SLC3A2 is upregulated in human osteosarcoma and promotes tumor growth through the PI3K/Akt signaling pathway

Unraveling pathogenesis, biomarkers and potential therapeutic agents for endometriosis associated with disulfidptosis based on bioinformatics analysis, machine learning and experiment validation

BACKGROUND

Endometriosis (EMs) is an enigmatic disease of yet-unknown pathogenesis. Disulfidptosis, a novel identified form of programmed cell death resulting from disulfide stress, stands a chance of treating diverse ailments. However, the potential roles of disulfidptosis-related genes (DRGs) in EMs remain elusive. This study aims to thoroughly explore the key disulfidptosis genes involved in EMs, and probe novel diagnostic markers and candidate therapeutic compounds from the aspect of disulfidptosis based on bioinformatics analysis, machine learning, and animal experiments.

RESULTS

Enrichment analysis on key module genes and differentially expressed genes (DEGs) of eutopic and ectopic endometrial tissues in EMs suggested that EMs was closely related to disulfidptosis. And then, we obtained 20 and 16 disulfidptosis-related DEGs in eutopic and ectopic endometrial tissue, respectively. The protein-protein interaction (PPI) network revealed complex interactions between genes, and screened nine and ten hub genes in eutopic and ectopic endometrial tissue, respectively. Furthermore, immune infiltration analysis uncovered distinct differences in the immunocyte, human leukocyte antigen (HLA) gene set, and immune checkpoints in the eutopic and ectopic endometrial tissues when compared with health control. Besides, the hub genes mentioned above showed a close correlation with the immune microenvironment of EMs. Furthermore, four machine learning algorithms were applied to screen signature genes in eutopic and ectopic endometrial tissue, including the binary logistic regression (BLR), the least absolute shrinkage and selection operator (LASSO), the support vector machine-recursive feature elimination (SVM-RFE), and the extreme gradient boosting (XGBoost). Model training and hyperparameter tuning were implemented on 80% of the data using a ten-fold cross-validation method, and tested in the testing sets which determined the excellent diagnostic performance of these models by six indicators (Sensitivity, Specificity, Positive Predictive Value, Negative Predictive Value, Accuracy, and Area Under Curve). And seven eutopic signature genes (ACTB, GYS1, IQGAP1, MYH10, NUBPL, SLC7A11, TLN1) and five ectopic signature genes (CAPZB, CD2AP, MYH10, OXSM, PDLIM1) were finally identified based on machine learning. The independent validation dataset also showed high accuracy of the signature genes (IQGAP1, SLC7A11, CD2AP, MYH10, PDLIM1) in predicting EMs. Moreover, we screened 12 specific compounds for EMs based on ectopic signature genes and the pharmacological impact of tretinoin on signature genes was further verified in the ectopic lesion in the EMs murine model.

CONCLUSION

This study verified a close association between disulfidptosis and EMs based on bioinformatics analysis, machine learning, and animal experiments. Further investigation on the biological mechanism of disulfidptosis in EMs is anticipated to yield novel advancements for searching for potential diagnostic biomarkers and revolutionary therapeutic approaches in EMs.

Amino acid transporters within the solute carrier superfamily: Underappreciated proteins and novel opportunities for cancer therapy

BACKGROUND

Solute carrier (SLC) transporters, a diverse family of membrane proteins, are instrumental in orchestrating the intake and efflux of nutrients including amino acids, vitamins, ions, nutrients, etc, across cell membranes. This dynamic process is critical for sustaining the metabolic demands of cancer cells, promoting their survival, proliferation, and adaptation to the tumor microenvironment (TME). Amino acids are fundamental building blocks of cells and play essential roles in protein synthesis, nutrient sensing, and oncogenic signaling pathways. As key transporters of amino acids, SLCs have emerged as crucial players in maintaining cellular amino acid homeostasis, and their dysregulation is implicated in various cancer types. Thus, understanding the intricate connections between amino acids, SLCs, and cancer is pivotal for unraveling novel therapeutic targets and strategies.

SCOPE OF REVIEW

In this review, we delve into the significant impact of amino acid carriers of the SLCs family on the growth and progression of cancer and explore the current state of knowledge in this field, shedding light on the molecular mechanisms that underlie these relationships and highlighting potential avenues for future research and clinical interventions.

MAJOR CONCLUSIONS

Amino acids transportation by SLCs plays a critical role in tumor progression. However, some studies revealed the tumor suppressor function of SLCs. Although several studies evaluated the function of SLC7A11 and SLC1A5, the role of some SLC proteins in cancer is not studied well. To exert their functions, SLCs mediate metabolic rewiring, regulate the maintenance of redox balance, affect main oncogenic pathways, regulate amino acids bioavailability within the TME, and alter the sensitivity of cancer cells to therapeutics. However, different therapeutic methods that prevent the function of SLCs were able to inhibit tumor progression. This comprehensive review provides insights into a rapidly evolving area of cancer biology by focusing on amino acids and their transporters within the SLC superfamily.

