Early detection of pemetrexed-induced inhibition of thymidylate synthase in non-small cell lung cancer with FLT-PET imaging.

Journal Article

Inhibition of thymidylate synthase (TS) results in a transient "flare" in DNA thymidine salvage pathway activity measurable with FLT ([18F]thymidine)-positron emission tomography (PET). Here we characterize this imaging strategy for potential clinical translation in non-small cell lung cancer (NSCLC). Since pemetrexed acts by inhibiting TS, we defined the kinetics of increases in thymidine salvage pathway mediated by TS inhibition following treatment with pemetrexed in vitro. Next, using a mouse model of NSCLC, we validated the kinetics of the pemetrexed-mediated "flare" in thymidine salvage pathway activity in vivo using FLT-PET imaging. Finally, we translated our findings into a proof-of-principle clinical trial of FLT-PET in a human NSCLC patient. In NSCLC cells in vitro, we identified a burst in pemetrexed-mediated thymidine salvage pathway activity, assessed by 3H-thymidine assays, thymidine kinase 1 (TK1) expression, and equilibrative nucleoside transporter 1 (ENT1) mobilization to the cell membrane, that peaked at 2hrs. This 2hr time-point was also optimal for FLT-PET imaging of pemetrexed-mediated TS inhibition in murine xenograft tumors and was demonstrated to be feasible in a NSCLC patient. FLT-PET imaging of pemetrexed-induced TS inhibition is optimal at 2hrs from therapy start; this timing is feasible in human clinical trials.

Full Text

Duke Authors

Cited Authors

  • Chen, X; Yang, Y; Berger, I; Khalid, U; Patel, A; Cai, J; Farwell, MD; Langer, C; Aggarwal, C; Albelda, SM; Katz, SI

Published Date

  • April 2017

Published In

Volume / Issue

  • 8 / 15

Start / End Page

  • 24213 - 24223

PubMed ID

  • 27655645

Pubmed Central ID

  • 27655645

Electronic International Standard Serial Number (EISSN)

  • 1949-2553

International Standard Serial Number (ISSN)

  • 1949-2553

Digital Object Identifier (DOI)

  • 10.18632/oncotarget.12085


  • eng