Sunitinib Resistance Research Articles

Mutational heterogeneity of imatinib resistance and efficacy of ripretinib vs sunitinib in patients with gastrointestinal stromal tumor: ctDNA analysis from INTRIGUE.

397784 Background: Ripretinib, a switch-control tyrosine kinase inhibitor (TKI), is indicated for patients (pts) with gastrointestinal stromal tumor (GIST) who received prior treatment with ≥3 TKIs, including imatinib. Sunitinib is approved for advanced GIST after imatinib failure. Circulating tumor DNA (ctDNA) analysis may provide insight into the efficacy of these agents in second-line advanced GIST. Here, we present exploratory baseline ctDNA results from INTRIGUE. Methods: INTRIGUE is an open-label, phase 3 study that enrolled adult pts with advanced GIST who progressed on or had intolerance to imatinib (NCT03673501). Randomization was 1:1 to ripretinib 150 mg once daily (QD) or sunitinib 50 mg QD (4 wks on/2 wks off). Baseline peripheral whole blood was analyzed by Guardant360, a 74-gene ctDNA next-generation sequencing (NGS)-based assay. Only KIT mutations are reported here. Results: Of 453 pts in the overall intent-to-treat (ITT) population, 362 (80%) samples were analyzed. ctDNA was detected in 280/362 (77%), with KIT mutations detected in 213/280 (76%). Common resistance mutations were in the KIT activation loop (AL; exons 17/18; 89/213, 42%) and ATP-binding pocket (ATP-BP; exons 13/14; 81/213, 38%). Efficacy in pts with detectable ctDNA in the KIT exon 11 and overall ITT populations was consistent with the primary analysis based on tumor data used for randomization. Pts with KIT exon 11 + 17/18 (−9/13/14) mutations had superior progression-free survival (PFS), objective response rate (ORR), and overall survival (OS) with ripretinib vs sunitinib, whereas pts with exon 11 + 13/14 (−9/17/18) mutations had better PFS, ORR, and OS with sunitinib vs ripretinib (Table). Subgroup safety profiles were consistent with the primary analysis. Conclusions: While KIT ATP-BP mutations predicted clinical benefit from sunitinib vs ripretinib, pts harboring resistance mutations in the KIT AL derived meaningful clinical benefit from ripretinib but not sunitinib. This study demonstrates the value of ctDNA NGS-based sequencing of the complex landscape of KIT mutations to predict the clinical benefit of ripretinib or sunitinib as second-line therapy in pts with advanced GIST. Clinical trial information: NCT03673501 . [Table: see text]

ZDHHC2-mediated AGK palmitoylation activates AKT/mTOR signaling to reduce sunitinib sensitivity in renal cell carcinoma.

Tyrosine kinase inhibitors (TKIs) that can suppress the VEGF signaling pathway and angiogenesis have been developed to impede the progression of malignant tumors and have been approved as first-line targeted agents for clear cell renal cell carcinoma (ccRCC). Dysregulation of lipid metabolism is a major driver of TKI resistance in renal cancer. In this study, we showed that the palmitoyl acyltransferase ZDHHC2 is abnormally upregulated in tissues and cell lines resistant to TKIs, such as sunitinib. Upregulation of ZDHHC2 contributed to sunitinib resistance in cells and mice, and ZDHHC2 regulated angiogenesis and cell proliferation in ccRCC. Mechanistically, ZDHHC2 mediated AGK S-palmitoylation to promote translocation of AGK into the plasma membrane and activation of the PI3K-AKT-mTOR signaling pathway in ccRCC, which modulated sunitinib sensitivity. In conclusion, these results identify a ZDHHC2-AGK signaling axis and suggest that ZDHHC2 is a targetable candidate for improving the anti-tumor efficacy of sunitinib in ccRCC.

