Shenoy, Niraj

Significance This study demonstrates that underexpression of succinate dehydrogenase (SDH) subunits resulting in accumulation of oncogenic succinate is a common, adverse, epigenetic modulating feature in clear cell renal cell carcinoma (ccRCC), during pathogenesis and progression. The study sheds light on the mechanisms of down-regulation of SDH subunits in ccRCC and deciphers the consequent oncogenic effects. It shows that functional SDH deficiency is a common feature of ccRCC (∼80% of all kidney cancers), and not just limited to the 0.05 to 0.5% of kidney cancers with germline SDH mutations.

e13073 Background: We observed several patients with a personal history of both RCC and myeloid malignancy, and aimed to explore a possible association, especially given the similarity in their epigenetic landscape, with both being characterized by widespread aberrant hypermethylation (Hu C et al, CCR 2014; Jiang Y et al, Blood 2009). Methods: Mayo Clinic’s ‘Advanced Cohort Explorer’ database was used to identify patients with a history of both RCC and a myeloid malignancy - Acute Myelogenous Leukemia (AML), Myeloproliferative Neoplasms (MPN), Myelodysplastic syndromes (MDS) - and to determine the clinical characteristics. The incidence of MDS in patients ≥65 years with a history of RCC was compared to that in the general population ≥65 years (SEER- Medicare database) as well as the general patient population at Mayo Clinic, using one sample test of proportions. Results: A total of 59 patients were identified, with both biopsy proven RCC and a myeloid malignancy during their life time (12 AML, 9 MPN, 9 low risk MDS and 29 intermediate- high risk MDS). The cohort was characterized by marked male predominance (4.4: 1). Median age at RCC diagnosis was 64 years (range 37-87) and myeloid malignancy was 75 years (range 44-90). 46/59 patients had the RCC antecedent, 10/59 concurrent and 3/59 subsequent to the myeloid malignancy with a median time of myeloid malignancy diagnosis after RCC diagnosis of 7.7 years. For patients ≥65 years, the risk of developing MDS with a history of stage I/II RCC and nephrectomy was 5.26 times that of the general population based on the SEER-Medicare database (Cogle, Blood 2011)(395/100,000 vs 75/100,000; p value < 0.001), and 3.07 times that of the general population at Mayo Clinic (395/100,000 vs 128.4/100,000; p value < 0. 001). Conclusions: We observed an association between RCC and myeloid malignancies, particularly MDS; with a history of RCC conferring a substantially increased risk of developing MDS. We hypothesize that the perturbation of epigenetic landscape in the form of widespread hypermethylation may explain, in part, the association between the two malignancies; and aim to explore the potential aberrancy of epigenetic regulators in our patient cohort with a genomic, epigenomic and transcriptomic analysis.

479 Background: We and others have previously shown that the ccRCC epigenome is characterized by widespread DNA hypermethylation (CCR 2014, Nature 2014). Various important tumor suppressor genes (TSGs), such as SMAD7 (inhibitor of oncogenic TGF-β signaling), are under-expressed due to aberrantly methylated promoters or enhancers. We hypothesized that the hypermethylation in ccRCC could be due to low activity of the TET enzymes, which convert methylcytosine (5-mc) to hydroxymethylcytosine (5-hmc). Loss of function of TET enzymes can occur with an inactivating mutation (TET-2 is mutated in about 6% of ccRCC (Science Signaling 2013) or hypoactivity of normal TET enzymes, through inhibition by metabolic intermediates. AA is an essential co-factor for TET enzymes (JACS 2015). We hypothesized that high dose AA treatment of ccRCC could potentially increase the functional activity of TET enzymes leading to demethylation of the RCC genome, and enhance expression of TSGs. Methods: In vitro TET activity was performed on ccRCC cell line 769P with increasing doses of AA (L-AA). Genome wide quantitative 5-mc and 5-hmc was evaluated using mass spectrometry. SMAD7 expression was determined using qRT-PCR. Proliferation assay (MTT) was performed with AA in combination with pazopanib. Cell cycle and apoptosis assays were performed. Results: AA, at doses achieved only by the intravenous route (1-10mM), increased TET activity in ccRCC cell line 769P. Genome wide 5-mc was significantly reduced and 5-hmc was increased, correlating with increase in TET activity. SMAD7 expression was increased with AA treatment. High dose AA led to proliferation inhibition with a cell cycle arrest in the G1 phase, and had a synergistic effect with pazopanib. Since AA leads to the generation of H2O2 in-vitro, catalase was used as control. This did not reverse the effect of AA on epigenetic changes; and proliferation inhibition was seen despite catalase control. Conclusions: High dose AA causes TET mediated DNA demethylation of the hypermethylated RCC genome, resulting in the re-expression of TSGs, and proliferation inhibition. Sequencing and xenograft studies are underway.