Abstract A35: Metabolomic profiling and the biochemical basis of prostate cancer racial disparity

African American (AA) men have an approximately 60% higher incidence of prostate cancer and are at 2 times greater risk of dying of prostate cancer than European Americans (EA). Environmental and socio-economic factors as well as a number of genetic alterations have been previously interrogated as possible explanations for this disparity. Currently, little is known about the specific biological pathway differences in prostate cancer between AA and EA men that may help explain the greater burden borne by AA men with this disease.

In this study, we seek to unravel and compare the prostate cancer metabolome of AA and EA men by employing state of the art metabolomic profiling and bioinformatic techniques. Based on the premise that metabolites are end products of enzyme action, we sought to identify a racially distinct biochemical signature for prostate cancer.

Fifty-six prostate cancer tissue samples from AA and EA men and their adjacent benign tissues (i.e., matched normal/tumor pairs) were analyzed using an unbiased liquid chromatography-coupled mass spectrometry approach. Differential metabolites were mapped into pathways and combined with bioinformatics-based bioprocess mapping to categorize metabolic differences observed in cancers of AA and EA origin. Our data indicate a specific and largely mutually exclusive metabolic signature for AA and EA derived prostate cancers. These findings may have important clinical implications and, importantly, shed new light on the biological basis of prostate cancer racial disparity.

Citation Format: Shaiju Kakkandan VareedKatrin Panzitt, Sumanta Basu, Vasanta Putluri, Tiffany Dorsey, Tiffany Wallace, Nagireddy Putluri, Sayeeduddin Mohammed, Michael Ittmann, Rick Kittles, George Michailidis, Stefan Ambs, Ganesh Palapattu, Arun Sreekumar. Metabolomic profiling and the biochemical basis of prostate cancer racial disparity. [abstract]. In: Proceedings of the Fifth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2012 Oct 27-30; San Diego, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2012;21(10 Suppl):Abstract nr A35.

Metabolomic profiling reveals potential markers and bioprocesses altered in bladder cancer progression

Although alterations in xenobiotic metabolism are considered causal in the development of bladder cancer, the precise mechanisms involved are poorly understood. In this study, we used high-throughput mass spectrometry to measure over 2,000 compounds in 58 clinical specimens, identifying 35 metabolites which exhibited significant changes in bladder cancer. This metabolic signature distinguished both normal and benign bladder from bladder cancer. Exploratory analyses of this metabolomic signature in urine showed promise in distinguishing bladder cancer from controls and also nonmuscle from muscle-invasive bladder cancer. Subsequent enrichment-based bioprocess mapping revealed alterations in phase I/II metabolism and suggested a possible role for DNA methylation in perturbing xenobiotic metabolism in bladder cancer. In particular, we validated tumor-associated hypermethylation in the cytochrome P450 1A1 (CYP1A1) and cytochrome P450 1B1 (CYP1B1) promoters of bladder cancer tissues by bisulfite sequence analysis and methylation-specific PCR and also by in vitro treatment of T-24 bladder cancer cell line with the DNA demethylating agent 5-aza-2'-deoxycytidine. Furthermore, we showed that expression of CYP1A1 and CYP1B1 was reduced significantly in an independent cohort of bladder cancer specimens compared with matched benign adjacent tissues. In summary, our findings identified candidate diagnostic and prognostic markers and highlighted mechanisms associated with the silencing of xenobiotic metabolism. The metabolomic signature we describe offers potential as a urinary biomarker for early detection and staging of bladder cancer, highlighting the utility of evaluating metabolomic profiles of cancer to gain insights into bioprocesses perturbed during tumor development and progression.

Metabolomic profiling reveals a role for androgen in activating amino acid metabolism and methylation in prostate cancer cells

Prostate cancer is the second leading cause of cancer related death in American men. Development and progression of clinically localized prostate cancer is highly dependent on androgen signaling. Metastatic tumors are initially responsive to anti-androgen therapy, however become resistant to this regimen upon progression. Genomic and proteomic studies have implicated a role for androgen in regulating metabolic processes in prostate cancer. However, there have been no metabolomic profiling studies conducted thus far that have examined androgen-regulated biochemical processes in prostate cancer. Here, we have used unbiased metabolomic profiling coupled with enrichment-based bioprocess mapping to obtain insights into the biochemical alterations mediated by androgen in prostate cancer cell lines. Our findings indicate that androgen exposure results in elevation of amino acid metabolism and alteration of methylation potential in prostate cancer cells. Further, metabolic phenotyping studies confirm higher flux through pathways associated with amino acid metabolism in prostate cancer cells treated with androgen. These findings provide insight into the potential biochemical processes regulated by androgen signaling in prostate cancer. Clinically, if validated, these pathways could be exploited to develop therapeutic strategies that supplement current androgen ablative treatments while the observed androgen-regulated metabolic signatures could be employed as biomarkers that presage the development of castrate-resistant prostate cancer.