Abstract 3585: Probing the relationship between renal carcinoma perfusion, hypoxia, and metabolism during response to VEGFR inhibition and at resistance

Abstract Clear cell renal cell carcinoma (ccRCC) is the most common primary kidney cancer. VEGF-receptor tyrosine kinase inhibitors remain a second-line or concurrent (with immunotherapy) treatment option for advanced RCC, but resistance inevitably occurs. There remains a need for biomarkers predictive of response to VEGFR targeting. Anti-VEGFR therapy-induced hypoxia can result in changes to both tumor metabolism and vascularization that contribute to the aggressiveness of treatment-resistant tumors. In this study we used in vivo hyperpolarized 13C-tert-butanol, a freely-diffusible novel MRI tracer that provides high-SNR tissue perfusion mapping, and hyperpolarized 13C pyruvate MRI, which enables real-time investigation of glycolytic lactate production, to understand the evolution of RCC perfusion and metabolism in response to VEGFR targeting, while correlating to histologic measures of tumor proliferation (Ki67) and vascularization (CD34). A498, a human ccRCC cell line, was implanted subcutaneously into 12-week-old nude mice. When tumors reached 15mm, the mice were placed into three arms, untreated (UT), sunitinib sensitive (SS), and sunitinib resistant (SR). SS mice were treated with sunitinib (25 mg/kg via gavage) then the mice were imaged with MRI at 48 hours. SR mice were treated with sunitinib daily until 2mm of re-growth was detected, then MRI was performed. UT mice were imaged when tumors reached 20mm. Pimonidazole infusion immediately after MRI, then the tumors were harvested. Histology included Ki67, CD34, and pimonidazole (hypoxia) staining. Ki67 expression was greater in the UT group compared to SS (37.56±5.21 vs 26.23±3.78, p=0.004), but not compared to SR (37.56±5.21 vs 34.32±1.12, p=0.93). The UT group demonstrated greater vascularization with CD-34 vessel counting than SS (UT 6.70±1.81 vs. SS 2.39±1.16, p=0.002), while vascularization was increased in SR compared to SS (SR 3.82±1.81 vs SS 2.39±1.16, p=0.05). Ki67 expression was positively correlated with CD34 expression. MR-measured tumor perfusion of the SS group was greater than UT (0.0086±0.0056 vs 0.0035±0.0026, p=0.0001) and SR (0.0086±0.0056 vs 0.0043±0.0033, p=0.0003). Tumor lactate production in the SS group was lower than UT (0.752±0.268 vs 0.609±0.188, p=0.04) and SR (0.752±0.268 vs 0.593±0.246, p=0.006). However, tumor perfusion was negatively correlated with lactate production ratio only in the SR group. Untreated and sunitinib-resistent RCC tumors are associated with increased perfusion and vascularity, and decreased lactate production. An inverse relationship between lactate production and perfusion in SR may be attributable to vascular normalization. Analysis of the spatial relationship between tumor metabolism and perfusion will further yield additional detail on the interplay between hypoxia and metabolism. Citation Format: Qianhui Dou, Patricia Coutinho de Souza, Xiaoen Wang, Aaron K. Grant, Leo L. Tsai. Probing the relationship between renal carcinoma perfusion, hypoxia, and metabolism during response to VEGFR inhibition and at resistance. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3585.

Abstract 3892: EZH2 mediated kinome reprogramming drives AR phosphorylation and activation in receptor tyrosine kinase inhibitors resistant renal carcinoma models

