Galanin and galanin receptor expression in neuroblastic tumours: correlation with their differentiation status

A signature based on five immune-related genes to predict the survival and immune characteristics of neuroblastoma

BACKGROUND

MYCN amplification (MNA) has been proved to be related to poor prognosis in neuroblastoma (NBL), but the MYCN-related immune signatures and genes remain unclear.

METHODS

Enrichment analysis was used to identify the significant enrichment pathways of differentially expressed immune-related genes (DEIRGs). Weight gene coexpression network analysis (WGCNA) was applied to reveal the correlation between these DEIRGs and MYCN status. Univariate and multivariate Cox analyses were used to construct risk model. The relevant fractions of immune cells were evaluated by CIBERSORT and single-sample gene set enrichment analysis (ssGSEA).

RESULTS

Five genes, including CHGA, PTGER1, SHC3, PLXNC1, and TRIM55 were enrolled into the risk model. Kaplan-Meier survival analysis and receiver operating characteristic (ROC) curve showed that our model performed well in predicting the outcomes of NBL (3-years AUC = 0.720, 5-year AUC = 0.775, 10-years AUC = 0.782), which has been validated in the GSE49711 dataset and the E-MTAB-8248 dataset. By comparing with the tumor immune dysfunction and exclusion (TIDE) and tumor inflammation signature (TIS), we further proved that our model is reliable. Univariate and multivariate Cox regression analyses indicated that the risk score, age, and MYCN can serve as independent prognostic factors in the E-MATB-8248. Functional enrichment analysis showed the DEIRGs were enriched in leukocyte adhesion-related signaling pathways. Gene set enrichment analysis (GSEA) revealed the significantly enriched pathways of the five MYCN-related DEIRGs. The risk score was negatively correlated with the immune checkpoint CD274 (PD-L1) but no significant difference with the TMB. We also confirmed the prognostic value of our model in predicting immunotherapeutics.

CONCLUSION

We constructed and verified a signature based on DEIRG that related to MNA and predicted the survival of NBL based on relevant immune signatures. These findings could provide help for predicting prognosis and developing immunotherapy in NBL.

The Galaninergic System: A Target for Cancer Treatment

Simple Summary

Peptidergic systems play an important role in cancer progression. The galaninergic system (the peptide galanin and its receptors: galanin 1, 2 and 3) is involved in tumorigenesis, the invasion and migration of tumor cells and angiogenesis and it has been correlated with tumor stage/subtypes, metastasis and recurrence rate in many types of cancer. Galanin exerts a dual action in tumor cells: a proliferative or an antiproliferative effect depending on the galanin receptor involved in these mechanisms. Galanin receptors could be used in certain tumors as therapeutic targets and diagnostic markers for treatment, prognosis and surgical outcome. This review shows the importance of the galaninergic system in the development of tumors and suggests future promising clinical antitumor applications using galanin agonists or antagonists.

Abstract

The aim of this review is to show the involvement of the galaninergic system in neuroendocrine (phaeochromocytomas, insulinomas, neuroblastic tumors, pituitary tumors, small-cell lung cancer) and non-neuroendocrine (gastric cancer, colorectal cancer, head and neck squamous cell carcinoma, glioma) tumors. The galaninergic system is involved in tumorigenesis, invasion/migration of tumor cells and angiogenesis, and this system has been correlated with tumor size/stage/subtypes, metastasis and recurrence rate. In the galaninergic system, epigenetic mechanisms have been related with carcinogenesis and recurrence rate. Galanin (GAL) exerts both proliferative and antiproliferative actions in tumor cells. GAL receptors (GALRs) mediate different signal transduction pathways and actions, depending on the particular G protein involved and the tumor cell type. In general, the activation of GAL₁R promoted an antiproliferative effect, whereas the activation of GAL₂R induced antiproliferative or proliferative actions. GALRs could be used in certain tumors as therapeutic targets and diagnostic markers for treatment, prognosis and surgical outcome. The current data show the importance of the galaninergic system in the development of certain tumors and suggest future potential clinical antitumor applications using GAL agonists or antagonists.