Hsa_circ_0050900 affects ferroptosis in intrahepatic cholangiocarcinoma cells by targeting hsa‑miR-605‑3p to regulate SLC3A2

Intrahepatic cholangiocarcinoma (ICC) is a highly lethal hepatobiliary tumor with high aggressiveness. The role of circular RNA (circRNA) in ICC remains to be explored. The present study aimed to investigate whether hsa_circ_0050900 affected ferroptosis in ICC cells by regulating hsa-microRNA (miR)-605-3p/solute carrier family 3 member 2 (SLC3A2). Human ICC cells were cultured and hsa_circ_0050900 expression was evaluated by reverse transcription-quantitative PCR. hsa_circ_0050900 was knocked down and ferroptosis inhibitor ferrostatin-1 was added to HuCCT-1 cells. Following knockdown or overexpression of hsa-miR-605-3p, Fe2+, reactive oxygen species (ROS), glutathione peroxidase 4 and SLC3A2 levels were assessed using iron and ROS assay kit or RT-qPCR and western blotting, respectively. Cell function experiments were performed to examine proliferation and migration abilities. Dual-luciferase reporter gene and argonaute2-RNA immunoprecipitation assay verified the relationship among hsa_circ_0050900, hsa-miR-605-3p, and SLC3A2. hsa_circ_0050900 was derived from actinin alpha 4 gene and was elevated in ICC cells. Among HuCCT-1, QBC-939, HCCC-9810, and RBE cell lines, the highest expression was in HuCCT-1 cells. Inhibition of hsa_circ_0050900 inhibited proliferation and migration by facilitating ICC cell ferroptosis. hsa-miR-605-3p expression was elevated after knocking down hsa_circ_0050900 and hsa-miR-605-3p was negatively regulated by hsa_circ_0050900. In addition, hsa-miR-605-3p targeted SLC3A2. Overexpression of hsa-miR-605-3p regulated SLC3A2 to promote ICC cell ferroptosis and inhibit proliferation and migration. Taken together, knockdown of hsa_circ_0050900 inhibited SLC3A2 expression via sponging hsa-miR-605-3p to promote ICC cell ferroptosis, and finally suppressed proliferation and migration. The present study suggested that hsa_circ_0050900 was a potential therapeutic target for ICC.

Downregulation of SLC3A2 mediates immune evasion and accelerates metastasis in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is a common malignancy originating from oral mucosal tissue. OSCC cells employ immune evasion strategies to avoid immune attacks, but research on inhibiting immune evasion and delaying OSCC progression is limited. This study aimed to investigate how SLC3A2 downregulation mediates immune evasion and promotes metastasis in OSCC through bioinformatics analysis and cell experiments. Gene enrichment analysis was performed using human double sulphur death-related genes from the GSEA database. Differentially expressed genes were selected from the GEO database. Diagnostic models were constructed and validated using gene expression datasets. Immune infiltration and function were analysed through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Cell experiments were conducted to evaluate the impact of SLC3A2 on immune response in OSCC. Ten double sulphur death-related genes were identified, with SLC3A2 and SLC7A11 being enriched in tongue squamous cell carcinoma-related diseases. Differential expression analysis revealed five genes (SLC3A2, SLC7A11, RPN1, GYS1 and NDUFS1) of diagnostic significance. GO analysis showed enrichment in amino acid import and transmembrane transport, while KEGG pathway analysis highlighted enrichment in ferroptosis, diabetic cardiomyopathy, and Starch and sucrose metabolism. Experimental verification confirmed higher SLC3A2 expression in OSCC cells. Overexpression of SLC3A2 inhibited cell proliferation and reduced PD-1 and CTLA-4 expression. Reduced SLC3A2 expression in OSCC promotes immune evasion and tumour progression by impairing T lymphocyte function. This study provides insights into targeted regulation of SLC3A2 expression for immune response-based therapies in OSCC.

CD98 heavy chain as a prognostic biomarker and target for cancer treatment

The SLC3A2 gene encodes for a cell-surface transmembrane protein CD98hc (4F2). CD98hc serves as a chaperone for LAT1 (SLC7A5), LAT2 (SLC7A8), y+LAT1 (SLC7A7), y+LAT2 (SLC7A6), xCT (SLC7A11) and Asc1 (SLC7A10) providing their recruitment to the plasma membrane. Together with the light subunits, it constitutes heterodimeric transmembrane amino acid transporters. CD98hc interacts with other surface molecules, such as extracellular matrix metalloproteinase inducer CD147 (EMMPRIN) and adhesion receptors integrins, and regulates glucose uptake. In this way, CD98hc connects the signaling pathways sustaining cell proliferation and migration, biosynthesis and antioxidant defense, energy production, and stem cell properties. This multifaceted role makes CD98hc one of the critical regulators of tumor growth, therapy resistance, and metastases. Indeed, the high expression levels of CD98hc were confirmed in various tumor tissues, including head and neck squamous cell carcinoma, glioblastoma, colon adenocarcinoma, pancreatic ductal adenocarcinoma, and others. A high expression of CD98hc has been linked to clinical prognosis and response to chemo- and radiotherapy in several types of cancer. In this mini-review, we discuss the physiological functions of CD98hc, its role in regulating tumor stemness, metastases, and therapy resistance, and the clinical significance of CD98hc as a tumor marker and therapeutic target.