Androgen-regulated metabolome in prostate cancer

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Background: Prostate cancer (PC) is the second most prevalent cancer among American men which is primarily treated by androgen ablation therapy. Although a number of patients respond to this regimen, a significant subset fail and the tumor invariably progresses into a hormone refractory metastatic state, which is lethal. Earlier we had reported the first unbiased metabolomic signature for localized and metastatic prostate cancer tissues. Advancing further, we attempt to delineate the subset of metabolome in prostate cancer which is regulated by androgen-action.

Methods: Androgen responsive (R22V1, LnCap and VCAP) and independent (PC3, DU145) PC cells and benign prostate epithelial cells (RWPE) were profiled for their metabolomic alterations using mass spectrometry. Extracted metabolome from these cells were profiles using a combination quadrupole-time-of-flight (Q-TOF) and triple quadrupole (QQQ) mass spectrometers coupled to reverse phase and aqueous normal phase chromatography. The metabolomic profiles were analyzed to delineate class-specific signatures which were interrogated for altered bioprocesses using Oncomine Concept Map (OCM, www.oncomine.org ). The androgen receptor (AR) regulated metabolome was verified using treatment of PC cells with synthetic androgen, R1881.

Results: A total of 3,092 metabolites (113 named) were detected across the 4 cells lines, of which 869 compounds were significantly (ANOVA P<0.01) different between androgen responsive and non-responsive cells. The differential compendia included 28 named metabolites, including sarcosine which was earlier shown to be elevated during PC development and progression. Bioprocess mapping of AR-regulated metabolome revealed enrichment of amino acid metabolism and methylation potential, both of which were earlier defined to be the hallmarks of PC development and progression.

Conclusions: The study defines AR-regulated metabolic signature which portrays enrichment of amino acid metabolism and methylation potential that are hallmarks of PC development and progression.

No significant financial relationships to disclose.

Multiplex panel of metabolomic markers for early detection of prostate cancer

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Background: Prostate cancer (PCa) is the second leading cause of cancer deaths among men in US. Prostate specific antigen (PSA) the clinical standard for early detection of PCa is not specific for the disease necessitating development of additional markers. Metabolites are stable, measurable in biological fluids and function as physiological indicators of the individual. Earlier we described the metabolomic alteration in PCa and nominated sarcosine as a tissue marker for PCa progression. Further, elevated sarcosine levels were seen in cancer urine. The current study describes a multiplex panel of metabolomic markers in urine that include sarcosine, for early detection of PCa.

Methods: A sensitive liquid chromatography- mass spectrometry based assay was used to quantify relative levels of tissue specific metabolites in urine of PCa patients. The urine specimens examined in this study were collected at University of Michigan from post DRE and pre-biopsy from clinically challenging patients with PSA between 4-10 ng/mL where biopsy was either positive or negative for tumor. The urine supernatants were recovered post-centrifugation, adjusted to have an osmolarity between 350-400 mOsm/kg, spiked with defined amount of internal standards and evaluated by multiple reaction monitoring (MRM) using a triple quadrupole mass spectrometer. The MRM data was examined using random-forest (RF)-to generate a panel of discriminatory compounds that were validated in an independent test set.

Results: A panel of 11 metabolites (glutamic acid, sarcosine, spermidine, histidine, methionine, adenosine, inosine, thymine, hydroxyphenyl lactic acid, acetyl valine and lauric acid) when employed in a RF-based 2-stage training model (n=63) delineated PCa and benign with a cross-validated (out-of-bag validation based on 20000 decision trees) accuracy of 76 %. When applied to an independent set of test samples (n=98) from the same cohort the accuracy, sensitivity, specificity, positive predictive value and negative predictive values were 72 %, 77.5 %, 62.5 %, 67.8 % and 73.2 % respectively.

Conclusions: The study describes a first-generation multiplex panel of metabolic markers for early detection of PCa in urine supernatants.

No significant financial relationships to disclose.

Use of metabolomic profiling to identify potential markers and mechanism for bladder cancer progression

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Background: Bladder cancer (BCa) is the second most prevalent urological malignancy and the fourth highest cause of cancer-related death in the United States that is known to be caused by defects in xenobiotic metabolism, which is not well understood. Using unbiased mass spectrometry we report the metabolomic profiles in BCa tissues and demonstrate its biomarker potential as well reveal a possible mechanism regulating altered xenobiotic metabolism in these tumors.

