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Background: Sunitinib resistance is a major challenge in advanced renal cell carcinoma (RCC). Clinically, elucidating the underlying mechanisms and developing practical countermeasures for sunitinib resistance in RCC is desirable. In previous studies, we found that circAGAP1 expression was significantly upregulated in clear cell RCC (ccRCC) and was strongly associated with poor prognosis. However, the role of circAGAP1 in sunitinib resistance in ccRCC remains unclear. Methods: We used public databases for bioinformatics analysis to identify the binding targets of circAGAP1. Additionally, the effects of circAGAP1 on the proliferation, clonogenesis, apoptosis, and migration of ccRCC cells were analyzed using quantitative real-time PCR, cell counting kit-8 assays, migration and apoptosis assays, and colony formation assays. Furthermore, RNA immunoprecipitation, dual-luciferase reporter, and fluorescence in situ hybridization assays were used to explore the molecular mechanism. Results: In this study, circAGAP1 exhibited higher expression in sunitinib-sensitive ccRCC cells and inhibited the clonogenesis, proliferation, and migration of ccRCC cells after sunitinib treatment. Mechanical studies revealed that circAGAP1 regulated the expression of sunitinib target platelet-derived growth factor receptor by acting as a microRNA sponge that suppresses miR-149-5p, miR-455-5p, and miR-15a-5p simultaneously. Overexpression of these three miRNAs reversed circAGAP1-mediated sunitinib sensitivity in ccRCC. Conclusions: In summary, our findings indicate that circAGAP1 may serve as a promising biomarker to predict sunitinib sensibility and a therapeutic target in ccRCC. [ABSTRACT FROM AUTHOR]

Abstract Background Renal cell carcinoma (RCC) is one of the most diagnosed urological malignancies with high mortality and increasing incidence. What’s more, the sunitinib resistance undoubtedly increased the difficulties in RCC therapy. Circular RNAs (circRNAs) are a newly found type of non-coding RNAs with a special circular structure, and are found to participate in the occurrence development, chemoresistance, and prognosis of cancers. Ferroptosis regulates disease progression mainly via polyunsaturated fatty acid metabolism and glutamine catabolic pathways. The mechanism of circRNAs contributed to sunitinib resistance through ferroptosis has not been elucidated clearly. Materials and methods In our research, we identified a novel circRNA Hsa_circ_0072732 from circRNA datasets (GSE108735 and GSE100186). RNase R and Actinomycin D assays were used to detect the loop structure and stability of circRNAs. qRT-PCR and western blot were used for the detection of RNA and protein levels. CCK8 assays were used to detect proliferation and cell viability. Lipid peroxidation (MDA), and reactive oxygen species (ROS) were detected by indicted kits. Dual-luciferase reporter and RNA pull-down assays were used to detect the RNA interactions. Results Our results showed that Hsa_circ_0072732 was highly expressed in RCC cells. Further investigations showed that the silence of Hsa_circ_0072732 could increase RCC sensitivity to sunitinib. Hsa_circ_0072732 contributed to sunitinib chemoresistance by impairing ferroptosis. Hsa_circ_0072732 exerts its function mainly by acting as sponges for miR-548b-3p and regulating the expression SLC7A11. Our research suggests that ferroptosis is involved in sunitinib resistance, and targeting ferroptosis is a promising way for RCC treatment. Conclusion Our research suggests Hsa_circ_0072732 enhanced renal cell carcinoma sunitinib resistance by inhibiting ferroptosis through miR-548b-3p/SLC7A11.

Background: Renal cell carcinoma (RCC) is one of the most diagnosed urological malignancies with high mortality and increasing incidence. What's more, the sunitinib resistance undoubtedly increased the difficulties in RCC therapy. Circular RNAs (circRNAs) are a newly found type of non-coding RNAs with a special circular structure, and are found to participate in the occurrence development, chemoresistance, and prognosis of cancers. Ferroptosis regulates disease progression mainly via polyunsaturated fatty acid metabolism and glutamine catabolic pathways. The mechanism of circRNAs contributed to sunitinib resistance through ferroptosis has not been elucidated clearly. Materials and methods: In our research, we identified a novel circRNA Hsa_circ_0072732 from circRNA datasets (GSE108735 and GSE100186). RNase R and Actinomycin D assays were used to detect the loop structure and stability of circRNAs. qRT-PCR and western blot were used for the detection of RNA and protein levels. CCK8 assays were used to detect proliferation and cell viability. Lipid peroxidation (MDA), and reactive oxygen species (ROS) were detected by indicted kits. Dual-luciferase reporter and RNA pull-down assays were used to detect the RNA interactions. Results: Our results showed that Hsa_circ_0072732 was highly expressed in RCC cells. Further investigations showed that the silence of Hsa_circ_0072732 could increase RCC sensitivity to sunitinib. Hsa_circ_0072732 contributed to sunitinib chemoresistance by impairing ferroptosis. Hsa_circ_0072732 exerts its function mainly by acting as sponges for miR-548b-3p and regulating the expression SLC7A11. Our research suggests that ferroptosis is involved in sunitinib resistance, and targeting ferroptosis is a promising way for RCC treatment. Conclusion: Our research suggests Hsa_circ_0072732 enhanced renal cell carcinoma sunitinib resistance by inhibiting ferroptosis through miR-548b-3p/SLC7A11. [ABSTRACT FROM AUTHOR]

Objective: To establish a renal cell carcinoma sunitinib-resistant cell line and to explore the mechanism by which protein disulfide isomerase A4 (PDIA4) regulates sunitinib resistance in renal cell carcinoma. Methods: A small-dose intermittent induction method was used to establish 786-O and OS-RC-2 resistant cell lines (786-OR and OS-RC-2R), qRT-PCR and Western blot were used to detect the expression of PDIA4 in drug-resistant renal carcinoma cell lines and non-drug-resistant renal carcinoma cell lines, and lentiviral infection was used to construct a stable overexpression or knockdown renal carcinoma cell line of PDIA4. The effect of PDIA4 on the proliferation of renal cancer cells was detected by CCK-8 assay; the expression of apoptosis-related proteins BCL2, BAX, Caspase3, Cleaved-Caspase3, and Caspase9 was detected by RT-qPCR and Western blot. Results: Compared with the control group of parental cells 786-O and OS-RC-2, the PDIA4 expression levels of drug-resistant cell lines 786-OR and OS-RC-2R are significantly increased (P<0.05). Overexpression of PDIA4 promoted the growth and viability of renal cancer cells as well as decreased the sensitivity of renal cancer cells to sunitinib (P<0.05), whereas knockdown of PDIA4 inhibited the growth and viability of renal cancer cells as well as elevated the sensitivity of renal cancer cells to sunitinib (P<0.05). In addition, overexpression of PDIA4 inhibited the expression of pro-apoptotic proteins (P<0.05), while knockdown of PDIA4 promoted the expression of pro-apoptotic proteins (P<0.05). Conclusion: PDIA4 is associated with sunitinib resistance in renal cell carcinoma by the mechanism of inhibition of apoptosis causing sunitinib resistance in renal cell carcinoma, and targeting PDIA4 reverses the resistance. [ABSTRACT FROM AUTHOR]

