CHOIR improves significance-based detection of cell types and states from single-cell data

Clustering is a critical step in the analysis of single-cell data, as it enables the discovery and characterization of putative cell types and states. However, most popular clustering tools do not subject clustering results to statistical inference testing, leading to risks of overclustering or underclustering data and often resulting in ineffective identification of cell types with widely differing prevalence. To address these challenges, we present CHOIR (clustering hierarchy optimization by iterative random forests), which applies a framework of random forest classifiers and permutation tests across a hierarchical clustering tree to statistically determine which clusters represent distinct populations. We demonstrate the enhanced performance of CHOIR through extensive benchmarking against 14 existing clustering methods across 100 simulated and 4 real single-cell RNA-seq, ATAC-seq, spatial transcriptomic, and multi-omic datasets. CHOIR can be applied to any single-cell data type and provides a flexible, scalable, and robust solution to the important challenge of identifying biologically relevant cell groupings within heterogeneous single-cell data.

Mechanisms of drug resistance in nutrient-depleted colorectal cancer cells: insights into lysosomal and mitochondrial drug sequestration

This Review delves into the mechanisms behind drug resistance in colorectal cancer (CRC), particularly examining the role of nutrient depletion and its contribution to multidrug resistance (MDR). The study highlights metabolic adaptations of cancer cells as well as metabolic adaptations of cancer cells under low nutrient availability, including shifts in glycolysis and lipid metabolism. It emphasizes the significance of MDR1 and its encoded efflux transporter, P-glycoprotein (P-gp/B1), in mediating drug resistance and how pathways such as HIF1α, AKT, and mTOR influence the expression of P-gp/B1 under limited nutrient availability. Additionally, the Review explores the dual roles of autophagy in drug sensitivity and resistance under nutrient limited conditions. It further investigates the involvement of lysosomes and mitochondria, focusing on their roles in drug sequestration and the challenges posed by lysosomal entrapment facilitated by non-enzymatic processes and ABC transporters like P-gp/B1. Finally, the Review underscores the importance of understanding the interplay between drug sequestration, lysosomal functions, nutrient depletion, and MDR1 gene modulation. It suggests innovative strategies, including structural modifications and nanotechnology, as promising approaches to overcoming drug resistance in cancer therapy.

DEPTOR as a novel prognostic marker inhibits the proliferation via deactivating mTOR signaling pathway in gastric cancer cells

Aberrantly activated mTOR signaling pathway is commonly found in malignancies including gastric cancer (GC). DEPTOR, as a naturally occurred inhibitor of mTOR, functions in the pro- or anti-tumor manner depending on distinct tumor contexts. However, the roles of DEPTOR in GC remain largely unknown. In this study, DEPTOR expression was identified to be significantly decreased in GC tissues compared with matched normal gastric tissues, and reduced DEPTOR level was indicative of poor prognosis in patients. Restored DEPTOR expression inhibited the propagation in AGS and NCI-N87 cells, whose DEPTOR levels are low, via deactivating mTOR signaling pathway. Likewise, cabergoline (CAB) attenuated the proliferation in AGS and NCI-N87 cells via partially rescuing DEPTOR protein level. Targeted metabolomics analysis showed that several key metabolites, such as l-serine, significantly changed in AGS cells with DEPTOR restoration. These results revealed the anti-proliferation function of DEPTOR in GC cells, suggesting that restored DEPTOR expression using CAB may be a potential therapeutic approach for patients with GC.

The UBE2C/CDH1/DEPTOR axis is an oncogene and tumor suppressor cascade in lung cancer cells

Ubiquitin-conjugating enzyme E2C (UBE2C) mediates ubiquitylation chain formation via the K11 linkage. While previous in vitro studies showed that UBE2C plays a growth-promoting role in cancer cell lines, the underlying mechanism remains elusive. Still unknown is whether and how UBE2C plays a promoting role in vivo. Here we report that UBE2C was indeed essential for growth and survival of lung cancer cells harboring Kras mutations, and UBE2C was required for KrasG12D-induced lung tumorigenesis, since Ube2c deletion significantly inhibited tumor formation and extended the lifespan of mice. Mechanistically, KrasG12D induced expression of UBE2C, which coupled with APC/CCDH1 E3 ligase to promote ubiquitylation and degradation of DEPTOR, leading to activation of mTORC signaling. Importantly, DEPTOR levels fluctuated during cell cycle progression in a manner dependent on UBE2C and CDH1, indicating their physiological connection. Finally, Deptor deletion fully rescued the tumor inhibitory effect of Ube2c deletion in the KrasG12D lung tumor model, indicating a causal role of Deptor. Taken together, our study shows that the UBE2C/CDH1/DEPTOR axis forms an oncogene and tumor suppressor cascade that regulates cell cycle progression and autophagy and validates UBE2C an attractive target for lung cancer associated with Kras mutations.

