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Background To explore the possible mechanism by which curcumin reverses the sunitinib resistance in clear cell renal cell carcinoma (ccRCC). Methods A sunitinib-resistant ccRCC cell model was established. The MTT assay was used to determine the half maximal inhibitory concentration (IC50) and drug resistance (DR) index. The effects of curcumin plus sunitinib or sunitinib alone on drug-resistant cell lines were verified by the cell counting kit-8 (CCK-8)assay, colony formation assay, and apoptosis assay. The concentration of iron ions in the cell lines was analyzed using an Abcam Iron Assay Kit. The expressions of ADAMTS18 gene and ferroptosis-related proteins (NCOA4, FTH1 and p53) after curcumin plus sunitinib treatment were analyzed by reverse transcription polymerase chain reaction (RT-PCR) and Western blotting. After transfection of curcumin plus sunitinib/sunitinib alone-treated drug-resistant cell lines with si-ADAMTS18, cell proliferation activity was assessed by the CCK-8 assay, and the protein expression levels of ADAMTS18, NCOA1, FTH1 and p53 were analyzed by Western blotting. After treatment with ferroptosis-1 (Fer-1; a ferroptosis inhibitor), the cell proliferation activity of drug-resistant cell lines treated with curcumin plus sunitinib/sunitinib alone was reassessed using the CCK-8 assay. Results Curcumin plus sunitinib inhibited the proliferation of sunitinib-resistant ccRCC cells (P0.05). Ferroptosis inhibitors reversed the inhibitory effect of curcumin on sunitinib-resistant ccRCC cell lines. Conclusions Curcumin can reverse the sunitinib resistance in ccRCC, possibly by upregulating the expression of the ADAMTS18 gene to induce ferroptosis.

We investigated the prognostic significance of Death-Associated Protein Kinase 1 (DAPK1) and its role in sunitinib resistance in clear cell renal cell carcinoma (ccRCC). DAPK1 mRNA levels were significantly lower in tumor tissues than normal kidney tissues in TCGA-KIRC dataset (n=428). Both overall survival and disease-free survival were significantly shorter in ccRCC patients with low DAPK1 expression than those with high DAPK1 expression. Receiver operating characteristic curve analysis showed that low DAPK1 expression correlated with poor prognosis in ccRCC patients. Multivariate analysis confirmed that DAPK1 expression was an independent prognostic indicator in ccRCC. Gene set enrichment analysis showed that low DAPK1 expression correlates with upregulation of pathways related to metastasis, drug resistance, hypoxia and invasiveness in ccRCC patients. Sunitinib-resistant ccRCC cells show significantly lower DAPK1 mRNA and protein levels than sunitinib-sensitive ccRCC cells. DAPK1 overexpression enhances apoptosis in sunitinib-resistant ccRCC cells via the ATF6-dependent ER stress pathway. Xenograft tumors derived from DAPK1-overxpressing ccRCC cells were significantly smaller than the controls in nude mice. Our finding demonstrates that low DAPK1 expression is an independent prognostic indicator that correlates with ccRCC progression and sunitinib resistance.

Sunitinib is a standard molecular-targeted drug used as a first-line treatment for metastatic clear cell renal cell carcinoma (ccRCC); however, resistance to sunitinib has become a major problem in medical practice. Recently, bromodomain containing 4 (BRD4), a member of the bromodomain family proteins, was identified as a promising therapeutic target, and its inhibitor JQ1 has been shown to have inhibitory effects in various human cancers. However, the anti-cancer effects of JQ1 in ccRCC, particularly sunitinib-resistant ccRCC, are still unclear. Here, we aimed to elucidate the anti-cancer effects of JQ1 and the mechanisms underlying BRD4 inhibition in sunitinib-sensitive and -resistant ccRCCs. Analysis of The Cancer Genome Atlas (TCGA) ccRCC cohort showed that patients with high BRD4 expression had shorter overall survival than those with low expression. JQ1 treatment significantly inhibited tumor growth of sunitinib-sensitive and -resistant ccRCC cells in part through MYC regulation. Based on RNA sequencing analyses of ccRCC cells treated with JQ1 to elucidate the mechanisms other than MYC regulation, we identified several oncogenes that may be potential therapeutic targets or prognostic markers; patients with high expression of SCG5, SPOCD1, RGS19, and ARHGAP22 had poorer overall survival than those with low expression in TCGA ccRCC cohort. Chromatin immunoprecipitation assays revealed that these oncogenes may be promising BRD4 targets, particularly in sunitinib-resistant ccRCC cells. These results identified SCG5, SPOCD1, RGS19, and ARHGAP22 as potential prognostic markers and showed that BRD4 inhibition may have applications as a potential therapeutic approach in sunitinib-sensitive and -resistant ccRCC.

