Search

Purpose: HIF2α is a key driver of kidney cancer. Using a belzutifan analogue (PT2399), we previously showed in tumorgrafts (TG) that ∼50% of clear cell renal cell carcinomas (ccRCC) are HIF2α dependent. However, prolonged treatment induced resistance mutations, which we also identified in humans. Here, we evaluated a tumor-directed, systemically delivered, siRNA drug (siHIF2) active against wild-type and resistant-mutant HIF2α. Experimental Design: Using our credentialed TG platform, we performed pharmacokinetic and pharmacodynamic analyses evaluating uptake, HIF2α silencing, target gene inactivation, and antitumor activity. Orthogonal RNA-sequencing studies of siHIF2 and PT2399 were pursued to define the HIF2 transcriptome. Analyses were extended to a TG line generated from a study biopsy of a siHIF2 phase I clinical trial (NCT04169711) participant and the corresponding patient, an extensively pretreated individual with rapidly progressive ccRCC and paraneoplastic polycythemia likely evidencing a HIF2 dependency. Results: siHIF2 was taken up by ccRCC TGs, effectively depleted HIF2α, deactivated orthogonally defined effector pathways (including Myc and novel E2F pathways), downregulated cell cycle genes, and inhibited tumor growth. Effects on the study subject TG mimicked those in the patient, where HIF2α was silenced in tumor biopsies, circulating erythropoietin was downregulated, polycythemia was suppressed, and a partial response was induced. Conclusions: To our knowledge, this is the first example of functional inactivation of an oncoprotein and tumor suppression with a systemic, tumor-directed, RNA-silencing drug. These studies provide a proof-of-principle of HIF2α inhibition by RNA-targeting drugs in ccRCC and establish a paradigm for tumor-directed RNA-based therapeutics in cancer.

Validation of Pax8-Cre;Vhl;Pbrm1 mice

By leveraging tumorgraft (patient-derived xenograft) RNA-sequencing data, we developed an empirical approach, DisHet, to dissect the tumor microenvironment (eTME). We found that 65% of previously defined immune signature genes are not abundantly expressed in renal cell carcinoma (RCC) and identified 610 novel immune/stromal transcripts. Using eTME, genomics, pathology, and medical record data involving >1,000 patients, we established an inflamed pan-RCC subtype (IS) enriched for regulatory T cells, natural killer cells, TH1 cells, neutrophils, macrophages, B cells, and CD8+ T cells. IS is enriched for aggressive RCCs, including BAP1-deficient clear-cell and type 2 papillary tumors. The IS subtype correlated with systemic manifestations of inflammation such as thrombocytosis and anemia, which are enigmatic predictors of poor prognosis. Furthermore, IS was a strong predictor of poor survival. Our analyses suggest that tumor cells drive the stromal immune response. These data provide a missing link between tumor cells, the TME, and systemic factors.Significance: We undertook a novel empirical approach to dissect the renal cell carcinoma TME by leveraging tumorgrafts. The dissection and downstream analyses uncovered missing links between tumor cells, the TME, systemic manifestations of inflammation, and poor prognosis. Cancer Discov; 8(9); 1142–55. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 1047

Supplementary Figure Legends

List of UTSW KCP patients with RNA-Seq and exome-seq. Sheet 1 contains information of 35 patients whose matched trio RNA-Seq data were used in the primary DisHet analyses. Sheet 2 contains information of patients whose bulk tumors were analyzed by RNA-Seq and whose follow up data are available. There are overlap between patients from these two sheets. Sheet 3 contains the information of tumorgraft data used in Fig. 5bc.

The full technical details of DisHet

Annotation of eTME genes. eTME genes (3x) are shown in the table. The "eTME (20x)" column shows eTME genes that satisfy the 20x cutoff. The other columns show the interpretation of the eTME genes using BLUEPRINT data, the Winslow signatures, Immunome signatures, and the ESTIMATE signature (immune and stromal signatures combined).

Gene ontology analysis shows enriched GO terms of the 904 eTME genes (20x cutoff) (first sheet), the 778 and the 610 eTME genes (20x cutoff) that are not captured by the Immunome alone and Immunome+ESTIMATE+Winslow gene signatures (second and third sheets).

