Success Story

July 8, 2019

New insight into liver cancer treatment

CBC Awardee Rick Silverman and a CBC Senior Investigator, Neil Kelleher, NU, collaborate on developing therapeutics for hepatocellular carcinoma (HCC)

Richard Silverman, NU

Congratulations to NU scientists Rick Silverman and Neil Kelleher on their recent publication in the Journal of the American Chemical Society, titled “Mechanism of Inactivation of Ornithine Aminotransferase by (1 S,3 S)-3-Amino-4-(hexafluoropropan-2-ylidenyl)cyclopentane-1-carboxylic Acid.”

The paper addresses new efforts towards developing drugs for hepatocellular carcinoma (HCC) — the most common form of liver cancer for which there is currently no effective treatment. The inhibition / inactivation of an enzyme called ornithine aminotransferase (OAT) has been implicated as a potential therapeutic pathway for HCC and the authors of the current study have previously identified several inhibitors of OAT. Here, they proceed to characterize the mechanism(s) of OAT inactivation and report that a two-step modification resulting in an addition of a trifluoromethyl group appears to be key to the process. This discovery provides an important start-point towards further development and optimization of potential HCC therapeutics.

Rick Silverman, the Patrick G. Ryan/Aon Professor of Chemistry at NU, is senior author on the publication. Rick is an active CBC community member and in 2018, he won an inaugural CBC Accelerator Award for the project: “Novel Drug for Hepatocellular Carcinoma.” Neil Kelleher, one of co-authors on the paper is a CBC Senior Investigator, who was hired in 2010 by NU with help from a generous CBC Recruitment Funds Award. Additional CBC connections of both researchers are listed below.


Publication linked to CBC funding*:

Moschitto MJ, Doubleday PF, Catlin DS, Kelleher NL, Liu D, Silverman RB. Mechanism of Inactivation of Ornithine Aminotransferase by (1 S,3 S)-3-Amino-4-(hexafluoropropan-2-ylidenyl)cyclopentane-1-carboxylic Acid. J Am Chem Soc. 2019 Jun 28. [Epub ahead of print] (PubMed)


ABSTRACT

The inhibition of ornithine aminotransferase (OAT), a pyridoxal 5′-phosphate-dependent enzyme, has been implicated as a treatment for hepatocellular carcinoma (HCC), the most common form of liver cancer, for which there is no effective treatment. From a previous evaluation of our aminotransferase inhibitors, (1 S,3 S)-3-amino-4-(perfluoropropan-2-ylidene)cyclopentane-1-carboxylic acid hydrochloride (1) was found to be a selective and potent inactivator of human OAT ( hOAT), which inhibited the growth of HCC in athymic mice implanted with human-derived HCC, even at a dose of 0.1 mg/kg. Currently, investigational new drug (IND)-enabling studies with 1 are underway. The inactivation mechanism of 1, however, has proved to be elusive. Here we propose three possible mechanisms, based on mechanisms of known aminotransferase inactivators: Michael addition, enamine addition, and fluoride ion elimination followed by conjugate addition. On the basis of crystallography and intact protein mass spectrometry, it was determined that 1 inactivates hOAT through fluoride ion elimination to an activated 1,1′-difluoroolefin, followed by conjugate addition and hydrolysis. This result was confirmed with additional studies, including the detection of the cofactor structure by mass spectrometry and through the identification of turnover metabolites. On the basis of this inactivation mechanism and to provide further evidence for the mechanism, analogues of 1 (19, 20) were designed, synthesized, and demonstrated to have the predicted selective inactivation mechanism. These analogues highlight the importance of the trifluoromethyl group and provide a basis for future inactivator design.

 

Graphical abstract. (Source: dx.doi.org)


Featured CBC Community member(s):

Richard Silverman, NU

Neil Kelleher, NU

ARTICLES PUBLISHED IN THE PAST ABOUT THE FEATURED CBC COMMUNITY MEMBER(S):

June 17, 2019
▸ Copper centers revealed with top-down mass spectrometry
Three CBC Awards contribute to today’s publication in Nature Communications!

May 13, 2019
▸ Battling epigenetic lymphomas
CBC Senior Investigator Neil Kelleher, NU, contributes to a new publication identifying a potential novel therapeutic pathway to treat the so called EZH2 dysregulated lymphomas

May 7, 2019
▸ Proteoforms explained
A recent review in Proteomics, co-authored by a CBC Senior Investigator and proteomics expert, Neil Kelleher, NU

August 9, 2018
▸ Top-down Proteomics
CBC Senior Investigator, Neil Kelleher, NU, explains the advantages of “top-down” versus “bottom-up” proteomics in early cancer detection and progression

April 25, 2018
▸ Using ‘top-down proteomics,’ CBC Senior Investigator, Neil Kelleher, NU, identifies and precisely measures eleven KRAS oncogene proteoforms found in colon cancer cells

April 13, 2018
▸ Past CBC awardee and frequent presenter at CBC-organized events, Rick Silverman, NU, highlighted in the journal Science, for his work to develop novel anti-addiction drugs

March 28, 2018
▸ New insights into the mechanism of methane metabolism by copper-binding bacteria revealed in a study from the Rosenzweig lab and CBC Senior Investigator, Neil Kelleher, NU

March 26, 2018
▸ New, cell-free protein manufacturing methodology, developed by Michael Jewett’s NU team and supported by CBC funding, could have important implications in biomedicine and beyond

November 23, 2017
▸ CBC’s mission of collaboration embraced through inter-institutional teaching and mentoring. Featuring Northwestern’s Chemistry of Life Processes Institute (CLP) Predoctoral Training Program.

November 13, 2017
▸ New insights into regulation of gene expression: work from the Shilatifard lab (NU) with contributions from two CBC scientists, Neil Kelleher and Jeffrey Savas.

October 5, 2017
▸ CBC Senior Investigator, Neil Kelleher, NU, deciphers molecular assembly of a gut toxin, colibactin

August 5, 2015
▸ Researchers Design First Artificial Ribosome

February 9, 2016
▸ “Clasping” Collaboration
Three CBC Scientists Join Forces to Develop Exceptional-Quality Antibodies Displaying an Unprecedented Mode of Action