Use of RT-PCR to detect co-expression of neuropeptides and their receptors in lung cancer

Chelator boosted tumor-retention and pharmacokinetic properties: development of 64Cu labeled radiopharmaceuticals targeting neurotensin receptor

PURPOSE

Accumulating evidence suggests that neurotensin (NTS) and neurotensin receptors (NTSRs) play key roles in lung cancer progression by triggering multiple oncogenic signaling pathways. This study aims to develop Cu-labeled neurotensin receptor 1 (NTSR1)-targeting agents with the potential for both imaging and therapeutic applications.

METHOD

A series of neurotensin receptor antagonists (NRAs) with variable propylamine (PA) linker length and different chelators were synthesized, including [64Cu]Cu-CB-TE2A-iPA-NRA ([64Cu]Cu-4a-c, i = 1, 2, 3), [64Cu]Cu-NOTA-2PA-NRA ([64Cu]Cu-4d), [64Cu]Cu-DOTA-2PA-NRA ([64Cu]Cu-4e, also known as [64Cu]Cu-3BP-227), and [64Cu]Cu-DOTA-VS-2PA-NRA ([64Cu]Cu-4f). The series of small animal PET/CT were conducted in H1299 lung cancer model. The expression profile of NTSR1 was also confirmed by IHC using patient tissue samples.

RESULTS

For most of the compounds studied, PET/CT showed prominent tumor uptake and high tumor-to-background contrast, but the tumor retention was strongly influenced by the chelators used. For previously reported 4e, [64Cu]Cu-labeled derivative showed initial high tumor uptake accompanied by rapid tumor washout at 24 h. The newly developed [64Cu]Cu-4d and [64Cu]Cu-4f demonstrated good tumor uptake and tumor-to-background contrast at early time points, but were less promising in tumor retention. In contrast, our lead compound [64Cu]Cu-4b demonstrated 9.57 ± 1.35, 9.44 ± 2.38 and 9.72 ± 4.89%ID/g tumor uptake at 4, 24, and 48 h p.i., respectively. Moderate liver uptake (11.97 ± 3.85, 9.80 ± 3.63, and 7.72 ± 4.68%ID/g at 4, 24, and 48 h p.i.) was observed with low uptake in most other organs. The PA linker was found to have a significant effect on drug distribution. Compared to [64Cu]Cu-4b, [64Cu]Cu-4a had a lower background, including a greatly reduced liver uptake, while the tumor uptake was only moderately reduced. Meanwhile, [64Cu]Cu-4c showed increased uptake in both the tumor and the liver. The clinical relevance of NTSR1 was also demonstrated by the elevated tumor expression in patient tissue samples.

CONCLUSIONS

Through the side-by-side comparison, [64Cu]Cu-4b was identified as the lead agent for further evaluation based on its high and sustained tumor uptake and moderate liver uptake. It can not only be used to efficiently detect NTSR1 expression in lung cancer (for diagnosis, patient screening, and treatment monitoring), but also has the great potential to treat NTSR-positive lesions once chelating to the beta emitter 67Cu.

LncRNA SLCO4A1-AS1 suppresses lung cancer progression by sequestering the TOX4-NTSR1 signaling axis

BACKGROUND

Metastasis is a multistep process involving the migration and invasion of cancer cells and is a hallmark of cancer malignancy. Long non-coding RNAs (lncRNAs) play critical roles in the regulation of metastasis. This study aims to elucidate the role of the lncRNA solute carrier organic anion transporter family member 4A1-antisense 1 (SLCO4A1-AS1) in metastasis and its underlying regulatory mechanisms.

METHODS

A comprehensive analysis of the Gene Expression Omnibus (GEO) database were used to identify metastasis-associated lncRNAs. Transwell migration and invasion assays, and a tail vein-injection mouse model were used to assess the migration and invasion of cancer cells in vitro and in vivo, respectively. High-throughput screening methods, including MASS Spectrometry and RNA sequencing (RNA-seq), were used to identify the downstream targets of SLCO4A1-AS1. Reverse transcription quantitative polymerase chain reaction (RT-qPCR), western blotting, RNA pull-down, RNA immunoprecipitation (RIP), fluorescence in situ hybridization (FISH), and chromatin immunoprecipitation (ChIp) assays were conducted to identify and validate the underlying regulatory mechanisms of SLCO4A1-AS1.

RESULTS

SLCO4A1-AS1 reduced cancer cell migration and invasion by disrupting cytoskeleton filaments, and was associated with longer overall survival in patients with lung adenocarcinoma. SLCO4A1-AS1 directly interacted with the DNA-binding protein, TOX High Mobility Group Box Family Member 4 (TOX4), to inhibit TOX4-induced migration and invasion. Furthermore, RNA-seq revealed that neurotensin receptor 1 (NTSR1) is a novel and convergent downstream target of SLCO4A1-AS1 and TOX4. Mechanistically, SLCO4A1-AS1 functions as a decoy of TOX4 by interrupting its interaction with the NTSR1 promoter and preventing NTSR1 transcription. Functionally, NTSR1 promotes cancer cell migration and invasion through cytoskeletal remodeling, and knockdown of NTSR1 significantly inhibits TOX4-induced migration and invasion.

CONCLUSION

These findings demonstrated that SLCO4A1-AS1 antagonizes TOX4/NTSR1 signaling, underscoring its pivotal role in lung cancer cell migration and invasion. These findings hold promise for the development of novel therapeutic strategies targeting the SLCO4A1-AS1/TOX4/NTSR1 axis as a potential avenue for effective therapeutic intervention in lung cancer.

Adding of neurotensin to non-small cell lung cancer cells increases tyrosine phosphorylation of HER3

Neurotensin (NTS) receptor 1 regulates the growth non-small cell lung cancer (NSCLC) cells. NTS binds with high affinity to NTSR1, leading to increased tyrosine phosphorylation of the EGFR and HER2. Using Calu3, NCI-H358, or NCI-H441 cells, the effects of NTS on HER3 transactivation were investigated. HER3 tyrosine phosphorylation was increased by NTS or neuregulin (NRG1) addition to NSCLC cells. NCI-H358, NCI-H441, and Calu-3 cells have HER3, NTSR1 and neuregulin (NRG)1 protein. NTSR1 regulation of HER3 transactivation was impaired by SR48692 (NTSR1 antagonist) or monoclonal antibody (mAb)3481 (HER3 blocker). Immunoprecipitation experiments indicated that NTS addition to NCI-H441cells resulted in the formation of EGFR/HER3 and HER2/HER3 heterodimers. The ability of NTS to increase HER3 tyrosine phosphorylation was impaired by GM6001 (MMP inhibitor), PP2 (Src inhibitor), Tiron (superoxide scavenger), or N-acetylcysteine (antioxidant). Adding NTS to NSCLC cells increased phosphorylation of ERK, HER3, and AKT. NTS or NRG1 increased colony formation of NSCLC cells which was strongly inhibited by SR48692 and mAb3481. The results indicate that NTSR1 regulates HER3 transactivation in NSCLC cells leading to increased proliferation.