DFNA5 inhibits colorectal cancer proliferation by suppressing the mTORC1/2 signaling pathways via upregulation of DEPTOR

The human deafness, autosomal dominant 5 gene (DFNA5), a newly discovered executor of pyroptosis, has been strongly implicated in the tumorigenesis of several human cancers. However, an understanding of the functional role of DFNA5 in the development and progression of colorectal cancer (CRC) is limited. In this study, we demonstrated that DFNA5 was downregulated in CRC tissues. Ectopic expression of DFNA5 inhibited tumor cell growth in vitro, retarded tumor formation in vivo, and blocked a cell-cycle transition from the G0/G1 to the S phase, whereas a DFNA5 knockdown promoted cell proliferation. Western blotting showed that the levels of cell cycle-related proteins, including cyclin D1, cyclin E, CDK2, and p21, were accordingly altered upon DFNA5 overexpression or DFNA5 knockdown. Mechanistic studies indicated that DFNA5 exerted its tumor suppressor functions by antagonizing mTORC1/2 signaling via upregulation of DEPTOR. In addition, blockage of mTORC1/2 signaling by Torin-1 abolished the accelerative proliferation by DFNA5 knockdown. In conclusion, these results indicated that DFNA5 inhibits the proliferation and tumor formation of colon cancer cells by suppressing mTORC1/2 signaling.

Overexpressed p-S6 associates with lymph node metastasis and predicts poor prognosis in non-small cell lung cancer

Background

Ribosomal protein S6 (S6), a downstream effect media of the AKT/mTOR pathway, not only is a part of 40S small subunit of eukaryotic ribosome, but also involves in protein synthesis and cell proliferation during cancer development.

Methods

In present study, we explore the association between phosphorylated S6 (p-S6) protein expression and clinicopathological features as well as prognostic implications in NSCLC. P-S6 was detected in tissue microarrays (TMAs) containing 350 NSCLC, 53 non-cancerous lung tissues (Non-CLT), and 88 cases of matched metastatic lymph node lesions via immunohistochemistry (IHC). Transwell assays and wound healing assay were used to assess the effects of p-S6 inhibition on NSCLC cell metastasis.

Results

The p-S6 expression in NSCLC was more evident than that in Non-CLT (p < 0.05). Compared to NSCLC patients who have no lymph node metastasis (LNM), those with LNM had higher p-S6 expression (p = 0.001). Regardless of lung squamous cell carcinoma (SCC) or adenocarcinoma (ADC), p-S6 was increased obviously in metastatic lymph nodes compared with matched primary cancers (p = 0.001, p = 0.022, respectively). Inhibition of p-S6 decreased the metastasis ability of NSCLC cells. In addition, p-S6 was an independent predicted marker for LNM in patients with NSCLC (p < 0.001). According to survival analysis, patients with highly expressed p-S6 had a lower survival rate compared with that with lower expression (p = 0.013). P-S6 is an unfavorable independent prognostic factor for NSCLC patients (p = 0.011).

Conclusion

Increased expression of p-S6 is not only a novel predictive biomarker of LNM but also poor prognosis in NSCLC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09664-4.

Inflammation suppresses DLG2 expression decreasing inflammasome formation

Purpose

Loss of expression of DLG2 has been identified in a number of cancers to contribute to the disease by resulting in increased tumor cell proliferation and poor survival. In light of the previous evidence that DLG2 alters the cell cycle and affects proliferation, combined with indications that DLG2 is involved in NLRP3 inflammasome axis we speculated that DLG2 has an immune function. So far, there is no data that clearly elucidates this role, and this study was designed to investigate DLG2 in inflammatory colon disease and in colon cancer as well as its impact on inflammasome induction.

Methods

The DLG2 expression levels were established in publicly available inflammation, colon cancer and mouse model datasets. The overexpression and silencing of DLG2 in colon cancer cells were used to determine the effect of DLG2 expression on the activation of the inflammasome and subsequent cytokine release.

