High expression of NPRL2 is linked to poor prognosis in patients with prostate cancer

NPRL2 is required for proliferation of oncogenic Ras-transformed bronchial epithelial cells

Nitrogen permease regulator-like 2 (NPRL2/TUSC4) is known to exert both tumor-suppressing and oncogenic effects in different types of cancers, suggesting that its actions are context dependent. Here, we delineated the molecular and functional effects of NPRL2 in malignantly transformed bronchial epithelial cells. To do so, we depleted NPRL2 in oncogenic HRas-transduced and malignantly transformed human bronchial epithelial (BEAS2B), Ras-AI-T2 cells. Intriguingly, depletion of NPRL2 in these cells induced activation of mTORC1 downstream signaling, inhibited autophagy, and impaired Ras-AI-T2 cell proliferation both in vitro and in vivo. These results suggest that NPRL2 is required for oncogenic HRas-induced cell transformation. Depletion of NPRL2 increased levels of the DNA damage marker γH2AX, the cell cycle inhibitors p21 and p27, and the apoptosis marker cleaved-PARP. These NPRL2-depleted cells first accumulated at G1 and G2, and later exhibited signs of mitotic catastrophe, which implied that NPRL2 depletion may be detrimental to oncogenic HRas-transformed cells. Additionally, NPRL2 depletion reduced heat shock factor 1/heat shock element- and NRF2/antioxidant response element-directed luciferase reporter activities in Ras-AI-T2 cells, indicating that NPRL2 depletion led to the suppression of two key cytoprotective processes in oncogenic HRas-transformed cells. Overall, our data suggest that oncogenic HRas-transduced and malignantly transformed cells may depend on NPRL2 for survival and proliferation, and depletion of NPRL2 also induces a stressed state in these cells.

NPRL2 down-regulation facilitates the growth of hepatocellular carcinoma via the mTOR pathway and autophagy suppression

Hepatocellular carcinoma (HCC) is a highly invasive malignancy. Recently, GATOR1 (Gap Activity TOward Rags 1) complexes have been shown to play an important role in regulating tumor growth. NPRL2 is a critical component of the GATOR1 complex. Therefore, this study used NPRL2 knockdown to investigate how GATORC1 regulates the prognosis and development of HCC via the mammalian target of rapamycin (mTOR) and autophagy signaling pathways. We established HepG2 cells with NPRL2 knockdown using small interfering RNA (siRNA) and short hairpin RNA (shRNA) systems. The siRNA-mediated and shRNA-mediated NPRL2 down-regulation significantly reduced the expression of NPRL2 and two other GATPOR1 complex components, NPRL3 and DEPDC5, in HepG2 cells; furthermore, the efficient down-regulation of NPRL2 protein expression by both the shRNA and siRNA systems enhanced the proliferation, migration, and colony formation in vitro. Additionally, the NPRL2 down-regulation significantly increased HCC growth in the subcutaneous and orthotopic xenograft mouse models. The NPRL2 down-regulation increased the Rag GTPases and mTOR activation and inhibited autophagy in vitro and in vivo. Moreover, the NPRL2 level in the tumors was significantly associated with mortality, recurrence, the serum alpha fetoprotein level, the tumor size, the American Joint Committee on Cancer stage, and the Barcelona Clinic Liver Cancer stage. Low NPRL2, NPRL3, DEPDC5, and LC3, and high p62 and mTOR protein expression in the tumors was significantly associated with disease-free survival and overall survival in 300 patients with HCC after surgical resection. Conclusion: The efficient down-regulation of NPRL2 significantly increased HCC proliferation, migration, and colony formation in vitro, and increased HCC growth in vivo. Low NPRL2 protein expression in the tumors was closely correlated with poorer clinical outcomes in patients with HCC. These results provide a mechanistic understanding of HCC and aid the development of treatments for HCC.

SEA and GATOR 10 Years Later

The SEA complex was described for the first time in yeast Saccharomyces cerevisiae ten years ago, and its human homologue GATOR complex two years later. During the past decade, many advances on the SEA/GATOR biology in different organisms have been made that allowed its role as an essential upstream regulator of the mTORC1 pathway to be defined. In this review, we describe these advances in relation to the identification of multiple functions of the SEA/GATOR complex in nutrient response and beyond and highlight the consequence of GATOR mutations in cancer and neurodegenerative diseases.