Neurotensin receptor 1 signaling promotes pancreatic cancer progression

Pancreatic cancer is one of the cancers with the poorest prognosis, with a 5-year survival rate of approximately 5-10%. Thus, it is urgent to identify molecular targets for the treatment of pancreatic cancer. Using serial transplantations in a mouse pancreatic orthotopic inoculation model, we previously produced highly malignant pancreatic cancer sublines with increased tumor-forming abilities in vivo. Here, we used these sublines to screen molecular targets for the treatment of pancreatic cancer. Among the genes with increased expression levels in the sublines, we focused on those encoding cell surface receptors that may be involved in the interactions between cancer cells and the tumor microenvironment. Based on our previous RNA-sequence analysis, we found increased expression levels of neurotensin (NTS) receptor 1 (NTSR1) in highly malignant pancreatic cancer sublines. Furthermore, re-analysis of clinical databases revealed that the expression level of NTSR1 was increased in advanced pancreatic cancer and that high NTSR1 levels were correlated with a poor prognosis. Overexpression of NTSR1 in human pancreatic cancer cells Panc-1 and SUIT-2 accelerated their tumorigenic and metastatic abilities in vivo. In addition, RNA-sequence analysis showed that MAPK and NF-κB signaling pathways were activated upon NTS stimulation in highly malignant cancer sublines and also revealed many new target genes for NTS in pancreatic cancer cells. NTS stimulation increased the expression of MMP-9 and other pro-inflammatory cytokines and chemokines in pancreatic cancer cells. Moreover, the treatment with SR48692, a selective NTSR1 antagonist, suppressed the activation of the MAPK and NF-κB signaling pathways and induction of target genes in pancreatic cancer cells in vitro, while the administration of SR48692 attenuated the tumorigenicity of pancreatic cancer cells in vivo. These findings suggest that NTSR1 may be a prognostic marker and a molecular target for pancreatic cancer treatment.

Dual Peptide-Modified Nanoparticles Improve Combination Chemotherapy of Etoposide and siPIK3CA Against Drug-Resistant Small Cell Lung Carcinoma

Small cell lung carcinoma (SCLC) is a highly aggressive form of malignancy with rapid recurrence and poor prognosis. The dual peptide-modified nanoparticles (NPs) for improving chemotherapy against drug-resistant small cell lung carcinoma cells has been developed. In this study, the SCLC targeting ligand, antagonist G peptide (AG), and cell-penetrating peptide, TAT, modified NPs were used to encapsulate both anticancer drugs etoposide (ETP) and PIK3CA small-interfering RNA (siPIK3CA). The ETP@NPs and siRNA@NPs had particle size 201.0 ± 1.9-206.5 ± 0.7 nm and 155.3 ± 12.4-169.1 ± 11.2 nm, respectively. The lyophilized ETP@NPs and siRNA@NPs maintained their particle size and zeta potential during 28-day storage without severe aggregation or dissociation. Either ETP@NPs or siRNA@NPs significantly reduced the IC₅₀ of drugs by 2.5-5.5 folds and 2.4-3.9 folds, respectively, as compared to free ETP and siRNA/PEI nanocomplex in drug-resistant CD133(+) H69 cells. Herein, the IC₅₀ of dual-peptide modified ETP@NPs and siRNA@NPs were prominently lower than single-peptide modified NPs. The synergistic effect (CI < 1) was further observed in co-treatment of ETP and siPIK3CA particularly delivered by dual-peptide modified NPs.

Upregulation of Thr/Tyr kinase Increases the Cancer Progression by Neurotensin and Dihydropyrimidinase-Like 3 in Lung Cancer

Lung cancer is one of the leading causes of cancer-related death globally, thus elucidation of its molecular pathology is highly highlighted. Aberrant alterations of the spindle assembly checkpoint (SAC) are implicated in the development of cancer due to abnormal cell division. TTK (Thr/Tyr kinase), a dual serine/threonine kinase, is considered to act as a cancer promoter by controlling SAC. However, the mechanistic details of how TTK-mediated signaling network supports cancer development is still a mystery. Here, we found that TTK was upregulated in the tumor tissue of patients with lung cancer, and enhanced tumor growth and metastasis in vitro and in vivo. Mechanistically, TTK exerted a significant enhancement in cancer growth by neurotensin (NTS) upregulation, and subsequently increased the expression of cyclin A and cdk2, which was resulting in the increase of DNA synthesis. In contrast, TTK increased cell migration and epithelial-to-mesenchymal transition (EMT) by enhancing the expression of dihydropyrimidinase-like 3 (DPYSL3) followed by the increase of snail-regulated EMT, thus reinforce metastatic potential and ultimately tumor metastasis. TTK and DPYSL3 upregulation was positively correlated with a poor clinical outcome in patients with lung cancer. Together, our findings revealed a novel mechanism underlying the oncogenic potential effect of TTK and clarified its downstream factors NTS and DPYSL3 might represent a novel, promising candidate oncogenes with potential therapeutic vulnerabilities in lung cancer.

Neurotensin receptors regulate transactivation of the EGFR and HER2 in a reactive oxygen species-dependent manner

Neurotensin is a 13 amino acid peptide which is present in many lung cancer cell lines. Neurotensin binds with high affinity to the neurotensin receptor 1, and functions as an autocrine growth factor in lung cancer cells. Neurotensin increases tyrosine phosphorylation of the epidermal growth factor receptor (EGFR) and the neurotensin receptor 1 antagonist SR48692 blocks the transactivation of the EGFR. Here the effects of reactive oxygen species on the transactivation of the EGFR and HER2 were investigated. Using non-small cell lung cancer (NSCLC) cell lines, neurotensin receptor 1 mRNA and protein were present. Using NCI-H838 cells, neurotensin or neurotensin^8-13 but not neurotensin^1-8 increased EGFR, ERK and HER2 tyrosine phosphorylation which was blocked by SR48692. Neurotensin addition to NCI-H838 cells increased significantly reactive oxygen species which was inhibited by SR48692, Tiron (superoxide scavenger) and diphenylene iodonium (DPI inhibits the ability of NADPH oxidase and dual oxidase enzymes to produce reactive oxygen species). Tiron or DPI impaired the ability of neurotensin to increase EGFR, ERK and HER2 tyrosine phosphorylation. Neurotensin stimulated NSCLC cellular proliferation whereas the growth was inhibited by SR48692, DPI or lapatinib (lapatinib is tyrosine kinase inhibitor of the EGFR and HER2). Lapatinib inhibited the ability of the neurotensin receptor 1 to transactivate the EGFR and HER2. The results indicate that neurotensin receptor 1 regulates the transactivation of the EGFR and HER2 in a reactive oxygen species-dependent manner.

