NK cell line modified to express a potent, DR5 specific variant of TRAIL, show enhanced cytotoxicity in ovarian cancer models

TRAILv-KHYG-1 cells significantly reduced OVCAR-3 cell viability as compared to non-modified NK cells. However, no significant reduction in viability was observed when SKOV-3 cell were cultured with either NK cells, despite having more DR5 surface expression compared to OVCAR-3 cells. These data indicate that mechanisms other than DR5 expression drive TRAIL resistance in ovarian cancer.

KHYG-1 human NK cells were modified with a TRAIL variant targeting DR5 (TRAILv-KHYG-1). Human ovarian cancer cell lines, OVCAR-3 and SKOV-3, were cultured with modified or non-modified NK cells at different effector:target (E:T) ratios for 4 or 16 h. Apoptosis was assessed by Annexin-APC and 7-AAD and measured using flow cytometry. Apoptotic cells were defined as annexin V 7-AAD double positive. Cytokine expression was measured by multiplex ELISA, and analysed by flow cytometry.

Ovarian cancer is a lethal gynaecological malignancy with unsatisfactory 5 year survival rates of 30-50 %. Cell immunotherapy is a promising new cancer treatment where immune cells, such as Natural Killer (NK) cells, are administered to enable the patient to fight cancer through direct cytotoxicity. NK cells orchestrate an adaptive immune response by enabling the release of tumour antigens. NK cell cytotoxicity and effector responses are largely driven by TRAIL engagement. In this study we investigated the cytotoxic potential of a human NK cell line that were modified to express a potent DR5 specific TRAIL variant. We hypothesised that this modification would enhance NK cell cytotoxicity against TRAIL sensitive and resistant ovarian cancer cell lines in vitro.

Modified and non-modified NK cells significantly reduced OVCAR-3 cell viability as compared to OVCAR-3 cells that were cultured alone after 4 and 16 h treatment. OVCAR-3 cell viability was reduced after treatment with 1:1 E:T ratio with TRAILv-KHYG-1 cells after 16 h. On the contrary, neither NK cell line had any effect of SKOV-3 cell viability despite SKOV-3 cells having more DR5 surface expression compared to OVCAR-3 cells. Conclusions: TRAILv-KHYG-1 cells significantly reduced OVCAR-3 cell viability as compared to non-modified NK cells. However, no significant reduction in viability was observed when SKOV-3 cell were cultured with either NK cells, despite having more DR5 surface expression compared to OVCAR-3 cells. These data indicate that mechanisms other than DR5 expression drive TRAIL resistance in ovarian cancer.