Recombinant C-terminal fragments of the gastrin-releasing peptide precursor are bioactive

A fluorescence-based lateral flow immunoassay using AIEgen-encapsulated nanoparticles to rapidly and sensitively detect pro-gastrin-releasing peptide

A fluorescence lateral flow immunoassay (F-LFIA) is presented using nanoparticles with encapsulated molecules whose emission is caused by aggregation as the fluorescent label to quantitatively detect gastrin-releasing peptide precursor (proGRP) in serum. The detection system was optimized to achieve a broad linear detection range of 10 ~ 5000 pg/mL and a detection limit of 6 pg/mL for F-LFIA. The proposed method exhibited good sensitivity, specificity, and reproducibility. The performance and applicability of the F-LFIA were evaluated in the analysis of 183 human serum samples, and the results were strongly correlated with those of the electrochemiluminescence immunoassay. The proposed F-LFIA can serve as a precise and rapid detection method to detect proGRP and has potential for the early diagnosis of small-cell lung cancer (SCLC).

Selective application of neuroendocrine markers in the diagnosis and treatment of small cell lung cancer

AIMS

Here, we explored the potential application and selection of neuroendocrine biomarkers in the diagnosis and treatment of small cell lung cancer.

METHODS

We retrospectively analyzed 118 patients with small cell lung cancer (SCLC), 166 patients with non-small cell lung cancer (NSCLC), 33 patients with benign lung disease (BLD), and 200 healthy individuals admitted to Zhejiang Provincial People's Hospital between January 1, 2015 and May 31, 2019. All the patients were newly diagnosed with either SCLC, NSCLC, or BLD and previously untreated. Peripheral blood levels of ProGRP, NSE, CEA, and CYFRA21-1 were analyzed during the follow-up treatment, and 2-fold upper limit of reference intervals were defined as effective elevation. We used paired results to analyze the diagnostic efficiency of proGRP and NSE on SCLC.

RESULTS

In the 118 SCLC patients, proGRP levels were significantly higher compared with NSE levels. The diagnostic efficiencies of NSE and ProGRP for SCLC were 0.8554 and 0.9053, respectively. The combined diagnostic efficiency (0.9426) was higher relative to NSE, but there was no significant difference compared with proGRP. The effective elevation rate of proGRP was 45.3% higher than that of NSE in the limited stage of SCLC. In the extensive disease of SCLC patients, 70.7% cases had more than 10-fold increase in proGRP value, whereas 56.9% cases had less than 5-fold increase in NSE value. Compared with pre-treatment, the median concentrations of proGRP increased by 204.0% higher than that of NSE (71.3%) in the progressive group. Besides, the dynamic change in imaging characteristics and tumor size had a strong correlation with the levels of proGRP.

SIGNIFICANCE

ProGRP is a reliable neuroendocrine biomarker in SCLC. The effective elevation of proGRP has a potential diagnostic and efficacy value in the evaluation of SCLC. However, the combined detection of proGRP and NSE does not significantly improve the diagnosis of lung cancer.

Pro-gastrin-releasing peptide (ProGRP) as a biomarker in small-cell lung cancer diagnosis, monitoring and evaluation of treatment response

Lung cancer belongs to malignant tumors that possess the highest rates of morbidity and mortality in the world. A number of morphological, biological and clinical features justify the distinction of small-cell carcinoma with respect to the other histological types of lung cancer. The predominant neuroendocrine phenotype is critical for the selection of biomarkers used in diagnostics, monitoring and evaluation of treatment response; early onset relapses in patients with small-cell lung cancer (SCLC) and the evaluation of their prognosis. Although for a long time the neuron-specific enolase (NSE) was considered to be the marker of choice for this tumor, it is now increasingly important to pay attention to concentrations of pro-gastrin-releasing peptide (ProGRP). The results of this marker have been implicated in the differential diagnosis of non-small lung cancer and SCLC, chemotherapy and radiotherapy monitoring as well as evaluation of treatment response. The subject of this series of studies is to determine the usefulness of ProGRP in the evaluation of patients’ prognosis and its predictive value. The current aim for the optimization of the effectiveness of biochemical diagnostics of SCLC is recommended by complementary ProGRP and NSE studies. The present work is a summary of the latest reports regarding diagnostic utility of these markers in SCLC.

