Signal transduction through substance P receptor in human glioblastoma cells: roles for Src and PKCdelta

Radiotherapy Plus the Neurokinin-1 Receptor Antagonist Aprepitant: A Potent Therapeutic Strategy for the Treatment of Diffuse Intrinsic Pontine Glioma

Background: Diffuse intrinsic pontine glioma (DIPG) is a devastating childhood brainstem tumor. The median survival of DIPG is 16-24 months independent of the treatment received. Therefore, new therapeutic strategies against DIPG are urgently needed. Substance P (SP) peptide, through the neurokinin neurokinin-1 receptor (NK-1R), is involved in glioma progression. It induces glioma cell proliferation by activating MAPKs (p38 MAPK, ERK1/2, and JNK), c-Myc, AP-1, and NF-κB and induces antiapoptotic effects via PI3K/Akt/mTOR in glioma cells. SP favors glycogen breakdown that is essential for glycolysis. The SP/NK-1R system also regulates the migration and invasion of glioma cells, stimulates angiogenesis, and triggers inflammation which contributes to glioma progression. Moreover, all glioma cells express NK-1R, and NK-1R is essential for the viability of glioma cells and not of normal cells. In contrast, in glioma, NK-1R antagonists, such as the drug aprepitant, penetrate the brain and reach therapeutic concentrations, thereby inhibiting mitogenesis, inducing apoptosis, and inhibiting the breakdown of glycogen in glioma cells. In addition, they inhibit angiogenesis and exert antimetastatic and anti-inflammatory effects. The combination of radiotherapy with NK-1R antagonists produces radiosensitization and radioneuroprotection, reduces both peritumoral- and radiation-induced inflammation, and also provides antinausea and antivomiting effects. Objective: This review updates the involvement of the SP/NK-1R system in glioma promotion and progression and the potential clinical application of NK-1R antagonist drugs in DIPG therapy. Conclusions: NK-1R plays a crucial role in glioma progression and NK-1R antagonists such as aprepitant could be used in combination with radiotherapy as a potent therapeutic strategy for the treatment of patients with DIPG.

Association of Neurokinin-1 Receptor Signaling Pathways with Cancer

BACKGROUND

Numerous biochemical reactions leading to altered cell proliferation cause tumorigenesis and cancer treatment resistance. The mechanisms implicated include genetic and epigenetic changes, modified intracellular signaling, and failure of control mechanisms caused by intrinsic and extrinsic factors alone or combined. No unique biochemical events are responsible; entangled molecular reactions conduct the resident cells in a tissue to display uncontrolled growth and abnormal migration. Copious experimental research supports the etiological responsibility of NK-1R (neurokinin-1 receptor) activation, alone or cooperating with other mechanisms, in cancer appearance in different tissues. Consequently, a profound study of this receptor system in the context of malignant processes is essential to design new treatments targeting NK-1R-deviated activity.

METHODS

This study reviews and discusses recent literature that analyzes the main signaling pathways influenced by the activation of neurokinin 1 full and truncated receptor variants. Also, the involvement of NK-1R in cancer development is discussed.

CONCLUSION

NK-1R can signal through numerous pathways and cross-talk with other receptor systems. The participation of override or malfunctioning NK-1R in malignant processes needs a more precise definition in different types of cancers to apply satisfactory and effective treatments. A long way has already been traveled: the current disposal of selective and effective NK-1R antagonists and the capacity to develop new drugs with biased agonistic properties based on the receptor's structural states with functional significance opens immediate research action and clinical application.

Neurokinin-1 receptor promotes non-small cell lung cancer progression through transactivation of EGFR

Despite the great advances in target therapy, lung cancer remains the top cause of cancer-related death worldwide. G protein-coupled receptor neurokinin-1 (NK1R) is shown to play multiple roles in various cancers; however, the pathological roles and clinical implication in lung cancer are unclarified. Here we identified NK1R as a significantly upregulated GPCR in the transcriptome and tissue array of human lung cancer samples, associated with advanced clinical stages and poor prognosis. Notably, NK1R is co-expressed with epidermal growth factor receptor (EGFR) in NSCLC patients' tissues and co-localized in the tumor cells. NK1R can crosstalk with EGFR by interacting with EGFR, transactivating EGFR phosphorylation and regulating the intracellular signaling of ERK1/2 and Akt. Activation of NK1R promotes the proliferation, colony formation, EMT, MMP2/14 expression, and migration of lung cancer cells. The inhibition of NK1R by selective antagonist aprepitant repressed cell proliferation and migration in vitro. Knockdown of NK1R significantly slowed down the tumor growth in nude mice. The sensitivity of lung cancer cells to gefitinib/osimertinib is highly increased in the presence of the selective NK1R antagonist aprepitant. Our data suggest that NK1R plays an important role in lung cancer development through EGFR signaling and the crosstalk between NK1R and EGFR may provide a potential therapeutic target for lung cancer treatment.

Yokukansan, a Japanese Herbal Medicine, Suppresses Substance PInduced Production of Interleukin-6 and Interleukin-8 by Human U373 MG Glioblastoma Astrocytoma Cells

BACKGROUND

Yokukansan is a traditional Japanese herbal medicine that has an antiallodynic effect in patients with chronic pain. However, the mechanisms by which yokukansan inhibits neuropathic pain are unclear.

