Modular Assembly of Allosteric MEK Inhibitor Structural Elements Unravels Potency and Feedback‐Modulation Handles

Having recently identified a so‐far unexplored area adjacent to the known binding site of allosteric mitogen‐activated protein kinase kinase (MEK) inhibitors, we now report an extension of these studies by combining our new side chains with different MEK inhibitor cores in a modular manner. Replacement of the amide headgroup with inverse sulfonamides resulted in the identification of new MEK inhibitors with at least 10‐fold higher cellular potency against K‐Ras‐mutated tumor cells. A selected inhibitor from this new series retained the favorable pharmacokinetic profile of its predecessor in rodent and non‐rodent species and displayed significant in vivo efficacy at once‐daily oral doses of 0.25–1 mg kg^?1 in a K‐Ras‐mutated xenograft model. The brain penetration potential of this analogue was significantly attenuated relative to PD325901. In a second series, the central fluorophenyl core was replaced by a pyridine moiety which gave rise to a similar boost in cellular potency. Most notably, analogues from this second series do not show MEK feedback phosphorylation in K‐Ras‐mutated A549 cells. Our results complement recent reports on the structural intricacies of MEK–Raf feedback interactions.     

The midbrain periaqueductal gray and fear extinction: Opioid receptor subtype and roles of cyclic AMP, protein kinase A, and mitogen-activated protein kinase.

Four experiments studied the opioid receptor subtype and signal transduction mechanisms mediating fear extinction in the ventrolateral quadrant of the midbrain periaqueductal gray (vlPAG). Microinjection of a μ- but not a δ- or κ-opioid receptor antagonist into the vlPAG retarded extinction. Extinction was also dose-dependently retarded by vlPAG infusions of a cyclic AMP (cAMP) analog but was unaffected by infusions of a protein kinase A activator or a mitogen-activated protein kinase inhibitor across wide dose ranges. The results show that fear extinction occurs via activation of vlPAG μ-opioid receptors and involves reductions in cAMP. These mechanisms are different from the cellular mechanisms for extinction in the amygdala and from the known cellular mechanisms for opioid analgesia in the vlPAG. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of the KIN2 gene product in Saccharomyces cerevisiae and comparison between the kinase activities of p145KIN1 and p145KIN2

We have isolated two yeast genes, KIN1 and KIN2, by their homology to the protein kinase family of viral oncogenes. Previous studies have identified the yeast KIN1 gene product (pp145^KIN1) as a 145 kilodalton (kDa) phosphoprotein with serine/threonine-specific protein kinase activity. To identify and biochemically characterize the KIN2 gene product, antibodies were raised against a bacterial β-galactosidase/KIN2 fusion polypeptide. In vivo, the KIN2 gene product is a 145 kDa phosphoprotein, pp145^KIN2. In immune complexes, pp145^KIN2 demonstrates serine/threonine protein kinase activity, transferring phosphate from [γ-³²P]ATP to either itself or the exogenously added substrates α-casein, acid-denatured enolase, or phosvitin. In vitro, kinase activity is dependent on either Mn²⁺ or Mg²⁺ ions. Both enzymes, pp145^KIN1 and pp145^KIN2, prefer ATP over GTP as their phosphoryl donor. Since a new class of yeast protein kinases has been identified which are serine/tyrosine-specific, we analysed a wide range of substrates to see if any could be phosphorylated by pp145^KIN1 or pp145^KIN2 on tyrosine residues. Both enzymes phosphorylate α-casein, acid-denatured enolase, and phosvitin on serine and threonine residues. Neither enzyme could phosphorylate tyrosine residues even though good substrates for tyrosine-specific kinases such as enolase, angiotensin II, and the synthetic polymer GLU⁸⁰TYR²⁰ were used. The biochemical analysis of KIN2 kinase activity shows remarkable similarity to that of its most closely related yeast kinase, KIN1. It remains to be seen if these two yeast protein kinases share any functional relationships or substrates in vivo.     

Emerging Importance of Tyrosine Kinase Inhibitors against Cancer: Quo Vadis to Cure?

GLOBOCAN 2020 estimated more than 19.3 million new cases, and about 10 million patients were deceased from cancer in 2020. Clinical manifestations showed that several growth factor receptors consisting of transmembrane and cytoplasmic tyrosine kinase (TK) domains play a vital role in cancer progression. Receptor tyrosine kinases (RTKs) are crucial intermediaries of the several cellular pathways and carcinogenesis that directly affect the prognosis and survival of higher tumor grade patients. Tyrosine kinase inhibitors (TKIs) are efficacious drugs for targeted therapy of various cancers. Therefore, RTKs have become a promising therapeutic target to cure cancer. A recent report shows that TKIs are vital mediators of signal transduction and cancer cell proliferation, angiogenesis, and apoptosis. In this review, we discuss the structure and function of RTKs to explore their prime role in cancer therapy. Various TKIs have been developed to date that contribute a lot to treating several types of cancer. These TKI based anticancer drug molecules are also discussed in detail, incorporating their therapeutic efficacy, mechanism of action, and side effects. Additionally, this article focuses on TKIs which are running in the clinical trial and pre-clinical studies. Further, to gain insight into the pathophysiological mechanism of TKIs, we also reviewed the impact of RTK resistance on TKI clinical drugs along with their mechanistic acquired resistance in different cancer types.     

