Abstract 9: Metabolic profiling of bladder cancer cell lines reveals molecular alterations involved in methylation and novel epigenetic phenotype
Authors: Krishnapuram Rashmi , Gu Franklin , Bhowmik Salil Kumar , Maity Suman , Manikkam Mohan , von Rundstedt Friedrich-Carl , Putluri Vasanta , Lotan Yair , Levitt Jonathan M. , Lerner Seth P. , Coarfa Cristian , Sreekumar Arun , Putlurip Nagireddy 
Published: July 2016

Background: Bladder cancer (BCa) is primarily “carcinogen driven cancer”. Epidemiological studies indicate environmental factors play a major causative role compared to genetic factors. Xenobiotic metabolism is highly perturbed and precise mechanisms involved are poorly understood during BCa progression. We identified metabolic signature that can distinguish bladder cancer from controls and reveals major alterations in phaseI/II enzymes involved in xenobiotic metabolism and suggest a key role for epigenetic modifications.

Material and Methods:

In this study, we used mass spectrometry based metabolomics profiling coupled with enrichment-based bioprocess mapping to obtain insight into biochemical alterations in bladder cancer cell lines. We further validated related gene expression using real time quantitative PCR (qPCR) and proteins using western blotting.

Results:

In this study, we used high-throughput mass spectrometry to measure over 350 compounds in seven bladder cell lines, identifying 91 metabolites which exhibited significant changes in bladder Cancer. Most importantly, methylated, hydroxylated and acetylated metabolites are altered. Interestingly, S-Adenosyl methionine (SAM) is the most prominent pathway upregulated corroborated with our previous findings obtained using patient derived metabolomic data from two independent cohorts. Second, we observe many of phaseI/phaseII metabolic enzymes including aldehyde oxidase (AOX1), cytochrome P450 1A1 (CYP1A1), CYP1B1, Glutathione S-transferase T1 (GSTT1), Glutathione S-transferase M2 (GSTM2), N-acetyl transferase I NAT1 and NAT2 are transcriptionally repressed in BCa cell line compared to benign indicating the pivotal role of methylation in gene silencing. Interestingly, we observe differential expression of polycomb group of proteins (Pcg) associated with PRC2 and PRC1 complex. Specifically, histone-lysine N-methyl transferase (EZH2) protein, which is SAM dependent histone methyl transferase and concomitant 3meHK27 trimethylated histone K27, is highly expressed in metastatic UMUC3 BCa cell line further indicating prominence of epigenetic modifications.

Conclusion:

We present an integrative pathway analysis of a metabolic gene signature which has not been previously described in the context of bladder cancer cell lines. Further mechanistic analyses reveals prominent role for methylation status and associated epigenetic modifications being played in the transcriptional repression of key xenobiotic enzymes. Collectively, our novel findings provide an opportunity for development of efficient biomarker implications and epigenetic therapy targeting BCa progression.

Citation Format: Rashmi Krishnapuram, Franklin Gu, Salil Kumar Bhowmik, Suman Maity, Mohan Manikkam, Friedrich-Carl von Rundstedt, Vasanta Putluri, Yair Lotan, Jonathan M. Levitt, Seth P. Lerner, Cristian Coarfa, Arun Sreekumar, Nagireddy Putlurip. Metabolic profiling of bladder cancer cell lines reveals molecular alterations involved in methylation and novel epigenetic phenotype. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 9.