Screening potential immune signatures for early-stage basal-like/triple-negative breast cancer

Background

Breast cancer (BC) is a highly heterogeneous disease. Among the BC molecular subtypes, basal-like/triple-negative BC (TNBC) is characterized by a high propensity for relatively early metastases and a lack of available endocrine and targeted therapies. Therefore, this study aimed to discover potential signatures for predicting the immune response in early-stage basal-like/triple-negative BC.

Method

A total of 86 cases of early-stage TNBC from the TCGA and 459 cases of normal breast tissue from GTEx were enrolled and analyzed to screen out differentially expressed genes (DEGs). Then, the prognostic effect and tumor immune cell infiltration relationship with the basal-like-specific DEGs were also evaluated.

Results

A total of 1556 DEGs, including 929 upregulated genes and 627 downregulated genes, were screened in early-stage basal-like BC. Two prognosis-associated DEGs, GAL and TTC36, were finally found to be basal-like BC specific. However, only GAL was significantly correlated with tumor immune-infiltrating cells, especially CD8⁺ T cells. The expressions of GAL and TTC36 were revalidated by using the GEO dataset.

Conclusion

GAL might be an immune signature for the response to immune checkpoint therapy in early basal-like/triple-negative BC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-022-02683-2.

Galanin System in Human Glioma and Pituitary Adenoma

Expression of neuropeptides and their corresponding receptors has been demonstrated in different cancer types, where they can play a role in tumor cell growth, invasion, and migration. Human galanin (GAL) is a 30-amino-acid regulatory neuropeptide which acts through three G protein-coupled receptors, GAL₁-R, GAL₂-R, and GAL₃-R that differ in their signal transduction pathways. GAL and galanin receptors (GALRs) are expressed by different tumors, and direct involvement of GAL in tumorigenesis has been shown. Despite its strong expression in the central nervous system (CNS), the role of GAL in CNS tumors has not been extensively studied. To date, GAL peptide expression, GAL receptor binding and mRNA expression have been reported in glioma, meningioma, and pituitary adenoma. However, data on the cellular distribution of GALRs are sparse. The aim of the present study was to examine the expression of GAL and GALRs in different brain tumors by immunohistochemistry. Anterior pituitary gland (n = 7), pituitary adenoma (n = 9) and glioma of different WHO grades I-IV (n = 55) were analyzed for the expression of GAL and the three GALRs with antibodies recently extensively validated for specificity. While high focal GAL immunoreactivity was detected in up to 40% of cells in the anterior pituitary gland samples, only one pituitary adenoma showed focal GAL expression, at a low level. In the anterior pituitary, GAL₁-R and GAL₃-R protein expression was observed in up to 15% of cells, whereas receptor expression was not detected in pituitary adenoma. In glioma, diffuse and focal GAL staining was noticed in the majority of cases. GAL₁-R was observed in eight out of nine glioma subtypes. GAL₂-R immunoreactivity was not detected in glioma and pituitary adenoma, while GAL₃-R expression was significantly associated to high-grade glioma (WHO grade IV). Most interestingly, expression of GAL and GALRs was observed in tumor-infiltrating immune cells, including neutrophils and glioma-associated macrophages/microglia. The presence of GALRs on tumor-associated immune cells, especially macrophages, indicates that GAL signaling contributes to homeostasis of the tumor microenvironment. Thus, our data indicate that GAL signaling in tumor-supportive myeloid cells could be a novel therapeutic target.

