TY - JOUR T1 - Targeting Non-Squamous Non-Small Cell Lung Cancer Via the Proton-Coupled Folate Transporter with 6-Substituted Pyrrolo[2,3-d]Pyrimidine Thienoyl Antifolates JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.115.102798 SP - mol.115.102798 AU - Mike R Wilson AU - Zhanjun Hou AU - Si Yang AU - Lisa Polin AU - Juiwanna Kushner AU - Kathryn White AU - Jenny Huang AU - Manohar Ratnam AU - Aleem Gangjee AU - Larry H. Matherly Y1 - 2016/01/01 UR - http://molpharm.aspetjournals.org/content/early/2016/02/02/mol.115.102798.abstract N2 - Pemetrexed (PMX) is a 5-substituted pyrrolo[2,3-d]pyrimidine antifolate used for therapy of non-squamous non-small cell lung cancer (NS-NSCLC). PMX is transported by the reduced folate carrier (RFC) and proton-coupled folate transporter (PCFT). Unlike RFC, PCFT is active at acidic pHs characterizing the tumor microenvironment. By real-time RT-PCR and immunohistochemistry, PCFT transcripts and proteins were detected in primary NS-NSCLC specimens. In 6 NS-NSCLC cell lines (A549, H1437, H460, H1299, H1650, and H2030) PCFT transcripts and proteins were detected by real-time RT-PCR and western blots, respectively. 6-Substituted pyrrolo[2,3-d]pyrimidine thienoyl antifolates related to PMX (C1 and C2, respectively) are selective substrates for PCFT over RFC. In the NS-NSCLC cell lines, both [3H]PMX and [3H]C2 were transported by PCFT. C1 and C2 inhibited proliferation of the NS-NSCLC cell lines; A549, H460, and H2030 cells were more sensitive to C1 than to PMX. C1 and C2 inhibited glycinamide ribonucleotide formyltransferase in de novo purine nucleotide biosynthesis. When treated at pH 6.8, which favors PCFT uptake, C1 and C2 inhibited clonogenicity of H460 cells greater than PMX; PMX inhibited clonogenicity more than C1 or C2 at pH 7.2 which favors RFC transport over PCFT. Knockdown of PCFT in H460 cells resulted in decreased [3H]PMX and [3H]C2 transport and decreased growth inhibition by C1, C2 and, to a lesser extent, PMX. In vivo efficacy of C1 was seen toward H460 tumor xenografts in severe-combined immunodeficient mice. Our results suggest that 6-substituted pyrrolo[2,3-d]pyrimidine thienoyl antifolates offer significant promise for treating NS-NSCLC by selective uptake by PCFT. ER -