Results

The expression of DLG2 is repressed in inflammatory colon diseases IBD and Ulcerative colitis as well as colorectal cancer tissue compared to healthy individuals. We subsequently show that induction with inflammatory agents in cell and animal models results in a biphasic alteration of DLG2 with an initial increase followed by an ensuing decrease. DLG2 overexpression leads to a significant increase in expression of IL1B, IκBζ and BAX, components that result in inflammasome formation. DLG2 silencing in THP1 cells resulted in increased release of IL-6 into the microenvironment which once used to treat bystander COLO205 cells resulted in an increase in STAT3 phosphorylation and an increase proliferating cells and more cells in the G2/M phase. Restoration of DLG2 to the colon resulted in reduced AKT and S6 signaling.

Conclusion

DLG2 expression is altered in response to inflammation in the gut as well as colon cancer, resulting in altered ability to form inflammasomes.

Trial registration

NCT03072641.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00432-022-04029-7.

DEPTOR inhibits lung tumorigenesis by inactivating the EGFR-mTOR signals

DEPTOR plays vital roles in the regulation of cell proliferation and survival by directly modulating the activity of mTORC1/2. However, the physiological role of DEPTOR in lung tumorigenesis, as well as its clinical significance, remains elusive. In this study, we revealed that decreased DEPTOR expression correlated with increased tumor size, poor differentiation, and worse survival in patients with lung cancer. DEPTOR depletion promoted cell proliferation, survival, migration, and invasion in human lung cancer cells. Mechanistically, DEPTOR bound to the kinase domain of EGFR via its PDZ domain to inactivate EGFR signal. Thus, DEPTOR depletion not only directly activated mTORC1/2, but also relieved the inhibition of EGFR to subsequently activate mTOR signals, leading to the induction of cell proliferation and survival. Additionally, activated EGFR-mTOR signals upregulated the expression of ZEB1 and SLUG to induce epithelial-mesenchymal transition, resulting in enhanced migration and invasion. Importantly, Deptor deletion accelerated Kras^G12D;p53^fl/fl-induced lung tumorigenesis and shortened mouse life span via the activation of EGFR-mTOR signals. Collectively, our study demonstrated that DEPTOR acts as a tumor suppressor in lung tumorigenesis, and its reduction may advance the progression of human lung cancer.

DEPTOR is an in vivo tumor suppressor that inhibits prostate tumorigenesis via the inactivation of mTORC1/2 signals

The DEPTOR-mTORC1/2 axis has been shown to play an important, but a context dependent role in the regulation of proliferation and the survival of various cancer cells in cell culture settings. The in vivo role of DEPTOR in tumorigenesis remains elusive. Here we showed that the levels of both DEPTOR protein and mRNA were substantially decreased in human prostate cancer tissues, which positively correlated with disease progression. DEPTOR depletion accelerated proliferation and survival, migration, and invasion in human prostate cancer cells. Mechanistically, DEPTOR depletion not only activated both mTORC1 and mTORC2 signals to promote cell proliferation and survival, but also induced an AKT-dependent epithelial–mesenchymal transition (EMT) and β-catenin nuclear translocation to promote cell migration and invasion. Abrogation of mTOR or AKT activation rescued the biological consequences of DEPTOR depletion. Importantly, in a Deptor-KO mouse model, Deptor knockout accelerated prostate tumorigenesis triggered by Pten loss via the activation of mTOR signaling. Collectively, our study demonstrates that DEPTOR is a tumor suppressor in the prostate, and its depletion promotes tumorigenesis via the activation of mTORC1 and mTORC2 signals. Thus, DEPTOR reactivation via a variety of means would have therapeutic potential for the treatment of prostate cancer.

DEPTOR inhibits cell proliferation and confers sensitivity to dopamine agonist in pituitary adenoma

DEP domain-containing mechanistic target of rapamycin (mTOR)-interacting protein (DEPTOR) is an important modulator of mTOR, a highly conserved kinase whose hyperactivation is critically involved in a variety of human tumors. The role of DEPTOR playing in pituitary adenoma (PA) is largely unknown. Here, we reported that DEPTOR was downregulated in PA tissues, especially dopamine-resistant prolactinomas. Consistently, overexpression of DEPTOR inhibited pituitary tumor GH3 and MMQ cells proliferation in vitro and in vivo, and sensitized GH3 and MMQ cells to cabergoline (CAB), a dopamine agonist (DA). Conversely, knockdown of DEPTOR promoted GH3 and MMQ cells proliferation, and conferred cells resistance to CAB. Mechanistically, DEPTOR inhibited both mTOR Complex 1 (mTORC1) and 2 (mTORC2) activities in PA cells. In addition, DEPTOR expression level was increased to suppress mTOR kinase activity via decreasing E3 ubiquitin ligase, βTrCP1, in response to CAB. Furthermore, DEPTOR enhanced autophagy-dependent cell death to confer cells sensitivity to CAB. Taken together, our results suggest that DEPTOR may be a potential target for the treatment of PAs.

