mTOR-related Genes Research Articles

Robust anti-myeloma effect of TAS0612, an RSK/AKT/S6K inhibitor, with venetoclax regardless of cytogenetic abnormalities.

Multiple myeloma (MM) remains a difficult-to-treat disease even with the latest therapeutic advances due to the complex, overlapping, and heterogeneous cytogenetic, genetic, and molecular abnormalities. To address this challenging problem, we previously identified the universal and critical roles of RSK2 and AKT, the effector signaling molecules downstream of PDPK1, regardless of cytogenetic and genetic profiles. Based on this, in this study, we investigated the anti-myeloma potency of TAS0612, a triple inhibitor against RSK, including RSK2, AKT, and S6K. Treatment with TAS0612 exerted the anti-proliferative effect via cell cycle blockade and the induction of apoptosis in human myeloma-derived cell lines (HMCLs) with diverse cytogenetic and genetic profiles. Ex vivo treatment with TAS0612 also significantly reduced the viability of patient-derived primary myeloma cells with diverse cytogenetic profiles. TAS0612 simultaneously caused the upregulation of several tumor suppressor genes, modulated prognostic genes according to the MMRF CoMMpass data, and downregulated a series of Myc- and mTOR-related genes. Moreover, the combination of TAS0612 with venetoclax (VEN) showed the synergy in inducing apoptosis in HMCLs irrespective of the t(11;14) translocation status. TAS0612 alone and combined with VEN are new potent candidate therapeutic strategies for MM, regardless of cytogenetic/genetic profiles, facilitating its future clinical development.

P03.03.A T2-FLUID-ATTENUATED INVERSION RECOVERY MISMATCH SIGN IN LOWER-GRADE GLIOMAS: CORRELATION WITH PATHOLOGICAL AND MOLECULAR FINDINGS

Abstract BACKGROUND After the new molecular-based classification was reported to be useful for predicting prognosis, the T2-fluid-attenuated inversion recovery (FLAIR) mismatch sign has gained interest as one of the promising methods for detecting lower-grade gliomas (LGGs) with isocitrate dehydrogenase (IDH) mutations and chromosome 1p/19q non-codeletion (IDH mut-Noncodel) with high specificity. Although all institutions could use T2-FLAIR mismatch sign without any obstacles, this sign was not completely helpful because of its low sensitivity. In this study, we attempted to uncover the mechanism of T2-FLAIR mismatch sign for clarifying the cause of this sign’s low sensitivity. MATERIAL AND METHODS In this study, data on 101 consecutive and unselected patients with LGGs (WHO grades 2 and 3) admitted to Miyazaki University Hospital between November 2005 and January 2021 were collected. The inclusion criteria were as follows: (1) obtained molecular information on IDH mutation and chromosome 1p/19q codeletion status and (2) obtained preoperative MRI data, including T2-weighted imaging and FLAIR sequences. In this study, 99 patients were enrolled and then classified into three groups based on IDH mutation and chromosome 1p/19q codeletion status: (1) IDH-mutant, 1p/19q-codeleted LGGs (IDH mut-codel); (2) IDH-mutant, 1p/19q-noncodeleted LGGs (IDH mut-Noncodel); and (3) IDH wild-type LGGs (IDH wt). RESULTS Among 99 patients with LGGs, 22 were T2-FLAIR mismatch sign-positive (22%), and this sign as a marker of IDH mut-Noncodel showed a sensitivity of 55.6% and specificity of 96.8%. Via pathological analyses, we could provide evidence that not only microcystic changes but the enlarged intercellular space was associated with T2-FLAIR mismatch sign (p =0.017). As per the molecular analyses, overexpression of mTOR-related genes (m-TOR, RICTOR) were detected as the molecular events correlated with T2-FLAIR mismatch sign (p = 0.020, 0.030. respectively). CONCLUSION We suggested that T2-FLAIR mismatch sign could pick up the IDH mut-Noncodel LGGs with enlarged intercellular space or that with overexpression of mTOR-related genes.