Physiology, signaling, and pharmacology of galanin peptides and receptors: three decades of emerging diversity

Galanin was first identified 30 years ago as a "classic neuropeptide," with actions primarily as a modulator of neurotransmission in the brain and peripheral nervous system. Other structurally-related peptides-galanin-like peptide and alarin-with diverse biologic actions in brain and other tissues have since been identified, although, unlike galanin, their cognate receptors are currently unknown. Over the last two decades, in addition to many neuronal actions, a number of nonneuronal actions of galanin and other galanin family peptides have been described. These include actions associated with neural stem cells, nonneuronal cells in the brain such as glia, endocrine functions, effects on metabolism, energy homeostasis, and paracrine effects in bone. Substantial new data also indicate an emerging role for galanin in innate immunity, inflammation, and cancer. Galanin has been shown to regulate its numerous physiologic and pathophysiological processes through interactions with three G protein-coupled receptors, GAL1, GAL2, and GAL3, and signaling via multiple transduction pathways, including inhibition of cAMP/PKA (GAL1, GAL3) and stimulation of phospholipase C (GAL2). In this review, we emphasize the importance of novel galanin receptor-specific agonists and antagonists. Also, other approaches, including new transgenic mouse lines (such as a recently characterized GAL3 knockout mouse) represent, in combination with viral-based techniques, critical tools required to better evaluate galanin system physiology. These in turn will help identify potential targets of the galanin/galanin-receptor systems in a diverse range of human diseases, including pain, mood disorders, epilepsy, neurodegenerative conditions, diabetes, and cancer.

Galanin plays an important role in cancer invasiveness and is associated with poor prognosis in stage II colorectal cancer

Reliable predictors of tumor recurrence for patients with stage II colorectal cancer (CRC) are needed to select patients who should receive adjuvant chemotherapy. Although galanin (GAL) is expressed in several malignant tumors and is associated with cell proliferation and tumor growth, the prognostic value of GAL expression in CRC is poorly understood. We compared GAL expression between 56 patients with stage II and III CRC who developed tumor recurrences and 56 patients who did not. The clinical and prognostic significance of GAL expression was examined using our data and independent public datasets. We also analyzed the influence of GAL expression on the proliferation and invasive activity of CRC cells. Higher expression of GAL was associated with tumor recurrence among the CRC patients (P<0.001). Stage II CRC patients who presented with high expression levels of GAL had significantly poorer prognosis than those with low expression levels of GAL [5-year overall survival: hazard ratio (HR), 7.31; 95% confidence interval (CI), 2.38–24.04; P<0.001; 5-year recurrence-free survival: HR, 3.99; 95% CI, 1.61–9.44; P=0.004], but there was no association between GAL expression and survival in stage III CRC patients. These findings were supported by analysis of two public datasets. Functionally, siRNA-mediated silencing of GAL resulted in a significant decrease in the proliferative and invasive activities of CRC cells. In conclusion, high expression of GAL is associated with poor prognosis of stage II CRC patients and GAL expression may be related to the aggressive behavior of CRC.

Clinical significance of serum biomarkers in pediatric solid mediastinal and abdominal tumors

Childhood cancer is the leading cause of death by disease among U.S. children between infancy and age 15. Despite successes in treating solid tumors such as Wilms tumor, disappointments in the outcomes of high-risk solid tumors like neuroblastoma have precipitated efforts towards the early and accurate detection of these malignancies. This review summarizes available solid tumor serum biomarkers with a special focus on mediastinal and abdominal cancers in children.

Galanin systems and ischemia: peptide and receptor plasticity in neurons and oligodendroglial precursors

Cerebral cortex contains few if any galanin neurons, but receives galanin-ergic inputs from subcortical areas. Apart from our earlier study on the response to cortical spreading depression, little is known about the presence and function of galanin in normal or injured cortex and to gain more insight into its possible roles, we investigated the temporal effects of focal ischemia on the expression of galanin and galanin receptors (GalRs). Focal ischemia induced in the rat by unilateral middle cerebral artery occlusion increased galanin and GalR1 mRNAs in penumbral/undamaged areas on the first and second day post-ischemia, while increased GalR2 mRNA was observed in the same regions only on the second day. Immunohistochemical studies revealed galanin immunoreactive neurons in the frontal/ cingulate cortex and abundant galanin-immunoreactivity in nerve axons/fibres within the penumbral areas, between the third and the seventh day after ischemia. Galanin mRNA and immunoreactivity was also increased in a population of small cells thought to be NG2-positive oligodendrocyte precursors. Up-regulation of galanin and GalRs in various cell populations following severe ischemic injury further demonstrates the marked plasticity of galanin and GalR1/2 expression after brain injury, and together with data reported elsewhere in this volume, suggests a functional role for galanin signalling in such pathophysiological conditions.

