Pseudonormal morphology of adenoid cystic carcinoma cells subverts the antitumor reactivity of immune cells

Objectives: Adenoid cystic carcinoma (ACC) is a rare salivary gland cancer most frequently arising in the head and neck region. The ACC microenvironment exhibits low immunogenicity (low tumor infiltrating lymphocytes and dendritic cells). This scenario favours immune evasion and partially explains poor prognosis because of the activation of immune inhibitory proteins. Gipie is a hook-related protein, that is involved in protein trafficking. Gipie (HkRP3, encoded by CCDC88B) is associated with T cell maturation and inflammatory functions and target cell killing in natural killer (NK) cells. Gipie is present in ACC patient samples and cells. Therefore, we investigated proliferation, apoptosis, and morphologic changes caused by Gipie in oral and salivary gland cancer cells in presence of immune cells. Methods: We assayed UM-HACC-2A (adenoid cystic carcinoma), A-253 (mucoepidermoid carcinoma, MEC), SCC4, SCC9, SCC25, CAL27 (oral squamous cell carcinoma, OSCC), OKF6 (normal oral) cells cocultured with, NK-92 (natural killer), and Jurkat, Clone E6-1 (acute T cell leukemia) cells, to construct multiple salivary gland and oral cancer-immune cell co-culture models. Gipie silenced cancer cells (silencing maintained for 48 hours) in the cancer immune coculture models were compared with their unaltered subsets. Cancer-immune cells interactions were maintained for 16 hours. Overall three hundred thirty-six (336) co-culture models were used to determine apoptosis, immune activation, morphology, transmigration, and protein expression. Additionally, we performed targeted mass spectrometry analysis to identify changes in protein profiles. Results: ACC cells exhibited Pseudonormal morphology after interacting with immune cells in the 3D coculture model. Gipie-silenced ACC cells in coculture model transformed to “lymphoblast-like” morphology. Gipie-silenced ACC cells in co-culture model (n = 24) showed significant increase of apoptotic cells compared to unaltered ACC cells, lowering of T regulatory cells (FoxP3⁺/IL-2Rα+/CD25⁺) (n = 24), and increase of activated NK cells (NKp30⁺/IFN-γ⁺) (n = 24) with significantly higher release of granzyme (n = 12) and perforin (n = 12). Increased activation of immune cells (transmigration and fluorescence intensity) via 3D-z-stack images were observed in Gipie-silenced subsets (n = 24). MEC cells responses were significantly less compared to ACC in co-culture models followed by silencing of Gipie, while OSCC and OKF6 cell responses were negligible, under identical conditions. Conclusions: The presence of Gipie confers pseudonormal morphology to ACC cells thereby reducing immune attack. Thus, trafficking proteins may impact ACC cancer-immune cell interaction during conventional chemotherapy or monoclonal immunotherapy.