Autism spectrum disorder and brain volume link through a set of mTOR-related genes.

Larger than average head and brain sizes are often observed in individuals with autism spectrum disorders (ASDs). ASD and brain volume are both highly heritable, with multiple genetic variants contributing. However, it is unclear whether ASD and brain volume share any genetic mechanisms. Genes from the mammalian target of rapamycin (mTOR) pathway influence brain volume, and variants are found in rare genetic syndromes that include ASD features. Here we investigated whether variants in mTOR-related genes are also associated with ASD and if they constitute a genetic link between large brains and ASD. We extended our analyses between large heads (macrocephaly) and rare de novo mTOR-related variants in an intellectual disability cohort (N=2,258). Subsequently using Fisher's exact tests we investigated the co-occurrence of mTOR-related de novo variants and ASD in the de-novo-db database (N=23,098). We next selected common genetic variants within a set of 96 mTOR-related genes in genome-wide genetic association data of ASD (N=46,350) to test gene-set association using MAGMA. Lastly, we tested genetic correlation between genome-wide genetic association data of ASD (N=46,350) and intracranial volume (N=25,974) globally using linkage disequilibrium score regression as well as mTOR specific by restricting the genetic correlation to the mTOR-related genes using GNOVA. Our results show that both macrocephaly and ASD occur above chance level in individuals carrying rare de novo variants in mTOR-related genes. We found a significant mTOR gene-set association with ASD (p=.0029) and an mTOR-stratified positive genetic correlation between ASD and intracranial volume (p=.027), despite the absence of a significant genome-wide correlation (p=.81). This work indicates that both rare and common variants in mTOR-related genes are associated with brain volume and ASD and genetically correlate them in the expected direction. We demonstrate that genes involved in mTOR signalling are potential mediators of the relationship between having a large brain and having ASD.

T2-fluid-attenuated inversion recovery mismatch sign in lower grade gliomas: correlation with pathological and molecular findings.

After the new molecular-based classification was reported to be useful for predicting prognosis, the T2-fluid-attenuated inversion recovery (FLAIR) mismatch sign has gained interest as one of the promising methods for detecting lower grade gliomas (LGGs) with isocitrate dehydrogenase (IDH) mutations and chromosome 1p/19q non-codeletion (IDH mut-Noncodel) with high specificity. Although all institutions could use T2-FLAIR mismatch sign without any obstacles, this sign was not completely helpful because of its low sensitivity. In this study, we attempted to uncover the mechanism of T2-FLAIR mismatch sign for clarifying the cause of this sign's low sensitivity. Among 99 patients with LGGs, 22 were T2-FLAIR mismatch sign-positive (22%), and this sign as a marker of IDH mut-Noncodel showed a sensitivity of 55.6% and specificity of 96.8%. Via pathological analyses, we could provide evidence that not only microcystic changes but the enlarged intercellular space was associated with T2-FLAIR mismatch sign (p = 0.017). As per the molecular analyses, overexpression of mTOR-related genes (m-TOR, RICTOR) were detected as the molecular events correlated with T2-FLAIR mismatch sign (p = 0.020, 0.030. respectively). Taken together, we suggested that T2-FLAIR mismatch sign could pick up the IDH mut-Noncodel LGGs with enlarged intercellular space or that with overexpression of mTOR-related genes.

Rap_GAP Domain of TSC2 Contributes to Tumor Suppression Through mTOR Signaling in Human Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is an aggressive disease with a high degree of tumor heterogeneity. Genetic lesions of mTOR-related genes, including TSC2 and hyperactivation of mTOR signaling, are common in HCC. However, the association of genetic alterations with hepatocarcinogenesis remains unclear. In this study, continuous truncating mutations occurred within or upstream of the TSC2 Rap_GAP domain in clinical HCC samples. To elucidate whether hyperactivation of mTOR signaling in HCC is caused by TSC2 truncating mutations, HCC cell models carrying the TSC2 deletion (CRISPR/Cas9) or the TSC2 truncating mutation (mutagenesis) were established. Our findings showed that either TSC2 deletion or TSC2 mutant could lead to TSC2 loss-of-function and hyperactivation of mTOR signaling. Furthermore, hyperactivation of mTOR signaling was relieved by rapamycin. Immunohistochemistry of clinical samples confirmed frequent TSC2 loss in HCC. Thus, our study revealed that genetic alterations cause TSC2 loss of function and result in the hyperactivation of mTOR, and high frequency of TSC2 truncating mutations around RAP_GAP domain may be one of the reasons for the hyperactivation of mTOR in HCC patients.