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., A new mTOR inhibitor, Rapalink‐1, suppresses the MAPK signaling pathway, the ErbB signaling pathway and ABC transporters.

Clear cell renal cell carcinoma (ccRCC) is the most common subtype of renal cell cancer, characterized by the highest mortality rate among other RCC subtypes due to the occurrence of metastasis and drug resistance following surgery. The Von Hippel-Lindau tumor suppressor (VHL)-hypoxia-inducible factor 1 subunit α (HIF1A)/hypoxia-inducible factor 2α (HIF2A)-vascular endothelial growth factor A (VEGFA) protein axis is involved in the development and progression of ccRCC, whereas sunitinib, a tyrosine kinase inhibitor, blocks the binding of VEGFA to its receptor. The aim of the present study was to examine the possible association of the gene expression of VHL, HIF1A, HIF2A, VEGFA and tumor protein P53 (P53) in cancer tissue with the outcome of ccRCC patients who were treated with sunitinib as first-line therapy following nephrec-tomy. A total of 36 ccRCC patients were enrolled, 11 of whom were administered sunitinib post-operatively. Tumor and control samples were collected, and mRNA and protein levels were assessed by reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. High mRNA and protein expression levels of HIF2A and VEGFA were found to be associated with shorter overall survival (OS) and progression-free survival (PFS) rates, as well as with unfavorable risk factors of cancer recurrence and mortality. Resistance to sunitinib was also observed; the OS and PFS rates were shorter (median OS and PFS: 12 and 6 months, respectively, vs. undetermined). Sunitinib resistance was associated with high HIF2A and VEGFA protein levels (b=0.57 and b=0.69 for OS and PFS, respectively; P

Background: Multiple lines of evidence support that the Hedgehog (Hh) signalling has a role in the maintenance and progression of different human cancers. Therefore, inhibition of the Hh pathway represents a valid anticancer therapeutic approach for renal cell carcinoma (RCC) patients. NVP-LDE225 is a Smoothened (Smo) antagonist that induces dose-related inhibition of Hh and Smo-dependent tumour growth. Methods: We assayed the effects of NVP-LDE225 alone or in combination with everolimus or sunitinib on the growth and invasion of human RCC models both in vitro and in vivo. To this aim, we used a panel of human RCC models, comprising cells with acquired resistance to sunitinib - a multiple tyrosine kinase inhibitor approved as a first-line treatment for RCC. Results: NVP-LDE225 cooperated with either everolimus or sunitinib to inhibit proliferation, migration, and invasion of RCC cells even in sunitinib-resistant (SuR) cells. Some major transducers involved in tumour cell motility, including paxillin, were also efficiently inhibited by the combination therapy, as demonstrated by western blot and confocal microscopy assays. Moreover, these combined treatments inhibited tumour growth and increased animal survival in nude mice xenografted with SuR RCC cells. Finally, lung micrometastasis formation was reduced when mice were treated with NVP-LDE225 plus everolimus or sunitinib, as evidenced by artificial metastatic assays. Conclusions: Hedgehog inhibition by NVP-LDE225 plus sunitinib or everolimus bolsters antitumour activity by interfering with tumour growth and metastatic spread, even in SuR cells. Thus, this new evidence puts forward a new promising therapeutic approach for RCC patients.