FOXO1 inhibits prostate cancer cell proliferation via suppressing E2F1 activated NPRL2 expression

Previous studies in our lab suggest that nitrogen permease regulator 2-like (NPRL2) upregulation in prostate cancer is associated with malignant behavior and poor prognosis. However, the underlying mechanisms of NPRL2 dysregulation remain poorly understood. This study aimed to explore the transcription factors (TFs) contributing to NPRL2 dysregulation in prostate cancer. Potential TFs were identified using prostate tissue/cell-specific chromatin immunoprecipitation (ChIP)-seq data collected in the Cistrome Data Browser and Signaling Pathways Project. Dual-luciferase assay and ChIP-qPCR assay were conducted to assess the binding and activating effect of TFs on the gene promoter. Cell Counting Kit-8 and colony formation assays were performed to assess cell proliferation. Results showed that E2F1 is a TF that bound to the NPRL2 promoter and activated its transcription. NPRL2 inhibition significantly alleviated E2F1 enhanced cell proliferation. Kaplan-Meier survival analysis indicated that E2F1 upregulation was associated with unfavorable progression-free survival and disease-specific survival. FOXO1 interacted and E2F1 in both PC3 and LNCaP cells and weakened the binding of E2F1 to the NPRL2 promoter. Functionally, FOXO1 overexpression significantly slowed the proliferation of PC3 and LNCaP cells and also decreased E2F1 enhanced cell proliferation. In summary, this study revealed a novel FOXO1/E2F1-NPRL2 regulatory axis in prostate cancer. E2F1 binds to the NPRL2 promoter and activates its transcription, while FOXO1 interacts with E2F1 and weakens its transcriptional activating effects. These findings help expand our understanding of the prostate cancer etiology and suggest that the FOXO1/E2F1-NPRL2 signaling axis might be a potential target.

NPRL2 reduces the niraparib sensitivity of castration-resistant prostate cancer via interacting with UBE2M and enhancing neddylation

In this study, we explored the regulatory effects of nitrogen permease regulator 2-like (NPRL2) on niraparib sensitivity, a PARP inhibitor (PARPi) in castrate-resistant prostate cancer (CRPC). Data from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) program were retrospectively examined. Gene-set enrichment analysis (GSEA) was conducted between high and low NRPL2 expression prostate adenocarcinoma (PRAD) cases in TCGA. CCK-8 assay, Western blot analysis of apoptotic proteins, and flow cytometric analysis of apoptosis were applied to test niraparib sensitivity. Immunofluorescent (IF) staining and co-immunoprecipitation (co-IP) were conducted to explore the proteins interacting with NPRL2. Results showed that the upregulation of a canonical protein-coding transcript of NPRL2 (ENST00000232501.7) is associated with an unfavorable prognosis. Bioinformatic analysis predicts a physical interaction between NPRL2 and UBE2M, which is validated by a following Co-IP assay. This interaction increases NPRL2 stability by reducing polyubiquitination and proteasomal degradation. Depletion of NPRL2 or UBE2M significantly increases the niraparib sensitivity of CRPC cells and enhances niraparib-induced tumor growth inhibition in vivo. NPRL2 cooperatively enhances UBE2M-mediated neddylation and facilitates the degradation of multiple substrates of Cullin-RING E3 ubiquitin ligases (CRLs). In conclusion, this study identified a novel NPRL2-UBE2M complex in modulating neddylation and niraparib sensitivity of CRPC cells. Therefore, targeting NPRL2 might be considered as an adjuvant strategy for PARPi therapy.

NPRL2 promotes docetaxel chemoresistance in castration resistant prostate cancer cells by regulating autophagy through the mTOR pathway

Docetaxel-based chemotherapy is recommended for metastatic castration-resistant prostate cancer (mCRPC). However, chemoresistance is inevitable and eventually progresses after several rounds of chemotherapy. Therefore, exploration of new therapeutic targets and molecular mechanisms that contribute to chemoresistance remains necessary. Our previous study accidentally demonstrated that expression of nitrogen permease regulator-like 2 (NPRL2), which is defined as a tumor suppressor, is upregulated in prostate cancer (PCa) and linked to poor prognosis, particularly in CRPC. The aim of this study was to investigate the role of NPRL2 in the chemoresistant CRPC cells. We found that NPRL2 was significantly overexpressed in docetaxel-resistant CRPC cells, while autophagy was enhanced and mTOR signaling was inhibited. Inhibiting NPRL2 increased the sensitivity to docetaxel in docetaxel-resistant CRPC cells, enhanced apoptosis and inhibited autophagy, and the opposite trends were observed when the mTOR inhibitor torin 1 was added to NPRL2-silenced cells. We further found that NPRL2 silenced docetaxel-resistant CRPC cells were sensitive to docetaxel in vivo. Briefly, our research reveals that overexpression of NPRL2 promotes chemoresistance by regulating autophagy via mTOR signaling and inhibits apoptosis in CRPC cells.