Translating the Role of mTOR- and RAS-Associated Signalopathies in Autism Spectrum Disorder: Models, Mechanisms and Treatment.

Mutations affecting mTOR or RAS signaling underlie defined syndromes (the so-called mTORopathies and RASopathies) with high risk for Autism Spectrum Disorder (ASD). These syndromes show a broad variety of somatic phenotypes including cancers, skin abnormalities, heart disease and facial dysmorphisms. Less well studied are the neuropsychiatric symptoms such as ASD. Here, we assess the relevance of these signalopathies in ASD reviewing genetic, human cell model, rodent studies and clinical trials. We conclude that signalopathies have an increased liability for ASD and that, in particular, ASD individuals with dysmorphic features and intellectual disability (ID) have a higher chance for disruptive mutations in RAS- and mTOR-related genes. Studies on rodent and human cell models confirm aberrant neuronal development as the underlying pathology. Human studies further suggest that multiple hits are necessary to induce the respective phenotypes. Recent clinical trials do only report improvements for comorbid conditions such as epilepsy or cancer but not for behavioral aspects. Animal models show that treatment during early development can rescue behavioral phenotypes. Taken together, we suggest investigating the differential roles of mTOR and RAS signaling in both human and rodent models, and to test drug treatment both during and after neuronal development in the available model systems.

Exercise training accelerates UPS- and mTOR-mediated protein turnover of grass carp Ctenopharyngodon idella

The present study is aimed to investigate the effects and mechanism of exercise training on the growth and protein turnover in grass carp Ctenopharyngodon idella. To this end, grass carp were respectively cultured at four water velocities (0 (control), 0.5, 1 and 1.5 body length s−1 (bl s−1)) for 10 weeks. The results showed that exercise training increased weight gain rate (WGR) and specific growth rate (SGR), and significantly decreased feed conversion ratio (FCR). The level of serum GH and the mRNA levels of GH/IGF-1 pathway-related genes (ghr and igf-1) of liver were significantly upregulated in C. idella after exercise training at 0.5 and 1 bl s−1. These indicated that at low and medium water velocities, exercise training was beneficial for fish growth. In addition, histochemical analysis of muscle showed that 0.5 bl s−1 exercise training significantly increased muscle fiber density of C. idella. The mRNA expression levels of UPS-related genes (ub, psmc1, psma2 and murf1) and mTOR-related genes (pi3k, mtor and s6k1) were significantly upregulated by 1 and 1.5 bl s−1 water velocity treatments. The levels of polyubiquitinated protein and 3-methylhistidine (3-MH) were significantly increased by the 1 bl s−1 exercise training treatment. These suggested that exercise training facilitated the protein turnover by motivating UPS and mTOR pathway. Taken together, our study demonstrated mechanism of exercise training increasing the growth rate and protein turnover in water velocity-dependent manner in C. idella, which will help to provide fundamental information for raceway-based and recirculating aquaculture system (RAS) aquaculture.

Acceleration of ageing via disturbing mTOR-regulated proteostasis by a new ageing-associated gene PC4.