OBJECTIVE

This study aimed to investigate the molecular effects of yokukansan on neuroinflammation in U373 MG glioblastoma astrocytoma cells, which express a functional high-affinity neurokinin 1 receptor (substance P receptor), and produce interleukin (IL)-6 and IL-8 in response to stimulation by substance P (SP).

METHODS

We assessed the effect of yokukansan on the expression of ERK1/2, P38 MAPK, nuclear factor (NF)-κB, and cyclooxygenase-2 (COX-2) in U373 cells by western blot assay. Levels of IL-6 and IL-8 in conditioned medium obtained after stimulation of cells with SP for 24 h were measured by enzyme-linked immunosorbent assay. All experiments were conducted in triplicate. Results were analyzed by one-way ANOVA, and significance was accepted at p < 0.05.

RESULTS

Yokukansan suppressed SP-induced production of IL-6 and IL-8 by U373 MG cells, and downregulated SP-induced COX-2 expression. Yokukansan also inhibited phosphorylation of ERK1/2 and p38 MAPK, as well as nuclear translocation of NF-κB, induced by SP stimulation of U373 MG cells.

CONCLUSION

Yokukansan exhibits anti-inflammatory activity by suppressing SP-induced production of IL-6 and IL-8 and downregulating COX-2 expression in U373 MG cells, possibly via inhibition of the activation of signaling molecules, such as ERK1/2, p38 MAPK, and NF-κB.

The Neurokinin-1 Receptor Antagonist Aprepitant, a New Drug for the Treatment of Hematological Malignancies: Focus on Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a heterogeneous hematological malignancy. To treat the disease successfully, new therapeutic strategies are urgently needed. One of these strategies can be the use of neurokinin-1 receptor (NK-1R) antagonists (e.g., aprepitant), because the substance P (SP)/NK-1R system is involved in cancer progression, including AML. AML patients show an up-regulation of the NK-1R mRNA expression; human AML cell lines show immunoreactivity for both SP and the NK-1R (it is overexpressed: the truncated isoform is more expressed than the full-length form) and, via this receptor, SP and NK-1R antagonists (aprepitant, in a concentration-dependent manner) respectively exert a proliferative action or an antileukemic effect (apoptotic mechanisms are triggered by promoting oxidative stress via mitochondrial Ca⁺⁺ overload). Aprepitant inhibits the formation of AML cell colonies and, in combination with chemotherapeutic drugs, is more effective in inducing cytotoxic effects and AML cell growth blockade. NK-1R antagonists also exert an antinociceptive effect in myeloid leukemia-induced bone pain. The antitumor effect of aprepitant is diminished when the NF-κB pathway is overactivated and the damage induced by aprepitant in cancer cells is higher than that exerted in non-cancer cells. Thus, the SP/NK-1R system is involved in AML, and aprepitant is a promising antitumor strategy against this hematological malignancy. In this review, the involvement of this system in solid and non-solid tumors (in particular in AML) is updated and the use of aprepitant as an anti-leukemic strategy for the treatment of AML is also mentioned (a dose of aprepitant (>20 mg/kg/day) for a period of time according to the response to treatment is suggested). Aprepitant is currently used in clinical practice as an anti-nausea medication.

Glioma and Neurokinin-1 Receptor Antagonists: A New Therapeutic Approach

BACKGROUND

In adults, the most lethal and frequent primary brain tumor is glioblastoma. Despite multimodal aggressive therapies, the median survival time after diagnosis is around 15 months. In part, this is due to the blood-brain barrier that restricts common treatments (e.g., chemotherapy). Unfortunately, glioma recurs in 90% of patients. New therapeutic strategies against glioma are urgently required. Substance P (SP), through the neurokinin (NK)-1 receptor, controls cancer cell proliferation by activating c-myc, mitogenactivated protein kinases, activator protein 1 and extracellular signal-regulated kinases 1 and 2. Glioma cells overexpress NK-1 receptors when compared with normal cells. The NK-1 receptor/SP system regulates the proliferation/migration of glioma cells and stimulates angiogenesis, triggering inflammation which contributes to glioma progression. In glioma cells, SP favors glycogen breakdown, essential for glycolysis. By contrast, in glioma, NK-1 receptor antagonists block the proliferation of tumor cells and the breakdown of glycogen and also promote the death (apoptosis) of these cells. These antagonists also inhibit angiogenesis and exert antimetastatic and anti-inflammatory actions.

OBJECTIVE

This review updates the involvement of the NK-1 receptor/SP system in the development of glioma and the potential clinical application of NK-1 receptor antagonists as antiglioma agents.

CONCLUSION

The NK-1 receptor plays a crucial role in glioma and NK-1 receptor antagonists could be used as anti-glioma drugs.

The emerging role of substance P/neurokinin-1 receptor signaling pathways in growth and development of tumor cells

Tachykinins (TKs) include an evolutionarily conserved group of small bio-active peptides which possess a common carboxyl-terminal sequence, Phe-X-Gly-Leu-Met-NH2. TKs also have been shown to have implications in different steps of carcinogenesis, such as angiogenesis, mitogenesis, metastasis, and other growth-related events. The biological actions of substance P (SP), as the most important member of the TK family, are mainly mediated through a G protein-coupled receptor named neurokinin-1 receptor (NK1R). More recently, it has become clear that SP/NK1R system is involved in the initiation and activation of signaling pathways involved in cancer development and progression. Therefore, SP may contribute to triggering a variety of effector mechanisms including protein synthesis and a number of transcription factors that modulate the expression of genes involved in these processes. The overwhelming insights into the blockage of NK1R using specific antagonists could suggest a therapeutic approach in cancer therapy. In this review, we focus on evidence supporting an association between the signaling pathways of the SP/NK1R system and cancer cell proliferation and development.