Role of ferroptosis in esophageal cancer and corresponding immunotherapy

Esophageal cancer (EC) is one of the most common digestive system malignancies in the world. The combined modality treatment of EC is usually surgery and radiation therapy, however, its clinical efficacy for advanced patients is relatively limited. Ferroptosis, a new type of iron-dependent programmed cell death, is different from apoptosis, necrosis and autophagy. In recent years, many studies have further enlightened that ferroptosis plays an essential role in the occurrence, development and metastasis of tumors. Targeting ferroptosis stimulates a new direction for further exploration of oncologic treatment regimens. Furthermore, ferroptosis has a critical role in the immune microenvironment of tumors. This paper reviews the mechanism of ferroptosis and the ferroptosis research progress in the treatment of EC. We further elaborate the interaction between ferroptosis and immunotherapy, and the related mechanisms of ferroptosis participation in the immunotherapy of EC, so as to provide new directions and ideas for the treatment of EC.

Functional role of MicroRNA/PI3K/AKT axis in osteosarcoma

Osteosarcoma (OS) is a primary malignant bone tumor that occurs in children and adolescents, and the PI3K/AKT pathway is overactivated in most OS patients. MicroRNAs (miRNAs) are highly conserved endogenous non-protein-coding RNAs that can regulate gene expression by repressing mRNA translation or degrading mRNA. MiRNAs are enriched in the PI3K/AKT pathway, and aberrant PI3K/AKT pathway activation is involved in the development of osteosarcoma. There is increasing evidence that miRNAs can regulate the biological functions of cells by regulating the PI3K/AKT pathway. MiRNA/PI3K/AKT axis can regulate the expression of osteosarcoma-related genes and then regulate cancer progression. MiRNA expression associated with PI3K/AKT pathway is also clearly associated with many clinical features. In addition, PI3K/AKT pathway-associated miRNAs are potential biomarkers for osteosarcoma diagnosis, treatment and prognostic assessment. This article reviews recent research advances on the role and clinical application of PI3K/AKT pathway and miRNA/PI3K/AKT axis in the development of osteosarcoma.

In Vitro and In Vivo Comparative Analysis of Differentially Expressed Genes and Signaling Pathways in Breast Cancer Cells on Interaction with Mesenchymal Stem Cells

The interaction of breast cancer cells (BCC) with mesenchymal stem cells (MSC) plays a vital role in influencing the gene expression in breast cancer cells and thereby its uncontrolled proliferation, metastasis, and drug resistance. The extent of MSC governing the BCC or the extent of BCC influencing the MSC is a complex process, and the interaction strongly depends upon conditions such as the presence or absence of other cell types and in vivo tumor microenvironment or simple in vitro conditions. Hence, understanding this interaction through gene expression profiling may provide key insights about potential genes which can be targeted for breast cancer treatment. In the current study, in vitro microarray dataset and in vivo RNA-seq dataset of BCC on interaction with the MSC were downloaded from NCBI GEO database and analyzed for differentially expressed genes (DEGs), gene ontology (GO) term enrichment, and Reactome pathway analysis. To target the genes which have similar effect on both in vitro and in vivo, a comparative analysis was performed, 24 genes were commonly upregulated in both in vitro and in vivo datasets, while no common downregulated genes were observed. Out of which, 16 significant genes based upon fold change (logFC > 2) are identified for manipulating the interactions between MSC and BCC. Among them, 6 of the identified genes (FSTL1, LOX, SERPINE1, INHBA, FN1, and VEGFA) have already been reported to be upregulated in BCC on interaction with MSC by various studies. Further experiments need to be conducted to understand the role of remaining 10 identified genes (EFEMP1, IGFBP3, EDIL3, IFITM1, IGFBP4, ITGA5, SLC3A2, HRH1, PPP1R15A, and NNMT) in MSC-BCC interaction. In addition to the reported significant genes and its associated pathways, the expression of long non-coding RNA identified in this study may increase our understanding about the way MSC interacts with BCC and accelerate MSC-based treatment strategies for breast cancer.

Characterizing the role of SLC3A2 in the molecular landscape and immune microenvironment across human tumors

Background: Inducing ferroptosis in human tumors has become a potential strategy to improve the prognosis of patients, even in those with chemotherapeutic resistance. The xCT complex is a major target for ferroptosis induction, constituted by SLC7A11 and SLC3A2. The role of SLC7A11 in cancer has been widely studied in recent years. However, related research studies for its partner SLC3A2 are still rare.

Methods: Bulk transcriptome, single-cell sequencing, and immunohistochemical staining were analyzed to explore the expression distribution of SLC3A2. Clinical outcomes were referred to uncover the relationship between SLC3A2 expression and patients’ prognosis. Immune cell infiltration was estimated by multiple deconvolution algorithms. The effect of SLC3A2 on the proliferation and drug resistance of cancer cell lines was evaluated by DEPMAP.

