Biology and therapeutic applications of the proton-coupled folate transporter

The proton-coupled folate transporter (PCFT; SLC46A1) was discovered in 2006 as the principal mechanism by which folates are absorbed in the intestine and the causal basis for hereditary folate malabsorption (HFM). In 2011, it was found that PCFT is highly expressed in many tumors. This stimulated interest in using PCFT for cytotoxic drug targeting, taking advantage of the substantial levels of PCFT transport and acidic pH conditions commonly associated with tumors.

We summarize the literature from 2006 to 2022 that explores the role of PCFT in the intestinal absorption of dietary folates and its role in HFM and as a transporter of folates and antifolates such as pemetrexed (Alimta) in relation to cancer. We provide the rationale for the discovery of a new generation of targeted pyrrolo[2,3-d]pyrimidine antifolates with selective PCFT transport and inhibitory activity toward de novo purine biosynthesis in solid tumors. We summarize the benefits of this approach to cancer therapy and exciting new developments in the structural biology of PCFT and its potential to foster refinement of active structures of PCFT-targeted anti-cancer drugs.

We summarize the promising future and potential challenges of implementing PCFT-targeted therapeutics for HFM and a variety of cancers.