Sup. Fig. 1 Simulation analyses show accurate dissection of bulk tumor RNA-Seq data by DisHet. Sup. Fig. 2 Validating immune/stroma component expression dissected by DisHet. Sup. Fig. 3 Comparison of dissection performance of DeMix and DisHet. Sup. Fig. 4 Principal Component Analysis (PCA) shows the clustering of TCGA pan-RCC patients tumors by the tumor-specific genes and eTME-specific genes, respectively. Sup. Fig. 5 CD4 and CD8 immunohistochemistry staining in the Six2-Cre;VhlF/F;Pbrm1F/F and Six2-Cre;VhlF/F;Bap1F/+. Supl. Fig. 6 Clinical manifestations of eTME-NIS patients.

Figure S5

Supp data legend

Purpose:HIF2α is a key driver of kidney cancer. Using a belzutifan analogue (PT2399), we previously showed in tumorgrafts (TG) that ∼50% of clear cell renal cell carcinomas (ccRCC) are HIF2α dependent. However, prolonged treatment induced resistance mutations, which we also identified in humans. Here, we evaluated a tumor-directed, systemically delivered, siRNA drug (siHIF2) active against wild-type and resistant-mutant HIF2α.Experimental Design:Using our credentialed TG platform, we performed pharmacokinetic and pharmacodynamic analyses evaluating uptake, HIF2α silencing, target gene inactivation, and antitumor activity. Orthogonal RNA-sequencing studies of siHIF2 and PT2399 were pursued to define the HIF2 transcriptome. Analyses were extended to a TG line generated from a study biopsy of a siHIF2 phase I clinical trial (NCT04169711) participant and the corresponding patient, an extensively pretreated individual with rapidly progressive ccRCC and paraneoplastic polycythemia likely evidencing a HIF2 dependency.Results:siHIF2 was taken up by ccRCC TGs, effectively depleted HIF2α, deactivated orthogonally defined effector pathways (including Myc and novel E2F pathways), downregulated cell cycle genes, and inhibited tumor growth. Effects on the study subject TG mimicked those in the patient, where HIF2α was silenced in tumor biopsies, circulating erythropoietin was downregulated, polycythemia was suppressed, and a partial response was induced.Conclusions:To our knowledge, this is the first example of functional inactivation of an oncoprotein and tumor suppression with a systemic, tumor-directed, RNA-silencing drug. These studies provide a proof-of-principle of HIF2α inhibition by RNA-targeting drugs in ccRCC and establish a paradigm for tumor-directed RNA-based therapeutics in cancer.

Table S2

Metastatic cohort, RECIST 1.1, Hazard Ratio

Purpose:The heterodimeric transcription factor HIF-2 is arguably the most important driver of clear cell renal cell carcinoma (ccRCC). Although considered undruggable, structural analyses at the University of Texas Southwestern Medical Center (UTSW, Dallas, TX) identified a vulnerability in the α subunit, which heterodimerizes with HIF1β, ultimately leading to the development of PT2385, a first-in-class inhibitor. PT2385 was safe and active in a first-in-human phase I clinical trial of patients with extensively pretreated ccRCC at UTSW and elsewhere. There were no dose-limiting toxicities, and disease control ≥4 months was achieved in 42% of patients.Patients and Methods:We conducted a prospective companion substudy involving a subset of patients enrolled in the phase I clinical trial at UTSW (n = 10), who were treated at the phase II dose or above, involving multiparametric MRI, blood draws, and serial biopsies for biochemical, whole exome, and RNA-sequencing studies.Results:PT2385 inhibited HIF-2 in nontumor tissues, as determined by a reduction in erythropoietin levels (a pharmacodynamic marker), in all but one patient, who had the lowest drug concentrations. PT2385 dissociated HIF-2 complexes in ccRCC metastases, and inhibited HIF-2 target gene expression. In contrast, HIF-1 complexes were unaffected. Prolonged PT2385 treatment resulted in the acquisition of resistance, and we identified a gatekeeper mutation (G323E) in HIF2α, which interferes with drug binding and precluded HIF-2 complex dissociation. In addition, we identified an acquired TP53 mutation elsewhere, suggesting a possible alternate mechanism of resistance.Conclusions:These findings demonstrate a core dependency on HIF-2 in metastatic ccRCC and establish PT2385 as a highly specific HIF-2 inhibitor in humans. New approaches will be required to target mutant HIF-2 beyond PT2385 or the closely related PT2977 (MK-6482).

