Abstract 2520: Ovarian tumors escape anti-tumor function of NK cells by inducing CISH expression and its inhibition prevents tumor progression
Authors: Acosta Jasmin C. , Stasik Amy K. , Bahr Janice M. , Barua Animesh 
Published: June 2022

Background: Ovarian cancer (OVCA), a lethal malignancy of women, mainly disseminates locally in the peritoneal cavity and the local immune system plays important roles in inhibiting its progression. Although NK cells, a member of innate immunity, recognize and exert anti-tumor immune responses, tumors escape NK cell immunity and progress to late stages by inducing factors like inhibitory receptors and cytokines. IL-15, a cytokine, stimulates NK cell function and persistent exposure to IL-15 induces cytokine inducible SH2-containing protein (CISH), an inhibitory receptor and a marker of NK cell exhaustion. It is unknown if ovarian tumors use this phenomenon in their favor as the tumor secretes enhanced levels of IL-15. Furthermore, dietary supplementation with root powder of Ashwagandha (ASH), a natural herb and an anti-stress compound has shown to decrease the rates of OVCA metastasis and enhance the frequency of intratumoral NK cells in a preclinical model. However, it is unknown if ASH supplementation improves NK cell frequency by inhibiting CISH. The goal of this study was to examine if OVCA progresses by inducing CISH-expression in NK cells and if dietary ASH supplementation reduces NK cell exhaustion by decreasing CISH expression.

Materials and methods: Two studies were conducted. Study 1: Exploratory study with clinical specimens including normal ovaries (n=5) and ovarian high grade serous carcinoma at early and late stages (n=5 each). Study 2: Prospective study using the laying hen model of OVCA supplemented with or without 2% dietary ASH root powder for 90 days (n=7 for each group; normal, early and late stage). Hen normal and tumor ovarian tissues were collected at the end of the study. Both the clinical and hen specimens were used for immunohistochemistry, Western blotting and gene expression assays to determine the frequency of CISH-expressing NK-cells and intensity of GRP78 expression (a marker of cellular stress). Data were collected and analyzed by ANOVA and unpaired t-test and considered significant when P&lt;0.05.

Results: CISH-expressing NK cells were localized in normal and tumor ovaries in women and hens. Compared with normal ovaries, frequency of CISH-expressing NK cells was significantly higher in tumors at early and late stages in patients and hens. Similarly, strong expression of CISH gene and protein (29kDa) was detected in tumor tissues. Enhanced expression of CISH positively correlated with expression of GRP78. Compared with untreated, ASH supplementation reduced tumor progression in 5 out of 7 hens and significantly decreased the frequency of CISH-expressing NK cells and GRP78 (P&lt;0.001).

Conclusion: The results of this study suggest that expression of CISH by NK cells and cellular stress were associated with OVCA progression and dietary ASH supplementation reduced NK cell exhaustion by decreasing CISH and GRP78. Support: Swim Across America and NIH CA187309

Citation Format: Jasmin C. Acosta, Amy K. Stasik, Janice M. Bahr, Animesh Barua. Ovarian tumors escape anti-tumor function of NK cells by inducing CISH expression and its inhibition prevents tumor progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2520.