Methods: Total metabolome from clinically annotated bladder-derived tissues were examined using mass spectrometry coupled to reverse and aqueous normal phase separation of compounds. Class- specific metabolites were examined in urine specimens for their biomarker potential as well as analyzed using Oncomine Concept Map for alterations in bioprocesses. The latter was validated using a collection of molecular techniques like Q-PCR, immunoblot analysis, methylation assays and use of methyl transferase inhibitor, on bladder-derived cell lines and patients specimens.

Results: A total of 2,019 compounds were detected across the 58 bladder-derived specimens, of which 50 named compounds were differential between BCa and its adjacent benign tissue. These included aromatic compounds like aniline, catechols as well as polyamines and S-adenosyl methionine (SAM). A subset of these compounds, were detected in urine and could distinguish BCa from benign, non-muscle-invasive from muscle invasive tumors and delineate patients responding to chemotherapy and TURBT. Bioprocess mapping of BCa-specific metabolome revealed co-enriched concepts describing methylation and cytochrome P450 (CYP) driven xenobiotic metabolism in bladder tumors. The role of methylation in regulation of CYP activity in BCa was confirmed using a combination of Aza-treatment, methylation-specific PCR and bisulphite sequencing on bladder-derived cell lines and tissues.

Conclusions: Unbiased metabolomic profiling reveals potential non-invasive metabolic markers for early detection, prognosis and therapeutic response of BCa as well as describes a role for methylation induced silencing of CYP1A1 and 1B1resulting in deficient xenobiotic metabolism in BCa.

No significant financial relationships to disclose.

Abstract A52: Metabolomic profiling reveals impaired xenobiotic metabolism in bladder cancer

Introduction: Bladder cancer (BCa) is the second most prevalent urological malignancy and the fourth highest cause of cancer-related death in the United States. Earlier studies have linked BCa development to alterations in metabolic pathways. Significant among these are decreased activity of N-acetyl transferases causing a slow-acetylator phenotype leading to inefficient detoxification of aromatic hydrocarbons causal to onset of BCa. Interestingly, Afro-American patients inherently exhibit such slow acetylator phenotype and are known to have a more aggressive form of the tumor compared to Caucasians. This indicates existence of a metabolic niche that governs the racial disparity in BCa, which is not well understood. Also, there is an imminent need to develop non-invasive markers for early detection and prognosis of BCa, since urine cytology which is the current clinical standard is not specific to the tumor. Using mass spectrometry we report metabolic alterations in BCa and delineate bioprocesses that are altered during its progression. Our data for the first-time demonstrates role of methylation in attenuation of xenotbiotic metabolism in BCa. Furthermore, the metabolic profiles seed further analysis to examine the racial disparity in these tumors.

Methods: Total metabolome from flash frozen clinically annotated bladder-derived tissues (n=58,31 benign adjacent and 27 BCa, 26 matched pairs) were examined using a combination of Q-TOF (unbiased) and triple-quadrupole (targeted) mass spectrometry. Panel of well-defined standards were used to ensure reproducibility of the profiling process. The metabolites were pre-fractionated using liquid chromatography prior to mass spectrometry in both the positive and negative ionization mode. The unbiased mass spectral data was searched using Metlin library to identify the compounds. The metabolomic profiles thus generated were analyzed to delineate class-specific signatures which were interrogated for altered bioprocesses using Molecular Concept Map (OCM, www.oncomine.org). The altered bioprocesses were validated in cell line models using a combination of Q-PCR, immunoblot analysis and functional assays.

Results and discussion: A total of 2019 compounds were detected across the 58 bladder-derived specimens of which, 423 compounds were significantly altered in BCa compared to adjacent benign. 50 of the differential compounds were named and used for developing a classificatory signature and bioprocess mapping. Included among these were polycylic compounds like aniline, catechols, aromatic amino acids, polyamines and S-adenosyl methionine (SAM). Interestingly this BCa-specific metabolic signature in tissues was able to delineate tumor from benign with an accuracy of 75 %. Importantly the functional mapping of the metabolic data revealed enhanced methylation potential in tumors as being one of the factors de-regulating the xenobiotic metabolism. In vitro experiments using bisulfite sequencing and methyltransferase inhibitor 5-Aza-cytidine confirmed this methylation-induced attenuation of phase I/II metabolic genes namely CYP1A1, CYP1B1, EPHX1 and GSTT1 in BCa. In summary, using unbiased metabolomic profiling report metabolic fingerprint for bladder cancer. Importantly our data for the first time reveals methylation-induced silencing of xenobiotic metabolism in bladder tumors.

Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):A52.