Abstract Systemic treatment of recurrent/metastatic renal cell carcinoma (RCC) largely uses receptor tyrosine kinase inhibitors (RTKI), as single agents or in combination with immune checkpoint inhibitors. Unfortunately, patients commonly develop resistance to RTKI’s, leaving few options for further treatment. Therefore, understanding the mechanisms responsible for drug resistance is critical to improve the clinical outcome in this disease. Our previous studies of acquired resistance to the RTKI sunitinib identified two major regulators, EZH2 and androgen receptor (AR). Inhibition of EZH2 or AR in combination with sunitinib re-sensitizes cells to sunitinib both in vitro and in vivo. To further explore the link between EZH2 and AR in drug resistance, 786-0 RCC cells with acquired resistance to sunitinib (786-0RS) was compared to drug naive 786-0 cells with exogenous AR (786-0AR). Chromatin immunoprecipitation sequencing (ChIP-seq) showed that AR and EZH2 bind the same genomic locations, but only in the resistant strain. Interestingly, treatment of 786-0AR cells with sunitinib caused AR to translocate to the nucleus observed by the presence of AR at EZH2 bound sites. Additionally, mass spec of AR purified from 786-0RS cells and 786-0AR cells found high phosphorylation of S81 and S213, two markers associated with ligand independent activation, in 786-0RS cells, but not in 786-0AR cells. Previously, our lab has reported that 786-0RS cells display a reprogramming of the tyrosine kinome which is dependent on EZH2 likely via a non-canonical mechanism. Consistent with this, EZH2 with a phosphomimetic mutation in Serine 21 (S21D) could promote sunitinib resistance when over-expressed with AR, whereas wild-type and phosphonull (S21A) EZH2 could not. We have also expanded the serine/threonine phosphoproteomic analysis and found extensive rewiring of these signaling networks in 786-0RS cells with an enrichment of EGFR mediated MAPK and AKT signaling when compared to 786-0 cells. Finally, our lab has generated 786-0 strains resistant to other RTKI including pazopanib and lenvatinib, and found that AR is expressed in these resistant models, solidifying AR activation as a conserved feature of RTKI resistance. Overall, our results suggest that AR activation is driven by phosphorylation induced by EZH2 dependent kinome reprogramming. Untangling the cross talk between AR and EZH2 in RTKI resistant RCC will provide the rationale for novel therapeutic strategies to improve the clinical outcome in patients with this disease. Citation Format: Christopher Rupert, Stephanie Metcalf, Saranya Rajendran, Sean Colligan, Peter Hollenhorst, Roberto Pili. EZH2 mediated kinome reprogramming drives AR phosphorylation and activation in receptor tyrosine kinase inhibitors resistant renal carcinoma models. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3892.

CircPTPN12 promotes the progression and sunitinib resistance of renal cancer via hnRNPM/IL-6/STAT3 pathway

Renal cell carcinoma (RCC) is characterized by the difficulties in early diagnosis and the propensity to metastases. For advanced RCC, sunitinib targeted therapy is the clinically recommended first-line drug and the major challenge of sunitinib treatment is adaptive resistance. Therefore, it is imperative to research the mechanisms underlying sunitinib resistance. In this study, we discovered that circPTPN12 was highly expressed in RCC tissues and was associated with poorer clinical outcomes. circPTPN12 could promote the proliferation, migration, invasion, and sunitinib resistance of RCC cells. Mechanistically, circPTPN12 was found to form a complex with hnRNPM, which was involved in the regulation of mRNA processing. The combination with circPTPN12 enhanced the ability of hnRNPM to maintain the stability of IL-6 mRNA and further activated the STAT3 signaling pathway. The study revealed that circPTPN12/hnRNPM/IL-6/STAT3 axis promoted RCC progression and sunitinib resistance, which might be a promising therapeutic target for relieving sunitinib resistance in RCC.

The m6A-regulation and single cell effect pattern in sunitinib resistance on clear cell renal cell carcinoma: Identification and validation of targets.