Results: Upregulated SLC3A2 may have an adverse effect on the survival of multiple cancers such as lower-grade glioma and acute myeloid leukemia. SLC3A2 expression is indispensable for multiple cell lines’ proliferation, especially for ESO51 (a cell line for esophageal cancer). In addition, SLC3A2 expression level was related to the remodeling of the immune microenvironment in cancers and some immune checkpoints such as PD-1 and PD-L1, which were potential therapeutic targets in many distinct cancers.

Conclusion: Our study systematically elucidated the role of SLC3A2 in the survival of cancer patients and the potential immunotherapeutic response. Few molecular mechanisms by which SLC3A2 regulates anti-tumor immunity have been clarified in the present study, which is the main limitation. Future research into the biological mechanism could further help with targeted treatment for cancer patients.

MIF/SCL3A2 depletion inhibits the proliferation and metastasis of colorectal cancer cells via the AKT/GSK-3β pathway and cell iron death

This study investigated the mechanisms of migration inhibitory factor (MIF) and solute carrier family 3 member 2 (SLC3A2) in colorectal cancer progression. The levels of MIF and SLC3A2 expression in cells were measured by RT-qPCR. SW480 and SW620 cells were transfected with sh-MIF and sh-SLC3A2, respectively. MIF, SLC3A2, GPX4, E-cadherin and N-cadherin expression were detected by immunofluorescence (IF). CCK8 and Transwell assays were performed to detect cell proliferation and migration. Co-immunoprecipitation (CoIP) was used to measure the binding activity of MIF and SLC3A2. Finally, a nude mouse tumorigenicity assay was used to confirm the functions of MIF and SLC3A2 in colorectal cancer. Results showed that the levels of MIF and SLC3A2 expression were up-regulated in colorectal cancer cells. Inhibition of MIF or SLC3A2 expression prevented cell proliferation, migration, epithelial-mesenchymal transition (EMT) and invasion. In addition, knockdown of MIF and SLC3A2 promoted iron death in SW480 and SW620 cells. CoIP results showed that MIF and SLC3A2 directly interact with each other. Knockdown of both MIF and SLC3A2 inhibited tumour growth and metastasis via the AKT/GSK-3β pathway in vivo. The Akt/GSK-3β pathway was found to participate in regulating MIF and SLC3A2 both in vivo and in vitro. MIF and SLC3A2 might be potential biomarkers for monitoring the treatment of colorectal cancer.

Alloferon Affects the Chemosensitivity of Pancreatic Cancer by Regulating the Expression of SLC6A14

Pancreatic cancer (PCa), one of the most malignant solid tumors, has a high mortality rate. Although there have been many trials of chemotherapeutic drugs such as gemcitabine, the mortality rates remain significantly higher than for other types of cancer. Therefore, more effective ways of improving conventional therapy for PCa are needed. Cancer cells take up large amounts of glutamine to drive their rapid proliferation. Recent studies show that the amino acid transporter SLC6A14 is upregulated in some cancers alongside glutamine metabolism. Alloferon, a peptide isolated from the insect immune system, exerts anti-viral and anti-inflammatory effects via its immunomodulatory function. In addition, it has anti-tumoral effects, although the underlying mechanisms are largely unknown. Therefore, we investigated the effects of alloferon on the PCa cell lines Panc-1 and AsPC-1. Exposure of these cells to alloferon for 3 weeks led to the downregulation of SLC6A14 expression and decreased glutamine uptake. Given that SLC6A14 plays a role in tumor progression and survival by promoting glutamine uptake into cancer cells, alloferon could be a potential adjuvant for the chemotherapeutic drug gemcitabine.

Identification of a Solute Carrier Family-Based Signature for Predicting Overall Survival in Osteosarcoma

Given the important role of SLC family in essential physiological processes including nutrient uptake, ion transport, and waste removal, and that their dysregulation was found in distinct forms of cancer, here we identified a novel gene signature of SLC family for patient risk stratification in osteosarcoma. Gene expression data and relevant clinical materials of osteosarcoma samples were retrieved from The Cancer Genome Atlas (TCGA) database. Prognosis-related SLC genes were identified by performing univariate Cox regression analysis and were utilized to construct a four-SLC gene signature in osteosarcoma. It allowed patients to be classified into high- and low-risk groups, and Kaplan-Meier survival analysis in the training, testing, entire, and external GSE21257 cohorts suggested that the overall survival of patients in high-risk group was consistently worse than that in low-risk group, suggesting the promising accuracy and generalizability of the SLC-based signature in predicting the prognosis of patients with osteosarcoma. Moreover, univariate and multivariate Cox regression analyses indicated that the derived risk score was the only independent prognostic factor for osteosarcoma patients in TCGA and GSE21257 cohorts. Besides, a prognostic nomogram comprising the derived risk score and clinical features including gender and age was developed for clinical decision-making. Functional enrichment analyses of the differentially expressed genes between high- and low-risk group revealed that immune-related biological processes and pathways were significantly enriched. Estimation of tumor immune microenvironment using ESTIMATE algorithm revealed that patients with lower risk score had higher stromal, immune, and ESTIMATE score, and lower tumor purity. ssGSEA analyses indicated that the scores of various immune subpopulations including CD8+ T cells, DCs, and TIL were lower in high-risk group than these in low-risk group in both cohorts. As for the related immune functions, the scores of APC co-inhibition, CCR, check-point, T cell co-stimulation, and Type II IFN response were lower in high-risk group than these in low-risk group in both cohorts. In all, we identified a novel prognostic signature based on four SLC family genes that accurately predicted overall survival in osteosarcoma patients. Furthermore, the signature is linked to differences in immunological status and immune cell infiltrations in the tumor microenvironment.