Validation of Neurotensin Receptor 1 as a Therapeutic Target for Gastric Cancer

Gastric cancer is the fifth most common type of malignancy worldwide, and the survival rate of patients with advanced-stage gastric cancer is low, even after receiving chemotherapy. Here, we validated neurotensin receptor 1 (NTSR1) as a potential therapeutic target in gastric cancer. We compared NTSR1 expression levels in sixty different gastric cancer-tissue samples and cells, as well as in other cancer cells (lung, breast, pancreatic, and colon), by assessing NTSR1 expression via semi-quantitative real-time reverse transcription polymerase chain reaction, immunocytochemistry and western blot. Following neurotensin (NT) treatment, we analyzed the expression and activity of matrix metalloproteinase-9 (MMP-9) and further determined the effects on cell migration and invasion via wound-healing and transwell assays. Our results revealed that NTSR1 mRNA levels were higher in gastric cancer tissues than non-cancerous tissues. Both of NTSR1 mRNA levels and expression were higher in gastric cancer cell lines relative to levels observed in other cancer-cell lines. Moreover, NT treatment induced MMP-9 expression and activity in all cancer cell lines, which was significantly decreased following treatment with the NTSR1 antagonist SR48692 or small-interfering RNA targeting NTSR1. Furthermore, NT-mediated metastases was confirmed by observing epithelial-mesenchymal transition markers SNAIL and E-cadherin in gastric cancer cells. NT-mediated invasion and migration of gastric cancer cells were reduced by NTSR1 depletion through the Erk signaling. These findings strongly suggested that NTR1 constitutes a potential therapeutic target for the inhibition of gastric cancer invasion and metastasis.

Oncogenic role of neurotensin and neurotensin receptors in various cancers

Neurotensin (NTS) has long been recognized as a neurotransmitter or neuromodulator in the central nervous system and as an endocrine agent in the periphery via actions mediated through neurotensin receptors (NTSRs). Many studies support a role for NTS in the endocrine, autocrine and paracrine growth stimulation of cancer, with oncogenic actions described for NTS in different types of cancers and cancer cell lines at each step of cancer progression, ranging from tumour growth and survival to metastatic spread. The mechanisms underlying the effects of the NTS/NTSR system in cell proliferation, migration and invasion, as well as the anti-apoptotic effects of this system, have been elucidated in different types of cancers, and include mitogen-activated protein kinases, phosphatidylinositol 3-kinase and RhoGTPases. The present mini review summarizes recent findings relating to the oncogenic function of the NTS/NTSR system.

Exploiting cancer's phenotypic guise against itself: targeting ectopically expressed peptide G-protein coupled receptors for lung cancer therapy

Lung cancer, claiming millions of lives annually, has the highest mortality rate worldwide. This advocates the development of novel cancer therapies that are highly toxic for cancer cells but negligibly toxic for healthy cells. One of the effective treatments is targeting overexpressed surface receptors of cancer cells with receptor-specific drugs. The receptors-in-focus in the current review are the G-protein coupled receptors (GPCRs), which are often overexpressed in various types of tumors. The peptide subfamily of GPCRs is the pivot of the current article owing to the high affinity and specificity to and of their cognate peptide ligands, and the proven efficacy of peptide-based therapeutics. The article summarizes various ectopically expressed peptide GPCRs in lung cancer, namely, Cholecystokinin-B/Gastrin receptor, the Bombesin receptor family, Bradykinin B1 and B2 receptors, Arginine vasopressin receptors 1a, 1b and 2, and the Somatostatin receptor type 2. The autocrine growth and pro-proliferative pathways they mediate, and the distinct tumor-inhibitory effects of somatostatin receptors are then discussed. The next section covers how these pathways may be influenced or 'corrected' through therapeutics (involving agonists and antagonists) targeting the overexpressed peptide GPCRs. The review proceeds on to Nano-scaled delivery platforms, which enclose chemotherapeutic agents and are decorated with peptide ligands on their external surface, as an effective means of targeting cancer cells. We conclude that targeting these overexpressed peptide GPCRs is potentially evolving as a highly promising form of lung cancer therapy.

Pentapeptides for the treatment of small cell lung cancer: Optimisation by Nind-alkyl modification of the tryptophan side chain

The pentapeptide, tert-Prenyl^4th-NH₂ (DMePhe-DTrp-Phe-DTrp(N-tert-prenyl)-Leu-NH₂), has recently been reported by our group to exhibit properties of substance P (SP) antagonist G against small cell lung cancer (SCLC). In this study, we undertook a systematic structure activity investigation to optimise this lead compound to improve its in vitro anti-tumour activity and biocompatibility. A series of d-tryptophan (D-Trp) derivatives were synthesised, with a range of aliphatic N-alkyl chains (methyl to pentyl) on the indole nitrogen (N^ind). These were incorporated into the pentapeptide sequence by substitution of the N^ind-tert-prenylated D-Trp 4th residue with the N^ind-alkylated D-Trp derivatives. These pentapeptides were significantly more potent than tert-Prenyl^4th-NH₂, with the N^ind-butyl modification generating the most cytotoxic peptides. Compared to tert-Prenyl^4th-NH₂, a single butyl modification on the 4th D-Trp residue (Butyl^4th-NH₂) showed a ∼3 fold enhancement in cytotoxicity in either the chemo-naive H69 or the DMS79 (originating from a patient treated with chemotherapeutics and radiation therapy) SCLC cell lines. In addition, the di-butylated sequence on the 2nd and 4th D-Trp residues (Butyl^2nd,4th-NH₂) gave ∼4.5 times higher cytotoxicity against the H69 cell line and a ∼2 fold increase against the DMS79 cell line, compared to tert-Prenyl^4th-NH₂. The favoured position for butyl modification was the 4th D-Trp residue, as the Butyl^2nd-NH₂ peptide gave lower cytotoxicity on both cell lines. Butylated peptide sequences, when exposed to neat mouse plasma for 24 h at 37 °C, were found to resist degradation with >80% remaining intact compared to ∼58% for tert-Prenyl^4th-NH₂. The degradation pathway in plasma occurs via de-amidation of the C-terminus, confirmed by mass spectrometry and RP-HPLC analysis. The butyl modification also conferred resistance to metabolism when tested using S9 liver fraction from mouse. The optimum analogue responsive against the DMS79 cell line was the Butyl^4th-NH₂ pentapeptide, which revealed a concentration dependent increase in apoptosis: the level of late apoptotic cells rose from ∼36% at 2 μM to ∼96% at 6 μM, as determined by flow cytometry, compared to the unmodified peptide that showed no such effect. Concluding, the butyl substitutions offered the best perspective for high cytotoxicity, induction of apoptosis and metabolic compatibility thereby comprising an improved broad spectrum SP antagonist candidate for treatment of SCLC.