Background: Sunitinib is the main target drug for clear cell renal cell carcinoma. However, the effect of sunitinib is often limited by acquired drug resistance. Methods: The open-accessed data used in this study were obtained from different online public databases, which were analyzed using the R software. The RNA level of specific genes was detected using quantitative Real-Time PCR. Sunitinib-resistant cell lines were constructed based on protocol get from the previous study. Colony formation and Cell Counting Kit-8 assays were applied to detect cell proliferation ability. Results: In this study, through publicly available data and high-quality analysis, we deeply explored the potential biological mechanisms that affect the resistance of sunitinib. Detailed, data from GSE64052, GSE76068 and The Cancer Genome Atlas were extracted. We identified the IFITM1, IL6, MX2, PCOLCE2, RSAD2 and SLC2A3 were associated with sunitinib resistance. Single-cell analysis, prognosis analysis and m6A regulatory network were conducted to investigate their role. Moreover, the MX2 was selected for further analysis, including its biological role and effect on the ccRCC microenvironment. Interestingly, we noticed that MX2 might be an immune-related gene that could affect the response rate of immunotherapy. Then, in vitro experiments validated the overexpression of MX2 in sunitinib-resistance cells. Colony formation assay indicated that the knockdown of MX2 could remarkably inhibit the proliferation ability of 786-O-Res and Caki-1-Res when exposed to sunitinib. Conclusion: In summary, through publicly available data and high-quality analysis, we deeply explored the potential biological mechanisms that affect the resistance of sunitinib. MX2 was selected for further analysis, including its biological role and effect on the ccRCC microenvironment. Finally, in vitro experiments were used to validate its role in ccRCC.

Sunitinib resistance in renal cell carcinoma: From molecular mechanisms to predictive biomarkers.

Currently, renal cell carcinoma (RCC) is the most prevalent type of kidney cancer. Targeted therapy has replaced radiation therapy and chemotherapy as the main treatment option for RCC due to the lack of significant efficacy with these conventional therapeutic regimens. Sunitinib, a drug used to treat gastrointestinal tumors and renal cell carcinoma, inhibits the tyrosine kinase activity of a number of receptor tyrosine kinases, including vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR), c-Kit, rearranged during transfection (RET) and fms-related receptor tyrosine kinase 3 (Flt3). Although sunitinib has been shown to be efficacious in the treatment of patients with advanced RCC, a significant number of patients have primary resistance to sunitinib or acquired drug resistance within the 6-15 months of therapy. Thus, in order to develop more efficacious and long-lasting treatment strategies for patients with advanced RCC, it will be crucial to ascertain how to overcome sunitinib resistance that is produced by various drug resistance mechanisms. In this review, we discuss: 1) molecular mechanisms of sunitinib resistance; 2) strategies to overcome sunitinib resistance and 3) potential predictive biomarkers of sunitinib resistance.

The E3 ligase RBCK1 reduces the sensitivity of ccRCC to sunitinib through the ANKRD35-MITD1-ANXA1 axis.

Despite the promise of targeted tyrosine kinase inhibitors (TKIs), such as sunitinib, in the extension of survival time in patients with clear cell renal cell carcinoma (ccRCC) progression or metastasis, the patients eventually succumb to inevitable drug resistance. Protein degradation executed by the ubiquitin-dependent proteasome system played an important role in determining the sensitivity of ccRCC to sunitinib. Here, we applied the bioinformatic analysis to identify that E3 ligase RBCK1 was elevated in the sunitinib-resistant renal cancer cell lines or patient specimens. The subsequent in vitro or in vivo studies demonstrated that RBCK1 contributed to decreasing the sensitivity of ccRCC to sunitinib. Then, we showed that inhibition of RBCK1 inactivated the AKT and MAPK signaling pathways, which might be one of the main reasons why RBCK1 induces sunitinib resistance in ccRCC cells. Mechanistically, our results indicated that RBCK1 promotes the degradation of ANKRD35 and that ANKRD35 destabilizes MITD1 by binding with SUMO2 in ccRCC cells. In addition, we showed that the RBCK1-ANKRD35-MITD1-ANXA1 axis regulates the phosphorylation of AKT and ERK and contributes to the dysregulation of sunitinib in ccRCC cells. Therefore, we identified a novel mechanism for regulating the sensitivity of sunitinib in ccRCC. Therefore, we elucidated a novel mechanism by which RBCK1 regulates sunitinib sensitivity in ccRCC.

AIM2 promotes renal cell carcinoma progression and sunitinib resistance through FOXO3a-ACSL4 axis-regulated ferroptosis.

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.

Suppression of SREBP-1 Expression by Simvastatin Decreases Visfatin-Induced Chemoresistance to Sunitinib in Human Renal Carcinoma 786-O Cells.