Research on ageing‐associated genes is important for investigating ageing and anti‐ageing strategies. Here, we firstly reported that the human positive cofactor 4 (PC4), a multifunctional and highly conserved nucleoprotein, is accumulated and activated during ageing and causes global accelerated ageing process by disrupting proteostasis. Mechanistically, PC4 interacts with Sin3‐HDAC complex and inhibits its deacetylated activity, leads to hyper‐acetylation of the histones at the promoters of mTOR‐related genes and causes mTOR signalling activation. Accordingly, mTOR activation causes excessive protein synthesis, resulting in impaired proteostasis and accelerated senescence. These results reveal a new biological function of PC4 in vivo, recognizes PC4 as a new ageing‐associated gene and provides a genetically engineered mouse model to simulate natural ageing. More importantly, our findings also indicate that PC4 is involved in histone acetylation and serves as a potential target to improve proteostasis and delay ageing.

Elevated glucose represses lysosomal and mTOR-related genes in renal epithelial cells composed of progenitor CD133+ cells.

Hyperglycemia is one of the major health concern in many parts of the world. One of the serious complications of high glucose levels is diabetic nephropathy. The preliminary microarray study performed on primary human renal tubular epithelial (hRTE) cells exposed to high glucose levels showed a significant downregulation of mTOR as well as its associated genes as well as lysosomal genes. Based on this preliminary data, the expression of various lysosomal genes as well as mTOR and its associated genes were analyzed in hRTE cells exposed to 5.5, 7.5, 11 and 16 mM glucose. The results validated the microarray analysis, which showed a significant decrease in the mRNA as well as protein expression of the selected genes as the concentration of glucose increased. Co-localization of lysosomal marker, LAMP1 with mTOR showed lower expression of mTOR as the glucose concentration increased, suggesting decrease in mTOR activity. Although the mechanism by which glucose affects the regulation of lysosomal genes is not well known, our results suggest that high levels of glucose may lead to decrease in mTOR expression causing the cells to enter an anabolic state with subsequent downregulation of lysosomal genes.

Identification of cancer biomarkers of prognostic value using specific gene regulatory networks (GRN): a novel role of RAD51AP1 for ovarian and lung cancers.

To date, microarray analyses have led to the discovery of numerous individual 'molecular signatures' associated with specific cancers. However, there are serious limitations for the adoption of these multi-gene signatures in the clinical environment for diagnostic or prognostic testing as studies with more power need to be carried out. This may involve larger richer cohorts and more advanced analyses. In this study, we conduct analyses-based on gene regulatory network-to reveal distinct and common biomarkers across cancer types. Using microarray data of triple-negative and medullary breast, ovarian and lung cancers applied to a combination of glasso and Bayesian networks (BNs), we derived a unique network-containing genes that are uniquely involved: small proline-rich protein 1A (SPRR1A), follistatin like 1 (FSTL1), collagen type XII alpha 1 (COL12A1) and RAD51 associated protein 1 (RAD51AP1). RAD51AP1 and FSTL1 are significantly overexpressed in ovarian cancer patients but only RAD51AP1 is upregulated in lung cancer patients compared with healthy controls. The upregulation of RAD51AP1 was mirrored in the bloods of both ovarian and lung cancer patients, and Kaplan-Meier (KM) plots predicted poorer overall survival (OS) in patients with high expression of RAD51AP1. Suppression of RAD51AP1 by RNA interference reduced cell proliferation in vitro in ovarian (SKOV3) and lung (A549) cancer cells. This effect appears to be modulated by a decrease in the expression of mTOR-related genes and pro-metastatic candidate genes. Our data describe how an initial in silico approach can generate novel biomarkers that could potentially support current clinical practice and improve long-term outcomes.

Variation in a range of mTOR-related genes associates with intracranial volume and intellectual disability

De novo mutations in specific mTOR pathway genes cause brain overgrowth in the context of intellectual disability (ID). By analyzing 101 mMTOR-related genes in a large ID patient cohort and two independent population cohorts, we show that these genes modulate brain growth in health and disease. We report the mTOR activator gene RHEB as an ID gene that is associated with megalencephaly when mutated. Functional testing of mutant RHEB in vertebrate animal models indicates pathway hyperactivation with a concomitant increase in cell and head size, aberrant neuronal migration, and induction of seizures, concordant with the human phenotype. This study reveals that tight control of brain volume is exerted through a large community of mTOR-related genes. Human brain volume can be altered, by either rare disruptive events causing hyperactivation of the pathway, or through the collective effects of common alleles.