Neuropeptide gastrin-releasing peptide induces PI3K/reactive oxygen species-dependent migration in lung adenocarcinoma cells

Nerve fibers and neurotransmitters have increasingly been shown to have a role in tumor progression. Gastrin-releasing peptide is a neuropeptide linked to tumor aggressiveness, acting as an autocrine tumor growth factor by binding to its receptor, gastrin-releasing peptide receptor, expressed by many tumors. Although neuropeptides have been previously linked to tumor cell proliferation, more recent studies have uncovered roles for neuropeptides in chemotaxis and metastasis. Understanding the precise roles of such peptides in cancer is crucial to optimizing targeted therapy design. We have previously described that gastrin-releasing peptide acts directly as a chemotactic factor for neutrophils, dependent on PI3K, ERK, and p38. In this study, we investigated roles for gastrin-releasing peptide in lung adenocarcinoma. We asked if gastrin-releasing peptide would act as a proliferative and/or chemotactic stimulus for gastrin-releasing peptide receptor-expressing tumor cells. In A549 cells, a non-small cell lung carcinoma line, the treatment with gastrin-releasing peptide leads to activation of AKT and ERK1/2, and production of reactive oxygen species. Gastrin-releasing peptide induced migration of A549 cells, dependent on gastrin-releasing peptide receptor and PI3K, but not ERK. However, no proliferation was observed in these cells in response to gastrin-releasing peptide, and gastrin-releasing peptide did not promote resistance to treatment with a chemotherapy drug. Our results suggest that, similar to what happens in neutrophils, gastrin-releasing peptide is a migratory, rather than a proliferative, stimulus, for non-small cell lung carcinoma cells, indicating a putative role for gastrin-releasing peptide and gastrin-releasing peptide receptor in metastasis.

Endothelin causes transactivation of the EGFR and HER2 in non-small cell lung cancer cells

Endothelin (ET)-1 is an important peptide in cancer progression stimulating cellular proliferation, tumor angiogenesis and metastasis. ET-1 binds with high affinity to the ET_A receptor (R) and ET_BR on cancer cells. High levels of tumor ET-1 and ET_AR are associated with poor survival of lung cancer patients. Here the effects of ET-1 on epidermal growth factor (EGF)R and HER2 transactivation were investigated using non-small cell lung cancer (NSCLC) cells. ET_AR mRNA was present in all 10 NSCLC cell lines examined. Addition of ET-1 to NCI-H838 or H1975 cells increased EGFR, HER2 and ERK tyrosine phosphorylation within 2min. The increase in EGFR and HER2 transactivation caused by ET-1 addition to NSCLC cells was inhibited by lapatinib (EGFR and HER2 tyrosine kinase inhibitor (TKI)), gefitinib (EGFR TKI), ZD4054 or BQ-123 (ET_AR antagonist), GM6001 (matrix metalloprotease inhibitor), PP2 (Src inhibitor) or Tiron (superoxide scavenger). ET-1 addition to NSCLC cells increased cytosolic Ca²⁺ and reactive oxygen species. ET-1 increased NSCLC clonal growth, whereas BQ123, ZD4054, lapatinib or gefitinib inhibited proliferation. The results indicate that ET-1 may regulate NSCLC cellular proliferation in an EGFR- and HER2-dependent manner.

CI-988 Inhibits EGFR Transactivation and Proliferation Caused by Addition of CCK/Gastrin to Lung Cancer Cells

Cholecystokinin (CCK) receptors are G-protein coupled receptors (GPCR) which are present on lung cancer cells. CCK-8 stimulates the proliferation of lung cancer cells, whereas the CCK2R receptor antagonist CI-988 inhibits proliferation. GPCR for some gastrointestinal hormones/neurotransmitters mediate lung cancer growth by causing epidermal growth factor receptor (EGFR) transactivation. Here, the role of CCK/gastrin and CI-988 on EGFR transactivation and lung cancer proliferation was investigated. Addition of CCK-8 or gastrin-17 (100 nM) to NCI-H727 human lung cancer cells increased EGFR Tyr(1068) phosphorylation after 2 min. The ability of CCK-8 to cause EGFR tyrosine phosphorylation was blocked by CI-988, gefitinib (EGFR tyrosine kinase inhibitor), PP2 (Src inhibitor), GM6001 (matrix metalloprotease inhibitor), and tiron (superoxide scavenger). CCK-8 nonsulfated and gastrin-17 caused EGFR transactivation and bound with high affinity to NCI-H727 cells, suggesting that the CCK2R is present. CI-988 inhibited the ability of CCK-8 to cause ERK phosphorylation and elevate cytosolic Ca(2+). CI-988 or gefitinib inhibited the basal growth of NCI-H727 cells or that stimulated by CCK-8. The results indicate that CCK/gastrin may increase lung cancer proliferation in an EGFR-dependent manner.

Neurotensin, a Novel Messenger to Cross-Link Inflammation and Tumor Invasion via Epithelial-Mesenchymal Transition Pathway

Multiple cytokines and growth factors are critical for the prognosis of cancer which has been regarded as a worldwide health problem. Recently, neuropeptides, soluble factors regulating a series of functions in the central nervous system, have also been demonstrated to stimulate the proliferation and migration of tumor cells. Among these signaling peptides, the role of neurotensin (NTS) on malignancy procession has become a hot topic. The effects of NTS on tumor growth and its antiapoptosis role have already been identified. Subsequently, studies demonstrated the impact of NTS on the migration and invasion, but the molecular mechanisms involved are still unclear at present. Recently, some reports indicated that NTS could induce expression and secretion of interleukin-8 (IL-8) to promote local imflammatory response which might participate in epithelial-mesenchymal transition (EMT)-related tumor migration. In present review, we highlight the process of tumor EMT induced by NTS through stimulating IL-8 and the significance of NTS/IL-8 pathway in clinical application prospect.