Nitrogen Permease Regulator-Like-2 Exhibited Anti-Tumor Effects And Enhanced The Sensitivity Of Colorectal Cancer Cells To Oxaliplatin And 5-Fluorouracil

Background

Colorectal cancer (CRC) is one of the most common malignant tumors in the world. Our previous study revealed that nitrogen permease regulator-like-2 (NPRL2), a promising anti-tumor gene, was downregulated at both the blood and tissue levels in CRC patients compared with that in healthy individuals.

Purpose

This study aims to explore the role of NPRL2 in CRC.

Methods

Herein, we constructed NPRL2 overexpression lentivirus vectors and transfected them into HT29 cells. The transfected cells were inoculated subcutaneously into nude mice. Tumor growth, pathology, apoptosis, and the protein expression of caspase-3, caspase-7, Bax, Bcl-2, and phosphorylated protein kinase B (p-Akt) were evaluated. To further explore whether NPRL2 could reduce drug resistance of CRC cells against oxaliplatin (L-OHP) and 5-fluorouracil (5-FU), we constructed a tumor model using HT29 cells. The tumor model was treated with lentiviral particles assembled with vectors encoding NPRL2 and exposed to L-OHP and 5-FU. Tumor growth, pathology, apoptosis, and the protein expression of caspase-3, caspase-7, Bax, Bcl-2, p-Akt, P-glycoprotein (P-gp), and multidrug resistance protein 1 (MRP1) were evaluated.

Results

The results indicated that in the in vivo CRC xenograft model, NPRL2 reduced the tumor volume and weight and enhanced apoptosis. Our results also confirmed that NPRL2 enhanced the sensitivity of CRC cells to L-OHP and 5-FU. Our studies further demonstrated that NPRL2 exerted anti-tumor and anti-drug resistance effects through the caspase-3, caspase-7, Bax, Bcl-2, Akt, P-gp, and MRP1 pathways.

Conclusion

Our present work demonstrated that NPRL2 exhibited anti-tumor effects and enhanced the sensitivities of CRC cells to L-OHP and 5-FU through the P-gp and MRP1 pathways.

hnRNPM, a potential mediator of YY1 in promoting the epithelial-mesenchymal transition of prostate cancer cells

BACKGROUND

With the popularity of serum prostate-specific antigen (PSA) screening, the number of newly diagnosed prostate cancer (PCa) patients is increasing. However, indolent or invasive PCa cannot be distinguished by PSA levels. Here, we mainly explored the role of heterogeneous nuclear ribonucleoprotein M (hnRNPM) in the invasiveness of PCa.

METHODS

Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis was used to detect the expressions of hnRNPM in PCa and benign prostate hyperplasia (BPH) tissues as well as in PCa cell lines. Immunohistochemistry was applied to detect the hnRNPM or Yin Yang 1 (YY1) expression in BPH, prostate adenocarcinoma (ADENO) and neuroendocrine prostate cancer (NEPC) tissues. After aberrant, the expression of hnRNPM in C4-2 and PC3 cells, the changes of cell migration and invasion were observed through wound-healing and transwell assays. We also predicted the transcription factor of hnRNPM through databases, then verified the association of hnRNPM and YY1 using chromatin immunoprecipitation (ChIP) and luciferase assays.

RESULTS

The expression level of hnRNPM is gradually reduced in BPH, ADENO, and NEPC tissues and it is less expressed in more aggressive PCa cell lines. Overexpression of hnRNPM can significantly reduce Twist1 expression, which inhibits the migration and invasion of PCa cells in vitro. In PCa cells, overexpression of YY1 can promote epithelial-mesenchymal transition by reducing hnRNPM expression. Furthermore, this effect caused by overexpression of YY1 can be partially attenuated by simultaneous overexpression of hnRNPM.

CONCLUSIONS

Our study demonstrates that hnRNPM negatively regulated PCa cell migration and invasion, and its expression can be transcriptionally inhibited by YY1. We speculated that hnRNPM may be a biomarker to assist in judging the aggressiveness of PCa.