Biological Effects of Temsirolimus on the mTOR Pathway in Endometrial Carcinoma: A Pharmacodynamic Phase II Study.

The PI3K/AKT/mTOR pathway is frequently aberrantly activated in endometrial carcinoma (EC). Temsirolimus is an mTOR inhibitor that has shown clinical activity in EC. We aimed to characterize the biological effects on mTOR pathway of temsirolimus in treatment-naive patients with primary EC, and to identify potential biomarkers associated with a short-term exposure to temsirolimus. Patients with EC were treated with 4 doses of temsirolimus previous to surgery. The primary objective was the analysis of paired endometrial aspirates and posttreatment (hysterectomy specimens) tumor tissue samples for mTOR downstream effectors p-S6K1 and p-4BEP1 levels by immunohistochemistry. Secondary objectives included analysis of expression of other mTOR-related biomarkers by immunohistochemistry, as well as analysis of the predictive value of mutations in mTOR-related genes. Toxicity was also assessed. Eleven patients were included in the study. p-S6K1 expression was reduced after treatment with temsirolimus in all patients. Variations of the expression of other mTOR-related proteins including p-4BEP1, PTEN, p-AKT, p53, p27, BAD, Bcl-2, Ki67, and cyclin D1 were also observed. Interestingly, the biological effects of the drug were more evident 1 week after the last dose of temsirolimus. Effects were less evident on tumors harboring mutations in NRAS. Toxicity was acceptable, being mucositis the most frequent adverse event. Short temsirolimus exposure effectively inhibits mTOR pathway in patients with endometrial cancer. p-S6K1 expression is a promising biomarker of sensitivity. The preoperative window opportunity in EC is a realistic scenario for biological knowledge and target development.

Frameshift mutations in mammalian target of rapamycin pathway genes and their regional heterogeneity in sporadic colorectal cancers.

Mammalian target of rapamycin (mTOR) pathway is known to be involved in cancer pathogenesis. The aim of our study was to find whether mTOR-related genes were mutated and expressionally altered in colorectal cancers (CRCs). Through public database searching, we found that PIK3CB, insulin receptor substrate 1/2 (IRS1), RPS6, EIF4B, RPS6KA5, and PRKAA2 that were known as mTOR-related genes possessed mononucleotide repeats in DNA coding sequences that could be mutated in cancers with microsatellite instability (MSI). We analyzed 124 CRCs by single-strand conformation polymorphism analysis and DNA sequencing and found 7 (8.9%), 8 (10.1%), and 3 (3.8%) of 79 CRCs with high MSI that harbored IRS1, EIF4B, and RPS6KA5 frameshift mutations, respectively. These mutations were not identified in stable MSI/low MSI (0/45). In addition, we analyzed intratumoral heterogeneity (ITH) of PIK3CB, IRS1, RPS6, EIF4B, RPS6KA5, and PRKAA2 frameshift mutations in 16 CRCs and found that IRS1, EIF4B, and RPS6KA5 mutations had regional ITH in 2, 2, and 1 CRCs, respectively. We also analyzed IRS1 expression in the CRCs by immunohistochemistry. Loss of IRS1 expression was identified in 31% of the CRCs. The loss of expression was more common in those with IRS1 mutation than those with wild-type IRS1. Our data indicate mTOR-related genes harbored not only somatic mutations but also mutational ITH and loss of expression, which together might play a role in tumorigenesis of CRC, especially with high MSI. Our data also suggest that mutation analysis in multiregional areas is needed for a precise evaluation of mutation status in CRC with MSI-H.

Effects of Arginine concentration on the in vitro expression of Casein and mTOR pathway related genes in mammary epithelial cells from dairy cattle.