Prospective validation of quantitative NSE mRNA in pleural fluid of non-small cell lung cancer patients

Although the survival of lung cancer patients has improved significantly due to the development of early detective tools, lung cancer remains a leading cause of cancer-related death after curative surgery. So it is extremely important for cancer patients to predict early metastasis, especially pleural dissemination, the most frequent type of recurrence in patients after surgery. Based on a retrospective study of 86 curatively resected lung cancer patients (training set), we determined a cutoff value of NSE mRNA using receiver-operating characteristic curve. Then, we prospectively used this cutoff value to validate the risk of pleural recurrence in a new cohort of 81 lung cancer patients (validation set) between April 2009 and June 2010 by real-time reverse transcriptase-polymerase chain reaction. During the median 27 months of postoperative surveillance, 16 of the 81 patients died, and 9 of the 16 developed pleural metastases. Multivariate analysis with the Cox proportional hazards model showed that positive NSE mRNA was a significant independent risk factor with both overall survival and pleural recurrence-free survival (both P < 0.0001) as end points which were significantly worse in patients with positive NSE mRNA (P < 0.0001). These results indicate that quantitative NSE mRNA in pleural fluid is a reliable prognostic indicator of pleural recurrence in the clinical setting.

The synthesis of neurotensin antagonist SR 48692 for prostate cancer research

An improved synthesis of the molecule SR 48692 is presented and its use as a neurotensin antagonist biological probe for use in cancer research is described. The preparation includes an number of enhanced chemical conversions and strategies to overcome some of the limiting synthetic transformations in the original chemical route.

[99mTc]demotensin VI: biodistribution and initial clinical results in tumor patients of a pilot/phase I study

PURPOSE

Neurotensin subtype 1 receptor overexpression is found in a variety of human tumors. The aim of this pilot/phase I study was to assess the safety profile, pharmacokinetics, and imaging characteristics of (99m)Tc-Demotensin VI in tumor patients.

METHODS

Scintigraphy with (99m)Tc-Demotensin VI was performed in 14 patients (2 female and 12 male) with advanced tumor stages. The diagnoses were pancreatic adenocarcinoma (n=4), small cell lung cancer (SCLC) (n=4), non-small cell lung cancer (NSCLC) (n=4), and colon carcinoma (n=2). Patients were injected with 500-550 MBq (99m)Tc-Demotensin VI. Blood samples were taken at various time points and urine was also collected up to 24 hours post-injection (p.i.) Planar images were acquired at 15-30 minutes, 1-2 hours, 4 hours, and 24 hours p.i. with additional SPECT imaging at 4 hours.

RESULTS

Radiochemical purity always exceeded 95% up to 4 hours. Urinary and blood excretion was rapid with 5.05% ID (mean: n=5) in plasma after 4 hours. No side effects were observed after injection of (99m)Tc-Demotensin VI. Focal tracer accumulation was observed in 3 patients with brain metastases due to NSCLC, although specificity of this uptake could not be proven. Further, no tumor-related findings were observed. Although stability tests in human plasma revealed that (99m)Tc-Demotensin VI remained intact up to 2 hours incubation, ex vivo urine analysis indicated rapid metabolism.

CONCLUSION

(99m)Tc-Demotensin VI was well tolerated by patients and showed favorable pharmacokinetics; however, tumor targeting was limited to brain metastases. Further studies on stability issues and receptor characterization in tumors are warranted to introduce neurotensin receptors (NTSR) imaging into the clinic.

A novel tetrabranched neurotensin(8-13) cyclam derivative: synthesis, 64Cu-labeling and biological evaluation

New macrocyclic 1,4,8,11-tetraazacyclotetradecane (cyclam) derivatives with 1, 2 and 4 neurotensin(8-13) units 4, 5 and 7 have been synthesized. Compounds 4 and 5 were prepared by the reaction of non-stabilized neurotensin(8-13) and cyclamtetrapropionic acid 2 using 1-ethyl-3-(3-dimethylaminocarbonyl)carbodiimide-hydrochloride and N-hydroxysulfosuccinimide. The tetrameric compound 7 was synthesized by Michael addition of neurotensin(8-13) acrylamide 6 and cyclam 1. The copper(II) complexation behavior of 4, 5 and 7 was investigated by UV/visible spectrophotometry and shows that the metal center resides inside the N4 chromophore with additional apical interactions established with pendant arms. The novel tetrabranched NT(8-13) cyclam 7 with nanomolar neurotensin receptor 1 binding affinity was efficiently radiolabeled with (64)Cu under mild conditions. (64)Cu⊂7 showed slow transchelation in the presence of a large amount of cyclam as competing ligand, while it completely remains intact in the presence of EDTA. The in vivo behavior of (64)Cu⊂7 was studied in rats and mice. The metabolic stability in rodent models was high with a half-life of intact (64)Cu⊂7 in plasma of 34 min in rats and 60 min in the mice, respectively. The binding affinity was high enough to demonstrate in vivo binding of (64)Cu⊂7 to NTR1 overexpressing HT-29 tumor xenotransplants in nude mice. Regarding elimination, (64)Cu⊂7 showed a substantial renal and reticuloendothelial accumulation. On the other hand, metabolization of the compound in vivo with a resulting metabolite-postulated to be the (64)Cu-cyclam-tetraarginine complex-also showed long retention in the circulating blood, preventing a better contrast of tumor imaging.

Design of peptide-targeted liposomes containing nucleic acids

Anticancer systemic gene silencing therapy has been so far limited by the inexistence of adequate carrier systems that ultimately provide an efficient intracellular delivery into target tumor cells. In this respect, one promising strategy involves the covalent attachment of internalizing-targeting ligands at the extremity of PEG chains grafted onto liposomes. Therefore, the present work aims at designing targeted liposomes containing nucleic acids, with small size, high encapsulation efficiency and able to be actively internalized by SCLC cells, using a hexapeptide (antagonist G) as a targeting ligand. For this purpose, the effect of the liposomal preparation method, loading material (ODN versus siRNA) and peptide-coupling procedure (direct coupling versus post-insertion) on each of the above-mentioned parameters was assessed. Post-insertion of DSPE-PEG-antagonist G conjugates into preformed liposomes herein named as stabilized lipid particles, resulted in targeted vesicles with a mean size of about 130 nm, encapsulation efficiency close to 100%, and a loading capacity of approximately 5 nmol siRNA/mumol of total lipid. In addition, the developed targeted vesicles showed increased internalization in SCLC cells, as well as in other tumor cells and HMEC-1 microvascular endothelial cells. The improved cellular association, however, did not correlate with enhanced downregulation of the target protein (Bcl-2) in SCLC cells. These results indicate that additional improvements need to be performed in the future, namely by ameliorating the access of the nucleic acids to the cytoplasm of the tumor cells following receptor-mediated endocytosis.

