The Effect of T-Bet Overexpression on Immune Factors In Vitro

Friday, February 17, 2017
Exhibit Hall (Hynes Convention Center)
Mahima Reddy, University of Pittsburgh Cancer Institute, Pittsburgh, PA
T-box transcription factor Tbx21 (T-bet) serves as a master regulator of T helper 1 cell commitment in CD4+ T cells and NK cells and acts as a major transcriptional controller of CD8+ T cell cytotoxic IFNγ and the cell surface chemokine receptor CXCR3. Past studies have shown anti-tumor efficacy after the direct injection of dendritic cells (DC) engineered to overexpress T-bet (DC.Tbet), but not control DC, into established tumors in mice. As a consequence of DC.Tbet-based therapy, different immune factors are upregulated in the therapeutic tumor microenvironment (TME). However, it remains unclear which cells within the TME are responsible for producing and responding to these factors. Hence, the current study was designed to determine if the largest cellular component of the TME–the malignant cells–were capable of being modulated to mimic the immune profiles of the therapeutic TME after being engineered to express T-bet in vitro. RT-PCR and Western blotting were used to quantify the transcription and protein levels, respectively, of IL-36R agonists, lymphotoxins, and chemokines (soluble factors that recruit immune cells into tissues) in MC38 colon carcinoma and MCA205 fibrosarcoma cells after infection with an optimal dose (MOI = 100) of recombinant adenovirus encoding murine T-bet. Experimental duplicates were analyzed 4, 18 and 48 hours after infection. Except for a nominal effect seen in the lymphotoxin series (specifically with the immune factor LTßR), immune factors associated with the therapeutic TME were not modulated as a consequence of ectopic T-bet expression in the mouse tumor cell lines. Future work will attempt to understand the intricacy of tumor immunomodulation by analyzing the role of other tumor components, such as stromal (fibroblasts, monocytes) and vascular cells in the in situ (TME) response to DC.Tbet-based therapy.