Arginine (Arg) is a conditionally-essential amino acid that is taken up by bovine mammary gland in excess of its output in milk. In this study we evaluated the effects of Arg concentration on the expression of casein and signaling pathway-related genes in mammary epithelial cells. The treatments (applied for 24 h) were designed to be devoid of Arg 0X (control; 0.00 mg/L), resemble the profile of Arg in casein (Arg 1X; 278.00 mg/L), be deficient [Arg 0.25X (69.50 mg/L) and Arg 0.5X (139.00 mg/L)], or be in excess of the amount in casein [Arg 2X (556.00 mg/L), Arg 4X (1,112 mg/L), and Arg 8X (2,224 mg/L)]. The expression of CSN1S, CSN3 and mTOR in the experimental groups was higher than those of the control group (P<0.05). Except for Arg 0.25X and Arg 8X (P>0.05), the expression of CSN1S2, CSN2 and JAK2 in other experimental groups was higher (P<0.05) than those in the control group. Except for Arg 8X (P>0.05), the expression of STAT5 in the other experimental groups was higher than those of the control (P<0.05). It also was observed that except for Arg 0.5X, the S6K expression was higher in other experimental groups than the control (P<0.05). In contrast, except for Arg 0.25X the other experimental groups resulted in lower 4EBP1 expression than the control (P<0.05). Among groups, the expression of CSN1S1, CSN1S2, CSN2, CSN3, JAK2, STAT5, mTOR and S6K gene was highest with Arg 2X (P<0.05); the reverse was true for 4EBP1 gene, with the lowest expression in this group (P<0.05). Taken together, Arg appears to play an important role in the transcriptional regulation of casein genes and mTOR-related genes in bovine mammary epithelial cells.

Abstract 3278: A subset of non-small cell lung cancers with wild-type EGFR are sensitized to Erlotinib (EGFR TKI) by mTOR inhibition.

Abstract To date, therapies targeting EGFR have only been effective in treating NSCLC patients whose tumors harbor a mutation in the EGFR gene. However, wild-type EGFR is often amplified in tumors and may still be an important, targetable driver even when no mutation is present. Continued activation of the PI3K-AKT-mTOR signaling pathway in the face of EGFR inhibition is a known indicator of resistance to EGFR targeted therapies. Therefore combination of an EGFR inhibitor with an inhibitor of the downstream kinase mTOR may be a useful strategy to overcome resistance to EGFR inhibition. In this study, the EGFR tyrosine kinase inhibitor, erlotinib, was used in combination with the dual mTORC1/2 inhibitor, Torin1, to screen a panel of NSCLC cell lines (N = 25) for a synergistic response to the combination of Torin1 + erlotinib verses each agent individually. A subset of EGFR wild-type NSCLC cell lines (5/25) responded synergistically to the erlotinib/Torin1 combination. Several cell lines in this subset harbor mutations in the Ras oncogene and thus are resistant to EGFR targeting monotherapy. These lines are also resistant to Torin1 treatment as a single agent. The erlotinib/Torin1 combination did not induce apoptosis or alter the cell cycle profile of the sensitized cell lines, but rather appears to slow the rate of proliferation. Other mTOR inhibitors such as the standard mTORC1 inhibitor, rapamycin, and the dual mTORC1/2 inhibitor AZD8055 sensitize these lines to erlotinib, but not to the same extent that Torin1 does. Erlotinib sensitive, EGFR mutant lines, and EGFR mutant lines with additional resistance mutations, are not sensitized to erlotinib with the addition of Torin1. The ability of Torin1 to sensitize lines appears to be specific for EGFR inhibition, as it does not sensitize these lines to standard Paclitaxel/Carboplatin doublet chemotherapy. We are exploring the possibility of feedback loops which are affected specifically by the Erlotinib/Torin1 combination, which may lead to the sensitization seen in these lines. Several avenues are being explored in order to determine biomarkers which may be used to predict a synergistic response to combined erlotinib/Torin1 therapy. Gene expression (microarray) has provided a candidate list of genes that are highly up-/down-regulated specifically in the responding subset of cell lines. Additionally, an siRNA mini-library screen (targeting 54 genes) focusing on mTOR related genes and GC/MS analyses to determine differences in metabolite levels between cell lines and following treatments, are being used to examine the role of metabolic differences in determining response to erlotinib/Torin1 therapy. By determining metabolic biomarkers to predict a synergistic response to erlotinib/Torin1 therapy, we hope to expand the utility of EGFR targeting therapies to EGFR wild-type tumors in a predictable and clinically relevant manner. Citation Format: Rebecca R. Britt, Luc Girard, Hyuntae Yoo, John Minna. A subset of non-small cell lung cancers with wild-type EGFR are sensitized to Erlotinib (EGFR TKI) by mTOR inhibition. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3278. doi:10.1158/1538-7445.AM2013-3278