Abstract Glycolysis-related metabolic reprogramming is a central hallmark of human cancers, especially in renal cell carcinoma. However, the regulatory function of glycolytic signature in papillary RCC has not been well elucidated. In the present study, the glycolysis-immune predictive signature was constructed and validated using WGCNA, glycolysis-immune clustering analysis. PPI network of DEGs was constructed and visualized. Functional enrichments and patients’ overall survival were analyzed. QRT-PCR experiments were performed to detect hub genes’ expression and distribution, siRNA technology was used to silence targeted genes; cell proliferation and migration assays were applied to evaluate the biological function. Glucose concentration, lactate secretion, and ATP production were measured. Glycolysis-Immune Related Prognostic Index (GIRPI) was constructed and combined analyzed with single-cell RNA-seq. High-GIRPI signature predicted significantly poorer outcomes and relevant clinical features of pRCC patients. Moreover, GIRPI also participated in several pathways, which affected tumor immune microenvironment and provided potential therapeutic strategy. As a key glycolysis regulator, PFKFB3 could promote renal cancer cell proliferation and migration in vitro. Blocking of PFKFB3 by selective inhibitor PFK-015 or glycolytic inhibitor 2-DG significantly restrained renal cancer cells’ neoplastic potential. PFK-015 and sunitinib could synergistically inhibit pRCC cells proliferation. Glycolysis-Immune Risk Signature is closely associated with pRCC prognosis, progression, immune infiltration, and therapeutic response. PFKFB3 may serve as a pivotal glycolysis regulator and mediates Sunitinib resistance in pRCC patients.

Glycolysis-related metabolic reprogramming is a central hallmark of human cancers, especially in renal cell carcinoma. However, the regulatory function of glycolytic signature in papillary RCC has not been well elucidated. In the present study, the glycolysis-immune predictive signature was constructed and validated using WGCNA, glycolysis-immune clustering analysis. PPI network of DEGs was constructed and visualized. Functional enrichments and patients' overall survival were analyzed. QRT-PCR experiments were performed to detect hub genes' expression and distribution, siRNA technology was used to silence targeted genes; cell proliferation and migration assays were applied to evaluate the biological function. Glucose concentration, lactate secretion, and ATP production were measured. Glycolysis-Immune Related Prognostic Index (GIRPI) was constructed and combined analyzed with single-cell RNA-seq. High-GIRPI signature predicted significantly poorer outcomes and relevant clinical features of pRCC patients. Moreover, GIRPI also participated in several pathways, which affected tumor immune microenvironment and provided potential therapeutic strategy. As a key glycolysis regulator, PFKFB3 could promote renal cancer cell proliferation and migration in vitro. Blocking of PFKFB3 by selective inhibitor PFK-015 or glycolytic inhibitor 2-DG significantly restrained renal cancer cells' neoplastic potential. PFK-015 and sunitinib could synergistically inhibit pRCC cells proliferation. Glycolysis-Immune Risk Signature is closely associated with pRCC prognosis, progression, immune infiltration, and therapeutic response. PFKFB3 may serve as a pivotal glycolysis regulator and mediates Sunitinib resistance in pRCC patients. [ABSTRACT FROM AUTHOR]

Cuproptosis, a new type of copper‐induced cell death, is involved in the antitumor activity and resistance of multiple chemotherapeutic drugs. Our previous study revealed that adrenomedullin (ADM) was engaged in sunitinib resistance in clear cell renal cell carcinoma (ccRCC). However, it has yet to be investigated whether and how ADM regulates sunitinib resistance by cuproptosis. This study found that the ADM expression was elevated in sunitinib‐resistant ccRCC tissues and cells. Furthermore, the upregulation of ADM significantly enhanced the chemoresistance of sunitinib compared with their respective control. Moreover, cuproptosis was involved in ADM‐regulated sunitinib resistance by inhibiting mammalian ferredoxin 1 (FDX1) expression. Mechanically, the upregulated ADM activates the p38/MAPK signaling pathway to promote Forkhead box O3 (FOXO3) phosphorylation and its entry into the nucleus. Consequently, the increased FOXO3 in the nucleus inhibited FDX1 transcription and cell cuproptosis, promoting chemoresistance. Collectively, cuproptosis has a critical effector role in ccRCC progress and chemoresistance and thus is a relevant target to eradicate the cell population of sunitinib resistance. [ABSTRACT FROM AUTHOR]

Multitargeted receptor tyrosine kinase inhibitors, including vascular endothelial growth factor (VEGF) inhibitors, such as sunitinib, have been used as the primary targeted agents for patients with recurrent or distant metastasis of advanced renal cell carcinoma (RCC). However, endogenous or acquired sunitinib resistance has become a significant therapeutic problem. Therefore, we focused on mechanisms of sunitinib resistance in RCC. First, we undertook RNA sequencing analysis using previously established sunitinib‐resistant RCC (SUR‐Caki1, SUR‐ACHN, and SUR‐A498) cells. The results showed increased expression of secretogranin II (SCG2, chromogranin C) in SUR‐RCC cells compared to parental cells. The Cancer Genome Atlas database showed that SCG2 expression was increased in RCC compared to normal renal cells. In addition, the survival rate of the SCG2 high‐expression group was significantly lower than that of the RCC low‐expression group. Thus, we investigated the involvement of SCG2 in sunitinib‐resistant RCC. In vitro analysis showed that migratory and invasive abilities were suppressed by SCG2 knockdown SUR cells. As SCG2 was previously reported to be associated with angiogenesis, we undertook a tube formation assay. The results showed that suppression of SCG2 inhibited angiogenesis. Furthermore, coimmunoprecipitation assays revealed a direct interaction between SCG2 and hypoxia‐inducible factor 1α (HIF1α). Expression levels of VEGF‐A and VEGF‐C downstream of HIF1α were found to be decreased in SCG2 knockdown SUR cells. In conclusion, SCG2 could be associated with sunitinib resistance through VEGF regulation in RCC cells. These findings could lead to a better understanding of the VHL/HIF/VEGF pathway and the development of new therapeutic strategies for sunitinib‐resistant RCC. This article showed increased expression of secretogranin II (SCG2, chromogranin C) in sunitinib‐resistant renal cell carcinoma. Suppression of SCG2 inhibited angiogenesis, and a direct interaction between SCG2 and hypoxia‐inducible factor 1α was indicated. [ABSTRACT FROM AUTHOR]