Akt2 causes TGFβ-induced deptor downregulation facilitating mTOR to drive podocyte hypertrophy and matrix protein expression

TGFβ promotes podocyte hypertrophy and expression of matrix proteins in fibrotic kidney diseases such as diabetic nephropathy. Both mTORC1 and mTORC2 are hyperactive in response to TGFβ in various renal diseases. Deptor is a component of mTOR complexes and a constitutive inhibitor of their activities. We identified that deptor downregulation by TGFβ maintains hyperactive mTOR in podocytes. To unravel the mechanism, we found that TGFβ -initiated noncanonical signaling controls deptor inhibition. Pharmacological inhibitor of PI 3 kinase, Ly 294002 and pan Akt kinase inhibitor MK 2206 prevented the TGFβ induced downregulation of deptor, resulting in suppression of both mTORC1 and mTORC2 activities. However, specific isoform of Akt involved in this process is not known. We identified Akt2 as predominant isoform expressed in kidney cortex, glomeruli and podocytes. TGFβ time-dependently increased the activating phosphorylation of Akt2. Expression of dominant negative PI 3 kinase and its signaling inhibitor PTEN blocked Akt2 phosphorylation by TGFβ. Inhibition of Akt2 using a phospho-deficient mutant that inactivates its kinase activity, as well as siRNA against the kinase markedly diminished TGFβ -mediated deptor suppression, its association with mTOR and activation of mTORC1 and mTORC2. Importantly, inhibition of Akt2 blocked TGFβ -induced podocyte hypertrophy and expression of the matrix protein fibronectin. This inhibition was reversed by the downregulation of deptor. Interestingly, we detected increased phosphorylation of Akt2 concomitant with TGFβ expression in the kidneys of diabetic rats. Thus, our data identify previously unrecognized Akt2 kinase as a driver of TGFβ induced deptor downregulation and sustained mTORC1 and mTORC2 activation. Furthermore, we provide the first evidence that deptor downstream of Akt2 contributes to podocyte hypertrophy and matrix protein expression found in glomerulosclerosis in different renal diseases.

Prognostic and clinicopathological significance of DEPTOR expression in cancer patients: a meta-analysis

Background

DEP domain containing mammalian target of rapamycin (mTOR)-interacting protein (DEPTOR), a recently discovered endogenous inhibitor of mTOR, has been found to be abnormally expressed in various tumors. Recent studies have demonstrated that DEPTOR could serve as a potential prognostic biomarker in several kinds of cancer. However, the prognostic value of DEPTOR is still controversial so far.

Patients and methods

PubMed, Embase and Web of Science were systematically searched to obtain all relevant articles about the prognostic value of DEPTOR in cancer patients. ORs or HRs with corresponding 95% CIs were pooled to estimate the association between DEP-TOR expression and the clinicopathological characteristics or survival of cancer patients.

Results

A total of nine eligible studies with 974 cancer patients were included in our meta-analysis. Our results demonstrated that the expression of DEPTOR was not associated with the overall survival (OS) (pooled HR=0.795, 95% CI=0.252-2.509) and event-free survival (EFS) (pooled HR=1.244, 95% CI=0.543-2.848) in cancer patients. Furthermore, subgroup analysis divided by sample size, type of cancer, Newcastle-Ottawa Scale (NOS) score and evaluation of DEPTOR expression showed identical prognostic value. In addition, our analysis also revealed that there was no significant association between expression level of DEPTOR and clinicopathological characteristics, such as tumor stage, lymph node metastasis, differentiation grade and gender.

Conclusion

Our meta-analysis suggested that despite the fact that DEPTOR could be overexpressed or downregulated in cancer patients, it might not be a potential marker to predict the prognosis of cancer patients.