A Dual Anti-Inflammatory and Anti-Proliferative 3-Styrylchromone Derivative Synergistically Enhances the Anti-Cancer Effects of DNA-Damaging Agents on Colon Cancer Cells by Targeting HMGB1-RAGE-ERK1/2 Signaling

The current anti-cancer treatments are not enough to eradicate tumors, and therefore, new modalities and strategies are still needed. Most tumors generate an inflammatory tumor microenvironment (TME) and maintain the niche for their development. Because of the critical role of inflammation via high-mobility group box 1 (HMGB1)–receptor for advanced glycation end-products (RAGE) signaling pathway in the TME, a novel compound possessing both anti-cancer and anti-inflammatory activities by suppressing the HMGB1-RAGE axis provides an effective strategy for cancer treatment. A recent work of our group found that some anti-cancer 3-styrylchromones have weak anti-inflammatory activities via the suppression of this axis. In this direction, we searched such anti-cancer molecules possessing potent anti-inflammatory activities and discovered 7-methoxy-3-hydroxy-styrylchromone (C6) having dual suppressive activities. Mechanism-of-action studies revealed that C6 inhibited the increased phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) under the stimulation of HMGB1-RAGE signaling and thereby suppressed cytokine production in macrophage-like RAW264.7 cells. On the other hand, in colorectal cancer HCT116 cells, C6 inhibited the activation of ERK1/2, cyclin-dependent kinase 1, and AKT, down-regulated the protein level of XIAP, and up-regulated pro-apoptotic Bax and caspase-3/7 expression. These alterations are suggested to be involved in the C6-induced suppression of cell cycle/proliferation and initiation of apoptosis in the cancer cells. More importantly, in cancer cells, the treatment of C6 potentiates the anti-cancer effects of DNA-damaging agents. Thus, C6 may be a promising lead for the generation of a novel class of cancer therapeutics.     

Diabetic vascular dysfunction: links to glucose-induced reductive stress and VEGF

A complete biochemical understanding of the mechanisms by which hyperglycemia causes vascular functional and structural changes associated with the diabetic milieu still eludes us. In recent years, the numerous biochemical and metabolic pathways postulated to have a causal role in the pathogenesis of diabetic vascular disease have been distilled into several unifying hypotheses. These involve either increased reductive or oxidative stress to the cell, or the activation of numerous protein kinase pathways, particularly protein kinase C and mitogen-activated protein kinases. As detailed below, there is tremendous crosstalk between these competing hypotheses. We propose that increased tissue glucose levels alter cytosolic coenzyme balance by increased flux of glucose through the sorbitol pathway increasing free cytosolic NADH levels. Increased NADH levels can generate reactive oxygen species via numerous mechanisms, lead to the formation of intracellular advanced glycation end products, and induce growth factor expression via mechanisms involving protein kinase C activation. The elevation in growth factors, particularly vascular endothelial growth factor (VEGF), is responsible for the vascular dysfunction via numerous mechanisms reported here in detail.     

Place Preference Induced by Nucleus Accumbens Amphetamine Is Impaired by Antagonists of ERK or p38 MAP Kinases in Rats.

The nucleus accumbens (NAc) plays a role in conditioned place preference (CPP). The authors tested the hypothesis that inhibition of mitogen-activated protein kinases (MAPKs) would inhibit NAc-amphetamine-produced CPP. Results confirmed that NAc amphetamine increased levels of the MAPK extracellular signal-regulated kinase (ERK). In CPP studies, NAc injections (0.5 μl per side) of the ERK inhibitor PD98059 (1.0-2.5 μg) or the p38 kinase inhibitor SB203580 (15-500 ng) dose dependently impaired CPP. The c-Jun-N-terminal kinase (JNK) inhibitor SP600125 (1.0-2.5 μg) failed to block the CPP effect. The drugs did not block amphetamine-induced motor activity. Results suggest that ERK and p38, but not JNK, MAPKs may be necessary for the establishment of NAc amphetamine-produced CPP and may also mediate other forms of reward-related learning dependent on NAc. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rare peptide segments are found significantly more often in proto-oncoproteins than control proteins: implications for immunology and oncology

There is some evidence to suggest that peptide segments that are found rarely or never in the host proteome play a role in the immune response to disease-related proteins, both those derived from microbes and those derived from the host itself. We conjecture that this pattern may extend to human proto-oncoproteins. Our hypothesis in this study is that the frequency of rare peptide segments in sets of human proto-oncoproteins is significantly higher than in sets of control proteins, and we show that this is the case. Possible immunological implications of this observation are discussed.