These amyloid deposits hinder organ function, lead to their failure and, ultimately, death

ing adaptations to growth in culture and subsequent expansion. Thus, xenograft tumors derived from these cell lines often look quite different histologically from those routinely encountered in a clinical pathological laboratory. Therefore, in this study, we established two cohorts of primary xenograft MedChemExpress Tipifarnib models derived from patient surgical tissues that pathologically resembled the original tumors. Primary xenograft PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19741226 tumors derived from surgical specimens retain the histology as well as the gene expression levels, DNA copy number PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/1974422 alterations and over 90% of the protein-coding gene mutations of the corresponding tumors. These primary xenograft models are therefore considered to be reasonable models in which to recapitulate the clinical course of ccRCC treated with sunitinib. In our primary xenograft models, KURC1 and KURC2 tumors displayed different characteristics regarding sunitinib sensitivity. KURC1 developed resistance to sunitinib after 4 weeks of treatment but KURC2 remained sensitive for more than 6 months. Although there have been some reports that primary xenograft tumors acquire resistance to sunitinib, previous studies showed that re-transplanted tumors in the next cohort of other mice recovered sensitivity to sunitinib. Surprisingly, in our study, when resistant KURC1 tumors were resected, re-transplanted into other mice and repeatedly re-administered with sunitinib, KURC1 tumors finally demonstrated complete resistance to sunitinib after four passages. These different types of primary xenograft models were useful in our research in identifying novel mechanisms of development of sunitinib resistance. To explore the underlying mechanisms of acquired resistance, we performed a microarray analysis comparing sunitinib-resistant and-sensitive KURC1 with controls, and sunitinib-sensitive KURC2 with controls. Additionally, we performed whole exome sequencing to compare completely sunitinib-resistant KURC1 with controls. Some gene expression changes were identified by microarray analysis, but acquired somatic mutations were not found in the exon regions within these genes of interest. Therefore, we compared gene expression changes in our data set with those in previous reports and evaluated whether these gene expression changes were related to sunitinib resistance. The pro-angiogenic cytokine interleukin 8 was increased in the plasma of sunitinibresistant xenograft mice, and neutralization of IL-8 blocked tumor angiogenesis and caused tumor re-sensitization to sunitinib. Reduction of IFN-related angiostatic chemokines and restoration of CXCL9 delayed acquired resistance to anti-VEGF treatment. MMP1, SERPNTE1, ANGPTL4, NRP2, ARG2 and INSIG2 were elevated in sorafenib-resistant xenograft tumors derived from a 786-O cell line. However, these gene levels were not upregulated in our primary xenograft model treated with sunitinib. These findings 13 / 20 IL13RA2 and Resistance to Sunitinib in ccRCC 14 / 20 IL13RA2 and Resistance to Sunitinib in ccRCC Fig 5. Evaluation of apoptosis and microvessel density after sunitinib treatment in our primary xenograft models. ssDNA staining and CD31 staining of KURC1 treated with sunitinib or vehicle with different sensitivity status. Scale bar, 50 m. Apoptosis was assessed by calculating the ssDNA positivity rate, and MVD was determined from CD31 staining using Image J software. Statistical analysis was performed using the Students’ t-test. doi:10.1371/journal.pone.0130980.g005 suggested that another mech