Cancer, chemistry, and the cell: molecules that interact with the neurotensin receptors

The literature covering neurotensin (NT) and its signalling pathways, receptors, and biological profile is complicated by the fact that the discovery of three NT receptor subtypes has come to light only in recent years. Moreover, a lot of this literature explores NT in the context of the central nervous system and behavioral studies. However, there is now good evidence that the up-regulation of NT is intimately involved in cancer development and progression. This Review aims to summarize the isolation, cloning, localization, and binding properties of the accepted receptor subtypes (NTR1, NTR2, and NTR3) and the molecules known to bind at these receptors. The growing role these targets are playing in cancer research is also discussed. We hope this Review will provide a useful overview and a one-stop resource for new researchers engaged in this field at the chemistry-biology interface.

Targeting V1A-vasopressin receptors with [Arg6, D-Trp7,9, NmePhe8]-substance P (6-11) identifies a strategy to develop novel anti-cancer therapies

BACKGROUND AND PURPOSE

The anti-cancer agent [Arg(6), D-Trp(7,9), N(me)Phe(8)]-substance P (6-11) (SP-G) modulates gastrin releasing peptide (GRP) and arginine vasopressin signalling in small cell lung cancer cells leading to growth arrest and apoptosis. We have shown that SP-G acts as a biased agonist at GRP receptors. This work examines the hypothesis that SP-G acts as a biased agonist at the V(1A) vasopressin receptor.

EXPERIMENTAL APPROACH

The human V(1A) receptor was expressed in CHO-K1 cells. Extracellular regulated kinase (ERK) activation and intracellular Ca(2+) were measured using activation state-specific antibodies and Fura-2-AM respectively. The effect of SP-G on tumourigenicity was assessed by colony assay.

KEY RESULTS

In V(1A) receptor expressing cells, SP-G caused a sustained activation of ERK via a stimulation of V(1A) receptor coupling to G(i). Inhibition of G(i) with Pertussis toxin attenuated the inhibition by SP-G of the growth of CHO-K1 cells stably expressing the V(1A) receptor. Chimeric V(1A) receptors containing the second or third intracellular loop of the V(2) receptor were capable of binding vasopressin and SP-G but had altered ability to activate phospholipase C (PLC) and ERK. The second intracellular loop of the V(1A) receptor was essential for vasopressin-stimulated PLC and ERK activation but not for SP-G-induced ERK activation.

CONCLUSIONS AND IMPLICATIONS

This work provides mechanistic insight, for biased agonists at V(1A) receptors and highlights a potential role for such agents as anti-cancer agents.

SCG3 transcript in peripheral blood is a prognostic biomarker for REST-deficient small cell lung cancer

PURPOSE

Specific markers of circulating tumor cells may be informative in managing lung cancer. Because the RE-1 silencing transcription factor (REST/NRSF) is a transcriptional repressor that is inactivated in neuroendocrine lung cancer, we identified REST-regulated transcripts (CHGA, CHGB, SCG3, VGF, and PCSK1) for evaluation as biomarkers in peripheral blood.

EXPERIMENTAL DESIGN

Transcripts were screened across lung cancer and normal cell lines. Candidates were assessed by reverse transcription-PCR and hybridization of RNA extracted from the peripheral blood of 111 lung cancer patients obtained at clinical presentation and from 27 cancer-free individuals.

RESULTS

Expression profiling revealed multiple chromogranin transcripts were readily induced on REST depletion, most notably SCG3 was induced >500-fold. The SCG3 transcript was also overexpressed by 12,000-fold in neuroendocrine compared with nonneuroendocrine lung cancer cells. In peripheral blood of lung cancer patients and cancer-free individuals, we found that SCG3 was more tumor-specific and more sensitive than other chromogranin transcripts as a biomarker of circulating tumor cells. Overall, 36% of small cell lung cancer (SCLC) and 16% of non-SCLC patients scored positively for normalized SCG3 transcript. This correlated with worse survival among SCLC patients with limited disease (n = 33; P = 0.022) but not extensive disease (n = 29; P = 0.459). Interestingly, the subcohort of 6 SCLC patients with resistance to platinum/etoposide chemotherapy all scored positively for peripheral blood SCG3 transcript (P = 0.022).

CONCLUSIONS

SCG3 mRNA, a component of the REST-dependent neurosecretory transcriptional profile, provides a sensitive prognostic biomarker for noninvasive monitoring of neuroendocrine lung cancer.

Bronchopulmonary neuroendocrine tumors

Bronchopulmonary neuroendocrine tumors (BP-NETs) comprise approximately 20% of all lung cancers and represent a spectrum of tumors arising from neuroendocrine cells of the BP-epithelium. Although they share structural, morphological, immunohistochemical, and ultrastructural features, they are separated into 4 subgroups: typical carcinoid tumor (TC), atypical carcinoid tumor (AC), large-cell neuroendocrine carcinoma (LCNEC), and small-cell lung carcinoma (SCLC), which exhibit considerably different biological characteristics. The clinical presentation includes cough, hemoptysis, and obstructive pneumonia but varies depending on site, size, and growth pattern. Less than 5% of BP-NETs exhibit hormonally related symptoms such as carcinoid syndrome, Cushing, acromegaly, and SIADH. SCLC is the most common BP-NET, while LCNEC is rare, approximately 10% and < or =1%, respectively, of all lung cancers. Both SCLC and LCNEC progress rapidly, are aggressively metastatic, and exhibit a poor prognosis. The incidence of BP-carcinoids (TC and AC) in the US was 1.57 of 100,000 in 2003 (an unexplained and substantial increase over the last 30 years, approximately 6% per year). No curative treatment except for radical surgery (almost never feasible) exists. The slow-growing TC exhibit a fairly good prognosis ( approximately 88%, 5-year survival), whereas AC demonstrate a 5-year survival of approximately 50%, and the highly malignant LCNEC and SCLC5-year survival of 15% to 57% and <5%, respectively. This review provides a broad overview on BP-NETs and focuses on the evolution of the disease, general features, and current diagnostic and therapeutic options.

Targeting growth factors in lung cancer

Lung cancer causes more deaths than any other malignancy in the developed world. Advances in surgical techniques and chemotherapy/radiotherapy regimes have produced only minimal improvements in long-term survival. New therapeutic interventions are urgently required. Research has indicated that growth factor signaling may be an important novel target in lung cancer therapy. Preclinical studies have demonstrated the role of extracellular growth factors in lung cancer cell proliferation, metastasis, and resistance to cytotoxic therapy, and have elucidated the key molecular components of growth factor-signaling cascades. This has enabled the development of selective growth factor inhibitors, which have been evaluated in clinical trials and are now an accepted component of advanced lung cancer treatment. Further research is underway to improve the efficacy of this growth factor-targeted therapy. This article will outline the important aspects of this translational research indicating the growth factor-signaling pathways identified in lung cancer, clinical trials of anti-growth factor therapy, and potential future research directions.