The tyrosine kinase inhibitor (TKI) cabozantinib might impede the growth of the sunitinib-resistant cell lines by targeting MET and AXL overexpression in metastatic renal cell carcinoma (mRCC). We studied the role of MET and AXL in the response to cabozantinib, particularly following long-term administration with sunitinib. Two sunitinib-resistant cell lines, 786-O/S and Caki-2/S, and the matching 786-O/WT and Caki-2/WT cells were exposed to cabozantinib. The drug response was cell-line-specific. The 786-O/S cells were less growth-inhibited by cabozantinib than 786-O/WT cells (p-value = 0.02). In 786-O/S cells, the high level of phosphorylation of MET and AXL was not affected by cabozantinib. Despite cabozantinib hampering the high constitutive phosphorylation of MET, the Caki-2 cells showed low sensitivity to cabozantinib, and this was independent of sunitinib pretreatment. In both sunitinib-resistant cell lines, cabozantinib increased Src-FAK activation and impeded mTOR expression. The modulation of ERK and AKT was cell-line-specific, mirroring the heterogeneity among the patients. Overall, the MET- and AXL-driven status did not affect cell responsiveness to cabozantinib in the second-line treatment. The activation of Src-FAK might counteract cabozantinib activity and contribute to tumor survival and may be considered an early indicator of therapy response. [ABSTRACT FROM AUTHOR]

Objective To investigate the expression level of circTMBIM6 in sunitinib-resistant renal carcinoma (RCC）cells and to explore its relationship with miR-19a-3p/PPARα axis. Methods The expression of TMBIM6 in suni⁃ tinib-resistant RCC cell lines A498, Caci-1 and 780-O was detected by qRT-PCR. The STARBASE and Target scan databases were used to predict the complementary binding of miR-19a-3p to the 3'untranslated region (3'UTR）of circTMBIM6 mRNA and the 3'UTR of PPARα mRNA. The wild-type and mutant circTMBIM6 mRNA 3'UTR double fluorescence re⁃ porter plasmids containing binding sites were constructed. 786-O cells were co-transfected with circTMBIM6-WT, circTM⁃ BIM6-MUT, miR-19a-3p mimics, or miR-NC negative control. At the same time, PPARα-WT, PPARα-MUT and miR- 19a-3p mimics or miR-NC negative control were co-transfected into 786-O cells to construct the wild-type and mutant PPARα mRNA 3'UTR double fluorescence reporter plasmids. The effects of miR-19a-3p on the activities of circTMBIM6 3'UTR and PPARα mRNA 3'UTR luciferase reporter gene were detected. The si-circTMBIM6 and si-NC+miR-NC nega⁃ tive control were co-transfected into A498, Caci-1 and 780-O cells. The three types of renal carcinoma cells were divided into the si-circTMBIM6 (down-regulated group）and si-NC+miR-NC group (control group). The expression of miR-19a-3p in the above three cell lines was detected by qPCR. These three kinds of cells were divided into the miR-19a-3p overex⁃ pression group, miR-19a-3p inhibitor group, and control group, which were transfected with miR-19a-3p mimics, miR- 19a-3p inhibitor and si-NC+miR-NC negative control, respectively. The expression of PPARα mRNA and protein was de⁃ tected by qRT-PCR and Western blotting. These three kinds of renal carcinoma cells were divided into the negative control group, miR-19a-3p inhibitor group, and circTMBIM6 inhibitor group, which were transfected with si-NC+miR-NC nega⁃ tive control, si-NC+miR-19a-3p inhibitor, and si-circTMBIM, respectively. RT-PCR and Western blotting were used to detect the expression levels of PPARα mRNA and protein and further to verify that circTMBIM6 regulated the expression of PPARα through miR-19a-3p. CCK-8 assay was used to detect the inhibition rate of cell proliferation in each group, and we observed the regulatory effects of circTMBIM6 and miR-19a-3p/PPARα axis in sunitinib-resistant renal carcinoma cells. Results In comparison with normal RCC cells, the expression level of circTMBIM6 in the sunitinib-resistant RCC cells was up-regulated (all P<0. 01). Bioinformatics analysis predicted that miR-19a-3p had potential complementary binding sites with the 3'UTR of circTMBIM6 and the 3'UTR of PPARα mRNA. Dual luciferase reporter gene assay reported that the luciferase activity of the circTMBIM6 wild-type 3'UTR in the miR-19a-3p mimics group was lower than that in the miRNC group (all P<0. 05）, but there was no significant change in the luciferase activity of the circTMBIM6 MUT 3'UTR in the miR-19a-3p mimics group and miR-NC group. In these three kinds of RCC cells A498, Caci-1, and 780-O, the ex⁃ pression of miR-19a-3p in the si-circTMBIM6 group was higher than that in si-NC+miR-NC group (all P<0. 05); the rela⁃ tive expression levels of PPARα mRNA and protein in the miR-19a-3p inhibitor group were higher than those in the nega⁃ tive control group, and those in the circTMBIM6 inhibitor group were lower than those of the negative control group (all P< 0. 05). CCK-8 assay showed that the inhibition rate of cell proliferation in the circTMBIM6 inhibitor group was lower than that of the negative control group, and that of the miR-19a-3p inhibitor group was higher than that of negative control group (all P<0. 05). Conclusion CircTMBIM6 expression level increases in sunitinib-resistant RCC cells, and circTMBIM6 regulates the expression of PPARα through sponge absorption of miR-19a-3p, which reduces the sensitivity of RCC cells to sunitinib and leads to drug resistance. [ABSTRACT FROM AUTHOR]

Sunitinib is an effective treatment for patients with metastatic Renal Cell Carcinoma (mRCC) but ultimately resistance occurs. The aim of this study was to investigate sunitinib resistance in RCCs and to develop therapeutic combination strategies with targeted radioimmunotherapy (RIT).We studied two RCC models, analyzed Vascular endothelial growth factor (VEGF) and its receptor (VEGFR) and AXL/MET expression and performed therapy studies in Balb/cnu/nu mice combining sunitinib and [177Lu]Lu-cG250 RIT (6.5 MBq/10 μg), specifically targeting RCC cells.pAXL and pMET were expressed in sunitinib-resistant SK-RC-52 and absent in sunitinib-sensitive NU12. NGS evaluation showed that expression of VEGFA, VEGFB, VEGFD, PGF and VEGFR1,2,3 was higher and expression of VEGFC and PDGFA was lower in NU12 than in SK-RC-52.Therapy studies combining sunitinib with [177Lu]Lu-cG250 RIT showed that the best response in mice with “resistant” SK-RC-52 tumors was observed with two cycles of Sunitinib and [177Lu]Lu-cG250 RIT, probably due to increased vascular permeability by sunitinib treatment. In the “sensitive” NU12 model, two cycles of [177Lu]Lu-cG250 RIT and two cycles of combination treatment were equally effective.Enhanced therapeutic efficacy was achieved when two agents ([177Lu]Lu-cG250 RIT and sunitinib) that on their own did not induce satisfactory response levels, are combined. Our findings provide a promising new therapeutic strategy for patients with advanced RCC.

