Abstract Background: The treatment response to steroid is the most important predictive factor for treatment outcome of T-cell acute lymphoblastic leukemia (T-ALL). To improve survival for steroid-resistant T-ALL patients, it is necessary to develop innovative therapeutic strategies to overcome steroid resistance. This study attempts to determine new therapeutic strategies to overcome steroid resistance for patients with T-ALL. Tissue transglutaminase (TG2) is a intracellular calcium-dependent protein cross-linking enzyme reported to be highly expressed in various metastatic or drug-resistant cancer cells, and chronic expression of TG2 constitutively activates nuclear factor kappa B (NF-kappaB). Methods: We used biochemical and molecular methodologies to demonstrate that TG2 modulation leaded to overcome the steroid resistance in T-ALL. Results: We generated the steroid-adapted subclones of T-ALL cell lines that were extremely less sensitive to steroid than their parent T-ALL cells. We found that steroid-resistant subclones of T-ALL cells expressed much higher levels of TG2 than their parent cells and the modulation of TG2 activities altered NF-kappaB expression in this steroid-resistant cells. Inhibition of TG2 suppressed steroid resistance and improved the cytotoxicity of leukemia cells in steroid-adapted subclones of T-ALL. Conclusion: This study shows that TG2 expression is elevated with steroid resistance in T-ALL and the modulation of TG2 induces the cytotoxicity of steroid-adapted T-ALL. TG2 could be a new therapeutic target to overcome steroid resistance in T-ALL. Furthermore, change of TG2 expression could serve as markers of induced steroid resistance in T-ALL. Citation Format: Hyun Joo Jung. Tissue transglutaminase is a new therapeutic target to overcome steroid resistance in T cell acute lymphoblastic leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1134. doi:10.1158/1538-7445.AM2017-1134