CASTOR1 suppresses the progression of lung adenocarcinoma and predicts poor prognosis

As a naturally occurring inhibitor of mammalian target of rapamycin (mTOR), accumulated evidence has confirmed that CASTOR1 plays a pivotal role in regulating the progression of human malignancies. However, the function of CASTOR1 in the development of lung adenocarcinoma is still unclear. Here we report that the expression of CASTOR1 is significantly reduced in lung adenocarcinoma cell lines as compared with that in normal lung epithelial cells. Cellular studies further revealed that ectopic CASTOR1 expression led to a significant suppression of the cellular proliferation, migration, and invasion of PC-9 cells. To further test the role of CASTOR1 in human patients with lung cancers, tumor tissues derived from lung cancer patients and paired adjacent normal lung tissues were collected for immunohistochemical​​​​​​, biochemical, and molecular biology analysis. Immunoblotting and real-time quantitative reverse transcription polymerase chain reaction analysis is revealed that CASTOR1 was significantly reduced in tumor tissues as compared with that in paired normal lung tissues. With immunostaining and retrospective analysis of pathological samples from lung cancer patients further revealed that expression of CASTOR1 was negatively correlated with smoking history, TNM stage, lymphnode metastasis, and distant metastasis. Furthermore, Kaplan-Meier survival analysis indicated that patients with low CASTOR1 expression levels had a significantly worse 5-year survival rate than those with high CASTOR1 expression. To further explore the molecular actions of CASTOR1 in lung cancer development, biochemical assays were performed and the results suggested that ectopic CASTOR1 expression resulted significant suppression of mTOR and downstream S6K phosphorylation, indicating that CASTOR1 might regulate the progression of lung adenocarcinoma by controlling mTOR activation. Thus, these findings demonstrated that CASTOR1 inhibits the tumorigenesis of lung adenocarcinoma cells and might serve as a potential therapeutic target or prognostic marker for human patients with lung adenocarcinoma.

PTRF suppresses the progression of colorectal cancers

As a key component of caveolae structure on the plasma membrane, accumulated evidence has suggested that Polymerase I and Transcript Release Factor (PTRF) plays a pivotal role in suppressing the progression of human malignances. However, the function of PTRF in the development of colorectal cancers is still unclear. Here we report that the expression of PTRF is significantly reduced in tumor tissues derived from human patients with colorectal cancers, and that the downregulation of PTRF correlates to the advanced stage of the disease. In addition, we found that the expression of PTRF negatively regulates the tumorigenic activities of colorectal cell lines (Colo320, HT29 and CaCo2). Furthermore, ectopic PTRF expression caused significant suppression of cellular proliferation, and anchorage-independent colony growth of Colo320 cells, which have the lowest expression level of PTRF in the three studied cell lines. Meanwhile, shRNA mediated knockdown of PTRF in CaCo2 cells significantly promoted cellular proliferation and anchorage-independent colony growth. In addition, in vivo assays further revealed that tumor growth was significantly inhibited in xenografts with ectopic PTRF expression as compared to untreated Colo320 cells, but was markedly enhanced in PTRF knockdown CaCo2 cells. Biochemical studies revealed that overexpression of PTRF led to the suppression of the AKT/mTOR pathway, as evidenced by reduced phosphorylation of AKT, mTOR, and downstream MMP-9. Thus, these findings, for the first time, demonstrated that PTRF inhibits the tumorigenesis of colorectal cancers and that it might serve as a potential therapeutic target for human colon cancer patients.

DEPTOR suppresses the progression of esophageal squamous cell carcinoma and predicts poor prognosis

As a naturally occurring inhibitor of mTOR, accumulated evidence has suggested that DEPTOR plays a pivotal role in suppressing the progression of human malignances. However, the function of DEPTOR in the development of esophageal squamous cell carcinoma (ESCC) is still unclear. Here we report that the expression of DEPTOR is significantly reduced in tumor tissues derived from human patients with ESCC, and the downregulation of DEPTOR predicts a poor prognosis of ESCC patients. In addition, we found that the expression of DEPTOR negatively regulates the tumorigenic activities of ESCC cell lines (KYSE150, KYSE510 and KYSE190). Furthermore, ectopic DEPTOR expression caused a significant suppression of the cellular proliferation, migration and invasion of KYSE150 cells, which has the lowest expression level of DEPTOR in the three cell lines. Meanwhile, CRISPR/Cas9 mediated knockout of DEPTOR in KYSE-510 cells significantly promoted cellular proliferation, migration and invasion. In addition, in vivo assays further revealed that tumor growth was significantly inhibited in xenografts with ectopic DEPTOR expression as compared to untreated KYSE150 cells, and was markedly enhanced in DEPTOR knockout KYSE-510 cells. Biochemical studies revealed that overexpression of DEPTOR led to the suppression of AKT/mTOR pathway as evidenced by reduced phosphorylation of AKT, mTOR and downstream SGK1, indicating DEPTOR might control the progression of ESCC through AKT/mTOR signaling pathway. Thus, these findings, for the first time, demonstrated that DEPTOR inhibits the tumorigenesis of ESCC cells and might serve as a potential therapeutic target or prognostic marker for human patients with ESCC.

