ESTRO 2024 - Abstract Book

S5171

Radiobiology - Immuno-radiobiology

ESTRO 2024

1267

Digital Poster

Cytotoxicity of NK cells is facilitated by migration induction to irradiated cancer cells

Woo-Yoon Park 1,2 , Seung-Yong Lee 3 , Pankaj Kumar Chaturvedi 2 , Prabakaran Dhakshnamoorthy Subramanian 2 , Gyu Sang Yoo 2 1 Chungbuk National University, Department of Radiation Oncology, Cheongju, Korea, Republic of. 2 Chungbuk National University Hospital, Department of Radiation Oncology, Cheongju, Korea, Republic of. 3 Chungbuk National University, Department of Radiation Oncology, Cheongju, Korea, Republic of

Purpose/Objective:

Most of the recent strategies of radiotherapy and immunotherapy combination depend on T-cell responses and take some time to get the desired effect. Natural killer (NK) cells play a crucial role in regulating the innate immune system, constituting the first line of defense against pathogens or cancers. While ionizing radiation (IR) has been shown to have a significant impact on NK cell activity, the underlying mechanisms behind this effect remain still unclear. IR has been known to turn cold tumors into hot tumors and boost the immune response by augmenting the antigenicity and adjuvanticity of malignant cells by interacting with the tumor microenvironment (TME), rendering tumor cells susceptible or more tolerant to immune attack. The purpose of this study is to evaluate the modulatory effects of ionizing radiation on NK cell cytotoxicity to lung cancer cells.

Material/Methods:

The cytotoxicity of NK cells in response to ionizing radiation was tested on monolayer cultures and spheroids of three lung cancer cell lines (A549, H1650, and H1299) by The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H tetrazolium bromide (MTT) assay and Lactate dehydrogenase (LDH) assay. Three effector-target (ET) ratios (1:1, 5:1, and 10:1) and three radiation doses (2, 10, and 20 Gy) were evaluated. Further, the expression profiles of NK cell ligands on the lung cancer cells were analyzed by Reverse transcription polymerase chain reaction (RT-PCR) and western blotting. The migration of NK cells to cancer cells irradiated was assayed using transwell membrane plate.

Results:

All the 3 cell lines displayed varying susceptibility to the combination treatment of IR and NK cells. The cell viability assay indicated that 10:1 ET ratio of NK cells was highly effective in attenuating cell growth of lung cancer cells (monolayers and spheroids) irradiated with either 2 Gy or 10, up to 24 h post-IR. The LDH assay demonstrated delayed cytotoxicity in spheroids, while the adherent cells (except A549) were more sensitive to the combination treatment at an early time point of 4 h post-IR. We examined the primary transcripts of the NK cell ligands (CD112, CD155, MICA, MICB, B7H6, ULBP1, ULBP2, and ULBP3) in the lung cancer cells by RT-PCR. We observed that most of them were upregulated in the irradiated monolayer cells. In agreement with the RT-PCR results, western blots also show that B7H6, CD155, and MICB ligands were over-expressed in irradiated adherent A549 and H1299 cells, while B7H6, CD155, MICB, and ULBP1 were over-expressed in H1650 cells. Spheroids also displayed a similar trend. The number of migrated NK cells towards the conditioned medium of cancer cells was also increased IR dose-dependently.