Identification of binding sites for C-terminal pro-gastrin-releasing peptide (GRP)-derived peptides in renal cell carcinoma: a potential target for future therapy

OBJECTIVE

To determine the expression and biology of the neuroendocrine growth factor gastrin-releasing peptide (GRP) and other proGRP-derived peptides in renal cancer.

MATERIALS AND METHODS

Receptor binding studies, enzyme-linked immunosorbent assay (ELISA) and radioimmunoassay, were used to quantitate the presence of proGRP-derived peptide receptors and their ligands in renal cancer cell lines and human renal cancers. Biological activity of proGRP peptides was confirmed with proliferation, migration, and extracellular-signal-regulated kinases 1 and 2 (ERK1/2) activation assays in vitro. In vivo, ACHN renal cancer xenografts were treated with proGRP-derived peptides to assess tumour size and necrosis. hypoxia-inducible factor 1α (HIF1α) and vascular endothelial growth factor (VEGF) expression were investigated with Western blotting and ELISA respectively, to determine the possible contribution of the proGRP peptides to tumour viability.

RESULTS

In ACHN cells that expressed both proGRP- and GRP-receptors, the expression of proGRP binding sites was 80-fold greater than the GRP-receptor (GRPR). C-terminal proGRP-derived peptides stimulated the activation of ERK1/2, but with a different time course to GRP, consistent with the suggestion that these peptides may have unique cellular functions. Both GRP and proGRP47-68 stimulated proliferation and migration of ACHN cells in vitro, but only GRP reduced the extent of tumour necrosis in ACHN xenografts. GRP, but not proGRP47-68, was able to induce HIF1α and VEGF expression in ACHN cells. This may account in part for the reduction in necrosis after GRP treatment. C-terminal proGRP-derived peptides were present in all three renal cancer cell lines and a panel of human renal cancers, but mature amidated GRP was absent.

CONCLUSION

C-terminal proGRP peptides are more abundant in renal cancers and their cell lines than the more extensively studied amidated peptide, GRP. These results suggest that C-terminal proGRP-derived peptides may be a better target for novel renal cancer treatments.

Pro-GRP-derived peptides are expressed in colorectal cancer cells and tumors and are biologically active in vivo

Amidated gastrin-releasing peptide (GRP) is the prototypical autocrine growth factor. Nonamidated peptides derived from the C terminus of pro-GRP are also biologically active in colorectal cancer (CRC) cell lines in vitro, via a receptor distinct from the GRP receptor. The aims of this study were to measure the amounts of pro-GRP-derived peptides in human CRC cell lines and tumors, characterize the immunoreactive peptide, and investigate its effect on proliferation in vitro and in vivo. Pro-GRP-derived peptides were quantitated by region-specific ELISA in extracts of five human CRC cell lines and 20 tumors. The immunoreactive material was purified by HPLC and its mass and sequence established by mass spectrometry. The concentration of GRPamide was determined by RIA. Proliferation of DLD-1 cells and murine gastrointestinal mucosa was measured by [(3)H]-thymidine incorporation and mitotic index, respectively. In CRC cell extracts, ELISA for pro-GRP-derived peptides detected 3-152 fmol/10(6) cells. The immunoreactive peptide was purified and identified as pro-GRP42-98. Resected stage III tumors contained significantly less pro-GRP immunoreactivity than stage II tumors, and no amidated GRP was detected in cell lines or tumors. Stable transfection of DLD-1 cells with pro-GRP short hairpin RNA, or treatment with a monoclonal anti-pro-GRP antibody, significantly reduced proliferation. Pro-GRP42-98, pro-GRP47-68, and pro-GRP80-97 significantly stimulated mitosis in colonic, but not small intestinal, mucosa of 10-wk-old mice. We conclude that nonamidated peptides derived from the C terminus of pro-GRP are expressed in significant quantities in CRC cell lines and tumors and stimulate the proliferation of CRC cells and of normal colonic mucosa. Such peptides are attractive targets for novel CRC therapies.

