Abstract 3602: TRAIL-NK-92 MI as a novel adoptive therapy for castration-resistant prostate cancer (CRPC): Preliminary in vitro results
Authors: Schwermann Maximilian , Srinivasan Praveen , MacDonald William , Tajiknia Vida , Schmidt Andrea , Zhang Shengliang , Carlsen Lindsey , George Andrew , Purcell Connor , Lu Shaolei , Hadfield Matthew , Mega Anthony , Carneiro Benedito , El-Deiry Wafik 
Published: March 2024

Introduction: Natural killer (NK) cell tumor infiltration and higher expression of activating receptors NKp30 and NKp46 are associated with improved clinical outcomes in prostate cancer (PC). Activation of NK cells by androgen receptor inhibitors enhanced the killing of PC cell lines (Schwermann 2023). These findings support the therapeutic potential of strategies inducing NK cell activation to treat CRPC. NK cells induce apoptosis of cancer cells via TNF-related apoptosis-inducing ligand) (TRAIL) binding of death receptor 5 (DR5), which is overexpressed in PC cells. This is the first report of adoptive therapy utilizing high expression of TRAIL as a novel therapeutic strategy.

Methods: We transduced NK-92-MI and CD4+ (Jurkat) cell lines with human TRAIL (pLVX-EF1alpha-TRAIL-IRES-eGFP).Transduced cells were pre-treated with simvastatin or atorvastatin (4uM) for 36h, followed by stimulation (IL-2 100 IU/ml and IL-12 100 ng/ml) for 2h. The eGFP-expressing cells were then sorted by FACS. PC (PC3, DU145, LNCaP, and 22Rv1), fibroblast (IMR-90), and brain endothelial (hCMEC/D3) cell lines were used in co-culture experiments with non-transduced and transduced NK cells and CD4+ cells. These experiments were quantified using the ImageXpress Confocal HT instrument. Viability assays were performed using Annexin-PI and flow cytometry staining for caspases 3/7.

Results: Transduced NK-92 MI cells with TRAIL displayed increased surface expression of TRAIL (control[C]: 4.38%±1; TRAIL-overexpression[NK-TRAIL]: 78.54%±3.76; p&lt;0.001). Co-culture of PC cell lines with TRAIL-NK-92 MI cells resulted in significant tumor-induced apoptosis compared to co-culture with non-transduced NK cells after 48 hours (LNCaP + NK [C]: 16.52%±5, LNCaP + NK-TRAIL: 73.19%±6; PC [C]: 14.4%±3, PC3 + NK-TRAIL: 79%±8; 22Rv1 [C]: 16.78%±1.7, 22Rv1 + NK-TRAIL: 76%±8; DU145 [C]: 13%±4, DU145 + NK-TRAIL: 59.1%±10; p&lt;0.001). This enhanced cytotoxic function was also observed in CD4+ cells expressing high levels of TRAIL. Annexin-PI staining as well as Caspase 3 and 7 showed increased apoptosis in PC co-cultured with NK-TRAIL. Co-culture of NK-TRAIL cells did not affect the viability of the non-malignant cells (IMR-90 and hCMEC/D3) over 48h (IMR-90 + NK: 4.6%±1, IMR-90 + NK-TRAIL: 4.47±2, p=0.9; hCMEC/D3 + NK: 2.7%±0.8, hCMEC/D3 + NK-TRAIL: 2.2±0.5, p&gt;0.99). These results align with the lower expression of DR5 on non-malignant cells compared to PC cell lines (IMR-90: 1.46%±0.5, hCMEC/D3: 1.9%±0.8, LNCaP: 92.3%±4.5).

Conclusion: Transduced NK-92 MI cells with human TRAIL-induced higher levels of apoptosis of PC cell lines compared with non-transduced NK cells in co-culture experiments. The results highlight the potential of TRAIL-expressing adoptive cell therapy for CRPC. Engaging adoptive therapies with specific targets (anti-PSMA CAR) might increase the therapeutic potential of this strategy.

Citation Format: Maximilian Schwermann, Praveen Srinivasan, William MacDonald, Vida Tajiknia, Andrea Schmidt, Shengliang Zhang, Lindsey Carlsen, Andrew George, Connor Purcell, Shaolei Lu, Matthew Hadfield, Anthony Mega, Benedito Carneiro, Wafik El-Deiry. TRAIL-NK-92 MI as a novel adoptive therapy for castration-resistant prostate cancer (CRPC): Preliminary in vitro results [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3602.