Design, synthesis and biological studies of a library of NK1-Receptor Ligands Based on a 5-arylthiosubstituted 2-amino-4,6-diaryl-3-cyano-4H-pyran core: Switch from antagonist to agonist effect by chemical modification

A library of 5-arylthiosubstituted 2-amino-4,6-diaryl-3-cyano-4H-pyrans has been synthesized as a new family of non-peptide NK1 receptor ligands by a one-pot cascade process. Their biological effects via interaction with the NK1 receptor were experimentally determined as percentage of inhibition (for antagonists) and percentage of activation (for agonists), compared to the substance P (SP) effect, in IPone assay. A set of these amino compounds was found to inhibit the action of SP, and therefore can be considered as a new family of SP-antagonists. Interestingly, the acylation of the 2-amino position causes a switch from antagonist to agonist activity. The 5-phenylsulfonyl-2-amino derivative 17 showed the highest antagonist activity, while the 5-p-tolylsulfenyl-2-trifluoroacetamide derivative 20R showed the highest agonist effect. As expected, in the case of the 5-sulfinylderivatives, there was an enantiomeric discrimination in favor of one of the two enantiomers, specifically those with (S_S,R_C) configuration. The anticancer activity studies assessed by using human A-549 lung cancer cells and MRC-5 non-malignant lung fibroblasts, revealed a statistically significant selective cytotoxic effect of some of these 2-amino-4H-pyran derivatives toward the lung cancer cells. These studies demonstrated that the newly synthesized 4H-pyran derivatives can be used as a starting point for the synthesis of novel SP-antagonists with higher anticancer activity in the future.

RNAi Based Approaches to the Treatment of Malignant Glioma

RNA interference (RNAi) is a recently discovered, powerful molecular mechanism that can be harnessed to engineer gene-specific silencing in mammalian tissues. A mechanism, where short double-stranded RNA (dsRNA) molecules, when introduced into cells elicit specific “knock-down” of gene expression via degradation of targeted messenger RNA, has lately become the technique of choice for analysis of gene function in oncology research. Thus, RNAi is currently being extensively evaluated as a potential therapeutic strategy against malignant gliomas, since surgical, radiological, and chemotherapeutic interventions during the past few decades have done little to improve the poor prognosis rate for patients with these dreaded tumors. This review summarizes the pre-clinical studies that are currently underway to test the validity of RNAi as a potential therapeutic strategy against malignant gliomas, and discusses the potential technical Hurdles that remain to be overcome before the technique can become a promising clinical therapy to combat this frequently lethal disease.

GW5074 and PP2 kinase inhibitors implicate nontraditional c-Raf and Lyn function as drivers of retinoic acid-induced maturation

The multivariate nature of cancer necessitates multi-targeted therapy, and kinase inhibitors account for a vast majority of approved cancer therapeutics. While acute promyelocytic leukemia (APL) patients are highly responsive to retinoic acid (RA) therapy, kinase inhibitors have been gaining momentum as co-treatments with RA for non-APL acute myeloid leukemia (AML) differentiation therapies, especially as a means to treat relapsed or refractory AML patients. In this study GW5074 (a c-Raf inhibitor) and PP2 (a Src-family kinase inhibitor) enhanced RA-induced maturation of t(15;17)-negative myeloblastic leukemia cells and rescued response in RA-resistant cells. PD98059 (a MEK inhibitor) and Akti-1/2 (an Akt inhibitor) were less effective, but did tend to promote maturation-uncoupled G1/G0 arrest, while wortmannin (a PI3K inhibitor) did not enhance differentiation surface marker expression or growth arrest. PD98059 and Akti-1/2 did not enhance differentiation markers and have potential, antagonistic off-targets effects on the aryl hydrocarbon receptor (AhR), but neither could the AhR agonist 6-formylindolo(3,2-b)carbazole (FICZ) rescue differentiation events in the RA-resistant cells. GW5074 rescued early CD38 expression in RA-resistant cells exhibiting an early block in differentiation before CD38 expression, while for RA-resistant cells with differentiation blocked later, PP2 rescued the later differentiation marker CD11b; but surprisingly, the combination of the two was not synergistic. Kinases c-Raf, Src-family kinases Lyn and Fgr, and PI3K display highly correlated signaling changes during RA treatment, while activation of traditional downstream targets (Akt, MEK/ERK), and even the surface marker CD38, were poorly correlated with c-Raf or Lyn during differentiation. This suggests that an interrelated kinase module involving c-Raf, PI3K, Lyn and perhaps Fgr functions in a nontraditional way during RA-induced maturation or during rescue of RA induction therapy using inhibitor co-treatment in RA-resistant leukemia cells.

The Transmodulation of HER2 and EGFR by Substance P in Breast Cancer Cells Requires c-Src and Metalloproteinase Activation

Background

Substance P (SP) is a pleiotropic cytokine/neuropeptide that enhances breast cancer (BC) aggressiveness by transactivating tyrosine kinase receptors like EGFR and HER2. We previously showed that SP and its cognate receptor NK-1 (SP/NK1-R) signaling modulates the basal phosphorylation of HER2 and EGFR in BC, increasing aggressiveness and drug resistance. In order to elucidate the mechanisms responsible for NK-1R-mediated HER2 and EGFR transactivation, we investigated the involvement of c-Src (a ligand-independent mediator) and of metalloproteinases (ligand-dependent mediators) in HER2/EGFR activation.