Sunitinib is one of the first-line multi-tyrosine kinase inhibitors for metastatic renal cell carcinoma, and resistance to sunitinib continues to be a limiting factor for the successful treatment. As interleukin-6 (IL-6) is overexpressed in sunitinib-resistant cells, the purpose of this study was to explore the potential of IL-6 inhibition with tocilizumab, an IL-6 receptor inhibitor, to overcome resistance. In vitro, two sunitinib-resistant renal cell carcinoma cell lines (Caki-1 and SN12K1) were treated with tocilizumab. A mouse subcutaneous xenograft model was also used. Cell viability was studied by MTT assay, and apoptosis by morphology and ApopTag. Expression of IL-6, vascular endothelial growth factor (VEGF), and Bcl-2 was analyzed by qPCR. In vitro, tocilizumab induced significant cell death, and reduced the expression of IL-6, VEGF, and Bcl-2 in sunitinib-resistant cells. However, the in vitro findings could not be successfully translated in vivo, as tocilizumab did not decrease the growth of the tumors. • Interleukin-6 confers resistance to sunitinib in metastatic renal cell carcinoma. • Inhibition of interlukin-6 with tocilizumab could overcome resistance. • In vitro, tocilizumab overcame resistance to sunitinib and reduced interleukin-6. • In vivo, interleukin-6 inhibition did not reduce tumor growth. • Also, upregulation of interleukin-6 did not increase tumor growth in vivo. [ABSTRACT FROM AUTHOR]

Sunitinib resistance is a major challenge in systemic therapy for renal cell carcinoma (RCC). The role of circular RNAs (circRNAs) in regulating sunitinib resistance of RCC is largely unknown. We established sunitinib-resistant RCC cell lines in vivo. Through RNA-sequencing, we identified circSNX6, whose expression is upregulated in sunitinib-resistant cells compared with their parental cells. High circSNX6 expression was correlated with sunitinib resistance and worse oncologic outcomes in a cohort of 81 RCC patients. In vitro and in vivo experiments confirmed that circSNX6 could promote sunitinib resistance in RCC. circSNX6 acts as a molecular "sponge" to relieve the suppressive effect of microRNA (miR)-1184 on its target gene, glycerophosphocholine phosphodiesterase 1 (GPCPD1), which increases intracellular lysophosphatidic acid (LPA) levels and, ultimately, promotes sunitinib resistance in RCC cells. Our findings demonstrated that the circSNX6/miR-1184/GPCPD1 axis had a critical role in regulation of intracellular LPA levels and sunitinib resistance in RCC; they also provide a novel prognostic indicator and promising therapeutic targets. [ABSTRACT FROM AUTHOR]

BackgroundAntiangiogenic agents that specifically target vascular endothelial growth factor receptor (VEGFR), such as sunitinib, have been utilized as the standard therapy for metastatic clear cell renal cell carcinoma (ccRCC) patients. However, most patients eventually show no responses to the targeted drugs, and the mechanisms for the resistance remain unclear. This study is aimed to identify pivotal molecules and to uncover their potential functions involved in this adverse event in ccRCC treatment.MethodsTwo datasets, GSE64052 and GSE76068, were obtained from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) were identified using the limma package in R software. The gene set enrichment analysis (GSEA) was conducted using clusterProfiler package. A protein–protein interaction (PPI) network was built using the STRING database and Cytoscape software. Kaplan—Meier survival curves were plotted using R software. qRT-PCR and Western blotting were used to detect the MX2 and pathway expression in RCC cell lines. Sunitinib-resistant cell lines were constructed, and loss-of-function experiments were conducted by knocking down MX2. All statistical analyses were performed using R version 3.6.1 and SPSS 23.0.ResultsA total of 760 DEGs were derived from two datasets in GEO database, and five hub genes were identified, among which high-level MX2 exhibited a pronounced correlation with poor overall survival (OS) in sunitinib-resistant ccRCC patients. Clinical correlation analysis and Gene Set Variation Analysis (GSVA) on MX2 showed that the upregulation of MX2 was significantly related to the malignant phenotype of ccRCC, and it was involved in several pathways and biological processes associated with anticancer drug resistance. qRT-PCR and Western blotting revealed that MX2 was distinctly upregulated in sunitinib-resistant RCC cell lines. Colony formation assay and Cell Counting Kit-8 (CCK8) assay showed that MX2 strongly promoted resistant capability to sunitinib of ccRCC cells.ConclusionMX2 is a potent indicator for sunitinib resistance and a therapeutic target in ccRCC patients.

Background: Antiangiogenic agents that specifically target vascular endothelial growth factor receptor (VEGFR), such as sunitinib, have been utilized as the standard therapy for metastatic clear cell renal cell carcinoma (ccRCC) patients. However, most patients eventually show no responses to the targeted drugs, and the mechanisms for the resistance remain unclear. This study is aimed to identify pivotal molecules and to uncover their potential functions involved in this adverse event in ccRCC treatment. Methods: Two datasets, GSE64052 and GSE76068, were obtained from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) were identified using the limma package in R software. The gene set enrichment analysis (GSEA) was conducted using clusterProfiler package. A protein–protein interaction (PPI) network was built using the STRING database and Cytoscape software. Kaplan—Meier survival curves were plotted using R software. qRT-PCR and Western blotting were used to detect the MX2 and pathway expression in RCC cell lines. Sunitinib-resistant cell lines were constructed, and loss-of-function experiments were conducted by knocking down MX2. All statistical analyses were performed using R version 3.6.1 and SPSS 23.0. Results: A total of 760 DEGs were derived from two datasets in GEO database, and five hub genes were identified, among which high-level MX2 exhibited a pronounced correlation with poor overall survival (OS) in sunitinib-resistant ccRCC patients. Clinical correlation analysis and Gene Set Variation Analysis (GSVA) on MX2 showed that the upregulation of MX2 was significantly related to the malignant phenotype of ccRCC, and it was involved in several pathways and biological processes associated with anticancer drug resistance. qRT-PCR and Western blotting revealed that MX2 was distinctly upregulated in sunitinib-resistant RCC cell lines. Colony formation assay and Cell Counting Kit-8 (CCK8) assay showed that MX2 strongly promoted resistant capability to sunitinib of ccRCC cells. Conclusion: MX2 is a potent indicator for sunitinib resistance and a therapeutic target in ccRCC patients. [ABSTRACT FROM AUTHOR]