Downregulation of DEPTOR inhibits the proliferation, migration, and survival of osteosarcoma through PI3K/Akt/mTOR pathway

Accumulating evidence reveals that DEP-domain containing mTOR-interacting protein (DEPTOR) plays pivotal roles in the pathogenesis and progression of many tumors. However, the expression level of DEPTOR and its function in the tumorigenesis of osteosarcoma (OS) remain unknown. In this study, we conducted quantitative real-time polymerase chain reaction, Western blot, and immunohistochemistry to detect DEPTOR expression level in human OS tissues and cell lines. To assess DEPTOR function, DEPTOR siRNA was designed and transfected into OS cells, which were then used in a series of in vitro assays. Our results indicated that DEPTOR was highly expressed in some OS tissues and cell lines. DEPTOR knockdown by siRNA dramatically inhibited cell proliferation, migration, invasion, and the formation of vasculogenic mimicry in OS cells. In addition, DEPTOR knockdown induced cell cycle arrest in the G0/G1 phase and apoptosis in the OS cell lines, MG63 and MNNG/HOS. Furthermore, we found that DEPTOR knockdown notably activated mTOR and inhibited the PI3K/Akt pathway. Taken together, these results suggest that DEPTOR overexpression is necessary for the proliferation, migration, invasion, formation of vasculogenic mimicry, and survival of OS cells and may be a potential target for the treatment of OS.

Different functions of DEPTOR in modulating sensitivity to chemotherapy for esophageal squamous cell carcinoma

There have been paradoxical findings regarding the expression of DEP domain-containing mTOR-interacting protein (DEPTOR) and its role in predicting prognosis in esophageal squamous cell carcinoma (ESCC). Here we show that DEPTOR expression was significantly increased in tumor tissues and predicted good survival in early stage ESCC patients but not in advanced stage patients. In vitro，our studies showed that ESCC cell lines could be classified into relatively high and low DEPTOR-expressing subgroups according to esophageal squamous epithelial cell line Het-1A.In our study, different levels of DEPTOR expression absolutely determined the response to chemotherapy. In relatively low-expressing cell lines, DEPTOR increased chemotherapy sensitivity via deactivation of the AKT pathway. In relatively high-expressing cell lines, DEPTOR increased cell survival and chemoresistance by strong feedback activation of the IRS1-PI3K-AKT-survivin pathway that occurred after downregulation of ribosomal protein S6 kinase (S6K). Collectively, our findings highlight the dichotomous nature of DEPTOR functions in modulating chemotherapy sensitivity in different ESCC cells.

Deptor: not only a mTOR inhibitor

Deptor is an important protein that belongs to the mTORC1 and mTORC2 complexes, able to interact with mTOR and to inhibit its kinase activity. As a natural mTOR inhibitor, Deptor is involved in several molecular pathways, such as cell growth, apoptosis, autophagy and ER stress response. For this reason, Deptor seems to play an important role in controlling cellular homeostasis. Despite several recent insights characterizing Deptor functions and regulation, its complete role within cells has not yet been completely clarified. Indeed, quite recently, Deptor has been associated with chromatin, and it has been demonstrated having a role in transcriptional regulation, controlling in such way endoplasmatic reticulum activity.

From all these observations it is not surprising that Deptor can behave either as an oncogene or oncosuppressor, depending on the cell- or tissue-contexts. This review highlights recent progresses made in our understanding of the many activities of Deptor, describing its transcriptional and post-transcriptional regulation in different cancer cell types. Moreover, here we discuss the possibility of using compounds able to inhibit Deptor or to disrupt its interaction with mTOR as novel approaches for cancer therapy.

