Abstract 531: Human γδ T cells limit breast tumor growth partly by down regulating cell survival-related molecules and up regulating apoptosis-related molecules in tumor cells
Authors: Aggarwal Reeva , Lu Jingwei , Kanji Suman , Das Manjusri , Joseph Matthew , Lustberg Maryam B. , Pompili Vincent , Shapiro Charles L. , Das Hiranmoy 
Published: August 2012

Background: Innate immune system has been known to play an important role in inhibiting the malignant transformation, tumor progression and invasion. However, the mechanistic basis remains ambiguous. Despite polyclonality of human γδ T cells, Vγ2Vα2 T cell subset, major subset of peripheral γδ T cells, uniformly recognize non-peptide antigens and provide the first line of defense towards many microbial infections. This γδ T cell subset was also shown to recognize and limit the growth of the various tumors such as myeloma, lymphoma, pancreatic tumors and ovarian tumors. The differential recognition of the tumor cells by the Vγ2Vα2 T cells depends on the expression levels of certain surface molecules on the tumor cells. Methods: To determine innate immune response of γδ T cells towards breast tumor cells, human peripheral γδ T cells were isolated and expanded in vitro using aminobisphosphonate, risedronate and co-cultured with breast tumor cells to assess tumor cell viability and proliferation using MTT assays and to determine the alteration in molecular levels in tumor cells using western blots. Cell morphology was recorded under microscope and flowcytometric analysis was performed to evaluate tumor surface molecules. Xenograft of the human breast tumor cells and human γδ T cells were performed in immunocompromised NOD/SCID mice. Immunohistochemistry was performed to evaluate status of the tumor tissue morphology, angiogenesis and apoptosis. Western blot was also performed to evaluate key signaling molecules. Results: Breast cancer cell death was associated with the surface expression levels of MICA/B and ICAM-1. Molecular signaling analysis demonstrated that cell survivability or immune escape from γδ T cells was associated with the higher expression levels of cell survival-related molecules such as Akt, Erk1/2 and Bcl2 and concomitant down regulation of apoptosis-related molecules, PARP and cleaved Caspase 3, and down regulation of tumor suppressor genes, PTEN and P53. However, opposite molecular signaling was observed in susceptible cell lines after co-culture with γδ T cells. In vivo, anti-neoplastic effects of γδ T cells were also documented, where tumor growth was inhibited due to the disruption of microvasculature, induction of tumor suppressor genes p53, downregulation of survival signals, and a strong induction of apoptotic molecules. Conclusions: Our current study reveals that γδ T cells limit the in vitro growth of breast cancer cell lines as SKBR7 (HER2+), T47D (ER+) and MDA-MB-231 (ER-) by inhibiting their survival and inducing apoptosis, except BR-CA-MZ01 (PR+) cells. In vivo xenograft also confirms the anti-neoplastic effect of γδ T cells towards breast tumor cells. These findings reveal that complex molecular signaling mechanisms are involved in γδ T cell-mediated anti-neoplastic effects other than cytotoxicity.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 531. doi:1538-7445.AM2012-531