Background: Metastatic renal cell carcinoma (RCC) often develops resistance to first-line targeted therapy such as sunitinib. G-Protein-coupled estrogen receptor 1 (GPER1) agonist G-1 was recently reported to regulate RCC physiology but the role of G-1 in RCC tumorigenesis and sunitinib resistance remains largely unknown. Materials and Methods: Parental and sunitinib-resistant 786-O cells were treated with GPER1 agonist G-1, and quantitative phosphoproteomics was performed. Bioinformatic analyses and validations, including immunoblotting, cell migration, and cell cycle distribution, were performed. Results: G-1 repressed cell proliferation and migration in both parental and sunitinib-resistant 786-O cells. Phosphoproteomic signatures, including phosphoinositide 3-kinase and protein kinase B (PI3K-AKT) as well as other pathways, were upregulated in sunitinib-resistant cells but application of G-1 reversed this effect. Among phosphoprotein candidates, activating transcription factor 2 (ATF2) Thr69/71 phosphorylation was antagonistically regulated by sunitinib resistance and G-1. Conclusion: Our results open up the possibility for managing RCC and sunitinib resistance by GPER1 agonist G-1 and its regulated pathways. [ABSTRACT FROM AUTHOR]

Long non-coding RNA metastasis associated with lung adenocarcinoma transcript 1 (MALAT1) contributes to chemotherapy resistance in some cancers, but the role of MALAT1 in sunitinib (SU) chemoresistance of carcinoma (RCC) is still unknown. In this study, MALAT1 expression in SU-resistance tumor tissues and cells was tested by qRT-PCR. Then, CCK-8, Annexin V-FITC/PI, transwell, and Western blotting assays were used to evaluate cell viability and IC50, apoptosis, cell invasion, and resistance of SU-resistance RCC cells after transfected with small interfering RNA against MALAT1. Further, RNA pull-down and luciferase reporter assay were applied to investigate the underlying mechanism of MALAT1 in SU resistance. The results showed that MALAT1 expression was dramatically upregulated in SU-resistance RCC tissues and cell lines. Knockdown of MALAT1 inhibited proliferation, invasion, and SU chemoresistance, but induced apoptosis in RCC cells. The results of RNA pull-down and luciferase reporter assay indicated that MALAT1 could interact with miR-362-3p and miR-362-3p interact with RasGAP SH3-domain-Binding Protein 1 (G3BP1). Moreover, G3BP1 also played a role in SU chemoresistance of RCC cells, and MALAT1 could perform as a miR-362-3p sponge to modulate G3BP1 expression. Rescue experiments suggested that downregulation of miR-362-3p and overexpression of G3BP1 can reverse the SU chemosensitivity of MALAT1 knockdown in RCC cells. In conclusion, depletion of LncRNA MALAT1 inhibited SU chemoresistance through modulating G3BP1 via sponging miR-362-3p in RCC cells, suggesting that targeting MALAT1 may be a potential therapeutic strategy for SU-resistance RCC. [ABSTRACT FROM AUTHOR]

Tumor resistance to tyrosine kinase inhibitors (TKIs) is an inexorable clinical event. The manipulation of adaptive changes in cancer cells while inhibiting the signaling pathways could be an effective strategy for overcoming TKI resistance toward reducing tumor relapse and prolonging survival. Here, we tested this approach by using polymeric nanomedicines delivering the pan-kinase inhibitor staurosporine (STS) to treat renal cell carcinoma (RCC) resistant to the multi-targeted TKI sunitinib. STS blocked the activity of TKI-resistant protein kinases and strongly inhibited adaptive dynamics in RCC cells promoted by MDR1 and GLUT1 to overcome sunitinib resistance. Co-delivery of STS and epirubicin directed to eliminate fast-proliferating cancer cells through the same nanomedicine platform enabled safe and potent in vivo efficacy in mouse models of RCC, overcoming sunitinib resistance and suppressing the development of metastasis. These results indicate our approach as a promising strategy for effectively managing TKI resistance. Unlabelled Image • PTEN- renal cell carcinoma (RCC) is resistant to tyrosine kinase inhibitors (TKIs) through high levels of GLUT1 and MDR1. • Staurosporine (STS) blocks TKI-resistant protein kinases and inhibits MDR1 and GLUT1 to overcome sunitinib resistance. • Including STS in nanomedicines potentiates the efficacy in orthotopic and metastatic RCC, overcoming sunitinib resistance. [ABSTRACT FROM AUTHOR]

Sunitinib, a multitargeted receptor tyrosine kinase inhibitor including vascular endothelial growth factor, has been widely used as a first‐line treatment against metastatic renal cell carcinoma (mRCC). However, mRCC often acquires resistance to sunitinib, rendering it difficult to treat with this agent. Recently, Rapalink‐1, a drug that links rapamycin and the mTOR kinase inhibitor MLN0128, has been developed with excellent therapeutic effects against breast cancer cells carrying mTOR resistance mutations. The aim of the present study was to evaluate the in vitro and in vivo therapeutic efficacy of Rapalink‐1 against renal cell carcinoma (RCC) compared to temsirolimus, which is commonly used as a small molecule inhibitor of mTOR and is a derivative of rapamycin. In comparison with temsirolimus, Rapalink‐1 showed significantly greater effects against proliferation, migration, invasion and cFolony formation in sunitinib‐naïve RCC cells. Inhibition was achieved through suppression of the phosphorylation of substrates in the mTOR signal pathway, such as p70S6K, eukaryotic translation initiation factor 4E‐binding protein 1 (4EBP1) and AKT. In addition, Rapalink‐1 had greater tumor suppressive effects than temsirolimus against the sunitinib‐resistant 786‐o cell line (SU‐R 786‐o), which we had previously established, as well as 3 additional SU‐R cell lines established here. RNA sequencing showed that Rapalink‐1 suppressed not only the mTOR signaling pathway but also a part of the MAPK signaling pathway, the ErbB signaling pathway and ABC transporters that were associated with resistance to several drugs. Our study suggests the possibility of a new treatment option for patients with RCC that is either sunitinib‐sensitive or sunitinib‐resistant. [ABSTRACT FROM AUTHOR]

