help elucidate the role of the MAPK cascade in a variety of biological settings.

https://www.pnas.org/content/pnas/92/17/7686.full.pdf

A synthetic inhibitor of the mitogen-activated protein kinase cascade.

The mitogen-activated protein kinase pathway is thought to be essential in cellular growth and differentiation. Here we report the discovery of a highly potent and selective inhibitor of the upstream kinase MEK that is orally active. Tumor growth was inhibited as much as 80% in mice with colon carcinomas of both mouse and human origin after treatment with this inhibitor. Efficacy was achieved with a wide range of doses with no signs of toxicity, and correlated with a reduction in the levels of activated mitogen-activated protein kinase in excised tumors. These data indicate that MEK inhibitors represent a promising, noncytotoxic approach to the clinical management of colon cancer.

Blockade of the MAP kinase pathway suppresses growth of colon tumors in vivo.

A small molecule called PD 153035 inhibited the epidermal growth factor (EGF) receptor tyrosine kinase with a 5-pM inhibition constant. The inhibitor was specific for the EGF receptor tyrosine kinase and inhibited other purified tyrosine kinases only at micromolar or higher concentrations. PD 153035 rapidly suppressed autophosphorylation of the EGF receptor at low nanomolar concentrations in fibroblasts or in human epidermoid carcinoma cells and selectively blocked EGF-mediated cellular processes including mitogenesis, early gene expression, and oncogenic transformation. PD 153035 demonstrates an increase in potency over that of other tyrosine kinase inhibitors of four to five orders of magnitude for inhibition of isolated EGF receptor tyrosine kinase and three to four orders of magnitude for inhibition of cellular phosphorylation.

https://science.sciencemag.org/content/sci/265/5175/1093.full.pdf

A specific inhibitor of the epidermal growth factor receptor tyrosine kinase

Epidermal growth-factor inhibitors of formula (I), wherein: 1) Y and Z are both C (carbon), both N or one N and the other C, in which case the ring structure is a linearly fused 6,6 (5 or 6) tricycle, or 2) one of Y and Z is C=C, C=N, whereupon the other one of Y or Z is simply a bond between the two aromatic rings, then the ring structure is a nonlinear 6,6 (5 or 6) tricycle, or 3) one of Y and Z is N, O or S, whereupon the other one of Y or Z is simply a bond between the two aromatic rings, then the ring structure is a fused 6,5 (5 or 6) tricycle; A, B, D and E can all be carbon, or up to two of them can be nitrogen, whereupon the remaining atoms must be carbon, or any two contiguous positions in A-E can be a single heteroatom, N, O or S, forming a five membered fused ring, in which case one of the two remaining atoms must be carbon, and the other can be either carbon or nitrogen. X = O, S, NH or NR9, such that R9 = lower alkyl, OH, NH?2?, lower alkoxy or lower monoalkylamino m = 0-3, and Ar is phenyl, thienyl, furanyl, pyrrolyl, pyridyl, pyrimidyl, imidazolyl, pyrazinyl, oxazolyl, thiazolyl, naphthyl, benzothienyl, benzofuranyl, indolyl, quinolinyl, isoquinolinyl and quinazolinyl.

Bicyclic compounds capable of inhibiting tyrosine kinases of the epidermal growth factor receptor family

The present invention provides compounds that are irreversible inhibitors of tyrosine kinases. Also provided is a method of treating cancer, restenosis, atherosclerosis, endometriosis, and psoriasis and a pharmaceutical composition that comprises a compound that is an irreversible inhibitor of tyrosine kinases.

Alexander James Bridges

Papers

A synthetic inhibitor of the mitogen-activated protein kinase cascade.

Blockade of the MAP kinase pathway suppresses growth of colon tumors in vivo.

A specific inhibitor of the epidermal growth factor receptor tyrosine kinase

Bicyclic compounds capable of inhibiting tyrosine kinases of the epidermal growth factor receptor family

Irreversible inhibitors of tyrosine kinases