Supplementary Figure S1. Pharmacodynamic analyses and illustrative mpMRI studies.

Supplementary Tables S2-S9.

Supplementary Data Legends

Methods describing MRI protocols, Image acquisition, and analysis, IHC analysis and cDNA library preparation.

Purpose:Intratumoral heterogeneity (ITH) challenges the molecular characterization of clear cell renal cell carcinoma (ccRCC) and is a confounding factor for therapy selection. Most approaches to evaluate ITH are limited by two-dimensional ex vivo tissue analyses. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can noninvasively assess the spatial landscape of entire tumors in their natural milieu. To assess the potential of DCE-MRI, we developed a vertically integrated radiogenomics colocalization approach for multi-region tissue acquisition and analyses. We investigated the potential of spatial imaging features to predict molecular subtypes using histopathologic and transcriptome correlatives.Experimental Design:We report the results of a prospective study of 49 patients with ccRCC who underwent DCE-MRI prior to nephrectomy. Surgical specimens were sectioned to match the MRI acquisition plane. RNA sequencing data from multi-region tumor sampling (80 samples) were correlated with percent enhancement on DCE-MRI in spatially colocalized regions of the tumor. Independently, we evaluated clinical applicability of our findings in 19 patients with metastatic RCC (39 metastases) treated with first-line antiangiogenic drugs or checkpoint inhibitors.Results:DCE-MRI identified tumor features associated with angiogenesis and inflammation, which differed within and across tumors, and likely contribute to the efficacy of antiangiogenic drugs and immunotherapies. Our vertically integrated analyses show that angiogenesis and inflammation frequently coexist and spatially anti-correlate in the same tumor. Furthermore, MRI contrast enhancement identifies phenotypes with better response to antiangiogenic therapy among patients with metastatic RCC.Conclusions:These findings have important implications for decision models based on biopsy samples and highlight the potential of more comprehensive imaging-based approaches.

Supplementary Figures

Supplementary Table S1. Multiparametric magnetic resonance imaging (mpMRI) acquisition parameters.

Purpose: Intratumoral heterogeneity (ITH) challenges the molecular characterization of clear cell renal cell carcinoma (ccRCC) and is a confounding factor for therapy selection. Most approaches to evaluate ITH are limited by two-dimensional ex vivo tissue analyses. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can noninvasively assess the spatial landscape of entire tumors in their natural milieu. To assess the potential of DCE-MRI, we developed a vertically integrated radiogenomics colocalization approach for multi-region tissue acquisition and analyses. We investigated the potential of spatial imaging features to predict molecular subtypes using histopathologic and transcriptome correlatives. Experimental Design: We report the results of a prospective study of 49 patients with ccRCC who underwent DCE-MRI prior to nephrectomy. Surgical specimens were sectioned to match the MRI acquisition plane. RNA sequencing data from multi-region tumor sampling (80 samples) were correlated with percent enhancement on DCE-MRI in spatially colocalized regions of the tumor. Independently, we evaluated clinical applicability of our findings in 19 patients with metastatic RCC (39 metastases) treated with first-line antiangiogenic drugs or checkpoint inhibitors. Results: DCE-MRI identified tumor features associated with angiogenesis and inflammation, which differed within and across tumors, and likely contribute to the efficacy of antiangiogenic drugs and immunotherapies. Our vertically integrated analyses show that angiogenesis and inflammation frequently coexist and spatially anti-correlate in the same tumor. Furthermore, MRI contrast enhancement identifies phenotypes with better response to antiangiogenic therapy among patients with metastatic RCC. Conclusions: These findings have important implications for decision models based on biopsy samples and highlight the potential of more comprehensive imaging-based approaches.