Identification of key genes in colorectal cancer using random walk with restart

As the most common type of cancer and the second leading cause of cancer-associated mortality, colorectal cancer (CRC) has received increasing attention. The aim of the present study was to investigate the mechanisms of CRC by analyzing the microarray dataset, GSE32323. The GSE32323 dataset was downloaded from the Gene Expression Omnibus, and included 17 pairs of matched cancer and normal colorectal tissue samples. The differentially expressed genes (DEGs) were screened using the Linear Models for Microarray Data package and a search of CRC genes, also denoted as seed genes, was performed using the Online Mendelian Inheritance in Man database. Subsequently, the protein‑protein interaction (PPI) network was downloaded from the Search Tool for the Retrieval of Interacting Genes database and the sub‑network (CRC.PPI) of the DEGs and seed genes were obtained. In addition, the top 50 nodes with highest affinity scores in the CRC.PPI were identified using random walk with restart analysis. The potential functions of the DEGs included in the top 50 nodes were analyzed using the Database for Annotation, Visualization and Integrated Discovery online tool. Using the Drug Gene Interaction database, drug‑gene interaction analysis was performed to identify antineoplastic drug interacts with genes. A total of 1,640 DEGs between the CRC and normal samples were screened. The obtained seed genes included cyclin D1 (CCND1) and aurora kinase A (AURKA). The enriched functions for the 31 DEGs in the PPI network of the top 50 nodes were predominantly associated with cell cycle. The DEGs may function in CRC by interacting with other genes in the PPI network of the top 50 nodes, for example, DEP domain‑containing MTOR‑interacting protein (DEPTOR)‑CCND1, AURKA‑breast carcinoma amplified sequence‑1 (BCAS1), CCND1‑BCAS1, CCND1‑neural precursor cell expressed developmentally downregulated 9 (NEDD9) and CCND1‑mitogen‑activated protein kinase kinase 2 (MAP2K2). Only three DEGs (CCND1, AURKA and DEPTOR) had interactions with their corresponding antineoplastic drugs. Taken together, DEPTOR, AURKA, CCND1, BCAS1, NEDD9 and MAP2K2 may act in CRC.

Cul1 promotes melanoma cell proliferation by promoting DEPTOR degradation and enhancing cap-dependent translation

Cullin1 (Cul1) serves as a rigid scaffold in the SCF (Skp1/Cullin/Rbx1/F-box protein) E3 ubiquitin ligase complex and has been found to be overexpressed in melanoma and to enhance melanoma cell proliferation by promoting G1-S phase transition. However, the underlying mechanisms involved in the regulation of melanoma cell proliferation by Cul1 remain poorly understood. In the present study, we found that Cul1 promoted mTORC1 activity and cap-dependent translation by enhancing the ubiquitination and degradation of DEPTOR. We further showed that suppression of the eIF4F complex assembly profoundly inhibited the promoting effect of Cul1 on melanoma cell proliferation, while enhancement of the eIF4F complex activity reversed the inhibitory effect of Cul1 depletion on melanoma cell proliferation, indicating that Cul1 contributes to melanoma cell proliferation by activating cap‑dependent translation. These data elucidate the role of Cul1 in cap-dependent translation and improves our understanding of the underlying mechanisms involved in the regulation of melanoma cell proliferation by Cul1.

DEPTOR has growth suppression activity against pancreatic cancer cells

DEPTOR was reported as a naturally occurring inhibitor of mTORC1 and mTORC2. The role of DEPTOR in the growth and survival of pancreatic cancer cells has not previously been determined. Here we report that while DEPTOR shows a cytoplasmic expression in both normal pancreatic acinar and islet cells in a patchy manner, its expression is reduced in PanIN1 and PanIN2 and completely lost in 100 out of 101 pancreatic ductal adenocarcinoma (PDAC) tissues. Ectopic DEPTOR expression in two pancreatic cancer cell lines, Panc-1 and Miapaca-2, caused a significant 1) suppression of anchorage-dependent growth in monolayer culture, particularly under conditions with growth factor deprivation; 2) decreased clonogenic survival, and 3) suppressed anchorage-independent growth in soft agar. These effects are attributable to moderate induction of apoptosis and growth arrest at the S and G2/M phases, in a cell line dependent manner. Furthermore, ectopic DEPTOR expression moderately inhibited mTORC1 activity, as demonstrated by reduced phosphorylation of S6K, S6, and 4E-BP1. Taken together, these data suggest that DEPTOR has a tumor suppressive activity against pancreatic cancer cells, and its loss of expression may contribute to pancreatic tumorigenesis.