Endothelin-1 enhances proliferation of lung cancer cells by increasing intracellular free Ca2+

Endothelin-1 (ET-1), the most potent vasoconstrictor, has been shown to be mitogenic in many tumor cells as well as in vascular cells. It was previously reported that the mRNA of ET-1 and endothelin receptors (ETRs) are expressed in lung cancer cells. However, their biological role in lung cancer remains to be explored. The purpose of this study was to determine whether ET-1 stimulates proliferation of the human lung adenocarcinoma cell SPC-A1 and probe its cellular mechanism. Reverse-transcription polymerase chain reaction and Western blot analysis showed that both the mRNA and protein of ET-1, ET A R and ET B R are expressed in SPC-A1 cells. Application of ET-1 at 10(-15)-10(-8) M caused a dose-dependent cell proliferation and an increase in intracellular free Ca2+ concentration ([Ca2+]i). This ET-1-induced cell proliferation and [Ca2+]i increase were completely abolished by BQ123, a selective ET A R antagonist, but not by BQ788, a selective ET B R antagonist. Furthermore, it was significantly reduced by U73122, a specific inhibitor of phospholipase C (PLC), but not by U73433, the structural isomer of U73122. Chelating extracellular Ca2+ or blocking voltage dependent calcium channels by nifedipine also significantly reduced the mitogenic effect of ET-1 and [Ca2+]i increase in SPC-A1 cells. These results indicate that ET-1 acts as an autocrine growth factor and enhances proliferation of SPC-A1 cells via activation of ET A R. The phosphoinositol/Ca2+ pathway and Ca2+ influx through voltage dependent Ca2+ channels activated by ET A R contribute to this process.

Neurotensin and growth of normal and neoplastic tissues

Neurotensin (NT) is a brain-gut tridecapeptide that functions as a neurotransmitter/neuromodulator in the central nervous system (CNS) and as an endocrine agent in the periphery. NT has numerous physiologic effects on multiple organs. This review will focus on the effects of NT as a trophic factor for normal and neoplastic tissues. In this regard, NT may act as an endocrine agent or, in some instances, in a paracrine and/or autocrine fashion. These effects appear to be mediated predominantly through the G protein-coupled high-affinity NT receptor. However, some of the trophic effects may also be through the other two receptor subtypes, particularly the NT receptor type 3, which belongs to a recently identified family of sorting receptors. The signaling pathways mediating the effects of NT are multiple but most appear to activate the ERK signaling pathway, which then activates downstream transcription factors, ultimately leading to proliferation. NT may be a useful agent to enhance the growth of normal tissues such as the small bowel mucosa during periods of gut disuse or disease and, finally, the selective targeting of NT receptor subtypes on certain cancers may offer a novel strategy in the armamentarium of cancer chemotherapeutics.

Radionuclide imaging of small-cell lung cancer (SCLC) using 99mTc-labeled neurotensin peptide 8-13

OBJECTIVES

To prepare 99m technetium (99mTc)-labeled neurotensin (NT) peptide and to evaluate the feasibility of imaging oncogene NT receptors overexpressed in human small-cell lung cancer (SCLC) cells.

METHODS

The NT analogue (Nalpha-His)Ac-NT(8-13) was synthesized such that histidine was attached at the N-terminus. The analogue was labeled with [99mTc(H2O)3(CO)3] at pH 7. 99mTc-(Nalpha-His)Ac-NT(8-13) in vitro stability was determined by challenging it with 100 times the molar excess of DTPA, human serum albumin (HSA) and cysteine. The affinity, 99mTc-(Nalpha-His)Ac-NT(8-13) binding to SCLC cell line NCI-H446, was studied in vitro. Biodistribution and imaging with 99mTc-(Nalpha-His)Ac-NT(8-13) were performed at 4 and 12 h postinjection, and tissue distribution and imaging after receptor blocking were carried out at 4 h in nude mice bearing human SCLC tumor. Blood clearance was determined in normal mice.

RESULTS

The affinity constant (Kd) of 99mTc-(Nalpha-His)Ac-NT(8-13) to SCLC cells was 0.56 nmol/L. When challenged with 100 times the molar excess of DTPA, HSA or cysteine, more than 97+/-1.8% radioactivity remained as 99mTc-(Nalpha-His)Ac-NT(8-13). Tumor-to-muscle ratio was 3.35+/-1.01 at 4 h and 4.20+/-1.35 at 12 h postinjection. The excretory route of 99mTc-(Nalpha-His)Ac-NT(8-13) was chiefly through the renal pathway. In the receptor-blocking group treated with unlabeled (Nalpha-His)Ac-NT(8-13), tumor-to-muscle ratio at 4 h was 1.25+/-0.55.

CONCLUSION

The results suggest that 99mTc-(Nalpha-His)Ac-NT(8-13) specifically binds to the SCLC cells and made 99mTc-(Nalpha-His)Ac-NT(8-13) a desirable compound for further studies in planar or SPECT imaging of oncogene receptors overexpressed in SCLC cells.

Roles for USF-2 in lung cancer proliferation and bronchial carcinogenesis

The upstream stimulatory factors USF-1 and USF-2 dimerize to regulate transcription through E-box motifs in target genes. Although widely expressed, they can mediate tissue-specific transcription and we previously reported that USF-2 can enhance transcription of arginine vasopressin, a neuropeptide growth factor in small cell lung cancer. Here we determine the expression and role of USF-2 in lung cancer subtypes and examine USF-2 distribution in the bronchial epithelium. For a panel of 12 cell lines and 10 frozen human tumour samples, immunoblotting demonstrated that USF-2 expression was more frequent and abundant in small cell lung cancer than in non-small cell lung cancer. An immunohistochemical study of 108 formalin-fixed and paraffin-embedded human samples was undertaken to localize USF-2 expression and included 44 small cell and 32 non-small cell lung cancers, and 32 samples with bronchial dysplasia. USF-2 was restricted to ciliated cells in normal bronchial epithelium, but was more strongly expressed in dysplastic epithelium (72%) and certain lung cancer types, including small cell lung cancer (71%), squamous cell carcinoma (69%) and a large cell neuroendocrine carcinoma, but was less common in adenocarcinoma (11%). In a small series, expression was assessed adjacent to positively staining tumours; in phenotypically normal bronchial tissues, USF-2 was more highly expressed at 1 cm than at 5 cm from the tumour. Transient USF-2 overexpression in non-small cell lung cancer cell lines significantly stimulated in vitro cell proliferation; this response was most apparent for NCI-H460 (p < 0.005), reducing the mean cell doubling time from 19 to 16 h. Dominant-negative USF-2 mutants had no significant effect on cell growth. Taken together, these data suggest that USF-2 represents a relatively early molecular marker for the development of bronchial dysplasia and non-adenocarcinoma lung cancer. USF may also play a role in bronchial carcinogenesis, perhaps through promoting cell proliferation, although the genes through which this is regulated remain to be determined.