Identification of DNA aptamers that specifically targets EBV+ nasopharyngeal carcinoma via binding with EphA2/CD98hc complex

Nasopharyngeal carcinoma (NPC) is one of the Epstein-Barr virus (EBV)-associated malignancies and has a distinct geographical distribution. The high mortality rates of NPC patients with advanced and recurrent disease highlight the urgent need for biomarkers for early diagnosis and effective treatments. In this study, we developed DNA aptamers that specifically bind to EBV positive NPC cells by the Cell-SELEX procedure. We further identified the EphA2 (ephrin type-A receptor 2)/CD98hc (CD98 heavy chain) complex as the potential target of the aptamer EA-3 by combining aptamer-based separation and mass spectrometry analysis. Our results revealed for the first time that EphA2 colocalized with CD98hc at the plasma membrane and EphA2 coimmunoprecipitated with CD98hc, which may serve as a starting point for exploring the potential functions of the complex of EphA2 and CD98hc in NPCs. Here, we demonstrated that aptamers can be useful for the identification of protein complexes on the surface of cancer cells.

SLC3A2 inhibits ferroptosis in laryngeal carcinoma via mTOR pathway

Objective

This study aimed to explore the mRNA and protein expression of SLC3A2 in laryngeal carcinoma cells and tissues, and functional regulatory mechanism of SLC3A2 in cell ferroptosis of laryngeal carcinoma.

Methods

We chose the key gene-SLC3A2 of DEGs from TCGA by bioinformatics analysis, and then we constructed stable knockdown of SLC3A2 in laryngeal carcinoma cells. MTT assay and clonogenic assay were used to determine cell viability and cell growth, respectively. The mRNA and protein expression were determined by RT-qPCR and western blotting, respectively. Xenograft tumor model was used to determine the role of SLC3A2 in tumor growth.

Results

The results of limma analysis recovered that 92 genes were involved in both upregulated DEGs and high risk of poor prognosis, whereas 36 genes were involved in both downregulated DEGs and low risk of poor prognosis. Pathway enrichment analysis indicated that mTOR signaling pathway and ferroptosis exerted a role in regulating these intersection genes. Moreover, SLC3A2 is a key gene in ferroptosis in laryngeal carcinoma. SLC3A2 is highly expressed in laryngeal carcinoma tissues and cells. Patients with high SLC3A2 expression exerted poor survival. SLC3A2 deficiency inhibited cell proliferation and foci formation. Furthermore, knockdown of SLC3A2 expression induced the efficacy of ferroptosis and suppressed ferroptosis related proteins expression. Mechanically, SLC3A2 deficiency facilitated ferroptosis through upregulating the expression of mTOR and P70S6K, whereas inhibited p-mTOR and p-P70S6K expression in laryngeal carcinoma cells. SLC3A2 deficiency inhibited tumorigenesis in nude mice.

Conclusion

Our study suggests that SLC3A2 negatively regulates ferroptosis through mTOR pathway in laryngeal carcinoma.

LncRNA SNHG6 Silencing Could Arrest Progression of High Grade Colorectal Cancers

BACKGROUND & OBJECTIVE

Colorectal cancer (CRC), like other cancers, needs faster and more accurate identifications. A well-timed prognosis of CRC could be an important turning point in the survival of patients. Supplementary signs, such as long non-coding RNAs (lncRNAs), could be helpful for this purpose. A new possible biomarker for CRC identification is introduced by this study.

METHODS

RNA extraction was performed by the RNX-Plus solution for 64 tumor and non-tumor tissues. Complementary DNAs (cDNAs) were synthesized, and quantitative real-time PCR was performed for relative expression level measurement and the data was analyzed statistically using the Prism 6 software. For Small nucleolar host gene 6 knockdown, siRNA was designed based on Reynolds rules. The cells were cultured in their appropriate media, and the siRNA-lipofectamine complex was formed. The transfection complex was presented for sw48, sw480, and sw1116 as CRC cells with different grades. After transfection, the SNHG6/β actin ratio was determined. Then, the distribution of siRNA-treated cells was determined by the Partec flow cytometer instrument and analyzed by the FloMax software.

RESULTS

SNHG6 was more expressed in CRC tumors than non-tumor tissues. In tumor tissues, SNHG6 upregulation and tumors' grade progression were concurrent. SNHG6 was upregulated in cases with lymphovascular invasion than in cases with perineural invasion. The knockdown of SNHG6 conduced to G1 arrest in CRC cells, more noticeably in high-grade ones.

CONCLUSION

SNHG6 could be applied as a consideration to differentiate tumor and non-tumor tissues and grade definition in colorectal malignancies, and it could participate in colorectal tumor formation as a cell cycle progressive factor.

