Dual Targeting of Epithelial Ovarian Cancer Via Folate Receptor alpha and the Proton-Coupled Folate Transporter with 6-Substituted Pyrrolo[2,3-d] pyrimidine Antifolates

作者：Hou Zhanjun^*; Gattoc Leda; O'Connor Carrie; Yang Si; Wallace Povirk Adrianne; George Christina; Orr Steve; Polin Lisa; White Kathryn; Kushner Juiwanna; Morris Robert T; Gangjee Aleem^*; Matherly Larry H^*

来源：Molecular Cancer Therapeutics, 2017, 16(5): 819-830.

DOI：10.1158/1535-7163.MCT-16-0444

Folate uptake in epithelial ovarian cancer (EOC) involves the reduced folate carrier (RFC) and the proton-coupled folate transporter (PCFT), both facilitative transporters and folate receptor (FR) alpha. Although in primary EOC specimens, FR alpha is widely expressed and increases with tumor stage, PCFT was expressed independent of tumor stage (by real-time RT-PCR and IHC). EOC cell line models, including cisplatin sensitive (IGROV1 and A2780) and resistant (SKOV3 and TOV112D) cells, expressed a 17-fold range of FR alpha and similar amounts (within similar to 2-fold) of PCFT. Novel 6-substituted pyrrolo[2,3-d] pyrimidine thienoyl antifolates AGF94 and AGF154 exhibited potent antiproliferative activities toward all of the EOC cell lines, reflecting selective cellular uptake by FR alpha and/or PCFT over RFC. When IGROV1 cells were pretreated with AGF94 at pH 6.8, clonogenicity was potently inhibited, confirming cell killing. FR alpha was knocked down in IGROV1 cells with lentiviral shRNAs. Two FR alpha knockdown clones (KD-4 and KD-10) showed markedly reduced binding and uptake of [3H] folic acid and [3H] AGF154 by FR alpha, but maintained high levels of [3H] AGF154 uptake by PCFT compared to nontargeted control cells. In proliferation assays, KD-4 and KD-10 cells preserved in vitro inhibition by AGF94 and AGF154, compared to a nontargeted control, attributable to residual FR alpha- and substantial PCFT-mediated uptake. KD-10 tumor xenografts in severe-compromised immune-deficient mice were likewise sensitive to AGF94. Collectively, our results demonstrate the substantial therapeutic potential of novel 6-substituted pyrrolo[2,3-d] pyrimidine antifolates with dual targeting of PCFT and FR alpha toward EOCs that express a range of FR alpha, along with PCFT, as well as cisplatin resistance.

• 出版日期2017-5