The resistance of renal cell carcinoma (RCC) to sunitinib impedes the success of chemotherapy in cancer treatment. Although several sunitinib resistance mechanisms have been proposed, little is known concerning the impact of obesity and adipokines in RCC cells. The upregulation of sterol-regulatory element-binding protein-1 (SREBP-1) has been reported to modulate the progression of tumor cells. The present study investigated the effect of visfatin on sunitinib-induced cytotoxicity in RCC cells through SREBP-1 expression. We found that visfatin-induced Akt and p70S6K activation increased SREBP-1 expression in 786-O cells. The visfatin-induced SREBP-1 mRNA and protein levels were attenuated through the inactivation of Akt and p70S6K by pharmacological inhibitors. In addition, the SREBP-1 knockdown using siRNA enhanced the cytotoxic effects of sunitinib. Our results also revealed the roles of simvastatin in attenuating the effects of visfatin on 786-O cells by inhibiting the production of reactive oxygen species. In particular, simvastatin co-treatment increased the cell cytotoxicity of sunitinib in visfatin-treated 786-O cells, which were associated with down-regulation of SREBP-1 expression. Our results suggest an important role of SREBP-1 in visfatin-induced drug resistance of RCC cells to sunitinib. The cytotoxic mechanism of simvastatin on RCC cells may provide a new strategy to improve therapeutic outcomes for the RCC treatment.

Extracellular Vesicle-Mediated Transfer of LncRNA IGFL2-AS1 Confers Sunitinib Resistance in Renal Cell Carcinoma.

Extracellular vesicle-packaged IGFL2-AS1 promotes sunitinib resistance by regulating TP53INP2-triggered autophagy, implicating this lncRNA as a potential therapeutic target in renal cell carcinoma.

Phosphoproteomic Analysis Identifies TYRO3 as a Mediator of Sunitinib Resistance in Metastatic Thymomas.

Simple SummaryAfter initially responding to empiric radio-chemotherapy, most advanced thymomas and thymic carcinomas become refractory and require second-line therapies. The multi-target tyrosine kinase inhibitor, sunitinib, is one of few options, especially in patients with thymic carcinomas, and has resulted in partial remissions and prolonged overall survival. However, sunitinib shows limited activity, and not all patients benefit equally. A better understanding of its mode of action and the definition of predictive biomarkers would help select patients who profit most. Using a real-time multiplex tyrosine phosphorylation assay containing 144 kinase substrates in a defined set of sunitinib-sensitive and -resistant cell lines, we generated a sunitinib response index (SRI). Protein lysates from thymomas and thymic carcinomas with spike-in of sunitinib were then classified as potential responders vs. non-responders using the same SRI classifier. Bioinformatic prediction and further experimental analysis of activated upstream kinases identified TYRO3 as a potent mediator of sunitinib resistance, specifically in metastatic thymomas. TYRO3 could serve both as a biomarker of sunitinib resistance and a potential therapeutic target that could help to tailor treatment decisions and to overcome therapy resistance in advanced thymomas and thymic carcinomas.Background: After initially responding to empiric radio-chemotherapy, most advanced thymomas (TH) and thymic carcinomas (TC) become refractory and require second-line therapy. The multi-target receptor tyrosine kinase (RTK) inhibitor, sunitinib, is one of the few options, especially in patients with thymic carcinomas, and has resulted in partial remissions and prolonged overall survival. However, sunitinib shows variable activity in thymomas, and not all patients benefit equally. A better understanding of its mode of action and the definition of predictive biomarkers would help select patients who profit most. Methods: Six cell lines were treated with sunitinib in vitro. Cell viability was measured by MTS assay and used to define in vitro responders and non-responders. A quantitative real-time assay simultaneously measuring the phosphorylation of 144 tyrosine kinase substrates was used to correlate cell viability with alterations of the phospho-kinome, calculate a sunitinib response index (SRI), and impute upstream tyrosine kinases. Sunitinib was added to protein lysates of 29 malignant TH and TC. Lysates were analyzed with the same phosphorylation assay. The SRI tentatively classified cases into potential clinical responders and non-responders. In addition, the activation patterns of 44 RTKs were studied by phospho-RTK arrays in 37 TH and TC. Results: SRI application separated thymic epithelial tumors (TET) in potential sunitinib responders and resistant cases. Upstream kinase prediction identified multiple RTKs potentially involved in sunitinib response, many of which were subsequently shown to be differentially overexpressed in TH and TC. Among these, TYRO3/Dtk stood out since it was exclusively present in metastatic TH. The function of TYRO3 as a mediator of sunitinib resistance was experimentally validated in vitro. Conclusions: Using indirect and direct phosphoproteomic analyses to predict sunitinib response in malignant TET, we have shown that TH and TC express multiple important sunitinib target RTKs. Among these, TYRO3 was identified as a potent mediator of sunitinib resistance activity, specifically in metastatic TH. TYRO3 may thus be both a novel biomarker of sunitinib resistance and a potential therapeutic target in advanced thymomas and thymic carcinomas.