Introduction: Renal cell carcinoma (RCC) is one of the most common malignant tumors of the urinary system and accounts for more than 90 % of all renal tumors. Resistance to targeted therapy has emerged as a pivotal factor that contributes to the progressive deterioration of patients with advanced RCC. Metabolic reprogramming is a hallmark of tumorigenesis and progression, with an increasing body of evidence indicating that abnormal lipid metabolism plays a crucial role in the advancement of renal clear cell carcinoma., Objectives: Clarify the precise mechanisms underlying abnormal lipid metabolism and drug resistance., Methods: Bioinformatics screening and analyses were performed to identify hub gene. qRT-PCR, western blot, chromatin immunoprecipitation (ChIP) assays, and other biological methods were used to explore and verify related pathways. Various cell line models and animal models were used to perform biological functional experiments., Results: In this study, we identified Mesoderm induction early response 2 (MIER2) as a novel biomarker for RCC, demonstrating its role in promoting malignancy and sunitinib resistance by influencing lipid metabolism in RCC. Mechanistically, MIER2 facilitated P53 deacetylation by binding to HDAC1. Acetylation modification augmented the DNA-binding stability and transcriptional function of P53, while deacetylation of P53 hindered the transcriptional process of PGC1A, leading to intracellular lipid accumulation in RCC. Furthermore, Trichostatin A (TSA), an inhibitor of HDAC1, was found to impede the MIER2/HDAC1/P53/PGC1A pathway, offering potential benefits for patients with sunitinib-resistant renal cell cancer., Conclusion: Our findings highlight MIER2 as a key player in anchoring HDAC1 and inhibiting PGC1A expression through the deacetylation of P53, thereby inducing lipid accumulation in RCC and promoting drug resistance. Lipid-rich RCC cells compensate for energy production and sustain their own growth in a glycolysis-independent manner, evading the cytotoxic effects of targeted drugs and ultimately culminating in the development of drug resistance., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Production and hosting by Elsevier B.V.)

The current study investigated the mechanism underlying sunitinib resistance. The parental human renal cell carcinoma (RCC) cell line 786-O was continuously exposed to various doses of sunitinib to obtain sunitinib-resistant cells (786-O/S). Cell proliferation and colony formation assays were performed to assess the survival of 786-O/S cells. The half-inhibitory concentration for the drug-resistant cells was calculated. 786-O/S cells demonstrated notably morphological changes compared with parental cells. Compared with 786-O cells, 786-O/S cells exhibited stronger proliferative and colony-forming abilities. Western blot analysis was performed to measure the levels of cyclooxygenase 2 (COX-2) and prostaglandin E2 (PGE2). Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of COX-2 and cluster of differentiation (CD) 133 in both 786-O and 786-O/S cells. Following incubation of the two cell lines with celecoxib, a COX-2 inhibitor, RT-qPCR was performed to detect the expression of COX-2 and CD133, and western blot analysis was used to assess the expression of CD133. The results revealed that the levels of COX-2 and PGE2 were significantly higher in 786-O/S cells compared with 786-O cells (P<0.01). Similarly, the expression of CD133 was 24-fold higher in 786-O/S compared with the parental cells (P<0.01). When celecoxib was incubated with the two cell lines, the expression of COX-2 and CD133 decreased significantly (P<0.0001). In summary, the results indicate that activation of the COX-2-PGE2 pathway in RCC leads to the development of sunitinib resistance and may serve an important role in the maintenance of the characteristics of stem cells that are closely associated with drug resistance. [ABSTRACT FROM AUTHOR]

Context: Sunitinib is the first-line targeted therapy for metastatic renal cell carcinoma (RCC). However, resistance to sunitinib often occurred in patients receiving sunitinib treatment. On the other hand, 17-beta-estradiol (estrogen or E2) has been demonstrated to repress RCC growth in vitro, whether E2 can also affect the growth of sunitinib-resistant RCC remains unknown. Aims: In this study, the role of E2 in inhibiting sunitinib-resistant RCC growth and the underlining acting mechanisms was explored. Settings and Design: Sunitinib resistance was first induced in vitro in ACHN cells. The effect of E2 on cellular growth was then assayed. Label-free phosphoproteomics was also conducted. Subjects and Methods: ACHN cells were first challenged with 10-μM sunitinib up to 4 months to induce drug resistance. Then, E2 at different concentrations were tested in both parental and sunitinib-resistant ACHN cells. To conduct phosphoproteomics study, the total cell lysates from E2-treated ACHN cells were harvested, trypsin digested, and the phosphopeptides were enriched by Fe-IMAC. Statistical Analysis Used: For comparing the E2-induced cell growth inhibition, Student's t-test was used, and P < 0.05 was considered statistically significant. As for label-free phosphoproteomics, false discovery rate <0.01 and phosphosite possibility >0.75 were considered as positive identifications. Results: E2 at the physiological concentration, that is, 10 nM, can repress the cell growth in both parental and sunitinib-resistant ACHN cells. Further, label-free phosphoproteomics revealed that transforming growth factor beta (TGF-β) pathway, cell cycle, and cytoskeleton bindings were enhanced in sunitinib-resistant cells but can be reduced by E2 treatment. On the other hand, programmed cell death and apoptosis were repressed in sunitinib-resistant cells, and E2 at 10 nM did not reverse the effect. We further validated the expression of SMAD3, an important molecule in TGF-β pathway, and found that SMAD3 decreased in sunitinib-resistant cells but can be upregulated by E2 treatment. Conclusions: Our study demonstrated that E2 can inhibit the cell growth in sunitinib-resistant RCC cells at physiological concentration by upregulating SMAD3 in the TGF-β pathway, which may lead to growth inhibition in RCC. [ABSTRACT FROM AUTHOR]

Sphingosine kinase 1 (SphK1) is the major source of the bioactive lipid and GPCR agonist sphingosine 1-phosphate (S1P). Although alterations in SphK1 expression and activity have been detected in various human malignancies, its potential molecular mechanisms in the development and sunitinib resistance of clear cell renal cell carcinoma (ccRCC) remain obscure. In this study, we aim to evaluate the clinical significance of SphK1 and to explore the therapeutic implications of combination approach for ccRCC patients. We identify upregulation of SphK1 significantly associated with poor prognosis of large cohort of ccRCC patients, which contributing to cell proliferation, colony formation, migration and survival. Suppression of SphK1 activity either by shRNA or pharmacologic inhibitior FTY720 suppresses cell growth in vitro and in vivo. A comprehensive phosphoprotein antibody array reveals that SphK1 overexpression promoted RCC progression by regulating the Akt/mTOR pathway. Moreover, FTY720 administration enhanced tumor growth inhibition effect of sunitinib treatment on RCC cells in vitro and in vivo. Our results unraveled that increased SphK1 kinase activation defines an important mechanism for sunitinib resistance, therefore contributes to tumour development and represents therapeutic targets for ccRCC.

Sunitinib resistance is a major clinical problem hampering the treatment of renal cell carcinoma (RCC). Studies on the comprehensive characterisation of morphological, functional and molecular changes in sunitinib-resistant RCC cells are lacking. The aim of the current study was to develop sunitinib resistance in four human RCC cell lines (786-0, Caki-1, Caki-2 and SN12K1), and to characterise the changed cell biology with sunitinib resistance. RCC cells were made resistant by continuous, chronic exposure to 10 µM of sunitinib over a period of 12 months. Cell proliferation, morphology, transmigration, and gene expression for interleukin-6 (IL-6), interleukin-8 (IL-8), vascular endothelial growth factor (VEGF), Bcl-2 and Bax were studied. There was no significant difference in growth rate or transmigration between the parental and resistant cells. Sunitinib-resistant cells were significantly hypertrophic compared with parental cells as evidenced by increases in the surface areas of the whole cells and the nuclei. IL-6 was significantly increased in all resistant cells. IL-8 was increased in sunitinib-resistant Caki-2 and SN12K1 cells and decreased in 786-0 without any significant changes in Caki-1. VEGF was increased in resistant Caki-2 and SN12K1 cells but not in 786-0 and Caki-1. The Bcl2/Bax ratio was increased in Caki-1, Caki-2 and SN12K1 cells but decreased in 786-0 cells. The increased IL-6 may contribute to sunitinib resistance either via VEGF-mediated angiogenesis or through shifting of the Bcl2/Bax balance in favour of anti-apoptosis.