The galanin system in cancer

Many tumours of neuroendocrine origin, and also an increasing number of non-neuroendocrine cancers, have been shown to express neuropeptides and/or their corresponding receptors. These peptides and receptors represent the molecular basis for in vivo diagnostic or therapeutic targeting of cancer with radiolabelled or cytotoxic peptide analogues. Galanin is a classical neuropeptide that functions in diverse physiological processes such as food intake, nociception, and blood pressure regulation, and it can also act as a growth factor for neurons. Expression of galanin peptide has been detected in pheochromocytoma, pituitary adenoma, neuroblastic tumours, gastrointestinal cancer, squamous cell carcinoma, brain tumours, melanoma, breast cancer and embryonal carcinoma. In several cancers and tumour cell lines expression of galanin receptors--three are known (GalR1, 2 and 3)--has been shown as well. Expression of peptide or receptors has been correlated with tumour stage or subtypes of pituitary adenoma, neuroblastic tumours, colon carcinoma and squamous cell carcinoma. Galanin treatment has tumour-reducing effects in murine models of gastrointestinal cancer, whereas in animal experiments on adenoma formation, galanin seems to act as a growth factor, promoting both proliferation and tumour formation. In cell culture experiments on tumour cell lines, galanin has shown growth promoting or inhibiting effects. Activation of GalR1 is generally anti-proliferative, whereas activation of GalR2 can have pro- or anti-proliferative effects. Therefore, galanin and its receptors are promising targets for diagnosis and treatment of several types of tumours.

Galanin is up-regulated in colon adenocarcinoma

The early diagnosis of colorectal cancer and the early detection of recurrence are central to effective treatment, as prognosis is directly related to the stage of the disease. When colorectal cancer is diagnosed at an early, localized stage, 5-year survival is 90%. There is substantial interest in the identification of circulating human tumor-derived proteins in serum for the purposes of early cancer diagnosis. We have implemented an approach based on the analysis of microarray data for the identification of tumor proteins that may have utility as biomarkers in colon cancer. Expression analysis of microarray data obtained from a variety of 290 tumors and normal tissues revealed that galanin was maximally expressed in colon cancer. These findings were corroborated by real-time quantitative PCR, in which the colon cancer cell lines LOVO, HCT15, SW480, and SW620 cell showed significantly higher levels of galanin expression than did noncolon cancer cell lines. To evaluate galanin as a potential biomarker of colon cancer, a preliminary "training" set of serum from 40 healthy donors and 55 colon cancer patients was analyzed by ELISA. The data pattern was confirmed by an independent set of 90 masked serum samples: 24 from healthy donors and 66 from colon cancer patients. This result yielded a sensitivity of 69.7% [95% confidence interval (95% CI), 57.1-80.4], specificity of 75.0% (95% CI, 53.3-90.2), and positive predictive value of 88.5% (95% CI, 76.6-95.7). The galanin expression level was significantly increased with tumor size and tumor stage. These findings justify a prospective assessment of serum galanin protein as a screening tool for colon cancer.