Resistance to tyrosine kinase inhibitors promotes renal cancer progression through MCPIP1 tumor-suppressor downregulation and c-Met activation

Tyrosine kinase inhibitors (TKIs) are the most commonly used targeted therapeutics in clear-cell renal cell carcinoma (ccRCC); however, drug resistance limits their utility and can lead to tumor “flare-up” and progression. In this study, we show that RCC resistance to sunitinib and sorafenib involves different mechanisms and leads to increased malignancy. Sunitinib decreased tumor growth and cell motility along with increased E-cadherin expression and secretion of the proangiogenic cytokines IL6 and IL8, which activated senescence in ccRCC cells and led to VE-cadherin phosphorylation, enhancing tumor angiogenesis. Sorafenib resistance increased the levels of mesenchymal markers and the secretion of MMP9, which cleaved VE-cadherin and disrupted endothelial cell integrity. Both sunitinib resistance and sorafenib resistance led to activation of the c-Met receptor IRAK1 and downregulation of the tumor suppressor MCPIP1, resulting in an increase in the metastasis of resistant cells, possibly due in part to enhanced vascularization of ccRCC. MCPIP1 overexpression partially overcame resistance to these drugs by decreasing micrometastasis and decreasing the expression of factors involved in tumorigenesis. In tumor samples from ccRCC patients, we observed a significant increase in the level of the c-Met receptor, IRAK1 and a decrease in MCPIP1 with respect to normal kidney tissue. Our results indicate separate novel mechanisms for sunitinib and sorafenib resistance, which both lead to MCPIP1 inhibition and ccRCC progression. The presented study suggests caution in the treatment of RCC with TKIs, which may lead to the unintended outcome of tumor progression.

Combination of sunitinib and 177Lu-labeled antibody cG250 targeted radioimmunotherapy: A promising new therapeutic strategy for patients with advanced renal cell cancer

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.

CircME1 promotes aerobic glycolysis and sunitinib resistance of clear cell renal cell carcinoma through cis-regulation of ME1

Circular RNAs (circRNAs) play critical roles in clear cell renal cell carcinoma (ccRCC). However, their involvement in sunitinib resistance remains largely unknown. Herein, we identified a novel circRNA, named circME1, which contributes to sunitinib resistance development in ccRCC. CircME1 also promoted proliferation, migration, and invasion of ccRCC cells. Further mechanism analysis showed that circME1 interacted with U1 snRNP at the promoter of its parental gene ME1, thereby upregulating the expression of ME1, enhancing aerobic glycolysis of ccRCC, and promoting its malignant phenotype. Furthermore, ME1 specific inhibitor could effectively repress the oncogenic functions of circME1. Taken together, our study demonstrates that the circME1/ME1 pathway is involved in ccRCC progression and sunitinib resistance development, which may be exploited for anticancer therapy.

The lncARSR/PTEN/Akt/nuclear factor-kappa B feedback regulatory loop contributes to doxorubicin resistance in hepatocellular carcinoma.