Abstract Clear cell renal cell carcinoma (ccRCC) is one of the most common malignant tumors in the urinary system, and its incidence continues to increase. Regulator of calcineurin 1 (RCAN1), one of the genes on chromosome 21, is a crucial mediator of tumor inhibition. RCAN1.4 is best characterized as an endogenous inhibitor of the phosphatase calcineurin, and it has been observed to be downregulated in numerous types of cancer. However, its essential function remains unclear in ccRCC. In the present study, we found that RCAN1.4 expression was frequently downregulated in renal cell carcinoma tissues and cells and was inversely correlated with various clinicopathological parameters. Low RCAN1.4 expression was associated with poor overall survival and disease-free survival and could act as a diagnostic indicator in ccRCC patients. Furthermore, the overexpression of RCAN1.4 inhibited cell proliferation, migration and invasion, whereas RCAN1.4 knockdown promoted these functions in ccRCC cell lines. In addition, RCAN1.4 expression was downregulated in sunitinib-resistant renal cancer cell lines, and inhibition of RCAN1.4 promoted sunitinib resistance. We also found that RCAN1.4 could regulate epithelial-mesenchymal transition (EMT) and the expression of HIF2α in sunitinib-resistant cell lines. Taken together, these findings indicate that downregulation of RCAN1.4 may be crucial for the metastasis of ccRCC and may induce sunitinib resistance. RCAN1.4 may act as a prognostic indicator and potential therapeutic target for ccRCC. [ABSTRACT FROM AUTHOR]

Sunitinib resistance is, nowadays, the major challenge for advanced renal cell carcinoma patients. Illuminating the potential mechanisms and exploring effective strategies to overcome sunitinib resistance are highly desired. We constructed a reliable gene signature which may function as biomarkers for prediction of sunitinib sensitivity and clinical prognosis. The gene expression profiles were obtained from The Cancer Genome Atlas database. By performing GEO2R analysis, numerous differentially expressed genes (DEGs) were found to be associated with sunitinib resistance. To acquire more precise DEGs, we integrated three different microarray datasets. Functional analysis revealed that these DEGs were mainly involved in Rap1 signaling pathway, p53 signaling pathway and Ras signaling pathway. Then, top five hub genes, BIRC5, CD44, MUC1, TF, CCL5, were identified from protein–protein interaction (PPI) network. Sub‐network analysis carried out by MCODE plugin revealed that key DEGs were related with PI3K‐Akt signaling pathway, Rap1 signaling pathway and VEGF signaling pathway. Next, we established sunitinib‐resistant OS‐RC‐2 and 786‐O cell lines and validated the expression of five hub genes in cell lines. To further evaluate the potentials of five‐gene signature for predicting clinical prognosis, we analyzed RCC patients with gene expressions and overall survival information from two independent patient datasets. The Kaplan–Meier estimated the OS of RCC patients in the low‐ and high‐risk groups according to gene expression signature. Multivariate Cox regression analysis indicated that the prognostic power of five‐gene signature was independent of clinical features. In conclusion, we developed a five‐gene signature which can predict sunitinib sensitivity and OS for advanced RCC patients, providing novel insights into understanding of sunitinib‐resistant mechanisms and identification of RCC patients with poor prognosis. [ABSTRACT FROM AUTHOR]

Renal cell carcinoma (RCC) is a highly vascularized tumor type, which is often associated with inactivated mutations in the von Hippel-Lindau gene that drives proangiogenic signaling pathways. As such, new therapies for the treatment of RCC have largely been focused on blocking angiogenesis. Sunitinib, an antiangiogenic tyrosine kinase inhibitor, is the most frequently used first-line drug for the treatment of RCC. Although treatment with sunitinib improves patient outcome considerably, acquired resistance will emerge in all cases. The molecular mechanisms of resistance to sunitinib are poorly understood, but in the past decade, several of these have been proposed. Lysosomal sequestration of sunitinib was reported as a potential resistance mechanism to sunitinib. In this review, the underlying molecular mechanisms of lysosomal sunitinib sequestration and the potential strategies to overcome this resistance are discussed to be able to further improve the treatment of RCC.

Renal cell carcinoma (RCC) is a serious threat to people's health due to its rapid progression, and patients easily develop resistance to targeted therapy. The absent in melanoma 2 (AIM2) is a receptor protein that has recently been proposed to play an important role in various diseases. In this study, AIM2 was identified as a new biomarker of RCC and promoted RCC progression and sunitinib resistance in an inflammasome-independent manner. Mechanistically, AIM2 promoted FOXO3a phosphorylation and proteasome degradation, thereby reducing its transcriptional effect on ACSL4 and inhibiting ferroptosis. In summary, AIM2 promoted RCC progression and sunitinib resistance through FOXO3a-ACSL4 axis-regulated ferroptosis, which could provide new ideas and therapeutic targets for RCC diagnosis and treatment., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

Sunitinib, an inhibitor of receptor tyrosine kinase, possesses anti-tumor activity in renal cell carcinoma (RCC) through its anti-angiogenic effects. However, patients with advanced RCC are resistant to sunitinib. Dysregulated circRNAs has been shown to be associated with drug resistance in various tumors. However, little is known about the effect of circRNA&#95;001895 on sunitinib resistance of RCC. First, the expression of circRNA&#95;001895 was found to be higher in sunitinib-resistant RCC tissues than chemosensitive tumor tissues. Half maximal inhibitory concentration of sunitinib-resistant RCC cells (786-O/R and ACHN/R) was higher than sunitinib-sensitive 786-O and ACHN cells. CircRNA&#95;001895 was also upregulated in 786-O/R and ACHN/R cells. Second, data from colony formation and flow cytometry analysis showed that knockdown of circRNA&#95;001895 suppressed cell proliferation and promoted cell apoptosis in 786-O/R and ACHN/R cells. Moreover, the protein expression of phosphorylated histone H2AX (γH2AX) was enhanced, while phosphorylated DNA-dependent protein kinase (p-DNA-PK) and Rad51 were reduced in 786-/R and ACHN/R by knockdown of circRNA&#95;001895. Lastly, knockdown of circRNA&#95;001895 conferred sensitivity of in vivo tumor growth to sunitinib. In conclusion, circRNA&#95;001895 was implicated in the sunitinib resistance in RCC through regulation of apoptosis and DNA damage repair, suggesting that circRNA&#95;001895 might be a potential therapeutic target for advanced RCC.