Results and Discussion

Overexpression of NK-1R in MDA-MB-231 and its chemical inhibition in SK-BR-3, BT-474 and MDA-MB-468 BC cells significantly modulated c-Src activation, suggesting that this protein is a mediator of NK-1R signaling. In addition, the c-Src inhibitor 4-(4’-phenoxyanilino)-6,7-dimethoxyquinazoline prevented SP-induced activation of HER2. On the other hand, SP-dependent phosphorylation of HER2 and EGFR decreased substantially in the presence of the MMP inhibitor 1–10, phenanthroline monohydrate, and the dual inhibition of both c-Src and MMP almost abolished the activation of HER2 and EGFR. Moreover, the use of these inhibitors demonstrated that this Src and MMP-dependent signaling is important to the cell viability and migration capacity of HER2+ and EGFR+ cell lines.

Conclusion

Our results indicate that the transactivation of HER2 and EGFR by the pro-inflammatory cytokine/neuropeptide SP in BC cells is a c-Src and MMP-dependent process.

Transcriptional network analysis reveals that AT1 and AT2 angiotensin II receptors are both involved in the regulation of genes essential for glioma progression

Gliomas are aggressive primary brain tumors with high infiltrative potential. The expression of Angiotensin II (Ang II) receptors has been associated with poor prognosis in human astrocytomas, the most common type of glioma. In this study, we investigated the role of Angiotensin II in glioma malignancy through transcriptional profiling and network analysis of cultured C6 rat glioma cells exposed to Ang II and to inhibitors of its membrane receptor subtypes. C6 cells were treated with Ang II and specific antagonists of AT1 and AT2 receptors. Total RNA was isolated after three and six hours of Ang II treatment and analyzed by oligonucleotide microarray technology. Gene expression data was evaluated through transcriptional network modeling to identify how differentially expressed (DE) genes are connected to each other. Moreover, other genes co-expressing with the DE genes were considered in these analyses in order to support the identification of enriched functions and pathways. A hub-based network analysis showed that the most connected nodes in Ang II-related networks exert functions associated with cell proliferation, migration and invasion, key aspects for glioma progression. The subsequent functional enrichment analysis of these central genes highlighted their participation in signaling pathways that are frequently deregulated in gliomas such as ErbB, MAPK and p53. Noteworthy, either AT1 or AT2 inhibitions were able to down-regulate different sets of hub genes involved in protumoral functions, suggesting that both Ang II receptors could be therapeutic targets for intervention in glioma. Taken together, our results point out multiple actions of Ang II in glioma pathogenesis and reveal the participation of both Ang II receptors in the regulation of genes relevant for glioma progression. This study is the first one to provide systems-level molecular data for better understanding the protumoral effects of Ang II in the proliferative and infiltrative behavior of gliomas.

Synthesis of sulfonylhydrazone- and acylhydrazone-substituted 8-ethoxy-3-nitro-2H-chromenes as potent antiproliferative and apoptosis inducing agents

3-Nitro-2H-chromenes have recently been identified as a novel class of potent antitumor agents. In view of the favorable effects shown by sulfonylhydrazones and acylhydrazones, we designed and synthesized a series of sulfonylhydrazone- and acylhydrazone-substituted 8-ethoxy-3-nitro-2H-chromene derivatives, and evaluated their cell growth inhibition activities against A549, KG-1, A2780, and K562 cells. All the tested compounds exhibited more potent antiproliferative activity than BENC-511 against KG-1 cells. These compounds displayed IC50 values in the nanomolar range against A2780 cells. Compound 7d showed prominent cytotoxicity against K562 cells with an IC50 of 0.11 µM, which was comparable to that of BENC-511. Compound 7d arrested K562 cells at the G1 phase at high concentrations and induced apoptosis in K562 cells. Furthermore, 7d increased the levels of cleaved caspase-3, decreased the expression of bcl-2 and induced the cleavage of poly(ADP-ribose) polymerase in K562 cells. Thus, this study provides the development of a series of novel compounds as effective antitumor agents with apoptotic death ability.

Overexpression of membrane metalloendopeptidase inhibits substance P stimulation of cholangiocarcinoma growth

Substance P (SP) promotes cholangiocyte growth during cholestasis by activating its receptor, NK1R. SP is a proteolytic product of tachykinin (Tac1) and is deactivated by membrane metalloendopeptidase (MME). This study aimed to evaluate the functional role of SP in the regulation of cholangiocarcinoma (CCA) growth. NK1R, Tac1, and MME expression and SP secretion were assessed in human CCA cells and nonmalignant cholangiocytes. The proliferative effects of SP (in the absence/presence of the NK1R inhibitor, L-733,060) and of L-733,060 were evaluated. In vivo, the effect of L-733,060 treatment or MME overexpression on tumor growth was evaluated by using a xenograft model of CCA in nu/nu nude mice. The expression of Tac1, MME, NK1R, PCNA, CK-19, and VEGF-A was analyzed in the resulting tumors. Human CCA cell lines had increased expression of Tac1 and NK1R, along with reduced levels of MME compared with nonmalignant cholangiocytes, resulting in a subsequent increase in SP secretion. SP treatment increased CCA cell proliferation in vitro, which was blocked by L-733,060. Treatment with L-733,060 alone inhibited CCA proliferation in vitro and in vivo. Xenograft tumors derived from MME-overexpressed human Mz-ChA-1 CCA cells had a slower growth rate than those derived from control cells. Expression of PCNA, CK-19, and VEGF-A decreased, whereas MME expression increased in the xenograft tumors treated with L-733,060 or MME-overexpressed xenograft tumors compared with controls. The study suggests that SP secreted by CCA promotes CCA growth via autocrine pathway. Blockade of SP secretion and NK1R signaling may be important for the management of CCA.