Galanin decreases proliferation of PC12 cells and induces apoptosis via its subtype 2 receptor (GalR2)

Galanin is a neuropeptide with a wide range of effects in the nervous and endocrine systems, mediated through three G protein-coupled receptor subtypes (GalR1-3). Interestingly, galanin and its receptors are also expressed in certain tumors. Here we studied the effects of galanin in rat pheochromocytoma (PC12) cells stably transfected with GFP-tagged GalR2. Galanin at 100 nM inhibited cell proliferation in both nontransfected and transfected cells. Conversly, both galanin and the GalR2(R3)-agonist AR-M1896 induced caspase-dependent apoptotic cell death only in GalR2-transfected cells. Western-blot analyses of downstream mediators of the G(q/11)-type G protein showed down-regulation of pAkt and pBad in galanin-exposed transfected cells. Also, the specific PI3 kinase inhibitor LY-294002 increased the level of pBad and decreased activation of caspases. In addition, p21(cip1) levels were up-regulated in galanin-exposed PC12 cells and down-regulated in galanin-exposed GalR2-transfected cells. In agreement, FACS analyses of galanin exposed cells showed occurrence of cell cycle arrest in PC12 cells and cell death in transfected cells. Finally, as shown with real-time PCR, galanin and its receptors were expressed at very high levels in human pheochromocytoma tissues as compared with normal adrenal medulla. These findings point to GalR2 as a possible target for therapeuthic interventions in pheochromocytoma.

Effects of bilateral adrenalectomy on systemic kainate-induced activation of the nucleus of the solitary tract. Regulation of blood pressure and local neurotransmitters

Glutamatergic transmission through metabotropic and ionotropic receptors, including kainate receptors, plays an important role in the nucleus of the solitary tract (NTS) functions. Glutamate system may interact with several other neurotransmitter systems which might also be influenced by steroid hormones. In the present study we analyzed the ability of systemic kainate to stimulate rat NTS neurons, which was evaluated by c-Fos as a marker of neuronal activation, and also to change the levels of NTS neurotransmitters such as GABA, NPY, CGRP, GAL, NT and NO by means of quantitative immunohistichemistry combined with image analysis. The analysis was also performed in adrenalectomized and kainate stimulated rats in order to evaluate a possible role of adrenal hormones on NTS neurotransmission. Male Wistar rats (3 month-old) were used in the present study. A group of 15 rats was submitted either to bilateral adrenalectomy or sham operation. Forty-eight hours after the surgeries, adrenalectomized rats received a single intraperitoneal injection of kainate (12 mg/kg) and the sham-operated rats were injected either with saline or kainate and sacrificed 8 hours later. The same experimental design was applied in a group of rats in order to register the arterial blood pressure. Systemic kainate decreased the basal values of mean arterial blood pressure (35%) and heart rate (22%) of sham-operated rats, reduction that were maintained in adrenalectomized rats. Kainate triggered a marked elevation of c-Fos positive neurons in the NTS which was 54% counteracted by adrenalectomy. The kainate activated NTS showed changes in the immunoreactive levels of GABA (143% of elevation) and NPY (36% of decrease), which were not modified by previous ablation of adrenal glands. Modulation in the levels of CGRP, GAL and NT immunoreactivities were only observed after kainate in the adrenalectomized rats. Treatments did not alter NOS labeling. It is possible that modulatory function among neurotransmitter systems in the NTS might be influenced by steroid hormones and the implications for central regulation of blood pressure or other visceral regulatory mechanisms control should be further investigated.

Novel peptides secreted from human neuroblastoma: useful clinical tools?

BACKGROUND

Differentially expressed neuroblastoma (NB) proteins are vital for the development of new diagnostics and therapeutics. For example, secretory NB peptides (neuron-specific enolase and chromogranins) are clinically useful. We investigated polypeptide secretion by employing proteomic technologies to analyze proteins released from cultured NB cells.

METHODS

Neuroblastoma cell lines (SK-N-AS, SK-N-DZ, and SK-N-FI) were grown in serum-free media. Conditioned media from each cell line was analyzed for secreted proteins by 2-dimensional polyacrylamide gel electrophoresis. Selected polypeptides were identified by liquid chromatography-linked tandem mass spectrometry.