Active surveillance (AS) may be used in the management of metastatic renal cell carcinoma (mRCC), but consensus regarding its application is lacking. We report an exploratory analysis of prospectively collected data and specimens prespecified in the only modern clinical trial evaluating AS in mRCC. Whole-exome and RNA sequencing were performed for patients providing consent to identify putative biomarkers associated with time on AS (TAS), the primary endpoint. Log-rank tests and multivariable Cox proportional-hazards models were used for analyses. Patients with mutations in either TP53 or SMARCA4 tumor suppressor genes had shorter TAS (7.5 vs 14.2 mo; log-rank p = 0.004). While these patients exhibited features of aggressive disease clinically, the two-gene model was independently predictive in multivariable analyses (hazard ratio 3.30, 95% confidence interval 1.07–10.18; p = 0.038). In conclusion, insight into the underlying RCC biology improves patient selection for AS. If validated, this two-gene model could help in stratifying patients with mRCC and identifying those who are poor candidates for AS. PATIENT SUMMARY: In this study, we analyzed tumors from patients with metastatic kidney cancer enrolled in a clinical trial of imaging surveillance. We found that tumors with mutations in either the TP53 or SMARCA4 gene progressed faster than tumors without these mutations. Thus, patients harboring mutations in these genes benefit from immediate systemic therapy.

Purpose: The heterodimeric transcription factor HIF-2 is arguably the most important driver of clear cell renal cell carcinoma (ccRCC). Although considered undruggable, structural analyses at the University of Texas Southwestern Medical Center (UTSW, Dallas, TX) identified a vulnerability in the α subunit, which heterodimerizes with HIF1β, ultimately leading to the development of PT2385, a first-in-class inhibitor. PT2385 was safe and active in a first-in-human phase I clinical trial of patients with extensively pretreated ccRCC at UTSW and elsewhere. There were no dose-limiting toxicities, and disease control ≥4 months was achieved in 42% of patients. Patients and Methods: We conducted a prospective companion substudy involving a subset of patients enrolled in the phase I clinical trial at UTSW (n = 10), who were treated at the phase II dose or above, involving multiparametric MRI, blood draws, and serial biopsies for biochemical, whole exome, and RNA-sequencing studies. Results: PT2385 inhibited HIF-2 in nontumor tissues, as determined by a reduction in erythropoietin levels (a pharmacodynamic marker), in all but one patient, who had the lowest drug concentrations. PT2385 dissociated HIF-2 complexes in ccRCC metastases, and inhibited HIF-2 target gene expression. In contrast, HIF-1 complexes were unaffected. Prolonged PT2385 treatment resulted in the acquisition of resistance, and we identified a gatekeeper mutation (G323E) in HIF2α, which interferes with drug binding and precluded HIF-2 complex dissociation. In addition, we identified an acquired TP53 mutation elsewhere, suggesting a possible alternate mechanism of resistance. Conclusions: These findings demonstrate a core dependency on HIF-2 in metastatic ccRCC and establish PT2385 as a highly specific HIF-2 inhibitor in humans. New approaches will be required to target mutant HIF-2 beyond PT2385 or the closely related PT2977 (MK-6482).