Next‐generation RNA sequencing reveals differential expression of MYCN target genes and suggests the mTOR pathway as a promising therapy target in MYCN‐amplified neuroblastoma

In many cancer types, MYC proteins are known to be master regulators of the RNA-producing machinery. Neuroblastoma is a tumor of early childhood characterized by heterogeneous clinical courses. Amplification of the MYCN oncogene is a marker of poor patient outcome in this disease. Here, we investigated the MYCN-driven transcriptome of 20 primary neuroblastomas with and without MYCN amplification using next-generation RNA sequencing and compared the results to those from an in vitro cell model for inducible MYCN (SH-EP MYCN-ER). Transcriptome sequencing produced 30-90 million mappable reads for each dataset. The most abundant RNA species was mRNA, but snoRNAs, pseudogenes and processed transcripts were also recovered. A total of 223 genes were significantly differentially expressed between MYCN-amplified and single-copy tumors. Of those genes associated with MYCN both in vitro and in vivo, 32% of MYCN upregulated and 37% of MYCN downregulated genes were verified either as previously identified MYCN targets or as having MYCN-binding motifs. Pathway analyses suggested transcriptomal upregulation of mTOR-related genes by MYCN. MYCN-driven neuroblastomas in mice displayed activation of the mTOR pathway on the protein level and activation of MYCN in SH-EP MYCN-ER cells resulted in high sensitivity toward mTOR inhibition in vitro. We conclude that next-generation RNA sequencing allows for the identification of MYCN regulated transcripts in neuroblastoma. As our results suggest MYCN involvement in mTOR pathway activation on the transcriptional level, mTOR inhibitors should be further evaluated for the treatment of MYCN-amplified neuroblastoma.

Abstract 1706: Microarray analysis of gene expression reveals that several mTOR related genes are upregulated in cisplatin resistant ovarian cancer cells

Abstract The mTOR pathway plays a central role in regulating protein synthesis, ribosomal protein translation, and cap-dependent translation. Recently, also mTOR signaling has been implicated not only in tumor development, but also in drug resistance against chemotherapy and radiotherapy. The mTOR pathway has emerged as an important cancer therapeutic target, principally with rapamycin and its derivatives. However the use of these mTOR inhibitors has been hampered because many cancer cells are resistant to these compounds. Cisplatin has been the most active drug for the treatment of ovarian cancer for almost 40 years. Although the majority of patients with ovarian cancer respond to front-line platinum combination chemotherapy the majority will develop disease that becomes resistant to cisplatin. The exact mechanism of cisplatin resistance is presently unknown. We performed growth inhibition experiments and found that the A2780CP20 human ovarian cancer cell line, which is resistant to cisplatin was also resistant to rapamycin and its analogs. Opposite, the cisplatin-sensitive counterpart, A2780PAR cell line was very sensitive to these compounds. Short-term treatment (4-hr) of A2780PAR cells with temsirolimus also induced long-term growth inhibitory effects as observed with a colony formation assay. Microarray analysis of gene expression showed that several survival related genes are up-regulated in A2780CP20 compared with the A2780PAR ovarian cancer cells. Current studies with small interference RNA (siRNA) will determine whether silencing of some candidate genes will sensitize cisplatin resistant ovarian cancer cells to rapamycin treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1706. doi:10.1158/1538-7445.AM2011-1706