RESULTS

We identified 5 polypeptides that were secreted or shed by NB. Ubiquitin, beta2-microglobulin, insulin-like growth factor binding protein-2, superoxide dismutase (copper and zinc), and heat shock cognate 70-kd proteins were secreted from NB cells, as compared with control media. Elevated levels of these proteins have been described in serum/tissues under intracellular stress and malignancies, including NB.

CONCLUSION

These novel secretory polypeptides may contribute to NB growth. The proteins may reveal additional tumor markers and permit putative use in the diagnosis and treatment of NB. Detection of these proteins in serum of children with NB vs controls (using 2-dimensional polyacrylamide gel electrophoresis and mass spectrometry techniques) is currently in progress.

Galanin and galanin receptors in human cancers

The increasing interest in peptides and peptide receptors in cancer is based on the possibility of receptor targeting, because peptide receptors are often expressed in different human tumors. The neuropeptide galanin has also been suggested to be involved in the development of neuroendocrine tumors based on the development of estrogen-induced tumors in estrogen-sensitive rats. This study summarizes our current knowledge on the expression of galanin peptide and galanin receptors in different human neuroendocrine tumors. The expression of both, peptide and corresponding receptor, seems to be a common feature of human gliomas, pheochromocytomas, pituitary and neuroblastic tumors. The co-expression of galanin and its receptors supports a role for galanin in tumor cell pathology via autocrine/paracrine mechanisms.

[Prognosis of neuroblastoma in childhood. Methods of assessment and clinical use]

Neuroblastoma and its benign counterpart, ganglioneuroma, are pediatric neuroblastic tumors arising in the sympathetic nervous system from neural-crest cells. Neuroblastoma, the most common extra-cranial solid tumour during childhood, is unique for its broad spectrum of clinical virulence from spontaneous remission to rapid and fatal progression despite intensive multimodality therapy. To a large extent, outcome could be predicted by the stage of disease and the age at diagnosis. However, a number of molecular events in neuroblastoma tumors, accounting for the variability of outcome and response to therapy, have been identified over the past decades. Among these, MYCN amplification is the most relevant prognostic factor and was the first genetic marker, in paediatric oncology, to be included in clinical strategies as a guide for therapeutic decision. This has allowed the most suitable intensity of therapy to be delivered according to a risk-stratified strategy, from observation to megadose chemotherapy with stem cell transplantation. Recent advances in understanding the biology and genetics of neuroblastoma will ultimately allow to select poor-risk patients for appropriate future biologically based therapies.

Galanin receptor subtype GalR2 mediates apoptosis in SH-SY5Y neuroblastoma cells

Recently we have shown that galanin binding significantly correlates with survival in neuroblastoma patients, indicating a possible modulatory role of galanin receptors in neuroblastic tumor biology. However, the molecular mechanisms beyond this correlation have not been elucidated. Here, the cellular effects on activation of specific galanin receptor subtypes in human SH-SY5Y neuroblastoma cells were analyzed using a tetracycline-controlled expression system. Pharmacological studies confirmed the inducible expression of high affinity binding sites for galanin in SH-SY5Y cells transfected with the galanin receptors GalR1 (SY5Y/GalR1) and GalR2 (SY5Y/GalR2). Microphysiometry revealed that both receptor subtypes were able to mediate an intracellular signal upon galanin application. Interestingly, induction of receptor expression and treatment with 100 nm galanin resulted in a dramatic decrease in cell viability in SY5Y/GalR2 cells (93 +/- 3%) compared with a less pronounced effect in SY5Y/GalR1 cells (19 +/- 10%). The antiproliferative potency of galanin was 100-fold higher in SY5Y/GalR2 (50% effective concentration, 1.1 nm) than in SY5Y/GalR1 cells (50% effective concentration, 190 nm). Furthermore, activation of receptor expression and exposure to galanin resulted in apparent morphological changes indicative of apoptosis in SY5Y/GalR2 cells only. Induction of cell death by the apoptotic process was confirmed by poly-(ADP-ribose)-polymerase cleavage, caspase-3 activation, and the typical laddering of DNA. This study indicates that a high level of GalR2 expression is able to inhibit cell proliferation and induce apoptosis in neuroblastoma cells and therefore identifies GalR2 as a possible target for pharmacological intervention in neuroblastoma.