The heavy chain of 4F2 antigen promote prostate cancer progression via SKP-2

The 4F2 cell-surface antigen heavy chain (4F2hc) forms a heterodimeric complex with L-type amino acid transporter 1 (LAT1) and transports large neutral essential amino acids. However, in contrast to the traditional role of LAT1 in various cancers, the role of 4F2hc has largely remained unknown. The role of 4F2hc in prostate cancer was studied. Treatment of C4-2 cells with si4F2hc was found to suppress cellular growth, migratory and invasive abilities, with this effect occurring through the cell cycle, with a significant decrease in S phase and a significant increase in G0/G1 phase, suggesting cell cycle arrest. In addition, it was proven by RNA seq that the key to 4F2hc’s impact on cancer is SKP2. si4F2hc upregulates the protein expression of cyclin-dependent kinase inhibitors (P21cip1, P27kip1) through the downstream target SKP2. Furthermore, the expression of 4F2hc and LAT1 in prostate cancer cells suggests the importance of 4F2hc. Multivariate analysis showed that high 4F2hc expression was an independent prognostic factor for progression-free survival (HR 11.54, p = 0.0357). High 4F2hc was related to the clinical tumour stage (p = 0.0255) and Gleason score (p = 0.0035). Collectively, 4F2hc contributed significantly to prostate cancer (PC) progression. 4F2hc may be a novel marker and therapeutic target in PC.

xCT-Driven Expression of GPX4 Determines Sensitivity of Breast Cancer Cells to Ferroptosis Inducers

Inducers of ferroptosis such as the glutathione depleting agent Erastin and the GPX4 inhibitor Rsl-3 are being actively explored as potential therapeutics in various cancers, but the factors that determine their sensitivity are poorly understood. Here, we show that expression levels of both subunits of the cystine/glutamate antiporter xCT determine the expression of GPX4 in breast cancer, and that upregulation of the xCT/selenocysteine biosynthesis/GPX4 production axis paradoxically renders the cancer cells more sensitive to certain types of ferroptotic stimuli. We find that GPX4 is strongly upregulated in a subset of breast cancer tissues compared to matched normal samples, and that this is tightly correlated with the increased expression of the xCT subunits SLC7A11 and SLC3A2. Erastin depletes levels of the antioxidant selenoproteins GPX4 and GPX1 in breast cancer cells by inhibiting xCT-dependent extracellular reduction which is required for selenium uptake and selenocysteine biosynthesis. Unexpectedly, while breast cancer cells are resistant compared to nontransformed cells against oxidative stress inducing drugs, at the same time they are hypersensitive to lipid peroxidation and ferroptosis induced by Erastin or Rsl-3, indicating that they are 'addicted' to the xCT/GPX4 axis. Our findings provide a strategic basis for targeting the anti-ferroptotic machinery of breast cancer cells depending on their xCT status, which can be further explored.

Identification of AR-V7 downstream genes commonly targeted by AR/AR-V7 and specifically targeted by AR-V7 in castration resistant prostate cancer

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The entire landscape of AR-V7 target regions/genes in CRPC cells was investigated.

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We identified 78 AR-V7 target genes, targeted specifically by AR-V7 e.g. SLC3A2, or commonly by AR and AR-V7 e.g. NUP210.

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SLC3A2 and NUP210 were markedly upregulated in clinical CRPC tissues, leading to increased proliferation in CRPC.

Primary prostate cancer (PC) progresses to castration-resistant PC (CRPC) under androgen deprivation therapy, by mechanisms e.g. expression of androgen receptor (AR) splice variant-7 (AR-V7). Here we conducted comprehensive epigenome and transcriptome analyses comparing LNCaP, primary PC cells, and LNCaP95, AR-V7-expressing CRPC cells derived from LNCaP. Of 399 AR-V7 target regions identified through ChIP-seq analysis, 377 could be commonly targeted by hormone-stimulated AR, and 22 were specifically targeted by AR-V7. Among genes neighboring to these AR-V7 target regions, 78 genes were highly expressed in LNCaP95, while AR-V7 knockdown led to significant repression of these genes and suppression of growth of LNCaP95. Of the 78 AR-V7 target genes, 74 were common AR/AR-V7 target genes and 4 were specific AR-V7 target genes; their most suppressed genes by AR-V7 knockdown were NUP210 and SLC3A2, respectively, and underwent subsequent analyses. NUP210 and SLC3A2 were significantly upregulated in clinical CRPC tissues, and their knockdown resulted in significant suppression of cellular growth of LNCaP95 through apoptosis and growth arrest. Collectively, AR-V7 contributes to CRPC proliferation by activating both common AR/AR-V7 target and specific AR-V7 target, e.g. NUP210 and SLC3A2.

An Emerging Class of Long Non-coding RNA With Oncogenic Role Arises From the snoRNA Host Genes

The small nucleolar RNA host genes (SNHGs) are a group of long non-coding RNAs, which are reported in many studies as being overexpressed in various cancers. With very few exceptions, the SNHGs (SNHG1, SNHG3, SNHG5, SNHG6, SNHG7, SNHG12, SNHG15, SNHG16, SNHG20) are recognized as inducing increased proliferation, cell cycle progression, invasion, and metastasis of cancer cells, which makes this class of transcripts a viable biomarker for cancer development and aggressiveness. Through our literature research, we also found that silencing of SNHGs through small interfering RNAs or short hairpin RNAs is very effective in both in vitro and in vivo experiments by lowering the aggressiveness of solid cancers. The knockdown of SNHG as a new cancer therapeutic option should be investigated more in the future.