Chemoresistance is a major obstacle to hepatocellular carcinoma (HCC) chemotherapy. Our previous study found that long noncoding RNA lncARSR (lncRNA Activated in RCC with Sunitinib Resistance) activated Akt signaling via repressing phosphatase and tensin homolog (PTEN) during doxorubicin resistance in HCC. The purpose of this study is to further explore lncARSR-mediated mechanisms and roles during doxorubicin resistance in HCC. The expression of lncARSR was detected by real-time quantitative polymerase chain reaction (qPCR). Nuclear factor-kappa B (NF-κB) activity was detected by NF-κB luciferase reporter assays, western blot, and NF-κB transcription factor assays. The effects of NF-κB on lncARSR were detected by chromatin immunoprecipitation assay, promoter luciferase reporter assay, and real-time qPCR. The effects of lncARSR/Akt/NF-κB on doxorubicin resistance were detected by Cell Counting Kit-8 assay, capsase-3 activity assay, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labelingassay. lncARSR activated NF-κB signaling through activation of Akt. NF-κB transactivated lncARSR through directly binding lncARSR promoter and increasing lncARSR promoter activity. Akt transactivated lncARSR via activating NF-κB signaling. Thus, lncARSR, Akt, and NF-κB formed a positive feedback regulatory loop in HCC. Through this feedback loop, lncARSR auto-regulated its transcription. Drug sensitivity assays showed that the lncARSR/Akt/NF-κB feedback regulatory loop promoted doxorubicin resistance in HCC. These findings identified the lncARSR/Akt/NF-κB feedback regulatory loop in HCC, which represent potential therapeutic targets for improving doxorubicin sensitivity in HCC.

N6-methyladenosine-modified TRAF1 promotes sunitinib resistance by regulating apoptosis and angiogenesis in a METTL14-dependent manner in renal cell carcinoma

BackgroundSunitinib resistance can be classified into primary and secondary resistance. While accumulating research has indicated several underlying factors contributing to sunitinib resistance, the precise mechanisms in renal cell carcinoma are still unclear.MethodsRNA sequencing and m6A sequencing were used to screen for functional genes involved in sunitinib resistance. In vitro and in vivo experiments were carried out and patient samples and clinical information were obtained for clinical analysis.ResultsWe identified a tumor necrosis factor receptor-associated factor, TRAF1, that was significantly increased in sunitinib-resistant cells, resistant cell-derived xenograft (CDX-R) models and clinical patients with sunitinib resistance. Silencing TRAF1 increased sunitinib-induced apoptotic and antiangiogenic effects. Mechanistically, the upregulated level of TRAF1 in sunitinib-resistant cells was derived from increased TRAF1 RNA stability, which was caused by an increased level of N6-methyladenosine (m6A) in a METTL14-dependent manner. Moreover, in vivo adeno-associated virus 9 (AAV9) -mediated transduction of TRAF1 suppressed the sunitinib-induced apoptotic and antiangiogenic effects in the CDX models, whereas knockdown of TRAF1 effectively resensitized the sunitinib-resistant CDXs to sunitinib treatment.ConclusionsOverexpression of TRAF1 promotes sunitinib resistance by modulating apoptotic and angiogenic pathways in a METTL14-dependent manner. Targeting TRAF1 and its pathways may be a novel pharmaceutical intervention for sunitinib-treated patients.

Circular RNA Eps15-homology domain-containing protein 2 induce resistance of renal cell carcinoma to sunitinib via microRNA-4731-5p/ABCF2 axis

