Abstract A089: The effect of lactate dehydrogenase-A (LDH-A) knockdown and human prostate-specific membrane antigen (hPSMA) directed CAR T-cell treatment on hPSMA(+) Myc-CaP tumors

Objective: Determine whether LDH-A knockdown enhances CAR T-cell tumor-targeting and treatment response.Background: It has been shown that T-cells are restricted from entering many human and murine solid tumors, including both murine and human prostate tumors. CD3(+) T-cells are restricted from Myc-CaP murine prostate tumors and localize around the periphery of the tumor nodules (1). Human prostate specific membrane antigen (hPSMA) targeted CAR T-cells are also restricted from hPSMA(+) Myc-CaP tumors and this is only partially reversed by anti-PD1 treatment (1). This report describes the benefit of LDH-A depletion and a greater response of CAR T-cells targeting Myc-CaP tumors with low expression of LDH-A. Methods: LDH-A depletion in hPSMA(+) Myc-CaP cells bearing a bioluminescence reporter (Renilla Luciferase), was achieved by shRNA knockdown (KD) (1). A scrambled IgG shRNA was used as a control (NC). LDH-A expression was quantified by digital droplet PCR (ddPCR), Western blotting and LDH enzyme activity. The glycolytic activity of KD and NC cells was measured using Seahorse XF96 and XFp analyzers. Intratumoral lactate levels were monitored by magnetic resonance spectroscopy (MRS). The preparation and characterization of “second generation” hPSMA-directed CAR T-cells and the hPSMA(+) Myc-CaP tumor models in SCID mice have been described (1). To monitor CAR T-cell trafficking, T-cells were transduced with a Click Beetle Red luciferase reporter to enable efficient visualization by bioluminescence imaging (BLI) of CAR T-cell trafficking, persistence and viability within the hPSMA(+)Myc-CaP tumor mass. Tumor volume was calculated from caliper measurements. CD31 and PD-L1 expression was quantified with immunofluorescent staining and Metamorph Offline image analysis. Results and Discussion: These studies demonstrated that LDH-A KD was the dominant factor in reducing tumor growth. The difference in tumor doubling time (DT) between KD and NC tumors in the presence of CAR T-cell therapy was significant (p Citation Format: Mayuresh M. Mane, Khalid Shalaby, Ivan Cohen, Avi Albeg, Jenny Ijoma, Myat Ko, Masatomo Maeda, Kiranmayi Vemuri, Jaya Satagopan, Anna Moroz, Juan Zurita, Larissa Shenker, Ellen Ackerstaff, Masahiro Shindo, Ekaterina Moroz, Maxim A. Moroz, Inna Serganova, Jason Koutcher, Vladimir Ponomarev, Ronald G. Blasberg. The effect of lactate dehydrogenase-A (LDH-A) knockdown and human prostate-specific membrane antigen (hPSMA) directed CAR T-cell treatment on hPSMA(+) Myc-CaP tumors [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A089.