Inhibition of polyamine synthesis and uptake reduces tumor progression and prolongs survival in mouse models of neuroblastoma

Amplification of the MYCN oncogene is associated with an aggressive phenotype and poor outcome in childhood neuroblastoma. Polyamines are highly regulated essential cations that are frequently elevated in cancer cells, and the rate-limiting enzyme in polyamine synthesis, ornithine decarboxylase 1 (ODC1), is a direct transcriptional target of MYCN. Treatment of neuroblastoma cells with the ODC1 inhibitor difluoromethylornithine (DFMO), although a promising therapeutic strategy, is only partially effective at impeding neuroblastoma cell growth due to activation of compensatory mechanisms resulting in increased polyamine uptake from the surrounding microenvironment. In this study, we identified solute carrier family 3 member 2 (SLC3A2) as the key transporter involved in polyamine uptake in neuroblastoma. Knockdown of SLC3A2 in neuroblastoma cells reduced the uptake of the radiolabeled polyamine spermidine, and DFMO treatment increased SLC3A2 protein. In addition, MYCN directly increased polyamine synthesis and promoted neuroblastoma cell proliferation by regulating SLC3A2 and other regulatory components of the polyamine pathway. Inhibiting polyamine uptake with the small-molecule drug AMXT 1501, in combination with DFMO, prevented or delayed tumor development in neuroblastoma-prone mice and extended survival in rodent models of established tumors. Our findings suggest that combining AMXT 1501 and DFMO with standard chemotherapy might be an effective strategy for treating neuroblastoma.

Frontiers of ctDNA, targeted therapies, and immunotherapy in non-small-cell lung cancer

Non-small-cell lung cancer (NSCLC), a main subtype of lung cancer, is one of the most common causes of cancer death in men and women worldwide. Circulating tumor DNA (ctDNA), tyrosine kinase inhibitors (TKIs) and immunotherapy have revolutionized both our understanding of NSCLC, from its diagnosis to targeted NSCLC therapies, and its treatment. ctDNA quantification confers convenience and precision to clinical decision making. Furthermore, the implementation of TKI-based targeted therapy and immunotherapy has significantly improved NSCLC patient quality of life. This review provides an update on the methods of ctDNA detection and its impact on therapeutic strategies; therapies that target epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK) using TKIs such as osimertinib and lorlatinib; the rise of various resistant mechanisms; and the control of programmed cell death-1 (PD-1), programmed cell death ligand-1 (PD-L1), and cytotoxic T-lymphocyte antigen-4 (CTLA-4) by immune checkpoint inhibitors (ICIs) in immunotherapy; blood tumor mutational burden (bTMB) calculated by ctDNA assay as a novel biomarker for immunotherapy. However, NSCLC patients still face many challenges. Further studies and trials are needed to develop more effective drugs or therapies to treat NSCLC.

lncRNA FLVCR-AS1 promotes osteosarcoma growth by targeting miR381-3p/CCND1

Purpose

This article reports on FLVCR-AS1 effects on osteosarcoma (OS) growth.

Methods

Tumor tissue and adjacent normal tissue of 48 OS patients were collected. HOS and 143B cells were transfected. Gene expression was examined with qRT-PCR and Western blot. CCK8 assays and cell cloning was performed to measure cell proliferation. Cell cycle and apoptosis were assessed. Luciferase-reporter gene assays and RNA pull-down tests were used to detect targeting relationships between genes.

Results

Prominently higher FLVCR-AS1 expression was found in OS tissue and cells, and was associated with poor prognosis (P<0.05, P<0.01, or P<0.001). Compared with the siCtrl group, 143B and HOS cells of the siFLVCR-AS1 group had significantly lower OD₄₅₀ values and clone numbers and obviously higher percentages of cells in the G₁ phase and apoptosis (P<0.01 or P<0.001). miR381-3p expression was directly inhibited by FLVCR-AS1, and CCND1 expression was directly suppressed by miR381-3p. Compared with the FLVCR-AS1 group, 143B cells of the FLVCR-AS1⁺ miR381-3p mimic group and FLVCR-AS1⁺ siCCND1 group showed remarkably lower OD₄₅₀ values and clone numbers obviously higher apoptosis and percentage of cells in the G₁ phase (P<0.05, P<0.01, or P<0.001).

Conclusion

FLVCR-AS1 promoted OS growth by upregulating CCND1 expression via downregulation of miR381-3p.