The Src-family kinase inhibitor PP2 rescues inducible differentiation events in emergent retinoic acid-resistant myeloblastic leukemia cells

Retinoic acid is an embryonic morphogen and dietary factor that demonstrates chemotherapeutic efficacy in inducing maturation in leukemia cells. Using HL60 model human myeloid leukemia cells, where all-trans retinoic acid (RA) induces granulocytic differentiation, we developed two emergent RA-resistant HL60 cell lines which are characterized by loss of RA-inducible G1/G0 arrest, CD11b expression, inducible oxidative metabolism and p47^phox expression. However, RA-treated RA-resistant HL60 continue to exhibit sustained MEK/ERK activation, and one of the two sequentially emergent resistant lines retains RA-inducible CD38 expression. Other signaling events that define the wild-type (WT) response are compromised, including c-Raf phosphorylation and increased expression of c-Cbl, Vav1, and the Src-family kinases (SFKs) Lyn and Fgr. As shown previously in WT HL60 cells, we found that the SFK inhibitor PP2 significantly increases G1/G0 cell cycle arrest, CD38 and CD11b expression, c-Raf phosphorylation and expression of the aforementioned regulators in RA-resistant HL60. The resistant cells were potentially incapable of developing inducible oxidative metabolism. These results motivate the concept that RA resistance can occur in steps, wherein growth arrest and other differentiation events may be recovered in both emergent lines. Investigating the mechanistic anomalies in resistant cell lines is of therapeutic significance and helps to mechanistically understand the response to retinoic acid’s biological effects in WT HL60 cells.

Alpha-2 adrenergic stimulation triggers Achilles tenocyte hypercellularity: Comparison between two model systems

The histopathology of tendons with painful tendinopathy is often tendinosis, a fibrosis-like condition of unclear pathogenesis characterized by tissue changes including hypercellularity. The primary tendon cells (tenocytes) have been shown to express adrenoreceptors (mainly alpha-2A) as well as markers of catecholamine production, particularly in tendinosis. It is known that adrenergic stimulation can induce proliferation in other cells. The present study investigated the effects of an exogenously administered alpha-2 adrenergic agonist in an established in vivo Achilles tendinosis model (rabbit) and also in an in vitro human tendon cell culture model. The catecholamine producing enzyme tyrosine hydroxylase and the alpha-2A-adrenoreceptor (α_2A AR) were expressed by tenocytes, and alpha-2 adrenergic stimulation had a proliferative effect on these cells, in both models. The proliferation was inhibited by administration of an α_2A AR antagonist, and the in vitro model further showed that the proliferative alpha-2A effect was mediated via a mitogenic cell signaling pathway involving phosphorylation of extracellular-signal-regulated kinases 1 and 2. The results indicate that catecholamines produced by tenocytes in tendinosis might contribute to the proliferative nature of the pathology through stimulation of the α_2A AR, pointing to a novel target for future therapies. The study furthermore shows that animal models are not necessarily required for all aspects of this research.

Substance P derivatives as versatile tools for specific delivery of various types of biomolecular cargo

The use of proteins or nucleic acids as therapeutic agents has been severely hampered by their intrinsic inability to cross the cell membrane. Moreover, common techniques for driving the delivery of macromolecules lack the ability to distinguish between healthy and diseased tissue, precluding their clinical use. Recently, receptor-mediated delivery (RMD) has emerged as a technology with the potential to circumvent the obstacles associated with the delivery of drug targets by utilizing the natural endocytosis of a ligand upon binding to its receptor. Here, we describe the synthesis of variants of substance P (SP), an eleven amino acid neuropeptide ligand of the neurokinin type 1 receptor (NK1R), for the delivery of various types of cargo. The variants of SP were synthesized with an N-terminal maleimide moiety that allows conjugation to surface thiols, resulting in a nonreducible thioether. Cargos lacking an available thiol are conjugated to SP using commercially available cross-linkers. In addition to the delivery of proteins, we expand the use of SP to include nuclear delivery of DNA fragments that are actively expressed in the target cells. We also show that SP can be used to deliver whole bacteriophage particles as well as polystyrene beads up to 1 μm in diameter. The results show the ability of SP to deliver cargo of various sizes and chemical properties that retain their function within the cell. Furthermore, the overexpression of the NK1R in many tumors provides the potential for developing targeted delivery reagents that are specific toward diseased tissue.