Checkpoint inhibitors are approved for the treatment of urothelial bladder cancer. However, there have been no reports on the prognostic value of programmed-death receptor ligand 1 (PD-L1) expression in squamous cell carcinoma (SCC) of the bladder. We assessed the relationship between PD-L1 expression, clinicopathological features, and oncologic outcomes in bladder SCC.Immunohistochemistry of PD-L1 was performed on 151 radical cystectomy specimens with pure SCC treated in Mansoura, Egypt from 1997 to 2004.Median patient age was 52 years (range: 36-74 years) and median length of follow up was 63 months (range: 1-100 months). Schistosomiasis was present in 81% of the specimens and 93% had muscle-invasive disease on pathologic staging. PD-L1 expression was negative in 50 (33%) of the specimens. Negative PD-L1 expression was associated with higher pathologic tumor stage (P = 0.04), higher grade lesions (P = 0.01), and the presence of lymphovascular invasion (P0.01). Kaplan-Meier analyses showed that negative PD-L1 expression is associated with worse recurrence-free (P = 0.01) and worse cancer-specific survival (P = 0.01). Multivariable Cox regression analyses showed negative PD-L1 expression was an independent predictor of disease recurrence (hazards ratio 2.05, 95% confidence interval 1.06-3.96, P = 0.03) and cancer-specific mortality (hazards ratio 2.89, 95% confidence interval 1.22-6.82, P = 0.02).Negative PD-L1 expression is associated with higher pathologic tumor stage, higher grade lesions, presence of lymphovascular invasion, and worse oncologic outcomes after radical cystectomy for SCC. These findings support the need for the inclusion of patients with bladder SCC into immunotherapy clinical trials.

Metastasis is the principal cause of cancer related deaths. Tumor invasion is essential for metastatic spread. However, determinants of invasion are poorly understood. We addressed this knowledge gap by leveraging a unique attribute of kidney cancer. Renal tumors invade into large vessels forming tumor thrombi (TT) that migrate extending sometimes into the heart. Over a decade, we prospectively enrolled 83 ethnically-diverse patients undergoing surgical resection for grossly invasive tumors at UT Southwestern Kidney Cancer Program. In this study, we perform comprehensive histological analyses, integrate multi-region genomic studies, generate in vivo models, and execute functional studies to define tumor invasion and metastatic competence. We find that invasion is not always associated with the most aggressive clone. Driven by immediate early genes, invasion appears to be an opportunistic trait attained by subclones with diverse oncogenomic status in geospatial proximity to vasculature. We show that not all invasive tumors metastasize and identify determinants of metastatic competency. TT associated with metastases are characterized by higher grade, mTOR activation and a particular immune contexture. Moreover, TT grade is a better predictor of metastasis than overall tumor grade, which may have implications for clinical practice., Tumour thrombi (TT) are intravascular extensions of renal cell carcinomas (RCC) which often lead to distant metastases. Here the authors examine the determinants of vascular invasion and metastasis in a unique cohort of RCC patients with TT using multi-region genomics and in vivo models.

Renal cell carcinoma (RCC) is characterized by a particularly broad metastatic swath, and, enigmatically, when the pancreas is a destination, the disease is associated with improved survival. Intrigued by this observation, we sought to characterize the clinical behavior, therapeutic implications, and underlying biology. While pancreatic metastases (PM) are infrequent, we identified 31 patients across 2 institutional cohorts and show that improved survival is independent of established prognostic variables, that these tumors are exquisitely sensitive to antiangiogenic agents and resistant to immune checkpoint inhibitors (ICIs), and that they are characterized by a distinctive biology. Primary tumors of patients with PM exhibited frequent PBRM1 mutations, 3p loss, and 5q amplification, along with a lower frequency of aggressive features such as BAP1 mutations and loss of 9p, 14q, and 4q. Gene expression analyses revealed constrained evolution with remarkable uniformity, reduced effector T cell gene signatures, and increased angiogenesis. Similar findings were observed histopathologically. Thus, RCC metastatic to the pancreas is characterized by indolent biology, heightened angiogenesis, and an uninflamed stroma, likely underlying its good prognosis, sensitivity to antiangiogenic therapies, and refractoriness to ICI. These data suggest that metastatic organotropism may be an indicator of a particular biology with prognostic and treatment implications for patients.

