BACKGROUND: Tumor-induced immunosuppression is a hallmark of tumor progression. Local immune function in the tumor vicinity plays a pivotal role in prevention of OVCA progression. Natural killer (NK) cells and cytotoxic T cells are important for anti-tumor immune function. NK cells recognize tumor cells through NKG2D receptor which binds with ligands expressed on the surface of tumor cells. Tumor cells escape NK cell by shedding NKG2D ligands from their surface. Tumors also avoid recognition by cytotoxic T cells. The mechanism of tumor-induced immunosuppression is not well understood. Glucose-regulated protein 78 (GRP78) has been suggested to increase in several malignancies. GRP78 is a marker of cellular stress and may be involved in tumor-induced immunosuppression. Understanding the mechanism of NK and T cell immunosuppression by OVCA is essential to develop effective immunotherapy.
OBJECTIVE: The goal of this study was to examine whether OVCA-induced GRP78 was associated with suppression of anti-tumor NK and T cell immunity, and whether Ashwagandha (ASH, Withania somnifera, a source of Withaferin-A and an anti-stress herbal supplement) can prevent OVCA-induced immunosuppression.
MATERIALS AND METHODS: Experiment-1: Normal postmenopausal ovaries (n=10), OVCA at early stage (papillary serous, endometrioid, mucinous and clear cell, n=5 each), and papillary serous at late stage (n=10) clinical samples were used. Tissues were examined for GRP78, NKG2D-expressing cells, CD8 T cells, ADAM10 (a cell surface expressing protease), and miRNA-180a (regulator of GRP78 expression). Experiment-2: Laying hens (4-year old) with OVCA at early stage were selected by transvaginal ultrasound imaging and divided into 2 groups, each with 20 normal and 20 OVCA. The control group received regular layer ration and the other group received diet supplemented with 2% ASH root powder for 120 days. Serum samples were collected before the start and at the time of euthanasia. Animals were sacrificed; gross morphology and tumor stages were recorded. Normal and cancerous ovaries were processed to examine the expression of OVCA markers mentioned above.
RESULTS: Stromal population of NKG2D-expressing cells and CD8 T cells were significantly higher in OVCA compared to normal ovaries (P<0.01). Significant differences were not observed in the frequency of intra-tumoral immune cells between OVCA at early and late stages. The intensity of GRP78 and ADAM10 expression by malignant cells increased significantly in association with OVCA progression (P<0.001). Increased GRP78 expression was associated with decreased expression of miRNA-180a. Ash supplementation inhibited tumor progression in 15 of 20 OVCA hens. Compared with untreated, GRP78 expression decreased significantly (P<0.001) in ASH-treated hens. The frequency of stromal and intratumoral NK and CD8 T cells increased significantly (P<0.05) in ASH-treated hens compared to control hens. ASH-treatment also increased miRNA-180a expression in hens.
CONCLUSION: OVCA progression was associated with increased GRP78 and ADAM10 expression which might be involved in decreased intra-tumoral immune cell infiltration. ASH supplementation enhanced anti-OVCA immune function by reducing tumor-associated cellular stress including GRP78 expression. Thus, ASH represents a potential GRP78-targeted anti-OVCA immunotherapy. Support: NIH/NCI R21CA187309.
Citation Format: Sa'Rah McNeal, Pincas Bitterman, Janice M Bahr, William P Hanafin, Sameer Sharma, Sanjib Basu, Animesh Barua. OVARIAN TUMOR-ASSOCIATED GRP78 INDUCES IMMUNOSUPPRESSION AND WITHAFERIN A (ASHWAGANDHA) ENHANCES ANTI-TUMOR IMMUNITY [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr NTOC-100.