Substance P is a mechanoresponsive, autocrine regulator of human tenocyte proliferation

It has been hypothesised that substance P (SP) may be produced by primary fibroblastic tendon cells (tenocytes), and that this production, together with the widespread distribution of the neurokinin-1 receptor (NK-1 R) in tendon tissue, could play an important role in the development of tendinopathy, a condition of chronic tendon pain and thickening. The aim of this study was to examine the possibility of endogenous SP production and the expression of NK-1 R by human tenocytes. Because tendinopathy is related to overload, and because the predominant tissue pathology (tendinosis) underlying early tendinopathy is characterized by tenocyte hypercellularity, the production of SP in response to loading/strain and the effects of exogenously administered SP on tenocyte proliferation were also studied. A cell culture model of primary human tendon cells was used. The vast majority of tendon cells were immunopositive for the tenocyte/fibroblast markers tenomodulin and vimentin, and immunocytochemical counterstaining revealed that positive immunoreactions for SP and NK-1 R were seen in a majority of these cells. Gene expression analyses showed that mechanical loading (strain) of tendon cell cultures using the FlexCell© technique significantly increased the mRNA levels of SP, whereas the expression of NK-1 R mRNA decreased in loaded as compared to unloaded tendon cells. Reduced NK-1 R protein was also observed, using Western blot, after exogenously administered SP at a concentration of 10⁻⁷ M. SP exposure furthermore resulted in increased cell metabolism, increased cell viability, and increased cell proliferation, all of which were found to be specifically mediated via the NK-1 R; this in turn involving a common mitogenic cell signalling pathway, namely phosphorylation of ERK1/2. This study indicates that SP, produced by tenocytes in response to mechanical loading, may regulate proliferation through an autocrine loop involving the NK-1 R.

Glioblastoma: synergy of growth promotion between CCL5 and NK-1R can be thwarted by blocking CCL5 with miraviroc, an FDA approved anti-HIV drug and blocking NK-1R with aprepitant, an FDA approved anti-nausea drug

WHAT IS KNOWN AND BACKGROUND

Two receptor signaling pathways that are commonly active in facilitating glioblastoma growth and invasion- that of CCR5 and neurokinin (NK)-1R- have small molecule inhibitors that are FDA approved and marketed to treat other conditions. The anti-HIV drug, maraviroc, inhibits human CCR5's ligand from binding, and hence blocks CCR5 stimulation. The anti-nausea drug aprepitant blocks substance P signaling at NK-1R.

AIMS AND OBJECTIVE

We propose on the basis of molecular insights that a combination of the two drugs is likely to be useful in the treatment of glioblastoma.

COMMENT

After stimulation by their respective ligands both CCR5 and NK-1R, through intermediaries, phosphorylate and thereby activate ERK1/2, triggering in turn migratory and mitotic events. Neurokinin-1R second messenger signaling also happens to serine phosphorylate CCR5. Phosphorylated CCR5 exhibits amplified activity after agonist ligation. Therefore, aprepitant and maraviroc combined treatment is expected to exert synergestic inhibition of growth enhancing signaling in glioblastoma. Inhibiting an amplifier is equivalent to amplifying an inhibitor. Since the two suggested drugs are non-cytotoxic they are envisioned as adjunctive treatments to current standard temozolomide, radiation, and bevacizumab, all to be used after debulking primary resection.

WHAT IS NEW AND CONCLUSION

Our analysis makes the case for a well-designed trial of the proposed combination in the treatment of glioblastoma.

Association of the GNB3 825T-allele with better survival in patients with glioblastoma multiforme

PURPOSE

Genotypes of the C825T polymorphism of the GNB3 gene encoding the G protein beta3 subunit were recently associated with the prognosis of different malignomas. We investigated potential associations of GNB3 genotypes with survival of patients with glioblastoma multiforme (GBM).

METHODS

One hundred and sixty-one patients suffering from GBM were retrospectively investigated. Inclusion criteria were availability of DNA and a follow-up of at least 24 months. The results were evaluated with respect to the basic clinical data, type of surgical intervention, MGMT promoter methylation, adjuvant therapy, and survival.

RESULTS

After 2 years of first diagnosis, 128 (79.5%) of the 161 patients had died, 33 (20.5%) were alive. Kaplan-Meier curves revealed a significant higher rate of survival for homo- and heterozygous T-allele carriers (P = 0.019) with 38.5 and 25.3%, respectively, but only 11.6% for homozygous C-allele carriers. Multivariable Cox regression identified the heterozygous (hazard ratio 3.3, 95% CI 1.3-8.0, P = 0.010), as well as homozygous GNB3 825 C-allele (hazard ratio 3.7, 95% CI 1.5-9.1, P = 0.004) as an independent negative prognostic factor for 2-year survival according to the GNB3 825 TT genotype reference group.

CONCLUSIONS

Our data suggest an association of the GNB3 825TT genotype and better survival in patients with GBM.

S41744, a dual neurokinin (NK)1 receptor antagonist and serotonin (5-HT) reuptake inhibitor with potential antidepressant properties: a comparison to aprepitant (MK869) and paroxetine