By leveraging tumorgraft (patient-derived xenograft) RNA-sequencing data, we developed an empirical approach, DisHet, to dissect the tumor microenvironment (eTME). We found that 65% of previously defined immune signature genes are not abundantly expressed in renal cell carcinoma (RCC) and identified 610 novel immune/stromal transcripts. Using eTME, genomics, pathology, and medical record data involving >1,000 patients, we established an inflamed pan-RCC subtype (IS) enriched for regulatory T cells, natural killer cells, TH1 cells, neutrophils, macrophages, B cells, and CD8+ T cells. IS is enriched for aggressive RCCs, including BAP1-deficient clear-cell and type 2 papillary tumors. The IS subtype correlated with systemic manifestations of inflammation such as thrombocytosis and anemia, which are enigmatic predictors of poor prognosis. Furthermore, IS was a strong predictor of poor survival. Our analyses suggest that tumor cells drive the stromal immune response. These data provide a missing link between tumor cells, the TME, and systemic factors. Significance: We undertook a novel empirical approach to dissect the renal cell carcinoma TME by leveraging tumorgrafts. The dissection and downstream analyses uncovered missing links between tumor cells, the TME, systemic manifestations of inflammation, and poor prognosis. Cancer Discov; 8(9); 1142–55. ©2018 AACR. This article is highlighted in the In This Issue feature, p. 1047

Clear cell renal cell carcinoma (ccRCC) is characterized by BAP1 and PBRM1 mutations, which are associated with tumors of different grade and prognosis. However, whether BAP1 and PBRM1 loss causes ccRCC and determines tumor grade is unclear. We conditionally targeted Bap1 and Pbrm1 (with Vhl) in the mouse using several Cre drivers. Sglt2 and Villin proximal convoluted tubule drivers failed to cause tumorigenesis, challenging the conventional notion of ccRCC origins. In contrast, targeting with PAX8, a transcription factor frequently overexpressed in ccRCC, led to ccRCC of different grades. Bap1-deficient tumors were of high grade and showed greater mTORC1 activation than Pbrm1-deficient tumors, which exhibited longer latency. Disrupting one allele of the mTORC1 negative regulator, Tsc1, in Pbrm1-deficient kidneys triggered higher grade ccRCC. This study establishes Bap1 and Pbrm1 as lineage-specific drivers of ccRCC and histologic grade, implicates mTORC1 as a tumor grade rheostat, and suggests that ccRCCs arise from Bowman capsule cells. Significance: Determinants of tumor grade and aggressiveness across cancer types are poorly understood. Using ccRCC as a model, we show that Bap1 and Pbrm1 loss drives tumor grade. Furthermore, we show that the conversion from low grade to high grade can be promoted by activation of mTORC1. Cancer Discov; 7(8); 900–17. ©2017 AACR. See related commentary by Leung and Kim, p. 802. This article is highlighted in the In This Issue feature, p. 783

Introduction & Objectives: Patients with metastatic renal cell carcinoma (mRCC) involving the pancreas have been shown to exhibit a relatively indolent course, yet the biologic explanation is unclear. We sought to characterize the genomic landscape of patients with mRCC harboring pancreatic metastases (PM) to identify molecular drivers of pancreatic tropism. Materials & Methods: mRCC patients harboring PM from UTSW and Cleveland Clinic were identified. Clinicopathologic data and oncologic outcomes were analyzed. Samples were obtained from primary tumors, metastatic sites (including pancreatic or other distant metastases), and matched normal tissue. Whole exome (WES) and RNA sequencing of tumors was conducted. Patient-derived xenograft (PDX) models were generated from a subset of patients, and the engrafted tumors were analyzed. Results: 31 mRCC patients with PM were included with 54 tumor samples derived from the primary tumor or thrombus (24), PM (21), or other metastatic sites (9). Median follow-up was 101 months. Clinicopathologic characteristics were similar between the two institutional cohorts, and all but one patient were favorable or intermediate IMDC risk. All patients had clear cell histology. 8 patients (26%) were metastatic at diagnosis, and median time to metastasis in the remaining patients was 74 months (IQR 32-120). Overall (OS) and cancer-specific (CSS) survival did not vary by IMDC risk group. OS was strikingly superior for mRCC patients with PM than a historic control of mRCC patients without PM (p Conclusions: mRCC patients with PM exhibit remarkably favorable survival outcomes. The relatively indolent biology of these tumors is reflected histologically and genomically and can be recapitulated in PDX models. Understanding tumor heterogeneity may help refine prognostic models for mRCC and hold implications for improved personalization of therapy. Citation Format: Nirmish Singla, Jacob Choi, Oreoluwa Onabolu, Layton Woolford, Christina Stevens, Vanina Tcheuyap, Tiffani McKenzie, Zhiqun Xie, Tao Wang, Renee McKay, Alana Christie, Payal Kapur, Brian Rini, James Brugarolas. Comprehensive molecular and genomic characterization of pancreatic tropism in metastatic renal cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2505.