ZEB1 Promotes Chemoresistance to Cisplatin in Ovarian Cancer Cells by Suppressing SLC3A2

Ovarian cancer is one of the deadliest gynecological malignancies in women. Chemoresistance has been a major obstacle for ovarian cancer treatment. Zinc finger E-box-binding homeobox 1 (ZEB1) is an important regulator of tumor development in various types of cancer. Abnormal expression of SLC3A2 (CD98hc), a type 2 transmembrane cell surface molecule, has been described in several cancers. This study was designed to investigate the role of ZEB1 and SLC3A2 in the chemoresistance to cisplatin in ovarian cancer cells. We found that ZEB1 was increased in cisplatin-resistant SKOV3/DPP cells. Downregulation of ZEB1 significantly decreased cell viability in response to cisplatin, increased cis-platin-induced apoptosis, and decreased migration and invasion in the presence of cisplatin. In addition, downregulation of ZEB1 decreased the volume and weight of implanted tumors. SLC3A2 was decreased in cisplatin-resistant SKOV3/DPP cells. Upregulation of SLC3A2 significantly decreased cell viability in response to cisplatin, increased cisplatin-induced apoptosis, and decreased migration and invasion in the presence of cisplatin. Moreover, upregulation of SLC3A2 decreased the volume and weight of implanted tumors. Downregulation of ZEB1 resulted in a significant increase of SLC3A2 expression. Moreover, downregulation of SLC3A2 significantly inhibited ZEB1 knockdown-mediated inhibition of cisplatin-resistance. ZEB1-mediated regulation of SLC3A2 was involved in the chemoresistance to cisplatin in ovarian cancer cells. Overall, we provide new insights into the mechanism of chemoresistance to cisplatin in ovarian cancer cells. ZEB1/SLC3A2 may be promising therapeutic targets for enhancement of the sensitivity of ovarian cancer cells to cisplatin-mediated chemotherapy.

Hypoxia-inducible factor-1 promotes cancer progression through activating AKT/Cyclin D1 signaling pathway in osteosarcoma

OBJECTIVE

Osteosarcoma is an aggressive malignant neoplasm, which commonly afflicts patients of 20-30 years of age, and its morbidity has increased markedly in recent years. Certain genes and signal pathways have been identified to exert key roles in osteosarcoma progression. Here, we set out to characterize in more detail of the role of HIF-1/AKT/Cyclin D1 pathway in the progression of osteosarcoma.

METHODS

Immunohistochemistry, western blot and qPCR were used to test the protein or mRNA levels of HIF-1 in osteosarcoma tissues or adjacent nontumor tissues. MTT, clone formation, wound healing, Transwell, in vivo tumorigenesis, flow cytometry and western blot analysis were used to determine cell proliferation, clone formation ability, migration, invasion, tumorigenesis, and cell apoptosis in MG63 and U2OS cells, respectively. Immunoprecipitation and immunofluorescence assays were performed to investigate the protein-protein interaction between HIF-1α and proteins related to signal pathways.

RESULTS

HIF-1 was overexpressed in osteosarcoma tissues and cell lines, which promoted cell proliferation, clone formation, migration, invasion and inhibited cell apoptosis. Results also demonstrated that HIF-1 combined with AKT, and there might be a positive loop between the two proteins of HIF-1 and AKT, then the protein-protein interaction up-regulated the expression of Cyclin D1 in protein level, but not mRNA level, made Cyclin D1 protein more stable, triggered cell proliferation, clone formation, tumorigenesis, but inhibited cell apoptosis.

CONCLUSIONS

The present study showed that HIF-1 modulated Cyclin D1 expression might through shaping a positive loop with AKT proteins. Additionally, HIF-1α promoted the tumor cells growth, migration and invasion in osteosarcoma through the activation of the AKT/Cyclin D1 signal cascade. We proposed that HIF-1 could be served as a marker for distinguishing osteosarcoma and an effective therapeutic target for osteosarcoma.

The multifunctional solute carrier 3A2 (SLC3A2) confers a poor prognosis in the highly proliferative breast cancer subtypes

Breast cancer (BC) is a heterogeneous disease characterised by variant biology, metabolic activity and patient outcome. This study aimed to evaluate the biological and prognostic value of the membrane solute carrier, SLC3A2 in BC with emphasis on the intrinsic molecular subtypes. SLC3A2 was assessed at the genomic level, using METABRIC data (n = 1980), and at the proteomic level, using immunohistochemistry on tissue microarray (TMA) sections constructed from a large well-characterised primary BC cohort (n = 2500). SLC3A2 expression was correlated with clinicopathological parameters, molecular subtypes and patient outcome. SLC3A2 mRNA and protein expression were strongly correlated with higher tumour grade and poor Nottingham prognostic index (NPI). High expression of SLC3A2 was observed in triple-negative (TN), HER2+ and ER+ high-proliferation subtypes. SLC3A2 mRNA and protein expression were significantly associated with the expression of c-MYC in all BC subtypes (p < 0.001). High expression of SLC3A2 protein was associated with poor patient outcome (p < 0.001), but only in the ER+ high-proliferation (p = 0.01) and TN (p = 0.04) subtypes. In multivariate analysis SLC3A2 protein was an independent risk factor for shorter BC-specific survival (p < 0.001). SLC3A2 appears to play a role in the aggressive BC subtypes driven by MYC and could act as a potential prognostic marker. Functional assessment is necessary to reveal its potential therapeutic value in the different BC subtypes.