TGF-β Reporter HEK 293 Cells

Cell line description

HEK-Blue™ TGF-β cells were generated by stable transfection of the human embryonic kidney HEK293 cell line with a Smad-inducible secreted embryonic alkaline phosphatase (SEAP) reporter. The binding of TGF-β to its receptor triggers a signaling cascade leading to the formation of a Smad2/Smad3/Smad4 complex. The heterocomplex enters the nucleus and binds SBE (Smad binding elements) sites in the engineered minimal promoter, thereby inducing the production of SEAP. This can be readily assessed in the supernatant using QUANTI-Blue™ Solution, a SEAP detection reagent.

HEK-Blue™ TGF-β cells detect human (h) and mouse (m) TGF-β. Of note, they detect all three isoforms of hTGF-β: hTGF-β1, hTGF-β2, and hTGF-β3 (see figures). 

TGF-β background

Tumor growth factor-beta (TGF-β) belongs to a family of structurally related cytokines that regulate a plethora of cellular functions, such as proliferation, apoptosis, differentiation, and migration [1,2]. TGF-β exists in at least three isoforms; TGF-β1, TGF-β2, and TGF-β3. In the immune system, TGF-β1 is the predominant isoform [1]. It is produced by many cell types, including macrophages, in a latent form that is bound to two other polypeptides, latent TGF-β1 binding protein (LTBP) and latency-associated peptide (LAP). Upon cleavage of these proproteins, the mature TGF-β1 is released. This mature protein can bind its cell surface receptors and initiate signaling.

TGF-β binds to type II receptors (TβR-II) which recruit and activate type I receptors (TβR-I). The active ligand-heterotetrameric receptor complex signals through downstream transcriptional factors named Smads, including Smad2, Smad3, and Smad4.
Smad complexes translocate into the nucleus where they regulate the transcription of target genes, which contain one or more Smad binding elements (SBEs) in their promoter region [3]. Perturbations in TGF-β signaling affect immune homeostasis and tolerance, leading to inflammatory diseases and tumor immune evasion [3].

1.  Travis MA. & Sheppard D., 2014. TGF-β activation and function in immunity. Annu Rev Immunol. 32:51-82.
2. Taylor AW., 2009. Review of the activation of TGF-beta in immunity. J Leukoc Biol. 85(1):29-33.
3. Battle E. & Massagué J., 2019. Transforming Growth Factor-beta Signaling in Immunity and Cancer. Immunity. 50(4):924.