Isolation, identification and biological activity of gastrin-releasing peptide 1-46 (oGRP 1-46), the primary GRP gene-derived peptide product of the pregnant ovine endometrium

We have previously demonstrated that pregnant ovine endometrium expresses the gastrin-releasing peptide (GRP) gene at a high level following conceptus implantation. Here we report the isolation, characterization and biological activity of ovine GRP 1-46, the primary product of this gene in the pregnant endometrium. Full thickness 125-140-day pregnant sheep uterus (term is 145 day) was homogenized in 80% acetonitrile/2% trifluoroacetic acid (1:7 ACN/TFA), concentrated on reverse-phase C18 cartridges and chromatographed successively on gel filtration (Sephadex G-50) and reverse-phase HPLC (C18 muBondapak). Purification was monitored by RIA. Purified GRP peptide was analysed by mass spectrometry giving a major mass ion at 4963 which corresponds exactly to GRP 1-46. Other mass ions from pro-GRP did not contain a biologically active N-terminus or antigenic determinant. Proteolytic cleavage of pro-GRP to give rise to GRP(1-46) would require preferential cleavage at the Glu-Glu bond by a Glu-C2-like enzyme, rather than the trypsin-like and C-terminal amidation enzymes (PAM) that produce GRP(18-27) and GRP(1-27) in other tissues. GRP 1-46 was synthesized and receptor binding and biological activity tested on a range of rodent and human cell lines that express GRP-related receptors GRPR, NMBR and BRS3. GRP 1-46 bound GRPR and NMBR with low affinity, and mobilized inositol phosphate in cell lines expressing the GRPR and NMBR, but not BRS-3. This study describes a new processed product of the GRP gene, GRP 1-46, which is highly expressed in the pregnant sheep endometrium and which acts as a weak agonist at the GRPR and NMBR.

Peptide processing and biology in human disease

PURPOSE OF REVIEW

To describe recent advances in the processing of gastrointestinal hormones, and the consequences for human disease of mutations in the enzymes involved.

RECENT FINDINGS

Although gastrointestinal prohormones were long regarded as devoid of biological activity, recent data indicate that the prohormones for both gastrin and gastrin-releasing peptide are bioactive, through different receptors from the mature hormones. Mutations in the family of prohormone convertases responsible for the initial steps in the processing of gastrointestinal hormones are associated with several different pathophysiological conditions in humans.

SUMMARY

Human mutational studies, when taken together with the phenotypes observed in mice deficient in the prohormone convertases, emphasize the crucial importance of the processing enzymes in mammalian biology. Although the phenotypes may often be ascribed to defective production of a mature hormone or growth factor, the recognition that the precursors are independently bioactive suggests that the increased precursor concentrations may also contribute to the symptoms. The observation that the precursors often act through different receptors from the mature hormones may permit the development of precursor-selective antagonists for therapeutic use.

Gastrin-releasing peptide: different forms, different functions

All forms of the neuropeptide gastrin-releasing peptide (GRP) are derived from the precursor proGRP1-125. Amidated GRP18-27, which together with amidated GRP1-27 was long thought to be the only biologically relevant product of the GRP gene, is involved in a multitude of physiological functions and acts as a mitogen, morphogen, and proangiogenic factor in certain cancers. Recently, GRP has been implicated in several psychiatric conditions, in the maintenance of circadian rhythm, in spinal transmission of the itch sensation, and in inflammation and wound repair. The actions of GRP are mediated by the GRP receptor. Over the last decade, nonamidated peptides derived from proGRP, such as the glycine-extended form GRP18-28 and recombinant and synthetic fragments from proGRP31-125, have been shown to be biologically active in a range of tissues and in cancer cell lines. While GRP18-28 acts via the GRP receptor, the identity of the receptor for proGRP31-125 and its fragments has not yet been established. Nonamidated fragments are also present in normal tissues and in various cancers. In fact, proGRP31-98 is the most sensitive serum biomarker in patients with small cell lung cancer and is a significant predictor of poor survival in patients with advanced prostate cancer.

Gastrin-releasing peptide (GRP) in the ovine uterus: regulation by interferon tau and progesterone