ABSTRACT Circular RNAs (circRNAs) are linked with the occurrence and progression of renal cell carcinoma (RCC). However, circRNAs’ mechanism in developing resistance to RCC has not been clarified. This research assessed the role and mechanism of circular RNA circ Eps15-homology domain-containing protein 2 (EHD2) in the resistance of sunitinib (SU) to RCC. ACHN, 786-O, 769P, and HEK-293 T cells and RCC tissue samples were used for the investigations. The circEHD2 expression in RCC cells and tissues was determined through RT-qPCR. Association of circEHD2 with RCC histological grade of RCC was done through Chi-square. MiR-4731-5p, ABCF2, and circEHD2 were transfected into RCC cell lines. A dual-luciferase reporter assay was used to determine the interaction between miR-4731-5p, circEHD2, and ABCF2. MTT assay was used to analyze cell viability, while apoptosis was studied using flow cytometry. Colony-formation and transwell experiments were used to assess migration and invasion. The ATP Binding Cassette Subfamily F Member 2 (ABCF2) expression was analyzed through western blot. The results showed increased circEHD2 in SU-resistant RCC tissues and cell lines and implicated in RCC histological grade and SU resistance. Knock-down of circEHD2 down-regulated the resistance of RCC to SU in vitro and vivo; circEHD2 bound to miR-4731-5p to mediate ABCF2 in RCC; ABCF2 rescued the inhibitory effect of circEHD2 knock-down on SU resistance of RCC. In conclusion, circEHD2 enhances RCC resistance to SU via acting as a miR-4731-5p sponge to mediate ABCF2. MiR-4731-5p can target circEHD2 and ABCF2, thus providing a novel and effective therapeutic against renal cell carcinoma.

Single-cell RNA-sequencing analysis reveals MYH9 promotes renal cell carcinoma development and sunitinib resistance via AKT signaling pathway

Clear cell renal cell carcinoma (ccRCC) is a serious threat to human health worldwide, while its heterogeneity limits therapeutic success and leads to poor survival outcomes. Single-cell RNA-sequencing (scRNA-seq) is an important technology, which provides deep insights into the genetic characteristics of carcinoma. In this study, we profiled the gene expression of single cells from human ccRCC tissues and adjacent normal tissues using the scRNA-seq. We found that MYH9 was commonly upregulated in the ccRCC cell subgroup. Additionally, MYH9 was of highly expression in ccRCC tissues and predicted poor prognosis of ccRCC patients. MYH9 knockdown in ccRCC cells dampened their proliferative and metastatic potentials, whereas MYH9 overexpression enhanced these properties. In vivo, MYH9 also promoted ccRCC growth. Mechanistic studies showed that MYH9 played these vital roles through AKT signaling pathway. Furthermore, MYH9/AKT axis determined the responses of ccRCC cells to sunitinib treatment and might serve as a biomarker for sunitinib benefits in ccRCC patients. Thus, MYH9 might be a novel therapeutic target and prognostic predictor for ccRCC.

LPPR5 Expression in Glioma Affects Growth, Vascular Architecture, and Sunitinib Resistance.

Despite intensive research, glioblastoma remains almost invariably fatal. Various promising drugs targeting specific aspects of glioma biology, in addition to or as an alternative to antiproliferative chemotherapy, were not successful in larger clinical trials. Further insights into the biology of glioma and the mechanisms behind the evasive-adaptive response to targeted therapies is needed to help identify new therapeutic targets, prognostics, or predictive biomarkers. As a modulator of the canonically oncogenic Rho-GTPase pathway, Lipid phosphate phosphatase-related protein type 5 (LPPR5) is pivotal in influencing growth, angiogenesis, and therapeutic resistance. We used a GL261 murine orthotopic allograft glioma model to quantify the tumor growth and to obtain tissue for histological and molecular analysis. Epicortical intravital epi-illumination fluorescence video microscopy of the tumor cell spheroids was used to characterize the neovascular architecture and hemodynamics. GL261-glioma growth was delayed and decelerated after LPPR5 overexpression (LPPR5OE). We observed increased tumor cell apoptosis and decreased expression and secretion of vascular endothelial growth factor A in LPPR5OE glioma. Hence, an altered micro-angioarchitecture consisting of dysfunctional small blood vessels was discovered in the LPPR5OE tumors. Sunitinib therapy eliminated these vessels but had no effect on tumor growth or apoptosis. In general, LPPR5 overexpression generated a more benign, proapoptotic glioma phenotype with delayed growth and a dysfunctional vascular architecture.