Expression of V1A and GRP receptors leads to cellular transformation and increased sensitivity to substance-P analogue-induced growth inhibition

Small-cell lung cancer (SCLC) is a particularly aggressive cancer, which metastasises early. Despite initial sensitivity to radio- and chemo-therapy, it invariably relapses, so that the 2-year survival remains less than 5%. Neuropeptides particularly arginine vasopressin (AVP) and gastrin-releasing peptide (GRP) act as autocrine and paracrine growth factors and the expression of these and their receptors are a hallmark of the disease. Substance-P analogues including [D-Arg1,D-Phe5,D-Trp7,9,Leu11]-substance-P (SP-D) and [Arg6,D-Trp7,9,NmePhe8]-substance-P (6-11) (SP-G) inhibit the growth of SCLC cells by modulating neuropeptide signalling. We show that GRP and V1A receptors expression leads to the development of a transformed phenotype. Addition of neuropeptide provides some protection from etoposide-induced cytotoxicity. Receptor expression also leads to an increased sensitivity to substance-P analogue-induced growth inhibition. We show that SP-D and SP-G act as biased agonists at GRP and V1A receptors causing blockade of Gq-mediated Ca2+ release while directing signalling to activate ERK via a pertussis toxin-sensitive pathway. This is the first description of biased agonism at V1A receptors. This unique pharmacology governs the antiproliferative properties of these agents and highlights their potential therapeutic potential for the treatment of SCLC and particularly in tumours, which have developed resistance to chemotherapy.

Sensitive detection of small cell lung carcinoma cells by reverse transcriptase-polymerase chain reaction for prepro-gastrin-releasing peptide mRNA

BACKGROUND

Gastrin-releasing peptide (GRP) is an autocrine growth factor in patients with small cell lung carcinoma (SCLC). The authors developed a reverse transcriptase-polymerase chain reaction (RT-PCR) assay for the detection of SCLC cells in the peripheral blood and the pleural effusion using preproGRP mRNA as a target.

METHODS

The current study was conducted to determine the utility of preproGRP-specific nested RT-PCR on the peripheral blood, bone marrow, and pleural effusion samples from 32 patients with SCLC, 39 patients with non-small cell lung carcinoma (NSCLC), 28 patients with nonmalignant pulmonary disease, and 20 healthy volunteers. The internal primers were designed to amplify a 244-base pair PCR product, a sequence encompassing exon 1 and exon 2 by the nested RT-PCR assay.

RESULTS

Amplification of the preproGRP message was detected in SCLC cell lines (LU165, SBC1, SBC2, and SBC3) but not in other NSCLC cell lines (A549, ABC1, EBC1, and Oka-1). The SCLC cells (LU165) were detected in dilutions of tumor cells of up to 10(-7) in hematopoietic cells from healthy donors. The preproGRP mRNA was detected in 16 of 32 (50%) blood samples, 2 of 11 (18%) marrow samples, and in all 6 (100%) pleural effusion samples. Blood samples gave positive results in 11 of 19 (58%) patients with extensive disease compared with 5 of 13 (38%) patients with limited disease. In contrast, only 1 blood sample (2.6%) from a patient with lung adenocarcinoma gave a positive result among patients with NSCLC. No other samples of blood, bone marrow, and pleural effusion from patients with NSCLC and none of the blood samples from patients with nonmalignant diseases and healthy volunteers were positive.

CONCLUSIONS

The current RT-PCR approach may be a sensitive and specific assay to detect SCLC cells in circulating blood as well as in pleural effusions from SCLC patients.

Upstream stimulatory factor activates the vasopressin promoter via multiple motifs, including a non-canonical E-box

We have described previously a complex E-box enhancer (-147) of the vasopressin promoter in small-cell lung cancer (SCLC) extracts [Coulson, Fiskerstrand, Woll and Quinn, (1999) Biochem. J. 344, 961-970]. Upstream stimulatory factor (USF) heterodimers were one of the complexes binding to this site in vitro. We now report that USF overexpression in non-SCLC (NSCLC) cells can functionally activate vasopressin promoter-driven reporters that are otherwise inactive in this type of lung cancer cell. Site-directed mutagenesis and electrophoretic mobility-shift analysis demonstrate that although the -147 E-box contributes, none of the previously predicted E-boxes (-147, -135, -34) wholly account for this USF-mediated activation in NSCLC. 5' Deletion showed the key promoter region as -52 to +42; however, USF-2 binding was not reliant on the -34 E-box, but on a novel adjacent CACGGG non-canonical E-box at -42 (motif E). This mediated USF binding in both SCLC and USF-2-transfected NSCLC cells. Mutation of motif E or the non-canonical TATA box abolished activity, implying both are required for transcriptional initiation on overexpression of USF-2. Co-transfected dominant negative USF confirmed that binding was required through motif E for function, but that the classical activation domain of USF was not essential. USF-2 bound motif E with 10-fold lower affinity than the -147 E-box. In NSCLC, endogenous USF-2 expression is low, and this basal level appears to be insufficient to activate transcription of arginine vasopressin (AVP). In summary, we have demonstrated a novel mechanism for USF activation, which contributes to differential vasopressin expression in lung cancer.

Lung epithelial stem cells

This review concentrates on recent evidence about lung stem cell origins and plasticity. The range of potential cells which can repopulate the injured lung, classically the basal and mucous secretory cells of the trachea, the Clara cells of the bronchiole, and the type II pneumocyte of the alveolus, has been extended to include the mucus-gland duct cells of the trachea and bronchus. Some evidence suggests that there are variant Clara cells that lack cytochrome P-450 and so are spared toxic activation of xenobiotics, and may aid bronchiolar repopulation after injury, such as with naphthalene. There may even be involvement of the neuroepithelial bodies or cells in this, though the evidence is not yet conclusive. The search for a resident pulmonary multipotent cell for repopulating any lung epithelium has not yet been successful. The picture remains similar to earlier conclusions, in that the local stem or precursor cell is the most likely to contribute to local needs in times of tissue damage. There remains a major challenge for lung cancer treatment, where high-dose chemo- or radio-therapy may be hoped to promote the seeding and repair of lung parenchyma by circulating bone marrow stem cells, as seen in liver models. Patient survival rates do not yet suggest that this occurs to any great extent, but this remains to be shown formally. The effects of prior fibrosis and tumour necrosis are probably confounding factors in this lack of rescue.