Gastrin-releasing peptide (GRP) is abundantly expressed by endometrial glands of the ovine uterus and processed into different bioactive peptides, including GRP1-27, GRP18-27, and a C-terminus, that affect cell proliferation and migration. However, little information is available concerning the hormonal regulation of endometrial GRP and expression of GRP receptors in the ovine endometrium and conceptus. These studies determined the effects of pregnancy, progesterone (P4), interferon tau (IFNT), placental lactogen (CSH1), and growth hormone (GH) on expression of GRP in the endometrium and GRP receptors (GRPR, NMBR, BRS3) in the endometrium, conceptus, and placenta. In pregnant ewes, GRP mRNA and protein were first detected predominantly in endometrial glands after Day 10 and were abundant from Days 18 through 120 of gestation. Treatment with IFNT and progesterone but not CSH1 or GH stimulated GRP expression in the endometrial glands. Western blot analyses identified proGRP in uterine luminal fluid and allantoic fluid from Day 80 unilateral pregnant ewes but not in uterine luminal fluid of either cyclic or early pregnant ewes. GRPR mRNA was very low in the Day 18 conceptus and undetectable in the endometrium and placenta; NMBR and BRS3 mRNAs were undetectable in ovine uteroplacental tissues. Collectively, the present studies validate GRP as a novel IFNT-stimulated gene in the glands of the ovine uterus, revealed that IFNT induction of GRP is dependent on P4, and found that exposure of the ovine uterus to P4 for 20 days induces GRP expression in endometrial glands.

International Union of Pharmacology. LXVIII. Mammalian bombesin receptors: nomenclature, distribution, pharmacology, signaling, and functions in normal and disease states

The mammalian bombesin receptor family comprises three G protein-coupled heptahelical receptors: the neuromedin B (NMB) receptor (BB(1)), the gastrin-releasing peptide (GRP) receptor (BB(2)), and the orphan receptor bombesin receptor subtype 3 (BRS-3) (BB(3)). Each receptor is widely distributed, especially in the gastrointestinal (GI) tract and central nervous system (CNS), and the receptors have a large range of effects in both normal physiology and pathophysiological conditions. The mammalian bombesin peptides, GRP and NMB, demonstrate a broad spectrum of pharmacological/biological responses. GRP stimulates smooth muscle contraction and GI motility, release of numerous GI hormones/neurotransmitters, and secretion and/or hormone release from the pancreas, stomach, colon, and numerous endocrine organs and has potent effects on immune cells, potent growth effects on both normal tissues and tumors, potent CNS effects, including regulation of circadian rhythm, thermoregulation; anxiety/fear responses, food intake, and numerous CNS effects on the GI tract as well as the spinal transmission of chronic pruritus. NMB causes contraction of smooth muscle, has growth effects in various tissues, has CNS effects, including effects on feeding and thermoregulation, regulates thyroid-stimulating hormone release, stimulates various CNS neurons, has behavioral effects, and has effects on spinal sensory transmission. GRP, and to a lesser extent NMB, affects growth and/or differentiation of various human tumors, including colon, prostate, lung, and some gynecologic cancers. Knockout studies show that BB(3) has important effects in energy balance, glucose homeostasis, control of body weight, lung development and response to injury, tumor growth, and perhaps GI motility. This review summarizes advances in our understanding of the biology/pharmacology of these receptors, including their classification, structure, pharmacology, physiology, and role in pathophysiological conditions.

Bombesin-related peptides and their receptors: recent advances in their role in physiology and disease states

PURPOSE OF REVIEW

Mammalian bombesin-related peptides, gastrin-releasing peptide and neuromedin B actions are mediated by two receptors (BB1-receptor, BB2-receptor), which are closely related to the orphan receptor BRS-3 (BB3-receptor). The purpose of this review is to highlight advances in the understanding of these peptides in physiology/disease states.

RECENT FINDINGS

Pharmacologic/receptor-knockout studies show involvement of these receptors in a number of new processes/diseases. Neuromedin B/BB1-receptor is an important physiological regulator of pituitary-thyroid function; in mediating behavior, especially feas/anxiety; in mediating satiety through different cascades than gastrin-releasing peptide/BB2 receptors and for its autocrine tumor-growth effects. Gastrin-releasing peptide/BB2-receptor plays important roles in mediating signals for pruritus, lung development/injury, small intestinal mucosal defense, and central nervous system processes such as learning/memory. The signaling mechanisms of its potent growth effects are being elucidated and their possible therapeutic targets identified. BB3-receptor knockout mice provided insights for their obesity/glucose intolerance and demonstrated that this receptor may be important in the lung response to injury, tumor growth and gastrointestinal motility. Each receptor is frequently overexpressed in human tumors and has potent growth effects. This effect is being explored to develop new antitumor treatments, such as bombesin-receptor ligands conjugated to cytotoxic agents.

SUMMARY

This receptor family is involved in an increasing number of central nervous system/peripheral processes physiologically and in disease states, and increased understanding of its role may lead to novel treatments.