‘Neuro’-peptides in glia: Focus on NPY and galanin

The term neuropeptide was advanced by de Wied and collaborators in the early seventies. At that time, they defined neuropeptides as endogenous substances synthesized in nerve cells and involved in nervous system functions. Since then, several studies have revealed that the very same 'neuropeptides' are also expressed in non-neuronal cells. It is therefore generally accepted that the original definition of these peptides was too limited and, consequently, it has recently been revised. Among the non-neuronal cells that synthesize neuropeptides are several glial cell types.

Expression and plasticity of galanin systems in cortical neurons, oligodendrocyte progenitors and proliferative zones in normal brain and after spreading depression

Neocortex contains very few galanin neurons but receives a moderate galanin innervation from various subcortical loci. Recent data suggest that galanin helps regulate the tonic neuronal excitability of hippocampus and probably cerebral cortex but relatively little is known about the anatomy and functional regulation of cortical galanin systems. Therefore, we examined, in the rat, the effect of the intense but benign stimulus, cortical spreading depression (CSD), on the expression of galanin and galanin receptors (GalR1 and GalR2) in the neocortex and associated regions, revealing complex, multicellular responses. Thus, following acute, unilateral KCl-induced CSD, a delayed and transient induction (onset after 48 h, lasting approximately 24 h) of galanin mRNA and peptide production occurred across the ipsilateral cerebral cortex in activated oligodendrocyte progenitor cells (OPCs), identified by specific NG2 proteoglycan immunostaining. An increase in GalR1 mRNA, immunoreactivity and receptor binding occurred in neurons within layers II and V of neocortex and in piriform cortex at 7-28 days after CSD, associated with a long-lasting depletion of galanin-positive nerve fibres in these regions. In contrast, GalR2 mRNA expression was largely unaltered after CSD. Additional novel findings in normal, adult brain were the detection of galanin mRNA and immunoreactivity in OPCs within the medial corpus callosum and in immature progenitor cells in the subventricular zone and rostral migratory stream. GalR1 and GalR2 mRNA was also present in these latter regions. These findings and the complex modulation of galanin and galanin receptors in multiple cell types (neurons/OPCs) following acute cortical activation/depression further demonstrate the potential plasticity of neuronal and non-neuronal galanin systems under physiological and pathological conditions and strongly suggest additional functions for this pleiotropic peptide in mammalian brain.

Gene and protein expression profiling during differentiation of neuroblastoma cells triggered by 13-cis retinoic acid

PURPOSE

The precise changes in RNA and protein expression that accompany neuroblastoma differentiation remain unknown. The authors used microarray technologies to screen molecules associated with the differentiation of neuroblastoma (NB) cells induced by 13-cis retinoic acid.

METHODS

The authors quantified the expression of 2,061 RNA transcripts related to oncogenesis and of 380 proteins expressed in SK-N-SH and CHP-134 NB cell lines in the presence or absence of 13-cis retinoic acid.

RESULTS

Hierarchical clustering captured gene expression altered during neuroblastoma differentiation induced by 13-cis retinoic acid. Several genes were further abstracted based on P values below 0.0017 or protein chips observed in both NB cell lines. The altered expressions of gene products revealed by both DNA and protein chips were in agreement. The expressions of N-myc, cyclin D3, and Wnt10B were downregulated, whereas those of retinoblastoma (RB) and related genes (p107, RB2/p130, p300/CBP, E2F-1, DP-1) as well as others were upregulated.

CONCLUSIONS

These results suggest that microarray technology can screen for genes that are important in neuroblastoma differentiation.