One of the most important goals that NCI has established in the area of cancer treatment has been for the conversion of cancer from an acute and lethal disease to a chronic condition that can be managed long term. Two requirements are needed to achieve this goal: 1) the development of new anticancer drugs and treatment regimens utilizing these drugs, and 2) the ability to accurately and non-invasively assess the effectiveness of these treatment regimens. Differentiating agents are an attractive possibility in this area of cancer treatment, for they are agents that can either cause reversion of the malignant phenotype or the triggering of apoptosis. Our goal in this project is to delineate the mechanisms by which phenylacetate (PA) and phenylbutyrate (PB), two differentiating agents currently under Phase II clinical trials, inhibit the proliferation of cancer cells. We will concentrate on the changes in phosphatidylcholine (PtdCho) metabolites that can be observed using in vivo magnetic resonance spectroscopy (MRS) with the goal of determining the spectroscopic indicators that can reliably be used as an index for the inhibition of proliferation and induction of apoptosis by PA and PB. This could provide a basis for clinical monitoring of response to differentiation therapy by 1H MRS. In vivo animal tumor studies will be combined with mechanistic studies on perfused cells, using MR spectroscopy with fluorescence microscopy, flow cytometry and molecular biology techniques to identify key checkpoints in PtdCho catabolism associated with differentiation therapy. Our preliminary studies indicate that PA and PB induce changes in MR-visible phospholipid metabolite levels that correlate with the induction of apoptosis. Using fluorescent phospholipase-activated phospholipid analogues, we have identified two different phospholipase activities in prostate cancer cells: one that is constitutive and primarily nuclear, and one that is cytoplasmic and inducible by PA or PB. Thus, the aims of this application are to i) measure in vitro and in vivo phospholipase activation induced by differentiating agents, ii) identify the phospholipase isoform contributing to spectral changes in PBinduced apoptosis; iii) examine the effects of phospholipase inhibition on the MR-visible metabolites in tumor cells undergoing apoptosis and iv) to investigate the potential of MR-visible resonances as a marker for response to differentiation therapy in murine tumor models. These studies provide a mechanistic underpinning for the changes induced in phospholipid metabolism by differentiation therapy and therefore constitute an important advance in the understanding of choline metabolism for the interpretation of in vivo MR spectra of tumors.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
1R01CA114347-01
Application #
6905382
Study Section
Medical Imaging Study Section (MEDI)
Program Officer
Liu, Guoying
Project Start
2005-05-13
Project End
2010-04-30
Budget Start
2005-05-13
Budget End
2006-04-30
Support Year
1
Fiscal Year
2005
Total Cost
$273,415
Indirect Cost
Name
University of Pennsylvania
Department
Radiation-Diagnostic/Oncology
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Mawn, Theresa M; Popov, Anatoliy V; Delikatny, E James (2012) A quantitative continuous enzyme assay of intramolecularly quenched fluorogenic phospholipase substrates for molecular imaging. Anal Biochem 422:96-102
Mawn, Theresa M; Popov, Anatoliy V; Beardsley, Nancy J et al. (2011) In vivo detection of phospholipase C by enzyme-activated near-infrared probes. Bioconjug Chem 22:2434-43
Delikatny, E James; Chawla, Sanjeev; Leung, Daniel-Joseph et al. (2011) MR-visible lipids and the tumor microenvironment. NMR Biomed 24:592-611
Milkevitch, Matthew; Beardsley, Nancy J; Delikatny, E James (2010) Phenylbutyrate induces apoptosis and lipid accumulations via a peroxisome proliferator-activated receptor gamma-dependent pathway. NMR Biomed 23:473-9
Popov, Anatoliy V; Mawn, Theresa M; Kim, Soungkyoo et al. (2010) Design and synthesis of phospholipase C and A2-activatable near-infrared fluorescent smart probes. Bioconjug Chem 21:1724-7
Milkevitch, Matthew; Jeitner, Thomas M; Beardsley, Nancy J et al. (2007) Lovastatin enhances phenylbutyrate-induced MR-visible glycerophosphocholine but not apoptosis in DU145 prostate cells. Biochim Biophys Acta 1771:1166-76