e16096 Background: The tropism of cancer metastases is poorly understood yet holds prognostic value. Clear cell renal cell carcinoma (ccRCC) exhibits a broad pattern of metastases, making it an optimal model to study organotropism. Notably, when ccRCC metastasizes to the pancreas (PM) independently of other sites, it is associated with favorable outcomes in patients for unclear reasons. Here, we comprehensively analyzed the clinical and molecular profile of patients with PM. Methods: RCC patients with PM from UTSW and Cleveland Clinic were identified. Clinicopathologic data and oncologic outcomes were analyzed. Whole exome sequencing (WES), RNAseq, and histologic assessment of primary and metastatic tumors from PM patients were conducted. Results: 31 RCC patients with PM were identified. We observed remarkably favorable outcomes in our PM cohort, with a median overall survival (OS) of 10.7 years from metastatic diagnosis and a long latency between initial diagnosis and development of metastasis (median 69 months in patients who were non-metastatic at diagnosis). OS was independent of both metastatic tumor burden and known IMDC prognostic factors. We discovered that tumors from PM patients were markedly uniform and clustered together by gene expression analysis. WES and DNA copy number analyses revealed a high frequency of VHL and PBRM1 mutations, 3p loss, and 5q amplification, along with a lower frequency of 9p, 14q and 4q losses and BAP1 mutations, characteristic of indolent ccRCC. Furthermore, the genomic and histologic features of tumors from patients with PM can be recapitulated in patient-derived xenograft models. Conclusions: To our knowledge, this is the first report to unravel molecular determinants of organotropism, and we highlight that organotropism can be an independent prognostic factor. Understanding tumor heterogeneity may help refine prognostic models for metastatic RCC and hold implications for improved personalization of therapy.

633 Background: Patients with metastatic renal cell carcinoma (mRCC) involving the pancreas have been shown to exhibit a relatively indolent course, yet the biologic explanation is unclear. We sought to characterize the genomic landscape of patients with mRCC harboring pancreatic metastases to identify molecular drivers of pancreatic tropism. Methods: mRCC patients harboring pancreatic metastases from UTSW and Cleveland Clinic were identified. Clinicopathologic data and oncologic outcomes were analyzed. Samples were obtained from primary tumors, metastatic sites (including pancreatic or other distant metastases), and matched normal tissue. Whole exome (WES) and RNA sequencing of tumors was conducted. Patient-derived xenograft (PDX) models were generated from a subset of patients, and the engrafted tumors were analyzed. Results: 31 mRCC patients with pancreatic metastases were included with 54 tumor samples derived from the primary tumor or thrombus (24), pancreatic metastasis (21), or other metastatic sites (9). Median follow-up was 101 months. Clinicopathologic characteristics were similar between the two institutional cohorts, and all but one patient were favorable or intermediate IMDC risk. All patients had clear cell histology. 8 patients (26%) were metastatic at diagnosis, and median time to metastasis in the remaining patients was 74 months (IQR 32-120). Overall (OS) and cancer-specific (CSS) survival did not vary by IMDC risk group. Morphologically, tumors largely displayed low-grade acinar patterns. WES with matched normal tissue and RNAseq were completed with adequate quality for 48 and 30 samples, respectively. 14 PDX lines were generated, of which 5 (36%) engrafted stably (≥2 passages). WES from 2 tumorgraft specimens revealed preservation of specific mutations in the corresponding human samples. Conclusions: mRCC patients with pancreatic metastases exhibit remarkably favorable survival outcomes. The relatively indolent biology of these tumors is reflected histologically and genomically and can be recapitulated in PDX models. Understanding tumor heterogeneity may help refine prognostic models for mRCC and hold implications for improved personalization of therapy.