Though neurokinin(1) (NK(1)) receptors are implicated in depressed states and their treatment, selective antagonists have disappointed in clinical trials. Accordingly, we designed a novel ligand, S41744 (2-piperazin-1-yl-indan-2-carboxylic-acid-(3-chloro-5-fluoro-benzyl)-methyl-amide), which both blocks NK(1) receptors and interferes with serotonin (5-HT) reuptake. S41744 mimicked the selective antagonist aprepitant in binding human (h)NK(1) receptors and in antagonising Substance-P-mediated Extracellular-Regulated-Kinase phosphorylation (pK(B), 7.7). Further, it dose-dependently (0.63-40.0 mg/kg, i.p.) displaced ex vivo [(3)H]-[Sar(9),Met(O(2))(11)]-Substance P binding to gerbil striatum, attenuated formalin-induced hind-paw licking in gerbils, and antagonised locomotion induced by i.c.v. administration of the NK(1) agonist GR73632 to guinea pigs. Like paroxetine, S41744 recognised h5-HT transporters, reduced synaptosomal uptake of 5-HT (pK(B), 7.9), and dose-dependently (0.63-10.0 mg/kg) elevated dialysis levels of 5-HT in the hippocampus and frontal cortex of freely-moving guinea pigs. Further, S41744 increased extracellular levels of 5-HT in frontal cortex and hippocampus of rats to a greater extent than paroxetine, and its inhibitory influence upon serotonergic perikarya was blunted relative to its affinity for 5-HT transporters. S41744 more potently blocked stress-induced vocalizations in guinea pigs than aprepitant and paroxetine, and it was active in forced-swim and marble-burying procedures of putative antidepressant properties in mice. While aprepitant displayed anxiolytic actions in stress-induced foot-tapping and social interaction tests in gerbils, paroxetine was anxiogenic and S41744 "neutral", reflecting balanced NK(1) antagonism and suppression of 5-HT reuptake. Moreover, S41744 shared anxiolytic actions of aprepitant in the rat Vogel Conflict Test. In conclusion, S41744 is an innovative NK(1) antagonist/5-HT reuptake inhibitor justifying further evaluation for treatment of stress-related disorders.

An engineered substance P variant for receptor-mediated delivery of synthetic antibodies into tumor cells

We have developed and tested a robust delivery method for the transport of proteins to the cytoplasm of mammalian cells without compromising the integrity of the cell membrane. This receptor-mediated delivery (RMD) technology utilizes a variant of substance P (SP), a neuropeptide that is rapidly internalized upon interaction with the neurokinin-1 receptor (NK1R). Cargos in the form of synthetic antibody fragments (sABs) were conjugated to the engineered SP variant (SPv) and efficiently internalized by NK1R-expressing cells. The sABs used here were generated to bind specific conformational forms of actin. The internalized proteins appear to escape the endosome and retain their binding activity within the cells as demonstrated by co-localization with the actin cytoskeleton. Further, since the NK1R is over-expressed in many cancers, SPv-mediated delivery provides a highly specific method for therapeutic utilization of affinity reagents targeting intracellular processes in diseased tissue.

Involvement of SRC family kinases in substance P-induced chemokine production in mouse pancreatic acinar cells and its significance in acute pancreatitis

Substance P is known to play a key role in the pathogenesis of acute pancreatitis. Src family kinases (SFKs) are known to be involved in cytokine signaling. However, the involvement of SFKs in substance P-induced chemokine production and its role in acute pancreatitis have not been investigated yet. To that end, we have used primary preparations of mouse pancreatic acinar cells as our model to show that substance P/neurokinin 1 receptor (NK1R) induced activation of SFKs. SFKs mediated the activation of mitogen-activated protein kinases [extracellular signal-regulated kinase (ERK), c-Jun NH(2)-terminal kinase (JNK)], transcription factors [signal transducer and activator of transcription (STAT) 3, nuclear factor (NF) kappaB, activator protein-1 (AP-1)], and production of chemokines in pancreatic acinar cells. We further tested the significance of the SFK signaling pathway in acute pancreatitis. Our results show, for the first time, that treatment of mice with the potent and selective SFK inhibitor PP2 [4-amino-5-(4-chlorophenyl)-7-(t-butyl) pyrazolo [3,4-D] pyrimidine], but not its negative inhibitor PP3 (4-amino-7-phenylpyrazol [3,4-D] pyrimidine), reduced the severity of pancreatitis. This was proven by significant attenuation of hyperamylasemia, pancreatic myeloperoxidase activity, chemokines, and water content. Histological evidence of diminished pancreatic injury also confirmed the protective effect of the inhibition of SFKs. Moreover, treatment with the substance P receptor antagonist CP96345 [(2S,3S)-cis-2-(diphenylmethyl)-N-((2-methoxyphenyl)-methyl)-1-azabicyclo(2.2.2.)-octan-3-amine] attenuated acute pancreatitis-induced activation of SFKs, ERK, JNK, STAT3, NFkappaB, and AP-1. The proposed signaling pathway through which substance P mediates acute pancreatitis is through substance P/NK1R-SFKs-(ERK, JNK)-(STAT3, NFkappaB, AP-1) chemokines. In light of our study, we propose that drugs targeting the substance P-mediated signaling pathways could prove beneficial in improving treatment efficacy in acute pancreatitis.

A constitutively active form of neurokinin 1 receptor and neurokinin 1 receptor-mediated apoptosis in glioblastomas

Previous studies have shown that neurokinin 1 receptor (NK1R) occurs naturally in human glioblastomas and its stimulation causes cell proliferation. In the present study we show that stimulation of NK1R in human U373 glioblastoma cells by substance P increases Akt phosphorylation by 2.5-fold, with an EC(50) of 57 nM. Blockade of NK1R lowers basal phosphorylation of Akt, indicating the presence of a constitutively active form of NK1R; similar results are seen in U251 MG and DBTRG-05 glioblastoma cells. Linkage of NK1R to Akt implicates NK1R in apoptosis of glioblastoma cells. Indeed, treatment of serum-starved U373 cells with substance P reduces apoptosis by 53 +/- 1% (p < 0.05), and treatment with NK1R antagonist L-733,060 increases apoptosis by 64 +/- 16% (p < 0.01). Further, the blockade of NK1R in human glioblastoma cells with L-733,060 causes cleavage of Caspase-3 and proteolysis of poly (ADP-ribose) polymerase. Experiments designed to elucidate the mechanism of NK1R-mediated Akt phosphorylation revealed total involvement of non-receptor tyrosine kinase Src and phosphatidyl-3-kinase, a partial involvement of epidermal growth factor receptor, and no involvement of mitogen-activated protein/extracellular signal-related kinase. Taken together, the results of the present study indicate a key role for NK1R in glioblastoma apoptosis.