Background: Metastatic renal cell carcinoma (RCC) often develops resistance to first-line targeted therapy such as sunitinib. G-Protein-coupled estrogen receptor 1 (GPER1) agonist G-1 was recently reported to regulate RCC physiology but the role of G-1 in RCC tumorigenesis and sunitinib resistance remains largely unknown., Materials and Methods: Parental and sunitinib-resistant 786-O cells were treated with GPER1 agonist G-1, and quantitative phosphoproteomics was performed. Bioinformatic analyses and validations, including immunoblotting, cell migration, and cell cycle distribution, were performed., Results: G-1 repressed cell proliferation and migration in both parental and sunitinib-resistant 786-O cells. Phosphoproteomic signatures, including phosphoinositide 3-kinase and protein kinase B (PI3K-AKT) as well as other pathways, were up-regulated in sunitinib-resistant cells but application of G-1 reversed this effect. Among phosphoprotein candidates, activating transcription factor 2 (ATF2) Thr69/71 phosphorylation was antagonistically regulated by sunitinib resistance and G-1., Conclusion: Our results open up the possibility for managing RCC and sunitinib resistance by GPER1 agonist G-1 and its regulated pathways., (Copyright© 2021, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Lysosomal accumulation of sunitinib has been suggested as an underlying mechanism of resistance. Here, we investigated if photochemical internalization (PCI), a technology for cytosolic release of drugs entrapped in endosomes and lysosomes, would activate lysosomal sequestered sunitinib. By super-resolution fluorescence microscopy, sunitinib was found to accumulate in the membrane of endo/lysosomal compartments together with the photosensitizer disulfonated tetraphenylchlorin (TPCS2a). Furthermore, the treatment effect was potentiated by PCI in the human HT-29 and the mouse CT26.WT colon cancer cell lines. The cytotoxic outcome of sunitinib-PCI was, however, highly dependent on the treatment protocol. Thus, neoadjuvant PCI inhibited lysosomal accumulation of sunitinib. PCI also inhibited lysosomal sequestering of sunitinib in HT29/SR cells with acquired sunitinib resistance, but did not reverse the resistance. The mechanism of acquired sunitinib resistance in HT29/SR cells was therefore not related to lysosomal sequestering. Sunitinib-PCI was further evaluated on HT-29 xenografts in athymic mice, but was found to induce only a minor effect on tumor growth delay. In immunocompetent mice sunitinib-PCI enhanced areas of treatment-induced necrosis compared to the monotherapy groups. However, the tumor growth was not delayed, and decreased infiltration of CD3-positive T cells was indicated as a possible mechanism behind the failed overall response. [ABSTRACT FROM AUTHOR]

Sphingosine kinase 1 (SphK1) is the major source of the bioactive lipid and GPCR agonist sphingosine 1-phosphate (S1P). Although alterations in SphK1 expression and activity have been detected in various human malignancies, its potential molecular mechanisms in the development and sunitinib resistance of clear cell renal cell carcinoma (ccRCC) remain obscure. In this study, we aim to evaluate the clinical significance of SphK1 and to explore the therapeutic implications of combination approach for ccRCC patients. We identify upregulation of SphK1 significantly associated with poor prognosis of large cohort of ccRCC patients, which contributing to cell proliferation, colony formation, migration and survival. Suppression of SphK1 activity either by shRNA or pharmacologic inhibitior FTY720 suppresses cell growth in vitro and in vivo. A comprehensive phosphoprotein antibody array reveals that SphK1 overexpression promoted RCC progression by regulating the Akt/mTOR pathway. Moreover, FTY720 administration enhanced tumor growth inhibition effect of sunitinib treatment on RCC cells in vitro and in vivo. Our results unraveled that increased SphK1 kinase activation defines an important mechanism for sunitinib resistance, therefore contributes to tumour development and represents therapeutic targets for ccRCC. [ABSTRACT FROM AUTHOR]

Sunitinib is used as standard treatment for metastatic or unresectable clear cell renal cell carcinoma (ccRCC). However, ccRCC eventually develops resistance to sunitinib in most cases, and the mechanisms underlying such resistance have not been fully determined. Nuclear receptors (NRs) are a class of transcription factors that regulate many cellular functions by controlling gene expression, and they also play important roles in tumor development, proliferation and progression in various types of cancers. In the present study, we aimed to explore the mechanisms underlying sunitinib resistance in RCC and the potential role of NRs in sunitinib resistance. The expression profile of NRs was obtained from the Gene Expression Omnibus (GEO) RNAseq database. A total of 138 patients from GSE65615 were examined in this study. From the GEO metadata, we found that the expressions of three genes, encoding peroxisome proliferator activated receptor alpha (PPARα), androgen receptor (AR) and PPARγ, were significantly increased in sunitinib-treated samples compared with control samples. RT-PCR analysis showed that the PPARα expression at the mRNA level was significantly increased in sunitinib-resistant A498, CaKi-1 and 780-O ccRCC lines compared with their sunitinib-sensitive parental cells. Furthermore, knockdown of PPARα significantly inhibited cell proliferation in all three sunitinib-resistant ccRCC lines, successfully overcoming the resistance to sunitinib. Our results also showed that nuclear factor kappa B (NF-κB) signaling pathway was activated in sunitinib-resistant ccRCC lines, indicating that PPARα and NF-κB inhibition could play a synergistic role to modulate sunitinib resistance and suggesting that PPARα could be used as a potential target to overcome sunitinib resistance via the NF-κB pathway., Competing Interests: None., (IJCEP Copyright © 2018.)

Background/aim: Placental growth factor (PlGF) is up-regulated in major malignant diseases or following antiangiogenic therapy, although it is present in low levels under normal physiological conditions. TB403, a monoclonal antibody against PlGF, was investigated in clear cell renal cell carcinoma (ccRCC) xenografts since it has been proposed as a potential target in oncology., Materials and Methods: Human ccRCCs were implanted in athymic nude mice to evaluate the efficacy of TB403 and to excise xenograft tumors for molecular experiments., Results: TB403 did not significantly inhibit tumor growth in treatment-naïve or sunitinib-resistant ccRCC xenografts. Gene expression profiling resulted in over-expression of the C1orf38 gene, which induced immunoreactivity in macrophages. Angiogenesis PCR arrays showed that VEGFR-1 was not expressed in ccRCC xenografts., Conclusion: PlGF blockade did not have a broad antiangiogenic efficacy; however, it might be effective on-target in VEGFR1-expressing tumors. The inhibition of VEGF pathway may induce the activity of tumor-associated-macrophages for angiogenesis escape., (Copyright© 2015 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.)