Cellular and behavioural profile of the novel, selective neurokinin1 receptor antagonist, vestipitant: a comparison to other agents

This study characterized the novel neurokinin (NK)(1) antagonist, vestipitant, under clinical evaluation for treatment of anxiety and depression. Vestipitant possessed high affinity for human NK(1) receptors (pK(i), 9.4), and potently blocked Substance P-mediated phosphorylation of Extracellular-Regulated-Kinase. In vivo, it occupied central NK(1) receptors in gerbils (Inhibitory Dose(50), 0.11 mg/kg). At similar doses, it abrogated nociception elicited by formalin in gerbils, and blocked foot-tapping and locomotion elicited by the NK(1) agonist, GR73632, in gerbils and guinea pigs, respectively. Further, vestipitant attenuated fear-induced foot-tapping in gerbils, separation-induced distress-vocalizations in guinea pigs, marble-burying behaviour in mice, and displayed anxiolytic actions in Vogel conflict and fear-induced ultrasonic vocalization procedures in rats. These actions were mimicked by CP99,994, L733,060 and GR205,171 which acted stereoselectively vs its less active isomer, GR226,206. In conclusion, vestipitant is a potent NK(1) receptor antagonist: its actions support the utility of NK(1) receptor blockade in the alleviation of anxiety and, possibly, depression.

Differences in the length of the carboxyl terminus mediate functional properties of neurokinin-1 receptor

The neurokinin-1 receptor (NK1R) has two naturally occurring forms that differ in the length of the carboxyl terminus: a full-length receptor consisting of 407 aa and a truncated receptor consisting of 311 aa. We examined whether there are differential signaling properties attributable to the carboxyl terminus of this receptor by using stably transfected human embryonic kidney (HEK293) cell lines that express either full-length or truncated NK1R. Substance P (SP) specifically triggered intracellular calcium increase in HEK293 cells expressing full-length NK1R but had no effect in the cells expressing the truncated NK1R. In addition, in cells expressing full-length NK1R, SP activated NF-kappaB and IL-8 mRNA expression, but in cells expressing the truncated NK1R, SP did not activate NF-kappaB, and it decreased IL-8 mRNA expression. In cells expressing full-length NK1R, SP stimulated phosphorylation of PKCdelta but inhibited phosphorylation of PKCdelta in cells expressing truncated NK1R. There are also differences in the timing of SP-induced ERK activation in cells expressing the two different forms of the receptor. Full-length NK1R activation of ERK was rapid (peak within 1-2 min), whereas truncated NK1R-mediated activation was slower (peak at 20-30 min). Thus, the carboxyl terminus of NK1R is the structural basis for differences in the functional properties of the full-length and truncated NK1R. These differences may provide important information toward the design of new NK1R receptor antagonists.

EGF regulates plasminogen activator inhibitor-1 (PAI-1) by a pathway involving c-Src, PKCdelta, and sphingosine kinase 1 in glioblastoma cells

Patients with gliomas expressing high levels of epidermal growth factor receptor (EGFR) and plasminogen activator inhibitor-1 (PAI-1) have a shorter overall survival prognosis. Moreover, EGF enhances PAI-1 expression in glioma cells. Although multiple known signaling cascades are activated by EGF in glioma cells, we show for the first time that EGF enhances expression of PAI-1 via sequential activation of c-Src, protein kinase C delta (PKCdelta), and sphingosine kinase 1 (SphK1), the enzyme that produces sphingosine-1-phosphate. EGF induced rapid phosphorylation of c-Src and PKCdelta and concomitant translocation of PKCdelta as well as SphK1 to the plasma membrane. Down-regulation of PKCdelta abolished EGF-induced SphK1 translocation and up-regulation of PAI-1 by EGF; whereas, down-regulation of PKCalpha had no effect on the EGF-induced PAI-1 activation but enhanced its basal expression. Similarly, inhibition of c-Src activity by PP2 blocked both EGF-induced translocation of SphK1 and PKCdelta to the plasma membrane and up-regulation of PAI-1 expression. Furthermore, SphK1 was indispensable for both EGF-induced c-Jun phosphorylation and PAI-1 expression. Collectively, our results provide a functional link between three critical downstream targets of EGF, c-Src, PKCdelta, and SphK1 that have all been implicated in regulating motility and invasion of glioma cells.

Molecular mechanisms mediating the G protein-coupled receptor regulation of cell cycle progression

G protein-coupled receptors are key regulators of cellular communication, mediating the efficient coordination of a cell's responses to extracellular stimuli. When stimulated these receptors modulate the activity of a wide range of intracellular signalling pathways that facilitate the ordered development, growth and reproduction of the organism. There is now a growing body of evidence examining the mechanisms by which G protein-coupled receptors are able to regulate the expression, activity, localization and stability of cell cycle regulatory proteins that either promote or inhibit the initiation of DNA synthesis. In this review, we will detail the intracellular pathways that mediate the G protein-coupled receptor regulation of cellular proliferation, specifically the progression from the G1 phase to the S phase of the cell cycle.